JP2002166739A - Slip detecting and eliminating device for automated guided vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for earlier detecting the slip of the wheel of an automated guided vehicle having a large number of axles driven independently by hydraulic motors for independent steering and immediately eliminating the slip if detected. SOLUTION: A rotation detector 15 is installed on each axle. In traveling on a straight lane, an averaged number of rotations is obtained from the number of rotations of each axle and, when there is the number of rotation higher by a specified value than the averaged number of rotation, the axle is judged to be in a slip state. In traveling on a curved lane, the number of rotations of each axle is compared with an allowable number of rotations according to a steer angle and, when there is the number of rotation out of the allowable number of rotations, the axle is judged to be in a slip state. When the axle is judged to be in a slip state, a traveling speed is lowered to eliminate the slip state.

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 having a plurality of axles independently driven by a hydraulic motor and independently steerable, and more particularly to a device for detecting wheel slip and eliminating the slip. .

[0002]

2. Description of the Related Art There is known a vehicle for transporting heavy goods on a factory premises, which is provided with a number of axles which are independently driven by a hydraulic motor and can be independently steered, and are capable of not only moving forward and backward, but also traversing or sloping. Have been.

[0003] Further, in steel works, heavy objects such as coils and large steel materials are placed on a pallet having legs, and are transported by a transport vehicle capable of loading and unloading by themselves. As shown in FIG. 4, the transport vehicle includes a plurality of axles that are independently driven by a hydraulic motor and can be independently steered, and are attached to a frame via an arm 3. It is configured so that it can be changed.

When a heavy object is to be conveyed, the lifting cylinder 4 is contracted and the carrier 1 of the carrier is lowered to sink into the pallet legs, and the carrier 1 is raised to carry the pallet. . As shown in FIG. 5, the power system of this transport vehicle includes hydraulic pumps 6 and 7 driven by an engine 9 and supplies hydraulic oil from a variable discharge type hydraulic pump 7 to a hydraulic motor 8 provided on each axle for traveling. For steering, hydraulic oil is supplied from a hydraulic pump 6 to a steering cylinder 5 provided on each axle, and for lifting and lowering of the cargo bed, hydraulic oil is supplied from a hydraulic pump 6 to a lifting cylinder 4 provided on each axle. The operation of these actuators is controlled by a hydraulic control device 10 provided in the cab.
Depending on the order from Specifically, the traveling speed is controlled by instructing a solenoid valve 13 that changes the discharge amount of the hydraulic pump 7, and when traveling on a curve, the steering angle of each wheel is calculated based on the curve information, and each steering cylinder is controlled. By instructing each electromagnetic valve 11 provided in the hydraulic path No. 5 to rotate each wheel to a predetermined steering angle. When the loading platform 1 is moved up and down, each solenoid valve 1 provided in the hydraulic path of each lifting cylinder 4
2. Although not shown, the hydraulic motor 8
The electromagnetic switching valve for reversing the hydraulic pump 7 and the hydraulic motor 8
And can travel at the same speed in reverse as in forward travel.

[0005]

In recent years, from the viewpoint of rationalization of physical distribution in factories, there has been a demand to operate a transport vehicle unattended. By the way, the automatic guided vehicle needs to travel on a commanded traveling route with high accuracy, and in particular, must be guided with high accuracy in a narrow passage or the like.

[0006] Therefore, it is necessary to detect slippage due to unevenness of the road surface, uneven load, or the like at an early stage, and if slippage is detected, to quickly eliminate the slippage so that the state is not continued. However, in a transport vehicle having a large number of axles independently driven by a hydraulic motor and capable of independent steering, there are many factors that cause slippage, so that it is difficult to predict the slippage, and there is a problem that the slippage cannot be detected unless the slipping state is continued to some extent. .

Accordingly, the present invention provides an apparatus for early detecting wheel slip of an automatic guided vehicle having a large number of axles independently driven by a hydraulic motor and capable of independent steering, and an apparatus for immediately canceling the slip when the slip is detected. It is intended to be.

[0008]

Means for Solving the Problems In order to achieve the above object, the invention of claim 1 employs the following means. That is, this is a slip detection device in an automatic guided vehicle provided with a large number of independently driven axles that are independently driven by a hydraulic motor, and provided with a rotation detector on each axle. A rotation speed higher than the average rotation speed by a predetermined value is determined as a determination value, and the rotation speed of each axle is compared with the determination value.If there is an axle with a rotation speed higher than the determination value, it is determined that the vehicle is in a slip state. The rotation speed of the axle is compared with an allowable rotation speed corresponding to the steering angle, and when there is a rotation speed outside the allowable rotation speed, a slip state is determined.

The slip detection device for an automatic guided vehicle according to the present invention is applied to a device in which a hydraulic motor is attached to each axle and driven independently, and each axle can be independently steered, except for a device driven by an electric motor. I will Normally, unmanned guided vehicles supply hydraulic oil to each hydraulic motor via a pipe branched from a hydraulic pump, so the load tends to be unbalanced on each axle due to irregularities on the road surface, etc. Are supplied. Therefore, the number of rotations of the axle with a small load increases, and the wheels often slip.

According to the present invention, the rotational speed of each axle is detected during straight running, and a vehicle that is higher than the average rotational speed by a predetermined value or more is determined as a slip state. The predetermined value may be an appropriate value depending on the transport vehicle, the traveling route, the transported cargo, and the like.
It is good to make it double, and to correct it according to the result of conveyance.

When the vehicle is traveling on a curve, the steering angle of each wheel changes according to the curve, and the load varies. Therefore, the range of the number of rotations at which the slip corresponding to the steering angle does not occur is set in advance as an allowable range. It is checked whether or not the rotation speed is within the allowable range, and those outside the range are determined to be in the slip state. When the steering angle is small, it may be treated in the same way as straight running.

A second aspect of the present invention is to eliminate the slip state detected in the first aspect of the present invention, and to reduce the amount of pressure oil supplied to a hydraulic motor for driving each axle. It is characterized by. As a result, the traveling speed is reduced, the contact between the wheels and the road surface is increased, and the slip state can be eliminated.

As a means for reducing the supply amount of the hydraulic oil to the hydraulic motor, it is simple to control the discharge amount using a variable discharge type hydraulic pump, but when using a constant discharge type hydraulic pump. May use a flow control valve or change the number of revolutions of the engine that drives the hydraulic pump.

According to a third aspect of the present invention, there is provided an automatic guided vehicle in which each axle is mounted on a frame via an arm and the arm is rotated by an elevating cylinder to change the height of a carrier. A device is provided, and when a slip state is detected, the lifting cylinder of the corresponding wheel is operated to increase the axle load.

In this automatic guided vehicle, the loading and unloading of the cargo can be carried out without using a crane, and the carrier can be moved up and down so that the carrier itself can be loaded and unloaded. The driving and steering of the axle are the same as those in claim 1. It has. In the case of this carrier, since each axle can be raised and lowered, the slip state can be eliminated by lowering the axle determined to be in the slip state and increasing the axle load. Therefore, there is no need to change the traveling speed.

The invention according to claim 2 can be naturally applied to an automatic guided vehicle capable of moving up and down a carrier.

[0017]

Embodiments of the present invention will be specifically described below with reference to the drawings. First, an embodiment of the present invention will be described with reference to FIGS.

The automatic guided vehicle has a number of axles, each of which is independently driven by a hydraulic motor 8, and each axle can be independently steered by a steering cylinder 5. Further, unlike the transport vehicle shown in FIG. 4, the arm 3 and the lifting cylinder 4 for lifting and lowering the loading platform are not provided. In FIG. 5, the lifting device 30 is omitted.

The traveling is performed by operating the hydraulic motor 8 and the steering cylinder 5 in accordance with a command from the hydraulic control device 10 based on data of a traveling route set in advance, and the guidance is performed by detecting a derivative laid on the traveling route with a sensor. I have. This automatic guided vehicle's slip detection device and slip elimination device
As shown in the block diagram of FIG. 1, the hydraulic motor 8 includes a rotation detector 15 provided on an output shaft (coaxial with the axle) and a slip control device 20. The slip control device 20 includes an input unit 21 and a storage unit. 22, a calculation unit 23, a comparison determination unit 24, and a control command unit 25.

The input unit 21 takes in the signal from the rotation detector 15 and the signal of the steering angle of each wheel from the hydraulic control unit 10 and converts it into a signal which can be easily processed to the arithmetic unit 23 and outputs it. The computing unit 23 computes an average rotation speed R0 of each axle during straight running to determine a slip value by which a slip is determined.
m is calculated.

The comparison / decision unit 24 compares the rotation speeds R1, R2, R3,... Of the respective wheels with the judgment value Rm in the case of straight running. Is determined to be in the slip state and output to the control command unit 25. In the case of curve running, the rotation speed of each axle is compared with the allowable rotation speed according to the steering angle of each wheel prepared in advance in the storage unit 22. It is determined to be in the state, and output to the control command unit 25.

The control command section 25 issues a command to reduce the discharge amount to the discharge amount control valve 13 of the variable discharge type hydraulic pump 7 that supplies the hydraulic oil to the hydraulic motor 8, thereby reducing the traveling speed. Next, the operation of slip detection and slip elimination of the automatic guided vehicle will be described with reference to the flowchart of FIG.

The unmanned guided vehicle travels with a target vehicle speed set based on a travel plan, based on which a command is sent from the hydraulic control device 10 to the solenoid valve 13 to control the discharge amount of the hydraulic pump 7. First, at step 100, the rotation speeds R1, R2,... Of the hydraulic motors 8 of the respective axles are detected by the respective rotation detectors 15 and sent to step 110. In step 110, it is determined whether the vehicle is traveling straight or on a curve. If the vehicle is traveling straight, an average rotation speed R0 of the rotation speed of each axle is calculated (step 120), and a determination value for determining slip is determined. Rm
Is calculated (step 130). Here, the determination value Rm is set to 120% of the average rotation speed. Then, in step 140, the rotational speeds R1, R2, R3,... Of each axle are compared with the determination value Rm, and if there is a rotational speed greater than the determination value Rm, it is determined that the wheel is in a slip state (step 140). 170).

If there is no rotational speed greater than the determination value Rm, it is determined that no slip has occurred, and the routine returns to step 100. On the other hand, if it is determined in step 110 that the vehicle is traveling on a curve, the allowable rotation speed (minimum value RS, maximum value Rn) for the steering angle of each axle commanded by the hydraulic control device 10 and the steering angle stored in the storage unit 22 in step 150. ) Is obtained, and it is determined whether or not the rotation speeds R11, R12,... Of each axle are within the allowable rotation speed range (step 160). Is determined (step 170).

If the rotational speeds of all axles are within the allowable range, it is determined that no slip has occurred, and step 1 is executed.
Returned to 00. When the slip state is determined in step 170, a process for eliminating the slip is instructed from the control command unit 25 to the hydraulic control device 10 (step 180).

This elimination process is performed by controlling the discharge amount control valve 1 of the variable discharge type hydraulic pump 7 that supplies pressure oil to the hydraulic motor 8.
A command to decrease the discharge amount is issued to 3, and the traveling speed is reduced. When it is determined in step 170 that the vehicle is in the slip state, the counting is performed (step 190), and the number of occurrences within a predetermined time is compared with a set value (step 19).
5) If the number is small, the process returns to step 100, and the detection of the slip state and the processing are repeated.

If the number of times is greater than the set value, it is determined that there is an abnormality, and the traveling is stopped (step 200). next,
A third embodiment of the present invention will be described. The automatic guided vehicle is the same as that described with reference to FIGS.
That is, the axle is attached to the frame via the arm 3 which rotates in the vertical direction by the lifting cylinder 4 on the automatic guided vehicle of the above-described embodiment, so that the loading platform can be raised and lowered.

As shown in the block diagram of FIG. 3, the slip detecting device and the slip eliminating device of the automatic guided vehicle are as follows.
It comprises a rotation detector 15 provided on the output shaft of each hydraulic motor 8 and a slip control device 20, and is the same as in the above embodiment. The determination of the slip state is the same as in the above embodiment, and the description is omitted.

This embodiment is different from the above-described embodiment in a elimination process for eliminating a slip performed after the determination of the slip state. Specifically, the command issued from the control command unit 25 to the hydraulic control device 10 is different from the above. That is, the control command unit 25 causes the hydraulic control device 1 to extend the lift cylinder 4 of the wheel determined to be in the slip state.
Command to 0. The hydraulic control device 10 instructs the solenoid valve 12 of the corresponding cylinder 4 to raise the cylinder 4.

This means that in the flowchart of FIG. 2, the means of the slip elimination process in step 180 is different. In this elimination process, since the wheel on which the slip has occurred is specified in step 170, the lifting cylinder 4 of the axle is extended to increase the axle load.

[0031]

As described above, the automatic guided vehicle slip detecting device according to the first aspect of the present invention is provided with a rotation detector on each axle, and when traveling straight, average rotation calculated from the rotation speed of each axle. The rotation speed of each axle is compared with the determination value.If there is an axle with a rotation speed higher than the determination value, it is determined that the vehicle is in a slip state. The rotational speed is compared with the allowable rotational speed according to the steering angle, and when there is a rotational speed outside the allowable rotational speed, the slip state is determined, so that the slip state can be detected quickly and easily. .

According to a second aspect of the present invention, when the slip detecting device detects a slip state, the traveling speed is reduced by reducing the amount of supply of hydraulic oil to the hydraulic motor. Is easily eliminated. According to a third aspect of the present invention, there is provided an automatic guided vehicle in which each axle is attached to a frame via an arm, and the arm is rotated by an elevating cylinder to change the height of the carrier. When a slip condition is detected, the lifting cylinder of the corresponding axle is actuated to increase the axle load, so that the slip condition is easily eliminated without lowering the vehicle speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a device for detecting and eliminating slip of an automatic guided vehicle according to the first and second aspects of the present invention.

FIG. 2 is a flowchart showing a control flow for detecting and eliminating a slip according to the present invention (claims 1 to 3).

FIG. 3 is a block diagram showing a configuration of a device for detecting and eliminating slippage of an automatic guided vehicle according to a third aspect of the present invention.

FIG. 4 is a side view showing the configuration of the automatic guided vehicle.

FIG. 5 is an explanatory diagram showing a power system for traveling, steering, and lifting / lowering of a carrier of the automatic guided vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Carrier 2 ... Wheel 3 ... Arm 4 ... Lifting cylinder 5 ... Steering cylinder 6 ... Hydraulic pump 7 ... Hydraulic pump 8 ... Hydraulic motor 9 ... Engine 10 ... Hydraulic control device 11, 12 ... Solenoid valve 13 ... Discharge amount control valve 15 ... Rotation speed detector 20 ... Slip control device 21 ... Input unit 22 ... Storage unit 23 ... Calculation unit 24 ... Comparison / determination unit 25 ... Control command unit 30 ... Load carrier elevating device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 29/04 B60K 17/358 F-term (Reference) 3D001 AA01 BA01 CA08 DA17 EB08 EB24 ED03 3D043 AA01 AA05 AB08 AB16 CB01 EA07 EB03 EB06 EB11 EE07 EE18 EF02 EF06 EF09 EF15 EF24 EF25 3G093 AA01 AA08 AA15 BA01 BA26 DB00 EB00 EB06 FA11

Claims (3)

[Claims] 1. A slip detecting device for an automatic guided vehicle provided with a number of independently driven axles driven independently by a hydraulic motor, wherein each of the axles is provided with a rotation detector.
A rotational speed higher than the average rotational speed calculated from the rotational speed of each axle by a predetermined value is determined as a determination value, and the rotational speed of each axle is compared with the determination value. Then, when traveling on a curve, the rotational speed of each axle is compared with an allowable rotational speed according to the steering angle, and if there is a rotational speed outside the allowable rotational speed, it is determined that a slip state is present. Automatic guided vehicle slip detection device. 2. The method according to claim 1, wherein when the slip detecting device detects a slip condition, the running speed is reduced by reducing the amount of pressure oil supplied to a hydraulic motor for driving each axle. A feature of automatic guided vehicle slip elimination equipment. 3. An automatic guided vehicle in which each axle is mounted on a frame via an arm and the arm is rotated by an elevating cylinder to change the height of the loading platform, wherein the slip detecting device according to claim 1 is provided. A slip eliminating device for an automatic guided vehicle, characterized in that, when a state is detected, the lifting cylinder of the corresponding axle is operated to increase the axle load.