JP2004272411A - Steering correction device for autonomously traveling vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering correction device which is simple in structure and adequately corrects a traveling error of a vehicle every time the wheels slip sideways when the vehicle is turning. <P>SOLUTION: A caster 4 which travels, while quaking, in the direction of the movement of the body 1 of the autonomously traveling vehicle, which turns by controlling the steering angle of a steering wheel 12, is provided on the lower surface of the body 1, and the setting steering angle of the steering wheel 12 is corrected so that the traveling-oscillation angle θS of the caster detected by a caster sensor 5 may agree with a reference oscillation angle θP of the caster found from the setting steering angle α of the steering wheel 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steering correction device for an autonomous vehicle, and more particularly, to a steering correction device for an autonomous vehicle that turns by controlling the steering angle of steered wheels of a vehicle body.
[0002]
[Prior art]
There is a case where an unmanned guided vehicle traveling along a guide line laid on a floor surface of a factory or the like leaves the guide line at a curved portion of a traveling course and performs autonomous traveling by its own control operation. FIG. 4 shows an example of a conventional autonomous vehicle. This autonomous vehicle includes a pair of driven wheels 11 at a front portion of a vehicle body 1, a steering wheel 12 also serving as a drive wheel at one of the vehicle width directions at a rear portion of the vehicle body, and a caster 4 at the other side in the vehicle width direction. ing. The conventional autonomous traveling vehicle controls the steering angle of the steered wheels 12 to make the traveling course turn around the turning center S. However, if the steered wheels 12 skid during the turning traveling, the traveling course will be increased. There has been a problem that running errors are accumulated and the running course is greatly deviated. For example, as shown in FIG. 5, when a large load is applied to the driven wheel 11 of the front wheel by a load or the like and the rolling resistance of the driven wheel 11 increases, the steered wheel 12 serving also as the driving wheel slides outward. Therefore, even if the steered wheels 12 are set to the steering angle α, the traveling errors of the vehicle body 1 are accumulated, and the vehicle goes inward from a predetermined traveling course. Will come.
[0003]
Conventionally, as a method of correcting such a traveling error, for example, a method of projecting light from a traveling vehicle onto a reflector disposed on a traveling course and correcting the traveling error based on the reflected light, or a method of disposing the traveling error on a reflecting course arranged on a traveling course Many proposals have been made to detect a posture correction pointer and correct a running error by correcting a vehicle body posture angle detected by a gyro based on the detection signal (for example, see Patent Documents 1 and 2). . However, these methods have a problem that a device mechanism for detecting a traveling error is complicated and cost is increased.
[0004]
[Patent Document 1]
JP-A-57-182209 [Patent Document 2]
JP-A-60-175117
[Problems to be solved by the invention]
The present invention has been made in view of the above-described difficulties in the conventional steering correction device for an autonomous vehicle, and even if a skid occurs on a wheel during turning, a traveling error of the vehicle body is reduced each time. An object of the present invention is to provide a steering correction device having a simple configuration capable of performing correction.
[0006]
[Means for Solving the Problems]
A steering correction device for an autonomous vehicle according to the present invention is a steering correction device for an autonomous vehicle that turns by controlling the steering angle of a steered wheel provided on a vehicle body, and is provided on a lower surface of the vehicle body. A caster that travels while swinging according to the moving direction of the vehicle body, a caster sensor that is provided on the vehicle body and detects a travel swing angle of the caster during turning traveling, and a vehicle body that is determined from a set steering angle of the steered wheels. Calculating means for calculating a reference swing angle of the caster based on a reference turning center; andcorrection means for correcting the steering angle of the steered wheels so that the traveling swing angle of the caster matches the reference swing angle. It is characterized by including.
[0007]
Further, the steering correction device for an autonomous vehicle according to the present invention is characterized in that the reference turning center is set in advance, and the calculating means calculates a reference swing angle of the caster based on the reference turning center.
[0008]
Still further, in the steering correction device for an autonomous vehicle according to the present invention, the reference turning center is set in advance, the steering angle of the steered wheel is set based on the reference turning center, and The reference swing angle of the caster is calculated based on the turning center.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
A steering correction device for an autonomous vehicle according to an embodiment of the present invention will be described with reference to FIGS. In the following, constituent members described in the related art are denoted by the same reference numerals, and detailed description and illustration thereof are omitted.
[0010]
As shown in FIG. 1, a steering correction device for an autonomous vehicle according to the present embodiment includes a caster 4 provided on a lower surface of a vehicle body 1, a caster sensor 5 for detecting a running swing angle of the caster 4, and a steering wheel 12. Calculating means 6 for calculating the reference swing angle of the caster 4 based on the set steering angle, and correcting means for correcting the steering angle of the steered wheels 12 so that the traveling swing angle of the caster 4 matches the reference swing angle. 7 is comprised.
[0011]
As shown in FIG. 2, the casters 4 are provided on the rear left side with respect to the traveling direction of the vehicle body 1, and run while swinging around the king pin 41 according to the moving direction of the vehicle body 1. The autonomous vehicle according to the present embodiment stably supports the vehicle body 1 by a pair of driven wheels 11 serving as front wheels, a steering wheel 12 serving also as a driving wheel serving as a right rear wheel, and a caster 4 serving as a left rear wheel. I have. As described above, in the present embodiment, the casters 4 are disposed on the rear left side of the vehicle body 1 in order to stably support the vehicle body 1. For example, the driven wheels 11 as a pair of front wheels are provided at the front of the vehicle body 1. In a case where the vehicle body 1 can be stably supported only by the driven wheel 11 and the steering wheel 12 by providing a steering wheel 12 also serving as a driving wheel at the center of the rear portion of the vehicle body in the vehicle width direction, the caster 4 May be arranged at any position on the lower surface of the vehicle body.
[0012]
The caster sensor 5 is constituted by a rotary potentiometer that detects the rotation angle of the king pin 41 of the caster 4. The caster sensor 5 detects a swing angle of the caster 4 with respect to the vehicle body 1 when the autonomous traveling vehicle is actually turning, as a travel swing angle. Then, a signal corresponding to the traveling swing angle is output to the correction means 7.
[0013]
The calculating means 6 obtains a set steering angle signal of the steered wheels 12 from the steering angle commanding means 2, calculates a reference turning center position of the vehicle body 1 based on the set steering angle, and further calculates a reference turning center position based on the reference turning center position. Then, the reference swing angle of the caster 4 is calculated. That is, the calculating means 6 calculates the swing angle which the caster 4 will show when the vehicle body 1 turns as set, as the reference swing angle. Then, a signal corresponding to the reference swing angle is output to the correction means 7. When the traveling path of the autonomous traveling vehicle is determined, the position of the reference turning center at the turning position and the reference swing angle of the caster 4 may be stored in the vehicle in advance.
[0014]
The correction means 7 compares the travel swing angle detected by the caster sensor 5 with the reference swing angle calculated by the calculation means 6 so that the travel swing angle of the caster 4 matches the reference swing angle. And outputs a correction signal to the steering control means 3. The steering control means 3 corrects the set steering angle commanded by the steering angle command means 2 based on the correction signal, and corrects the steering angle of the steered wheels 12.
[0015]
Hereinafter, an operation example of the steering correction device of the present embodiment will be described with reference to FIGS. 2 and 3. Here, a case will be described in which, when the steered wheels 12 of the autonomously traveling vehicle make a turn with the steering angle set to α, the steered wheels 12 skid outward and the vehicle body 1 attempts to turn inward from a predetermined course.
[0016]
In this case, as shown in FIG. 2, the vehicle body 1 is supposed to turn around the reference turning center S, but actually turns around a position different from the reference turning center S (for example, the turning center P). That is, the caster 4 starts running at the swing angle θP corresponding to the inward running. In the steering correction device according to the present embodiment, the travel swing angle θP is detected by the caster sensor 5, and the correction means 7 compares the travel swing angle θP with the reference swing angle θS.
[0017]
As shown in FIG. 3, when the traveling swing angle θP is larger than the reference swing angle θS, the correcting unit 7 determines that the vehicle body 1 is rotating inward from the predetermined course, and performs A correction signal is output to the steering control means 3 so as to make the steering angle of the steered wheels 12 smaller than the set steering angle α by the correction steering angle β. Conversely, when the traveling swing angle θP is smaller than the reference swing angle θS, the correction means 7 determines that the vehicle body 1 is out of the predetermined course, and turns the steered wheels 12 so that the vehicle body 1 is turned inward more than it is now. A correction signal is output to the steering control means 3 so that the angle is made larger by the correction steering angle than the set steering angle α. If the traveling swing angle θP is equal to the reference swing angle θS, the correction means 7 determines that the vehicle body 1 is turning on a predetermined course, and the steered wheels 12 are directly controlled to the set steering angle α. It is. Thus, the steering correction device of the present embodiment corrects the steering angle of the steered wheels 12 by comparing the traveling swing angle θP with the reference swing angle θS. The correction steering angle β can be appropriately set in consideration of, for example, the slip resistance of the steered wheels 12 with respect to the floor. For example, if the traveling swing angle θP of the caster 4 is larger than the reference swing angle θS by one degree, the steered wheels 12 are made smaller by one degree. Conversely, if it is smaller once, it is increased once. Alternatively, the correction value is calculated by multiplying the angle difference between the traveling swing angle θP of the caster 4 and the reference swing angle θS by a gain value, and the steered wheels 12 are controlled based on the calculation result. When the optimum value is obtained by actually running the gain value, more accurate control of the steered wheels 12 can be performed.
[0018]
As described above, in the steering correction device for an autonomous vehicle according to the present embodiment, the traveling error of the vehicle body 1 with respect to a predetermined traveling course is detected by using the casters 4 that directly reflect the actual traveling state. Therefore, even if a running error due to skidding of the wheels occurs, the running error can be accurately corrected each time, and the running error is accumulated with the running as in the conventional case, and the vehicle body greatly deviates from the running course. No problem.
[0019]
Further, since the steering correction device of the present embodiment can detect the traveling error of the vehicle body 1 with a very simple device, a reflector or a posture correction pointer is provided at a predetermined position on a traveling course as in a conventional autonomous vehicle. There is no need to dispose it, and the device mechanism for detecting a traveling error does not become complicated or cost increases.
[0020]
Although the embodiments of the present invention have been described above, the steering correction device for an autonomous vehicle according to the present invention can be implemented in other embodiments. For example, in the above-described embodiment, the position of the reference turning center S is calculated based on the set steering angle of the steered wheels 12 obtained from the steering angle commanding means 2. However, for example, the reference turning center is set in advance. In a case where the set steering angle of the steered wheels 12 is set on the basis of the reference turning center and the present invention is applied to an autonomous traveling vehicle that turns on the traveling course, the caster 4 is controlled based on the preset reference turning center. The reference swing angle may be calculated.
[0021]
Further, in the above-described embodiment, an example is described in which the steering correction device is applied to an autonomous traveling vehicle having a steering wheel 12 also serving as a driving wheel on the rear right side of the vehicle body 1, but the present invention is not limited to this. However, the present invention can be applied to, for example, an autonomous vehicle that is provided with a plurality of steered wheels at a plurality of locations on a vehicle body and turns with the plurality of steered wheels. In this case, the reference swing angle of the caster may be calculated based on the set steering angles of the plurality of steered wheels.
[0022]
The present invention can be implemented in various modified, changed, and modified modes based on the knowledge of those skilled in the art without departing from the spirit of the present invention. In addition, within the range in which the same operation or effect occurs, any of the invention-specific matters may be replaced with another technology, and the integrally-structured invention-specific matter may be replaced by a plurality of members. The present invention may be embodied in a form in which the invention-specific matters constituted by a plurality of members are integrally constituted.
[0023]
【The invention's effect】
As described above, according to the steering correction device for an autonomous vehicle according to the present invention, the traveling error of the vehicle body with respect to the traveling course can be detected by using the caster that directly reflects the actual traveling state. Even if a running error occurs due to the skidding of the wheels, the running error can be accurately corrected each time, and the running error is accumulated together with the running as in the conventional case, and there is no problem that the vehicle body largely deviates from the running course. . Therefore, for example, there is no hindrance to cargo handling immediately after turning.
[0024]
Further, according to the present invention, the traveling error of the vehicle body can be detected with a very simple device mechanism. Therefore, it is necessary to dispose a reflector and a posture correction pointer at a predetermined position on a traveling course as in a conventional autonomous vehicle. In addition, there is no need to complicate the device mechanism for detecting the traveling error or increase the cost. Since the device mechanism is simple, it can be easily applied to a conventional autonomous vehicle.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a steering correction device for an autonomous vehicle according to an embodiment of the present invention.
FIG. 2 is a schematic plan view illustrating a state in which the autonomous traveling vehicle turns inward from a predetermined traveling course.
FIG. 3 is a schematic plan view illustrating an operation state of the steering correction device according to the embodiment.
FIG. 4 is a schematic front view illustrating a state in which a conventional autonomous traveling vehicle turns around a predetermined traveling course.
FIG. 5 is a schematic plan view illustrating a state in which a conventional autonomous traveling vehicle turns inward from a predetermined traveling course.
[Explanation of symbols]
Reference Signs List 1 vehicle body 11 driven wheel 12 steered wheel 4 caster 41 king pin 5 caster sensor 6 calculating means 7 correcting means α set steered angle S of steered wheel S reference rotation center (of vehicle body) θS reference swing angle of caster θP travel swing angle of caster

Claims (3)

A steering correction device for an autonomous vehicle that turns by controlling a steering angle of a steering wheel provided on a vehicle body,
A caster provided on a lower surface of the vehicle body and traveling while swinging according to a moving direction of the vehicle body;
A caster sensor that is provided on the vehicle body and detects a traveling swing angle of the caster during turning traveling;
Calculating means for calculating a reference swing angle of the caster based on a reference turning center of the vehicle body obtained from a set steering angle of the steered wheels;
Correction means for correcting the steering angle of the steered wheels so that the traveling swing angle of the caster matches the reference swing angle,
A steering correction device for an autonomous vehicle, comprising: The steering correction device for an autonomous vehicle according to claim 1, wherein the reference turning center is set in advance, and the calculating means calculates a reference swing angle of the caster based on the reference turning center. The reference turning center is set in advance, the steering angle of the steered wheel is set based on the reference turning center, and the calculating means calculates a reference swing angle of the caster based on the reference turning center. The steering correction device for an autonomous traveling vehicle according to claim 1.

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