JPH08123551A - Differential speed arithmetic method for four-wheel steering type automated guided vehicle - Google Patents

Abstract

PURPOSE: To enable stable traveling and to improve the accuracy of following to a leading guide by providing an automated guided vehicle, which can independently drive four wheels, and calculating differential speed with the speed of that driving wheel as the function of steering angle of two wheels for which following control is performed by the leading guide. CONSTITUTION: Since the truck of the automated guided vehicle is traveled along a leading guide 2, steering angles ϕ3 and ϕ2 of right side traveling wheels are respectively controlled to be changed by a driving motor so that deviation amounts δ3 and δ2 from the leading guide 2 can be '0' by a guide sensor integrated with the right front wheel and a guide sensor integrated with the right rear wheel. Next, steering angles δ1 and δ4 of the left side wheels are decided to be orthogonal to rotation radius ρ1 and ρ4. Thus, since the four rotation radius orthogonal to the arbitrary steering angle of all four traveling wheels are gathered to one point C, respective traveling wheel advancing direction V1-V4 are orthogonal to the respective rotation radius and side slip on the ground to travel the carrier can be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential speed control for a four-wheel steering type automatic guided vehicle, and more particularly to a differential speed calculation method for achieving stable running performance and improving the accuracy of following a guide. .

[0002]

2. Description of the Related Art When an article is conveyed in a clean room such as a semiconductor manufacturing factory, an automatic guided vehicle capable of suppressing dust generation is adopted. This is a system in which a magnetic or optical guideway is laid along the traveling process in a factory that runs in advance, and the guided vehicle is automatically guided by this guideway. On the lower surface, three running wheels are arranged in a relative relationship so that a straight line connecting the wheels is a triangle as shown in the figure. In this system, the front wheels are free-roller type, and steering is performed by the front wheels, and the two traveling wheels of the rear wheels are driving wheels of a mechanical power transmission system via differential gears, and the front wheels are made to travel along a guide. .

[0003]

In the system in which only the front wheels are steered and the rear wheels are driven to drive, the rear wheels cannot be freely steered. Therefore, when the vehicle is traveling, the vehicle can be bent at a right angle and can be accurately curved in a small-diameter curve. Was difficult.

The present invention provides an unmanned guided vehicle capable of independently steering four wheels, and obtains a differential speed as a function of a steering angle of two wheels whose driving wheels are controlled to follow a guide guide to obtain stable running. It is an object of the present invention to provide a four-wheel steering type automatic guided vehicle that improves the accuracy of following a guide.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and makes it possible to independently steer the four traveling wheels provided in an automatic guided vehicle and to arrange them on the diagonal line of the four wheels. Driving the two traveling wheels that have been driven to travel, and calculating the driving speed of the driving traveling wheels as a function of the steering angle of the two traveling wheels that are controlled so as to follow the guidance guide to control the differential speed. Is the gist.

[0006]

[Operation] Driving two traveling wheels diagonally arranged with respect to the vehicle body of a four-wheel steering type automatic guided vehicle, and the differential speed of the two driving wheels is a function of the steering angle of the wheels that follow the guide. Since the calculation and control are performed, the traveling of the automatic guided vehicle is stable, the tracking accuracy with respect to the guide guide is improved, and the automatic guided vehicle can travel accurately along the route. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A differential speed calculation method for a four-wheel steering type automatic guided vehicle according to the present invention will be described below with reference to the embodiments shown in the drawings.

Further, a guide sensor 7 is integrally provided on the right front traveling wheel 3 and a guide sensor 8 is integrally provided on the right rear traveling wheel 5, and when the traveling wheels 3, 5 change their directions, the guide sensor 7 is provided. , 8 are also mounted so as to turn together with the traveling wheels 3, 5.

The front and rear traveling wheels 4 and 6 on the left side of the truck 1 are steered, but no guide sensor is attached.

Since the carriage 1 of the automatic guided vehicle travels according to the guide 2, the guide sensor 7 integrated with the right front wheel 3 and the guide sensor 8 integrated with the right rear wheel 5 allow
In order that the deviation amounts δ3 and δ2 from the guide 2 become 0,
The steering motors (not shown) are controlled to change the steering angles φ3 and φ2 of the right traveling wheels 3 and 5, respectively.

When the steering angles φ3 and φ2 are determined, the steering angles φ1 and φ4 of the other two left and right traveling wheels are determined as follows. A turning radius ρ3 orthogonal to the steering angles φ3 and φ2
Letting C be the intersection of ρ2, the steering angles φ1, φ4 of the left wheel
Is determined so as to be orthogonal to the rotation radii ρ1 and ρ4.

By thus collecting four turning radii orthogonal to the arbitrary steering angles of all the four traveling wheels at one point C, the traveling wheel traveling directions V1 to V4 are orthogonal to the respective turning radii. Therefore, the sideslip (slip in each rotation radius direction) with respect to the ground on which the vehicle travels can be minimized.

Next, the relationship between the steering angles φ3, φ2 and φ1, φ4 is as shown in FIG.

[0014]

(Equation 1)

From equations (4) and (5), steering angles φ2 and φ3
Indicates that the steering angle φ4 is determined. Similarly, the relationship between the steering angles φ3, φ2 and φ1 is

[0016]

(Equation 2)

From the equations (4) 'and (5)', the steering angles φ2 and φ
When 3 is determined, φ1 is determined. Figure 1
Driving wheels 4 and 5 for driving are arranged on the diagonal line of the vehicle body of the automatic guided vehicle with respect to the driven wheels (driving wheels for non-driving) 3 and 6. The method of determining the peripheral velocities V1 and V2 of the driving traveling wheels in such an arrangement is to drive the wheels 4 and 5 with a minimum slip amount with respect to the ground.

Therefore, in the relationship diagram shown in FIG.

[0019]

(Equation 3)

The relationship between the outer wheel speed V2 and the inner wheel speed V1 is the rotational angular speed ω. Is common to all points of the automated guided vehicle body,

[0021]

(Equation 4)

The above equation shows a method of determining the differential speed V1 with respect to V2 according to the steering angles φ1 and φ2. Here, let the center speed of the automated guided vehicle be V

[0023]

[Formula 5]

From the equations (16), (6) and (7), V1 = f2 (φ1, φ2) V (17) where f2 (φ1, φ2) represents a function. Furthermore, φ1 is φ1 = f3 (φ2, φ3) from the equations (4) ′ and (5) ′ (18) where f3 (φ2, φ3) is a function. (17),
From equation (18), V1 = f4 (φ2, φ3) V (19)

Therefore, the traveling speed V of the automatic guided vehicle is determined from the equation (19), and the steering angle φ for following the guide tape is set.
When 2 and φ3 are determined, the speed V1 of the driving wheels arranged on the diagonal line may be determined by the equation (19), and V2 may be determined by the equation (15).

By the method of determining the differential speed as described above, (1) the differential speed during traveling by four-wheel steering is simple if only the two steering angles of the steered wheels that should follow the guide are determined. It becomes possible to decide. (2) Since the steering angle control for following the guidance guide may be controlled independently so that the deviation amount by the guide sensor of each steered wheel is always 0 regardless of the differential speed.
The control calculation for control can be simplified.

[0027]

EFFECTS OF THE INVENTION The differential speed calculation method for a four-wheel steering type automatic guided vehicle according to the present invention calculates the differential speed using the steered wheel steering angle that follows the guide guide among the four wheels. ) The control for following the guidance guide by the front and rear steering wheels can be made independent of the differential speed calculation, and the following accuracy is greatly improved. (2) The calculation of the differential speed of the two diagonal wheels can be made independent as a function of the steering angle of the two wheels, which simplifies the control device. And so on.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a wheel layout of a four-wheel steering type automatic guided vehicle of the present invention.

FIG. 2 is an explanatory diagram of a differential speed calculation method.

[Explanation of symbols]

 1 Automated guided vehicle body 2 Guidance guide 3 Driven wheels 4 Driven wheels 5 Driven wheels 6 Driven wheels 7 Right front wheel guide sensor 8 Right rear wheel guide sensor

Claims (1)

[Claims] 1. The four traveling wheels provided on the automatic guided vehicle can be independently steered, and the two traveling wheels arranged diagonally of the four wheels are driven to travel, and the driving traveling wheels are driven. A differential speed calculation method for a four-wheel steering automatic guided vehicle, which comprises calculating a speed as a function of a steering angle of two traveling wheels controlled to follow a guide and controlling a differential speed.