Title: Direction control device of control target
Abstract: The left and right rear drive wheels of a vehicle are controlled independently, and the traveling direction of the vehicle is changed by providing a rotational speed difference between each of the left and right rear drive wheel. A vehicle operator merely designates the turning direction by moving an operation stick, e.g., to the left or right, which will in turn enable an automatic turn at an optimum curvature to be performed which frees the vehicle operator from complicated steering operations. A highly precise and responsive turn is achieved when the left and right independent control is implemented with a PLL control circuit.
Patent Number: 6,988,570 Issued on 01/24/2006 to Takeuchi
| Inventors:
|
Takeuchi; Kesatoshi (Suwa, JP)
|
| Assignee:
|
Seiko Epson Corporation (Tokyo, JP)
|
| Appl. No.:
|
126961 |
| Filed:
|
April 22, 2002 |
Foreign Application Priority Data
| Apr 20, 2001[JP] | 2001-123411 |
| Apr 20, 2001[JP] | 2001-123412 |
| Current U.S. Class: |
180/6.48; 180/6.5; 318/432 |
| Current Intern'l Class: |
B62D 11/02 (20060101) |
| Field of Search: |
180/624,65,411,626,628,648
318/432-434,437,34,41,53,66,85,489,911
|
References Cited [Referenced By]
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| 4577140 | Mar., 1986 | Schmidt et al.
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| 4774518 | Sep., 1988 | Fukuhara.
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| 4817000 | Mar., 1989 | Eberhardt.
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| 4825132 | Apr., 1989 | Gritter.
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| 4900992 | Feb., 1990 | Sekizawa et al.
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| 5222568 | Jun., 1993 | Higasa et al.
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| 5258912 | Nov., 1993 | Ghoneim et al.
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| 5345155 | Sep., 1994 | Masaki et al.
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| 5379223 | Jan., 1995 | Asplund.
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| 5456332 | Oct., 1995 | Borenstein.
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| 5469928 | Nov., 1995 | Adler et al.
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| 5481460 | Jan., 1996 | Masaki et al.
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| 5487437 | Jan., 1996 | Avitan.
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| 5624004 | Apr., 1997 | Watanabe.
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| 5699873 | Dec., 1997 | Moriya et al.
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| 5701066 | Dec., 1997 | Matsuura et al.
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| 5921338 | Jul., 1999 | Edmondson.
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| 5973463 | Oct., 1999 | Okuda et al.
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| 6192304 | Feb., 2001 | Goetz.
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| 6353408 | Mar., 2002 | Whight.
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| 6360163 | Mar., 2002 | Cho et al.
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| 6539329 | Mar., 2003 | Kato et al.
| |
| Foreign Patent Documents |
| 1-308106 | Dec., 1989 | JP.
| |
| 2-262806 | Oct., 1990 | JP.
| |
| 5-176418 | Jul., 1993 | JP.
| |
| 5-328542 | Dec., 1993 | JP.
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| 8-19110 | Jan., 1996 | JP.
| |
| 2001-28804 | Jan., 2001 | JP.
| |
| 2001-47887 | Feb., 2001 | JP.
| |
Other References
International Search Report, May 28, 2002.
|
Primary Examiner: Morris; Lesley D.
Assistant Examiner: Lum; L.
Attorney, Agent or Firm: Nixon Peabody LLP
Claims
What is claimed is:
1. A direction control device capable of controlling a direction of a control
target including a plurality of driving means by individually controlling said
driving means, comprising:
a drive control means for controlling a drive of respective drive means;
a target direction commanding means for commanding a target direction for a movement
of said control target; and
a drive characteristic difference setting means for setting a drive characteristic
difference in work speed between the respective driving means such that the direction
of said control target is controlled in said target direction:
wherein said drive control means controls the drive of each of said driving means
in accordance with said drive characteristic difference in work speed and comprises
a control circuit adapted to control feedback to each of said driving means such
that a drive characteristic difference detection result will become a set value
as said drive characteristic and wherein said control circuit comprises a PLL control
circuit which controls each of said driving means based on a phase difference of
a reference signal frequency and a drive state detection signal frequency of said
driving means and wherein said control circuit sets said phase difference initially
based on said drive characteristic set.
2. A direction control device for a vehicle including an electric motor for individually
rotationally driving each of a plurality of drive wheels between stationary, current
direction and target direction drive modes, and which is capable of controlling
a vehicle direction by providing a rotation difference between each of the respective
drive wheels based on a steering state of a steering means, comprising:
a drive control means capable of controlling the a drive of each of said electric
motors;
a target direction commanding means for commanding a target direction of said
vehicle based on a steering state of said steering means;
an electric motor characteristic difference setting means for setting a rotational
status of the respective electric motors, the rotational status indicative of a
rotation difference in each of the drive wheels; and
a detection means for detecting an actual rotational status of each of the electric
motors;
wherein said drive control means controls the drive of each electric motor of
each drive wheel as a function of a set rotational status and the detected rotational
status of each of said electric motors, and controls an advancing direction of
the vehicle toward the target direction by providing a rotational difference to
each of said drive wheels based upon the steering state.
3. A direction control device according to claim 2, wherein said drive control
means comprises a PLL control circuit which controls the electric motor of each
of said drive wheels based on a phase difference of a detected frequency signal
and a reference frequency signal wherein the reference frequency signal is derived
from a set rotational status for each electric motor of each drive wheel and a
detected frequency signal is derived from the detected rotational status for each
electric motor of each drive wheel.
4. A direction control device according to claim 3, wherein the PLL circuit is
provided with a division value which is altered with each change in drive state
of said vehicle, the drive state indicated by a difference between a reference
frequency signal determined from a target drive state and the detected frequency
signal detecting an actual drive state of the rotational driving means.
5. A direction control device according to claim 2, wherein said steering means
is a steering wheel, and said target direction commanding means sets the target
direction of said vehicle in accordance with the steering state of said steering wheel.
6. A direction control device according to claim 2, wherein said vehicle comprises
auxiliary front wheels which rotate in the direction of said vehicle without any
steerage or drive and which support the vehicle against a road surface; and said
drive control means further comprises a floatation control means for floating said
auxiliary wheels while said vehicle is moving forward and maintaining the floating
state of said auxiliary wheels while the vehicle is moving.
7. A vehicle comprising the direction control device according to claim 1.
8. An electric vehicle comprising a direction control device having an electric
motor for individually rotationally driving each of a plurality of drive wheels,
and which is capable of controlling a vehicle direction by providing a rotational
difference to the respective drive wheels based on a steering state of a steering
means, comprising:
a drive control means capable of controlling the driving of each electric motor;
a target direction commanding means for commanding a target direction of said
vehicle based on the steering state of said steering means;
a drive characteristics setting means for setting a drive state for each electric
motor for each drive wheel thereby providing the rotational difference in each
of said drive wheels such that a movement of said vehicle is controlled in said
target direction; and
a detection means for detecting a rotational status of the respective motors;
wherein said drive control means controls driving each electric motor of each
of said drive wheels as a function of a rotational status set value for each electric
motor and a detected rotational status value for each electric motor, where the
rotational status set value corresponds to a designated rotational speed pulse
signal from a pulse motor.
9. An electric vehicle according to claim 8, wherein said drive control means
comprises a PLL control circuit which controls the electric motor of a drive wheel
based on a phase difference between a reference frequency signal and a detected
frequency signal,
wherein the reference frequency signal is derived from the rotational status
set value and the detected frequency signal is derived from the detected rotational
status of each of said electric motors.
10. A steering control device of a vehicle having a plurality of wheels supporting
a vehicle body against a road surface for movement between a current traveling
direction and steerage direction, comprising:
a drive control means for individually controlling a drive for each wheel of
a pair of wheels positioned on a left and right side of said vehicle body and the
pair of wheels being selected from said plurality of wheels;
a steering angle setting means for setting a designated steering angle signal
of a frequency corresponding to a steerage direction of said vehicle;
a drive signal output control means for outputting a drive signal of a prescribed
frequency to each drive control means for performing independent drive control
for each drive of said pair of wheels based on the designated steering angle signal
of the steering angle setting means;
a steering angle detection means for detecting a current steering angle direction
utilizing the current traveling direction of said vehicle as a reference;
a signal converting means for converting a detected steering angle signal to
a frequency signal corresponding to the steering angle detected with said steering
angle detection means; and
a phase comparison means for comparing phases of the frequency signal corresponding
to the designated steering angle with said steering angle setting means and the
detected steering angle frequency signal obtained with said signal converting means;
wherein a drive signal is output to the drive of each of the respective wheels
from said drive control means to cause the vehicle to move toward the steerage
direction such that said phases will coincide based on a comparison result of said
phase comparison means.
11. A steering control device according to claim 10, wherein said phase comparison
means and drive control means each comprise a PLL circuit.
12. A steering control device according to claim 10, wherein the drive for said
pair of wheels is an electric motor.
13. A direction control device according to claim 3, wherein said vehicle comprises
auxiliary front wheels which rotate in the direction of said vehicle without any
steerage or drive and which support the vehicle against a road surface; and said
drive control means further comprises a floatation control means for floating said
auxiliary wheels while said vehicle is moving forward and maintaining a floating
state of said auxiliary wheels while the vehicle is moving.
14. A direction control device according to claim 4, wherein said vehicle comprises
auxiliary front wheels which rotate in the direction of said vehicle without any
steerage or drive and which support the vehicle against a road surface; and said
drive control means further comprises a floatation control means for floating said
auxiliary wheels while said vehicle is moving forward and maintaining a floating
state of said auxiliary wheels while the vehicle is moving.
15. A direction control device according to claim 5, wherein said vehicle comprises
auxiliary front wheels which rotate in the direction of said vehicle without any
steerage or drive and which support the vehicle against a road surface; and said
drive control means further comprises a floatation control means for floating said
auxiliary wheels while said vehicle is moving forward and maintaining a floating
state of said auxiliary wheels while the vehicle is moving.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a direction control device capable of altering
the motion of the control target having a plurality of driving means by independently
controlling the drive mechanism, and, for example, relates to a direction control
device of an electric vehicle of a two-wheel drive and which is capable of changing
directions based on the rotation difference of such drive wheels. As such drivers,
for example, there are electric traveling vehicles such as an electric car, electric
wheelchair, electric cart, and so on. The present invention may also be employed
in electric construction machinery, electric welfare equipment, electric robots,
electric toys, electric airplanes, and electric optical devices (camera, projector, etc.).
2. Background Art
In electric motor vehicles such as electric carts and electric cars, the vehicle
speed is adjusted by controlling the rotational speed of the electric motor for
driving the drive wheels. With current electric motor drive vehicles, when setting
the speed, the accelerator pedal or throttle lever is operated, the acceleration
is set based on the manipulated variable thereof, and, when the desired speed is
reached, the accelerator pedal is returned to a prescribed level in order to maintain
the speed.
Meanwhile, when steering the vehicle, it is standard that the passenger
steers the steering wheel. Conventionally, when taking an electric cart or electric
wheelchair as this type of electric vehicle, as the steering system thereof, there
are those which change the traveling direction of the vehicle by steering the steering
wheel or lever toward a prescribed direction to control the front wheels, and those
which change the traveling direction of the vehicle by providing a rotation difference
to the left and right rear wheels.
Nevertheless, with the front wheel steering type vehicles, a structure
is required for steering the front wheels. Moreover, with the vehicles employing
the steering method of providing a rotation difference to the left and right rear
wheels, there is an inconvenience in that the passenger is required to provide
a suitable rotation difference to the left and right rear wheels each time he/she
wishes to change the direction of the vehicle.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a direction control device which
does not require a structure for steering the front wheels, which is capable of
providing a rotation difference to the left and right drive wheels by the passenger
merely changing the steering device such as a handle or lever in a desired direction,
and, as a result, which enables the change in direction of the vehicle in a desired
direction. Another object of the present invention is to provide control technology
capable of quickly and accurately realizing the foregoing drive control of the
left and right drive wheels. Still another object of the present invention is to
provide a direction control device capable of applying a circular steering wheel
as the steering device. A further object of the present invention is to provide,
in an electric vehicle having front wheels as auxiliary wheels, control technology
in which added to the foregoing direction control device is a control mechanism
enabling the travel of an electric vehicle with such auxiliary wheels afloat while
such electric vehicle is running. A still further object of the present invention
is to provide an electric vehicle comprising the foregoing direction control device.
In order to achieve the foregoing objects, the present invention provides a direction
control device capable of controlling the direction of a control target having
a plurality of driving means by individually controlling the driving means, comprising:
drive control means for controlling the drive of the respective drive means; target
direction commanding means for commanding the target direction of the moving direction
of the control target; and drive characteristic difference setting means for setting
the drive characteristic difference to the respective driving means such that the
direction of the control target is controlled in the target direction; wherein
the drive control means controls the drive of each of the driving means in accordance
with the drive characteristic difference.
Another direction control device according to the present invention further
comprises drive characteristic difference detection means for detecting the drive
characteristic difference of the respective driving means, wherein the drive control
means comprises a control circuit for controlling the feedback of each of the driving
means such that the drive characteristic difference detection result will become
the drive characteristic difference set value.
The control circuit is a PLL control circuit which controls each of the driving
means based on the phase difference of the reference signal frequency and the drive
state detection signal frequency of the driving means.
The present invention also provides a direction control device having an electric
motor for rotationally driving a plurality of drive wheels individually, and which
is capable of controlling the vehicle direction by providing a rotation difference
to the respective drive wheels based on the steering state of the steering means,
comprising: drive control means capable of controlling the drive of each of the
electric motors; target direction commanding means for commanding the target direction
of the vehicle based on the steering state of the steering means; electric motor
characteristic difference setting means for setting the rotational status of the
respective electric motors providing the rotation difference in each of the drive
wheels; and detection means for detecting the rotational status of the respective
motors; wherein the drive control means controls the drive of the electric motor
of each of the drive wheels in accordance with the set rotational status and detected
rotational status of each of the electric motors, and is capable of controlling
the advancing direction of the vehicle by providing a rotation difference to each
of the drive wheels.
The drive control means comprises a PLL control circuit which controls the electric
motor of each of the drive wheels based on the phase difference of the detected
frequency signals pursuant to the reference frequency signal against the set rotational
status to the electric motor of each of the drive wheels and the detected rotational
status of the electric motor. The division value of the PLL circuit is altered
with the drive mode of the vehicle.
The steering means is a steering wheel, and the target direction setting means
sets the target direction of the vehicle in accordance with the steering state
of the steering wheel. The vehicle comprises an auxiliary wheel which rotates in
pursuit of the direction of the vehicle without any steerage or drive and supports
the vehicle against the road surface; and the direction control device comprising
floatation control means capable of floating the auxiliary wheel while the vehicle
is running and maintaining and controlling the floating state of the auxiliary
wheel against the road surface.
The present invention also provides a vehicle comprising the foregoing direction
control device, and which comprises this direction control device as the moving
direction control device as the control target.
The present invention also provides an electric vehicle comprising the direction
control device having an electric motor for rotationally driving a plurality of
drive wheels individually, and which is capable of controlling the vehicle direction
by providing a rotation difference to the respective drive wheels based on the
steering state of the steering means, comprising: drive control means capable of
controlling the drive of each of the electric motors; target direction commanding
means for commanding the target direction of the vehicle based on the steering
state of the steering means; drive characteristics setting means for setting the
drive state of the electric motor of each of the drive wheels for providing the
rotation difference in each of the drive wheels such that the direction of the
vehicle is controlled in the target direction; and detection means for detecting
the rotational status of the respective motors; wherein the drive control means
controls the drive of the electric motor of each of the drive wheels based on the
rotational status set value of the respective motors and the rotational status
detected value of the electric motor.
The drive control means comprises a PLL control circuit for controlling the electric
motor of each of the drive wheels based on the phase difference between reference
frequency signal pursuant to the set rotational status and the detected frequency
signal pursuant to the detected rotational status of each of the electric motors.
The present invention also provides a steering control device of a vehicle having
a plurality of wheels supporting the vehicle body against the road surface, comprising:
drive control means capable of individually controlling the drive of each wheel
of a pair of wheels provided to the left and right of the vehicle body among the
plurality of wheels; steering angle setting means for setting the frequency signal
corresponding to the steerage of the vehicle; drive signal output control means
for outputting the drive signal of a prescribed frequency for performing drive
control upon granting independence to each actuator of the wheels based on the
angle signal designated with the steering angle setting means; steering angle detection
means for detecting the angle of the current traveling direction with the direct
advancing state of the vehicle as the reference; signal converting means for converting
a signal to a frequency signal corresponding to the steering angle detected with
the steering angle detection means; and phase comparison unit for comparing the
phases of the frequency signal corresponding to the angle designated with the steering
angle setting means and the frequency signal obtained with the signal converting
means; wherein a drive signal is output to the drive mechanism of the respective
wheels from the drive control means toward a direction in which the phases will
coincide based on the comparison result of the phase comparison means.
The phase comparison means and drive control means comprise a PLL circuit. The
respective drive mechanisms of the wheels are electric motors.
The PLL (Phase Locked Loop) circuit is a feedback control circuit for synchronizing
the phases, and is used for controlling the output phase such that the signal having
a frequency of a pulse or AC signal becomes the same phase as the reference signal.
This technology is often used in spindle motors for rotating the hard disk of information
processing equipment, motors for rotating the VCR heads, motors for rotating the
polygon mirror for performing laser scans, and so on, and the target motor was
in most cases a stepping motor or the like. With the present invention, the rotational
speed of the motor can be controlled by performing inverter control even against
AC motors and DC motors to be driven under a constant voltage, and, by further
employing PLL technology, high-precision rotation angle control is enabled. Particularly,
for example, in a case when the load against the movement of the driven plate alters,
torque control becomes necessary. Nevertheless, by measuring the current speed
of the driven plate, speed control is enabled in a state of adding the torque load.
The present invention also provides a vehicle direction control method capable
of controlling the direction of a vehicle by controlling with a control circuit
the rotational driving for rotationally driving a plurality of drive wheels independently
and providing a rotation difference to the respective drive wheels in a rotational-drive
state; wherein the control circuit includes: a step of comparing the phase difference
between the reference frequency signal determined from the target drive state against
each of the drive wheels and the detected frequency signal detecting the drive
state of the drive wheels, and controlling the drive state of the rotational driving
means based on this phase difference.
The present invention also provides a vehicle direction control method capable
of controlling the direction of a vehicle by controlling with a control circuit
the rotational driving for rotationally driving a plurality of drive wheels independently
and providing a rotation difference to the respective drive wheels in a rotational-drive
state; wherein the control circuit includes: a step of seeking the target drive
state of each of the drive wheels based on the detection signal from the detection
means for detecting the operational status of the passenger; and a step of comparing
the phase difference between the reference frequency signal determined from the
target drive state against each of the drive wheels and the detected frequency
signal detecting the drive state of the drive wheels, and controlling the drive
state of the rotational driving means based on this phase difference.
The control circuit includes the step of outputting a drive signal to the respective
rotational driving means of each of the drive wheels based on the phase difference.
The control circuit is structured by including a PLL.
In the present invention, the drive control means or control circuit for driving
the rotational driving means such as an electric motor for performing drive control
to the respective drive wheels is structured by including PLL as described above.
Such drive control means or control circuit comprises a microcomputer, and performs
feedback control so as to coincide or converge the drive state of the respective
drive wheels with a desired drive state via the PLL circuit based on the processing
results of the microcomputer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural diagram showing the vehicle to which the present invention
is employed;
FIG. 2 is a control block diagram of the speed/steering control unit;
FIG. 3 is a front view of the instrument panel of the vehicle;
FIG. 4 is a flowchart for performing speed control;
FIG. 5 is a timing chart for performing speed control;
FIG. 6 is a characteristic diagram showing the turning pattern of the vehicle;
FIG. 7 is a structural diagram of the control block of a direction control device
according to another embodiment;
FIG. 8 is a block diagram showing in detail the rotation control circuit (drive
control means) provided to each rear wheel;
FIG. 9 is a frame format showing the appearance of the position designation
unit, auxiliary wheel designation unit, rotation angle designation unit, braking
designation unit and speed designation unit shown in FIG. 7;
FIG. 10 is a diagram showing the tilt pattern in the position designation unit;
FIG. 11 is a diagram showing the tilt pattern in the auxiliary wheel floatation
designation unit;
FIG. 12 is a characteristic diagram showing the relationship between the auxiliary
wheel floatation ratio and the vehicle acceleration;
FIG. 13 is a frame format showing the floating state of the auxiliary wheels;
FIG. 14 is a frame format showing the relationship between the steering direction
of the steering wheel and the vehicle direction;
FIG. 15 is a second frame format showing the relationship between the steering
direction of the steering wheel and the rotational direction of the vehicle; and
FIG. 16 is a third frame format showing the relationship between the steering
direction of the steering wheel and the turning direction of the vehicle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows the electric vehicle
10 comprising an example of the direction
control device of the present invention. This vehicle
10 drives the respective
left and right rear wheels
16B with an electric motor (pulse motor
12
described later). The vehicle body
14 is provided with two wheels in the
front and back; that is, a total of four wheels. Reference numeral
16A shows
the two front wheels and reference numeral
16B shows the two rear wheels.
These four wheels
16 ground and support the vehicle
10 on the road surface.
The front wheels
16A are so-called cast type wheels in which the direction
thereof freely changes in accordance with the traveling direction of the vehicle,
and are non-drive wheels. These front wheels
16A are not steered with a
steering device (steering wheel), and follow the moving direction and turning direction
of the vehicle. The steering of the vehicle, as described later, is achieved by
providing a rotation difference to the left and right rear wheels
16B, which
are the drive wheels.
The front wheels support the front side of the vehicle, and, as described above,
rotate in the front/rear/left/right directions in pursuit of the traveling direction
of the vehicle. Moreover, even in cases where the left and right rear wheels mutually
rotate in the opposite direction, the front wheels
16A become approximately
transverse against the front/rear direction, and will not hinder the rotational
movement of the vehicle
10. To the vicinity of these front wheels
16A,
an angle encoder
17 and gyro sensor
19 for detecting the rotational
angle of the vehicle are provided.
Each of the left and right rear wheels
16B is connected to a motor actuator
20. These motor actuators
20 are controllably connected to the speed/steering
control unit
22. Each of the left and right motor actuators
20 rotate
the drive wheels upon receiving a control signal from the speed/steering control
unit
22. The rotational status such as the rotational speed of the drive
wheels is thereby controlled. A rotation difference is provided to the respective
drive wheels in a rotating state.
The motor actuator
20 is structured by comprising a pulse motor
12,
which is an electric motor as the rotational driving means, a drive control unit
24 for controlling the drive of this pulse motor
12, and a transmission
mechanism unit
26 for transmitting the driving force of the pulse motor
12 to the axle
16B. The drive control unit
24 drives the pulse
motor
12 under a certain control characteristic and independently turns
the left and right rear wheels
16B based on the designated control signal
from the speed/steering control unit
22. Further, when the left and right
rear wheels
16B are rotated at an identical revolution and rotational speed,
the vehicle will either advance forward or move in reverse, and, when a revolution
difference or rotational speed difference is provided to the left and right rear
wheels, the vehicle will rotate or turn in the right direction or left direction
in accordance with such difference. In addition, when the left and right rear wheels
are rotated in the reverse direction, the vehicle will show a behavior of rotating
on its axis. Thus, the passenger is able to steer the vehicle by providing a rotation
difference to the left and right rear wheels.
FIG. 2 shows the control block structure corresponding to the control operation
performed by the speed/steering control unit
22. The foregoing speed/steering
control unit
22 provides a drive wheel control signal necessary in running/steering
the vehicle to each drive control unit
24 of the left and right rear wheels.
Next, the speed control of the vehicle is explained. Although the foregoing
drive control unit
24 exists for each of the left and right rear wheels,
the drive control unit of the left wheel and that of the right wheel are the same.
Thus, only one of the control units will be explained, and the description of the
other control unit will be omitted.
The drive control unit
24 comprises a PLL (Phase Locked Loop) control
circuit
22A, which is of a phase control system. The reference speed setting
unit
28 comprises a structure of dividing the frequency signal from the
crystal oscillator
30 with the M value corresponding to the designated speed
of the vehicle (designated by the speed designation unit
80 described later)
and outputting a reference frequency signal M. The reference frequency signal M
is input to the phase comparison unit
32.
A frequency signal N is input to the phase comparison unit
32 from the
designated
speed setting unit
34, and the phase comparison unit
32 compares
the frequency signal M and frequency signal N and outputs the phase difference
thereof as the phase difference signal to the LPF (Low Pass Filter)
36.
The LPF
36 outputs the control voltage signal, which is obtained by eliminating
high frequency components such as noise upon integrating the phase difference signal,
to the VCO (Voltage Control Oscillation Circuit)
38. The clock signal from
the VCO
38 is sent to the pulse motor driving driver
40 for driving
the foregoing pulse motor
12 of the driving unit
24. Thus, the pulse
motor driver
40 controls the drive of the pulse motor
12 in accordance
with the phase difference signal of the phase comparison unit
32.
The pulse motor
12 is provided with a rotation speed encoder
42.
This speed encoder
42 outputs a pulse signal corresponding to the rotation
of the respective rear wheels. This encoded signal is set as the frequency signal
S of the rear wheel driving motor in the actual measurement setting unit
44.
This frequency signal S is input to the comparison unit
46. In the comparison
unit
46, the frequency signal distributed for each of the left and right
wheels with the distribution unit
74 and corresponding to the designated
rotational speed of the respective rear wheels and the actual measurement frequency
signal S are compared to calculate the difference between the two, and the distribution
unit
74 decides whether the rotation of the rear wheels should be increased
or decreased, as well as with what degree of acceleration the rotation should be
increased or decreased in order to determine the N value (divided value), and distributes
this to the comparison unit
46 of the respective drive wheels. The comparison
unit
46 or the designated speed setting unit
34 N divides the frequency
signal S and sets this as the designated speed frequency signal in the designated
speed setting unit
34. The designated speed frequency signal N is output
from the designated speed setting unit
34 to the phase comparison unit
32.
Therefore, control in which the phase of frequency signal M and the phase
of frequency signal N coincide is implemented as described above, and the rotation
of the real wheels is controlled such that the vehicle speed is controlled to converge
to the designated speed. According to the foregoing control structure, the control
of rotational speed of the respective rear wheels is enabled with the PLL control
system, and is conducted with ease and expedition.
During the braking of the vehicle, the left and right pulse motors are separated
from the power source not shown in order to operate the motor as the power generator,
and the generated power is supplied to the storage cell thereby. Further, during
the sudden braking of the vehicle, in addition to the foregoing power generation
with a motor, a special braking means such as a magnetic brake may also be used.
Power may be generated with a motor for gradual braking or during non-acceleration,
and a special braking means may be used in addition thereto for sudden braking.
In order to change the traveling direction of the vehicle
10, a rotation
difference is provided to the left and right rear wheels
16B. Since the
front wheels
16A are casters as described above, the traveling direction
of the vehicle
10 is altered in accordance with the rotation difference
of the left and right rear wheels
16B. In the speed/steering control unit
22, control is implemented for providing a rotational speed to the respective
drive wheels so as to achieve the designated vehicle traveling speed while providing
a rotation difference to the left and right rear wheels to the drive control unit
24 disposed independently to the left and right rear wheels
16B.
The speed/steering control unit
22 comprises a curvature setting unit
76 for setting the curvature radius upon turning the vehicle
10,
and a turning direction operation unit
78 for computing the actual turning
direction of the vehicle from the detected value from the sensor. Input to the
curvature setting unit
76 are the designated speed from the speed designation
unit
80 provided to the instrument panel
50 (c.f. FIG. 3) of the
vehicles and the designated direction from the direction designation unit
82.
Moreover, the actual speed from the speed encoder
42 is also input
to this curvature setting unit
76. Thereby, the curvature setting unit
76
calculates and seeks the optimum curvature from the designated turning direction,
the designated vehicle speed (rotational speed of the drive wheels), and the actual
speed, and this result is sent to the distribution unit
74. In other words,
a sudden turn is allowed when the speed is slow, and the curvature radius will
increase during high speed travel.
Meanwhile, a signal from the angle encoder
17 and gyro sensor
19
provided to the vehicle
10 is input to the turning direction operation unit
78, and, for example, the turning angle of the vehicle with the direction
during direct advancement as the reference is calculated, and output to the foregoing
distribution unit
74. At the distribution unit
74, the difference
between the designated direction and actual direction, and the designated value
N for driving the respective rear wheels
16B based on the designated speed
are distributed and sent to the drive control unit
24 of the respective
drive wheels.
FIG. 3 shows a frame format of an instrument panel
50 provided to the
driver's seat to which the passenger of the vehicle
10 will board. An ignition
key cylinder
52 is provided to this instrument panel
50, and the
control of this drive system is enabled by the passenger inserting the key not
shown into the ignition key cylinder
52 and turning the key to the ON position.
Further provided to the instrument panel
50 are a designated speed
display unit
54 (
80 in FIG. 2) for displaying the designated speed,
and a current speed display unit
56 for displaying the current speed. The
passenger is thereby able to visually compare the designated speed displayed on
the designated speed display unit
54 and the current speed displayed on
the current speed display unit
56. Moreover, although the display units
54 and
56 were respectively represented as a 7-segment display in
FIG. 3, the representation may be a dot-matrix display or an analog display.
A display unit
84 (
82 in FIG. 2) for displaying the traveling direction
of the vehicle is provided between the designated speed display unit
54
and the current speed display unit
56. This traveling direction display
unit
84 comprises a rotating disc
86 to which an arrow
88
is marked thereon, and indexes
90 for indicating the rotational quantum
of the vehicle are provided around the periphery of the disc
86. When the
vehicle is steered and the traveling direction thereof is changed, the disc
86
rotates such that the arrow
88 faces such direction, and, in accordance
with the vehicle facing the designated direction, the arrow of the disc rotates
so as to return to the position of direct advancement (display position of FIG.
3).
Further, a speed/turning direction designating operation stick
48
for designating the speed and turning direction is provided to the instrument panel
50. This operation stick
48 protrudes approximately perpendicularly
from the panel, and may be tilted toward an arbitrary direction of front/back/left/right
at a prescribed angle (c.f. dotted line of FIG.
3). Further, when the passenger
removes his/her hand from such operation stick, it returns to the state of being
approximately perpendicular as shown with the solid line in FIG. 3 with the biasing
power of the biasing means not shown.
Designation of the vehicle speed and vehicle turning direction may be
conducted independently depending on the direction this operation stick
92
is tilted, and the tilting to the front or back will increase/decrease the designated
speed. In other words, for example, while the operation stick is tilted toward
the front, the speed designation will increase, and the speed designation value
will be established upon the passenger removing his/her hand from the operation
stick
92. When the operation stick is tilted toward the back, the speed
designation value will decrease. By tilting the operation stick
92 toward
the left or right, the designation of the traveling direction of the vehicle; that
is, the steering of the vehicle is enabled. For instance, when the operation stick
is tilted toward the right, the disc
86 continues to rotate in the clockwise
direction of FIG. 3 at a prescribed speed, and, when the operation stick
92
is released, the designated rotational angle of the vehicle will be established.
The opposite will occur when the operation stick is tilted toward the left.
By controlling the speed of the respective left and right rear wheels
16B,
a rotation difference will arise between the drive wheels, and the vehicle will
begin to turn. Next, the disc
86 gradually begins to return to the position
of the direct advancement of the vehicle, and the turning of the vehicle is completed
once the disc returns to the position shown in FIG.
3.
Moreover, a stop key
62 is provided to the vicinity of the operation
stick
92. The stop key is for instantaneously making the designated speed
zero, and, by performing the ordinary stopping operation by pressing this stop
key, control is performed such that the vehicle is decelerated at an optimum acceleration
(minus) and stopped within a range that will not cause an abrupt braking. When
this stop key
92 is operated, the display on the designated speed display
unit
54 will become 0. Moreover, a separate key or pedal maybe separately
provided for stopping the vehicle, particularly for the purpose of emergency braking.
The operation of the present embodiment is now described below with reference
to the flowchart of FIG.
4 and the timing chart of FIG.
5.
Foremost, at step
100 of the speed control routine shown in FIG.
4(A), it is judged whether the key has been inserted in the ignition key
cylinder
52 to place the vehicle in the ON state, and, when this is judged
as positive, the routine proceeds to step
102.
At step
102, it is judged whether the designated speed is 0, and, when
this is judged as positive, the routine returns to step
100 since the designated
speed is 0. Moreover, when it is judged as negative in this step
102, the
routine proceeds to step
104 since it is judged that there is a speed designation.
At step
104, the rotational speed of the respective rear wheels is measured
with the speed encoder
42 and the actual measurement S thereof is read.
At the subsequent step
106, the designated speed and actual speed of the
vehicle are compared, and, when there is a speed difference between the two, since
it is necessary to adjust the speed, it is judged in step
108 as to whether
speed adjustment is required.
At step
108, when it is judged that speed adjustment is not required (negative
judgment), it is determined that the current speed is stable at the designated
speed, and the routine returns to step
100. Moreover, at step
108,
when it is judged that speed adjustment is required, the routine proceeds to step
110 in order to perform speed control with PLL control. At step
110,
as described above, the frequency signal phase is compared in the phase comparison
unit
32, and the drive of the respective drive wheels is controlled based
on the phase difference. In other words, as illustrated in step
112, frequency
M to become the reference is supplied to the PLL circuit in order to control the
drive of the electric motor
12 of the respective drive wheels such that
the current rotational speed of the rear wheels becomes frequency N of the designated
rotational speed.
At the subsequent step
114, it is judged whether the designated speed
has
been altered. In other words, it is judged whether the speed/turning direction
operation stick
92 of the instrument panel
50 has been operated or
not, and, when the designated speed has not been altered, the routine proceeds
to step
130. At this step
130, it is judged whether a designation
has been made regarding the turning direction. In other words, it is judged whether
the operation stick
92 has been operated in the left or right direction
of FIG. 3, and, when judged as negative, the routine returns to step
100,
and the travle of the vehicle
10 is controlled at the current designated
speed and traveling direction.
Here, when the designated speed has been altered at step
114, since
the operation result of the speed difference at the comparison unit
46 will
change, the routine proceeds to step
116 in order to set the frequency signal
N corresponding to the designated speed, and, thereafter, the speed is controlled
with the frequency signal N after the alteration thereof.
Further, when a direction designation is made at step
130, the routine
proceeds to step
132, and the optimum turning curvature of the vehicle is
selected based on the current speed. In the present embodiment, the curvature to
be selected in the respective driving wheels in conformity with the curvature of
the vehicle is determined as shown in FIG.
6. In other words, for direct
advancement, the left and right rear wheels
16B are driven at an equal speed.
With this as the reference, when turning left, there is a pattern of making the
left rear wheel
16B at ½ the drive speed of the right rear wheel, a
pattern of stopping the drive of the left rear wheel
16B, a pattern of reversing
the left rear wheel
16B at ½ the drive speed of the right rear wheel
16B, and a pattern of reversing the left rear wheel
16B at the same
drive speed of the right rear wheel
16B.
Moreover, when turning right, there is a pattern of making the right rear
wheel
16B at ½ the drive speed of the left rear wheel
16B, a
pattern of stopping the drive of the right rear wheel
16B, a pattern of
reversing the right rear wheel
16B at ½ the drive speed of the left
rear wheel
16B, and a pattern of reversing the right rear wheel
16B
at the same drive speed of the left rear wheel
16.
For example, FIG. 6 explains an example of the vehicle making a gradual left
turn. The mathematization of the operational status of this vehicle can be represented
as follows:
Cos θ=
W/W2√{square root over (+MVL2)} (1)
MVL=W COS
2√{square root over (θ-1)} (2)
θ: Angle of direction for turning against the direct advancement (current
direction of advancement).
W: Pitch measurement of the left and right rear wheels.
MVL: Linear velocity difference per time unit of the left and right rear wheels.
Each of these patterns are classified into a gradual turn, standard turn, rapid
turn, and U-turn of the vehicle, and selected as the drive mode of the respective
drive wheels in accordance with the vehicle speed.
When the curvature radius pattern of the traveling direction of the vehicle
is selected at step
132, the routine proceeds to step
134 and calculates
the rotational speed difference of the respective rear wheels
16B based
on the selected curvature, and, at the subsequent step
136, the aforementioned
designated value N for controlling the speed of the respective rear wheels
16B
based on the current speed is set, and the routine then returns to step
100.
When the stop key
62 is operated during the control routine described
above, the braking interruption routine shown in FIG.
4(B) is activated,
and, in addition to the actual measurement S of the motor rotation being read at
step
120, deceleration at a prescribed acceleration (minus) based on the
actual measurement S is commenced at step
122. As a result, the vehicle
10 will stop after the vehicle speed is converged to zero.
Next, control from the phase control unit
32 to the driver
40
via the VCO
38 is explained with reference to the timing chart illustrated
in FIG. 5 in a case where the vehicle
10 is actually driven by repeating
acceleration and deceleration. Moreover, in FIG. 5, explained as the control parameters
are the speed designation value, set frequency signal N, PLL control frequency
signal M, and vector value representing the frequency increase/decrease.
Although the example shows a mode where the vehicle
10 is advancing
directly forward, when the vehicle is steered, each of the rear wheels is controlled
at a different speed designation value so as to generate a rotational speed difference
in the respective wheels
16B. Exemplified is the change in the speed designation
value against the time axis, and the upward direction of the vertical axis represents
high speed, and the downward direction represents low speed. Moreover, the vector
display corresponding to the frequency increase/decrease implies that the frequency
of the set frequency signal N is being increased (accelerated) in order to increase
the rotational speed of the motor when the vector is facing the upward direction
in the diagram, and, contrarily, implies that the frequency is being lowered (decelerated)
when facing the downward direction. Further, when the vector is parallel against
the time axis, such portion implies that the vehicle is being maintained in a constant
speed state upon making the frequency of the set frequency signal N to be constant.
When the speed designation value is raised, the set frequency N foremost becomes
higher in accordance therewith, and the PLL control frequency M thereafter becomes
higher (area in which the frequency vector turns upward). Further, when the speed
designation value of the vehicle is lowered, the set frequency N foremost becomes
lower in accordance therewith, and the PLL control frequency M thereafter becomes
lower (area in which the frequency vector turns downward). Further, when maintaining
the speed, the set frequency N and the PLL control frequency M coincide (area in
which the frequency vector is horizontal). The aforementioned control is realized
with the PLL control system based on the phase difference between frequency signals
N and M.
As described above, with the present embodiment, the frequency phase comparison
control with the PLL circuit is employed in the speed control of the vehicle
10,
and, since the PLL circuit is used to control the drive status of the pulse motor
12, the vehicle speed is automatically increased or decreased to the previously
designated speed. Further, since the vehicle travels steadily at this speed when
the vehicle speed reaches the designated speed, burden on the passenger can be
alleviated. This type of speed control is optimum for the control of electric wheelchairs.
Further, according to the foregoing speed control, since the passenger is not required
to needlessly increase the vehicle speed, the power consumption of the electric
motor can be kept to a minimum, and this is optimum in vehicles where power is
limited; for exam
