JPH0981240A - Method for controlling traveling of autonomously traveling automated guided vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an autonomously traveling automated guided vehicle capable of accurately moving its reference point to an optional destination at the time of traveling followed by directional change and having simple constitution in respect to a two-wheel driving type automated guided vehicle using a battery as a power source. SOLUTION: In this method, a controller rotates either one of right and left driving wheels 2b, 2a at first until auxiliary wheels 5a, 5b are turned up to almost horizontal directions when the traveling direction of a vehicle body 1 is changed from forward to backward or from backward to forward on the way of movement from the reference point up to an aimed position and then rotates the other driving wheel by the same rotational amount. Then the controller rotates the auxiliary wheels at first to turn the position of the vehicle body 1 in parallel with the initial position, calculated the deviation amount (x), (y) of the vehicle body 1 at the time of changing the direction and controls a DC motor so as to correct the deviation amounts (x), (y) to move the reference point to the aimed position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autonomous guided vehicle, and more particularly to an automated guided vehicle that can be accurately moved to any desired position.

[0002]

2. Description of the Related Art Unmanned guided vehicles are widely used for transporting and handling parts and products in factories, but unmanned guided vehicles accompanying changes in the manufacturing process in response to demands for manufacturing, product diversification, etc. It is necessary to change the traveling route of the car frequently. For this, an autonomous guided vehicle that does not require a taxiway and is easy to change the travel route is suitable.

An autonomous guided vehicle has data indicating a traveling route stored in a memory in advance, and controls the vehicle so that the vehicle is on a predetermined traveling route while detecting the current position of the vehicle by various sensors. Run while doing.

When a track-type automatic guided vehicle is run, it is possible to run by detecting the deviation from the track by the left and right track detection sensors and controlling the rotation of the left and right wheels. This type of technology is disclosed in, for example, Japanese Patent Laid-Open No. 5-324057
No., published in Japanese Unexamined Patent Publication No.

[0005]

However, in the case of running without a track like a robot wagon, it is necessary to make the running accuracy extremely high because there is no track detection sensor. Further, when traveling straight, turning, turning, etc., it is necessary to calculate all how to rotate the left and right wheels and rotate them exactly.

In the case of going straight, the amount of rotation can be easily obtained by dividing the amount of movement by the circumference of the wheel. Further, in the case of turning, since the rear wheel turns in the left and right directions on the circumference having the diameter of the pitch of the rear wheel, the amount of movement of the rear wheel can be easily obtained from the turning angle.

However, in the case of curve traveling, it is difficult to easily obtain it because the left and right driving wheels of the vehicle body have different amounts of rotation.

There is no problem when the traveling direction of the automatic guided vehicle is only forward or backward, but when the traveling direction is switched midway such as from forward to backward and from backward to forward, a flexible caster (auxiliary wheel) is midway. Due to the rotation of the car, the position of the vehicle body 1 is displaced. This is a phenomenon that occurs when the rotation of the caster is not known by the control system, and it is impossible to correct the deviation.

An object of the present invention is to accurately move a reference point of an automatic guided vehicle to an arbitrary target position in a two-wheel drive type automatic guided vehicle using a battery as a power source when traveling with a direction change. It is an object of the present invention to provide an unmanned guided vehicle of an autonomous traveling system which is capable of performing and has a simple structure.

[0010]

The features of the present invention are a DC motor for driving a pair of drive wheels, which are mounted at symmetrical positions of a vehicle body, an auxiliary wheel, and a battery as a power source. -, A rotary encoder for detecting the number of rotations of the driving wheels, and a controller for outputting a rotation pulse and a rotation direction of the DC motor as command values based on control information and an output signal of the encoder. In the traveling control method for the autonomous guided vehicle, the controller is such that when the vehicle body is moved from the reference point to the target position, the traveling direction is switched from forward to backward or backward to forward. In some cases, one of the left and right drive wheels is first rotated until the auxiliary wheel is in a substantially horizontal direction, and then the other drive wheel is rotated by the same amount. The auxiliary wheels are rotated first to bring the position of the vehicle body parallel to the initial position, the displacement amounts x and y of the vehicle body at the time of the direction change are calculated, and the displacement amounts x and y are corrected. To control the DC motor,
It is to move the reference point to the target position.

[0011]

According to the present invention, a DC motor for driving a pair of driving wheels mounted symmetrically with respect to the center line in the front-rear direction of the vehicle body and an encoder for detecting the rotational speed of the driving wheels. In the case of the one having a dash, the reference point of the vehicle body can be accurately moved to a target position separated by a predetermined distance. In particular, accurate position control becomes possible by calculating the displacements x and y of the vehicle body at the time of turning, and correcting the displacements when traveling thereafter.

When this method is applied to a relatively simple moving device such as a bed / wagon, the front wheel control is not required, so that the cost can be reduced and the power consumption can be reduced, so that the method can be used in various applications. It is possible.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.
First, FIG. 1 is a view conceptually showing a back surface of a vehicle body 1 of an automated guided vehicle according to an embodiment of the present invention. This automated guided vehicle is
It is a rear-wheel drive type automated guided vehicle. Drive wheels 2a and 2b are attached to the rear portion of the vehicle body 1 at symmetrical positions. DC motors 3a and 3b for driving the drive wheels 2a and 2b are provided with rotary encoders 4a and 4b for detecting the rotational speed of the drive wheels. 5
Is a universal caster (auxiliary wheel), and 6 is a controller. The traveling distance and the vehicle body angle of the vehicle body 1 are determined by the encoder 4a,
It is detected by the controller 6 based on the output signal of 4b.
The vehicle body 1 is equipped with a battery as a power source for the DC motor (not shown).

The controller 6 is constructed as shown in FIG. That is, the microcomputer 61
A movement amount command and detection values of the rotary encoders 4a and 4b are received as inputs from a host (main) computer (not shown), and the position of the auxiliary wheel 5 is used as a reference point.
Is output to the spindle motor amplifier 62 as command values so as to drive the DC motors 3a and 3b so as to obtain the vehicle body angle after the vehicle body 1 is moved. . Information such as the moving course and the current position of the vehicle body 1 is held in the main computer.

Next, the control operation of the vehicle body 1 by the controller 6 will be described with reference to the vehicle body positional relationship diagram of FIG. 3 and the control flow of FIG. This control is based on the drive wheel position 2 in FIG.
When moving the reference points 5 of the triangles 5a, 2b connecting the a, 2b and the reference points 5 to the target position 5'distance M in the direction of the angle θ (front right), the drive wheels 2a, 2b are moved. It asks how much should be moved.

In the main computer, first, the vehicle body 1
It is checked whether the posture (vehicle body angle) is within a predetermined range with respect to the traveling direction, for example, within 30 ° to the left and right (step 402). If the angle of the vehicle body 1 is not within 30 ° from the left and right, the DC motors 3a and 3b are driven to turn the vehicle body 1 within 30 ° (step 40).
4).

Next, the controller 6 receives information about the traveling direction and traveling distance of the vehicle body 1 from the main computer, that is, data on the traveling angle θ and traveling distance M from the current position to the traveling direction (step 406).

Next, the controller 6 calculates the position of the turning center Z of the vehicle body 1 (step 408). here,
The center Z of rotation when the reference point 5 of the triangles 5 2a 2b moves to the target position 5 ′ is the perpendicular line extending from the center point of the reference point 5 and the target position 5 ′ and the positions 2a and 2b of the drive wheels. This is the point where the extension lines intersect.

Next, the controller 6 obtains the turning amount θx of the vehicle body 1 by the method described below (step 41).
0).

First, if either of the front and rear directions of the drive wheels 2a and 2b and the reference point 5 is set to H, the moving turning radius (SZ) of the center point of the drive wheels 2a and 2b is the side 5B of the triangle 5AB in FIG. And the side CZ of the triangle BCZ. The side 5B = M / 2 * cosec θ. It is calculated by the side ZC = H * cotθ. Side SZ = side 5B + side CZ = M / 2 * cosec θ + H * cot θ = M * cosec θ / 2 + H * cos θ / sin θ = (M + 2H * cos θ) / (2 * sin θ)

Therefore, the radius of gyration of movement of the drive wheel 2a is the side 2
aZ = side SZ + side 2a2b / 2, and the moving radius of rotation of the drive wheel 2b is obtained by side 2bZ = side SZ−side 2a2b / 2.

Further, the movement angle and the vehicle body angle after movement are θX.
= ΘY = θZ Here, θY = ARCTAN ((H + Mcosθ) / (side SZ-Msinθ)) = ARCTAN ((H + Mcosθ) / (((M + 2Hcosθ) / (2sinθ))-Msinθ)) = ARCTAN ((H + Mcosθ) / ((M + 2Hcosθ-2Msinθ * sinθ) / 2sinθ)) = ARCTAN ((2sinθ (H + Mcosθ) / ((M + 2Hcosθ-2M (1-cosθ * cosθ))) = ARCTAN ((2sinθ (H + Mcosθ)) / (2cosθ (H + Mcosθ) -M)) In addition, θZ = ARCTAN (H / side SZ) = ARCTAN (H / ((M + 2Hcosθ) / 2sinθ)) = ARCTAN (2Hsinθ / ( M + 2cos θ)) Next, the rotation amounts R and L of the left and right rear wheels are obtained (step 4
12). The moving distance (R) of the right wheel when moving the reference point 5 to the target position 5 ′ moves by θX on the circumference having the radius of the side 2b2, so R = 2 * side 2bZ * π * θX / Required by 360.

Further, the moving distance (L) of the left wheel moves by θX on the circumference having the radius of the side 2aZ, so that L = 2 * side
It is calculated by 2aZ * π * θX / 360.

Next, the one with the larger amount of rotation is the main wheel and the one with the smaller amount of rotation is the slave wheel (step 414), and the main wheel and the slave wheel are rotated at the set speed (step 416).

Further, the amount of rotation of the slave wheel is detected and compared with a calculated value. When the amount of slave wheel is large, the rotation of the slave wheel is stopped, and when it is small, it is rotated, and this process is repeated until the master wheel rotates by the set amount. When the wheel has rotated by the set amount, the main wheel is stopped (steps 418 to 422).

Then, the driven wheel is rotated, and when the rear wheel has rotated by the set amount, the driven wheel is stopped (steps 424 to 42).
8).

When the vehicle moves to the right front, it moves without any problem in the calculation of R and L in step 412, but in the other directions, it moves, but it is unnatural as an automated guided vehicle. It will be in motion. That is, the operation is similar to turning.

Therefore, in such a case, if the traveling direction is smaller than 90 °, the calculation is performed as it is. When the traveling direction is 90 ° <θ <180 °, (180 °
-Θ) is replaced with θ, and the left and right rear wheels are reversed.

When the traveling direction is 270 ° <θ <360 °, (360 ° -θ) is replaced with θ and the rotation amount of the left rear wheel and the rotation amount of the right rear wheel are exchanged for normal rotation. .

When the traveling direction is 180 ° <θ <270 °, (θ-180 °) is replaced with θ, and the rotation amount of the left rear wheel and the rotation amount of the right rear wheel are replaced and both are reversed.

That is, when moving to the rear right, (18
(0 ° -running direction) is replaced with the running direction, the same calculation is performed, and when the left and right wheels are rotated and moved in reverse, the reference point 5
Can be moved to the target position 5'by retreating.

When moving to the left front, (360 °
-When the traveling angle) is replaced with the traveling angle, the calculation is performed, and the left and right wheels are moved in the opposite amounts, the reference point 5 can be moved to the target position 5 '.

Further, when moving to the left rear, (running direction −180 °) is replaced with the running direction, the same calculation is performed,
It is possible to move the reference point 5 to the target position 5'by reversing the movement amount of the left and right wheels, rotating the wheels in the opposite direction, and backward turning left.

In this way, the reference point 5 is moved to the target position 5'by rotating the drive wheels 2a, 2b by the moving distances R and L in the above manner. However, at this time, the drive wheel 2a (2b) must rotate at a constant rate with respect to 2b (2a).

Normally, in such a case, the driving motor-3
It is a general method to construct a servo system in a and 3b and rotate them at a constant speed by a speed control.

In the case of the present invention, since the battery is used as the drive source, the power consumption is suppressed and the drive wheel 2 is used.
In order to keep the rotation ratios of a and 2b more accurate, the processing flow is as shown in the above step 414 and thereafter.

That is, of the drive wheels 2a and 2b, the one having the longer travel distance is the main wheel and the one having the smaller travel distance is the slave wheel, and the ratio of the slave wheel / main wheel travel distance is calculated in advance and used for the master wheel and the slave wheel. The drive motors 3a and 3b are rotated at a designated speed. At this time, the rotation speed of the main wheel is set to the encoder 4a (4
b), read the value, multiply the value by the ratio (subordinate wheel / main wheel), and compare the encoder 4b (4a) of the secondary wheel with
When the amount of rotation of the driven wheel is large, the driven motor for the driven wheel-3a (3
By turning off the rotation of b) and turning it on at high speed when it is small, it is possible to always keep the rotation ratio of the main wheel and the sub-wheel close to the ideal state.

In the case of straight traveling, the drive motors 3a and 3b are rotated at a designated speed, and the rotation speed is changed to the encoder 4a,
It is possible to make the rotation amounts of the left and right drive wheels 2a and 2b always the same by reading at 4b and turning off the rotation of the drive motor having the larger rotation amount at high speed.

In the case of this system, the minimum electric power required for moving the automatic guided vehicle is sufficient, and the consumption of the battery can be suppressed.

There is no problem if the traveling direction is forward only or backward only in the above step 414, but when the traveling direction is switched midway such as forward to backward and backward to forward, the flexible caster 5 is in the middle. The position of the vehicle body 1 is displaced due to the rotation. This is a phenomenon that occurs when the rotation of the caster is not known by the control system, and it is impossible to correct the deviation.

Therefore, it is desirable to carry out this correction before the processing of step 414 and thereafter. This correction is shown in FIG.
This will be described with reference to FIG. In the example of the figure, there are two free casters, the left and right 5a and 5b, but there is no difference from the case of one. In the correction, in order to forcibly rotate the caster 5 by changing the direction of the vehicle body 1 from the state of FIG. 6 (A), as shown in FIG. 6 (B), the drive wheel 2a, 2b on either the left or right side is moved first. Then, rotate the caster 5 until it faces straight. As a result, the vehicle body moves to the 1'position. Then, as shown in FIG. 6C, the other drive wheel is rotated by the same amount to rotate the caster first. As a result, the car body moves to the 1 "position.

In FIG. 5, the distance between the drive wheels 2a and 2b is PW (mm) The distance between the center of the drive wheels and the center of the caster axis is H (mm) The distance between the center of the caster axis and the center of the mounting axis is e (mm ) The turning angle of the vehicle body due to turning is θa. The deviation of the vehicle body to the front is x (mm), and the deviation of the vehicle body to the left (right) is y (mm). Θa = arccos (H / (he)) x = PW-PW cos θa y = PW sin θa Thus, the displacements x and y of the vehicle body 1 at the time of changing the direction are calculated, and corrective control can be performed by correcting the displacements when traveling thereafter.

When this method is applied to a relatively simple moving device such as a bed and a wagon, front wheel control is not required, so that the cost can be reduced and the power consumption can be reduced, so that it can be used in various applications. It is possible.

Needless to say, the present invention can also be applied to a front wheel drive type automatic guided vehicle.

[0045]

According to the present invention, a DC motor for driving a pair of drive wheels mounted symmetrically with respect to the center line in the front-rear direction of the vehicle body and the rotational speeds of the drive wheels are detected. In a vehicle having an encoder, the reference point of the vehicle body can be accurately moved to a target position separated by a predetermined distance. In particular, accurate position control becomes possible by calculating the displacements x and y of the vehicle body at the time of turning, and correcting the displacements when traveling thereafter.

When this method is applied to a relatively simple moving device such as a bed and a wagon, front wheel control is not required, so that the cost can be reduced and the power consumption can be reduced. It is possible.

[Brief description of drawings]

FIG. 1 is a view conceptually showing a back surface of a vehicle body 1 of an automated guided vehicle according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a controller shown in FIG.

3 is a vehicle body positional relationship diagram for explaining a vehicle body control operation by the controller of FIG. 1. FIG.

FIG. 4 is a control flow showing a control operation of a vehicle body by the controller of FIG.

FIG. 5 is an explanatory diagram of vehicle body position deviation correction when switching the traveling direction to either forward or backward.

FIG. 6 is an explanatory diagram of an operation for correcting the displacement of the vehicle body position in FIG.

[Explanation of symbols]

1 ... vehicle body, 2a, 2b ... drive wheels, 3a, 3b ... direct current mode
4a, 4b ... Rotary encoder, 5 ... Flexible casters (auxiliary wheels), 6 ... Controller

Claims (2)

[Claims] 1. A pair of drive wheels mounted at symmetrical positions on a vehicle body, an auxiliary wheel, a DC motor for driving the drive wheels using a battery as a power source, and the rotational speeds of the drive wheels. Travel control in an autonomous guided vehicle that includes a rotary encoder for detection and a controller that outputs a rotation pulse and a rotation direction of the DC motor as command values based on control information and an output signal of the encoder. In the method, when the controller moves the vehicle body from a reference point to a target position, when the traveling direction is switched between forward and backward or backward and forward, the drive wheel on either the left or right side is changed. First until the auxiliary wheel is oriented almost laterally, then the other drive wheel is rotated by the same amount to rotate the auxiliary wheel first, and The position is made parallel to the initial position, the displacement amounts x and y of the vehicle body at the time of the direction change are calculated, and the DC motor is controlled so as to correct the displacement amounts x and y. A traveling control method in a self-propelled automatic guided vehicle, wherein the reference point is moved to the target position. 2. The traveling control method for a self-propelled automatic guided vehicle according to claim 1, wherein the controller obtains a traveling angle θ and a traveling distance M of the vehicle body in the traveling direction as the control information, and stores the control information in the control information. Based on the control information and the displacement amounts x and y of the vehicle body, the position of the turning center Z of the reference point on the vehicle body is obtained based on the drive, and the drive required to move the reference point to the target position. The rotation amounts R and L of the wheels are obtained by calculation, the one having the larger rotation amount is the main wheel and the one having the smaller rotation amount is the slave wheel, the rotation ratio of the slave wheel / main wheel is previously calculated, and the main wheel and the slave wheel are set at the set speed. Rotate, and further detect the amount of rotation of the driven wheel,
When this is compared with the rotation ratio and is larger than the ratio, the rotation of the slave wheel is stopped, and when it is small, it is rotated, and this process is repeated until the main wheel reaches the set rotation amount,
A self-propelled type characterized in that when the main wheel reaches the set rotation amount, the main wheel is stopped, then the slave wheel is rotated, and when the slave wheel rotates by the set amount, the slave wheel is stopped. Driving control method for automatic guided vehicle.