JP2005071128A - Automatic guided transport vehicle and method for controlling travel thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of controlling a simple type automatic guided transport vehicle of the two-wheel drive type with a three-wheeler configuration so that it travels smoothly along a curved path without causing an overloaded condition. <P>SOLUTION: When the vehicle turns along a curved path, the steering angle θ of its front drive wheel 1 is detected; based on the ratio of the turning radii Rf, Rr of the front drive wheel 1 and the rear drive wheel 2 with respect to a center O of turning, which radii differ with each other correspondingly to the steering angle θ detected, and on the travel speed Vf of the front drive wheel 1, a speed command value for the rear drive wheel 2 at which the front drive wheel 1 and the rear drive wheel 2 assume the same angular velocity with respect to the center O of turning is calculated. The rear drive wheel 2 is controlled based on the speed command value calculated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a tricycle configuration including a front drive wheel and a steering wheel disposed at a front side location on a center line in a traveling direction of a vehicle body, and a rear drive wheel disposed at each of left and right sides on the rear side in the traveling direction. More specifically, the present invention relates to a method for controlling the traveling of a simple type automatic guided vehicle of the two-wheel drive system, and more specifically, traveling control for smoothly turning the automated guided vehicle along a curved traveling path without being overloaded. It is about the method.

  Conventionally, for the purpose of automation and labor saving, a guided method using a fixed track with no track is generally adopted for the traveling control of the automatic guided vehicle used in the automatic guided system. . The above-mentioned fixed route is set by a guide line in which guide tape or the like is attached to the floor surface of an unmanned warehouse or factory, and the automatic guided vehicle detects the guide line by an electromagnetic or optical detection means by a line sensor. However, it is designed to automatically run along the guidance line.

  As an inexpensive and simple type of automatic guided vehicles used in the automatic guided system, one having a form as shown in FIG. 6 or FIG. 7 is generally known. The automatic guided vehicle in FIG. 6 is a one-wheel drive type in which one drive wheel 50 rotated by a drive motor 51 and two driven wheels (casters) 52 and 53 are provided in a three-wheeled vehicle arrangement, The driven wheel 52 on the left side of the figure is adapted to transmit the rotational force of the drive motor 58 by switching operation of the clutch mechanism 54 when it is desired to slide or spin. FIG. 4A shows a straight traveling state, and FIG. 4B shows a side sliding state.

In addition, the automatic guided vehicle in FIG. 7 has front drive wheels 55 and rear drives that are rotationally driven by front drive wheel drive motors 57 and rear drive wheel drive motors 58 at front and rear positions on the center line along the traveling direction of the vehicle body. This is a two-wheel drive type in which wheels 56 are arranged, and has a structure in which casters 59 and 59 for preventing tilting are arranged on both the left and right sides in the central portion in the traveling direction, and the illustration is omitted. However, the driving direction of the front driving wheel 55 and the rear driving wheel 56 is arbitrarily changed by rotating around the horizontal plane with the steering shaft as the rotation center. When the automatic guided vehicle is turned along a curved traveling path such as a corner section, traveling control is performed so that the rear driving wheel is changed to the same steering angle in reverse phase with respect to the front driving wheel. Each of the automatic guided vehicles shown in FIGS. 6 and 7 is of a simple type, and the drive motors 51, 57, and 58 are all small.
JP 11-327648 A

  However, since the automatic guided vehicle in FIG. 6 is a one-wheel drive type using only a small drive motor 51, there is a limit on the load weight of a transportable object, for example, about 100 kg. Further, since the automatic guided vehicle in FIG. 7 is a two-wheel drive type, it can transport an object to be transported with a loading weight of about 300 kg, but the front and rear drive wheels 55 and 56 are arranged on the same line. Therefore, in addition to the need for two casters 59 and 59, the number of parts is increased, and when traveling along a curve traveling path, the steering angle of the rear driving wheel 56 is set to the steering angle of the front driving wheel 55. On the other hand, in order to set the same angle in the opposite phase, it is necessary to provide a steering mechanism for each of the front and rear drive wheels 55 and 56, which increases the cost as the configuration becomes complicated.

  Therefore, it is conceivable to use an automatic guided vehicle as shown in FIG. This automatic guided vehicle is provided with two front and rear drive wheels 55 and 56 and one follower wheel (caster) 59 that are individually driven to rotate by drive motors 57 and 58 in a tricycle configuration similar to FIG. It has become a two-wheel drive type. The front drive wheel 55 is provided with a steering portion (not shown), and travel control is performed so that the front and rear drive wheels 55 and 56 always travel at the same speed. Since this automatic guided vehicle is a two-wheel drive type in the form of a three-wheeled vehicle, there is an advantage that it is possible to transport an object to be transported having a similar load weight while simplifying the configuration as compared with the automatic guided vehicle of FIG. .

  However, in this automatic guided vehicle, for example, when traveling along a curved traveling path such as a corner section, the front and rear drive wheels 55 and 56 are not arranged on the same line. Although the speed difference between the front and rear drive wheels 55 and 56 is different from each other, the front and rear drive wheels 55 and 56 are controlled to travel at the same speed. The rear drive wheel 56 is overloaded when turning, and the front drive wheel 55 is overloaded when turning clockwise in the figure. As a result, slipping occurs in at least one of the drive motors 57 and 58, making it difficult to smoothly turn, and as a result of frequent occurrence of an overload state, the life of the travel system or the drive system is shortened. Easy to invite.

  The present invention has been made in view of the above-described conventional problems, and a two-wheel drive simple automatic guided vehicle in the form of a three-wheeled vehicle can be smoothly moved along a curve traveling path without causing an overload state. The object is to provide a method that can be controlled to run.

  In order to achieve the above object, a traveling control method for an automatic guided vehicle according to a first aspect of the present invention includes a front drive wheel disposed at a front position on a center line in a traveling direction of a vehicle body, and rear left and right traveling directions. When controlling the traveling of the automatic guided vehicle that is provided at each of the both side portions, and at least one of which is a rear driving wheel, the steering unit is provided only on the front driving wheel, along the curve traveling path When turning, the front drive wheel and the rear drive wheel calculate the speed command value of the rear drive wheel with the same angular velocity with respect to the turning center, and based on the calculated speed command value, the rear drive wheel It is characterized by running control.

  The invention according to claim 2 detects the steering angle of the front driving wheel, and the ratio of the respective turning radii with respect to the turning center of the front driving wheel and the rear driving wheel, which differ according to the detected steering angle, and the Based on the traveling speed of the front driving wheel, the speed command value of the rear driving wheel is calculated.

  The invention according to claim 3 always determines whether or not the steering angle is larger than a predetermined set angle, and when the determination result is smaller than the set angle, the front drive wheel and the rear drive wheel are the same. When the determination result is larger than the set angle, the command speed of the rear drive wheel is such that the angular speed of the front drive wheel and the rear drive wheel with respect to the turning center is the same. A value is calculated, and the rear drive wheel is controlled to travel based on the calculated speed command value.

  According to a fourth aspect of the present invention, a speed command value, which is a traveling speed of the rear driving wheel having the same angular speed with respect to the turning center of the front driving wheel and the rear driving wheel, is obtained using the traveling speed of the front driving wheel as a reference speed. The correction coefficient is calculated in advance for each different steering angle, stored in a table, and after traveling along the curve traveling path, the traveling speed and the steering angle of the front drive wheel are detected. The correction coefficient corresponding to the calculated steering angle is read from the table, and the speed command value of the rear drive wheel is calculated by performing a calculation based on the traveling speed of the front drive wheel and the correction coefficient. .

  The invention according to claim 5 is characterized in that the steering angle is θ, the tread that is the distance between the rear drive wheel and the driven wheel is T, the wheel base that is the distance between the front drive wheel and the rear drive wheel is W, and the front drive wheel When the traveling speed of the vehicle is Vf, a different correction coefficient for each steering angle θ is calculated in advance from the equation Vf × [cos θ−T × sin θ / (2 W)] and stored in the table. ing.

  In the invention according to claim 6, when turning on the power to the automatic guided vehicle or when the automatic guided vehicle becomes unstable, it is determined whether or not it is detected that the steering angle has returned to the origin, Until the return to origin is detected, control is performed so that the front drive wheel and the rear drive wheel travel at a preset low speed, respectively.

  According to a seventh aspect of the present invention, the front of the turning center that changes in accordance with the amount of tire deformation, after the tire deformation amount of the rear drive wheel is obtained before changing with the load weight of the conveyed object, An apparent difference in the turning radius of the rear driving wheel is calculated, and the command speed value of the rear driving wheel calculated based on the traveling speed of the front driving wheel is corrected based on the calculated apparent difference in the turning radius. It is like that.

  In the invention according to claim 8, the load weight of the conveyed object is measured by the load measuring means, and the tire deformation amount of the front and rear drive wheels is calculated based on the measured load weight.

  In the invention according to claim 9, the load weight of the conveyed object is measured by the load cell.

  Further, the automatic guided vehicle of the invention according to claim 10 is disposed at each of the front drive wheel disposed at the front side position on the center line in the traveling direction of the vehicle body and at both the left and right side positions at the rear side in the traveling direction. A wheel having one of the rear drive wheels, a steering unit provided only on the front drive wheel, and a turning center of the front drive wheel and the rear drive wheel when turning along a curve travel path. A control device is provided for controlling the rear drive wheel that calculates a speed command value of the rear drive wheel having the same angular velocity and performs traveling control based on the calculated speed command value.

  According to an eleventh aspect of the present invention, the control device detects the steering angle of the front drive wheel, and sets each of the turning radii relative to the turning centers of the front drive wheel and the rear drive wheel that differ according to the detected steering angle. Based on the ratio and the traveling speed of the front driving wheel, a speed command value for the rear driving wheel is calculated.

  In the invention according to claim 12, the control device determines whether or not the steering angle is larger than a predetermined set angle, and when the determination result is smaller than the set angle, the front drive wheel and the rear drive wheel And the rear drive where the angular velocities with respect to the turning center of the front drive wheel and the rear drive wheel are the same when the determination result is larger than the set angle. A wheel command speed value is calculated, and the rear drive wheel is travel-controlled based on the calculated speed command value.

  According to the first aspect of the present invention, when the simple and inexpensive automatic guided vehicle of the two-wheel drive type in the form of a three-wheeled vehicle is turned along the curve travel path, the front and rear drive wheels are adapted to the difference in the steering angle. Even if the turning radius changes, the traveling speed of the rear driving wheel is variably adjusted so that the angular speeds of the front driving wheel and the rear driving wheel with respect to the turning center are the same. The occurrence of an overload condition caused by the speed difference can be effectively suppressed, and the vehicle can smoothly turn along the curve travel path. Therefore, it is not necessary to modify or add to the mechanism of a simple automatic guided vehicle of the two-wheel drive type in the three-wheeled vehicle form, and the traveling control is simply applied to the automated guided vehicle having the existing configuration. By carrying out the above, it is possible to transport an object having a relatively large load weight without any trouble.

  In the second aspect of the invention, the speed command value of the rear drive wheel is calculated based on the ratio of the turning radius of the rear drive wheel before the change in the steering angle corresponding to the difference, with the traveling speed of the front drive wheel as the reference speed. The traveling control can be performed accurately and reliably so that the angular velocities of the front drive wheel and the rear drive wheel with respect to the turning center are the same.

  In the third aspect of the invention, in general, high speed running is performed with a small steering angle, and low speed running is performed when the steering angle is large. Therefore, the speed command value of the rear drive wheel is calculated in a very short time during high speed running with a small steering angle. Accordingly, it is possible to prevent an increase in the amount of calculation in the control unit, and to prevent abnormal traveling control due to insufficient processing of the control unit.

  In the invention of claim 4, if the traveling speed and the steering angle of the front driving wheel are detected, for example, by a simple calculation of simply multiplying the traveling speed of the front driving wheel by a correction coefficient corresponding to the steering angle, The speed command value of the rear drive wheel can be calculated, and the calculation process of the speed command value of the rear drive wheel can be simplified.

  In the invention of claim 5, the correction coefficient for calculating the speed command value of the rear drive wheel with the traveling speed of the front drive wheel as the reference speed is accurately determined based on the ratio of the turning radii of the front and rear drive wheels. Can be set.

  In the invention of claim 6, in the state where the automated guided vehicle is unstable, for example, in the encoder of the steering unit in the simple automated guided vehicle, data is lost when the battery power is turned off, and the battery power is turned on again. In such a case, the vehicle becomes unstable until the steering function is restored to a normally functioning state. Therefore, it is possible to suppress the automatic guided vehicle from traveling at a high speed in a state where the steering function does not function normally, and to return to a state where the steady control process can be performed as quickly as possible while the output of the drive motor is small. Can do.

  According to the seventh aspect of the present invention, even when the load weight of the conveyed object is increased and the tire deformation amount of the front and rear drive wheels is increased, the vehicle can be smoothly turned. In the invention of claim 8, for example, data obtained by measuring the tire deformation amount of the front and rear driving wheels in advance with respect to the loaded weight is stored in a table, and the tire deformation amount is read from the table based on the measured loaded weight. It is possible to easily and accurately calculate the apparent difference between the turning radii of the front and rear drive wheels with respect to the turning center that changes according to the amount of tire deformation.

  According to the ninth aspect of the present invention, it is possible to easily and accurately measure the loaded weight of the conveyed object.

  The invention according to claim 10 is a simple and inexpensive structure of a two-wheel drive system in the form of a three-wheeled vehicle, but when turning along a curve traveling path, the front and rear drives corresponding to the difference in steering angle Even if the turning radius of the wheel changes, the traveling speed of the rear driving wheel can be variably adjusted so that the angular speeds of the front driving wheel and the rear driving wheel with respect to the turning center are the same. It is possible to smoothly turn along a curved road while effectively suppressing the occurrence of an overload caused by the speed difference. Therefore, the existing structure of the simple type of the two-wheel drive system in the form of a three-wheeled vehicle does not require any modification or attachment on the mechanism, and only a software change in the control device makes it possible to cover a relatively large load. Transported objects can be transported without hindrance.

  In the invention of claim 11, the control device uses the traveling speed of the front driving wheel as a reference speed, and changes the steering angle according to the difference between the steering angle and the speed command value of the rear driving wheel based on the ratio of the turning radius of the rear driving wheel. Therefore, traveling control can be performed accurately and reliably so that the angular velocities of the front driving wheel and the rear driving wheel with respect to the turning center are the same.

  In the twelfth aspect of the invention, high speed running is generally performed with a small steering angle and low speed running is performed when the steering angle is large. Therefore, the speed command value of the rear drive wheel is calculated in a very short time during high speed running with a small steering angle. Accordingly, it is possible to prevent an increase in the amount of calculation in the control device, and to prevent abnormal traveling control due to insufficient processing of the control unit.

  Hereinafter, the traveling control method of the automatic guided vehicle according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of an automatic guided vehicle that is a control target of a traveling control method according to the present invention. This automatic guided vehicle has a front drive wheel 1 disposed at a front side position on a center line in a traveling direction indicated by an arrow, and a rear drive wheel 2 and a driven wheel 3 disposed at left and right rear positions in the traveling direction. It is a two-wheel drive type in the form of a tricycle arranged on the lower surface side. The front and rear drive wheels 1 and 2 are individually driven to rotate by a front drive wheel drive motor 7 and a rear drive wheel drive motor 8, respectively. The front drive wheel drive motor 7 is housed in a steering section 9 that also serves as a motor case.

  The steering unit 9 is attached to the vehicle body 4 so as to be rotatable around a horizontal plane with the steering wheel 10 as a rotation center, and the rotation of the steering wheel drive motor 11 is transmitted to the steering wheel 10 via the belt 12. It is rotated by. At this time, the front drive wheel 1 is rotated integrally with the steering unit 9 to change the direction. A line sensor 13 for detecting a guide line 14 laid on the floor surface is attached to the front surface of the steering unit 9. Therefore, this automatic guided vehicle is structurally the same as that shown in FIG.

  FIG. 2 is a functional block showing an electric system configuration of the automatic guided vehicle. In this figure, the same or corresponding parts as in FIG. A control unit 18 including a CPU in the control device 17 controls the entire automatic guided vehicle by executing a control program set and stored in the ROM 20 based on the control data stored in the RAM 19. Further, the control unit 18 appropriately reads the correction coefficient set and stored in advance in the table 21, calculates the speed command value of the rear drive wheel 2, and based on the calculated speed command value, the travel speed of the rear drive wheel 2 is calculated. The control is performed, and details thereof will be described later.

  The front drive wheel drive motor 7 is rotationally controlled by a motor driver unit 22 that receives a speed command signal from the control unit 18, and the rear drive wheel drive motor 8 is a motor driver unit that receives a speed command signal from the control unit 18. The steering wheel drive motor 11 is controlled to rotate by a predetermined angle in the forward and reverse directions by the motor driver unit 24 that receives the steering angle command signal from the control unit 18. When these drive motors 7, 8, and 11 are rotationally driven, encoder pulses output from the encoders 7a, 8a, and 11a provided therein are respectively input to the corresponding motor driver units 22, 23, and 24. These motor driver units 22, 23, and 24 count the input encoder pulses with their built-in counters and perform predetermined calculations to thereby obtain positional information on the front, rear drive wheels 1 and 2, and the steered wheels 10, respectively. The signal is calculated and output to the control unit 18. Further, the detection signal of the guide line 14 is input from the line sensor 13 to the control unit 18.

  When the automatic guided vehicle travels straight forward, the control unit 18 executes a control program and outputs a speed command signal based on the command speed set and stored in the control data to the motor driver units 22 and 23. The rear drive wheel drive motors 7 and 8 are controlled to rotate at the same speed. Further, the control unit 18 outputs a steering angle command signal to the motor driver unit 24 based on the detection signal input from the line sensor 13. Further, the control unit 18 calculates a steering angle for correcting the traveling direction of the vehicle body 4 so as to match the guide line 14, and sends a steering angle command signal based on the calculated steering angle to the motor driver unit 24. The steering wheel 10 is output and controlled via the steering wheel drive motor 11. Thereby, the automatic guided vehicle travels automatically along the guide line.

  Next, traveling control by the control unit 18 when the automatic guided vehicle travels along a curved traveling path such as a corner section will be described. FIG. 3 is a diagram for explaining travel control when the automatic guided vehicle travels along a curved travel path. This figure exemplifies a case where the vehicle body turns counterclockwise along a curve traveling path. In the figure, the steering angle formed by the center line S of the traveling direction of the vehicle body 4 and the front drive wheel 1 is represented by θ. The tread that is the distance between the rear drive wheel 2 and the driven wheel 3 is T, the wheel base that is the distance between the front drive wheel 1 and the rear drive wheel 2 is W, the traveling speed of the front drive wheel 1 is Vf, and the rear drive wheel 2 is Vr, the traveling speed of the central portion of the vehicle body 4 facing the rear driving wheel 2 is Vc, the turning radius of the front driving wheel 1 is Rf, the turning radius of the rear driving wheel 2 is Rr, and the rear driving of the vehicle body 4 is performed. Let Rc be the turning radius of the central part facing the wheel 2. The steering angle θ is positive in the counterclockwise direction and negative in the clockwise direction with respect to the center line S of the vehicle body 4.

In the traveling control method according to this embodiment, the turning radii Rf and Rr of the front and rear drive wheels 1 and 2 are different when turning along a curve traveling path, whereas the angular velocities are equal to each other. Travel control is performed so that the travel speed of the rear drive wheel 2 is corrected with reference to the travel speed of the front drive wheel 1. Therefore, in order for the angular velocities with respect to the turning center O in the front and rear drive wheels 1 and 2 to be equal,
It suffices if the equation dθ / dt = Vf / Rf = Vc / Rc = Vr / Rr holds. Further, the above equation can be transformed to Vc = Vf × (Rc / Rf) = Vfd × cos θ. Furthermore, the above equation can be modified as follows.

Vr = Vc × (Rr / Rc) = (Vf × cos θ) × (Rc−T / 2) / Rc = Vf × cos θ × (1−T / 2Rc)
On the other hand, since tan θ = W / Rc and Rc = W / tan θ, the following equation is established.

Vr = Vf × cos θ × [1-T × tan θ / (2 W)] = Vf [cos θ−T × sin θ / (2 W)]
That is, since the equation of Vr = Vf [cos θ−T × sin θ / (2W)] is established, the angular velocities of the front and rear driving wheels 2 with respect to the turning center O when turning along the curve traveling path are made the same. Therefore, the travel speed Vr of the rear drive wheel 2, that is, the speed command value of the rear drive wheel 2, is a speed ratio of the rear drive wheel 2 to the front drive wheel 1 to the travel speed Vf of the front drive wheel 1 serving as a reference speed. It can be calculated by multiplying [cos θ−T × sin θ / (2W)]. Here, since the tread T and the wheel base W are unique to the automatic guided vehicle, [cos θ−T × sin θ / (2 W)] is replaced with the correction coefficient k, and the correction coefficient k for each of various steering angles θ. Can be calculated in advance. Therefore, in this embodiment, the value of the correction coefficient k for each of various steering angles θ is calculated in advance, and the calculated value of the correction coefficient k is set and stored in the table 21 in FIG. 2 in association with the steering angle θ. ing.

  Next, the travel control process by the control unit 18 of the above embodiment will be described with reference to the flowcharts of FIGS. FIG. 4 is a flowchart showing the travel control process by the control unit 18. In the figure, the control unit 18 always performs a calculation to calculate the steering angle θ based on the position information signal input from the motor driver unit 24 in FIG. 2 (step S1), and the calculated steering angle θ is a predetermined set angle. For example, it is determined whether the angle is greater than 5 ° (step S2).

  In general, when traveling at a high speed, the vehicle travels with a small steering angle θ, and when traveling along a curved road, traveling at high speeds can cause adverse effects on the transported object and difficult to control due to the effects of centrifugal force. From low speed. Therefore, when the steering angle θ is small compared to the predetermined set angle, the vehicle travels straight at a relatively high speed, and when the steering angle is large compared to the predetermined set speed, the vehicle travels at a low speed. Turn around along. Therefore, the predetermined set angle is a steering angle θ that can distinguish between high-speed running and low-speed running, and the set angle is compared with the steering angle θ to determine whether it is high-speed running or low-speed running. Can be distinguished.

  Now, assuming that the automatic guided vehicle starts turning along a curved traveling path, the control unit 18 determines that the steering angle θ is larger than a predetermined set angle, and therefore performs control as low speed traveling. Subsequently, the traveling speed Vf of the front drive wheel 1 is calculated based on the position information signal input from the motor driver unit 22 (step S3), and the correction coefficient k corresponding to the calculated steering angle θ is read from the table 21 ( Step S4), the rear drive wheel 2 that can make the angular velocities of the front drive wheel 1 and the rear drive wheel 2 with respect to the turning center O the same by performing an operation of multiplying the traveling speed Vf of the front drive wheel 1 by the correction coefficient k. A speed command value that is the travel speed Vr of the current is calculated (step S5).

  After that, the control unit 18 outputs a speed command signal based on the calculated speed command value of the rear drive wheel 2 to the motor driver unit 23 to thereby control the rotation of the rear drive wheel drive motor 8 and thereby control the rear drive wheel 2. Is driven at the speed command value calculated above. Thereby, although the turning radii Rf and Rr of the front drive wheel 1 and the rear drive wheel 2 with respect to the turning center O are different from each other, the turning centers O of the front driving wheel 1 and the rear driving wheel 2 are different. Thus, the vehicle can smoothly turn and the driving system for traveling and steering is effectively prevented from being overloaded.

  In addition, this traveling control method has an inexpensive configuration similar to that shown in FIG. 8 and an automated guided vehicle capable of transporting an object to be transported having a load weight of about 2.5 times that of the automated guided vehicle of FIG. On the other hand, the effect can be obtained by running control only by software change without any modification or attachment of the structure on the mechanism.

  Then, the control unit 18 returns to step S1 and executes the same control process as described above until it is determined that the conveyance is finished (step S7), and if the steering angle θ is smaller than the set angle during high speed traveling. When the determination is made (step S2), the traveling speed Vf of the front drive wheel 1 is calculated based on the position information signal input from the motor driver unit 22 (step S8), and then the speed command signal based on the calculated traveling speed Vf. Is output to the motor driver unit 23 (step S9), and the traveling speed of the rear driving wheel 2 is controlled to be the same as the traveling speed of the front driving wheel 1 (step S6). As described above, when the steering angle θ is smaller than the set angle, the calculation of the speed command value for the rear drive wheel 2 is not performed. It is possible to eliminate an increase in the amount of calculation in the control unit 8 when calculating the value in an extremely short time, and to prevent abnormal traveling control due to insufficient processing of the control unit 18.

  FIG. 5 is a flowchart illustrating a control process executed by the control unit 18 every time a travel speed is newly set during travel control. In the figure, the control unit 18 performs the speed setting process and the steering origin detection process in parallel. First, the speed setting process will be described. The control unit 18 determines whether or not the currently set speed is not equal to the command speed (step S11), and monitors whether the current set speed is not equal when it is equal. Then, the control unit 18 determines whether or not the steering origin detection flag is ON at the time when it is determined that the currently set speed is not equal to the command speed (step S11) (step S12). When it is determined that the steering origin detection flag is on (step S12), or after it is determined that the steering origin detection flag is off (step S12), the command speed is the same as or less than the specified low speed. Is determined (step S13), the command speed is set to the currently set speed (step S15), and the front and rear drive wheels 1 and 2 are controlled to travel at the command speed via the motor driver units 22 and 23. After that, the process returns to step S11 and the same control process as described above is repeated.

  When it is determined that the command speed is greater than the designated low speed (step S13), the designated low speed is set to the currently set speed (step S14) and the front and rear driving wheels are set via the motor driver units 22 and 23. After controlling to run 1 and 2 at the designated low speed, the process returns to step S11 and the same control process as described above is repeated.

  On the other hand, in the steering origin detection process, the steering origin detection flag is turned off (step S17) when the power is turned on (step S16). Thereafter, the control unit 18 determines whether or not the origin of the steering angle θ has been detected (step S18), waits for the origin of the steering angle θ to be detected, and determines that the origin of the steering angle θ has been detected. At the time of (step S18), the steering origin detection flag is set to ON (step S19), and the steering origin detection process is terminated.

  The control process described above is performed when the steering angle origin detection flag is turned off during the speed control process and the control becomes unstable. For example, in the simple type automatic guided vehicle to be controlled according to the present invention, the data of the encoder 11a of the steering wheel drive motor 11 is lost when the battery power is turned off, and the origin is detected when the battery power is turned on next time. The flag is turned off. In that case, the control process described with reference to FIG. 5 is performed to suppress the automatic guided vehicle from traveling at a high speed in a state where the steering angle θ cannot be accurately acquired, and possible while traveling at a specified low speed. It is possible to quickly return to a state where steady control processing can be performed.

  Note that the speed command value of the rear drive wheel 2 calculated based on the traveling speed Vf of the front drive wheel 1 and the correction coefficient k described above is the value of the front drive wheel 1 or 2 before and after the load weight of the conveyed object. If the tire deformation amount is measured by a load sensor or the like and corrected based on the apparent difference between the turning radii Rf and Rr with respect to the turning center O that changes in accordance with the tire deformation amount, smoother cornering is possible. Can be performed. Here, when the load weight is measured by the load measuring means and the tire deformation amount of the front and rear drive wheels is calculated based on the measured load weight, for example, the front and rear drive wheels with respect to the load weight are used. If the tire deformation amount is stored in a table in advance and the tire deformation amount is read from the table based on the measured load weight, the front and rear of the turning center that changes according to the tire deformation amount can be obtained. The apparent difference in the turning radius of the drive wheel can be calculated easily and accurately. Furthermore, if the load weight of the conveyed object is measured by the load cell, the loaded weight of the conveyed object can be easily and accurately measured.

  On the other hand, when correction according to the amount of tire deformation of the front and rear drive wheels 1 and 2 is not performed, auxiliary wheels are provided at both the left and right sides in the center of the traveling direction of the vehicle body 4, and the front and rear drive wheels described above are provided. It is preferable to take measures to prevent deformation due to the loaded weight of one or two objects to be conveyed.

  In the above embodiment, the left and right wheels on the rear side have been described by exemplifying the case where the left side is the drive wheel 2 and the right side is the driven wheel 3 and the vehicle is turning left. The scope of the right of the invention is not limited to this. For example, in the same configuration as that of the embodiment, when turning to the right, the steering angle θ in FIG. 3 may be calculated as a negative value.

  In the configuration of the rear wheel, the right side may be a driving wheel and the left side may be a driven wheel. In that case, when performing a left turn and a right turn, the traveling speed of the rear drive wheel 2 is calculated by a method that is completely opposite to that in the above-described embodiment. Further, both the left and right wheels on the rear side may be drive wheels.

  According to the automatic guided vehicle and the traveling control method of the automatic guided vehicle according to the present invention, when a simple and inexpensive automatic guided vehicle of a two-wheel drive system in the form of a tricycle is turned along a curved traveling path, Since the traveling speed of the rear driving wheel is variably adjusted so that the angular speeds of the front driving wheel and the rear driving wheel are the same with respect to the turning center, the two-wheel drive simple type automated guided vehicle is used. Carries a relatively large load to be transported without any trouble by simply performing software control on an automated guided vehicle with an existing configuration without any modification or attachment on the mechanism. It can be suitably applied when desired.

The top view which shows schematic structure of the automatic guided vehicle used as the control object of the traveling control method which concerns on this invention. The functional block which shows the electric system structure of an automatic guided vehicle same as the above. The figure for demonstrating the control in case an automatic guided vehicle same as the above turns to the left along a curve driving path. The flowchart which shows the traveling control process by the control part of an automatic guided vehicle same as the above. The flowchart which shows a control process when setting a travel speed newly in the automatic guided vehicle same as the above. The top view which shows schematic structure of the conventional automatic guided vehicle. The top view which shows schematic structure of the other conventional automatic guided vehicle. The top view which shows schematic structure of the other further conventional automatic guided vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front drive wheel 2 Rear drive wheel 3 Driven wheel 4 Car body 9 Steering part 18 Control part 21 Table S Center line (theta) Steering angle O Turning center Rf Turning radius of front driving wheel Rr Turning radius of rear driving wheel Vf Running of front driving wheel Speed Vr Travel speed of rear drive wheel T Tread W Wheel base

Claims (12)

A front drive wheel disposed at a front position on a center line in a traveling direction of the vehicle body, and a wheel disposed at each of both left and right rear positions in the traveling direction, at least one of which is a rear drive wheel. A method for controlling the travel of an automated guided vehicle in which a steering unit is provided only on a drive wheel,
Calculating a speed command value of the rear drive wheel that makes the angular velocities of the front drive wheel and the rear drive wheel the same with respect to the turn center when making a turn along a curve travel path;
A traveling control method for an automatic guided vehicle, wherein traveling control of the rear drive wheel is performed based on the calculated speed command value.   The steering angle of the front driving wheel is detected, and the ratio of the respective turning radii to the turning center of the front driving wheel and the rear driving wheel which differ according to the detected steering angle and the traveling speed of the front driving wheel are determined. 2. The traveling control method for an automatic guided vehicle according to claim 1, wherein a speed command value for the rear driving wheel is calculated based on the driving speed. It is determined whether or not the steering angle is larger than a predetermined setting angle, and when the determination result is smaller than the set angle, control is performed so that the front driving wheel and the rear driving wheel are driven at the same traveling speed. And
When the determination result is larger than the set angle, calculate a command speed value of the rear drive wheel, the angular speed of the front drive wheel and the rear drive wheel with respect to the turning center being the same,
The traveling control method for an automatic guided vehicle according to claim 1 or 2, wherein traveling control of the rear drive wheel is performed based on the calculated speed command value. A different correction coefficient is used to obtain a speed command value, which is a traveling speed of the rear driving wheel having the same angular velocity with respect to the turning center of the front driving wheel and the rear driving wheel, using the traveling speed of the front driving wheel as a reference speed. Calculate in advance for each corner and store it in the table.
When the vehicle travels along a curved road, after detecting the traveling speed and steering angle of the front drive wheel, the correction coefficient corresponding to the calculated steering angle is read from the table,
The traveling control method for an automatic guided vehicle according to any one of claims 1 to 3, wherein a calculation based on a traveling speed of the front driving wheel and a correction coefficient is performed to calculate a speed command value for the rear driving wheel. When the steering angle is θ, the tread that is the distance between the rear drive wheel and the driven wheel is T, the wheel base that is the distance between the front drive wheel and the rear drive wheel is W, and the traveling speed of the front drive wheel is Vf The correction coefficient for each different steering angle θ is
5. The traveling control method for an automatic guided vehicle according to claim 4, wherein the traveling control method is calculated in advance from an equation of Vf × [cos θ−T × sin θ / (2W)] and set and stored in a table.   When turning on the power to the automated guided vehicle or when the automated guided vehicle becomes unstable, it is determined whether the steering angle has been restored to the origin. The traveling control method for an automatic guided vehicle according to any one of claims 1 to 5, wherein the driving wheels and the rear driving wheels are each controlled to travel at a preset low speed.   After determining the tire deformation amount of the front and rear drive wheels before changing with the load weight of the conveyed object, the apparent turning radius of the front and rear drive wheels with respect to the turning center that changes according to the tire deformation amount 7. The difference in the above is calculated, and the command speed value of the rear drive wheel calculated based on the traveling speed of the front drive wheel is corrected based on the apparent difference in the calculated turning radius. The driving control method for an automatic guided vehicle according to any one of the above.   8. A traveling control method for an automatic guided vehicle according to claim 7, wherein a load weight of the object to be conveyed is measured by a load measuring means, and a tire deformation amount of the front and rear drive wheels is calculated based on the measured load weight. .   The traveling control method for an automatic guided vehicle according to claim 8, wherein the load weight of the object to be conveyed is measured by a load cell. A front drive wheel disposed at a front location on the center line in the traveling direction of the vehicle body;
A wheel disposed at each of the left and right sides on the rear side in the running direction, and at least one of the wheels as a rear drive wheel;
A steering section provided only on the front drive wheel;
When the vehicle travels along a curved traveling path, the speed command value of the rear drive wheel is calculated so that the angular speeds of the front drive wheel and the rear drive wheel are the same with respect to the turning center, and the calculated speed command is calculated. An automatic guided vehicle comprising: a control device that controls the rear driving wheel that controls traveling based on a value.   The control device detects the steering angle of the front driving wheel, and the ratio of the respective turning radii with respect to the turning center of the front driving wheel and the rear driving wheel which differ according to the detected steering angle and the traveling of the front driving wheel The automatic guided vehicle according to claim 10, wherein the automatic guided vehicle is configured to calculate a speed command value of the rear drive wheel based on the speed.   The control device determines whether or not the steering angle is larger than a predetermined set angle, and when the determination result is smaller than the set angle, the front drive wheel and the rear drive wheel travel at the same travel speed. When the determination result is larger than the set angle, the command speed value of the rear drive wheel is calculated so that the angular speeds of the front drive wheel and the rear drive wheel with respect to the turning center are the same. The automatic guided vehicle according to claim 10 or 11, wherein traveling control of the rear drive wheel is performed based on the calculated speed command value.

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