U.S. patent application number 12/829091 was filed with the patent office on 2011-06-30 for velocity feedback control system for a rotor of a toy helicopter.
This patent application is currently assigned to Spin Master Ltd.. Invention is credited to Paul Mak.
Application Number | 20110155844 12/829091 |
Document ID | / |
Family ID | 44186240 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155844 |
Kind Code |
A1 |
Mak; Paul |
June 30, 2011 |
Velocity Feedback Control System for a Rotor of a Toy
Helicopter
Abstract
There is provided a method and apparatus for controlling a toy
helicopter in flight. The toy helicopter is powered by a first
rotor and a second rotor. A target speed ratio is determined for
the speed of the first rotor and the speed of the second rotor. The
speed of the rotors is adjusted incrementally until the target
ratio is achieved
Inventors: |
Mak; Paul; (Kowloon,
CN) |
Assignee: |
Spin Master Ltd.
|
Family ID: |
44186240 |
Appl. No.: |
12/829091 |
Filed: |
July 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12785079 |
May 21, 2010 |
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12829091 |
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12647129 |
Dec 24, 2009 |
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12785079 |
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Current U.S.
Class: |
244/17.13 ;
701/3 |
Current CPC
Class: |
G05D 1/0858
20130101 |
Class at
Publication: |
244/17.13 ;
701/3 |
International
Class: |
B64C 27/57 20060101
B64C027/57; G05D 1/00 20060101 G05D001/00 |
Claims
1. A method for controlling a toy helicopter, the helicopter having
a first rotor and a second rotor, the first rotor being driven by a
first motor, and the second rotor being driven by a second motor,
power being provided to the first motor and the second motor using
pulse width modulation; the first rotor having a first rotor speed
and the second rotor having a second rotor speed, the first rotor
speed and the second rotor speed being adjusted such that the
helicopter is stable in flight, the ratio of the adjusted first
rotor speed to the adjusted second rotor speed defining a target
ratio; the method comprising the steps of: (a) measuring the first
rotor speed, measuring the second rotor speed and determining a
ratio of the first rotor speed to the second rotor speed; (b) if
the ratio is greater than the target ratio, performing at least one
of decreasing the power to the first rotor by a fixed increment and
increasing the power to the second rotor by a fixed increment; (c)
if the ratio is less than the target ratio, performing at least one
of increasing the power to the first rotor by a fixed increment and
decreasing the power to the second rotor by a fixed increment; and
(d) repeating steps (a) to (c) until the ratio and the target ratio
are within a predetermined margin; wherein measuring the first
rotor speed comprises measuring a feedback voltage of the first
motor and measuring the second rotor speed comprises measuring a
feedback voltage of the second motor.
2. The method according to claim 1, wherein one of the first rotor
and the second rotor is a tail rotor.
3. The method according to claim 1, wherein the second rotor is
coaxial with the first rotor.
4. The method according to claim 1, wherein the target ratio is
determined by a trim position.
5. The method according to claim 1, the method further comprising
the steps of: (e) reading a throttle position; (f) determining a
target rotor speed for at least one of the first rotor and the
second rotor based on the throttle position; (g) measuring the
speed of the at least one of the first rotor and the second rotor;
(h) if the speed of the at least one of the first rotor and the
second rotor is greater than the target rotor speed, decreasing the
power to the at least one of the first rotor and the second rotor
by a fixed increment; (i) if the speed of the at least one of the
first rotor and the second rotor is less than the target rotor
speed, increasing the power to the at least one of the first rotor
and the second rotor by a fixed increment; (j) repeating steps (a)
to (c) and (g) to (i), until the speed of the at least one of the
first rotor and the second rotor and the target motor speed are
within a first predetermined margin, and the ratio and the target
ratio are within a second predetermined margin.
6. The method of claim 5, wherein the step of reading a throttle
position comprises receiving a wireless command, wherein the
wireless command specifies the throttle position.
7. The method according to claim 1, the method further comprising
the steps of: (e) reading a steering position; (f) determining a
new target ratio based on the steering position; and (g) repeating
steps (a) to (c), until the ratio and the new target ratio are
within a predetermined margin.
8. The method according to claim 7, wherein the step of determining
the new target ratio comprises using a relationship associated with
the steering position.
9. The method according to claim 8 wherein the relationship is
represented by a lookup table.
10. A toy helicopter comprising: a first rotor powered by a first
motor; a second rotor powered by a second motor; a power source to
provide power to the first rotor and the second rotor; and a
microprocessor configured to perform the method of claim 1.
Description
RELATED APPLICATION
[0001] This application claims the benefit of, priority to, relates
to the disclosure of, and is a Continuation of application Ser. No.
12/785,079 entitled VELOCITY FEEDBACK CONTROL SYSTEM FOR A ROTOR OF
A TOY HELICOPTER filed May 21, 2010 which is a Continuation of
application Ser. No. 12/647,129 entitled VELOCITY FEEDBACK CONTROL
SYSTEM FOR A ROTOR OF A TOY HELICOPTER filed Dec. 24, 2009. The
contents of these applications are incorporated by reference
herein.
BACKGROUND
[0002] The present invention relates to toy helicopters. In
particular, the present invention relates to a method and device
for improving the controllability and stability of toy
helicopters.
[0003] Toy helicopters, just like real helicopters, get lift from a
rotor, spinning in a horizontal plane above the helicopter's main
body. However, the spinning of the rotor causes torque to be
applied on the helicopter, which makes it very difficult to
maintain the helicopter in a forward-facing position.
[0004] Some helicopters solve this problem by having two coaxial
rotors, each spinning in a direction opposite that of the other. As
each of the two rotors creates a torque which counteract each
other, the helicopter remains stable.
[0005] Another way to counteract the torque produced by the rotor
is to add a tail rotor, which spins in a vertical plane. The force
produced by such a tail rotor is designed to be in an opposite
direction to the torque produced by the horizontal rotor, such that
the helicopter remains stable.
[0006] However, as will be appreciated by people skilled in the
art, the above solution requires that the rotors be precisely
calibrated, since if too much or too little power is given to one
of the rotors, the helicopter will be difficult to maneuver. In toy
helicopters, this particularly creates problems in two situations:
(1) when the helicopter's battery loses power, and (2) when the
power to the rotor is increased or decreased suddenly.
[0007] Therefore, the present device and method provide a solution
to the above problem. Specifically, the present device and method
use software to ensure the amount of power provided to a second
rotor is calibrated precisely to counteract the torque created by a
first rotor.
[0008] There is further provided a device and method to precisely
set the speed of a rotor according to a throttle position.
[0009] There is further provided a device and method to steer a toy
helicopter by adjusting the power level of a first rotor and a
second rotor.
SUMMARY
[0010] The present device and method provide greater stability and
maneuverability to a toy helicopter by ensuring that the amount of
power provided to the rotors will produce the correct amount of
torque according to user commands.
[0011] According to at least one embodiment of the present
invention, there is provided a method for controlling a helicopter,
the helicopter having a plurality of rotors, each rotor having a
rotor speed and a target rotor speed, the method comprising the
steps of: (a) measuring the rotor speed of at least one of the
plurality of rotors; (b) if the rotor speed of the at least one of
the plurality of rotors is greater than the target rotor speed for
the at least one of the plurality of rotors, decreasing the power
to the at least one of the plurality of rotors by a fixed
increment; (c) if the rotor speed of the at least one of the
plurality of rotors is less than the target rotor speed for the at
least one of the plurality of rotors, increasing the power to the
at least one of the plurality of rotors by a fixed increment; and
(d) repeating steps (a) to (c) until the rotor speed of the at
least one of the plurality of rotors and the target rotor speed for
the at least one of the plurality of rotors are within a
predetermined margin.
[0012] According to at least one embodiment of the present
invention, there is provided a method for controlling a helicopter,
the helicopter having a first rotor and a second rotor, the method
comprising the steps of (a) measuring the speed of the first rotor;
(b) determining the target second rotor speed based on the speed of
the first rotor; (c) measuring the speed of the second rotor; (d)
if the speed of the second rotor is greater than the target second
rotor speed, decreasing the power to the second rotor by a fixed
increment; (e) if the speed of the second rotor is less than the
target second rotor speed, increasing the power to the second rotor
by a fixed increment; and (f) repeating steps (c) to (e) until the
speed of the second rotor and the target second rotor speed are
within a predetermined margin.
[0013] According to at least one embodiment of the present
invention, there is provided a method for controlling a helicopter,
the helicopter having a rotor, the method comprising the steps of:
(a) reading a throttle position; (b) determining the target rotor
speed based on the throttle position; (c) measuring the speed of
the rotor; (d) if the speed of the rotor is greater than the target
rotor speed, decreasing the power to the rotor by a fixed
increment; (e) if the speed of the rotor is less than the target
rotor speed, increasing the power to the rotor by a fixed
increment; and (f) repeating steps (c) to (e) until the speed of
the rotor and the target rotor speed are within a predetermined
margin.
[0014] According to at least one embodiment of the present
invention, there is provided a method of steering a helicopter, the
helicopter having a first rotor and a second rotor, the method
comprising the steps of: (a) reading a steering position; (b)
measuring a first rotor speed; (c) determining a target second
rotor speed based on the first rotor speed and the steering
position; (d) measuring the second rotor speed; (e) if the second
rotor speed is greater than the target second rotor speed,
decreasing the power to the second rotor by a fixed increment; (f)
if the second rotor speed is less than the target second rotor
speed, increasing the power to the second rotor by a fixed
increment; and (g) repeating steps (d) to (f) until the second
rotor speed and the target second rotor speed are within a
predetermined margin.
[0015] According to at least one embodiment of the present
invention, there is provided a method for controlling a helicopter,
the helicopter having a first rotor and a second rotor, the first
rotor having a first rotor speed and the second rotor having a
second rotor speed, the first rotor speed and the second rotor
speed being adjusted such that the helicopter is stable in flight,
the ratio of the adjusted first rotor speed to the adjusted second
rotor speed defining a target ratio; the method comprising the
steps of (a) measuring the ratio of the first rotor speed to the
second rotor speed; (b) if the ratio is greater than the target
ratio, performing at least one of decreasing the power to the first
rotor by a fixed increment and increasing the power to the second
rotor by a fixed increment; (c) if the ratio is less than the
target ratio, performing at least one of increasing the power to
the first rotor by a fixed increment and decreasing the power to
the second rotor by a fixed increment; and (d) repeating steps (a)
to (c) until the ratio and the target ratio are within a
predetermined margin.
[0016] According to at least another embodiment of the present
invention, there is provided a helicopter comprising: a first rotor
powered by a first motor; a second rotor powered by a second motor;
a power source to provide power to the first rotor and the second
rotor; and a microprocessor configured to perform any of the above
methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a side view of a helicopter according to one
embodiment of the present invention.
[0018] FIG. 2 is a flow chart of a method according to one
embodiment of the present invention.
[0019] FIG. 3a shows a symbolic representation of power delivered
to a motor using pulse width modulation.
[0020] FIG. 3b shows a symbolic representation of power delivered
to a motor using pulse width modulation.
[0021] FIG. 4 is a flow chart of a method according to one
embodiment of the present invention.
[0022] FIG. 5 is a block diagram of the electronic components of a
helicopter according to one embodiment of the present
invention.
DETAILED DESCRIPTION
[0023] Reference is made to FIG. 1. FIG. 1 shows a helicopter 60
having a cockpit 61, landing gear 62, a first rotor 63 and a second
rotor 64. It also includes a first motor to drive the first rotor
63, a second motor to drive the second rotor 64, and a power source
to power both motors. A microprocessor controls the level of power
provided to each motor. As the first and second motors receive
power, rotors 63 and 64 rotate at a speed which depends on the
level of power received. There is a tail rotor 100.
[0024] In at least one embodiment, the power that drives the motors
is adjusted using Pulse Width Modulation (PWM). Reference is now
made to FIGS. 3a and 3b, which illustrate how PWM is used to
provide different amounts of power.
[0025] FIG. 3a shows a graph where voltage (V) is plotted against
time (t). Power is provided for a period x and then turned off for
a period x'. In this example, the periods x and x' are essentially
equal, and therefore power is provided, on average, for half of the
time.
[0026] FIG. 3b shows another graph where voltage (V) is plotted
against time (t). In this example however, the period x during
which power is provided has been reduced in relation to the period
x' during which power is turned off, and power is provided, on
average, for a third of the time.
[0027] Thus the graphs of FIG. 3a and FIG. 3b show how PWM can be
used to adjust very finely the amount of power provided to an
electric motor. As will be understood by those skilled in the art,
what is most important in PWM is not the specific periods x and x'
but rather the proportion of x in relation to x'.
[0028] Therefore, in the at least one embodiment wherein power is
adjusted using PWM, the power level could be one of N power levels.
Although those skilled in the art could readily understand how this
can be done, the following example is provided for illustrative
purposes.
[0029] The period T is defined as follows:
T=x+x' Equation 1
[0030] If there are N power levels, each separated by an increment
of .lamda., the increment .lamda. must be computed by the following
equation:
.lamda. = T N - 1 Equation 2 ##EQU00001##
[0031] The values for x and x' for a power level i, where i is
between 0 and (N-1) are computed as follows:
x=i.lamda. Equation 3
x'=[N-(i+1)].lamda. Equation 4
[0032] Thus, for 16 power levels (N=16) and a period T=30
milliseconds, the values of x and x' for a given power level i are
computed as per the table below.
TABLE-US-00001 i x x' 0 0 30 1 2 28 2 4 26 3 6 24 4 8 22 5 10 20 6
12 18 7 14 16 8 16 14 9 18 12 10 20 10 11 22 8 12 24 6 13 26 4 14
28 2 15 30 0
[0033] It will be appreciated however, that the above example is
provided for illustrative purposes only and is not limiting.
[0034] It will also be appreciated by those skilled in the art that
in at least some embodiments, a motor may require at least a
certain threshold of power before operating, such that, for
example, the minimum pulse width required is achieved when i has a
value n which is greater than 1 but less than N. The specific value
n will depend on the particular characteristics of the motor and
can be readily determined by the skilled person. In such a case,
the above table may be adjusted so that power levels corresponding
to i=1 . . . n would be discarded.
[0035] In at least one embodiment, the power is provided to the
first motor and the second motor using PWM as shown in the example
above. In such an embodiment, the step of adjusting the power to
the second motor incrementally is performed by increasing or
decreasing the variable i by 1, and recalculating the values of x
and x' accordingly.
[0036] As will be appreciated by those skilled in the art, using
PWM also allows measurement of the rotational speed of a rotor by
measuring the feedback voltage of the motor which drives the rotor.
When no power is provided to the motor (i.e., during the period
corresponding to x' in FIGS. 3a and 3b), the motor acts like a
generator and generates a feedback voltage dependent upon the
rotation speed of the associated rotor, making it possible to use
the feedback voltage produced by the motor as a proxy for the speed
of the rotor driven by the motor.
[0037] The power received by the first and second motors, and
therefore, the rotational speed of the rotors powered by the first
and second motors, is monitored, according to at least one
embodiment, by measuring the feedback voltage produced by the
motors. In particular, in at least one embodiment, the feedback
voltage of the first motor is measured as a proxy for the
rotational speed of the first rotor, and the measurement is used to
determine what the rotational speed of the second rotor, and the
feedback voltage of the second motor, should be to achieve
stability.
[0038] In at least one embodiment, the feedback voltage of the
motors is measured by a circuit or a microprocessor.
[0039] The relationship between the first motor feedback voltage
and the second motor feedback voltage required to achieve a stable
flight depends on a number of factors, including but not limited
to, the number of blades on each rotor and the dimension of these
blades. Therefore, there is no unique rule which is applicable to
each helicopter, however, it is within the purview of a person
skilled in the art to determine that relationship by simple
experimentation.
[0040] Based on the relationship between the first motor feedback
voltage and the target second motor feedback voltage, the target
second motor feedback voltage is computed and compared to the
measured second motor feedback voltage. It will be appreciated by
those skilled in the art that these steps are preferably performed
by a microprocessor running software.
[0041] If the measured second motor feedback voltage is equal to,
or within an acceptable margin of error of, the target second motor
feedback voltage, the method ends and is repeated when new
measurements are performed. On the other hand, if the values
diverge by more than an acceptable margin, the power to the second
rotor is adjusted incrementally.
[0042] Reference is now made to FIG. 2 which shows a flow diagram
of the method according to at least one embodiment of the present
invention.
[0043] The method starts at step 210 where the first rotor's speed
is measured. As will be appreciated by those skilled in the art, it
is not necessary that the actual rotational speed of the rotor be
measured. As per the above, the speed may be measured using a proxy
value such as the motor's feedback voltage.
[0044] At step 220, the first rotor's speed measured in step 210 is
used to compute the target second rotor speed. As with step 210, in
some embodiments, it may be simpler to compute a target proxy value
such as a target feedback voltage for the second motor. The
relationship between the first rotor's speed and the target second
rotor speed is typically determined by experimentation. In some
embodiments, the target second rotor speed may be computed as the
first rotor's speed multiplied by a factor a, as in the equation
below, where S.sub.target is the target second rotor speed and
S.sub.first is the first rotor speed.
S.sub.target=S.sub.first.times..alpha. Equation 5
[0045] It will be appreciated by one of skill in the art that other
mathematical relationships of varying complexity can exist between
the speed of the first rotor and the target speed of the second
rotor and that it is within the ability of the skilled person to
determine such mathematical relationships.
[0046] In another embodiment, a look-up table can be created and
stored in memory, where the first rotor speed is used as an index
to find a target second rotor speed.
[0047] It should be appreciated by those skilled in the art that
the above examples are provided for illustrative purposes only and
are not intended to be limiting.
[0048] At step 230, the actual second rotor speed is measured, and
at step 240 the second rotor speed is compared to the target second
rotor speed. It will be appreciated by those skilled in the art
that for the comparison to be meaningful, both values should be in
the same units. Therefore, if the actual speed is measured in
revolutions per minute (RPM), the target second rotor speed should
also be in revolutions per minute. Similarly, if the measured speed
is measured as a feedback voltage, the target speed should also be
expressed as a feedback voltage.
[0049] If, at step 240, it is found that the actual speed is less
than the target speed, the second rotor speed is increased
incrementally, using PWM as discussed above or by other means known
in the art. Similarly, if the actual speed is more than the target
speed, the second rotor speed is decreased incrementally, using PWM
as discussed above or by other means known in the art. In both
cases, the method returns to step 230 where the actual speed is
measured once again.
[0050] If however the actual speed is equal to the target speed, or
if the two speeds are within an acceptable margin of error of each
other, the method ends at step 270. What is an acceptable margin of
error will depend on a host of factors, however it is within the
purview of the skilled person to determine that experimentally.
[0051] The skilled person will appreciate that it is possible to
adjust the speed of either rotor or of both rotors simultaneously,
by adjusting the power to the respective motors, in order to
maintain the rotor speeds within the desired mathematical
relationship. For example, if the second rotor speed is higher than
is required to maintain the required mathematical relationship with
the first rotor speed, either the power can be decreased to the
second motor, or the power can be increased to the first motor, or
the power of both motors can be adjusted simultaneously, until the
second rotor speed and first rotor speed achieve the desired
relationship.
[0052] The present method and device also provide for setting the
rotor speed according to a user-controlled throttle, such as, for
example, on a remote control device which is used to control the
helicopter's flight. As is known in the art, the throttle controls
the amount of power delivered to the helicopter's rotor.
[0053] The present method can be used to ensure that the actual
power delivered to a first rotor is appropriate based on the
throttle position, and to adjust a second rotor's power
accordingly. Such a method is shown in FIG. 4.
[0054] As shown in FIG. 4, the method starts at step 510 where the
throttle position is determined. This step may be performed by the
processor inside the helicopter, and could consist of receiving a
command from the remote control device notifying the helicopter
that the throttle has been moved to a new level. Other means of
performing this step may be known in the art and the above is not
intended to be limiting.
[0055] At step 520, the throttle level is used to determine the
target rotor speed. As will be appreciated by those skilled in the
art, the relationship between the throttle level and the rotor
speed is readily established.
[0056] At step 530, the rotor speed is measured. As in the case of
the method shown in FIG. 2, measuring the rotor speed may consist
in measuring a proxy value, like the motor's feedback voltage.
[0057] At step 540, the rotor speed is compared to the target rotor
speed. If the actual speed is less than the target speed, the rotor
speed is increased incrementally at step 550. If the actual speed
is more than the target speed, the rotor speed is decreased
incrementally at step 560. In at least one embodiment, the rotor
speed is increased or decreased by adjusting the parameters of
PWM.
[0058] If the actual speed is equal to the target speed, or if the
actual speed and the target speed are within an acceptable margin
of each other, the method ends at step 570. The method is repeated
the next time the throttle is moved to a new level.
[0059] It will be appreciated by those skilled in the art that the
methods of FIG. 4 and of FIG. 2 may be combined, so that as a first
rotor's speed is adjusted to correspond to the throttle position,
the second rotor's speed is adjusted to provide a stable flight at
the first rotor's adjusted speed. In at least one embodiment of
this combined method, the method of FIG. 2 is performed every time
the method of FIG. 4 increases or decreases the first rotor's
speed.
[0060] The skilled person will appreciate that in at least one
embodiment, the method according to the present invention can
involve adjusting the ratio between the speeds of the first rotor
and the second rotor. It is therefore contemplated that the speeds
of both the first rotor and second rotor can be modified
simultaneously so as to adjust this ratio, for example, by using
PWM as described above. For example, the ratio of the first rotor
speed to the second rotor speed is too high, the helicopter can be
controlled by simultaneously and incrementally increasing the power
to the second rotor and decreasing the power to the first rotor
until the desired ratio of the first rotor speed to the second
rotor speed has been established. Conversely, if the ratio of the
first rotor speed to the second rotor speed is too low, the
helicopter can be controlled by simultaneously and incrementally
increasing the power to the first rotor and decreasing the power to
the second rotor until the desired ratio of the first rotor speed
to the second rotor speed has been achieved.
[0061] In at least one embodiment, the present method may be used
on a helicopter with first and second rotors being co-axial rotors,
as shown in FIG. 1. In at least one embodiment, the present method
may also be used on a helicopter with first and second rotors being
a main horizontal rotor and a tail rotor. In at least one
embodiment, the first rotor is a main horizontal rotor and the
second rotor is a tail rotor.
[0062] Typically, a helicopter with two coaxial rotors will be
stable (i.e., the torque produced by both rotors will
counterbalance each other) if both rotors are of the same
dimensions and they rotate at the same speed in opposite
directions. In such a case, the present method could be used to
ensure that the speed of both rotors is the same. For example, the
present method could be implemented with .alpha.=1 (as in Equation
5 above).
[0063] In some cases however, the desired ratio between the speed
of both rotors may not be 1, for example if the dimensions of the
rotors are different from each other.
[0064] In at least one embodiment, the present method may also be
used for performing yawing motions, either on a helicopter with
co-axial rotors or on a helicopter with a tail rotor. In
particular, this can be done by adjusting the relationship between
the first rotor speed and the target second rotor speed.
[0065] As will be appreciated by those skilled in the art, in the
above examples, the method's objective is to cancel out the torque
from the first rotor with the torque from a second rotor, so that
the helicopter could fly in a straight line. If however it is
desired, not to fly in a straight line, but to perform yawing
motions, the torque of either motor can be harnessed to that
effect.
[0066] Steering of a helicopter can be controlled by a remote
control device which includes a left and right steering control. It
will be appreciated by those skilled in the art, that when the
steering control is in a neutral position, the present method
should be performed as described above. When the steering control
is moved in a position indicating that the helicopter should steer
left or right, the present method should be performed to ensure the
ratio between the first rotor speed and the second rotor speed
creates a net torque which directs the helicopter's flight
according to the steering control's position.
[0067] In at least one embodiment, the steering control has 7
discrete positions. Each position corresponds to a relationship
between the speed of the first rotor and the second rotor. The
following table is provided to illustrate how this can be achieved,
however, it is not intended to be limiting.
TABLE-US-00002 Steering position .alpha. Neutral 1 Left-1 0.9
Left-2 0.8 Left-3 0.7 Right-1 1.1 Right-2 1.2 Right-3 1.3
[0068] In the above table, the neutral position corresponds to an
.alpha. value of 1, meaning that for the helicopter to travel in a
straight line, both the first rotor and second rotor should rotate
at the same speed. The steering position Left-1 means that the
helicopter should be turning slightly left, and therefore the
.alpha. value is 0.9, which means that the second rotor speed
should be 90% of the first rotor's speed. As would be appreciated
by those skilled in the art, this implies that the resulting torque
when the second rotor rotates at 90% of the first rotor's speed
makes the helicopter turn left.
[0069] Similarly, the steering position Left-2 corresponds to a
more pronounced steering to the left and this is achieved by having
the second rotor speed at 80% of the first rotor's speed, or an
.alpha. of 0.8.
[0070] As will be appreciated by those skilled in the art, the
relationship between the steering position, the first rotor speed,
and the second rotor speed may not be as simple as depicted above.
In particular it may not necessarily be expressed in terms of a
single factor .alpha.. The applicable values for a given helicopter
may be readily determined experimentally by the person of skill in
the art, and in the case when no clear mathematical relationship
between these values can be established, a lookup table might be
the most efficient way of computing the correct values.
[0071] In at least one embodiment, the remote control of the
helicopter further includes a trim knob. In this embodiment, the
trim knob is used to adjust the relationship between the speeds of
each rotor. Therefore, once the helicopter is flying, the user can
adjust the trim knob until the helicopter's flight is stable. In
particular, as the trim knob is adjusted, one rotor's speed is
increased by an increment and the other rotor's speed is decreased
by the same increment, thereby maintaining a constant thrust acting
on the helicopter. The ratio between the two rotor speeds following
an adjustment of the trim knob is then stored as a target ratio and
maintained, using the methods described above, until the trim knob
is adjusted again. The skilled person will appreciate that, while a
trim knob is specifically described, any means of controlling the
trim is contemplated as forming part of the present invention.
[0072] Reference is now made to FIG. 5, which shows a block diagram
of the helicopter's internal circuitry according to at least one
embodiment.
[0073] The microprocessor control unit (MCU) 70 is shown as having
a decoding module 72, an arithmetic and logic unit (ALU) 73, a
first motor control 74, and a second motor control 75. It will be
appreciated by those skilled in the art that the ALU 73 is an
important hardware component of microprocessors which is used to
perform arithmetic and logical operations. The decoding module 72,
the first motor control 74 and the second motor control 75 can be
implemented as software modules or as individual circuits, as is
known in the art. Also shown in FIG. 5 are the infrared (IR) module
71, the first motor 76 and the second motor 77.
[0074] During operation, the IR module 71 receives commands from a
remote control device (not shown). These commands are decoded by
the decoding module 72, processed by the ALU 73, where the commands
are interpreted and the desired speed for both the first rotor and
second motor are computed according to the present disclosure.
[0075] The ALU then notifies the first motor control 74 of the
desired speed. The first motor control 74 adjusts the first motor
76's speed as described above and receives feedback voltage
information from the first motor 76.
[0076] Based on the feedback information received from the first
motor 76, the ALU also notifies the second motor control 75 of the
desired speed for the second motor. The second motor control then
adjusts the second motor 77's speed as described above and receives
feedback voltage information from the second motor 77.
[0077] The embodiments of the present invention described herein
are intended to be non-limiting. Various modifications which are
readily apparent to the person of skill in the art are intended to
be within the scope of the invention, the only limitations to which
are set forth in the appended claims.
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