U.S. patent number RE37,360 [Application Number 07/837,588] was granted by the patent office on 2001-09-11 for electronic motor controls, laundry machines including such controls and/or methods of operating such controls.
This patent grant is currently assigned to Fisher & Paykel. Invention is credited to Gerald D. Duncan.
United States Patent |
RE37,360 |
Duncan |
September 11, 2001 |
Electronic motor controls, laundry machines including such controls
and/or methods of operating such controls
Abstract
A control apparatus and method for an electric motor having
sensing devices which sense the frequency and polarity of EMFs in
the rotor windings down to a condition where the rotor is in
condition for reversing, and causing reversing of the motor when
the frequency is such as to allow reversing and the .[.polarits.].
.Iadd.polarity .Iaddend.of a selected winding is at or near a zero
crossing between positive and negative polarities. Cyclical
reversal is effected by measuring the time the rotor takes to coast
from a "power off" condition to the condition for reversing and
with an electronically commutated motor reversing can usually be
effected in one commutation period. The motor is used in a clothes
washing machine or similar application where rapid reversal is
required or timing of the time from one reversal to the next is
required to be constant.
Inventors: |
Duncan; Gerald D. (Mt Eden,
NZ) |
Assignee: |
Fisher & Paykel (Auckland,
NZ)
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Family
ID: |
27484287 |
Appl.
No.: |
07/837,588 |
Filed: |
February 18, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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526711 |
May 17, 1990 |
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Reissue of: |
908176 |
Sep 16, 1986 |
04857814 |
Aug 15, 1989 |
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Foreign Application Priority Data
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Sep 16, 1985 [NZ] |
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213489 |
Sep 16, 1985 [NZ] |
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213490 |
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Current U.S.
Class: |
318/281;
318/443 |
Current CPC
Class: |
H02P
23/24 (20160201); D06F 34/08 (20200201); H02P
6/30 (20160201); D06F 34/10 (20200201) |
Current International
Class: |
D06F
37/30 (20060101); H02P 23/00 (20060101); H02P
6/00 (20060101); H02P 001/22 (); H02P 003/12 () |
Field of
Search: |
;318/138,254,280,281,282,283,284,286,379,380,430,439,443,444,445 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ro; Bentsu
Attorney, Agent or Firm: Christie, Parker & Hale,
LLP
Parent Case Text
.Iadd.CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of Ser. No. 07/526,711, filed
May 17, 1990, now abandoned; which is a reissue application of Ser.
No. 06/908,176, filed Sep. 16, 1986, now U.S. Pat. No.
4,857,814..Iaddend.
Claims
What we claim is:
1. A method of cyclically reversing an electronically commutated
motor having a plurality of windings on a stator and a rotor having
magnetic poles rotatable relative to said stator and using
electronic control apparatus and means to indicate the position of
the rotor, said method comprising the steps of
(a) initiating and then continuing a correct sequence of the
commutations selected from a desired time of and desired number of
the commutations,
(b) removing all the power from the windings and allowing the rotor
to coast towards zero speed of rotation,
(c) testing and establishing a position of the rotor relative to
the stator at least during a later part of the coasting of the
rotor, and
(d) when the rotor has slowed to a condition in which application
of reversed commutation will cause reversal of rotation but is
still rotating (condition for reversing) and its position relative
to the stator is established, and without delay after the condition
for reversing, applying power to the stator windings and effecting
entry into said correct sequence of the commutations of power to
the winding, the position of entry into said correct sequence being
determined by the direction of rotation of the rotor before
stopping and the position of the rotor relative to the stator to
cause the rotor to change direction the correct sequence of
commutations follows automatically to maintain rotor rotation in
the changed direction, and repeating steps (b) to (d) to give
cyclical reversal for a desired time.
2. A method as claimed in claim 1 which includes the steps of
indicating the direction and sequence of back EMFs in said windings
after power has been removed therefrom and at least as the rotor
nears a position where it is in the checking voltage transition
points between positive and negative in at least one of said
windings caused by the back EMFs in said at least one of said
windings and the step of applying power and effecting entry
comprises the step of entering the sequence of the commutations to
cause reversal about a time when such a voltage transition point
occurs in a selected winding.
3. A method as claimed in claim 1 or claim 2 wherein the step of
testing and establishing includes the steps of testing back EMF
from at least one of the windings for polarity and frequency, and
wherein the step of applying power and effecting entry comprises
the step of entering the sequence of the commutations when the
frequency of the back EMF has fallen to a value such that the rotor
has slowed to the condition for reversing and polarity is
substantially at a zero crossing between opposite polarities in a
selected winding.
4. A method as claimed in claim 3 in which the step of testing and
establishing includes the step of testing all the windings to
indicate the position of the rotor.
5. A method as claimed in claim 1 wherein the change in the
sequence of the commutation usually occurs within a single
commutation to cause a change in direction of rotation of the
rotor.
6. A method for driving an electronically commutated motor
cyclically in opposite directions during each of a sequence of half
cycles, each half cycle comprising the steps of
applying electrical power driving the motor in a reverse direction
from the prior cycle causing acceleration of the motor towards a
desired speed, switching power off to the motor and reducing the
speed of the motor to a condition where applying power in the next
half cycle will reverse the direction of motor rotation,
determining resistance to rotation of the motor, and
adjusting the power applied to the motor in the step of applying
power so as to cause acceleration of the motor in accordance with
the resistance to motor rotation determined during the prior half
cycle.
7. Control apparatus for applying power to an electronically
commutated motor having a plurality of windings on a stator adapted
to be selectively commutated and a rotor having magnetic poles
rotatable relative to said stator, said control apparatus
comprising:
(a) timing means to time the period of one of the rotation and
counting means to count the number of rotations of the rotor in a
desired direction,
(b) commutation switching means to disconnect the power from said
windings to allow the rotor to coast towards zero speed of
rotation,
(c) detecting means to indicate rotor position relative to said
stator at least during a later part of the coasting of the rotor
before the rotor comes to rest, and
(d) pattern reverse means operable, in response to a signal from
said detecting means when the rotor has slowed to a condition in
which application of reversing commutations will cause reversal of
rotation but is still rotating (condition to be reversed) and
without delay after the condition to be reversed, for applying
power to the stator windings and effecting entry into a correct
sequence of the commutations of power to the winding, the position
of entry into said correct sequence being determined by the
direction of rotation of the rotor before stopping and the position
of the rotor relative to the stator and thereby cause said rotor to
change direction without testing for rotor direction.
8. Control apparatus as claimed in claim 7 wherein said detecting
means detects the direction and sequence of back EMFs in at least
one of said windings after the power has been removed therefrom and
.[.detectts.]. .Iadd.detects .Iaddend.voltage transition points
between positive and negative polarity in at least one of the
windings and said pattern reverse means is actuated to reverse the
sequence of the commutations about the time when a voltage
transition point occurs in at least one of the windings.
9. Control apparatus as claimed in claim 7 or claim 8 wherein said
control apparatus further comprises:
(e) a commutating circuit responsive to control signals to cause
electrical power from a power source to be applied commutatively to
said windings to cause said rotor to rotate in a desired
direction,
(f) testing means responsive to any back EMF generated in at least
one unpowered winding to test the polarity and frequency of any
back EMF generated in that unpowered winding,
(g) the pattern .[.reversing.]. .Iadd.reverse .Iaddend.means
comprising commutation reversing means to cause the commutation to
reverse to give the correct sequence of commutation to rotate the
rotor in the desired direction, and
(h) commutation reversing actuating means to reverse the
commutation when said frequency is at a value such that the motor
is in the condition to be reversed and the polarity in a selected
winding is substantially at a zero crossing between opposite
polarities.
10. Electrical control means for cyclically controlling the supply
of electrical power to an electric motor having a rotor.Iadd.,
.Iaddend.said control means comprising switching means to switch
power on and off to said motor, .[.power on timing means to time
the length of power on time when power is switched on,.]. coasting
timing means to time the length of coasting time said rotor takes
from the time power is switched off thereto to the time when said
rotor has slowed to a condition in which the rotor rotation may be
reversed (condition for reversing), the control means controlling
the amount of power applied to the motor in accordance with the
coast time.Iadd., .Iaddend.and reversing means to reverse the
direction of said rotor when said rotor is in the condition for
reversing and to switch power by said switching means when
reversing is to be effected.
11. Electrical control means as claimed in claim 10 .Iadd.further
comprising power on timing means to time the length of power on
time when power is switched on, .Iaddend.wherein a stroke time
during which said rotor rotates in one direction between reversals
is the sum of said power on time and said coasting time.
12. A method of cyclically controlling power to an electrical motor
having a rotor, said method including the steps of starting
rotation of said rotor in one direction, setting an initial power
on time and applying power to said motor during said power on time,
switching off power at the end of said initial power on time,
allowing the rotor to slow until the rotor has slowed to a
condition in which application of power will cause reversal of
rotation (condition to be reversed), checking a ramp down time
after power is switched off within which the rotor slows to the
condition to be reversed, causing reversal of direction of rotation
of said rotor, as soon as the rotor is in the condition to be
reversed, and repeating the preceding steps, using the ramp down
time to adjust the amount of power applied to the motor while
repeating the steps.
13. A method of cyclically controlling the supply of power to an
electric motor having a rotor.Iadd., .Iaddend.said method including
the steps of
setting a desired time of rotation of said rotor in one
direction,
starting rotation of said rotor in said one direction,
setting an initial power on time and applying power to said motor
during said initial power on time,
switching off the power to the motor at the end of said initial
power on time, allowing the rotor to slow to a condition in which
application of power to the motor will cause reversal of rotation
but is still rotating (condition for reversal),
checking a ramp down time within which the rotor takes to slow to
the condition for reversal,
causing reversal of direction of rotation of said rotor by applying
power to the motor, substantially at said condition for reversal,
for a further power on time which is such that said further power
on time plus said ramp down time (half cycle time) equals said
desired time,
switching off power to said motor at the end of said further power
on time, again checking the next said ramp down time within which
the rotor takes to slow the condition for another reversal,
again reversing direction of the rotor when said rotor is in the
condition for reversal and applying power to said motor for a still
further power on time which is such that said still further power
on time plus said next down ramp time (half cycle time) equals said
desired time and repeating the steps, starting with the step of
causing reversal of direction, for a desired length of time,
adjusting the power on time during at least one said half cycle
time in accordance with a previous ramp down time at desired
intervals of time so that the adjusted power on time for the at
least one said half cycle time plus the ramp down time for the
previous half cycle time equals said desired time.
14. A method of electronically cyclically controlling the supply of
power to an electric motor using sensing means and actuate
adjustment means for adjusting the power to the motor, said method
including the steps of setting a desired speed of rotation of the
motor, sensing the resistance to rotation of the motor; using
responses from the sensing means for controlling the adjustment
means to adjust the power supplied to the motor to change the motor
speed towards said desired speed and then operate the motor within
a range of speeds substantially at said desired speed of rotation,
switching off the supply of power to the motor following which the
motor slows to a stop and applying power to the motor and repeating
the recited steps at least once, starting with the step of
controlling to thereby cause a change in the adjusted power
supplied to the motor in accordance with the sensed resistance to
rotation of the rotor that occurred prior to the stop of the motor,
with the motor running in the reverse direction.
15. A method as claimed in claim 14 which includes the step of
sensing resistance to rotation by measuring the time the motor
takes to run down from a power off condition to a condition in
which application of power to the motor will cause reversal of
rotation (condition to be reversed).
16. A method as claimed in claim 14 or claim 15 .[.which
includes.]. .Iadd.wherein .Iaddend.the step of controlling
initially causes acceleration of the motor to just below the
desired speed and, after stopping of the motor, causes acceleration
of the motor at least substantially up to the desired speed.
17. A method as claimed in claim 14 or claim 15 wherein the step of
using .[.responsive.]. .Iadd.responses .Iaddend.for controlling
causes the motor, after stopping, to accelerate to a speed just
above the desired speed and thereby overshoot the desired speed and
then fall to the desired speed.
18. A method as claimed in claim 15 wherein the step of using
.[.responsive.]. .Iadd.responses .Iaddend.for controlling causes
the motor speed, after stopping, to overshoot or undershoot in
relation to a desired plateau level of the desired speed to give a
desired vigorousness of motion to the motor.
19. A method as claimed in any one of claims 12 to 15, wherein the
motor has windings on a stator driving a rotor, which method
includes the steps of
(a) continuing motor rotation for a desired time, or angle .[.or.].
.Iadd.of .Iaddend.rotation,
(b) removing all power from the windings and allowing the rotor to
coast towards a condition to be reversed,
(c) testing the position of the rotor relative to the stator during
the coasting towards the condition to be reversed, and
(d) when the rotor is in a condition such that application of power
to the windings will cause reversal of rotation (condition to be
reversed) and its position relative to the stator is known,
applying a changed sequence of commutations to the windings to
cause the rotor to change direction, the correct commutations
following automatically to maintain rotor rotation in the changed
direction, and repeating the steps to give cyclical reversal for a
desired time.
20. A method as claimed in claim 19, which includes the steps of
following the direction and sequence of back EMFs in said windings
after power has been removed therefrom and at least as the rotor
nears a position where it is in the condition to be reversed.Iadd.,
.Iaddend.checking the voltage transitions points between positive
and negative for at least one of said windings and changing the
sequence of commutations to the windings to cause reversal about
the time when a voltage transition point occurs in at least one
.Iadd.said .Iaddend.winding.
21. A method as claimed in claim 20 which includes the steps of
testing the back EMFs from at least one said winding for polarity
and frequency and changing the sequence of commutation when the
frequency has fallen to a value such that the rotor is in the
condition to be reversed and the polarity is at or near a zero
crossing between opposite polarities in at least one said
winding.
22. A method as claimed in claim 21 which includes the step of
testing all the windings to indicate the position of the rotor.
23. A method as claimed in claim 22 comprising the step of enabling
said changed sequence of commutations to occur within a single
commutation change to cause a change in direction of rotation of
the rotor.
24. An electrical control means for cyclically controlling the
supply of electrical power to an electric motor having a rotor,
said control means comprising
switching means to switch power to said motor on and off,
power timing means to control the length of time when power is
switched for a selected power on time,
coasting timing means to time the length of the coast time said
rotor takes from the time power is switched off thereto to the time
when said rotor is in condition for reversal of direction of
rotation,
stroke time setting means to set, to a desired value, the stroke
time during which said rotor rotates in one direction between
reversals,
algebraic subtracting means to algebraically subtract a previous
coast time from said stroke time to arrive at a time setting for
said selected power on time,
reversing means to reverse the direction of said rotor when said
rotor is in condition for reversal.
25. An electrical control means for cyclically controlling the
supply of electrical power to an electrical motor having a
rotor.Iadd., .Iaddend.said control means comprising:
switching means to switch power to said motor on and off, coasting
timing means to time the length of time said rotor takes from the
time power is switched off thereto to the time when said rotor has
slowed to a condition in which the rotor direction may be reversed
(condition for reversing), reversing means to reverse the direction
of said rotor when said rotor is in the condition for reversing and
to switch on said switching means when reversing is to be
effected.Iadd., .Iaddend.and means for controlling the supply of
power to said motor in accordance with a desired length of time of
coasting to the condition for reversing.
26. An electrical control means for cyclically controlling the
supply of electrical power to an electric motor having a rotor,
said electrical control means including setting means operable to
set a desired speed of rotation of the rotor of said motor, sensing
means to sense resistance to rotation of the rotor prior to a
reversal in direction of running of the rotor, adjustment means
responsive to the resistance to rotation speed prior to a preceding
reversal of running of the rotor for adjusting the power supplied
to the motor to accelerate said rotor towards the desired speed and
to maintain the rotor speed within a range of speeds substantially
at said desired speed of rotation, switching means to switch off
the supply of power to said motor after a desired time and
reversing means, operable when said rotor has slowed to a condition
in which the rotation direction may be reversed (condition for
reversing), to reenable the preceding recited means with the rotor
running in the reverse direction.
27. Electrical control means as claimed in claim 26 wherein said
sensing means comprises timing means to measure the time the rotor
takes to run down from a .[.powr.]. .Iadd.power .Iaddend.off
condition to the condition for reversing.
28. Electrical control means as claimed in claim 26 wherein the
motor has a .[.rotor.]. .Iadd.stator .Iaddend.including windings;
said electrical control means .[.includes.].
.Iadd.including.Iaddend.:
.[.(e).]. a commutating circuit responsive to control signals to
cause electrical power from a power source to be applied
commutatively to said windings and to cause said rotor to rotate in
a desired direction,
.[.(f).]. testing means responsive to any back EMF generated in at
least one unpowered winding to test the frequency and polarity of
the back EMF generated in that unpowered winding,
.[.(g).]. the reversing means comprising commutation reversing
means to reverse commutation of the commutatively applied electric
power to give a correct sequence of commutation to rotate the rotor
in the desired direction when the condition for reversing exists
and a selected winding has a signal therein substantially at a zero
crossing between opposite polarities.
29. Electrical control means as claimed in claim 26 or claim 27
wherein the motor has a stator including windings to drive the
rotor; said electrical control means including means for providing
commutation signals to the windings, and said reversing means
comprising
(a) counting means to count one of the time of the period of
rotation and the number of rotations of the rotor in a desired
direction,
(b) .[.communication.]. .Iadd.commutation .Iaddend.switching means
to disconnect the power from said windings,
(c) detecting means to indicate rotor position relative to said
stator, and
(d) pattern reverse means operable by a signal from said detecting
means to cause commutation signal changes to the windings which
cause said rotor to change direction without testing for rotor
rotational direction.
30. Electrical control means as claimed in any one of claims 25 to
27 wherein the motor has windings, and comprising braking means to
brake the rotor, the braking means comprising switching means,
having an impedance, to connect an end of at least one winding to
an end of at least one other winding to provide a closed circuit
through said impedance and the interconnected windings through
which braking currents pass, the other ends of the interconnected
windings being connected together, and comparator means
interconnected to compare voltages between opposite ends of the
windings to enable the speed of the rotor during braking to be
indicated.
31. Electrical control means as claimed in any one of claims 25 to
27 wherein the motor has a stator including windings; said
electrical control means further comprising braking means for
braking the rotor, the braking means comprising swiching means,
having an impedance, to connect one end of one winding to one end
of another of said windings through said impedance, the other end
of said windings being connected together, comparator means for
comparing the voltages between opposite ends of the windings to
enable the speed of the rotor during braking to be established.
32. A method of cyclically reversing an electronically commutated
motor having a plurality of windings on a stator and a rotor having
magnetic poles rotatable relative to said stator, said method
comprising the steps of
(a) removing substantially all the power from the windings and,
while the rotor is rotating, allowing the rotor to coast towards
zero speed of rotation, and
(b) when the rotor has slowed to a condition in which application
of a reversed commutation will cause reversal of rotation at any
time between a still rotating condition of the rotor and
substantially the time the rotor has stopped rotation (condition
for reversing) and without delay, applying power to the stator
windings and effecting entry at the correct sequence of
commutations of power to the windings to cause the rotor to change
direction and to maintain rotor rotation in the changed
direction.
33. The method of claim 32 comprising the step of repeating the
recited steps to provide cylical reversals for desired time
intervals.
34. The method of claim 33 comprising the steps of
testing and determining the position of the rotor relative to the
stator at a later part of the coasting of the rotor before reaching
zero speed of rotation, the step of effecting entry into the
correct sequence of commutations being .[.condition.].
.Iadd.conditioned .Iaddend.upon the determined position in the
preceding step. .Iadd.
35. A method of cyclically controlling the supply of power to an
electric motor having a rotor, a stator and windings, which method
comprises:
(a) setting a desired time of rotation of said rotor in one
direction,
(b) starting rotation of said rotor in said one direction, setting
an initial "power on" time during which power is applied to said
motor, switching off power at the end of said initial "power on"
time, causing the rotor to slow to a condition for reversing while
the rotor is still rotating (condition for reversal),
(c) checking a ramp down time which said rotor takes to slow to
said condition for reversal,
(d) causing reversal of direction of rotation of said rotor,
(e) applying power to said motor for a further "power on" time
which is such that said further "power on" time plus said ramp down
time (half cycle) equals said desired time,
(f) switching off power to said motor at the end of said further
"power on" time,
(g) checking the next ramp down time and reversing direction of the
rotor to said one direction when said rotor is in said condition
for reversal,
(h) applying power to said motor for a still further "power on"
time which is such that said further "power on" time plus said next
ramp down time substantially equals said desired time, and
(i) selectively repeating selected ones of the preceding steps for
a desired length of time, adjusting the "power on" time at desired
intervals of time so that the adjusted "power on" time for a
further half cycle plus the ramp down time for a previous half
cycle substantially equals said desired time. .Iaddend..Iadd.
36. The method of claim 35 wherein the condition for reversal is
one wherein a reversal in commutation of power to the windings will
cause a reversal of rotation of the rotor. .Iaddend..Iadd.
37. A method according to claim 35, including the steps of:
(a) setting a desired speed of rotor rotation,
(b) setting a forward cycle comprising
(i) applying power to said motor at an initial rate for a
predetermined period to accelerate the rotor,
(ii) determining the speed attained at the end of the period of
acceleration, which speed depends on the resistance to rotation of
the rotor, and
(iii) switching off the power supply to the motor,
(c) setting a reverse cycle comprising repeating the forward cycle
steps, but with the rotor running in the reverse direction and with
the power adjusted in accordance with the previously determined
speed to adjust the acceleration rate and thereby change the rotor
speed so that it approaches a desired speed, and
(d) selectively repeating the forward and reverse cycles.
.Iaddend..Iadd.
38. A method according to claim 35 or 37, which includes the
further step of sensing rotor resistance to rotation by measuring
the time the rotor takes to run down from a power off condition
when power is switched off to the condition for reversal.
.Iaddend..Iadd.
39. A method according to claim 37 comprising the steps of
effecting such acceleration to cause the rotor to rotate initially
just below a desired speed and adjusting the supply of power to the
motor so that the rotor speed rises to said desired speed.
.Iaddend..Iadd.
40. A method according to claim 37 further comprising the steps of
effecting such acceleration to cause the rotor to accelerate to a
speed just above a desired speed and adjusting the power supplied
to the motor so that the speed falls to the desired speed.
.Iaddend..Iadd.
41. A method according to claim 35 or 37 further comprising the
steps of adjusting a level of one of overshoot and undershoot in
speed of the rotor in relation to a desired plateau level of
constant speed to give a desired vigorousness of motion to the
rotor. .Iaddend..Iadd.
42. A method according to claim 35 or 37 comprising
initiating and then continuing a correct sequence of commutations
of power to the windings selected from a desired time of and a
desired number of commutations,
a reversing cycle comprising removing all the power from the
windings and allowing the rotor to coast towards zero speed of
rotation,
testing and establishing the position of the rotor relative to the
stator at least during a latter part of the coasting of the rotor,
and
when the rotor has slowed to a condition in which application of
reversed commutation will cause reversal of rotation but is still
rotating and the position of the rotor relative to the stator is
known, without delay applying power to the windings effecting entry
into the correct sequence of commutations, the position of entry
into the correct sequence being determined by the direction of
rotation of the rotor before stopping and the position of the rotor
relative to the stator, to cause the rotor to change direction, the
correct sequence of commutations following automatically to
maintain rotor rotation in the changed direction, and
selectively repeating the reversing steps to achieve cyclical
reversal for a desired time. .Iaddend..Iadd.
43. A method according to claim 42 comprising following the
direction and sequence of EMFs in said windings after power has
been removed therefrom and, at least as the rotor approaches a
position where it is in condition for reversal, checking the
voltage transition points between positive and negative for at
least one winding and changing the sequence of commutations to
cause reversal substantially at the time when a voltage transition
point occurs in a selected winding. .Iaddend..Iadd.
44. A method according to claim 43 further comprising testing the
EMFs from at least one winding for polarity and frequency and
changing the sequence of commutations when the frequency has fallen
to a value such that the rotor is in condition for reversal and the
polarity is substantially at a zero crossing between opposite
polarities. .Iaddend..Iadd.
45. A method according to claim 44 wherein the step of testing
comprises testing all the windings to indicate the position of the
rotor. .Iaddend..Iadd.
46. A method according to claim 42 further comprising a step of
enabling the sequence of commutations to occur within a single
commutation change to cause a change in direction of rotation of
the rotor. .Iaddend..Iadd.
47. A method according to claim 42 wherein the motor is an
electronically commutated motor. .Iaddend..Iadd.
48. A method according to claim 35 or 36 wherein the desired time
is variable. .Iaddend..Iadd.
49. A method of electronically cyclically controlling the supply of
power to an electric motor, having a rotor, which method comprises
the steps of
(a) a forward cycle comprising
(i) setting a desired speed of rotation for the rotor,
(ii) applying power to said motor at an initial rate for a
predetermined period to accelerate the rotor, and
(iii) determining the speed attained at the end of the
predetermined period of acceleration, which speed depends on the
resistance to rotation of the rotor, and switching off the power
supply to the motor, and
(b) a reverse cycle comprising repeating the forward cycle steps,
but with the rotor running in the reverse direction and with the
power adjusted in accordance with the previously determined speed
to adjust the acceleration rote of the rotor and thereby change the
rotor speed towards a desired speed. .Iaddend..Iadd.
50. A method according to claim 49 further comprising the steps
of
sensing resistance of the rotor to rotation by setting an
acceleration rate,
sensing the speed of the rotor obtained in a given time period,
and
comparing the obtained speed with said desired speed of rotation
and adjusting the power applied in the step of applying power
during a next cycle, to achieve an acceleration rate which will
accelerate the rotor closer to the desired speed.
.Iaddend..Iadd.
51. A method according to claim 49 or 50, further comprising the
steps of effecting acceleration causing the rotor to rotate
initially just below the desired speed during one of said cycles
and adjusting the application of power so that the speed rises to
said desired speed in a later one of said cycles.
.Iaddend..Iadd.
52. A method according to claim 49 or claim 50, further comprising
the steps of effecting acceleration to cause the rotor to
accelerate to a speed just above the desired speed and adjusting
the application of power so that the speed falls to said desired
speed. .Iaddend..Iadd.
53. A method according to claim 49 or 50, further comprising the
step of adjusting acceleration of the rotor so as to cause one of
an overshoot and undershoot in rotor speed in relation to the
desired rotor speed after acceleration to give a desired
vigorousness of motion to the rotor. .Iaddend..Iadd.
54. A method according to claim 49 or 50 wherein the motor further
comprises a stator and windings and further comprising the steps
of
a) initiating and then continuing a correct sequence of
commutations of power to the windings selected from a desired time
of and a desired number of commutations, causing the rotor to
rotate in one direction,
b) reversing all of the power from the windings and allowing the
rotor to coast towards zero speed or rotation,
c) testing and establishing a position of the rotor relative to the
stator at least during a latter part of the coasting of the rotor,
and
d) when the rotor has slowed to a condition in which application of
reversed commutation will cause reversal of rotation but the rotor
is still rotating and the position of the rotor relative to the
stator is known, without delay applying power to the windings
effecting entry into the correct sequence of commutations, the
position of entry into the correct sequence being determined by the
direction of rotation of the rotor before stopping and the position
of the rotor relative to the stator, to cause the rotor to change
direction, the correct sequence of commutations following
automatically to maintain rotor rotation in the changed direction,
and repeating the steps of removing power and testing and
establishing, and without delay applying power to give cyclical
reversals in direction of rotation of the rotor for a desired time.
.Iaddend..Iadd.
55. A method according to claim 54, further comprising the steps of
following the direction and sequence of voltage representing EMFs
in said windings after power has been removed therefrom and, at
least as the rotor nears a position where it is in condition for
reversal, checking the voltage transition points between positive
and negative for each winding and changing the sequence of
commutations to cause reversal about the time when a voltage
transition point occurs in a selected winding. .Iaddend..Iadd.
56. A method according to claim 55, further comprising the steps of
testings the voltage representing EMFs from at least one of the
windings for polarity and frequency and changing the sequence of
commutation when the frequency has fallen to a value such that the
rotor is in condition for reversing and the polarity is
substantially at a zero crossing between opposite polarities in a
selected winding. .Iaddend..Iadd.
57. A method according to claim 56 wherein the step of testing
comprises testing all of the windings. .Iaddend..Iadd.
58. A method according to claim 55 further comprising a step of
enabling the change in the sequence of commutations to occur within
a single commutation change to cause a change in direction or
rotation of the rotor. .Iaddend..Iadd.
59. A method according to claim 49 wherein the motor is an
electronically commutated motor and the recited steps are applied
to such motor. .Iaddend..Iadd.
60. An electronic controller for cyclically controlling the supply
of electrical power to an electric motor having a rotor, a stator
and windings, comprising
a) setting means operable to set a desired speed of rotation of the
rotor,
b) means for setting an initial rate of supply of power and
applying that rate of power to said motor for a predetermined
period to accelerate said rotor to attain an initial speed and to
substantially maintain that speed,
c) speed determining means for determining said initial speed which
speed is dependent on the resistance to rotation of said rotor,
d) switching means to switch off the supply of power to said motor
after said predetermined period,
e) adjusting means responsive to said speed determining means for
adjusting the supply of power to the motor in accordance with the
previously attained speed to adjust the acceleration rate and
thereby change said initial rotor speed towards a desired speed,
and
f) reversing means operable when said rotor is in a condition for
reversal for causing cycles of forward and reverse rotor rotation
to be repeated. .Iaddend..Iadd.
61. An electronic controller according to claim 60 further
comprising sensing means for sensing resistance to rotation of the
rotor, said sensing means comprising timing means to measure the
time the rotor takes to run down from switching power off to the
motor to the condition for reversal. .Iaddend..Iadd.
62. An electronic controller according to claim 60 or 61, wherein
the reversing means comprises
a) switching means to disconnect power from said windings to allow
the rotor to run down towards zero speed of rotation,
b) detecting means to test, establish and indicate rotor position
relative to said stator, and
c) pattern reverse means operable in response to a signal from said
detecting means, when the rotor has slowed to a condition in which
application of reversed commutation will cause reversal of rotation
but the rotor is still rotating, for issuing control signals to
effect entry into a sequence of commutations to cause said rotor to
change direction without testing for rotor
direction..Iaddend..Iadd.
63. An electronic controller according to claim 62 wherein the
reversing means further comprises one of timing means to time the
period of rotation and counting means to count the number of
rotations of the rotor in a desired direction..Iaddend..Iadd.
64. An electronic controller according to claim 60 or 61, further
comprising
a) a commutating circuit responsive to control signals to cause
electrical power from a power source to be applied commutatively to
said windings for causing said rotor to rotate in a desired
direction,
b) testing means responsive to any EMF generating in at least one
unpowered winding to test the frequency and polarity of EMFs
generated in that unpowered winding, and
c) commutation reversing means for reversing commutation to give
the correct sequence of commutation to rotate the rotor in the
desired direction when the frequency has fallen to a value at which
the rotor is in condition for reversal and the polarity of a
selected winding is substantially at a zero crossing between
opposite polarities..Iaddend..Iadd.
65. An electronic controller according to claim 60, further
comprising braking means to brake the rotor, the braking means
comprising switching means, having an impedance, for connecting one
end of one winding to one end of another of said windings through
said impedance, the other ends of said windings being connected
together, and comparator means for comparing the voltages between
opposite ends of the windings for establishing the speed of the
rotor during braking..Iaddend..Iadd.
66. An electronic controller according to claim 60, wherein said
electronic controller is adapted for controlling an electronically
commutated motor..Iaddend..Iadd.
67. An electrical control for cyclically controlling the supply of
electrical power to an electric motor having a rotor, a stator and
windings, said electrical control comprising
switching means for switching power to said motor on and off,
power timing means for controlling the length of the power on
time,
coast timing means for timing the length of time said rotor takes
from the time power is switched off thereto to the time when said
rotor is in a condition for reversal of direction of rotation,
stroke time setting means for setting a desired value of the stroke
time during which said rotor rotates in one direction between
reversals,
algebraic subtracting means for algebraically subtracting a
previous coast time from said stroke time to yield a result
corresponding to a time setting for said power on time,
reversing means for reversing the direction of said rotor when said
rotor is in the condition for reversal and for switching on said
switching means when reversal is to be effected, and
means for repeating the operation thereof, enabling selected ones
of the previously recited means for a desired length of
time..Iaddend..Iadd.
68. Electrical control according to claim 67, further comprising
means for providing commutation signals to the windings, and
wherein the reversing means comprises
counting means for counting the time of the period of rotation or
the number of rotations of the rotor in a desired direction,
commutation switching means for disconnecting power from said
windings,
detecting means for indicating rotor position relative to said
stator, and
pattern reverse means responsive to a signal from said detecting
means for issuing control signals to cause commutation signal
changes to the windings which cause said rotor to change rotational
direction without testing for rotor rotational
direction..Iaddend..Iadd.
69. Electrical control according to claim 68 further comprising
a commutating circuit responsive to said control signals for
causing electrical power from a power source to be applied
commutatively to said windings for causing said rotor to rotate in
a desired direction,
testing means responsive to any EMF generated in at least one
unpowered winding to test the frequency and polarity of EMFs
generated in that unpowered winding, and
the pattern reversing means comprising commutation reversing means
to reverse commutation to give the correct sequence of commutation
to rotate the rotor in the desired direction when the frequency has
fallen to a value at which the rotor is in condition for reversal
and polarity in the unpowered winding is substantially at a zero
crossing between opposite polarities..Iaddend..Iadd.
70. Electrical control according to claims 67, 68 or 69 comprising
rotor braking means, the braking means comprising switching means,
having an impedance, for connecting one end of one of said windings
to one end of another of said windings through the impedance, the
other ends of said windings being connected together, and
comparator means for comparing the voltages between opposite ends
of the windings for establishing the speed of the rotor during
braking..Iaddend..Iadd.
71. Electrical control according to claim 70 wherein the stroke
time setting means is variable..Iaddend..Iadd.
72. Electrical control means according to any one of claims 67, 68
or 69 comprising
setting means for setting a desired speed of rotation of the
rotor,
means for setting and applying an initial rate of supply of power
to said motor for a predetermined period of time to accelerate said
rotor to attain an initial speed and to maintain that speed,
speed determining means for determining said initial speed
dependent on the resistance to rotation of said rotor,
wherein the switching means is adapted for switching off the supply
of power to said motor after said predetermined period of time,
adjusting means responsive to said speed determining means for
adjusting the supply of power in accordance with the previously
attained rotor speed to adjust the acceleration rate and thereby
change said initial rotor speed towards a desired speed, and
the reversing means being operable when said rotor is in condition
for reversal for selectively causing cycles of forward and reverse
rotor rotation to be repeated..Iaddend..Iadd.
73. Electrical control according to claim 72 further comprising
means for sensing resistance to rotation of the rotor, which means
for sensing resistance comprises timing means for measuring the
time the rotor takes to run down from a power off condition to the
condition for reversal..Iaddend..Iadd.
74. Electrical control according to claim 68 wherein said detecting
means comprises means for detecting the direction and sequence of
EMFs in at least one of the windings after power has been removed
therefrom and for detecting voltage transition points between
positive and negative polarity, said pattern reverse means being
operative for reversing the sequence of commutations substantially
at the time when a voltage transition point occurs in said at least
one winding..Iaddend..Iadd.
75. Electrical control according to claim 68 wherein said electric
motor is an electronically commutated motor..Iaddend..Iadd.
76. A method of cyclically reversing an electronically commutated
motor having a plurality of windings on a stator and a rotor having
magnetic poles rotatable relative to said stator to create back
EMFs and using electronic control apparatus comprising a
microprocessor, said method comprising the steps of:
(a) applying power to the motor to provide power to the windings to
initiate and continue a sequence of commutations selected from a
desired time of, and desired number of, the commutations;
(b) turning off power to the motor to remove all power from the
windings and allow the rotor to coast toward zero speed of
rotation;
(c) determining a direction in which the rotor is rotating using
the back EMFs created by the rotor and windings;
(d) determining when the rotor has slowed sufficiently to be in a
condition for reversal of direction by (i) sensing when the back
EMFs are at a first reference value and sensing when the back EMFs
reach a second reference value, (ii) determining that the rotor is
in the condition for reversal if an elapsed time between the
reference values is at least equal to a predetermined commutation
time period, and (iii) if the elapsed time is less than the
predetermined commutation time period, repeating the step (i) of
sensing using new first and second reference values, and the step
(ii) of determining, until the elapsed time is at least as great as
the predetermined commutation time period; and
(e) reversing the rotor by reversing the sequence of commutations
based on the rotor direction and using back EMFs as an indication
of rotor position, when the rotor is in the condition for
reversal..Iaddend..Iadd.
77. The method of claim 76 wherein step (d)(ii) further comprises
determining that the rotor is in the condition for reversal, where
elapsed time from sensing the first reference value is at least as
great as a predetermined minimum time period, without sensing the
second reference value, the predetermined minimum time period being
greater than the predetermined commutation time
period..Iaddend..Iadd.
78. The method of claim 77 further comprising the step of timing
elapsed time from the turning off of power to motor, and applying
dynamic braking to the rotor when the condition for reversal is not
reached within a predetermined maximum time
period..Iaddend..Iadd.
79. The method of claim 78 wherein the predetermined minimum time
period is 40 milliseconds, the predetermined commutation time
period is 20 milliseconds, and the predetermined maximum time
period is 150 to 200 milliseconds..Iaddend..Iadd.
80. The method of claim 78 wherein the first and second reference
values correspond to a first position of the rotor where one of the
windings has its back EMF cross zero volts and a next position of
the rotor where one of the windings has its back EMF cross zero
volts, respectively..Iaddend..Iadd.
81. The method of claim 76 further comprising the step of timing
elapsed time from the turning off of power to the motor, and
applying dynamic braking to the rotor when the condition for
reversal is not reached within a predetermined maximum time
period..Iaddend..Iadd.
82. The method of claim 76 wherein the first and second reference
values correspond to a first position of the rotor where one of the
windings has its back EMF cross zero volts and a next position of
the rotor where one of the windings has its back EMF cross zero
volts, respectively..Iaddend..Iadd.
83. The method of claim 82 further comprising the steps of
indicating a direction and sequence of back EMFs in the windings
after power has been removed therefrom and at least as the rotor
nears a position where the rotor is in the condition for reversal,
checking voltage transition points between positive and negative in
at least one of the windings caused by the back EMFs in the at
least one of said windings, and wherein the step of reversing
further comprises applying power to the motor and effecting entry
into a correct sequence of commutations to achieve reversal of the
rotor, the sequence of the commutations being entered about a time
when such voltage transition point occurs in a selected
winding..Iaddend..Iadd.
84. The method of claim 76 wherein, in the step (d)(iii) of
repeating, the new first reference value corresponds to a previous
second reference value..Iaddend..Iadd.
85. The method of claim 76 wherein the rotor rotation direction is
one of clockwise and counterclockwise, and the direction is
determined by the sequence of back EMFs generated from the
windings, and wherein reversal is effected by applying voltage to
at least some of the windings which is opposite in polarity from
the sequence of back EMFs..Iaddend..Iadd.
86. The method of claim 85 wherein there are three windings
connected to a common central point at a reference voltage, and the
windings are spaced 120.degree., the three windings comprise a
first winding (A), a second winding (B), and a third winding (C),
and the step of reversing comprises applying a correct sequence of
commutations to the windings to effect reversal, wherein if the
rotor is rotating clockwise, power is applied to the windings to
effect counterclockwise rotation, as follows:
if the back EMF from the first winding is positive (A+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (A-) across the first
winding,
if the back EMF from the second winding is positive (B+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (B-) across the
second winding,
if the back EMF from the second winding is positive (B+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (B-) across the
second winding,
if the back EMF from the third winding is positive (C+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (C-) across the third
winding,
if the back EMF from the third winding is positive (C+), and from
the second winding is negative (B-), applying positive voltage (B+)
across the second winding and negative voltage (C-) across the
third winding,
if the back EMF from the first winding is positive (A+), and from
the second winding is negative (B-), applying positive voltage (B+)
across the second winding and negative voltage (A-) across the
first winding, and
wherein if the rotor is rotating counterclockwise, power is applied
to the windings to effect clockwise rotation, as follows:
if the back EMF from the first winding is negative (A-), and from
the third winding is positive (C+), applying positive voltage (A+)
across the first winding and negative voltage (C-) across the third
winding,
if the back EMF from the second winding is negative (B-), and from
the third winding is positive (C+), applying positive voltage (B+)
across the second winding and negative voltage (C-) across the
third winding,
if the back EMF from the second winding is negative (B-), and from
the first winding is positive (A+), applying positive voltage (B+)
across the second winding and negative voltage (A-) across the
first winding,
if the back EMF from the first winding is positive (A+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (A-) across the first
winding,
if the back EMF from the second winding is positive (B+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (B-) across the
second winding, and
if the back EMF from the second winding is positive (B+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (B-) across the
second winding..Iaddend..Iadd.
87. The method of claim 76 further comprising the step of
determining a position of the rotor when the rotor is in the
condition for reversal, to provide the indication of rotor
position..Iaddend..Iadd.
88. An apparatus for cyclically reversing an electronically
commutated motor having a plurality of windings on a stator and a
rotor having magnetic poles rotatable relative to said stator to
create back EMFs, said apparatus comprising:
(a) power on means for applying power to the motor to provide power
to the windings to initiate and continue a sequence of commutations
selected from a desired time of, and desired number of, the
commutations;
(b) commutation switching means for turning off power to the motor
to remove all power from the windings and allow the rotor to coast
toward zero speed of rotation;
(c) detection means for sensing back EMFs created by the rotor and
windings and for providing an indication of a direction in which
the rotor is rotating;
(d) means for determining when the rotor has slowed sufficiently to
be in a condition for reversal of direction, comprising (i) first
means for sensing when the back EMFs are at a first reference value
and for sensing when the back EMFs reach a second reference value,
(ii) second means for measuring an elapsed time for the back EMFs
to reach the second reference value after passing the first
reference value, and for determining that the rotor is in the
condition for reversal when the elapsed time is at least equal to a
predetermined commutation time period, and wherein the first means
is adapted for repeating sensing, when the elapsed time is less
than the predetermined commutation time period, using new first and
second reference values, until the elapsed time is at least as
great as the predetermined commutation time period; and
(e) means responsive to the means for determining when the rotor is
in the condition for reversal for reversing the rotor by reversing
the sequence of commutations based on the indication by the
detection means of rotor direction and an indication of rotor
position based on the back EMFs..Iaddend..Iadd.
89. The apparatus of claim 88 wherein the second means further
comprises means for determining that the rotor is in the condition
for reversal when an elapsed time for sensing the first reference
value is at least as great as a predetermined minimum time period
without sensing the second reference value, the predetermined
minimum time period being greater than the predetermined
commutation time period..Iaddend..Iadd.
90. The apparatus of claim 89 further comprising means for timing
an elapsed time from the turning off of power to the motor, and
means for applying dynamic braking to the rotor when the condition
for reversal is not reached within a predetermined maximum time
period..Iaddend..Iadd.
91. The apparatus of claim 90 wherein the predetermined minimum
time period is 40 milliseconds, the predetermined commutation time
period is 20 milliseconds, and the predetermined maximum time
period is 150 to 200 milliseconds..Iaddend..Iadd.
92. The apparatus of claim 90 wherein the first and second
reference values correspond to a first position of the rotor where
one of the windings has its back EMF cross zero volts and a next
position of the rotor where one of the windings has its back EMF
cross zero volts, respectively..Iaddend..Iadd.
93. The apparatus of claim 88 further comprising means for timing
an elapsed time from the turning off of power to the motor, and
means for applying dynamic braking to the rotor when the condition
for reversal is not reached within a predetermined maximum time
period..Iaddend..Iadd.
94. The apparatus of claim 88 wherein the first and second
reference values correspond to a first position of the rotor where
one of the windings has its back EMF cross zero volts and a next
position of the rotor where one of the windings has its back EMF
cross zero volts, respectively..Iaddend..Iadd.
95. The apparatus of claim 94 wherein the detection means senses
the sequence of back EMFs in the windings after power has been
removed therefrom and at least as the rotor nears a position where
the rotor is in the condition for reversal, the detection means
comprises means for checking voltage transition points between
positive and negative in at least one of the windings caused by the
back EMFs in the at least one of said windings and wherein the
means for reversing comprises means for applying power to the motor
and effecting entry into a correct sequence of commutations to
achieve reversal of the rotor about a time when a voltage
transition point occurs in a selected winding..Iaddend..Iadd.
96. The apparatus of claim 88 wherein the new first reference value
corresponds to a previous second reference
value..Iaddend..Iadd.
97. The apparatus of claim 88 wherein rotor rotation direction is
one of clockwise and counterclockwise, the detection means is
adapted for determining rotor direction by the sequence of back
EMFs generated from the windings, and the means for reversing
effects reversal by applying voltage to at least some of the
windings which voltage is opposite in polarity from the sequence of
back EMFs..Iaddend..Iadd.
98. The apparatus of claim 97 wherein there are three windings
connected to a common central point at a reference voltage, and the
windings are spaced at 120.degree., the three windings comprise a
first winding (A), a second winding (B), and a third winding (C),
and wherein in response to the detection means sensing that the
rotor is rotating clockwise, the means for reversing applies power
to the windings to effect counterclockwise rotation, as
follows:
if the back EMF from the first winding is positive (A+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (A-) across the first
winding,
if the back EMF from the second winding is positive (B+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (B-) across the
second winding,
if the back EMF from the second winding is positive (B+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (B-) across the
second winding,
if the back EMF from the third winding is positive (C+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (C-) across the third
winding,
if the back EMF from the third winding is positive (C+), and from
the first winding is negative (B-), applying positive voltage (B+)
across the second winding and negative voltage (C-) across the
third winding,
if the back EMF from the first winding is positive (A+), and from
the second winding is negative (B-), applying positive voltage (B+)
across the second winding and negative voltage (A-) across the
first winding, and
wherein in response to the detection means sensing that the rotor
is rotating counterclockwise, the means for reversing applies power
to the windings to effect clockwise rotation, as follows:
if the back EMF from the first winding is negative (A-), and from
the third winding is positive (C+), applying positive voltage (A+)
across the first winding and negative voltage (C-) across the third
winding,
if the back EMF from the second winding is negative (B-), and from
the third winding is positive (C+), applying positive voltage (B+)
across the second winding and negative voltage (C-) across the
third winding,
if the back EMF from the second winding is negative (B-), and from
the first winding is positive (A+), applying positive voltage (B+)
across the second winding and negative voltage (A-) across the
first winding,
if the back EMF from the first winding is positive (A+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (A-) across the first
winding,
if the back EMF for the second winding is positive (B+), and from
the third winding is negative (C-), applying positive voltage (C+)
across the third winding and negative voltage (B-) across the
second winding, and
if the back EMF from the second winding is positive (B+), and from
the first winding is negative (A-), applying positive voltage (A+)
across the first winding and negative voltage (B-) across the
second winding..Iaddend..Iadd.
99. The apparatus of claim 88 further comprising means for
determining a position of the rotor when the rotor is in the
condition for reversal, to provide the indication of rotor
position..Iaddend.
Description
This invention relates to electronic controls for electric motors,
laundry machines including such controls and/or methods of
operating said controls.
It is an object of the present invention to provide an electronic
motor control for controlling electric motors and/or a laundry
machine including such controls and/or a method of operating
.Iadd.a .Iaddend.laundry machine using such controls which will at
least provide the public with a useful choice.
Accordingly in one aspect the invention may broadly be said to
consist .[.in.]. .Iadd.of .Iaddend.a method of cyclically reversing
an electronically commutated motor having a plurality of windings
on a stator and a rotor having magnetic poles rotatable relative to
said stator and using electronic control apparatus and means to
indicate the position of the rotor, said method comprising the
steps of
(a) Initiating and then continuing a correct sequence of
commutations for a desired time or desired number of
commutations,
(b) Removing all power from the windings and allowing the rotor to
coast towards zero rotation,
(c) Testing the position of the rotor relative to the stator,
and
(d) When the rotor is in condition to be reversed and its position
relative to the stator is known, changing the sequence of
commutations to cause the rotor to change direction .[.the.].
.Iadd.to .Iaddend.correct commutations following automatically to
maintain rotor rotation in the changed direction, and repeating the
steps to give cyclical reversal for a desired time.
In a further aspect the invention consists in control apparatus for
an electronically commutated motor having a plurality of windings
on a stator adapted to be selectively commutated and a rotor having
magnetic poles rotatable relative to said stator said control
apparatus comprising:
(a) Timing means to time the period of rotation or counting means
to count the number of rotations of the rotor in a desired
direction,
(b) Commutation switching means to disconnect power from said
windings to allow the rotor to run down towards zero rotation,
(c) Detecting means to indicate rotor position relative to said
stator, and
(d) Pattern reverse means operable in response to a signal from
said detecting means when the rotor is in condition to be reversed
to cause the control signals to cause commutation changes which
cause said rotor to change direction without testing for rotor
direction.
In a still further aspect the invention consists .[.in.]. .Iadd.of
.Iaddend.a method of cyclically controlling the supply of power to
an electric motor having a rotor said method including the steps of
starting rotation of said rotor in one direction setting an initial
"power on" time during which power is applied to said motor,
switching off power at the end of said initial "power on" time,
causing the rotor to slow until in a condition to be reversed,
checking the ramp down time the rotor takes to slow to a condition
ready for reversal, causing reversal of direction of rotation of
said rotor, as soon as the rotor is in condition to be reversed,
and repeating the said steps as desired.
In a still further aspect the invention consists in a method of
cyclically controlling the supply of power to an electric motor
having a rotor said method including the steps of setting a desired
time of rotation of said rotor in one direction starting rotation
of said rotor in said one direction setting an initial "power on"
time during which power is applied to said motor, switching off
power at the end of said initial "power on" time, causing the rotor
to slow until in a condition to be reversed, checking the ramp down
time to rotor takes to slow to a condition ready for reversal,
causing reversal of direction of rotation of said rotor, applying
power to said rotor for a further "power on" time which is such
that said further "power on" time plus said ramp down time equals
said desired time, switching off power to said rotor at the end of
said further "power on" time, again checking the next ramp down
time reversing direction of the rotor to said one direction when
said rotor is in condition for reversal and applying power to said
rotor for a still further "power on" time which is such that said
still further "power on" time plus said next down ramp time equals
said desired time and repeating the cycles for a desired length of
time, adjusting the "power on" time at desired intervals of time so
that the adjusted "power on" time for a further half cycle plus the
down ramp time for a previous half cycle equals said desired
time.
In a still further aspect the invention consists in a method of
electronically cyclically controlling the supply of power to an
electric motor said method including the steps of setting a desired
speed of rotation of the rotor of the motor, sensing the resistance
to rotation of the motor and using responses from the sensing means
to actuate adjustment means to adjust the power supplied to the
motor to change the motor speed towards said desired speed and then
operate the motor within a range of speeds at or close to said
desired speed of rotation, switching off the supply of power to the
motor, stopping its rotation and then repeating the cycle of
operations with the motor running in the reverse direction.
In a still further aspect the invention consists in an electrical
control means for cyclically controlling the supply of electrical
power to an electric motor having a rotor said control means
comprising switching means to switch power to said motor on and
off, coasting timing means to time the length of time said rotor
takes from the time power is switched off thereto to the time when
said rotor is in condition for reversal of direction of rotation,
and reversing means to reverse the direction of said rotor when
said rotor is in condition for reversing and to switch on said
switching means when reversing is to be effected.
In a still further aspect the invention consists in an electronic
control means for cyclically controlling the supply of electrical
power to an electric motor said electronic control means including
setting means operable to set a desired speed of rotation of the
rotor of said motor, sensing means to sense resistance to rotation
of the motor and adjustment means responsive to said sensing means
to adjust the power supplied to the motor to accelerate said motor
towards the desired speed and to then operate the motor within a
range of speeds at or close to said desired speed of rotation,
switching means to switch off the supply of said motor after a
desired time and reversing means operable after the motor has
substantially stopped to cause the cycle of operating to be
repeated with the motor running in the reverse direction.
In a still further aspect the invention consists in an electrical
control means for cyclically controlling the supply of electrical
power to an electric motor having a rotor said control means
comprising switching means to switch power to said motor on and
off, power timing means to time the length of power time when power
is switched on, coasting timing means to time the length of time
said rotor takes from the time power is switched off thereto to the
time when said rotor is in condition for reversal of direction of
rotation, stroke timing means to time the stroke time during which
said rotor rotates between reversals setting means to set said
stroke timing means to a desired stroke time, algebraic subtracting
means to .[.algebracially.]. .Iadd.algebraically .Iaddend.subtract
a previous coast time from said stroke time to arrive at a time
setting for said power time and reversing means to reverse the
direction of said rotor when said rotor is in condition for
reversing and to switch on said switching means when reversing is
to be effected.
In a still further aspect the invention consists in a method of
operating a laundry machine having a container for a wash load of
soiled fabrics in wash water and a reciprocable agitator in said
container and an electric motor driving said agitator, said method
comprising the steps of starting rotation of said motor in one
direction setting an initial "power on" time during which power is
applied to said motor, switching off power at the end of said
initial "power on" time, allowing the motor to slow down until in a
condition to be reversed, checking the time between the power off
condition and a condition when the rotor is in condition to be
reversed causing reversal of direction of the rotor as soon as the
motor is in condition for reversal and repeating the said steps as
desired.
In a still further aspect the invention consists in a method of
operating a laundry machine having a container for a wash load of
soiled fabrics in water and a reciprocable agitator in said
container, an electric motor driving said agitator, setting means
to set a desired rate and amplitude of time and/or angle of
oscillating rotation of said agitator .Iadd.and .Iaddend.an
electronic control means controlling the supply of electrical power
to said electric motor in one of a plurality of sequences, said
method including the steps of setting a selected one of said
plurality of sequences so that said agitator is driven in
oscillating rotation during a wash phase in a sequence of washing
operations, sensing the resistance to oscillation of said agitator
due to the wash load in said container and adjusting the power
supplied to said electric motor so that a selected rate of removal
of soil from said soiled fabrics is substantially achieved.
In a still further aspect the invention consists in a laundry
machine including a container for a wash load of soiled fabrics in
water.Iadd., .Iaddend.a reciprocatable agitator in said
container.Iadd., .Iaddend.an electric motor driving said agitator,
setting means to set a desired rate and amplitude of oscillating
rotation of said agitator, electronic control means controlling the
supply of electrical power to said electric motor in one of a
plurality of selected sequences so that said agitator is driven in
oscillating rotation during a wash phase, selecting means for
selecting a desired one of said sequences so that a washing action
selected from such as delicate, regular, heavy duty, wool, and
permanent press washing actions is to be effected by the machine
said electronic control means including sensing means to sense the
resistance to oscillating rotation of said agitator due to the wash
load in the container and adjustment means responsive to said
sensing means to adjust the power applied to said electric motor so
that a washing action results such that a selected rate or removal
of soil from said soiled fabrics is substantially achieved.
To those skilled in the art to which the invention relates, many
changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the scope of the invention as defined in the
appended claims. The disclosures and the descriptions herein are
purely illustrative and are not intended to be in any sense
limiting.
Preferred forms of the invention will now be described with
reference to the accompanying drawings in which,
FIG. 1 is a block diagram of an electronic control circuit to
control an electronically commutated motor driving an agitator and
spin tub of a clothes washing machine,
FIGS. 2 and 3 illustrate EMFs in windings with the rotor rotating
clockwise in relation to FIG. 2 and counterclockwise in relation to
FIG. 3,
FIG. 4 is a diagram showing motor stator windings, and electronic
power commutation circuitry,
FIG. 5 is a circuit diagram of a voltage digitizing circuit used in
the invention.[...]. .Iadd.,.Iaddend.
FIG. 6 is a flow diagram of motor reversing sequences.[...].
.Iadd.,.Iaddend.
FIG. 7 is a flow diagram of deriving values of index and
.[.indexr.]. .Iadd.INDEXR.Iaddend.,
FIG. 8 is a flow diagram for determining the rotor position,
FIG. 9 is a graph showing the motor and hence the agitator velocity
profile during a half cycle of agitator oscillating rotation in a
wash mode.[...]. .Iadd.,.Iaddend.
FIG. 9a is as FIG. 9 but illustrating action when the stroke time
is variable,
FIG. 10 is a graph showing a series of acceleration profiles,
FIG. 11 is a graph showing resultant curves under operating
conditions between the completion of the acceleration mode and the
cutoff point of applying power to the motor,
FIGS. 12 to 16 are flow diagrams showing various phases of
operation of the control circuit of FIG. 1.[...].
.Iadd.,.Iaddend.
FIG. 16a is a diagrammatic view of a speed sensor for use with the
invention, .Iadd.and .Iaddend.
FIGS. 17, 18 and 19 are figures repeated from a Boyd & Muller
U.S. Pat. No. 4,540,921 to provide background to the present
invention.
This invention relates in general to a laundry machine with a
cabinet.Iadd., .Iaddend.a wash water container in its cabinet, a
spin tub in the container.Iadd., .Iaddend.reciprocating agitator in
the spin tub.Iadd., .Iaddend.and a motor for driving the agitator
in the spin tub. Specifically it relates to sensing means for
sensing the load on the agitator and adjusting means operating in
response to signals from the sensing means to adjust the power by
adjustment of the profile of velocity to the agitator as indicated
by a velocity/time graph such that soil removal and washing
activity remain substantially constant according to a desired
setting for different loads.
Laundry machines are required to wash a wide variety of fabrics and
garments. Different clothes and fabric types require different
treatment to achieve an appropriate wash action. In general, with
vertical agitator washing machines, as agitator velocity is
increased, soil removal and wear and tear also increase. An
appropriate balance between soil removal and wear and tear is
necessary. It is a major objective of laundry machines to wash each
type of fabric with an agitator action appropriate to the load type
and size. For example, clothes which fall into the broad category
of "delicates," often synthetic in origin, or fragile items which
are susceptible to damage during the wash but which are typically
only slightly soiled, require gentleness of wash action with less
emphasis on soil removal, whereas "regular" items such as cottons
which are strong when wet can withstand a more vigorous wash
action.
Conventional vertical axis laundry machines employ various types of
transmissions to convert rotary motion provided by an electric
motor into oscillatory motion at the agitator for their wash mode.
Such motors are generally of essentially constant speed types.
Therefore to provide wash actions suitable for loads ranging from
delicate garments to heavily soiled hard wearing garments requires
multiple gearing or switched speed motors each of which is costly.
Further, as wash load is increased towards rated capacity for a
constant amount of water, mean soil removal typically decreases and
mean gentleness increases. Variance of soil removal and gentleness
also .[.increaese.]. .Iadd.increase .Iaddend.indicating less
uniformity of wash action throughout the wash load. Therefore it is
difficult to maintain good wash performance with laundry machines
of this type under varying load conditions.
The use of agitator drive systems such as disclosed in the John
Henry Boyd Australian Patent Specification AU-A-85-183/82 AND THE
FISHER & PAYKEL United Kingdom Patent UKN2095705 wherein the
agitator may be directly driven by an electronically controlled
motor either with or without a simple speed reduction unit and
oscillatory rotation is enabled by periodic reversal of rotation of
the motor .Iadd.which .Iaddend.provides opportunity for varying the
speed and rate of reversal of the agitator to obtain the
appropriate balance between soil removal and wear and tear for each
category of load. However the problem of variation of soil removal
and also wear and tear with load size still remains.
In a first aspect of the invention the following describes
apparatus to carry out an oscillatory rotation of the agitator
during a washing phase of the cycle of operations of the washing
machine and then on command to spin the spin tub in a spin phase of
the washing cycle, and is principally concerned with the agitation
cycle.
In a further aspect of the invention, later in this specification a
detailed description is given of preferred forms of sensing means
to sense the wash load in the laundry machine, correcting means to
correct for velocity variations, adjusting means to adjust the
power applied to the agitator by modification of the profile of
velocity as indicated by a velocity/time graph, and setting means
to alter the stroke angle of the agitator such that soil removal
and wear and tear such that wash performance .[.remain.].
.Iadd.remains .Iaddend.substantially constant for a particular
setting with variation of load size.
The preferred form of the invention is an improvement on the
disclosure in the Boyd and Muller U.S. Pat. No. 4,540,921.Iadd.,
.Iaddend.the specification and drawings of which are incorporated
by reference herein.
For assistance in the full understanding of the present
invention.Iadd., .Iaddend.excerpts from the Boyd and Muller U.S.
Pat. No. 4,540,921 are inserted herein but no claim is made to the
subject matter .[.desribed.]. .Iadd.described .Iaddend.and claimed
in that Specification.
Referring to FIG. 1 of the drawings, .[.An.]. .Iadd.an
.Iaddend.electronically commutated motor (ECM) 2 is described in
detail in the Boyd/Muller U.S. Pat. No. 4,540,921.
The ECM 2 constitutes a stationary assembly having a plurality of
winding stages adapted to be selectively commutated, and rotatable
means associated with that stationary assembly in selective
magnetic coupling relation with the winding stages. The winding
stages are commutated without brushes by sensing the rotational
position of the rotor as it rotates within the stationary assembly.
DC voltage is selectively applied by commutation circuit 17 to the
winding stages in preselected orders of sequences leaving at least
one of the winding stages unpowered at any one time while the other
winding stages are powered in response to a pattern of control
signal from voltage digitizing circuit 13.
The control apparatus comprises a general purpose microcomputer 10
eg an intel 8049 which receives commands for example from a console
11 having a series of push buttons or other user operable controls
9 and the microcomputer 10 stores patterns of signals which feed
through a pulse width modulation control means 18 and a commutation
control signal generator 8 (which are described in more detail
later) to a three phase power bridge commutation circuit 17. The
necessary power supplies are fed by a DC .[.Power.]. .Iadd.power
.Iaddend.supply 12. In addition, signals are fed from a winding of
the ECM .Iadd.which .Iaddend.is unpowered when other windings in
the stator of the ECM are under power. This will be explained
further later. Signals from the motor windings are fed to a voltage
digitizing circuit 13, as described in the Boyd Muller
Specification and below in relation to FIG. 4 of this
specification, and are thence supplied to the microcomputer 10.
Power switching circuits also feed through a current sensing
circuit 5 to the microcomputer 10. A loop position error indicator
15 and a speed demand rate velocity timer .[.15.]. .Iadd.16
.Iaddend.are provided and a commutation rate sensing device 14 but
any other rotor speed and position varying device may be used as
will be explained further later. A pulse width modulation control
circuit 18 is provided.
In broad terms a clothes washing machine according to the present
invention when operated to cause washing, functions as follows.
The operator selects a desired set of washing requirements by
operating push buttons controlling its console microcomputer. As a
result the console microcomputer sends a series of data values to
the motor control microcomputer 10 and these are placed into
registers (memory locations) of the same .[.time.].
.Iadd.name.Iaddend., in the motor control microcomputer 10. Data
transmitted from the console is broken up into 3 groups:
Group 1 contains the command words:
00H-BRAKE
01H-WASH
02H-SPIN
03H-TEST
04H-MODIFY
05H-STATUS
06H-STOP
07H-PUMP
Group 2 contains error codes:
08H-PARAMETER range error detected
09H-PARITY error detected
0AH-COMMAND error detected
Group 3 contains parameter data:
0BH to 7FH
The motor control microcomputer program knows which group to expect
during each communication, therefore if the program has got out of
step with the console in any way this will be picked up as a range
error.
However due to this data structure some data in group 3 may be
outside their working range so within the listing some parameters
are offset after they have been received so that they fall within
the correct value to be used within the program.
To maintain function overviews, at the beginning of the wash cycle
the console microcomputer 19 controls the filling of the bowl.
While the bowl is filling, a spin command is sent to the motor
control microcomputer. The spin speed is very low, approximately 70
.[.rpm.]. .Iadd.RPM.Iaddend., and its main purpose is to mix the
soap powder while the bowl is being filled. Once the bowl is filled
the console then sends a WASH command to the motor controller
.Iadd.(microcomputer) .Iaddend.10 to start the agitate cycle. This
agitate cycle starts from rest, ramps up to speed, maintains this
speed for a predetermined time and then coasts to a stop all within
one forward or reverse cycle of the agitator. Once the agitator has
stopped the process is repeated in the opposite direction thus
producing an agitating motion. The console microcomputer 19
determines all these parameters which determine what sort of wash
is required eg. .[.gently.]. .Iadd.gentle .Iaddend.cycle, and is
loaded into the motor controller 10 before the start of the
cycle.
The motor controller 10 continually modifies these wash parameters
to account for the load in order to maintain the most effective
dirt removal to gentleness ratio. Because of the agitating motion
the load is shuffled around the bowl and this affects how fast the
agitator ramps to speed and how long it takes to come to a stop at
the end of the stroke. Therefore to maintain constant wash
effectiveness these parameters are monitored and modified each
stroke cycle to maintain the ideal conditions requested by the
console microcomputer.
The motor controller 10 will continue this action until it receives
another command from the console microcomputer .Iadd.19.Iaddend..
In a little more detail, the wash mode runs as follows.
On receiving a "WASH" command a jump is made to the WASH routine.
Low speed windings of the motor are set and a brake is set off. The
routine then waits for the .[.Console.]. .Iadd.console
.Iaddend.microcomputer to send the wash cycle parameters, ie:
(1) TSTROKE The time for rotation of the agitator in one
direction.
(2) WRAMP The time it takes to reach speed from rest.
(3) ENDSPD The velocity which the agitator must reach after the
wash ramp time is up.
When these have been placed in the appropriate registers they are
then checked for errors. Checks for other errors are also made
including a check to make sure the motor is stationary.
A routine now sets LORATE=ENDSPD=ACCSPD. LORATE is the motor speed,
ACCSPD is the speed that the motor must reach to obtain the correct
wash ramp rate. ACCSPD may become greater than ENDSPD to achieve
the correct acceleration ramp.
As is explained in more detail later, the speed rate timer RATETMR
used in the timer interrupt routine for the speed reference count
is loaded with the count set in LORATE previously.
The position error counter 15 is cleared and current trip and
pattern error circuits are reset. In the wash mode the program
bypasses the spin cycle routine.
At this point the plateau time, TFLAT, is calculated from the
original information sent by the .[.Console.]. .Iadd.console
.Iaddend.microcomputer. To do this it sets the coast time at 180
mS. This is a time chosen which guarantees that the motor will have
coasted to a stop with very little load. Thus the plateau time is
calculated:
TFLAT=TSTROKE-WRAMP-15(180 mS time count)
using a long timer a count of 15 gives:
127.times.96 uS.times..times.15=180 mS (approx).
The routines up to this point have only been setting the wash
parameters for the first stroke. The following values as referred
to above, are set in the random access memory in the motor control
microcomputer 10:
TSTROKE total stroke time, ie. from rest to peak speed and to rest
again.
WRAMP time to full speed
ENDSPD full speed count
LORATE (set at ENDSPD) speed rate
ACCSPD (set at ENDSPD) acceleration rate
ALGFLG (set FALSE) end of ramp flag
ENDFLG (set FALSE) plateau time flag
SLECTR position error counter
RATETMR (set at LORATE) sets speed reference to speed loop error
counter
TFLAT calculated from above parameters; time at maximum speed
At this point the wash cycle can begin.
To actually set the motor into motion we must first set bit pattern
pointers INDEXR and INDEX. For the wash cycle the direction of
motion has arbitrarily been set at CCW (counter clockwise) for the
first stroke, thus:
and the direction register DIRECT=01H for CCW. The wash ramp time
WRAMP is loaded into a long timer for the beginning of the wash
ramp cycle. Commutation now takes place, and the motor is started
up.
After passing through the required time for or number of
commutation routines the program ends. At the end of the agitate
cycle the console microcomputer 19 will send a command to the motor
controller microcomputer 10 to stop the agitate cycle and turn on
the pump to drain the wash bowl before going into the spin
mode.
As will be explained in more detail later, to enable motor reversal
to be effected the invention .[.requires to determine.].
.Iadd.determines .Iaddend.the position of the rotor during coasting
of the rotor after power to the stator has been cut off. It will be
clear however that this aspect of the invention cannot be put into
use until the rotor itself has been operating under an
electronically commutated sequence. Accordingly when the rotor has
been stopped e.g. at the very start of a washing cycle it is
necessary to start the motor when the position of the rotor is not
known. Accordingly the technique described in the Boyd and Muller
Specification in particular at page 55 is preferably used. In this
technique the digitized voltages received from the voltage
digitizing circuit are tested and as soon as complementary bits or
logic levels in the proper test bit order have been sensed
operations proceed to advance in sequence to commutate the winding
stages. If complementary bits are not sensed in the predetermined
proper test bit order in a predetermined time period.Iadd.,
.Iaddend.operations take place to advance commutations in the
sequence rapidly and force commutate the motor, thus causing the
rotor to oscillate briefly. Thus if for example clockwise rotation
is required and the sensing indicates that the rotor is starting to
run in the counterclockwise direction, the rotor runs for a short
distance in this direction (one or a few commutations occurring)
until the force commutating is effected to cause it to run in the
correct direction.
Thus referring to FIG. 4 there is provided a three phase motor 20
with a common point 21 and a switching bridge in which three
switching devices 22, 23 and 24 connect the lower supply positive
rail 25 to the ends of the windings 26, 27 and 28 and three further
switches 31, 32, and 33 connect the ends of the windings to the
power supply negative rail 35. The upper switches 22, 23 and 24 may
be referred to as the A+, B+ and C+ switches and the lower switches
31, 32 and 33 may be referred to as the A-, B- and C- switches.
When the motor is stationary there is no information as to the
position of the rotor so it is not known as to which pair of
switches to turn on to get the rotor to rotate in the correct
direction so a selected upper and lower switch are turned on.
Statistically there is a 50% chance the rotor will rotate in the
correct direction and a 50% change that it will rotate in the
incorrect direction. An algorithm is provided in the microprocessor
10 that once power has been applied senses whether the motor is
going in the correct or the wrong direction and in the event that
the rotor is rotating in the wrong direction the algorithm advances
commutation signals quickly through the sequence of commutations
until the correct sequence is adopted and the rotor synchronizes
with the commutated supply and is now running in the right
direction. It may take three or four switchings or more to
synchronize the rotor and so with the starting algorithm 50% of the
time it will start correctly and will just run into synchronism and
50% of the time it will start in the wrong direction and then stop
and recover and then come back in the right direction. Thus with
this arrangement every time the direction of the motor is reversed
then if the present invention as will be described further later is
not used then the motor is allowed sufficient time to coast to zero
and then is started up using this starting algorithm. This start up
algorithm is described in Boyd & Muller 4,540,921 more fully at
col 8 line 23 et seq and col 23 line 57 at seq and col 24 line 43
to col 26 line 44. There must be some random initial rotation ie.
some oscillation of the rotor and there must be time to start
correct direction of rotation.
A random start means that the rotor will start in the wrong
direction in 50% of all starts. Start up algorithm restores the
correct direction of rotation in a time dependent on the initial
rotor position, the pair of switches first energized and the motor
load.
With a three phase 8 pole ECM as described by Boyd and Muller there
are 24 commutations per rotor revolution. With an 8 to 1 coupling
ratio between motor and agitator (e.g. by belt and pullery
arrangement) and typical stroke angles of 145.degree. to
250.degree. of arc and acceleration times of 120 to 200
milliseconds respectively the motor is required to accelerate to
speed in the range of 7 to 30 commutations. At startup the motor
may require 1 to 2 communication angles to restore correct
rotation, a significant proportion of the acceleration period. The
resultant effect is a delay in reversal followed by rapid
acceleration to speed often with some overshoot.
Gentleness of wash action in the washing machine is related to the
acceleration of the agitator. Hence erratic reversal decreases
gentleness. Further, delays in reversals also can reduce the rate
of soil removal. The overall effect is reduction in desired wash
performance.
Thus according to the present invention a more positive
acceleration and consequently a more positive rate of soil
removement and rate of wash action is achieved by monitoring the
speed and position of the rotor while the rotor is coasting. When
the position of the rotor is monitored down to a position in which
it is in condition for reversal, power is switched to the motor
such that torque is generated to cause the rotor to reverse
direction preferably within a single communication angle and allow
the motor to run in the opposite direction without reverting to the
start up algorithm.
Accordingly the rotor may be accelerated up to speed and maintained
at speed using the power switching sequence as described in Boyd
& Muller 4,540,921 referring to tables 1 and 2 therein and in
particular at col 6, lines 24 to 39 where the following passage
appears:
"The winding stages of motor M as explained for instance in the
aforementioned Alley U.S. Pat. No. 4,250,544 are commutated without
brushes by sensing the rotational position of the rotatable
assembly or rotor 15 as it rotates within the bore of stator 13 and
utilizing electrical signals generated as a function of the
rotational position of the rotor to sequentially apply a DC voltage
to each of the winding stages in different preselected orders to
sequences that determine the direction of the rotation of the
rotor. Position sensing may be accomplished by a position detecting
circuit responsive to the back EMF of the ECM to provide a
.[.simultated.]. .Iadd.simulated .Iaddend.signal indicative of the
rotational position of the ECM rotor to control the timed
sequential application of voltage to the winding stages of the
motor."
The present invention is concerned with the monitoring of speed and
position of the rotor while coasting and using this information to
reverse the motor preferably in a single commutation.
If the rotor to the motor is rotated and voltage measurements taken
at the ends of the phases with respect to the star point 21 i.e.
the centre of the three phase windings, EMFs will be generated and
in FIGS. 2 and 3 such EMFs have been plotted. The .[.Figures.].
.Iadd.figures .Iaddend.illustrate a single electrical revolution of
the rotor in degrees and essentially show the wave forms of a three
phase generator with the exception that the wave forms instead of
being sinusoidal are trapezoidal. The three phases have been
indicated by the letters A (pecked line), B (full line) and C
(slashed line). For example in B phase it will be seen that in FIG.
2 the EMF goes from a maximum negative at zero degrees through zero
voltage to a maximum positive, stays at a maximum positive for
120.degree. then goes from maximum through zero voltage to maximum
negative stays at maximum negative for 120.degree. and then starts
to rise again from zero degrees. It will be seen that in FIG. 2 the
sequence (which represents rotation in a clockwise direction) has a
different sequence of EMF generations as compared with FIG. 3 which
represents a counterclockwise direction of rotation. Referring now
to FIG. 4, applying voltages to the windings and assuming that
winding 26 is A, winding 27 is C and winding 28 is B and that if we
wish to have power on the motor at zero degrees such that we have a
maximum EMF across the motor and thus maximum torque in clockwise
direction, switches 22 (A+) and 33 (C-) would be switched on,
connecting power from the positive rail 25 through switch 22 to the
A phase windings 20 through the neutral point 21 and the C phase
windings 27 through switch 33 to negative rail 35. Thus referring
again to FIG. 2 with the notation therein indicated to obtain
maximum torque in the motor the connections would be A+ and C- to
the 60.degree. angle and then B+ and C- at the 120.degree. angle to
B+ and A- to 180.degree. angle then C+ and A- to the 240.degree.
angle, C+, .Iadd.and .Iaddend.B- to the 300.degree. angle. A+ to B-
to the 360.degree. angle, the sequence commencing at A+ and C-
again. Thus there is a sequence of six different patterns and each
goes to 60.degree. of angle of rotation giving 360.degree. in
rotation. Referring to the tables herein. Table I .[.summarises.].
.Iadd.summarizes .Iaddend.the sequence of control signals required
for each step in the sequence described above. Referring to Table I
it will be seen that the rows numbered 5 down to 0 correspond to
the sequence of digital signals required to control the A+, B+ and
C+ switches 22 to 24 and the A-, B- and C- switches on or off. A 0
in the table indicates that the switch is turned on and a 1 in the
table denotes that the switch is turned off. This is a negative
notation because of the manner of operation of the microcomputer.
Two further control lines are used to control whether or not the
upper or lower switches are pulse width modulated to control motor
current. Thus the microcomputer 10 is programmed to contain the
pattern shown in Table I. The six columns from left to right for
each switch control line show each step in the sequence described
above with each step indexed from 0 to 5 in the row marked INDEX.
Counterclockwise rotation is obtained by applying the control
signals of Table 2 which is the reverse of the sequence of Table 1.
The value of INDEX therefore is a reference of position in the
commutation sequence for each tale at any time. At each commutation
INDEX is incremented by 1 until a maximum value of 5, then reset to
0 to continue the cycle. In each table another index is referenced
"INDEXR" as mentioned in connection with flow diagrams discussed
below. The INDEXR row has entries which are unique to each pattern
in the sequence and different for Table I and Table 2 so that a
given pattern is uniquely identified for clockwise and
counterclockwise rotation. Determination of the time for
commutation is explained in detail in Boyd/Muller and excerpts are
given later. Now during coasting (as described in the Boyd/Muller
Patent) transitions in signals from comparators monitoring EMF
signals contain position information. To repower the motor while
still spinning such that the motor continues to run in sequence in
the same direction requires that values of INDEX and INDEXR be
computed such that correct switching sequence is initiated as
explained in Boyd/Muller. In this specification .[.is.]. .Iadd.are
.Iaddend.explained methods of repowering the motor such that the
motor reverses direction by determining safe speeds for reversal
and computing suitable values of INDEX and INDEXR such that correct
switching sequence for reverse direction is initiated, preferably
in a single commutation period.
It will be noted from the diagram of FIGS. 2 and 3 that for any
60.degree. commutation interval in the unpowered phase the EMF is
going from the maximum in one sense through a zero to a maximum in
the other sense and it is that phase which is going to be turned on
in the next commutation interval so that the microcomputer can
determine when to turn that phase on by determining when that phase
crosses through the zero point. This is effected by the use of
voltage comparators for example by circuitry as shown in FIG. 5 in
which VA is a measure of this voltage to zero volts appearing in
winding 26, VB is a measure of the voltage to zero volts in winding
28 and VC is a measure of the voltage to zero volts in winding 27.
When for example a voltage VC is greater than the voltage VN on the
neutral point N (21) FIG. 4 the output of the comparator 36 will be
high. When the voltage is less than the voltage VN at the neutral
point, the output of the comparator 36 is low and the output of
these comparators is fed directly into the microcomputer 10 which
reads in the comparatives. It is to be noted that the output is
comparative when the circuitry is looking at the comparator for the
unused winding at any one time which will change sense when the EMF
in that winding crosses zero. The microcomputer is then informed
that it is almost time to commute in accordance with the present
invention with each successive zero crossing in a sequence, if
there is a low to high transition, the next one is a high to a low
transition, then low to high, high to low, and continuing in that
way. Thus the microcomputer knows where each winding is in the
sequence and it knows which of the comparatives to look for
.[.for.]. the next EMF sensing. The microcomputer looks for a
transition and it also knows whether it should be low going high or
high going low so that it can compute from the sequence where the
rotor is in relation to the windings and what the next indications
will be from the comparatives. Accordingly the microcomputer
follows either Table 1 or Table 2 depending on the direction of
rotation and cycles continue with the correct switches being turned
on at the correct time.
In the A,B, & C circuits of FIG. 5, as shown with reference to
the C circuit resistance 37 and capacitance 38 provide a filter
effect reducing the sensitivity to transients.
Now during coasting, the EMFs are still present in the motor and
thus zero crossing transistors will also still be present and
result in signals being sent by the comparators to the
microcomputer, these signals being digitized by the digitizing
circuit 13, FIG. 5.
The Boyd and Muller Patent describes operations for repowering an
ECM after coasting under control of the apparatus therein described
and is repeated with reference to FIGS. 17, 18 and 19 as follows,
see col. 30 line 36 and et seq of Boyd & Muller Patent.
"In FIG. 17 the relaying routine of step 588 is shown. Operations
commence with BEGIN 651 and proceed to produce the OFF pattern (all
ones on lines 62) at step 653 to turn off the motor M. At step 655
microcomputer 61 issues a Low on line DB6 (FIG. 3) producing a High
on line H from NAND gate 157, and causing relay 147 in high-low
speed circuit 41 to switch from the low speed connection
arrangement to a high speed connection arrangement. Microcomputer
61 waits for 10 milliseconds as by any suitable routine, such as
counting from a preset number down to zero, in step 657 in order to
permit the relay 147 armature 155 to come to rest in the high speed
position. However, during this waiting period, the rotor 15 of
motor M has, or may have, rotated through a significant angle for
commutation purposes. Accordingly, at step 659 a routine is
executed for determining the value of INDEX from the sensed
digitized voltages on comparator outputs A, B, and C of FIG. 6 when
the winding stages are temporarily unpowered, and resuming
producing patterns of digital signals on line 62 beginning with the
pattern of digital signals (and thus a corresponding set of control
signals from control signal generator 51) identified by the value
of INDEX so determined. The digitized back .[.emfs.]. .Iadd.EMFs
.Iaddend.for three wye-connected winding stages S1, S2 and S3 are
illustrated in FIG. 18 and tabulated in Tables III and IV for
clockwise and counterclockwise rotation respectively.
In FIG. 18 and in the first three rows of Tables III and IV, the
logic levels of the digitized voltages on input lines 0, 1 and 2 of
microcomputer 61 (FIG. 1, 4,540,921) are shown when rotor 15 (FIG.
2.Iadd., .Iaddend.4,540,921) is coasting. Each of the six columns
shows the logic levels of the digitized back .[.emfs.]. .Iadd.EMFs
.Iaddend.present at any given time. As the rotor turns, the logic
levels of a given column are replaced by the logic levels in the
column next to the right. When the right-most column is reached,
.[.the logic levels begin again in the left-most column is
reached,.]. the logic levels begin again in the left-most column,
cycling through the columns as before. FIG. 18 shows superimposed
on the logic zeros and ones a waveshape of the digitized back
.[.emfs.]. .Iadd.EMFs .Iaddend.on the input lines 0, 1 and 2. The
digitized back .[.emfs.]. .Iadd.EMFs .Iaddend.at any one time and
their changes to other values at other times bear sufficient
information to permit sensing the position of the turning rotor 15
and to identify the proper point in sequence for beginning
commutation of such turning rotor and for resuming commutation
whenever commutation is interrupted or discontinued. Accordingly,
the index-determining operations of step 659 as described in
further detail in FIG. 19 are used in relaying routine 588 in the
preferred embodiment, and are used in other embodiments of the
invention whenever it is desired to begin commutation in
sequence.
In FIG. 19 operations commence with BEGIN 671, and microcomputer
71, (FIG. 1.Iadd., .Iaddend.4,540,921) inputs all the lines 0, 1
and 2 of port P1 at once by masking with ALLHI=07 (binary
00000111). As a result there resides in microcomputer 61 (FIG.
1.Iadd., .Iaddend.4,540,921) a three bit binary number having
binary digits corresponding to each of the digitized voltages on
the three lines. This binary number is designated DATA1 and stored
in step 673. Then at step 675, microcomputer 61 inputs all the
lines 0, 1 and 2 of port P1 again in search of digitized voltages
corresponding to an adjacent column of digitized voltages in FIG.
18.
The digitized voltages just obtained in step 675 are sorted and
designated DATA2. In step 683, DATA1 is compared with DATA2. If
they are the same number, (i.e. DATA1-DATA2=.[.)) the.]. .Iadd.0).
The .Iaddend.rotor has not turned sufficiently to move to the
adjacent rightward column in FIG. 18 and in the Table III or IV
corresponding to the direction of rotation. When DATA1=DATA2 a
branch is made back to step 675 to input another set, or instance,
of digitized voltages until an instance of digitized voltages is
found at step 675 which is different from DATA1. At step 685, the
difference DATA2-DATA1 is computed.
When step 689 is reached, microcomputer 61 has stored values of
DATA1 and DATA2 which are in adjacent columns of one of the Tables
III or IV. Each Table III or IV lists values of R3, which is the
difference DATA2-DATA1, in the column corresponding to the
digitized back .[.emfs.]. .Iadd.EMFs .Iaddend.in DATA1. Beneath a
value of difference R3 in each .[.of.]. column of Tables III or IV
are values of INDEX and INDEXR. The values of INDEX and INDEXR are
precisely the values for identifying the proper Table 1 or Table II
and the proper column therein containing the digital signal
patterns which microcomputer 61 can and does then produce to resume
commutation of the winding stages at the proper point in sequence.
(Beneath the tabulated value of R3 in Table III is an entry
designated "Offset R3" which is a number calculated to the program
listing of Appendix I for microcomputer table lookup purposes).
If the direction is counterclockwise, a branch is made from step
689 for table lookup in a table in microcomputer 61 (FIG. 1 of
4,540,921) having the information found in Table IV in rows R3 and
INDEX. When INDEX is formed, INDEXR is reset by adding 12 to INDEX.
If the direction determined is clockwise, a branch is made from
step 689 to step 693 for table lookup in a table microcomputer 61
(FIG. 1, of 4,540,921) having the information found in Table III in
rows R3 and INDEX. INDEXR is reset as equal to INDEX when the
direction is clockwise. After step 691 or step 693 is executed.
RETURN 679 is reached.
The operation of FIG. 19 can be described more generally as
follows. Microcomputer 61 (FIG. 1 of 4,540,921) identifies
successive patterns of the control signals and of the digital
signals of Tables I and II by values of an index designated INDEX.
A value of the index is determined from the sensed digitized
voltages when the winding stages are temporarily unpowered.
Microcomputer 61 (FIG. 1 of 4,540,921) resumes producing successive
patterns of the digital signals which causes control signal
generator 51 (FIG. 1 of 4,540,921) to generate successive patterns
of the control signals in sequence beginning with a pattern of the
digital signals and control signals determined from the sensed
digitized voltages. The lookup table information stored in
microcomputer 61 (FIG. 1 of 4,540,921) is a function, i.e. a
predetermined correspondence between members of two sets of
numbers. The sets of numbers involved here are values of INDEX on
the one hand and values of the differences R3. Equivalently, Tables
III and IV can be regarded as tabulating INDEX as a function of
digitized back .[.emf.]. .Iadd.EMF .Iaddend.itself. It is also to
be understood that there are a multitude of equivalent ways made
known by the disclosure made herein, of setting up a function
relating the digitized back .[.emf.]. .Iadd.EMF
.Iaddend.information to some variable such as INDEX which can be
used to determine the proper point for beginning in sequence when
commutation begins again. When the successive patterns of digital
signals and control signals are identified by values of an index,
the index is advantageously determined as a function of a number
represented by the sensed digitized voltages when the winding
stages are temporarily unpowered, the microcomputer 61 (FIG. 1 of
4,540,921) resumes producing patterns beginning with the pattern of
the control signals identified by the value of the index so
determined. The index is determined as a first function of a number
represented by the sensed digitized voltages when the winding
stages are temporarily unpowered and the preselected sequence is
for clockwise rotation of the rotatable means 15 (FIG. 1 of
4,540,921) and determined as a second function of the number so
represented when the preselected sequence is for counterclockwise
rotation, and microcomputer 61 (FIG. 1 of 4,540,921) resumes
producing patterns beginning with the pattern of the control
signals identified by the value of the index so determined. The
value of the index is also determined as a function of the
difference of first and second numbers represented by different
instances of the sensed digitized voltages, and microcomputer 61
begins with the pattern of the control signals identified by the
value of the index so determined.
The value of the index is determined as a function of the
difference of first and second numbers represented by different
instances of the second digitized voltages unless one of the
numbers is in a set of predetermined numbers, such as 0 and 7, and
microcomputer 61 begins with the pattern of the control signals
identified by the value of the index so determined. A difference of
first and second numbers are represented by different instances of
the sensed digitized voltages is calculated and a value of the
index is determined as a function of the difference unless the
difference is in a set of predetermined numbers, such as 0, +3, and
-3, and microcomputer 61 (FIG. 1 of 4,540,921) begins with the
pattern of the control signals identified by the value of index so
determined. Microcomputer 61 (FIG. 1 of 4,540,921) in this way
prevents sensed digitized voltages representing a number in a
predetermined set, such as 1 and 7, from being used to determine
the beginning pattern of control signals. Microcomputer 61 (FIG. 1
of 4,540,921) repetitively senses the digitized voltages while the
winding stages are temporarily unpowered and determines the
beginning pattern of the control signals as soon as a change occurs
in any one of the sensed digitized voltages..[.".].
Table 3 herein is equivalent of Table III in the Boyd Muller
patent.
It is to be noted that in Boyd/Muller when the motor is operated in
the agitate mode to reverse motor direction a definite time is
allowed for the rotor to coast to a stop and then random restarting
is effected with a 50% chance that the rotor will start in the
wrong direction necessitating adjustment of the commutation to
reverse the rotor direction and accelerate to speed in the right
direction. This gives irregular accelerations to the rotor and thus
causes irregular washing action to result. Accordingly this
invention involves a precise or defined method which may be
implemented on a .[.programed.]. .Iadd.programmed .Iaddend.computer
for finding where the rotor is and where the switching in the
sequences will be. Thus with a transition the microcomputer
calculates which switches should be on at any one time.
If we want to start at that time we apply power with those switches
so set or indexed .[.these tables.]. and start applying power.
Timers are provided as follows:
SHORT TIMER, LONG TIMER, COMMUTATION TIMER
In this implementation an INTEL 8049 1-chip microcomputer is used
for motor control microcomputer 10. It contains an 8 bit timer.
This timer can be driven by either an external oscillator or
directly from the ALE pulse which is divided by a factor of 32
before entering the timer (ALE=CLOCK/32). The microprocessor clock
runs at 10 MHZ so therefore a (10 MHZ/15)/32=20.833 KHZ clock
signal is applied to the timer. This provides a count every 48
microseconds in the timer and in operation the timer is loaded with
a count of 2 thus providing an interrupt pulse every 96
microseconds. This interrupt rate provides the base timing to the
motor controller.
On interrupt the program is forced to jump to a Timer Interrupt
Routine. On entry to this routine the timer is reloaded with a
count of 2 to provide the 96 microsecond base time.
This routine has two major functions:
(i) Decrementing Timer Register counts every 96 microseconds, and
setting the appropriate timeout flag when the counts reach
zero.
There are three timer registers used.
(a) Short Delay Timer
(b) Commutation Delay Timer
(c) Long Delay Timer.
The registers (a) and (b) are decremented each interrupt, therefore
using a count of 01H to OFFH timers (a) and (b) can achieve time
intervals of 96 microseconds to 24 .[.millisenconds.].
.Iadd.milliseconds .Iaddend.(ie. 256.times.96 microseconds). For
extended time delays using register (c), an intermediate prescaler
register which is initially set to 7FH (127) is decremented every
interrupt. Only when the Prescaler Register reaches zero is the
register (c) decremented. Therefore the long timer can achieve time
intervals of 127.times.96=12 milliseconds to 127.times.256.times.96
milliseconds=3 seconds. In order for the main program to use these
time delays a count must be put into the appropriate Timer
Register. The timer flag must then be tested periodically to see
whether the time is up.
(ii) The second function of this routine is to provide the Speed
Demand Rate function 16 of FIG. 1. ie. to provide a count rate to
position error counter 15 equal to the required motor commutation
rate. This is achieved by setting the Speed Rate Timer Register
(RATETMR) equal to the count for the period of the required
commutation rate eg. ACCSPEED, ENDSPD. Thus on every timer
interrupt the RATETMR is decremented and once it is zero the
Position Error Counter 15 is decremented. The RATETMR is
automatically reloaded with the correct count and the cycle repeats
for continuous operation.
Referring now .[.the.]. .Iadd.to .Iaddend.FIG. 6 which is a flow
chart of the reversing sequence of the present invention it will be
assumed that the microcomputer has timed out the application of
power to the motor and the motor is switched off i.e. all power is
disconnected from the stator. A long timer 40 is set to 150-200
milliseconds preferably 180 milliseconds, in block 40 which is an
arbitrary maximum time of coasting. As stated power is turned off
as indicated in block 41 and a check is made in block 42 of the
register DIRECT provided in the microcomputer 10 to indicate
whether the motor is going clockwise or counterclockwise. In the
event that direction of rotation is clockwise the register value is
changed to counterclockwise ready for starting in the next
direction and vice versa, so that the appropriate blocks 43 and 44
are used as required. There is a second timer called the short
timer which is set in block 45 to a value of 40 milliseconds. This
timer provides a safety feature in that should the rotor stop then,
of course, the succession of EMFs will also stop and no measurable
signals will be transmitted to the microcomputer to work on.
Accordingly the second timer assists in avoiding maloperation.
There is a third timer called the commutation timer which is set to
20 milliseconds in block 46. Now that value corresponds to a rate
of occurrence of zero crossings sufficiently low as to allow
reversing to take place. Next there is a tag rotor (tag
corresponding to R3 in the Boyd Muller Specification) position
indicator which senses the position of the rotor in block 47. This
is related to Tables 4 and 5. Table 4 being used when it is
required to go from clockwise to counterclockwise and Table 5 when
it is required to go from counterclockwise to clockwise as is
explained more fully in FIG. 8. Thus a start is made by inputting
the values of A, B and C, that is the outputs of the voltage
digitizing circuit. These are stored in memory as data 1 (block 60
of FIG. 8). Then the values corresponding to the EMF signals are
inputted again and stored as data 2 .Iadd.in .Iaddend.block 61.
These data 1 and data 2 in are then compared in block 62. If they
are equal and if the short timer is not equal to zero in block 63,
that is to say a transition has not yet been reached the computer
(as indicated by line 48) takes the measurements again of A, B and
C, comparing them to the previous value. As soon as data 1 is not
equal to data 2, data 1 is then subtracted from data 2 and this
gives a value in hexadecimal for the transition. That is put into
the storage register called "Tag" block 64. Then the flow diagram
is traversed further to see if the modulus of data 2 minus data 1
equals 0, 1, 2 or 4 each of which is one of the allowed values. If
it is not, there is something wrong and it is a matter of going
back to the beginning and restarting the whole procedure again
because the values are incorrect for whatever reason. Normally
however such values are .[.correctand.]. .Iadd.correct and
.Iaddend.there is a valid change and the routine above set forth is
then moved out of. If there is no transition within 40 milliseconds
as indicated by the short timer then the rotor is down to a speed
at which reverse direction can take place. If a transition is
obtained within 20 milliseconds as indicated by commutation timer
then the rotor is still spinning at a rate greater than that
allowable for reversal and it is necessary to run through the
sequence again. If the long timer has not reached 0 as checked in
block 49 then we have to check to see if the commutation timer is
equal to 0 as checked in block 50 (FIG. 6), if it is not, then it
is known that the rotor is still spinning. The sequence goes around
monitoring the position, keeping up to date and getting a new value
of the rotor position every time the sequence has gone through. If
the long timer which is set for 180 milliseconds (a little longer
than the expected coating time), times out then it is necessary to
apply a dynamic brake, e.g. by short circuiting all the windings
one to the other. The short timer 45 is a safety device which
ensures that the routine is not continually gone through searching
for a timing out when in fact the rotor has stopped and although
looking for a change no such change will occur because there is no
EMF generated to create such a change. Thus when the commutation
period gets greater than 40 milliseconds the device times out.
Assuming that a transition has been found within the allowable
parameters then values are derived for INDEX and INDEXR at block 53
which is explained in detail in FIG. 7. When the rotor is down to a
speed at which reversal can take place, information stored in
register tag and direction register .[.diect.]. .Iadd.direct
.Iaddend.defines where the rotor is and its direction of rotation.
Accordingly values of INDEX and INDEXR according to either Table 4
(clockwise to counterclockwise rotor position sensing) or Table 5
(counterclockwise to clockwise rotor position sensing) are chosen
and windings energized which will cause a torque to the rotor which
cause the rotor to reverse direction from its previous direction.
If for example the EMF from the motor windings when the rotor is
coasting are those resulting from clockwise rotation, such EMFs
will follow the pattern of FIG. 2, and supporting the rotor is in a
position where EMF C is high, EMF B is low and EMF A is changing
from low to high i.e. the transition point 55 in FIG. 2 is reached
and has been reached in time greater than 20 milliseconds (in
normal operation) after transition point 56 has been reached. If
power were applied to continue in the same direction the switchings
to the windings would be A+ and B- but since it is required to
reverse direction and it will be seen that in FIG. 3 transition
point 57 corresponds to transition point 55 in FIG. 2 so that to
provide reverse torque switchings B+ and A- will energize the
required windings. In some circumstances energizing of C- intead of
A- may be used since EMF A is falling to the right of transition
point 57 while C is rising. Thus in Table 4, Index 3 relating to
Table 2 is chosen in preference to Index 4 and when the EMF in the
selected winding drop backs to zero due to rotor speed dropping to
zero commutation increments to .[.index.]. .Iadd.Index .Iaddend.4
in Table 2 and sequence continues in selected order. The position
loop error counter 15 is set to a restart value in block 53a the
speed demand rate 16 is set to a restart speed in block 53b and the
microcomputer then returns the timing to a main commutation
.[.programme.]. .Iadd.program.Iaddend.. Of course during agitate
the reverse routine shown in FIG. 6 is reverted to at each reversal
until the end of the wash cycle determined in this method by
command module 11 which commands microcomputer 10 to cease and a
further routine entered into e.g. draining then spinning.
It will be seen that by following the reverse routine in which the
position of the rotor is monitored down to a point and speed in
which the rotor is in condition for reversal a reversal can be
effected in a single commutation period causing the motor to pass
through the stop and reverse direction without loss of rhythm
unless braking has had to be effected. When braking is effected it
may be necessary to go back to the start routine above described in
which the selected switches are turned on and indications from the
windings used to indicate whether the rotor is moving in the right
direction. If it is not, then the motor is force commutated to
change direction of the rotor and pick up acceleration speed as
above described. However this does not happen usually in practice
but the smooth transition with change of direction within about one
commutation period effected.
Furthermore even with dynamic braking in which the motor winding
ends are connected together it is still possible to monitor the
velocity of the rotor down to the point of reversal thus reducing
the time in which reversal is effected. In the voltage digitizing
circuit of FIG. 5, unlike the .[.Body.]. .Iadd.Boyd .Iaddend.Muller
circuitry, the star point voltage VN is brought into the circuit
13. The voltage at the star point is the vector sum of the three
EMF's generated in the windings and varies at the cummutation rate.
The signals from the comparators are not in the same sequence as an
open circuit when coasting but are in synchronism with the rotor
and accordingly the velocity of the rotor can be measured and
reversal commenced when the velocity falls to a desired level. Thus
in testing for transitions when the agitating sequence has not been
interrupted then the changes which take place are monitored and the
numbers go from all 0's to all 1's not all at the same time, but
the pattern is sufficient to enable the time for reversal to be
determined.
Thus referring FIG. 4, braking is effected by making switches 31,
32 and 33 conductive there is a small voltage drop in these
switches and although VA, VB and VC all move together and therefore
it is not possible to tell the position of the rotor, the
comparators of FIG. 5 will detect small voltage variations (about 1
or 2 volts) between the VA, VB and VC voltage and the VN voltage to
enable the rate of movement to the indicated and passed on to
microcomputer 10.
TABLE I DATA FOR CLOCKWISE ROTATION DIGITIAL SIGNALS P2 Rail Line
Disable Sequence of Patterns 7 Top 0 1 0 1 0 1 6 Btm 1 0 1 0 1 0 5
(B-) 1 1 1 1 0 0 4 (C+) 1 1 1 0 0 1 3 (A-) 1 1 0 0 1 1 2 (B+) 1 0 0
1 1 1 1 (C-) 0 0 1 1 1 1 0 (A+) 0 1 1 1 1 0 INDEX: 0 1 2 3 4 5
INDEXR: 0 1 2 3 4 5 CONTROL: A+ B+ B+ C+ C+ A+ SIGNALS: C- C- A- A-
B- B- .[.DIGITISED.]. .Iadd.DIGITIZED.Iaddend. VOLTAGE 01 02 04 01
02 04 MASK: (B) (A) (C) (B) (A) (C)
TABLE I DATA FOR CLOCKWISE ROTATION DIGITIAL SIGNALS P2 Rail Line
Disable Sequence of Patterns 7 Top 0 1 0 1 0 1 6 Btm 1 0 1 0 1 0 5
(B-) 1 1 1 1 0 0 4 (C+) 1 1 1 0 0 1 3 (A-) 1 1 0 0 1 1 2 (B+) 1 0 0
1 1 1 1 (C-) 0 0 1 1 1 1 0 (A+) 0 1 1 1 1 0 INDEX: 0 1 2 3 4 5
INDEXR: 0 1 2 3 4 5 CONTROL: A+ B+ B+ C+ C+ A+ SIGNALS: C- C- A- A-
B- B- .[.DIGITISED.]. .Iadd.DIGITIZED.Iaddend. VOLTAGE 01 02 04 01
02 04 MASK: (B) (A) (C) (B) (A) (C)
TABLE I DATA FOR CLOCKWISE ROTATION DIGITIAL SIGNALS P2 Rail Line
Disable Sequence of Patterns 7 Top 0 1 0 1 0 1 6 Btm 1 0 1 0 1 0 5
(B-) 1 1 1 1 0 0 4 (C+) 1 1 1 0 0 1 3 (A-) 1 1 0 0 1 1 2 (B+) 1 0 0
1 1 1 1 (C-) 0 0 1 1 1 1 0 (A+) 0 1 1 1 1 0 INDEX: 0 1 2 3 4 5
INDEXR: 0 1 2 3 4 5 CONTROL: A+ B+ B+ C+ C+ A+ SIGNALS: C- C- A- A-
B- B- .[.DIGITISED.]. .Iadd.DIGITIZED.Iaddend. VOLTAGE 01 02 04 01
02 04 MASK: (B) (A) (C) (B) (A) (C)
TABLE I DATA FOR CLOCKWISE ROTATION DIGITIAL SIGNALS P2 Rail Line
Disable Sequence of Patterns 7 Top 0 1 0 1 0 1 6 Btm 1 0 1 0 1 0 5
(B-) 1 1 1 1 0 0 4 (C+) 1 1 1 0 0 1 3 (A-) 1 1 0 0 1 1 2 (B+) 1 0 0
1 1 1 1 (C-) 0 0 1 1 1 1 0 (A+) 0 1 1 1 1 0 INDEX: 0 1 2 3 4 5
INDEXR: 0 1 2 3 4 5 CONTROL: A+ B+ B+ C+ C+ A+ SIGNALS: C- C- A- A-
B- B- .[.DIGITISED.]. .Iadd.DIGITIZED.Iaddend. VOLTAGE 01 02 04 01
02 04 MASK: (B) (A) (C) (B) (A) (C)
TABLE V COUNTERCLOCKWISE TO CLOCKWISE ROTOR POSITION SENSING B 1 0
0 0 1 1 A 1 1 1 0 0 0 C 0 0 1 1 1 0 -- -- -- -- -- -- HEX: 3 2 6 4
5 1 TAG: 2 -1 4 -2 1 -4 (DATA2-DATA1) INDEX: 3 2 1 0 5 4 INDEXR: 3
2 1 0 5 4
Turning now to the second aspect of the invention, as stated above
the digitizing circuit 13 is responsive to the Back EMF of the ECM
2 to provide a simulated signal indicative of the position of the
ECM rotor.
Velocity control of the ECM 2 is provided by a microcomputer
controlled digital implementation of a position control loop
referred to later. Position and velocity feedback information is
contained in the outputs of the voltage digitizing circuit 13.
Commutation rate sensing software 14 in the motor control
microprocessor 10 supplies a count of one to position error counter
15 for each commutation. Each count decrements the counter by one.
The count rate is therefore proportional to motor velocity.
Requested velocity information is provided by speed demand rate
timer hardware/software 16 which supplies a count rate to position
error counter 16 equal to the required motor commutation rate, that
rate having been indirectly selected by appropriate actuation of
manual selection controls in the user controls 9. Speed demand rate
timer 16, amplifier stages, pulse width modulation controls 18,
commutation control signal generator 8, commutation circuit 17,
voltage digitizing circuit 13 and commutation rate sensing circuit
14 define the feed back position control loop the summation point
being the position error counter 15.
The position error counter 15 algebraically sums the positive pulse
rates for the speed demand rate 16 and the negative commutation
rate sensing device 14. The output from the position error counter
error counter 15 appears as an error signal being the algebraic
difference between the two counts which controls the current (and
hence power) in the motor by a Pulse Width Modulated Control
Circuit 18 with current limit control 5. The error is the
difference between the desired count as indicated from the speed
demand rate indicator 16 as compared with the commutation rate
device 14. A zero PWM rate is the equivalent of a zero count and a
100% PWM rate is the equivalent of a full scale count. This aspect
is explained more fully in U.S. patent .[.applicaton.].
.Iadd.application .Iaddend.U.S. Ser. No. 709043 by Neil Gordon
Cheyne filed 7 March 1985, now abandoned, with a continuation
application filed Aug. 24, 1987, Ser. No. 088,657, the
specification and drawings of which are incorporated herein by
reference and which explains improved pulse width modulated control
methods for controlling current (and hence power) to an inductive
load with special applications to D.C. Motors. In this way the
Digital Position control loop is arranged so that when the ECM is
rotating at a speed less than that requested by Speed Demand Rate
Timer 16 low speed power is increased until current limit is
effected to give faster acceleration but during steady speed
operation the error and hence PWM pulses are maintained and
controlled to control the power input to the ECM to that which is
sufficient to maintain speed.
User controls 9 are provided and in the preferred embodiment
include a command microcomputer 19 which translates the user
commands into signals to the motor control microcomputer 10. Thus
the speed demand rate is set by commands initiated by the user
controls 9 and these controls have commands relating to a wash
.[.programme.]. .Iadd.program .Iaddend.selection e.g. delicate,
regular, heavy duty, wool, permanent press and also a selector
relating to water level e.g. low, medium and high water level. Each
of these imposes a different power demand, stroke angle,
acceleration rate and speed from the other on the wash load imposed
on the agitator 1 which is mounted within a spin tub 3 and water
container 4 in the known way. In FIG. 1 the motor 2 is shown
driving direct to the agitator 1 but of course an indirect drive
could also be used.
The above describes an electronic controlling circuit which enables
the speed of the motor 2 to be controlled.
Referring now to FIG. 9 this indicates a profile of velocity
against time of one half cycle in the oscillatory rotation of the
agitator by the motor 2. As may be seen power is applied to the
motor to achieve three steps in the half cycle, an initial step 120
of acceleration from zero velocity to a desired maximum velocity a
second step 121 at which the maximum velocity is maintained until a
cutoff point 122 is reached when power is removed from the motor
and a third step during which the rotating assembly of the motor
and the agitator then coasts to a stop substantially in accordance
with either for example curve 123 or as is shown in smaller pecked
lines curve 124, the curve 124 starting from a different cutoff
point 125 which will be explained further later. Thus there are
three different times, an acceleration time 128, a plateau time
referenced 129 when substantially constant speed is maintained
subject to .[.matter.]. .Iadd.matters .Iaddend.discussed below and
a coasting time referenced 130. The sum of these times results in a
total stroke time.
Of these times the acceleration time 128 and the plateau time 129
are electronically controllable but the coasting time 130 is
dependent on mechanical conditions involving the inertia of the
rotating assembly including the rotor of the motor and the agitator
and associated drive gear against which is acting the resistance of
the load of fabrics placed in the spin tub 3. Accordingly the coast
time 130 will depend on and vary according to the load placed in
the washing machine plus other smaller factors such as the effect
of heating up of bearings.
A desired washing action will vary from a gentle action if the
"delicate" control is actuated to a heavy duty vigorous action if
the "heavy duty" control is actuated. In a particular washing
machine which has been made, five types of washing actions had been
provided as mentioned above namely delicate, regular, heavy duty,
wool and permanent press and three different water levels so that
it is possible to have 15 combinations or 15 different agitator
velocity profiles that must be achieved.
To do this command microcomputer 19 feeds commands based on
information from user controls 9 to the motor control microcomputer
10 which define the acceleration time, the stroke time and the
maximum speed of rotation according to the selection made in the
user control circuit 9 and which have been preprogrammed into the
command microcomputer 19.
Motor control microcomputer 10 retains this information and
commands the motor to agitate following the required profile via
the digital position control loop as explained below repeatedly
until instructed to stop by the command microcomputer 19.
The method for control of acceleration time 128 can be explained
with reference to FIG. 10.
In FIG. 10 are shown typical curves of the velocity/time showing
the effect of velocity demand on acceleration. Thus FIG. 10 is a
plot of velocity versus time for the motor. The information
provided by operating the user control in circuit 9 is based on the
motor being started at zero speed and that the contents of the
position error counter is at zero. Accordingly the command defines
an acceleration rate i.e. requested velocity that must be achieved
in the acceleration time 128 of FIG. 9. That velocity can be
provided either as motor RPM, agitator RPM or commutation rate and
suitable circuitry provided dependent on the type of information
provided. The various curves V1 to V4 in FIG. 10 show the different
acceleration rates resulting from velocity demand rates for one
resistance to rotation of the motor and show the time taken to
reach a maximum velocity or speed.
As can be seen in FIG. 9 acceleration rate increases with
increasing speed demand rate. Each curve is essentially linear over
its first portion. Time to reach requested speed is almost
independent of speed demand rate but is a function of the loop gain
of the position control loop.
For any given velocity profile the acceleration must be such that a
set speed i.e. the plateau speed 121 shown in FIG. 9 must be
achieved in a certain time. Accordingly the command must be set to
provide a definite acceleration rate i.e. reaching the set speed in
a given time. However the load on the agitator is not at this time
known and therefore initially a speed demand rate is
.[.initialised.]. .Iadd.initialized .Iaddend.which will reach the
maximum speed in the given time under arbitrary predetermined
conditions. The preferred method of operation is to initially set a
speed rate demand which will result in an acceleration rate which
is slightly less than that ultimately desired and then to adjust
the speed demand rate upwardly to the desired speed over the next
.[.dew.]. .Iadd.few .Iaddend.cycles. Thus giving a wash action
which is more gentle than would be obtained by moving quickly to
the maximum speed with the possibility of overload occurring. This
is achieved by adjusting the loop gain of the velocity control loop
in any known way such that the time taken to reach the required
plateau speed when speed demand rate timer 16 is loaded with that
plateau speed rate is greater than the range of times required. One
way is to adjust the error value contained in position error
counter 15 required to achieve 100% PWM rate. If the load in the
machine is light the agitator will accelerate to speed more quickly
than if the load is heavy. Accordingly the present invention
provides programming of the microcomputer such that the speed at
the end of the required acceleration time is measured. If that
speed is below the required speed the microcomputer issues an
instruction to increase the speed demand rate at the beginning of
the next agitator stroke. Similarly if the motor is above speed at
that time the command is to reduce the speed demand rate and thus
reduce the power applied to bring the motor up to the plateau
speed. This testing of the acceleration rate is carried out on each
half cycle whether that half cycle is in the forward direction as
shown in FIG. 20 or in the reverse direction. Thus the oscillating
rotation i.e. the back and forth motion of the motor 2 and the
agitator 1 is such that the resistance to oscillation or rotation
is measured at each half cycle and by modifying the acceleration
rate to always bring that acceleration rate to a position where the
plateau speed is achieved in the set acceleration time and
substantial uniformity of operation is thus attained. Thus
acceleration is controlled to achieve the desired plateau speed in
the desired time, and this acceleration speed is maintained within
practical limits.
Plateau speed is maintained by adjusting the speed demand rate 16
to the speed demand rate required for the plateau speed at time 127
in FIG. 9.
However consideration must now be given to the circumstances
illustrated in FIG. 11. In this figure the demanded velocity is
shown by a pecked line 137. A series of curves are shown, the upper
curve 131 showing an overshoot and curve 132 shows a lesser
overshoot while curves 133 and 134 show two undershooting curves of
velocity. This is brought about by the varying position error count
in the position error counter 15. If there is a heavy load it takes
considerable power to get to speed and the power to get to speed is
greater than that required to maintain that speed and that is
indicated by a large counter value in the position error counter 15
and hence a high PWM ratio in circuit 18. Accordingly at the time
of reaching the point 135 in FIG. 11 (which corresponds with point
127 in FIG. 9) there is more power applied to the motor than
required to maintain the motor at the demanded velocity 137 and the
motor will thus continue to accelerate for a short time and
overshoot as can be seen by either of curves 131 and 132. This can
be provided for by adjusting the value set in the position error
counter 15. If the initial position error count is set at a low
level there is an undershoot below point 135 with the power then
being levelled off by the above checking of the speed and comparing
that speed with a desired count rate or alternatively the
acceleration power can be maintained to above point 135 so that
there is an overshoot and then the automatic error counting is
carried out to reduce the overshooting curve down to the demanded
velocity straight line 137. The value of the position error counter
or the speed demand rate can be adjusted at any time under control
of the microcomputer so that the actual count can be updated or
modified as desired and since the counter is within the
microcomputer, it can be loaded at any time.
Now the value of that counter at 127 in FIG. 9 is an indirect
measure of the wash load. Where we have a high value in the counter
we have a large wash load, a small value in the counter shows a
small wash load. Now to further increase the power that we have
applied to the load as that load increases in excess of that
required to maintain the profile as explained to maintain a given
level explained in background we can adjust the amount of overshoot
to obtain any profile. What is done is that the value of the
counter is adjusted such that with only water in the bowl there is
no overshoot then as clothes are added or as the load is increased
the value is adjusted in the counter to allow small amount of
overshoot. This small amount of overshoot increases the stroke
length of the agitator slightly and increases the turnover in the
clothes. This is explained above in the background material but
essentially wash action is provided by movement of clothes through
the water and how vigorous this movement is determines the soil
removal. However by increasing the stroke length slightly the
required wash requirements are maintained. The acceleration rate
and velocity desired in for example delicate wash are such that
slight lengthening of the stroke angle does not result in excessive
washing action.
The function of maintaining acceleration rate by adjusting the
speed command rate and controlling overshoot allows slight
increases so that under very heavy loads the stroke length is
increased slightly. If the acceleration rate is not controlled then
typically with a velocity controlled motor if just a final speed is
requested, the error in position error counter increases and the
acceleration rate .[.decrease.]. .Iadd.decreases .Iaddend.with load
and results in a decreased stroke angle and lowered soil level
removal.
It is necessary now to look at the coasting time and curves of FIG.
9. As stated above the deceleration rates of the agitator and motor
are not electronically controllable. The rotating assembly can only
be allowed to coast to a stop or be braked to a stop and thus are
not electronically controlled. Now if the coast time were fixed so
that it could be guaranteed that the motor would coast to a stop
before an attempted reverse or almost to a stop before reversal
could be effected it would be possible to end up with a shorter
stroke time as the load increases because we have the
.[.sitation.]. .Iadd.situation .Iaddend.that the maximum time to
coast to standstill is when there are no clothes in the water. As
the clothes load increases the coasting time becomes shorter and
thus the area under the curve in FIG. 9 becomes less and since that
area is proportional to the stroke angle that we are applying to
the clothes load or the agitator if deceleration is effected more
quickly then the stroke angle applied to the load is decreased
which is disadvantageous. The opposite effect is however desired,
namely, that it is desired to increase stroke to the load as the
load increases and therefore the following technique is also
adopted. The stroke time is set to a predetermined figure by a
command received from circuit 9. This stroke time is for practical
purposes the same for all wash duties. This means that as the coast
time decreases the plateau time must be increased so that the point
122 in FIG. 9 is not a point fixed in time but a point which is
determined as follows. For each half cycle, the microprocessor
measures the time to coast from plateau speed to substantially zero
speed and the microprocessor subtracts that time from the stroke
time and also subtacts the required acceleration time from the
stroke time which leaves a plateau time required for the next
stroke so that for each half cycle of the agitator the
microprocessor calculates a new plateau time depending on the last
coasting time and as may be seen from FIG. 9 two different coasting
times and two examples of different plateau times are shown. In the
first the plateau time is the time to extend from point 127 to
point 122 and for the second, assuming the same acceleration time,
from the point 127 to the point 125 and the deceleration or
coasting curves are as shown by the lines 123 and 124 respectively.
Accordingly at least in the preferred form the invention comprises
the combination of the three techniques for controlling
acceleration and altering the acceleration time as desired
controlling the overshoot or undershoot in relation to the desired
maximum speed in the second zone of FIG. 9, recalculating the
plateau time for each half cycle depending on the coasting time in
the last half cycle and then reversing the rotating assembly
immediately at or near zero speed. This allows the maintenance of
any required washing performance. Corrections are made continuously
and by monitoring the curves such as those shown in FIG. 9 on
.[.a.]. .Iadd.an .Iaddend.oscilloscope it can be seen that
variations occur substantially all the time because the load on the
agitator may well depend on the position of the clothes in the
container and those clothes may be bunched or balled in some cases
and almost immediately the bunching can be freed by the agitator
action so that the load on a next half cycle is considerably
lighter than when the clothes are bunched during a previous half
cycle. The time to accelerate to a given speed may take a number of
strokes to settle which provides a high averaging effect which
prevents large disturbances. For example if a bunching of clothes
is only momentary then if it were not for some delay in averaging
out there could be violent disturbances in the speed of actuation
of the agitator and this could cause too vigorous an action and
with a heavy load then there is an increased power input which is
what is required.
In a less preferable alternative it is possible to allow the stroke
time to vary. In such an alternative the maximum speed would be
more closely monitored so that extra area under the curve of FIG. 9
and therefore the extra stroke angle for heavier loads would be
gained by extending the power cut off point as required.
The sequence of operations will now be explained in relation to the
flow diagrams shown in FIGS. 12 to 16. The flow chart of the main
routine shown in FIG. 12 can be explained with reference to FIG. 9.
This is the routine required to agitate and the first initial block
140 is shown in more detail in FIG. 13 where the notations are:
T-stroke is stroke time, W-ramp is ramp time, and End-speed is the
maximum required speed. Once .[.initialisation.].
.Iadd.initialization .Iaddend.has taken place there are four things
to do, first it is necessary to start at the beginning of the
stroke to accelerate till point 127 in FIG. 9 is reached to
maintain a plateau speed along the plateau 121 shown in FIG. 9 and
then to coast to a stop after power has been switched off at 122
and then to reverse the direction of agitation and recommence the
cycle in .[.a.]. .Iadd.an .Iaddend."upside down" disposition from
that shown in FIG. 9. These steps are shown in FIG. 12 where
acceleration is shown in block 141.Iadd., .Iaddend.maintain plateau
speed shown in block 142.Iadd., .Iaddend.the decelerate or coast is
shown in block 143.Iadd., .Iaddend.change direction is shown in
block 144.Iadd., .Iaddend.and additionally in block 145 there is a
decision to be made as to whether agitation is to be concluded and
if so the command microcomputer 19 sends a signal to the motor
control microcomputer to interrupt the sequence at a selected time
that agitation is to be ended. If the answer is no then the
accelerate maintain coast and change direction cycle is maintained
for a further cycle and so on until the interrupt signal is given.
A yes (Y) answer results in the end of agitation and the washing
cycle then goes into a further routine which does not form part of
the present invention.
Now referring to FIG. 13 when initialization is commanded the
parameters fed to the motor control microcomputer 10 are stroke
time and acceleration time but it is necessary for the plateau time
i.e. for the point of 122 to be calculated. Thus the acceptance of
the agitate parameters are shown in block 150 and in block 151
there is a calculation of the initial plateau time shown as initial
T-flat. This time is arbitrarily selected for the first stroke as
the stroke time (which is a set time) minus the ramp time W-ramp
which is the acceleration time and then an arbitrary 150
milliseconds which is taken to be a reasonable coasting time. Thus
for the first stroke the T-flat time equals the initial T-flat time
i.e. the time obtained by the calculation shown in block 151. This
procedure is necessary since on .[.initialisation.].
.Iadd.initialization .Iaddend.is no information as to what the real
coast time is going to be so an estimate is made and subsequently
after every stroke the actual coasting time is movement and used as
will be .[.explaind.]. .Iadd.explained .Iaddend.later.
As a next step it is necessary to .[.known.]. .Iadd.know
.Iaddend.the speed to which the motor is to be accelerated. Again
there is no information as to the speed likely to be attained in
the time interval 128 on applying a known amount of power and
accordingly as is shown in block 153 the speed to which the motor
is to be accelerated referred to as ACC speed is shown as being the
end speed i.e. the maximum speed to be obtained for the particular
wash .[.programe.]. .Iadd.program .Iaddend.selected and the end
speed for example as it is seen in FIG. 10 for any given velocity
demand. Acceleration at the commencement is virtually linear and if
commands are given to supply power to the motor so that a
substantially linear acceleration is obtained up to the fixed
demanded speed and for the first stroke the demanded velocity is to
be equal to the plateau speed i.e. End-speed. However as explained
above it is .[.preferably.]. .Iadd.preferable .Iaddend.to arrange
the gain of the position loop such that acceleration is always less
than normally required if initial acceleration speed demand rate
equals End-speed when the agitator is operating in water only. The
practical result of this is that End-speed or maximum speed is not
actually achieved in time interval 128 for the first stroke.
Looking .[.row.]. .Iadd.now .Iaddend.at FIG. 14 which is a flow
chart during the acceleration phase the timer is set to W-ramp
which is a fixed time in block 154. This timer is a timer which is
set to the time and then counts down to zero so it is set with an
initial value that is equal to the time that is required. It is set
running which automatically happens when the timer is loaded and
the microcomputer senses when it gets to zero so in future it knows
how long it has taken to do something so the acceleration time is
the acceleration portion shown in FIG. 9 namely slope 120. As shown
in block 155 the microcomputer then loads the speed demand rate 16
and this is set at a rate equal to the acceleration speed ACCSPEED
which for the .[.fist.]. .Iadd.first .Iaddend.stroke as we have
discussed above is the End-speed as shown in block 153 FIG. 13. As
shown in block 156 the rotor is started and acceleration takes
place while as shown in block 157 the timer runs down to zero and
at this stage the motor velocity will have reached about point 127
and at that point as shown in block 158 the actual speed is
measured by use for example of the commutation rate sensing shown
in block 14FIG. 1 where the interval between commutations is
measured by the motor control microcomputer. That actual speed is
compared with the speed which is required in block 159. If it is
less than the End-speed then the microcomputer checks to see if the
acceleration speed is less than an arbitrary maximum as seen in
block 160. If it is then the acceleration speed is incremented one
step and retesting is carried out one step as seen in block 161 and
retesting is carried out in the next half cycle. If the actual
speed is not less than End-speed or acceleration speed is not less
than the maximum then a check is made as in block 162 to check if
the actual speed is greater than the End-speed. If no, then again
the test is ended. If it is greater than End-speed, then as
indicated in block 163 tests are made to see if the actual speed is
greater than an arbitrary minimum, if so, then the acceleration
speed is decremented in the next half cycle by one step as
indicated in block 164. In this way the acceleration rate is
adjusted in the next half cycle to provide an acceleration which
will achieve the required demanded velocity within the time W-ramp.
As stated, this entire process is effected for each half cycle.
Looking now at FIG. 15 which is the flow chart to maintain the
plateau .[.speed. The.]. .Iadd.speed, the .Iaddend.timer has been
set to T-flat which initially was the timing calculated in block
151 of FIG. 13. At point 127 .[.FIG. 9.]. (.Iadd.FIG. 9.Iaddend.)
the speed demand rate is set to End-speed and the motor is intended
to just maintain that speed. If the motor is not up to speed or
above speed by this method the motor will automatically settle to
the End-speed. The position error counter is also adjusted for
whatever overshoot is required and this is illustrated in the flow
chart of FIG. 15 where a test is made by the microcomputer in block
165 to see if the acceleration speed is greater than the
.[.End-speed if.]. .Iadd.End-speed. If .Iaddend.not, then no
adjustment is made as indicated in block 166. If it is greater,
then the position error counter is adjusted by an increment which
is a constant K times the acceleration speed minus the End-speed.
Of course if undershoot is desired the sign in this formula would
be reversed. However in practice undershoot is not desired if the
required speed is not achieved after .[.initialisation.].
.Iadd.initialization .Iaddend.step. After the adjustment has been
made in block 173 the motor continues at its desired speed until
the timer counts down to zero as shown in block 174. At this stage,
which is point 122 on the curve of FIG. 9, power is cut off to the
motor. It is to be noted that the question of compensation is one
where if there is a large load of clothes then acceleration speed
will be much greater than the End-speed and an overshoot curve such
as that of 131 or 132. FIG. 11, will be followed and the result of
this is that the stroke angle will increase slightly as the load
increases. The higher the load the slightly greater the stroke
angle and this has an improved effect in maintaining a wash rate
substantially constant as between a light and a heavy load. It is
noted that the stroke time is maintained but the stroke angle
increases. With a traditional agitator washing machine with an
induction motor it has a fixed speed so that not only does the
stroke time stay the same but the stroke angle is virtually always
constant although under heavy load it may reduce slightly. With a
traditional machine the actual stroke profile virtually does not
change with load. The power that goes into the load increases but
only sufficient to maintain that profile. The present invention
modifies the profile in accordance with the load and that is novel.
Thus in modifying the profile the present invention actually
overadapts the acceleration power to give an overshoot to give a
greater area under the curve of FIG. 9 and thus apply extra power
where there is a heavier load which is a desired result of the
present invention. Thus the time to coast to zero is an indirect
measure of the load on the agitator.
Having reached point 122 and the time indicated in block 171 has
timed out as shown in block 174 a coasting time of 180 milliseconds
(just greater than the expected coast time) is chosen as shown in
block 175 (FIG. 16) the motor turned off as in block 176 and then
the motor coasts and the agitator will slow down under the load
imposed by the clothes and other frictional effects.
The microcomputer waits on speed to fall to zero or the timer to
empty to zero as shown in block 177 whether the time .[.reaches.].
.Iadd.reaches .Iaddend.zero or not is tested in block 178. If the
timer equals zero then braking is effected as shown in block 179
and the coding T-flat=initial T-flat selected in the microcomputer
as shown in block 180. In such a case the motor is restarted under
circumstances above outlined in which it may restart in the right
direction or the wrong direction at random and force commutating is
necessary as described above. If the timer does not equal zero, the
microcomputer is programmed to T-flat which equals the remainder of
the linear time plus the initial T-flat time. The time as shown at
180 in FIG. 16 to coast to zero speed is an indirect measure of the
load on the agitator. The position and speed of the rotor is
measured and the information supplied to the microcomputer as is
described above.
As described above, while the rotor is coasting, EMFs are generated
in the one or more unused windings and these EMFs can be sensed to
indicate when an EMF changes sense i.e. crosses over a zero point.
However other position or velocity and direction sensing devices
can be provided e.g. Hall effect devices or light intercepting
devices or with non-ECM type e.g. brush, indiction of synchronous
motors, it is still possible to measure the EMFs. However with such
motors we do not need to known position, only speed. Thus the
microcomputer senses when the rotor is approaching a position in
which it is in condition for reversing and the time taken to reach
this position is measured and used in calculating a new value of
T-flat for the next half cycle. This is effected by taking the
remainder of the timer of block 175 and if this time is not zero
then the rotor has reduced to zero speed in less than 180
milliseconds. Thus the calculation shown in block 151 (FIG. 13) of
T-STROKE minus W-ramp minus 180 milliseconds is modified by taking
away the difference between 180 milliseconds and the actual time
taken for the rotor to come (not shown in the flow diagram) and
that provides a new calculation for the plateau time which is
substituted for the calculation shown in block 151. However if the
timer does get to zero in block 178 then the rotor is braked to
stop in block 179 and the T-flat selected to be used is the initial
T-flat as indicated in block 180. Once the rotor is at or near
stopped, then unless the rotor has been braked to a stop as
illustrated in block 179 then for an ECM, reversal is usually
effected in a single commutation period as is described above.
In the event that agitation is to cease as illustrated at 145 in
FIG. 12 then other parts of the washing cycle take over for example
the drain is opened and the water allowed to drain out. As
described above, the coasting time of a previous half cycle is
algebraically subtracted from the stroke time to give the "power
on" time for the next half cycle. However different adjustments are
possible e.g. only every tenth or other number half cycle could be
used to make the adjustment or the coasting times over a period,
e.g. over one second averaged to give a "power on" time for the
next second.
An important aspect of the invention resides in the measuring of
the coast time from the stroke time to give a "power on" time for
the next .Iadd.half .Iaddend.cycle. Thus although this invention
has been described in relation to an electronically commutated
motor which gives added advantages in controlling acceleration
rates and maximum speeds, an important advantage of the invention
is this aspect can be gained using other motor types for example an
induction motor. Such a motor may only be accelerated in a manner
broadly .[.dependant.]. .Iadd.dependent .Iaddend.on the number of
poles in its rotor and the load. However by controlling the cut off
point 122 at which power is applied to the motor by subtracting the
coast time of one half cycle from the stroke time to give an
acceleration time and plateau time for the next half cycle,
considerable control is given to the rate of extracting dirt
consistent with a desired degree of gentleness of washing.
Thus referring to FIG. 16a, a speed sensor driven by a rotor has a
ring magnet 71 the multiple holes of which actuate a Hall effect
transducer 72, the signals from which are in the form of pulses
which vary in lines according to the speed of rotation of the ring
magnet 71. When the pulse time reaches a predetermined length of
time, reversing is effected.
Also photo sensitive devices can be used, for example as described
in U.S. Pat. No. 4,005,347 the specification and drawings of which
are incorporated herein by reference. In either case the time
between switching off power to the motor and the motor being in
condition for reversing is measured and used in a next half cycle
to determine the "power on" time which .Iadd.will .Iaddend.give the
required washing action.
Although the above descriptions are based on using a fixed stroke
time, the invention in this aspect can also be put into effect with
a .[.variably.]. .Iadd.variable .Iaddend.stroke time operation.
Thus where the stroke time is to be variable according to the load
in the washing tub and referring to FIG. 9a, which is similar to
FIG. 9, the acceleration time 81 plus the plateau time 82 are set
by the operator according to a required gentleness or vigorousness
of washing to a fixed "power on" time. A small load will give a
coast time indicated between points 83 and 84 with a delay curve
85. A large load gives a steeper delay curve 86 with a coast time
indicated between points 83 and 87 and accordingly the motor will
be in condition for reversal much earlier than in the light load
coast time curve 85. If reversing is thus effected with a shortened
stroke time more consistent washing performances will be obtained,
whether the load is small or large.
* * * * *