Automated guided vehicle control device

Abstract

To provide a control device for automatic guided vehicle capable of performing thrust control without a force sensor.SOLUTION: The control device has: a base 20 mounted on a movable automatic guided vehicle 10; first to fourth actuators 31 to 34 respectively installed at four corners of the base 20; and a top plate 40 which is disposed facing the tip of each output shaft of the actuators 31 to 34 and on which a load 50 (truck) is mounted. A controller 60 gives an actuator drive motor 100 a torque reference value obtained by adding a maximum static friction torque to an additional torque converted from a thrust command by a thrust command-to-addition torque conversion function.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a lift-up type automated guided vehicle (hereinafter sometimes referred to as AGV) that transports a cart by lifting it from below, and in particular to a lifter control device that enables ground transport in which the wheels of the cart are kept on the ground. [Background technology]

[0002] Conventional techniques for AGV ground transportation include the following: In Patent Document 1 and Patent Document 2, ground transportation is achieved by pressure control using a pneumatic actuator. In Patent Document 3, ground transportation is achieved by controlling the height of an electric actuator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6641994 (Patent application 2015-255945) [Patent Document 2] Patent No. 6848651 (Patent application 2017-87864) [Patent Document 3] JP 2020-77295 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Documents 1 and 2, pneumatic actuators are used, which have problems such as frequent maintenance, difficulty in high-precision control, and noise.In Patent Document 3, electric actuators are used to control the height, but the wheels of the cart may lift off the ground on uneven, undulating ground or on a slope.

[0005] In this invention, we consider an approach using force control of an electric actuator to deal with swells and inclinations. While the use of a force sensor is the first method of force control, a sensorless method is preferable in terms of cost. When trying to achieve highly accurate force control without a sensor, friction of the actuator becomes an issue. It is difficult to distinguish between reaction force and friction using only the estimated value of the reaction force by an observer.

[0006] The present invention is made to solve the above-mentioned problems, and an object of the present invention is to provide a control device for an automatic guided vehicle that can perform thrust control without a force sensor. [Means for solving the problem]

[0007] The control device for an automated guided vehicle according to claim 1 for solving the above problem comprises: A base mounted on a movable traveling body; The actuator is installed at each of the four corners of the base, and the output shaft is The above on the base Installation was done First to fourth actuators configured to be movable in a direction perpendicular to the surface; a controlled body disposed opposite to a tip end of each of the output shafts of the first to fourth actuators; a controller that controls motors for driving the first to fourth actuators; The controller has a thrust-to-additional torque conversion unit that converts a thrust command into an additional torque using a conversion function of thrust command to additional torque, and an adder unit that adds a maximum static friction torque to the converted additional torque to output a motor torque reference value, and is characterized in that an output of the adder unit is used as a motor torque reference value for the motor for driving the actuator.

[0008] The control device for an automated guided vehicle according to claim 2 is the control device for an automated guided vehicle according to claim 1, The controller is characterized by performing lifter ascent control based on a motor torque reference value using a maximum static friction torque in the positive direction, thrust control based on a motor torque reference value obtained by adding the additional torque and the maximum static friction torque, and lifter descent control based on a motor torque reference value using a maximum static friction torque in the negative direction.

[0009] The control device for an automated guided vehicle according to claim 3 is the control device for an automated guided vehicle according to claim 1 or 2, The conversion function of the thrust command to the additional torque in the thrust-additional torque conversion unit is expressed as follows: a first identification process in which the motor torque reference value is gradually increased from zero, the motor torque reference value when the actuator starts to move is recorded as a maximum static friction torque, and a value measured by a force sensor of a reaction force when the actuator is pressed against a wall surface with this torque is also recorded; a second identification process is executed to determine a relationship between the maximum static friction torque recorded in the first identification process plus an additional torque as a motor torque reference value, the reaction force measured by a force sensor when the actuator is pressed against a wall surface, and the additional torque; The relationship between the reaction force measurement value and the additional torque obtained in the second identification process is converted into a conversion function of the thrust command versus additional torque and set.

[0010] The control device for an automated guided vehicle according to claim 4 is any one of claims 1 to 3, The controller: a position controller that controls the position response value of each actuator output shaft obtained by variable-converting the angle of the actuator drive motor when the first to fourth actuators are each controlled to rise at a constant speed so that the position response value becomes a command value for the actuator length, and outputs a force reference value for the actuator; a disturbance observer that receives as input a force reference value of the actuator and a position response value of an output shaft of the actuator, and outputs an estimated disturbance proportional to a load of the actuator; a load estimator that executes a preliminary process for setting in advance a relational expression between a sum of outputs of a disturbance observer for an output shaft of each actuator when a controlled object is controlled to ascend at a constant speed by the first to fourth actuators and a sum of loads acting on the output shaft of each actuator, and then estimates a load by substituting the sum of outputs of the disturbance observer for an output shaft of each actuator when a controlled object, the load of which is unknown, is controlled to ascend at a constant speed by the first to fourth actuators into the relational expression; The thrust command is determined based on the load estimated by the load estimation device.

[0011] The control device for an automated guided vehicle according to claim 5 is the control device for an automated guided vehicle according to claim 4, The output of the disturbance observer is defined by equation (5):

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[0012] (1) According to the invention described in claims 1 to 5, force sensorless thrust control, lifter ascent and contact with the controlled object, and lifter descent can each be achieved simply by changing the thrust command value. If the controlled object is a wheeled cart, thrust control makes it possible to transport the cart with its wheels on the ground. Because thrust control is performed on each axis of the first to fourth actuators, travel according to the road surface is possible even if there is a slope or undulation. (2) According to the invention described in claim 3, the relationship between the thrust force at rest and the motor torque reference value can be identified. By using this, force sensorless thrust force control can be realized with high accuracy. Since it becomes possible to identify the actual efficiency and the thrust force at the maximum static friction torque, more accurate force control becomes possible. (3) According to the invention as recited in claim 4, it becomes possible to estimate the load without a force sensor, which can be applied to the generation of a thrust command in thrust control. (4) According to the invention described in claim 5, the conversion gain of thrust can be identified from the torque reference value of the motor without a force sensor. Since it becomes possible to identify the conversion gain (= actual efficiency), more accurate force control can be realized. [Brief description of the drawings]

[0013] [Figure 1] 3A and 3B show an overview of the device according to the present embodiment, where FIG. 3A is an external view and FIG. 3B is an explanatory diagram of the numbers of actuators as viewed from above the device. [Diagram 2] FIG. 2 is an explanatory diagram showing an example of connection between an actuator output shaft and a controlled object in the device according to the present embodiment. [Diagram 3] FIG. 1 is an overall configuration diagram of a first embodiment of the present invention. [Figure 4] FIG. 2 is a configuration diagram of a controller according to the first embodiment of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram of a conversion function of a thrust-additional torque conversion unit in the first embodiment of the present invention. [Figure 6] FIG. 11 is an overall configuration diagram of a second embodiment of the present invention. [Figure 7] FIG. 11 is an explanatory diagram of conversion variables of a thrust-additional torque conversion unit in the second embodiment of the present invention. [Figure 8] FIG. 10 is an explanatory diagram showing the relationship between the reaction force measurement value of the actuator and the additional torque, which is an experimental result in the second embodiment of the present invention. [Figure 9] FIG. 11 is an explanatory diagram showing the lifter average position and the sum of the force sensor outputs in the experimental results of thrust control in the second embodiment of the present invention. [Figure 10] FIG. 11 is an overall configuration diagram of a third embodiment of the present invention. [Figure 11]FIG. 11 is a configuration diagram of a controller according to a third embodiment of the present invention. [Figure 12] FIG. 11 is an explanatory diagram showing a relationship between the sum of disturbance observer outputs and the sum of loads in the third embodiment of the present invention. [Figure 13] 4A and 4B show the response when entering a slope, where FIG. 4A is an explanatory diagram of ground contact transportation based on height control, and FIG. 4B is an explanatory diagram of ground contact transportation based on force control of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. In embodiment 1 of the present invention, an example of feedforward type force control that is force sensorless and takes into account only static friction is described. In embodiment 2, pre-identification is performed using a force sensor to achieve more accurate sensorless force control. In embodiment 3, a load estimation method using a disturbance observer is described in relation to the generation of command values ​​for force control. EXAMPLES

[0015] An outline of a lifter device (hereinafter sometimes referred to as a four-axis lifter) according to an embodiment of the present invention is shown in Fig. 1. In Fig. 1(a), a base 20 is mounted and fixed on an automated guided vehicle (AGV: mobile vehicle) 10, and stators of first to fourth actuators 31 to 34 equipped with servo motors are fixed to the four corners of the base 20.

[0016] The output shafts of the first to fourth actuators 31 to 34 are each oriented in the vertical direction. (As shown in FIG. 1, the direction is perpendicular to the surface on which the first to fourth actuators 31 to 34 are placed on the base 20) This vertical movement is achieved by the action of a servo motor which moves the output shaft (shown as a) of the actuator in the vertical direction.

[0017] A top plate 40 constituting a controlled object is disposed at the tip of each output shaft of the first to fourth actuators 31 to 34 so as to be supported by the tip. The controlled object of the present invention is not limited to the top plate 40, but also includes luggage, a cart, a wheeled cart, and the like that are placed on the top plate 40.

[0018] 1(b) shows the positional relationship of each actuator on the top board 40. In the figure, Actuators 1 to 4 indicate the positions of the first to fourth actuators 31 to 34, and the x-axis is the traveling direction of the AGV.

[0019] In addition, the actuators 31 to 34 in this embodiment employ a ball screw mechanism as an example.

[0020] 2 shows an example of connection between the output shaft 31a of the first actuator 31 and the top plate 40 among the actuators 31 to 34. In Fig. 2, a spherical seat nut 51-1 is attached to the tip of the output shaft 31a.

[0021] A spherical seat receiver 52-1 is disposed between the spherical seat nut 51-1 and the top plate 40.

[0022] One end of a full thread (screw) 53-1 is inserted into a portion of the top plate 40 opposite the arrangement positions of the spherical seat nut 51-1, the spherical seat holder 52-1, and the spherical seat holder 52-1, connecting the spherical seat nut 51-1, the spherical seat holder 52-1, and the top plate 40.

[0023] A spherical joint may be used in place of the spherical seat nut 51-1 and the spherical seat receiver 52-1.

[0024] 2, even if the top plate 40 is tilted, the output shaft of the actuator can come into contact with the top plate 40, and the tilt of the top plate can be mechanically tolerated.

[0025] In addition, the full thread 53-1 prevents the top plate 40 from collapsing, and the other end of the full thread 53-1 is covered with a cap nut 54-1 (a top plate removal prevention device), which prevents the top plate 40 from coming off the full thread 53-1.

[0026] The second to fourth actuators 32 to 34 have the same connection configuration as that shown in FIG.

[0027] The overall configuration of the system of the first embodiment is shown in Fig. 3. In Fig. 3, the same parts as in Fig. 1 are denoted by the same reference numerals. The thick lines in Fig. 3 indicate mechanical connections. From the bottom, the AGV 10, the base 20, the motor 100 for driving the actuators, the actuators 31 to 34, the top plate 40, and the cargo 50 are connected.

[0028] The luggage 50 is to be placed on the top plate 40, and in this embodiment, it is assumed to be a wheeled cart. The motor 100 is a combination of a motor driver and the motor itself, and the actuators (31 to 34) are transmission mechanisms such as ball screws and gears.

[0029] The controller 60 provides a torque reference to the motor 100. In the first embodiment, the controller 60 does not require a feedback signal.

[0030] The configuration of the controller 60 (first embodiment) is shown in FIG. cmd The thrust-additional torque conversion unit 61 converts the thrust command to the additional torque into the additional torque τ ad The maximum static friction torque τ sf Add this to the motor torque reference value τ ref This is implemented for each actuator.

[0031] Thrust command f cmd is a constant value calculated in advance (for example, a constant multiple of the load). Maximum static friction torque τ sf The maximum static friction torque τ sf The value of is set as the torque reference value when the actuator (31 to 34) moves while gradually increasing the torque reference value.

[0032] It is assumed that the contents of the thrust-additional torque conversion unit 61 are expressed as a function of the added torque relative to the thrust command, as shown in Fig. 5. This time, it is assumed to be linear. In the case of the first embodiment where no prior identification is performed, the slope of the straight line in Fig. 5 is calculated from the catalog value of the ball screw lead or gear ratio. For example, in the case of a ball screw, the slope is found as "slope = lead / (2π x efficiency)".

[0033] In the first embodiment, the thrust force at the maximum static friction torque is assumed to be zero, but in reality it is not zero. A more accurate method of identifying the function that takes this into consideration will be described in the second embodiment.

[0034] Motor torque reference value τ in Fig. 4 ref is input to the motor driver in the block of the motor 100 in FIG. ref The current is controlled based on the

[0035] When the cargo 50 is a wheeled cart, ground transportation follows the sequence of "lifter lift → constant thrust applied for ground transportation → lifter lowering", and the details of each step are assumed to be as follows.

[0036] (1) Lifter lifting: In the lift-up operation, which does not require a pressing force, the maximum static friction torque (plus a small torque) is used as the torque reference value, and the lifter is slowly raised to contact the cart.

[0037] (2) Thrust control: After a certain time has elapsed after contact, the additional torque τ corresponding to the thrust command is applied as shown in Figure 4. ad + Maximum static friction torque τ sf The output of the adder 62, which is the torque reference value τ ref After changing the torque reference value, the wheels of the AGV 10 are driven to carry out the transportation. This completes the ground transportation.

[0038] (3) Lifter descent: After the ground transfer is completed and the AGV 10 stops, the lifter begins to descend. The maximum static friction torque in the negative direction (plus a small torque) is input as the torque reference value, and the lifter is slowly lowered. In this mechanical system, the end of the range of motion is the origin, so the system returns to the origin.

[0039] As shown in Fig. 4, the maximum static friction torque τ sf and additional torque τ ad By configuring them separately, it is possible to realize thrust control that corresponds to the individual differences in friction of each actuator (31 to 34). The control system used here is a feedforward type thrust control system.

[0040] The response when entering a slope (undulation) during ground transportation using the thrust control described above in (2) is shown in Fig. 13. Fig. 13 shows the state in which a cart 55 with wheels 55a, 55b mounted on the top plate 40 of the AGV 10 in Fig. 1(a) is being transported on the ground, and (a) shows ground transportation based on height (position) control. When one wheel 55a enters the inclined surface 91, the other wheel 55b lifts off the horizontal road surface 92, preventing normal ground transportation.

[0041] In contrast, FIG. 13(b) shows ground-contact transportation using force control in the first embodiment, so when the cart 55 enters the inclined surface 91 and tilts, the lifter naturally tilts accordingly, so that the wheels 55b do not lift up and normal ground-contact transportation can be performed.

[0042] In this manner, according to this embodiment, even if the road surface is inclined or undulating, the vehicle can travel in accordance with the road surface.

[0043] Another advantage of pre-identifying the maximum static friction torque is that the lifter can be raised and lowered by using the maximum static friction torque (plus a small torque) as the torque reference value.

[0044] Since the thrust and lifter ascent and descent are all performed by torque control, they can be achieved simply by changing the thrust command value, making implementation easy. EXAMPLES

[0045] In the first embodiment, the "thrust-torque conversion" is given without a force sensor by using catalog values ​​or the like, but in the second embodiment, a method of identifying the "thrust-torque conversion" using a force sensor will be described.

[0046] The overall configuration of the system according to the second embodiment is shown in Fig. 6. In Fig. 6, the same parts as those in Figs. 1 and 3 are denoted by the same reference numerals. In the second embodiment, the controller 70 provides a torque reference value to the motor 100, and feeds back the motor rotation angle from the motor 100 and the reaction force from the force sensor 110. The force sensor 110 that measures the reaction force is installed at the tip of each of the actuators 31 to 34. When lifting a load 50 (for example, a dolly 55), the entire weight is supported by the force sensor 110.

[0047] The identification process is performed in the following order: "Identification of thrust at maximum static friction torque → Identification of the relationship between reaction force and added torque."

[0048] (1) Identification of maximum static friction torque and thrust: The torque reference value is gradually increased from zero, and the torque reference value at which the actuators (31 to 34) start to move is recorded as the maximum static friction torque, and the reaction force measurement value when this torque is pressed against a wall surface is also recorded (first identification process). The identification of the maximum static friction torque itself is the same as in the first embodiment. The motor rotation angle is used to detect the timing at which the motor 100 starts to move.

[0049] (2) Identification of the relationship between reaction force and additional torque: The maximum static friction torque plus the additional torque is used as the torque reference value, and the wall (or a sufficiently heavy car) is pushed by the actuators (31-34). The reaction force measurement value at this time is recorded, and the reaction force measurement value f is calculated as shown in Figure 7(a). res and additional torque τ ad Plot the relationship between (second identification process).

[0050] The relationship in FIG. 7(a) corresponds to the thrust command f cmd and additional torque τ adThe relationship obtained in Fig. 7(b) is used as a conversion function of thrust command versus additional torque, and is substituted for Fig. 5 in the first embodiment.

[0051] That is, the controller 70 in FIG. 6 includes a thrust-additional torque conversion unit 61 and an adder 62 similar to those in FIG. 4, and uses the thrust command f in FIG. 7(b) obtained in the first and second identification processes as a conversion function of the thrust command versus added torque in the thrust-additional torque conversion unit 61. cmd and additional torque τ ad The transformation function of the relationship is set.

[0052] In the second embodiment, the thrust value at the maximum static friction torque and the actual efficiency can be identified, so that more accurate thrust control is possible, compared to the first embodiment. Examples of the results of experiments on the identification of (1) and (2) above are shown below.

[0053] First, as a result of identifying the maximum static friction torque in (1) above, the torques of the four actuators (31-34) were found to be (0.013, 0.011, 0.012, 0.018) [Nm]. Next, by adding additional torque in the identification in (2) above, the relationship between the actuator reaction force measurement value (vertical axis) and the additional torque (horizontal axis) was obtained as shown in Figures 8(a)-(d). Figure 8 shows individual differences between the actuators.

[0054] Based on the correspondence between the reaction force measurement value and the added torque in FIG. 8, a conversion function of thrust command versus added torque in thrust-added torque conversion section 61 in controller 70 in FIG. 6 was set, and an experiment on thrust control was performed.

[0055] In this experiment, the above steps were taken in order: (1) lifter lift (up to 6 seconds after start), then (2) thrust control (after 6 seconds). First, a torque reference value (added with a small torque) corresponding to maximum static friction was applied, and the lift-up operation and contact with the cart were performed. The lifter was raised slowly, which helps to reduce the impact. Contact occurred about 3 seconds after the operation, and after a certain period of time had passed, 6 seconds onwards, the torque reference value was increased to achieve the desired thrust, as shown in (2).

[0056] The experimental results are shown in Figure 9. The top row of Figure 9 shows the average height of each axis of the lifter (COG height), and the bottom row shows the sum of the force sensor (110) outputs for each axis (fres All). A 5 rad / s low-pass filter is inserted into the force sensor output. It can be seen that in the period from 0 to 6 seconds in Figure 9, lifter lift is achieved from the position response, and in the period from 6 to 10 seconds in Figure 9, thrust control is achieved from the force response. The thrust command is 36 kgf, and the force sensor response also indicates approximately 36 kgf.

[0057] According to the second embodiment, the relationship between the thrust and the torque reference value at the time of stationary can be identified. By using this, it is possible to realize the force sensorless thrust control with high accuracy. Compared to the first embodiment, it is possible to identify the actual efficiency and the thrust at the time of the maximum static friction torque, so that it is possible to perform the force control with higher accuracy. EXAMPLES

[0058] Thrust command (thrust command f input to the thrust-additional torque conversion unit 61 in FIG. 4) cmd ) is a constant value, but is often determined by taking into consideration the load, such as a constant multiple of the load. In the third embodiment, in relation to the selection of the thrust command, the estimation of the load without a force sensor is dealt with.

[0059] The overall configuration of the system according to the third embodiment is shown in Fig. 10. In Fig. 10, the same parts as in Fig. 1 and Fig. 6 are denoted by the same reference numerals. A controller 80 in Fig. 10 provides a torque reference value to the motor 100 and feeds back the motor rotation angle from the motor 100, but does not require a force sensor.

[0060] The controller 80 includes a thrust-additional torque conversion unit 61 and an adder 62 shown in FIG. 4, and a load estimation device shown in FIG. 11, which will be described later. The controller 80 calculates a thrust command f, which is an input to the thrust-additional torque conversion unit 61, based on the load estimated by the load estimation device. cmd This determines the

[0061] The load estimation process consists of the following steps: (1)-(3) pre-processing and (4) and (5) load estimation process.

[0062] <Preliminary process> (1) Implement constant speed position control on each actuator axis and lift the load. Record the output of the disturbance observer for each axis at constant speed. The disturbance observer here is assumed to be a standard disturbance observer that takes position and torque reference values ​​as inputs and has a single-inertia system as the reference model. However, the reference model may be changed to suit the plant, for example when the plant is not a single-inertia system. A block diagram of the control of the load estimation device is shown in Figure 11.

[0063] In FIG. 11, 81 indicates the motor angle θ res Convert the variable to the actuator length X res This is a variable conversion unit that outputs (the position response value of the actuator output shaft).

[0064] 82 is the position response value X of each actuator output shaft when the first to fourth actuators are each controlled to rise at a constant speed. res is the actuator length command value X cmd The actuator force reference value F ref This is a position controller that outputs

[0065] 83 is the actuator force reference value F ref The motor torque reference value τ is calculated by variable transformation. ref This is the variable transformation unit that outputs

[0066] 84 is the actuator force reference value F ref and the position response value X of each actuator output shaft res The estimated disturbance (disturbance estimate) F^ is proportional to the actuator load. dis is a disturbance observer that outputs

[0067] 85 is the disturbance estimate F^ of the disturbance observer 84 disto the output of the position controller 82, but this adder 85 may be omitted.

[0068] 86 is the output (F^) of the disturbance observer 84 for the output shaft of each actuator when the load 50 (a controlled object such as a cart) is controlled to rise at a constant speed by the first to fourth actuators. dis ) and the sum of the loads acting on the output shafts of each actuator to obtain the load estimation value W^.

[0069] In this block in FIG. 11, the load W applied to the output shaft of each actuator is estimated.

[0070] (2) The relationship between the sum of the observer outputs and the sum of the loads is plotted through experiments with multiple load patterns, where the sum of the observer outputs is the sum of the outputs of the disturbance observer 84 for the output shafts of the actuators, and the sum of the loads is the sum of the loads applied to the output shafts of the actuators.

[0071] (3) Derive the relationship between the sum of observer outputs and the sum of weights (using least squares method, etc.).

[0072] <Load Estimation Process> (4) The target unknown load (controlled body with unknown load) is lifted by constant speed position control as in (1) above, and the sum of the outputs of the disturbance observer 84 at the constant speed is recorded.

[0073] (5) The output obtained in (4) is substituted into the relational expression between the observer output sum and the weight sum to derive the estimated weight.

[0074] Although it is difficult to identify the friction of an actuator when it is stationary, it is relatively easy to identify dynamic friction, especially when it moves at a constant speed, because the Coulomb friction, which is speed-dependent, is constant. The load estimation in the third embodiment utilizes this property. The equation of motion of the actuator is expressed by equation (1).

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[0075] From equation (4), the output F^ of the disturbance observer 84 dis and the torque reference value τ ref is proportional to the load.

[0076] An example of the experimental results of the load estimation flow is shown below. Regarding the preliminary process (1) and (2), Fig. 12(a) shows the time series response of the sum of the disturbance observer outputs when the load (cart) on the tabletop 40 is changed from 0 to 40 kg. In Fig. 12(a), it can be seen that when the tabletop 40 is being lifted at a constant speed (a period of 6 to 10 s), the sum of the observer outputs is constant and changes according to the load on the tabletop 40.

[0077] As the preliminary process (3), the average of the period of 8 to 10 seconds during which the observer output sum is constant and stable is taken, and the relationship with the load on the tabletop is plotted in Figure 12(b). The approximate straight line obtained here becomes the contents of the load estimator 86 in Figure 11.

[0078] In (4) of the load estimation process, the unknown load is lifted by constant speed position control, and the sum of the outputs of the disturbance observer 84 is recorded.

[0079] In the load estimation process (5), the recorded output sum is compared with FIG. 12(b) to derive the corresponding load.

[0080] In FIG. 12(b) of the approximation line (y=ax+b), y is the sum of the disturbance observer outputs, a is the slope, and x is the load. Therefore, for example, if the sum of the disturbance observer outputs is y(N), the sum of the loads can be estimated to be (yb) / a(kg).

[0081] In this way, the thrust command f in FIG. 4 is calculated by taking into account the load estimated value (W^) estimated by the load estimator 86 in FIG. cmd Determine.

[0082] As described above, according to the third embodiment, the load can be estimated without a force sensor, and the estimation can be applied to the generation of a thrust command in thrust control. EXAMPLES

[0083] The system configuration and the controller configuration of the fourth embodiment are shown in FIG. 10 and FIG. 11, similarly to the third embodiment. In the fourth embodiment, the following equation (4) expressing the sum of the outputs of the disturbance observer is used.

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[0084] (1) The pre-processing steps (1) to (3) of the third embodiment are carried out to obtain the gradient a of the approximation line in FIG. 12(b).

[0085] (2) Torque reference value τ ref Change the thrust conversion gain as Gr = Grn / a.

[0086] By transforming equation (4) into equation (5), the output of the disturbance observer F^ dis can be expressed as a linear function of the load W.

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[0087] According to the fourth embodiment, it becomes possible to identify the conversion gain of thrust (=actual efficiency) from the torque reference value, so that more accurate force control is realized. [Explanation of symbols]

[0088] 10…AGV 20…Foundation 31~34…Actuator 40…Tabletop 50…Luggage 55…Trolley 55a,55b...Wheel 60,70,80...Controller 61...Thrust-additional torque conversion section 62…Addition section 81, 83...Variable conversion section 82...Position controller 84…Disturbance observer 86...Load estimator 100…Motor 110...Force sensor

Claims

1. A base mounted on a movable traveling body; First to fourth actuators are respectively installed at four corners of the base, and the output shafts of the first to fourth actuators are configured to be movable in a direction perpendicular to the surface on the base where the first to fourth actuators are installed; a controlled body disposed opposite to a tip end of each of the output shafts of the first to fourth actuators; a controller that controls motors for driving the first to fourth actuators; The controller has a thrust-to-additional torque conversion unit that converts a thrust command into an additional torque using a conversion function of thrust command to additional torque, and an adder unit that adds a maximum static friction torque to the converted additional torque to output a motor torque reference value, and the output of the adder unit is used as a motor torque reference value for a motor for driving the actuator.

2. The control device for an automated guided vehicle as described in claim 1, characterized in that the controller performs lifter ascent control based on a motor torque reference value using a maximum static friction torque in a positive direction, thrust control based on a motor torque reference value obtained by adding the additional torque and the maximum static friction torque, and lifter descent control based on a motor torque reference value using a maximum static friction torque in a negative direction.

3. The conversion function of the thrust command to the additional torque in the thrust-additional torque conversion unit is expressed as follows: a first identification process in which the motor torque reference value is gradually increased from zero, the motor torque reference value when the actuator starts to move is recorded as a maximum static friction torque, and a value measured by a force sensor of a reaction force when the actuator is pressed against a wall surface with this torque is also recorded; a second identification process is executed to determine a relationship between the maximum static friction torque recorded in the first identification process plus an additional torque as a motor torque reference value, the reaction force measured by a force sensor when the actuator is pressed against a wall surface, and the additional torque; 3. The control device for an automated guided vehicle according to claim 1, wherein the relationship between the reaction force measurement value and the additional torque obtained in the second identification process is converted into a conversion function of the thrust force command versus the additional torque and set.

4. The controller: a position controller that controls the first to fourth actuators so that a position response value of an output shaft of each actuator, obtained by variable-transforming an angle of a motor for driving the actuator when the first to fourth actuators are each controlled to rise at a constant speed, becomes a command value for the length of the actuator, and outputs a force reference value for the actuator; a disturbance observer that receives as input a force reference value of the actuator and a position response value of an output shaft of the actuator, and outputs an estimated disturbance proportional to a load of the actuator; a load estimator that executes a pre-process for setting in advance a relational expression between a sum of outputs of a disturbance observer for an output shaft of each actuator when a controlled object is controlled to ascend at a constant speed by the first to fourth actuators and a sum of loads acting on the output shaft of each actuator, and then estimates a load by substituting the sum of outputs of the disturbance observer for an output shaft of each actuator when a controlled object, the load of which is unknown, is controlled to ascend at a constant speed by the first to fourth actuators into the relational expression; 4. The control device for an automatic guided vehicle according to claim 1, wherein the thrust command is determined based on a load estimated by the load estimation device.

5. The output of the disturbance observer is defined by equation (5): [0050] (where M is the inertia of the actuator, Gr is the conversion gain from the torque reference value of the motor for driving the actuator obtained by variable conversion of the force reference value of the actuator, Grn is the nominal value of the conversion gain Gr from the torque reference value to the thrust, F ｄ ｒｉｃ is kinetic friction, g is gravitational acceleration, and W is the load.

5. The control device for an automated guided vehicle according to claim 4, wherein a gradient a of an approximation straight line expressed by the relational expression set by execution of the pre-process is used to identify a thrust conversion gain Gr from the torque reference value in the equation (5) as Gr = Grn / a.

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