JPH07248819A - Track control method for automatic running vehicle - Google Patents

Abstract

PURPOSE:To provide the track control method for automatic running vehicle which stabilizes track control and easily generates a track. CONSTITUTION:The segment connecting a preceding target point t1 on a track 2 and a next target point t2 is defined as a target track 20 of a vehicle 10, and a circle 21 which has a certain radius with the vehicle 10 as the center is drawn, and the intersection between this circle and the target track 20 is denoted as a temporary target point ta. If there are two intersections between the circle and the target track, one nearer intersection to the next target point is denoted as the temporary target point ta. An angle theta formed between a segment 16 connecting the temporary target point ta and a vehicle reference point 15 of the vehicle 10 and a vehicle reference line 13 is taken as a steering angle theta' of a steering driving wheel 12 to run the vehicle 10. After the temporary target point ta coincides with the next target point t2, a segment connecting this point and the next target point is defined as the target track 20. This control is repeatedly executed till the vehicle no arrives at the final target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track control method for an automatic vehicle which causes the vehicle to follow a target track by a steering mechanism.

[0002]

2. Description of the Related Art Conventionally, in a warehouse or the like, an automatic vehicle (AGV: Autonomous Guide) is used for loading and unloading cargo.
d Vehicle) is used. As a guidance system for this autonomous vehicle, generally, an electromagnetic induction system, a magnetic induction system,
An optical method or the like is used. However, in these methods, there is a problem that a guide wire is laid or a guide tape is attached each time the traveling route is changed.

In order to solve such a problem, recently, a method of mounting a laser guide device using a laser beam on an automatic vehicle and detecting the position of the vehicle by the laser guide device to control the track of the vehicle. Is being considered. In this method, when a vehicle travels from a station 1a to another station 1b, for example, as shown in FIG. Direction / speed / motion information is added to the map point (target point) 3 to be used as trajectory information (map data). These data are registered in advance in, for example, a memory mounted on the autonomous vehicle 10 shown in FIG. 7, and when a command is received from the operation room, the travel control is performed with reference to the contents of the corresponding map data.

FIG. 7 shows a schematic structure of an automatic vehicle 10 which is the subject of the present invention. The automatic traveling vehicle 10 has two fixed wheels 11a and 11b as front wheels and one steering drive wheel (steering wheel) 12 at the rear center as rear wheels. Then, a line passing from the center of the steering drive wheel 12 to the center of the vehicle 10 is set as a vehicle reference line 13, and the vehicle reference line 13 and the fixed wheels 11a, 1a.
The intersection with the central axis 14 of 1b, that is, the center of rotation of the vehicle 10 is set as the vehicle reference point 15. A laser guiding device is mounted on the vehicle reference point 15.

The vehicle 10 constructed as described above first proceeds on the track 2 shown in FIG. 6 with the initially set map point 3 as the target point, and when it judges that the map point 3 has passed, the vehicle 10 next Drive toward the target point set in.

FIG. 8 shows a coordinate system for explaining orbit control by the laser guiding device. In addition, FIG.
Shows a flowchart for trajectory control. The autonomous vehicle 10 first detects the coordinates (xv, yv) of the vehicle reference point 15 in each control cycle, and also detects the inclination angle α, that is, the angle α between the vehicle reference line 13 and the x-axis (step S1). ), The inclination angle β of the straight line 16 connecting the vehicle reference point 15 and the target point t is calculated (step S2). Next, the angle formed by the vehicle reference line 13 and the straight line 16, that is, α and β
Deviation .theta. Is calculated (step S3), and a steering angle .theta.
). Then, this steering angle θ'is output to adjust the angle of the steering drive wheel 12 (step S
Five ).

[0007]

In the conventional track control method described above, the distance between the vehicle 10 and the target point t changes as the vehicle 10 advances, so as shown in FIGS. 10 (a) and 10 (b). Even if the distance between the vehicle 10 and the track 2 is the same, the steering angle θ ′ greatly changes depending on the distance between the vehicle 10 and the target point t. That is, as shown in FIG. 10A, when the vehicle 10 is close to the target point t, the steering angle θ '
Is large and the vehicle 10 and the target point t are far from each other as shown in FIG. 10B, the steering angle θ ′ is small, and as a result, it is difficult to put the vehicle 10 on the track on which the vehicle should originally travel. is there. Especially when the target point is switched,
If the vehicle 10 deviates from the target trajectory by a small amount when the vehicle passes the target point, the steering angle θ'changes largely before and after that.

For the above reasons, the running condition of the vehicle 10 changes depending on the set target point interval even if the target track is a straight line. Need to set points. Therefore, the distance between the target points of the trajectory is important for control, requires a lot of knowledge when creating the trajectory, is very troublesome to create, and requires a long period of time.

Further, since the trajectory control is performed on the basis of the vehicle reference point 15 which is set at the turning center of the vehicle 10, the vehicle 10 which is away from the trajectory 2 returns to the trajectory 2 as shown in FIG. At this time, the posture of the vehicle 10 cannot be adjusted in time, and the vehicle 10 once protrudes on the opposite side of the track 2. That is,
As shown in FIG. 11C, the vehicle reference point 15 of the vehicle 10
When the vehicle 10 reaches the target point t, the vehicle 10 tries to put the vehicle 10 on the track 2 by adjusting the angle of the steering drive wheel 12, so that the vehicle 10 moves to the opposite side of the track 2 as shown in FIG. Only the distance d extends.

The present invention has been made in view of the above circumstances, and the steering angle can be proportional to the distance between the vehicle and the track without being affected by the distance between the vehicle and the target point. It is an object of the present invention to provide a trajectory control method for an automatic traveling vehicle, in which the vehicle can be stably operated and the trajectory can be easily created. Another object of the present invention is to provide a trajectory control method for an autonomous vehicle that can improve the trajectory following ability of the vehicle.

[0011]

A trajectory control method for an automatic traveling vehicle according to the present invention comprises (1) a step of setting a set of target points having a plurality of arrival orders, and (2) an arbitrary time point. A step of setting a line segment connecting a target point to be reached next and a target point reached immediately before as a target trajectory of the vehicle, and (3) tentatively defining an intersection point of a portion of a certain distance from the vehicle and the target trajectory. A step of moving the temporary target point as a target point with the movement of the vehicle over time, and (4) when there are two temporary target points, it is close to the next target point to be reached. The step of setting the other point as a temporary target point,
(5) A step of causing the vehicle to travel with a straight line connecting the temporary target point and the vehicle and an angle formed by the movement of the vehicle at that time as a steering angle of the steering wheel, Until the point is reached, the steps (3) to (5) are repeated to control the trajectory of the vehicle. Further, the present invention is characterized in that the vehicle reference point on the vehicle is moved in the traveling direction of the vehicle to be a movement reference point, and the trajectory control is performed based on the movement reference point.

[0012]

[Operation] A line segment connecting the previous target point and the next target point on the track is set as the target track of the vehicle, and the intersection of the portion at a certain distance from the vehicle reference point and the target track is set as the temporary target point. , By correcting the trajectory of the vehicle with respect to this temporary target point, the distance between the vehicle and the temporary target point will always be constant,
The steering angle is not affected by the distance between the vehicle and the target point, and becomes proportional to only the distance between the vehicle and the target trajectory. Therefore, the steering angle is always constant if the distance between the vehicle and the target trajectory is the same, and the trajectory control is stable.

Further, since the steering angle is not affected by the distance between the vehicle and the target point as described above, the distance between the target points on the track becomes completely unrelated to the track control, and as a result, the distance between the target points is increased. It is possible to easily create a trajectory in a short period without paying attention to the above.

Further, by performing the trajectory control using the movement reference point which is obtained by moving the vehicle reference point by a certain distance in the traveling direction of the vehicle, when the vehicle away from the trajectory returns to the target trajectory, When the movement reference point set further ahead reaches the target trajectory, the steering angle is adjusted, and the trajectory is corrected without the vehicle protruding to the opposite side of the target trajectory.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram for explaining a trajectory control method for an autonomous vehicle according to a first embodiment of the present invention. The automatic vehicle 10 has the same configuration as that described in FIG. 7, and has two fixed wheels 11a and 11b as front wheels,
As a rear wheel, one steering drive wheel (steering wheel) 12 is provided at the center of the rear part. And steering drive wheel 1
The line passing from the center of 2 to the center of the vehicle 10 is the vehicle reference line 1
3, the intersection of the vehicle reference line 13 and the center axis 14 of the fixed wheels 11a and 11b, that is, the rotation center of the vehicle 10 is the vehicle reference point 15. The vehicle 10 has a vehicle reference point 15
A laser guidance device (not shown) mounted on the computer, a computer that processes a signal from the laser guidance device to control the steering drive motor, receives a command from the operation room, and outputs a vehicle state signal to the operation room. It is equipped with a traveling control device such as a wireless device for wirelessly transmitting to.

Then, as described with reference to FIG. 6, for example, the track 2 for traveling the vehicle 10 from the station 1a to the station 1b is set by a set of target points and stored in advance in the memory of the traveling control device. In addition, the vehicle 10
In the area where the vehicle travels, a plurality of corner cubes (not shown) that reflect the laser light are arranged along the peripheral portion or the traveling path. For example, corner cubes are arranged at the four corners of the area in which the vehicle 10 travels. Vehicle 10
Laser light is scanned in a horizontal plane by a laser guiding device and projected onto a corner cube. Then, the laser light reflected by the three or more corner cubes closest to the corner cube is received by the sensor, and the relative position between the corner cube and the vehicle 10 and the deviation from the track 2 are calculated from the principle of triangulation. , Orbit control to correct the deviation.

The trajectory control of this automatic vehicle 10 is shown in FIG.
It is performed according to the flowchart shown in. First, as shown in FIG. 1, the vehicle 10 is assumed to have a line segment connecting a previous target point (target point reached immediately before) t1 and a target point t2 to be reached next on the track 2 at an arbitrary time, as shown in FIG. Is set as a target trajectory 20 (step A1), a circle 21 having a predetermined radius r centered on the vehicle reference point 15 is drawn, and the intersection point of the circle 21 and the target trajectory 20 is provisionally set. As the target point ta (step A2). In this case, if there are two tentative target points, the point closer to the next target point is set as the tentative target point ta (step A3). This temporary target point ta is moved with time as the vehicle 10 moves.

Then, the temporary target point ta and the vehicle reference point 1
The vehicle 10 is caused to travel with the angle θ formed by the straight line 16 connecting 5 and the vehicle reference line 13 as the steering angle (steering angle) θ ′ of the steering drive wheel (steering wheel) 12. The steering angle θ'is obtained by the means shown in FIGS. 8 and 9. That is, the coordinates (xv, yv) of the vehicle reference point 15
And the inclination angle α, that is, the angle α between the vehicle reference line 13 and the x-axis is detected, and the inclination angle β of the straight line 16 connecting the vehicle reference point 15 and the target point t is calculated. Then, the deviation θ between the inclination angles α and β is calculated, and the steering angle θ ′ (basically θ = θ ′) is set in the direction opposite to the direction of the target point t by an angle proportional to the angle θ.

In FIG. 1, the temporary target point ta is
When the target point t2 to be reached next coincides with the target point t2 to be reached next, the line segment connecting the coincident point and the target point to be reached next is set as the target trajectory 20. Then, it is determined whether or not the vehicle 10 has reached the target station (step A5
), If the target station has not been reached, the process returns to step A2 and the above-mentioned processing is repeated. That is, the processes of steps A2 to A5 are repeatedly executed until the vehicle 10 reaches the target station, and when it is determined in step A5 that the vehicle 10 has reached the station, the trajectory control process ends.

As described above, the intersection of the portion of the vehicle reference point 15 at a constant distance and the target trajectory 20 is set as the temporary target point ta,
By correcting the trajectory of the vehicle 10 with respect to the temporary target point ta, the distance between the vehicle 10 and the temporary target point ta is always constant, and the steering angle θ ′ is the distance between the vehicle 10 and the target point t. Is no longer affected by, and becomes proportional only to the distance between the vehicle 10 and the target trajectory 20. Therefore, the steering angle θ'is always constant if the distance between the vehicle 10 and the target track 20 is the same, and the track control is stable.
Further, even when the target point is switched, the steering angle .theta. 'Does not change greatly.

Further, it is possible to control the vehicle 10 to be placed not only on the target point t but also on the target track, and it is possible to cope with the case where the traveling road is narrow. Further, as described above, the steering angle θ'is not affected by the distance between the vehicle 10 and the target point t, so the distance between the target points on the track is completely unrelated to the track control, and as a result, the track is created. It becomes easier and the preparation period can be shortened.

(Second Embodiment) In the second embodiment, a vehicle reference point 1 set at the center of rotation of the automatic vehicle 10 or the like.
By moving the vehicle 5 in the traveling direction of the vehicle 10 to control the trajectory, the trajectory following performance is improved.

That is, in contrast to the first embodiment, as shown in the flowchart of FIG. 3, the process of step A1, that is, the line connecting the previous target point t1 on the trajectory 2 and the next target point t2 to be reached After the minute is set as the target trajectory 20 of the vehicle 10, the vehicle reference point 15 is set to the vehicle reference line 13 as shown in FIG.
Along the road, move a certain distance in the traveling direction and move to the reference point 15
Set a.

After that, the processes of steps A2 to A5 are executed in the same manner as the flowchart shown in FIG. 2, but at this time, the movement reference point 15a is used instead of the vehicle reference point 15 to control the trajectory of the vehicle 10. To do.

That is, in step A2, the movement reference point 15
A circle 21 with a radius r is drawn around a, and the intersection of this circle 21 and the target trajectory 20 is taken as a temporary target point ta. Then, in step A4, the angle θ formed by the straight line 16 connecting the provisional target point ta and the movement reference point 15a of the vehicle 10 and the vehicle reference line 13 is determined by the steering angle θ'of the steering drive wheel 12.
The vehicle 10 is driven as.

By using the movement reference point 15a in place of the vehicle reference point 15 in this manner, as shown in FIGS.
As shown in (1), it is possible to improve the track following ability when the vehicle 10 that has been away from the track 2 returns to the target track 20. That is, when the vehicle 10 that has been away from the track 2 returns to the target track 20 as shown in FIG. 5A, the movement reference point set ahead of the vehicle 10 as shown in FIG. When 15a reaches the target track 20, the angle adjustment of the steering drive wheels 12 is started, and thereafter, as shown in FIG.
The trajectory of the vehicle 10 is corrected as shown in (c) to (e). In this case, the distance between the vehicle reference point 15 and the movement reference point 15a is set in advance so that the vehicle 10 can efficiently return to the target trajectory 20. Therefore, the trajectory correction is performed without the vehicle 10 protruding to the opposite side of the target trajectory 20.
The trackability of 0 can be improved.

In the above embodiment, the automatic vehicle 10 is used.
Although the case where the fixed wheels 11a and 11b of the vehicle are driven in front has been described, the case of traveling in the case where the steering drive wheels 12 are driven in front and the case of traveling of another type of vehicle are the same as those in the above embodiment. The trajectory control can be performed in the same manner.

[0028]

As described in detail above, according to the present invention, a line segment connecting a previous target point and a target point to be reached next on the track is set as the target track of the autonomous vehicle, and the target track and the vehicle are set. Since the intersection of the part with a certain distance from the reference point is set as a temporary target point and the trajectory of the vehicle is corrected with respect to this temporary target point, the steering angle is influenced by the distance between the vehicle and the target point. It will not be received and will be proportional to the distance between the vehicle and the track. Further, since the steering angle is not affected by the distance between the vehicle and the target point, the distance between the target points becomes completely unrelated to the trajectory control, the trajectory can be easily created, and the preparation period can be shortened.

Further, in the present invention, instead of the vehicle reference point, the vehicle reference point is moved by a predetermined distance in the traveling direction along the vehicle reference line to perform the trajectory control of the vehicle. It is possible to improve the track-following property when the vehicle that has been away from the track returns to the target track.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a trajectory control method for an autonomous vehicle according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a trajectory control operation in the embodiment.

FIG. 3 is a timing chart showing a trajectory control operation in the second embodiment of the present invention.

FIG. 4 is a diagram showing an example of setting a movement reference point in the embodiment.

FIG. 5 is a diagram for explaining the operation when the vehicle that has been away from the track returns to the target track in the embodiment.

FIG. 6 is a diagram showing an example of setting a vehicle traveling track which is a target of the present invention.

FIG. 7 is a diagram showing an example of the configuration of an autonomous vehicle as a target of the present invention.

8 is a diagram showing a coordinate system by a laser guiding device for explaining a setting operation of a steering angle of a self-driving vehicle in FIG.

FIG. 9 is a flowchart showing a conventional orbit control method for an autonomous vehicle.

FIG. 10 is a diagram showing a difference in steering angle depending on a distance between a vehicle and a target point in a conventional trajectory control method.

FIG. 11 is a diagram for explaining an operation when a vehicle that has been away from the track returns to the target track in the conventional track control method.

[Explanation of symbols]

 1a, 1b Station 2 Autonomous vehicle orbit 3 Map point on orbit 10 Autonomous vehicle 11a, 11b Fixed wheel 12 Steering drive wheel 13 Vehicle reference line 14 Fixed wheel center axis 15 Vehicle reference point 15a Movement reference point 16 Vehicle reference A straight line connecting the point and the target point 20 Target trajectory 21 A circle with a defined radius centered on the vehicle reference point

Claims (2)

[Claims] 1. A step of setting a set of target points having a plurality of arrival orders, and (2) connecting a target point to be reached next and a target point reached immediately before at an arbitrary time point. A step of setting a line segment as a target trajectory of the vehicle,
(3) A step of moving a portion of a certain distance from the vehicle and the target trajectory to a temporary target point, and moving the temporary target point with the movement of the vehicle over time. (4) The temporary target point When there are two target points, a step closer to the next target point to be reached is set as a temporary target point, and (5)
And a straight line connecting the temporary target point and the vehicle and an angle formed by the movement of the vehicle at that time as a steering angle of the steered wheels, the step of causing the vehicle to travel, and the vehicle reaches the final target point. The track control method for an automatic vehicle is characterized in that the above steps (3) to (5) are repeated to control the track of the vehicle. 2. A step (1) of setting a set of target points having a plurality of arrival orders, and (2) connecting a target point to be reached next and a target point reached immediately before at an arbitrary time point. A step of setting a line segment as a target trajectory of the vehicle,
(3) A step of moving a vehicle reference point serving as a vehicle control reference in a vehicle traveling direction by a certain distance to set a movement reference point, and (4) a portion at a certain distance from the vehicle movement reference point and the target trajectory. And a step of moving the intersection of the temporary target point and the temporary target point with the movement of the vehicle over time, and (5) when there are two temporary target points, A step of setting a point closer to the target point to be used as the temporary target point, and (6) an angle formed by the straight line connecting the temporary target point and the movement reference point of the vehicle and the movement of the vehicle at that time. The steering angle of the steered wheels is set, and the vehicle is run, and the steps (4) to (6) are repeated until the vehicle reaches a final target point to perform trajectory control of the vehicle. A characteristic method for controlling the orbit of an autonomous vehicle.