JP3329963B2 - Automated guided vehicle steering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic guided vehicle that automatically travels along a taxiway, enabling all four wheels provided on the guided vehicle to be steered, enabling the guided vehicle to turn in a narrow place, and The present invention relates to a method of steering an automatic guided vehicle, which enables smooth change of the vehicle.

[0002]

2. Description of the Related Art In order to transport articles in a clean room such as a semiconductor manufacturing factory, an automatic guided vehicle excellent in suppressing dust generation is used. This transport vehicle travels in a clean room by being guided by a guide provided in advance along a transport process. One of the prior arts of this carrier is Japanese Patent Publication No. 6-46.
There is an unmanned vehicle described in Japanese Patent No. 364. As shown in FIG. 4, two driving wheels which can be independently rotated are provided at the left and right sides of the center of the lower surface of the bogie of the unmanned vehicle, and the position of the guide path is detected by a guide sensor (not shown). The unmanned vehicle is provided with casters that can rotate freely to maintain the overall balance at the center of the front (or rear) portion of the bogie so that the vehicle runs by driving a drive motor provided with wheels.

[0003]

Therefore, in a three-wheeled carrier in which one front wheel is used for steering and two rear wheels are used for driving, a turning radius at the time of turning and an area occupied by a locus are large, and a track in a narrow place is required. Was difficult to change. Another drawback is that the trajectories of traveling when traveling forward and when traveling backward are different.

The present invention employs a four-wheel system, in which each of the four wheels is independently steered and each of the front and rear wheels is independently driven, so that the turning of the carrier in a narrow place and the change of the track can be reliably performed. The purpose is to do.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and makes it possible to independently control the steering of four wheels provided on the lower surface of a carrier and to drive each of the front and rear wheels one by one. In a method of steering an automatic guided vehicle that travels while independently controlling the speeds of the drive wheels, two front wheels are steered in the traveling direction of the carrier, and the rear part of the carrier at the start of turning of the carrier. The two rear wheels are steered in the traveling direction guided by the front wheels so that the trajectory does not protrude from the straight trajectory and smoothly transition to turning, and then the two front wheels and the two rear wheels are in opposite phases. To turn the carrier at a predetermined radius, then steer the two rear wheels toward the direction of travel of the two front wheels, and at the end of the turn, move the trajectory of the front of the carrier from the straight trajectory. Steer to move straight ahead without protruding The gist of the door.

[0006]

[Operation] When turning with a constant radius, the front and rear wheels are steered in opposite phases to turn. The left and right steering angles of the turning center are different from the turning radius of the inner wheel because the turning radius of the outer wheel and the turning radius of the inner wheel are different, so that the steering angle of the inner wheel is larger than the steering angle of the outer wheel. Correct the steering angle. Further, the rotational speed of the drive wheel is corrected such that the rotational speed of the inner wheel is smaller than the rotational speed of the outer wheel so that the rotational speed of the inner wheel is smaller. When shifting from straight running to turning with a fixed radius, the front wheels are steered to a steering angle corresponding to the turning radius. On the rear wheel side, when the turning angle of the vehicle body is equal to or less than the steering angle of the front wheel, the steering angle of the rear wheel is matched with the turning angle of the vehicle body, and the rear wheel side is steered so as to always face the traveling direction. When the turning angle of the vehicle body coincides with the steering angle of the front wheels, the phase of the steering angle of the rear wheels is inverted to the steering angle of the front wheels to make the absolute values coincide with each other. Perform steering.
Further, when the vehicle shifts from turning to straight running, the sign of the steering angle of the front wheels is reversed to be equal to the turning angle of the vehicle body until the turning angle becomes zero by the reverse operation, and the front of the vehicle body always faces the traveling direction. And the rear wheels are steered at a constant angle. And when the turning angle of the body becomes zero, the front wheels,
The steering angle of the rear wheels is shifted to zero, and the vehicle shifts to straight running.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for steering an automatic guided vehicle according to the present invention will be described below with reference to an embodiment shown in the drawings. In the drawing, reference numeral 1 denotes a bogie of an automatic guided vehicle, and four traveling wheels are arranged on the lower surface of the bogie so that the bogie 1 runs stably.
One of the driving wheels is a driving wheel, the driving wheels 2 and 5 are provided with driving motors to be driving wheels, the other two wheels are driven wheels 3 and 4 having no driving motor, and the two driving wheels 2 and 5 are driven wheels. , 5 are arranged at diagonal positions with respect to the carriage 1.

Each of the driving wheels 2, 5 and the driven wheels 3, 4 is provided with a steering mechanism (not shown).
5 can be independently steered.

Further, the driving wheel 2 and the driven wheel 3 disposed at both ends of the front end and the rear end in the traveling direction of the carriage 1 are paired, and the front and rear driving wheels 2 and 5 are located at diagonal positions of the carrier 1. The driven wheels 3 and 4 are also disposed at diagonal positions of the carrier. Although not shown, the transport vehicle 1 includes a guide device for guiding the transport vehicle along a track at a portion of a front and rear driven wheel and a straight road, and a control device for controlling steering and driving. A taxiway 10 is laid in.

Accordingly, a description will be given of a method of traveling the automatic guided vehicle of the present invention configured as described above along a taxiway.
Now, the transport vehicle 1 is moved from one straight road 11 through a curved road 12 to another straight road 13 without using a guiding device provided on the ground.
When the trajectory is changed, the guidance control is performed by the guidance device so that the trajectory always coincides with the guidance path in the straight part, and since there is no guidance in the curved part, the trajectory of the turn is determined in advance, and This will be described with reference to FIG.

In FIG. 1, (A) is a part of guidance control for straight traveling along a guidance road, (B) is a steering wheel in which a front wheel is steered along a turning trajectory, and a rear wheel is steered in a straight traveling direction. (C) is a part that performs steering so that both the front and rear wheels follow the turning trajectory, and (D) is a part that performs steering so that the front wheel follows a straight path after the course change. The rear wheel performs steering along the turning locus, and (E) shows the part that completes turning and performs guidance control so that both the front wheel and the rear wheel follow the straight line after the track change.

In the section of the front and rear wheels, one straight road 1
When the transport vehicle 1 travels along the curved road 1, the A
2, the rear wheels are in the section B where the rear wheels are still on the straight road 11, the front wheels are in the section of the straight road 13, and the front and rear wheels are equal in the section E of the other straight road 13 so that the left and right steering angles are equal. , The front wheels in section B and section C
, And the rear wheels in the section D independently control the steering of the left and right wheels so that each wheel faces the tangential direction of the center of the turn. Table 1 shows the relationship between the steering control of the front wheels and the rear wheels and the control section.

[0013]

[Table 1]

FIG. 2 shows the relationship between the wheels when the carrier 1 travels on a curved section of the taxiway. In FIG. 2, the center of the turning locus is O, the turning radius of the inner wheel is r1, the turning radius of the outer wheel is r2, the center of the vehicle and the turning center, the angles between the left and right wheels are φ1, φ2, and the steering angles of the inner and outer wheels. To θ1, θ
2. If the interval between the front and rear wheels (wheel base) is WB and the interval between the left and right wheels (tread) is TR, the following is obtained.

[0015]

(Equation 1)

The relation between the turning radius of the inner wheel and the turning radius of the outer wheel is expressed by the equations (1) and (2), and the angles φ1 and φ2 with respect to the turning center are obtained from the relation of the equation (3). ), (5). The relationship between the running speed of the inner wheel and the outer wheel and the turning radius / angle of the turning center is expressed by Equations (6) and (7) in Equation 1.
Becomes Here, ω indicates the angular velocity of the turning, and the turning center is kept at a constant value. The speed of the inner wheel is given by Expression 8 with respect to the speed of the outer wheel.

The angle of the turning center and the steering angle are expressed by equation (9)
(10) Based on these relationships, a turning radius is given to determine the trajectory, the steering angle and the rotational speed of the wheel are determined, and the vehicle can be driven along the trajectory on a trajectory where no taxiway exists.

FIG. 3 shows an embodiment in which the turning center O is set at the center of the vehicle body in a narrow place as an application of the present invention. The steering angle in this case is as shown in Expression 2.

[0019]

(Equation 2)

The present invention is applicable not only to control during automatic operation but also to manual operation. During manual operation, the steering angle of the outer wheel is set at an arbitrary angle by a command device, and the steering angle of the inner wheel and the rotation speed of the inner wheel are calculated based on the steering angle of the outer wheel and the speed command source to determine the control amount.

The present invention can be applied not only to a trackless carrier running on four wheels, but also to the steering of a tracked carrier.

As shown in FIG. 5, when turning along the outer periphery of equipment or obstacles arranged in the factory without protruding the corners thereof, the inner wheels are stopped and the outer wheels are stopped. In the case of turning the corner of the obstacle by the above, the center of the turn is on the line connecting the front and rear wheels of the inner wheel, and the steering angle θ1 of the inner wheel is obtained by the following equation.

[0023]

(Equation 3)

In the case where the vehicle turns along the corner of the obstacle, as shown in FIG. 4, the trail of the rear part of the transport vehicle protrudes outward from the trail of the front part. At the time of this corner work, as shown in FIG. 4, the wheels can be steered to turn sideways on the inner wheel and at an angle θ2 on the outer wheel to make a small turn.

[0025]

According to the automatic guided vehicle steering method of the present invention, the turning angle of the inner wheel and the outer wheel during turning is adjusted to the tangential direction of the turning circle, thereby turning the vehicle on a fixed locus with reduced running resistance during turning. . During turning, the front wheel and the rear wheel follow the same trajectory and the turning radius is smaller for the same steering angle compared to the three-wheel carrier, and when the steering angle of the inner wheel is steered at right angle, the turning of the body width around the inner wheel side I do. Further, the present invention has an advantage that a so-called spin turn with the turning center at the center of the vehicle body can be easily realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for steering an automatic guided vehicle according to the present invention, showing a trajectory of the guided vehicle and a control switching section.

FIG. 2 is an explanatory diagram illustrating a relationship between a turning locus, a steering angle, and a turning radius of the carrier.

FIG. 3 is an explanatory diagram showing a relationship between a steering angle and a turning radius during a spin turn.

FIG. 4 is an explanatory diagram of wheel steering when turning a corner.

FIG. 5 is an explanatory diagram of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conveyor vehicle 2 Drive wheel 3 Driven wheel 4 Driven wheel 5 Drive wheel 10 Guideway 11 One straight road 12 Curved road 13 The other straight road

Claims (2)

(57) [Claims] 1. Four wheels provided on the lower surface of a transport vehicle can be independently controlled for steering, and each of the front and rear wheels is a drive wheel,
In the method of steering an automatic guided vehicle that independently controls the speed of the drive wheels and travels, the two front wheels are steered so as to be directed in the traveling direction of the carrier, and the trail of the rear portion of the carrier at the start of the turn of the carrier. The two rear wheels are steered in the traveling direction guided by the front wheels so as to smoothly transition to turning without protruding from the straight path, and then the two front wheels and the two rear wheels are steered in opposite phases. Then, the carrier is turned by a predetermined radius, and then the two rear wheels are steered in the traveling direction of the two front wheels, and at the end of the turn, the trajectory of the front part of the carrier does not protrude from the straight trajectory. A steering method for an automatic guided vehicle, wherein the steering is performed so as to shift to straight running. 2. Four wheels provided on the lower surface of the carrier can be independently controlled for steering, and each of the front and rear wheels is a drive wheel.
In the method of steering an automatic guided vehicle that independently controls the speed of the drive wheels and travels, the two front wheels are steered so as to be directed in the traveling direction of the carrier, and the trail of the rear portion of the carrier at the start of the turn of the carrier. The two rear wheels are steered in the traveling direction guided by the front wheels so as to smoothly transition from a straight trajectory to a turn, and then the two front wheels and the two rear wheels are steered in opposite phases. At a predetermined radius, and then steer the two rear wheels toward the traveling direction of the two front wheels, so that the trajectory of the front part of the carrier shifts from the straight trajectory to the straight running at the end of the turn. A steering method for an automatic guided vehicle, characterized by steering.