U.S. patent application number 11/877830 was filed with the patent office on 2009-04-30 for method and apparatus for determining an imbalance condition in an appliance.
Invention is credited to Mariano Filippa, Edward Hatfield, Richard D. Suel, II.
Application Number | 20090107185 11/877830 |
Document ID | / |
Family ID | 40342512 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107185 |
Kind Code |
A1 |
Filippa; Mariano ; et
al. |
April 30, 2009 |
METHOD AND APPARATUS FOR DETERMINING AN IMBALANCE CONDITION IN AN
APPLIANCE
Abstract
In one embodiment of the invention, an appliance and method is
provided that can determine load imbalance or out-of-balance
conditions. The appliances that typically apply load imbalance
detection are clothes washers. A method of imbalance detection
includes identifying parameter values that fluctuate with load
imbalance over a predetermined sample period and determining a
target parameter value from the identified parameter values. The
method further includes calculating a parameter spread of the
parameter values by comparing parameter values to the target
parameter value. The method further includes converting the
parameter spread into a weight value that reflects an imbalance
condition.
Inventors: |
Filippa; Mariano;
(Louisville, KY) ; Hatfield; Edward; (Louisville,
KY) ; Suel, II; Richard D.; (Louisville, KY) |
Correspondence
Address: |
General Electric Company;GE Global Patent Operation
PO Box 861, 2 Corporate Drive, Suite 648
Shelton
CT
06484
US
|
Family ID: |
40342512 |
Appl. No.: |
11/877830 |
Filed: |
October 24, 2007 |
Current U.S.
Class: |
68/12.06 |
Current CPC
Class: |
D06F 37/203 20130101;
D06F 35/005 20130101 |
Class at
Publication: |
68/12.06 |
International
Class: |
D06F 33/00 20060101
D06F033/00 |
Claims
1. A method for determining an imbalance condition in an appliance,
comprising: identifying parameter values that fluctuate with load
imbalance over a predetermined sample period; determining a target
parameter value from the identified parameter values; calculating a
parameter value spread of the parameter values by comparing
parameter values to the target parameter value; converting said
parameter spread into a weight value that reflects an imbalance
condition.
2. The method of claim 1 wherein the predetermined sample period
comprises a moving sample period.
3. The method of claim 1 wherein the target parameter value
comprises an average.
4. The method of claim 1, further comprising periodically
recalculating the target parameter value and identifying additional
parameter values.
5. The method of claim 1 wherein calculating said parameter value
spread comprises: calculating an average parameter value from said
parameter values; and comparing said average parameter value to
each said parameter value to arrive at an average deviation
value;
6. The method of claim 1 wherein converting said parameter spread
into a weight value comprises: dividing said parameter spread by a
load constant value.
7. The method of claim 6, wherein said parameter spread is
multiplied by current motor speed.
8. The method of claim 1, wherein the said parameter value
comprises speed.
9. The method of claim 1, wherein the said parameter value
comprises voltage amplitude required to maintain a constant
speed.
10. The method of claim 1, wherein said appliance is an automatic
washing machine.
11. The method of claim 1, wherein said washing machine is a
horizontal axis washer.
12. The method of claim 1, wherein said washing machine is a
vertical axis washer.
13. A computer program embodied on a computer-readable medium,
comprising: identifying parameter values that fluctuate with load
imbalance over a predetermined sample period; determining a target
parameter value from the identified parameter values; calculating a
parameter value spread of the parameter values by comparing
parameter values to the target parameter value; converting said
parameter spread into a weight value that reflects an imbalance
condition.
14. An appliance comprising: a vessel mounted for rotation about an
axis; a motor for rotating the vessel about an axis; a processor
configured to determine load imbalance; and a memory for receiving
and storing parameter data and instructions for determining load
imbalance; wherein the load imbalance is determined by: identifying
parameter values that fluctuate with load imbalance over a
predetermined sample period; determining a target parameter value
from the identified parameter values; calculating a parameter value
spread of the parameter values by comparing parameter values to the
target parameter value; converting said parameter spread into a
weight value that reflects an imbalance condition.
15. The device of claim 14 wherein the predetermined sample period
comprises a moving sample period.
16. The device of claim 14 wherein the target parameter value
comprises an average.
17. The device of claim 14, wherein the load imbalance is further
determined by periodically recalculating the target parameter value
and identifying additional parameter values.
18. The device of claim 14 wherein calculating said parameter value
spread comprises: calculating an average parameter value from said
parameter values; and comparing said average parameter value to
each said parameter value to arrive at an average deviation
value;
19. The device of claim 14 wherein converting said parameter spread
into a weight value comprises: dividing said parameter spread by a
load constant value based on the weight of the load in a
washer.
20. The device of claim 14, wherein said parameter spread is
multiplied by current motor speed.
21. The device of claim 14, wherein the said parameter value
comprises speed.
22. The device of claim 14, wherein the said parameter value
comprises voltage amplitude required to maintain a constant
speed.
23. The device of claim 14, wherein said appliance is a washing
machine.
24. The device of claim 23, wherein said appliance is a horizontal
axis washer.
25. The device of claim 23, wherein said appliance is a vertical
axis washer.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present invention generally relates to methods and an
apparatus for detecting imbalance conditions in an appliance.
[0003] 2. Description of the Related Art
[0004] Appliances such as automatic washing machines typically
contain rotatable vessels that are designed to hold material or
clothing and are known in the art. The vessel is contained within a
housing and is perforated with apertures. The apertures allow water
to be pumped into the vessel to wash the material in the vessel and
to allow soiled water to be forced out of the vessel. A washing
machine usually contains a main control panel that controls various
cycles, typically comprising a wash cycle, spin cycle, a rinse
cycle, followed by another spin cycle. Water is pumped into the
vessel during the wash cycle and rinse cycle, while it is extracted
via centrifugal force during the spin cycle as the vessel rotates
or spins. Additionally, a washing machine usually contains an
agitator that oscillates to facilitate washing where the vessel
rotates about a vertical axis. In machines that contain vessels
that rotate about a horizontal axis, an agitator is usually not
included as clothes can be tumbled instead of agitated in order to
facilitate in the washing process.
[0005] Appliances that contain rotatable vessels are subject to
operating conditions such as load imbalances. Load imbalances in
appliances such as washing machines occur when the material
contained in the vessels is not evenly distributed within the
vessel. The material may be unevenly distributed when loaded into
the vessel or may become unevenly distributed as the vessel
rotates. For example, in vertical-axis washing machines, when a
wash or rinse cycle completes and water is drained from the vessel,
the clothes are gathered at the bottom of the vessel without being
evenly distributed within the vessel. As the motor ramps up the
speed for the next cycle, the clothes can creep up the sides of the
vessel and become imbalanced.
[0006] Similarly, in horizontal-axis washing machines, load
imbalances can occur when clothes are not evenly distributed during
the machine's distribution cycle. Load imbalance conditions can
cause various inconveniences such as severe vibration and movement
of the appliance. Severe vibration occurs when a load is
imbalanced, or out of balance because the center of mass of the
rotating vessel no longer corresponds to the geometric axis of the
vessel. Severe vibration can cause an appliance to move along the
surface it rests upon, for example, when a washing machine moves
across the floor. Additionally, severe vibration can cause the
vessel to break free from its mountings. Another disadvantage of
load imbalance conditions is that the motor's power is wasted in
the vibrations and movement instead of being fully applied to
rotating the vessel.
[0007] Prior art solutions designed to prevent imbalance conditions
were typically mechanical and include adding masses to the
rotatable vessel of the appliance in order to counter-balance
imbalance conditions.
[0008] Other solutions that were designed to detect imbalance
conditions are typically complex and include comparing the actual
power usage of a vessel to an expected power usage and measuring
current ripples. One example of such an attempt is illustrated in
U.S. Pat. No. 6,640,374, where the amount of current used by the
motor to rotate the vessel is compared to a threshold value.
[0009] Accordingly, there is a need to provide an improved method
and apparatus to detect load imbalance conditions in an appliance
to allow for simplified design and manufacturing.
BRIEF DESCRIPTION OF THE INVENTION
[0010] In one embodiment of the invention, an appliance and method
is provided that can determine load imbalance or out-of-balance
conditions. The appliances that typically apply load imbalance
detection are clothes washers. A method of imbalance detection
includes identifying parameter values that fluctuate with load
imbalance over a predetermined sample period and determining a
target parameter value from the identified parameter values. The
method further includes calculating a parameter spread of the
parameter values by comparing parameter values to the target
parameter value. The method further includes converting the
parameter spread into a weight value that reflects an imbalance
condition.
[0011] In another embodiment of the invention, a computer program
embodied on a computer-readable medium includes identifying
parameter values that fluctuate with load imbalance over a
predetermined sample period and determining a target parameter
value from the identified parameter values. The method further
includes calculating a parameter spread of the parameter values by
comparing parameter values to the target parameter value. The
method further includes converting the parameter spread into a
weight value that reflects an imbalance condition.
[0012] In another embodiment of the invention, an appliance
includes a vessel mounted for rotation about an axis; a motor for
rotating the vessel about an axis; a processor configured to
determine load imbalance; and a memory for receiving and storing
parameter data and instructions for determining load imbalance. The
load imbalance is determined by identifying parameter values that
fluctuate with load imbalance over a predetermined sample period
and determining a target parameter value from the identified
parameter values. The method further includes calculating a
parameter spread of the parameter values by comparing parameter
values to the target parameter value. The method further includes
converting the parameter spread into a weight value that reflects
an imbalance condition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings are described herein:
[0014] FIG. 1a is a view of a horizontal-axis washing machine.
[0015] FIG. 1b is a diagram showing a horizontal-axis washing
machine.
[0016] FIG. 2 is a block diagram showing a system for detecting a
load imbalance in an embodiment of the present invention.
[0017] FIG. 3 is a flow diagram showing a method for detecting a
load imbalance condition.
[0018] FIG. 4 is a table containing load imbalance data.
[0019] FIG. 5 is a graph of the load imbalance data of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] One embodiment of the present invention concerns a method
and a circuit for detecting a load imbalance in an appliance that
is simple to implement.
[0021] Referring now to FIG. 1a, a horizontal-axis washing machine
in accordance with one embodiment of the present invention is
illustrated generally at 10. A horizontal-axis washing machine
includes a vessel that rotates about a horizontal axis within the
cabinet. Another embodiment of the invention includes a
vertical-axis machine where the vessel rotates about a vertical
axis within the cabinet. One of ordinary skill in the art can
perform the exemplary embodiments of the invention described herein
using either configuration. Washer 10 includes a motor 12 and a
motor control unit 14 (see FIG. 1b) that can also be integrated
within one unit. Washer 10 includes an outer housing or cabinet 20
supporting a fixed tub 22, a vessel or moving tub ("tub") 25, motor
12, and motor control unit 14, within which there is a processor
102, in a known manner. Vessel drive shaft 30 is also illustrated.
Tub 25 is configured to hold articles (not shown) such as clothes
to be washed.
[0022] In the horizontal washer configuration, a direct belt drive
is configured to transmit rotary motion imparted on a motor shaft
36 by motor 12 to tub 25 via drive belt 29. FIG. 1b illustrates a
side view of the exemplary washer of the present invention.
[0023] During a spin cycle, liquid within the articles is removed
by the centrifugal force imparted by the spinning vessel and is
allowed to exit the basket through apertures (not shown). During
the spin cycle, articles or clothing becomes plastered to the wall
of tub 25 at a first speed or plaster speed. Plaster refers to the
centrifugal force of the spin cycle pushing the clothing against
the wall or structure of the basket. The clothes remain positioned
by centrifugal force during a time period the first speed or
plaster speed to a second speed or maximum speed of the spinning
basket. The plastered speed and maximum speed can be determined by
one of ordinary skill in the art. Load imbalance conditions can
occur when the clothes are unevenly plastered throughout the
vessel.
[0024] FIG. 2 depicts a block diagram showing an appliance for
detecting a load imbalance in an embodiment of the present
invention. The appliance, which could be an automatic washing
machine 10, can include a cabinet 20, a vessel 25, a motor 12, and
a motor control unit 14 including a memory 101, a processor 102,
and a sensor 103. The cabinet 20 contains the vessel 25 that can be
loaded with material, for example clothes. The motor 12 drives the
vessel and can be directly attached to the vessel by a belt,
clutch, or a direct coupling, for example. The motor can be any
type, including an induction motor. The sensor 103 can detect the
rotation speed of the motor shaft along with other parameters that
fluctuate due to load imbalance, such as voltage amplitude, torque
and motor current, for example. Any type of sensor can be used,
including a hall sensor to detect the rotation speed of the motor
shaft. The memory 101 stores the executable instructions for
controlling the functions of an appliance. The processor 102
executes the instructions stored in the memory 101. The memory 101
can either be external or internal to the processor. The processor
may comprise any type of processor including microcontroller or a
microprocessor. The processor 102 executes the instructions to
determine when an imbalance condition exists according to the
method shown in FIG. 3 and takes corrective action if a
sufficiently high imbalance or out of-balance (OOB) condition is
detected. The actions taken when a sufficiently high imbalance
condition is detected may include stopping the motor, attempts to
re-balance the clothes in the tub, or a reduction of the allowed
top speed.
[0025] FIG. 3 is a flow diagram showing a method for detecting a
load imbalance condition. The method includes selecting a parameter
that fluctuates due to load imbalance, in this example, voltage
amplitude which is required to maintain a constant speed. The
method further includes identifying parameter values in a
predetermined sample period 201 and determining a target parameter
value 202, which is the average of the parameter values in this
example. In one exemplary embodiment, the parameter measured is
voltage amplitude, required to maintain a constant speed, which is
measured at a fixed interval of time, (i.e. every 50 ms) of a
pre-determined sample period. The sample period represents the
predetermined sample period, the time during which the parameter
values are read. The parameter values are stored in a data buffer
of predetermined length in memory. If the buffer is full, return to
the beginning of the data buffer so the parameter data will
overwrite the oldest parameter data. The effect of this method is
that of a moving data window or moving sample period.
[0026] In one embodiment, the amplitude required to maintain the
current speed is calculated in the microprocessor software. The
software increases or decreases voltage amplitude according to
input from a speed sensor 103 to maintain a constant speed. The
speed sensor 103 may be employed to detect speed fluctuations of
the motor shaft 36.
[0027] The method further provides calculating a parameter spread
of the parameter values described above 203. The parameter spread
is calculated whenever the buffer window is full of parameter
values, for example or in another embodiment, whenever a total
number of parameter values is reached over a given sample period.
Also, several sample periods may be taken over time, which
constitutes a moving sample period. In one embodiment of the
invention, the parameter spread comprises an average deviation
based on the difference between the average of the parameter values
in the sample period and a particular parameter value, although
other methods of determining parameter spread may be used.
[0028] In accordance with the present embodiment, the processor 102
compares individual parameter values to a the target parameter
value to get an average deviation of the parameter spread as shown
below:
i = 1 N X i - X N ##EQU00001##
[0029] The parameter spread shown by the equation above requires
calculating the average (X) of the total number of parameter values
from the sample period, summing the absolute value of each
parameter value (X.sub.i), which can be a real-time reading of the
fluctuating parameter, minus the average (X), and dividing the sum
by a predetermined number of values. The processor can calculate
the average parameter error by retrieving the parameter value data
from memory at predetermined intervals.
[0030] Furthermore, the parameter spread may be converted to an
actual weight value (Lbs or Kg) 204 that can be used to determine
the existence of an imbalance condition 205 by the following
equation:
OOB Lbs=Parameter Spread/Load Constant
[0031] Wherein the load constant is calculated by applying a
predetermined linear equation to the current load size in the
washing machine tub. The current load size can be determined in
various ways as determined by one of ordinary skill in the art, and
stored in memory as a weight value (lbs or kg). The slope and
offset comprise predetermined values that are constants calibrated
using known or predetermined imbalance loads.
Load Constant=(Load Size) (Slope)+Offset
[0032] An example of calibration includes calculating the average
deviation for a chosen parameter for each known imbalance load,
which is a known actual imbalance that has a weight value (lbs or
kg). When voltage is the measured parameter, the voltage deviation
is measured as an A/D value, where 1 VDC=2.0277 A/D units.
[0033] In practical embodiments the load constant may be determined
through empirical data that may stored in tabular format in the
memory 101. To accomplish this, the load constant may be generated
through the use of empirical data such as that provided in FIG. 4
utilizing the following equation wherein the parameter spread is
the average deviation as provided in FIG. 4.
Load Constant=Parameter Spread/Actual OOB
[0034] When voltage amplitude is the measured parameter, the
equation for the load constant can be modified as shown below:
Load Constant=Parameter Spread*Speed/Actual OOB
[0035] The modification to the equation includes multiplying the
parameter spread by the speed of the motor in order to normalize
the voltage amplitude spread. The modification to the equation
above is not required, although desirable due to the drop in
amplitude spread as speed increases. If the amplitude spread is
multiplied by the speed, the resulting load constant curve is
flatter and provides an improved imbalance calculation. In the
current implementation, the OOB calculation is optimized between 90
basket RPM (or plaster speed) and about 150 basket RPM. This range
may vary slightly based on machine dynamics.
[0036] Referring now to FIG. 5, a linear graph of the data from the
table of FIG. 4 showing slope 300 gives the equation:
Load Constant=-7.2623*Load Size+152.46
[0037] Wherein the load size is the actual weight of the clothes in
the vessel.
[0038] The imbalance weight value (OOB Lbs) can be determined by
the using the equation:
OOB=Parameter Spread/Load Constant
[0039] An imbalance condition will be detected when the OOB value
is above a predetermined value.
[0040] The particular embodiments of the invention described above
are merely illustrative as the invention may be practiced in
different but equivalent manners apparent to those skilled in the
art. Similarly, the protection sought is to be found in the claims
and is not to be limited by the descriptions of the embodiments
above. Therefore, the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope of the invention.
* * * * *