JP2002373023A - Automatically guided cargo vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatically guided cargo vehicle, which can stably travel all the time by suppressing the shaking of a car body while traveling. SOLUTION: In the automatically guided cargo vehicle to be steered to travel along a guideline 5 laid on the surface of a road, line detecting means 6 and 7 for detecting the guideline 5 are respectively provided on the front side and rear side of a car body 1. Furthermore, a control means 10 is provided for calculating the displacement quantity Y0 of a virtual point P0 preset on the front side of the car body 1 in the traveling direction from the guideline 5 on the basis of the detection output of each of two line detecting means 6 and 7 and controlling steering of the car body 1 so that the calculated displacement quantity Y0 is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic guided cargo handling vehicle that travels along a guideway laid on a road surface.

[0002]

2. Description of the Related Art Automated warehouses and the like employ an unmanned transport system. In such an unmanned transport system, a guide line is laid on a road surface in advance, and an automatic route is provided along the guide line. 2. Description of the Related Art Autonomous traveling of guided cargo handling vehicles (for example, unmanned forklifts and unmanned transport vehicles) has been performed.

FIG. 5 is a plan view showing a schematic configuration of an unmanned forklift as an example of such a conventional automatic guided cargo handling vehicle. In this unmanned forklift, a pair of forks 2 is provided in front of a vehicle body 1 so as to be able to move up and down. The vehicle body 1 is provided with a pair of left and right traveling wheels 3 on the front side, and one drive steering wheel 4 on the rear side, and a guide line 5 laid on the road surface on the front side of the vehicle body 1. A magnetic sensor 6 as a line detecting means for detecting is installed. Further, the vehicle body 1 incorporates a traveling device for driving and driving the driving steered wheels 4 and a steering device for steering (both are not shown), and a control device 10 such as a microcomputer for controlling these devices. .

The above-mentioned guide line 5 is made of a magnet, such as a magnetic tape, and the magnetic sensor 6 has, for example, a plurality of Hall elements arranged in parallel by a predetermined length along the width direction of the vehicle body. A signal having a different voltage value is output according to the position where the guide line 5 crosses.

[0005] In such an unmanned forklift, in order to autonomously travel along the guide line 5, conventionally,
The following control is performed. For example, assuming that the unmanned forklift is traveling forward in the direction indicated by the arrow F in FIG. 5, the control device 10 first reads the detection output of the magnetic sensor 6 as shown in the flowchart of FIG. Step 10), the central part P1 of the magnetic sensor 6
Then, a displacement Y1 displaced from the guide line 2 is calculated (step 11).

Next, a steering angle θ of the steering device is calculated from the displacement Y1 based on, for example, the following equation (step 12). θ = K · Y1 (1) Here, K is a conversion coefficient from a displacement amount to an angle.

Subsequently, the control device 10 controls the steering motor of the steering device (not shown) to change the direction of the drive steered wheels 4 by an angle corresponding to the steering angle θ obtained by the above equation (1) (step 1). 13).

Therefore, for example, as shown in FIG. 5, if the central portion P1 of the magnetic sensor 6 is displaced by Y1 to the right with respect to the traveling direction from the guide line 5, the drive steered wheels 4 will not be driven by the rear wheels. In this case, the vehicle body 1 is rotated clockwise by an angle θ corresponding to the displacement amount Y1, and as a result, the vehicle body 1 turns counterclockwise. Naturally, if the central portion P1 of the magnetic sensor 6 is displaced leftward from the guide line 5 with respect to the traveling direction, the operation reverses to the above.

As described above, in the prior art, the steering angle θ is determined based on the displacement Y1 of the central portion P1 of one magnetic sensor 6 from the guide line 5, and the attitude of the vehicle body 1 is corrected by the angle θ. Meanwhile, control is performed such that the vehicle travels along the guide line 5.

[0010]

However, such a conventional automatic guided cargo handling vehicle detects a displacement Y1 from the central portion P1 of the magnetic sensor 6 provided on the front side of the vehicle body 1 to the guide line 5. When the steering control of the vehicle body 1 is performed so that the displacement amount Y1 becomes zero, the swing (the amount of change in angle) of the vehicle body 1 becomes large as shown by the broken line in FIG. Become. Therefore, the center O of the vehicle body 1 protrudes greatly from the guide line 5.

That is, conventionally, the central portion P of the magnetic sensor 6 is
When the vehicle 1 crosses the guide line 5 and a displacement is generated on the left side with respect to the traveling direction, the real-time control is performed to reverse the direction of the vehicle body 1 so as to immediately cancel the displacement. Will be. In such real-time control, the fact that the vehicle body 1 has an inertia force,
The timing of the change of direction is delayed, and it protrudes. Then, once the protrusion occurs, it takes a long time until the vibration of the vehicle body 1 converges. For this reason, in the conventional automatic guidance type cargo handling vehicle, it was difficult to perform a stable traveling with a small swing of the vehicle body 1.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an automatic guided cargo handling vehicle capable of always keeping a stable running while suppressing the swing of the vehicle body during running. I do.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an automatic guided cargo handling vehicle which is steered to travel along a guide line laid on a road surface. I have to.

That is, according to the first aspect of the present invention, the front and rear sides of the vehicle body are each provided with line detecting means for detecting the guide line, and based on the detection output of each of the two line detecting means. And calculating control means for calculating a displacement amount of the virtual point set in advance on the front side in the traveling direction of the vehicle body from the guide line, and controlling the steering of the vehicle body so that the calculated displacement amount becomes small. I have.

Thus, the displacement of the virtual point set in front of the vehicle body from the guide line is obtained, and the direction of the vehicle body is controlled based on the amount of the displacement. Compared with this, the vibration of the vehicle body can be suppressed to a small value, and the vibration of the vehicle body is converged within a short time, so that the vehicle can always run stably.

According to a second aspect of the present invention, in the configuration of the first aspect, the imaginary point is a fork attached to a front portion of the vehicle body with a center line connecting the central portions of the two line detecting means. Are set in the vicinity of the position of the intersection with the line connecting the tips.

Thus, since the tip of the fork is controlled so as to be substantially parallel to the guide line, the load placed on the fork is loaded on a rack or the like, and the load on the rack is loaded. In this case, the positioning accuracy is improved.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this embodiment, an unmanned forklift will be described as an example of the automatic guided cargo handling vehicle.

FIG. 1 is a plan view showing a schematic configuration of an unmanned forklift according to an embodiment of the present invention, and FIG. 2 is a block diagram of an operation control system. Components corresponding to those in FIG. 5 are denoted by the same reference numerals. .

In these figures, reference numeral 1 denotes a vehicle body, 2 denotes a pair of forks, 3 denotes a pair of running wheels, 4 denotes a driving steering wheel,
Reference numeral 5 denotes a guide line, and these components are basically the same as the conventional one shown in FIG. Numeral 8 denotes the drive steering wheel 4
Is a steering device that steers the drive steered wheels 4, and 10 is a control device such as a microcomputer that controls these devices 8, 9. In this embodiment, magnetic sensors 6 and 7 are provided on the front side and the rear side of the vehicle body 1 as line detecting means for detecting the guide line 5, respectively.

The control device 10 corresponds to the control means in the claims, and includes an arithmetic control unit 11 and a memory 12. The arithmetic control unit 11 controls the traveling device 8 and controls the steering device 9 based on the detection output of each of the two magnetic sensors 6 and 7 as described later in detail. In addition, the memory 12 stores data detected by the magnetic sensors 6 and 7, an arithmetic expression for obtaining the steering angle θ of the steering device 9, data of the calculation result, and the like.

Next, the operation of the steering control in the control device 10 when the unmanned forklift having the above-described configuration allows the autonomous traveling along the guide line 5 will be described with reference to the flowchart shown in FIG.

For example, assuming that the unmanned forklift is traveling forward in the direction indicated by arrow F in FIG.
The control device 10 first takes in the detection outputs of the magnetic sensors 6 and 7 before and after the vehicle body 1 (step 0).

The arithmetic and control unit 11 controls each of the magnetic sensors 6 and
Based on the detection output of 7, the displacement amounts Y1, Y2 of the central portions P1, P2 of the magnetic sensors 6, 7 from the guide line 2 are obtained (steps 1, 2).

Next, an intersection point between a center line M connecting the central portions P1 and P2 of the two magnetic sensors 6 and 7 and a line connecting the tips of the pair of forks 2 is defined as a virtual point P0, and the following displacement amount is set. Find Y0.

That is, the arithmetic control unit 11 calculates the displacement amounts Y1 and Y2 and the respective dimensions L of the vehicle body 1 and the fork 2.
Based on the proportional relationship between L1 and L2, the displacement Y0 of the virtual point P0 imagined as described above from the guide line 5 is calculated based on the following equation (2) (step 3). Y0 = (L2 / L1) · (Y1-Y2) + Y1 (2)

Subsequently, the arithmetic and control unit 11 calculates the steering angle θ of the steering device 9 from the displacement Y0 obtained by the above equation (2) based on the following equation (3) (step 4). θ = K · Y0 (3) Here, K is a conversion coefficient from a displacement amount to an angle.

The arithmetic control unit 11 controls a steering motor (not shown) of the steering device 9 to drive the steered wheels 4 by an angle corresponding to the steering angle θ obtained by the above equation (3).
Is changed (step 5).

That is, as shown in FIG.
Is displaced leftward from the guide line 5 by Y0 with respect to the traveling direction, the driven wheel 4 is rotated counterclockwise by an angle θ corresponding to the displacement Y0 because the rear wheel is driven.
As a result, the vehicle body 1 turns clockwise. That is, the direction is changed so that the center O of the vehicle body 1 approaches the guide line 5.

When the virtual point P0 crosses the guide line 5 and is displaced to the right with respect to the traveling direction, the direction of the vehicle body 1 is reversed so as to immediately cancel the displacement. Will be controlled.

As described above, since the virtual point P0 serving as a reference for the steering control of the vehicle body 1 is set at the front position of the vehicle body 1, the direction change of the vehicle body 1 requires that the vehicle body 1 be positioned at the virtual point P0. It will be started before it actually reaches. That is, it is a kind of predictive control. Therefore, the timing of the turning of the vehicle body 1 is not delayed as in the related art,
The phenomenon that the center O of the vehicle body 1 protrudes greatly from the guide line 5 as in the related art is suppressed, and as shown by the solid line in FIG. 4, the vibration of the vehicle body 1 decreases and the vibration converges in a short time. For this reason, stable running can always be performed.

In particular, as in the example shown in FIG. 1, the imaginary point P0 at the tip of the fork 2 is the intersection of the center line M connecting the central parts P1 and P2 of the two magnetic sensors 6 and 7 with the guide line 5. When it is located forward of Q, the displacement Y of each of the central portions P1 and P2 of the magnetic sensors 6 and 7 to the guide line 5 is determined.
1, Y2, and the displacement Y0 of the virtual point P0 to the guide line 5 are opposite to the left and right with respect to the traveling direction.
Is displaced from the guide line 5, the control device 10
Accordingly, the direction is changed so that the center O of the vehicle body 1 approaches the guide line 5, so that the center O of the vehicle body 1 protruding from the guide line 5 can be further reduced, which is convenient.

FIG. 1 shows an example in which the displacements Y1 and Y2 of the magnetic sensors 6 and 7 up to the guide line 5 and the displacement Y0 of the virtual point P0 up to the guide line 5 are reversed left and right with respect to the traveling direction. Where the displacements Y1 and Y2 of the magnetic sensors 6 and 7 up to the guide line 5 and the displacement Y of the virtual point P0 up to the guide line 5 are obtained.
0 is located on the same side (for example, right side) with respect to the traveling direction, the drive steering wheel 4 is rotated clockwise by an angle corresponding to the displacement Y0. 1 changes its direction counterclockwise, so that the center O of the vehicle body 1 approaches the guide line 5.

Further, as in this embodiment, a center line M connecting the central portions P1 and P2 of the two magnetic sensors 6 and 7 is used.
When the position of the intersection between the fork 2 and the line connecting the tips of the pair of forks 2 is set as the virtual point P0, the tip of the fork 2 is controlled so that it is always substantially parallel to the guide line 5; It is possible to improve the positioning accuracy when the load placed on the rack is loaded on a rack or the like or when the load on the rack is unloaded.

When one or both of the magnetic sensors 6 and 7 deviate from the guide line 5, the operation can be continued as it is.
It is preferable to stop the unmanned forklift emergency.

With respect to the above embodiment, the following modifications and applications can be considered. (1) In the above embodiment, the virtual point P0 is made to coincide with the position of the approximate tip of the fork 2 in consideration of the positioning accuracy when handling the luggage, but the center O of the vehicle body 1 protrudes from the guide line 5. In the case where control is performed to keep the value of the virtual point P small, the above-mentioned restriction does not exist, and the virtual point P0 may be set at a position in front of the vehicle body 1.

(2) In the above embodiment, the virtual point P0 is always set at a constant position regardless of the traveling speed of the vehicle body 1, but the position of the virtual point P0 is Is more preferable because the delay in the timing of the direction change of the vehicle body 1 can be further reduced.

(3) In the above-described embodiment, an unmanned forklift has been described as an example of the automatic guided cargo handling vehicle. However, the present invention is not limited to this, and may be applied to an unmanned guided vehicle. The present invention can be widely applied to any cargo handling vehicle that can be guided along the guide line 5.

[0039]

According to the automatic guided cargo handling vehicle of the present invention,
The following effects are obtained. (1) According to the first aspect of the present invention, the displacement amount of the virtual point set in advance in the traveling direction of the vehicle body from the guide line based on the detection outputs of the pair of line detection means provided before and after the vehicle body. Is calculated, and the steering device is controlled so that the calculated amount of displacement becomes small. Therefore, it becomes a kind of predictive control, and the vibration of the vehicle body can be suppressed smaller than in the past, and the vibration of the vehicle body is shorter. Converges within
It is possible to always perform stable running.

(2) According to the second aspect of the present invention, the virtual point is an intersection of a center line connecting the central portions of the two track detecting means and a line connecting the tips of the forks attached to the front portion of the vehicle body. Since it is set near the position, in addition to the effect of the invention described in claim 1 or claim 2, since the tip of the fork is controlled so that it is always substantially parallel to the guide line,
Luggage placed on a fork can be loaded on a rack, etc.
The positioning accuracy when loading the load on the rack is improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of an unmanned forklift according to an embodiment of the present invention.

FIG. 2 is a block diagram of an operation control system of the unmanned forklift according to the embodiment of the present invention.

FIG. 3 is a flowchart for explaining a steering control operation of the unmanned forklift according to the embodiment of the present invention.

FIG. 4 is a time chart showing a comparison of the state of vibration of the vehicle body between the steering control of the unmanned forklift according to the embodiment of the present invention and the conventional steering control.

FIG. 5 is a plan view showing a schematic configuration of a conventional unmanned forklift.

FIG. 6 is a flowchart for explaining a steering control operation of a conventional unmanned forklift.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 2 Fork 5 Guidance line 6 Magnetic sensor (track detection means) 7 Magnetic sensor (track detection means) 9 Steering device 10 Control device (control means)

Claims (2)

[Claims] 1. An automatic guided cargo handling vehicle that is steered to travel along a guide line laid on a road surface, wherein line detecting means for detecting the guide line is provided on a front side and a rear side of a vehicle body, respectively. On the other hand, based on the detection output of each of the two track detecting means, a displacement of the virtual point set in advance in the traveling direction of the vehicle body from the guide line is calculated, and the calculated displacement is calculated. An automatically guided cargo-handling vehicle, comprising: control means for steering-controlling the vehicle body so as to be smaller. 2. The virtual point is set near an intersection of a center line connecting the central portions of the two track detecting means and a line connecting the tips of forks attached to the front of the vehicle body. 2. The automatic guided cargo handling vehicle according to claim 1, wherein: