JP2008123116A - Automatic carrier and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic carrier and its control method for automatically correcting any error during traveling to achieve autonomous traveling without using any external sensor. <P>SOLUTION: The moving quantity of each driving unit is calculated during its movement on a route calculated from an input via-point, and the moving quantity of a whole loading platform is calculated by averaging the moving quantity, and when the moving quantity of the loading platform is within an allowable range, the current location of each driving unit is calculated from the moving quantity of the loading platform, and when the moving quantity of the loading platform is beyond an allowable range, the mean value other than the driving unit with an error is defined as the moving quantity of the loading platform so that the current location of each driving unit can be calculated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic conveyance cart and a control method thereof.

  Various automatic transport carts have been developed for the purpose of automating logistics. In particular, the development of an automated transport cart that can automatically move in a given path and direction without a track is underway.

Conventionally, as such an automatic conveyance carriage, two measurement wheels are provided at the front and rear, separately from the driving wheel, under the carriage, and the movement direction in the horizontal axis direction and the vertical axis direction is measured. Is calculated so that it can move autonomously in a route and direction designated in advance (for example, Patent Document 1).
JP-A-5-313735

  However, conventionally, since an external sensor that is not related to the driving wheel, which is a component of the carriage, is used as a measuring wheel, there is a problem that the cost for manufacturing the automatic conveyance carriage is increased. On the other hand, in the case where such an external sensor is not provided, as disclosed in the prior art of Patent Document 1, only a signal from an encoder provided on a drive wheel causes a wheel slip or failure. There has been a problem that position control cannot be detected and an error occurs in position control.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic conveyance carriage capable of autonomously traveling by automatically correcting an error during traveling without using an external sensor and a control method therefor.

  In order to achieve the above object, the present invention provides a plurality of drive means having wheels provided on the bottom surface of the loading platform and independently driving right and left, detection means for detecting the rotation speed of each wheel, and the rotation speed of each wheel. The amount of movement of each of the plurality of driving means is obtained from the amount of movement of each of the driving means, the amount of movement of the loading platform is obtained, and when the amount of movement of the loading platform is within a predetermined allowable range, And a control means for obtaining a current position of each of the driving means from a moving amount.

  In order to achieve the above object, the present invention obtains the amount of movement of a plurality of driving means provided on the lower surface of the loading platform from the number of rotations of wheels independently driven on the right and left sides of the moving means, A moving amount of the loading platform is obtained from a moving amount of the means, and when the moving amount of the loading platform is within a predetermined allowable range, a current position of each driving means is obtained from the moving amount of the loading platform. It is the control method of a conveyance trolley.

  According to the present invention, the movement amount of the entire automatic conveyance carriage is once obtained from the movement amounts of the plurality of drive means, the position of the automatic conveyance carriage is obtained from the movement amount, and the obtained automatic conveyance carriage as a whole is obtained. By re-determining the current position of each driving means using the amount of movement as the current position, the current position of each driving means is automatically corrected. Therefore, it is possible to autonomously travel an accurate automatic transport cart without requiring an external sensor.

  Further, the present invention detects which driving means has a large error when the movement amount of the automatic conveyance carriage obtained from the movement amounts of a plurality of driving means is out of a predetermined allowable range. Since the value is excluded, a more accurate current position can be obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view for explaining the configuration of an automatic conveyance cart to which the present invention is applied, and is a view seen from the bottom of the cart. FIG. 2 is a block diagram for explaining a control system of the automatic conveyance cart. FIG. 3 is a perspective view (a) and a schematic view (b) for explaining the configuration of one drive unit.

  As shown in the figure, the automatic conveyance cart 1 is provided with first to fourth drive units (drive means) 11 to 14 on the lower surface of the loading platform 10. A control device 20 is attached to the lower surface of the loading platform 10. Here, the direction of the arrow F shown in FIG.

  As shown in FIGS. 2 and 3, each drive unit 11-14 has a steering shaft 30, and has two drive wheels (wheels) that rotate independently with respect to the steering shaft 30. The two driving wheels are a left driving wheel DL and a right driving wheel DR. The steering shaft 30 is positioned before the ground point of each drive wheel DL and DR. This is an arrangement for enabling the drive unit to rotate smoothly in the left-right direction.

  An angle sensor 31 is provided on the steering shaft 30. The left drive wheel DL is connected to a first motor 41 that is a power source of the drive wheel and a first encoder 42 (detection means) that measures the movement amount (rotation angle) of the first motor 41. Similarly, the second drive wheel DR and the second encoder 44 (detection means) for measuring the movement amount (rotation angle) of the second motor 43 are also connected to the right drive wheel DR.

  The control device 20 (control means) transfers control signals to and from the angle sensors 31, the first motor 41, the second motor 43, the first encoder 42, and the second encoder 44 of each of the drive units 11-14. So connected. Therefore, a drive signal is output from the control device 20 to the first motor 41 and the second motor 43 of each of the drive units 11 to 14, and the first motor 41 and the second motor 43 are based on the received drive signal. Rotate. On the other hand, from the first encoder 42 and the second encoder 44 of each of the drive units 11 to 14, the measurement results of the rotation angles of the first motor 41 and the second motor 43 are contained in the control device 20. The current position of the automatic conveyance cart 1 is obtained by a method described later, and the first motor 41 of each of the drive units 11 to 14 is automatically moved according to a route input in advance. A drive signal is output to the second motor 43. Such a control device 20 is, for example, a microcomputer.

  In addition, the attachment position of the control apparatus 20 is not restricted to the lower surface of the loading platform 10, and may be an upper surface or a side portion.

  Here, the basic operation of the automatic conveyance cart 1 will be described.

  FIG. 4 is an explanatory view for explaining the movement of the drive wheels in one drive unit and the accompanying traveling direction of the drive unit, and FIG. 5 is an explanatory view for explaining the overall operation of the automatic conveyance carriage 1.

  First, the movement of one drive unit will be described with reference to FIGS.

  When the drive wheels DL and DR of the drive unit 11 (the same applies to the other drive units 12 to 14) rotate to advance in the vector directions indicated by the speeds νli and νri, respectively, DL and DR are opposite to each other in the illustrated example. The direction and speed of movement of the drive unit 11 are determined by the decomposition vectors denoted by νxi and νyi, respectively. Then, the rotation angle wθ of the drive unit 11 is determined by the decomposition vectors νxi and νyi. The rotation angle wθ is an angle centered on the position (control point CP) when the center SP of the steering shaft 30 is used.

  The symbols νl and νr shown in the present specification and drawings indicate the traveling direction (vector direction) and speed (vector length) of each of the driving wheels DL and DR, and νxi and νyi are two-dimensional coordinate systems. The velocity (vector length) resolved in the x and y directions of the control point CP at. The subscript i of each symbol is for identifying each of the first to fourth drive units, and is 1 to 4 when the respective speeds of the respective drive units are distinguished. In the following description, if the drive units are not distinguished from each other, the suffix i may not be added.

  With reference to FIG. 4, the movement and moving direction of each drive wheel DL and DR of the drive unit will be described.

  First, as shown in FIG. 4A, when the speed νl of the drive wheel DL is slower than the speed νr of the drive wheel DR and both drive wheels rotate in the forward direction, the vehicle proceeds forward while turning left (referred to as the previous left). ).

  Next, as shown in FIG. 4B, when the speed νl of the drive wheel DL and the speed νr of the drive wheel DR are the same and both drive wheels rotate in the forward direction, the vehicle moves forward.

  Next, as shown in FIG. 4C, when the speed νl of the driving wheel DL is faster than the speed νr of the driving wheel DR and both driving wheels rotate in the forward direction, the vehicle proceeds forward while turning right (right previous time). Called).

  Next, as shown in FIG. 4D, when the speed νl of the drive wheel DL and the speed νr of the drive wheel DR are the same and rotate in the reverse direction (DL is the reverse direction, DR is the forward direction), the drive unit itself Turns left (referred to as the left line).

  Next, as shown in FIG. 4E, when the speed νl of the drive wheel DL and the speed νr of the drive wheel DR are the same and rotate in the reverse direction (DL is the forward direction, DR is the reverse direction), the drive unit itself Turns right (referred to as right row).

  In the case of FIG. 4D and FIG. 4E, the left-hand or right-hand movement is performed with the automatic conveyance carriage 1 stopped, and thereafter, for example, both in the same manner as in FIG. When the driving wheels rotate in the same direction at the same speed, the automatic conveyance carriage 1 itself moves to the left or right in a direction perpendicular to the F direction in FIG. Further, in the figure, the case where the driving wheels are each rotated to the right or the right as the right direction with respect to the F direction is shown, but the present invention is not limited to this. For example, after the automatic conveyance carriage is stopped, it can be moved in a given angle direction.

  Next, as shown in FIG. 4 (f), when the speed νl of the driving wheel DL is slower than the speed νr of the driving wheel DR and both the driving wheels rotate in the reverse direction, the vehicle moves backward while turning left (left rear). Called times).

  Next, as shown in FIG. 4G, when the speed νl of the drive wheel DL and the speed νr of the drive wheel DR are the same and both drive wheels rotate in the reverse direction, the vehicle moves backward.

  Next, as shown in FIG. 4C, when the speed νl of the driving wheel DL is faster than the speed νr of the driving wheel DR and both the driving wheels rotate in the reverse direction, the vehicle moves backward while turning right (right rear). Called times).

  In each of the above movements, the speed is a vector ν that is a combined vector of νx and νy (the speed of each drive unit is indicated by νi (where i is a natural number of 1 to 4)).

  Next, a method of calculating the speed vector (that is, the angle indicating the speed and the moving direction) of the drive unit that moves as described above will be described.

  5A and 5B are explanatory diagrams for explaining a method of calculating the speed vector of the drive unit. FIG. 5A is a perspective view, and FIGS. 5B and 5C are schematic views.

  As shown in FIG. 5A, the radius of the drive wheel (distance from the ground point to the axle center) is r, the rotation angle of the drive wheel is θli for the left drive wheel, and θri for the right drive wheel. Here, the rotation angle of the drive wheel is a value acquired from the first encoder 42 and the second encoder 44. It is easier to understand the rotation angles θli and θri in an angle unit (an angle in which 360 degrees is one rotation) in actual calculation. However, the present invention is not limited to this. For example, when a pulse encoder is used, the rotation angle is counted. It may be the number of pulses itself.

  In order to obtain the moving amount of each driving wheel from the signals from the first and second encoders 42 and 44, the moving amount of the left driving wheel DL is Δdli = Δθli × r, and the moving amount of the right driving wheel DR is Δdri = Δθri ×. It is calculated as r.

  As shown in FIG. 5B, the movement amount Δd of the unit center position (intermediate between the drive wheels) parallel to the reference direction of the entire drive wheel (the F direction in FIG. 1 is the positive direction of the reference direction). Can be obtained by Δd = (Δdli + Δdri) / 2. The rotation angle Δθ of the entire drive wheel is Δθ = (Δdli−Δdri) / D (where D is the distance between the center of the drive wheel DL and the center of DR).

  Further, when rotation is applied to the drive unit, the rotation center O has a relationship of Δdli: Δdri = ΔLi: ΔRi (where ΔLi is a distance from the drive wheel DL to the rotation center O, and ΔRi is rotated from the drive wheel DR). Distance to center O. D = ΔLi + ΔRi). Therefore, the rotation center O is at a position of ΔLi = (D × (Δdli / Δdri)) / (1+ (Δdli / Δdri)) from the relationship of ΔLi = ΔRi × (Δdli / Δdri) and D = ΔLi + ΔRi.

  The rotation center O is defined as a position where the rotation axis is XJ, a position moved from the rotation axis XJ by Δdli parallel to the reference direction at the position of the left drive wheel DL, and a position of the right drive wheel DR from the rotation axis XJ. This is the point O where the line segment ΔXJ connecting the position moved by Δdri parallel to the direction intersects with the rotation axis XJ.

  As shown in FIG. 5C, the amount of movement of the control point CP of the drive unit accompanying the rotation is as follows. The segment O-CP drawn from the rotation center O to the control point CP is set to the rotation center O as a fulcrum. This is the amount of movement ΔCP when the position of CP is moved by the rotation angle Δθ.

  Then, the movement amount of the control point CP becomes the combined vector ΔS of the vector Δd and the vector ΔCP, and the current movement amount ΔCP at the control point CP of the drive unit for which the position of the end point (tip point of the arrow) of the vector ΔS is obtained. . If this ΔCP is added to the previous position, the current position after the operation of the drive unit is obtained.

  The movement amount ΔCPi (where i is a natural number of 1 to 4) of each drive unit 11 to 14 calculated as described above is calculated by the control device 20. And the control apparatus 20 calculates the movement amount of the automatic conveyance trolley 1 whole further based on this. Further, using the steering angle obtained from the angle sensor 31, a vector wθ indicating the direction of each drive unit 11 to 14 from the reference point of the automatic conveyance vehicle 1 is obtained. That is, a vector obtained by adding wθ (rotated by wθ) to ΔS and ΔCPi is a drive unit vector viewed from the reference position of the automatic conveyance carriage 1.

  6 and 7 are explanatory diagrams for explaining a method of calculating the movement amount of the entire automatic conveyance vehicle 1.

  As shown in FIG. 6, the movement amount of the entire automatic conveyance carriage 1 is calculated from the center SP of the steering shaft 30 to the center position OO (of the automatic conveyance carriage 1 with respect to the obtained movement amounts ΔCPi of the drive units 11 to 14. It can be obtained from the geometrical arrangement up to the reference point of the loading platform 10). That is, the positions of the centers SP1 to SP4 of the steering shafts 30 of the drive units 11 to 14 are attached at intervals of X1 to X4 in the x-axis direction from the center position OO of the automatic conveyance carriage 1, respectively. It is attached to the direction at intervals of Y1-4.

  Accordingly, the movement amount of the automatic conveyance carriage 1 obtained from the movement amount ΔCPi of each drive unit 11 to 14 is decomposed into the movement amount ΔCPi of each drive unit 11 to 14 in the x-axis direction and the y-axis direction, respectively. Is subtracted from X1 to X4 and Y1 to Y4 in the y-axis direction.

  If there is no error in the operation of each drive unit 11-14, the movement amount of the automatic conveyance carriage 1 obtained from the movement amount ΔCPi of each drive unit 11-14 should match. However, in reality, an error such as slip (details will be described later) occurs, and the movement amount of the automatic conveyance carriage 1 obtained from the movement amount ΔCPi of each drive unit 11 to 14 does not match.

  Therefore, in the present embodiment, the movement amount of the automatic conveyance carriage 1 obtained from the movement amount ΔCPi of each drive unit 11 to 14 is the movement amount (estimated) of the automatic conveyance carriage 1 obtained from the movement amount ΔCPi of each drive unit 11 to 14. Each value of (movement amount) is simply calculated as an arithmetic average, and is used as the movement amount Save of the automatic conveyance carriage 1. The current position after the movement is a value obtained by adding the value of the movement amount Save to the previous current position.

  Then, as shown in FIG. 7, the movement amount Save of the automatic conveyance carriage 1 obtained by averaging is set as the center position OO of the automatic conveyance carriage 1, and this time, each drive unit 11 is geometrically determined from the position of Save = OO. The current positions SS1 to SS4 of the drive units 11 to 14 with respect to Save = OO are calculated by calculating backward from the relationship between the center position of -14 and the center position of the automatic transport cart 1.

  By subtracting the current positions SS1 to SS4 of each drive unit from the average value Save, the subtle difference in position between the drive units is automatically corrected. Then, the obtained current positions SS1 to SS4 of the drive units 11 to 14 become current positions of the drive units for moving to the next path point (details will be described later).

  Of the errors generated in each of the drive units 11 to 14, those that are not large can be used as they are, but if a large error occurs, the cause of the automatic conveyance carriage 1 being off the path. It becomes.

  Therefore, in the present embodiment, the future movement is controlled depending on whether or not the value of the movement amount Save of the automatic conveyance carriage 1 obtained by averaging the movement amounts of the respective drive units is out of the predetermined allowable range dmax. It was decided to determine whether it was possible.

  Here, the allowable range dmax changes depending on how much the automatic conveyance carriage 1 may deviate from a route given in advance when the automatic conveyance cart 1 autonomously travels. In addition, an error not caused by a failure such as a slip increases as the speed of the automatic conveyance carriage 1 increases, so that the allowable range dmax needs to be changed according to the speed.

  Therefore, in the present embodiment, the allowable range dmax is a range of a circle having a radius of the target speed × the control sampling period with the next target point in the traveling direction as the center. By setting in this way, only errors such as slip depending on the speed can be allowed.

  For example, when the target maximum speed of the automatic conveyance carriage 1 is 1 m / s, if the allowable deviation during the traveling is 5 mm, and the control sampling period is 0.02, the allowable range dmax is set to the next target point. The center is a circle having a radius of 0 to 1 (m / s) × 0.02 sec. Of course, the allowable range dmax may be changed as appropriate depending on the purpose of the automatic conveyance cart 1 and the target speed. A via point or an interpolation point to be described later may be used, or a point advanced by the current speed × the control sampling period in the direction of the via point and the interpolation point with respect to the current position may be set separately from the interpolation store.

  In this way, when the allowable range dmax is provided and the value of the movement amount Save of the automatic conveyance carriage 1 exceeds the allowable range dmax, it is assumed that a large error has occurred in any of the drive units, and a large error has occurred. By not using the movement amount ΔSi of the drive unit that is used for calculating the average value, the calculation accuracy of the current position of the automatic conveyance cart 1 can be increased.

  However, it is impossible to determine which drive unit has a large error only by the value of the movement amount Save of the automatic conveyance carriage 1 obtained by averaging the movement amounts ΔSi of all the drive units. Therefore, in this embodiment, an average value is obtained only from other drive units except for one drive unit, and a drive unit having a large error is determined depending on whether the average value exceeds the allowable range dmax. . This means that if the average value calculated only from the other drive units excluding one drive unit does not exceed the allowable range dmax, the drive unit removed at that time is the source of a large error. Is.

  On the other hand, even when there is a drive unit in which such a large error has occurred, the automatic conveyance carriage 1 is provided with a plurality of drive units, so that a slip or the like occurs in the drive unit in which a large error has occurred. However, the traveling direction of the automatic conveyance carriage 1 itself does not increase greatly. However, if the movement amount of the drive unit having a large error is added, the movement amount (that is, the current position) of the automatic conveyance carriage 1 is increased. This is eliminated because a nuisance occurs in the calculation.

  Specifically, a comparison is made between the values Save1 and dmax averaged using the values of the movement amounts ΔS2 to 4 of the other drive units except for the movement amount ΔS1 of the first drive unit 11, and similarly the second drive unit. A comparison is made between the values Save2 and dmax averaged using the values of the movement amounts ΔS1, ΔS3 and ΔS4 of the other drive units except for the movement amount ΔS2 of 12, and similarly, the movement amount ΔS3 of the third drive unit 13 is excluded. A comparison is made between the value Save3 averaged using the movement amounts ΔS1, ΔS2 and ΔS4 of the other drive units and dmax. Similarly, except for the movement amount ΔS4 of the fourth drive unit 14, A comparison is made between the values Save4 and dmax averaged using the values of the movement amounts ΔS1 to ΔS3. If there is a Savei that does not exceed dmax among these Saves 1 to 4 (where i is 1 to 4), it is determined that the drive unit excluded at that Savei has caused a large error.

  Errors that occur in each drive unit include, for example, slipping of the drive wheels, insufficient air pressure and puncture when the drive wheels are inflated tires, differences in wear when the drive wheels are solid rubber tires, and between multiple drive units. Is generated by an internal force due to a difference in speed of the steering shaft 30, an internal force due to a difference in angle of the steering shaft 30, an internal force due to a difference in direction of the angle sensor 31 provided on the steering shaft 30, an error of the angle sensor 31, and the like.

  FIG. 13 is an explanatory diagram for explaining a difference in speed among a plurality of drive units, and FIG. 13 is an explanatory diagram for explaining an internal force due to a difference in angle of the steering shaft 30.

  As shown in FIG. 12A, for example, when the speed ν1 of the first drive unit is higher than the third drive unit speed ν3, the combined speed sν is ν1 as shown in FIG. Slower and faster than ν3. For this reason, a speed difference will arise between these drive units. Similarly, as shown in FIG. 12B, for example, when the speed ν1 of the first drive unit 11 is slower than the speed ν3 of the third drive unit 13, these combined speeds sν are faster than ν1 and slower than ν3. Thus, a speed difference occurs between these drive units.

  Such a speed error causes the drive unit that rotates faster to slip and causes an error in calculating the current position.

  On the other hand, as shown in FIG. 13A, the internal force due to the difference in the angle of the steering shaft 30 is obtained when the velocity vectors of the first drive unit 11 and the second drive unit 12 are inward of each other, or in FIG. As shown in b), it occurs when the velocity vectors of the first drive unit 11 and the second drive unit 12 are outward. In the inward direction, forces acting on the outside are generated, the first drive unit 11 generates a force in the direction eθ1 <0, and the second drive unit 11 generates a force in the direction eθ1> 0. . On the other hand, when they are directed outward, forces acting inside each other are generated, the first drive unit 11 generates a force in the direction eθ1> 0, and the second drive unit 11 generates a force in the direction eθ1 <0. appear.

  When such an internal force occurs, each drive unit will slip by the applied force, and if the turning angle of the steering shaft 30 changes and the balance of the force is lost, the drive unit rotates in either direction. It will move. For this reason, the internal force due to such a difference in the angle of the steering shaft 30 also causes an error in calculating the current position.

  Next, overall control when the automatic conveyance cart 1 autonomously travels will be described.

  FIG. 8 is a flowchart showing an operation procedure of the control device 20 when the automatic conveyance cart 1 autonomously travels.

  First, the control device 20 receives an input of a traveling course (S1). The course input at this time may be only a typical route point of the route scheduled to travel and an interpolation method between the route points.

  FIG. 9 is an explanatory diagram of this route point and an interpolation instruction between the route points.

  As shown in FIG. 9, the traveling course is set and input as a waypoint through some points on the route on which the automatic conveyance cart 1 is to be run, and further, an interpolation instruction is given as to how to travel between the waypoints. Enter as. As the via point, the start point and end point of the route and the position where the route bends between them are usually input. Then, linear interpolation is instructed where it is necessary to go straight between the via points, and circular interpolation is instructed at a bent portion.

  Next, the control device 20 performs target trajectory generation and target speed / target rotation speed calculation based on the input via point and interpolation instruction (S2).

  FIG. 10 is an explanatory diagram of target trajectory generation and target speed / target rotation speed calculation.

  As shown in the figure, in the section in which linear interpolation is instructed, as shown in FIG. 10A, the speed gradually increases from the first waypoint (t = 0 s) as the target speed, and the intermediate point between the waypoints. The interpolation point is set so that the point is accelerated to the point (t = 10 s) and gradually becomes slower from the intermediate point to the end point (t = 20 s) at the end of the section in which linear interpolation is instructed. However, the maximum speed shall not exceed the maximum speed during straight running.

  On the other hand, in the section in which circular interpolation is instructed, the target speed basically increases from the first waypoint (t = 20 s) in the same section as in the case of linear interpolation. The acceleration point is set to (t = 30 s), and the interpolation point is set so as to gradually become slower from the intermediate point to the end point of the section (t = 40 s). However, the maximum speed shall not exceed the maximum speed during arc traveling.

  As shown in FIG. 10B, the speed ν during arc traveling set at this time is decomposed into a target rotational speed using a two-dimensional coordinate system into a speed νxj in the x-axis direction and a speed νyj in the y-axis direction. To do. In addition, w (theta) shows the direction of a drive unit in a figure, and is the steering angle of the present attitude | position of the automatic conveyance trolley | bogie 1 + a drive unit. Here, the current posture of the automatic conveyance carriage 1 is the direction of the automatic conveyance carriage 1 obtained from the current position, and the steering angle is a value obtained from the angle sensor 31 of each drive unit.

  Thereby, since preparations for traveling are completed, the control device 20 can cause the automatic conveyance cart 1 to travel if there is a traveling command (not shown).

  When the automatic carriage 1 is traveling, the control device 20 commands the drive wheels of the drive units to have the same speed so that the target speed of the linear section is the same in the straight section. Instructs the speed of each drive wheel of each drive unit to be the target speed and target rotational speed of the arc section.

  FIG. 11 is an explanatory diagram for explaining a speed command for an arc segment.

  In the arc section, as shown in FIG. 11A, the arc center position ICR of the section is determined in advance (designated as the arc center position ICR commanded in the arc interpolation command). Since the target rotational speed is calculated as a circular arc in which the distance r0 from the ICR to the center position of the automatic conveyance carriage 1 moves, it must be distributed to the respective drive units 11-14. If the distance from the ICR to the control point CP of each drive unit is ri, the target speed νi = ν + wθ × ri of each drive unit is obtained.

  As shown in FIG. 11B, the control device 20 distributes and commands the obtained target speed νi of each drive unit to the speed of each drive wheel in each drive unit.

  The target speed νi of each drive unit can be obtained by the following equation (1).

From νi = wj · ui, ui = wj− ¹ · νi (1)
Where ui is the speed of each drive wheel in one drive unit. Therefore, the subscript i of ui is 1 or 2, for example, u1 = speed of the left driving wheel and u2 = speed of the right driving wheel.

  ui is obtained by the following equation (2).

Wj ⁻¹ represents a Jacobian matrix, and is represented by the following equation (3).

  In the equations (2) and (3), the dot θli indicates the rotation speed of the left driving wheel, and the dot θri indicates the rotation speed of the right driving wheel (the dot is a symbol indicating that it is a differential value as shown in the equation and the figure). is there). Further, r is the radius of the drive wheel (wheel), and θ (no dot) is the rotation angle of the drive wheel (wheel). Further, s is a distance from the steering shaft to the axle and is called an offset amount.

  When traveling starts, the control device 20 calculates the movement amount ΔCPi of each drive unit as already described (S10). The interval for obtaining the amount of movement depends on a predetermined control sampling period.

  Then, the control device 20 calculates an average value Save of the movement amounts at the center position OO of the automatic conveyance carriage 1 from the obtained movement amounts ΔCPi of the drive units 11 to 14 (S11), and the value is within the allowable range dmax. If so (S12: Yes), the current position of each drive unit 11-14 is calculated based on the average value Save (S15).

  On the other hand, if the average value Save exceeds the allowable range dmax (S12: No), it is detected which drive unit has a large error (S14). As described above, the average value Savei is obtained from the drive units excluding one drive unit as described above, and if the obtained average value Savei is within the allowable range dmax, the error of the drive unit excluded at that time is Judge as big. The control device 20 sets the average value Savei within the allowable range dmax as the average value Save at that time (S15: an average value excluding a drive unit having a large error), and the drive units 11 to 14 from the average value. Is calculated (S15).

  Subsequently, the control device 20 determines whether or not the current position has reached the route end point (S16). If the end point has not been reached, the control device 20 calculates the target speed and direction from the current position to the target point. Then, a command is given to each drive unit (S17). The target point here is the next interpolation point on the path. Thereafter, the process returns to S10 and continues.

  On the other hand, if it is determined in S16 that the route end point has been reached, the process is terminated.

  As described above, according to the present embodiment, the movement amount Save of the automatic conveyance carriage 1 as a whole is obtained by averaging the movement amounts of the respective drive units 11 to 14, thereby requiring an external sensor other than the drive wheels. First, the position of the automatic conveyance carriage 1 can be obtained, and the current movement amount Save of the automatic conveyance carriage 1 as a whole is fed back to the current position of the drive unit as the current position, thereby automatically correcting the current position. Will be done.

  Further, if the movement amount Save of the automatic conveyance carriage 1 exceeds the allowable range dmax, it is determined which drive unit has a large error and excludes a large value of the error. The position can be determined.

  Although the embodiment to which the present invention is applied has been described above, the present invention is not limited to such an embodiment. For example, although the case where there are four drive units has been described in the above-described embodiment, the present invention can be applied even when there are three drive units. In the above-described embodiment, when detecting a drive unit having a large error, the movement amounts of the other three drive units excluding the movement amount of one drive unit are averaged. You may make it exclude the moving amount | distance of two drive units.

  Further, when a drive unit having a large error is detected in the above-described embodiment, the drive unit is stored in the control device, and thereafter, it is determined that the same drive unit continuously has a large error. In such a case, a warning may be displayed noting that the drive unit has a problem due to a failure or the like rather than a simple slip.

  The present invention can be used for a self-propelled carriage.

It is the schematic for demonstrating the structure of the automatic conveyance trolley to which this invention is applied. It is a block diagram for demonstrating the control system of an automatic conveyance trolley | bogie. It is a perspective view for demonstrating the structure of one drive unit. It is explanatory drawing explaining the movement of the drive wheel in one drive unit, and the advancing direction of the drive unit accompanying it. It is explanatory drawing explaining the calculation method of the speed vector of a drive unit. It is explanatory drawing explaining the calculation method of the movement amount of the whole automatic conveyance trolley | bogie. It is explanatory drawing explaining the calculation method of the movement amount of the whole automatic conveyance trolley | bogie. It is a flowchart which shows the operation | movement procedure of a control apparatus when an automatic conveyance trolley runs autonomously. It is explanatory drawing about a route point and the interpolation instruction | indication between them. It is explanatory drawing about target locus | trajectory production | generation and calculation of a target speed and target rotational speed. It is explanatory drawing explaining the speed command of a circular arc area. It is explanatory drawing explaining the difference in the speed between several drive units. It is explanatory drawing explaining the internal force by the difference in the angle of a steering shaft.

Explanation of symbols

1 ... Automatic transport cart,
10 ... loading platform,
20 ... Control device,
30 ... Steering shaft,
31 ... An angle sensor,
41 ... 1st motor,
42 ... first encoder,
43 ... second motor,
44. Second encoder.

Claims (6)

A plurality of driving means having wheels provided on the bottom surface of the loading platform and independently driven on the left and right sides;
Detecting means for detecting the rotational speed of each wheel;
The amount of movement of each of the plurality of driving means is obtained from the number of rotations of each wheel, the amount of movement of the cargo bed is obtained from the obtained amount of movement of each driving means, and the amount of movement of the cargo bed is within a predetermined allowable range. Control means for obtaining the current position of each driving means from the amount of movement of the loading platform,
An automatic conveyance cart characterized by comprising:   The movement amount of the loading platform is obtained by obtaining an estimated movement amount at the reference point of the loading platform for each driving means from the movement amount of each driving means and the mounting position of each driving means on the loading platform. The automatic conveyance cart according to claim 1, wherein the average value is an average value.   When the movement amount of the loading platform is outside the allowable range, the control means obtains the average value from the movement amount of the remaining driving means excluding the movement amount of at least one driving means when obtaining the average value, 3. The automatic conveyance cart according to claim 2, wherein if the obtained average value is within an allowable range, it is determined that the error of the driving means excluded at that time is large. The amount of movement of the plurality of driving means provided on the lower surface of the loading platform is obtained from the number of rotations of the wheels that are independently driven on the left and right provided on the moving means,
Obtain the amount of movement of the cargo bed from the amount of movement of each driving means that has been obtained,
A control method for an automatic conveyance cart, wherein when the movement amount of the loading platform is within a predetermined allowable range, the current position of each of the driving means is obtained from the movement amount of the loading platform.   The movement amount of the loading platform is obtained by obtaining an estimated movement amount at the reference point of the loading platform for each driving means from the movement amount of each driving means and the mounting position of each driving means on the loading platform. 5. The method for controlling an automatic conveyance carriage according to claim 4, wherein the average value is an average value of   When the movement amount of the loading platform is outside the allowable range, the average value is obtained from the movement amount of the remaining driving means excluding the movement amount of at least one driving means when obtaining the average value, and the obtained average 6. The method for controlling an automatic conveyance carriage according to claim 5, wherein if the value is within an allowable range, it is determined that the error of the drive means excluded at that time is large.