Dolly

Abstract

To provide a carriage whose wheels hardly slip and which can be turned properly.SOLUTION: A carriage 1 is provided with: a carriage body 2; a pair of left and right wheels 3 provided in the carriage body; left and right driving units 4 that respectively drive the wheels which are driven; a steering wheel 5 provided in the carriage body, which receives operation by a user; a sensor 6 that detects longitudinal loads applied to the steering wheel and moment around a vertical shaft; and a control device 7 that controls the driving units. The control device sets a target speed in a longitudinal direction of the carriage body on the basis of the detected longitudinal loads, and sets a target angular velocity around the vertical shaft of the carriage body on the detected moment around the vertical shaft, which when products of the target speed in the longitudinal direction and the target angular velocity are larger than a predetermined threshold, performs a correction process the target speed in the longitudinal direction so that the products of the target speed in the longitudinal direction and the target angular velocity are below the threshold, and controls the driving units on the basis of the corrected target speed in the longitudinal direction and the target angular velocity.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a carriage.

Background Art

[0002] Patent Document 1 discloses a power assist carriage having a handle for detecting an operating force of a user and power assist control means for driving drive wheels for traveling and steering based on the operating force input to the handle.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a carriage such as that of Patent Document 1, if the forward / rearward speed and angular velocity become too high during turning, the centrifugal force applied to the drive wheels increases, and there is a risk of drive wheel slip.

[0005] In view of the above background, an object of the present invention is to provide a carriage in which the wheels are difficult to slip and an appropriate turning operation can be performed.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention provides a trolley (1) comprising a body (2), a pair of left and right wheels (3) provided on the body, left and right drive units (4) that drive each of the wheels, a handle (5) provided on the body that receives user input, a sensor (6) that detects the front-rear load and moment around the vertical axis applied to the handle, and a control device (7) that controls the drive units, wherein the control device sets a target front-rear speed of the body based on the front-rear load, sets a target angular velocity of the body around the vertical axis based on the moment around the vertical axis, and when the product of the target front-rear speed and the target angular velocity is greater than a predetermined threshold, it corrects the target front-rear speed so that the product of the target front-rear speed and the target angular velocity is less than or equal to the threshold, and controls the drive units based on the corrected target front-rear speed and the target angular velocity.

[0007] According to this embodiment, the target longitudinal speed is corrected so that the product of the target longitudinal speed and the target angular speed is less than or equal to a predetermined threshold, thereby providing a trolley that is less prone to wheel slippage and can perform appropriate turning maneuvers.

[0008] In the above embodiment, preferably, the control device corrects the target forward and backward velocity in the correction process to a value less than or equal to the value obtained by dividing the threshold by the target angular velocity.

[0009] According to this embodiment, the control device can easily correct the target longitudinal speed.

[0010] To solve the above problems, one aspect of the present invention provides a trolley (1) comprising a body (2), a pair of left and right wheels (3) provided on the body, left and right drive units (4) that drive each of the wheels, a handle (5) provided on the body that accepts user input, a sensor (6) that detects the front-rear load and moment around the vertical axis applied to the handle, and a control device (7) that controls the drive units, wherein the control device sets a target front-rear speed of the body based on the front-rear load, sets a target angular velocity of the body around the vertical axis based on the moment around the vertical axis, and when the product of the target front-rear speed and the target angular velocity is greater than a predetermined threshold, it corrects the target angular velocity so that the product of the target front-rear speed and the target angular velocity is less than or equal to the threshold, and controls the drive units based on the corrected target angular velocity and the target front-rear speed.

[0011] According to this embodiment, the target angular velocity is corrected so that the product of the target longitudinal velocity and the target angular velocity is less than or equal to a predetermined threshold, thereby providing a trolley that is less prone to wheel slippage and can perform appropriate turning maneuvers.

[0012] In the above embodiment, the control device may, in the correction process, correct the target angular velocity to a value less than or equal to the value obtained by dividing the threshold by the target velocity before and after the target.

[0013] According to this embodiment, the control device can easily correct the target longitudinal speed.

[0014] To solve the above problems, one aspect of the present invention provides a trolley (1) comprising a body (2), a pair of left and right wheels (3) provided on the body, left and right drive units (4) that drive each of the wheels, a handle (5) provided on the body that receives user input, a sensor (6) that detects the front-rear load and moment around the vertical axis applied to the handle, and a control device (7) that controls the drive unit, wherein the control device sets a target front-rear speed of the body based on the front-rear load, sets a target angular velocity of the body around the vertical axis based on the moment around the vertical axis, and when the product of the target front-rear speed and the target angular velocity is greater than a predetermined threshold, it corrects the target angular velocity and the target angular velocity so that the product of the target front-rear speed and the target angular velocity is less than or equal to the threshold, and controls the drive unit based on the corrected target angular velocity and the corrected target front-rear speed.

[0015] According to this embodiment, the target longitudinal speed and target angular velocity are corrected so that the product of the target longitudinal speed and target angular velocity is less than or equal to a predetermined threshold, thereby providing a trolley that is less prone to wheel slippage and can perform appropriate turning maneuvers.

[0016] In the above embodiment, preferably, the control device corrects the target longitudinal velocity by replacing it with a longitudinal velocity correction value vt1' that satisfies the following equation (1) and the target angular velocity with an angular velocity correction value ωt' that satisfies the following equation (2), when the threshold is Th, the target longitudinal velocity is vt1, and the target angular velocity is ωt.

number

[0017] According to this embodiment, the control device can easily correct the target longitudinal speed.

[0018] In the above aspect, the mass of the carriage is m, the distance in the longitudinal direction of the vehicle from the center of gravity to the wheel is L1, the distance in the vehicle width direction from the center of gravity to the wheel is L2, and the maximum static friction force F , , , , , , , , , , , , [Figure 3] , [Figure 2] , [Figure 8] , [Figure 1] , [Figure 7] ,

[0023] , [Figure 6] , , [Figure 5] , , [Figure 4] ,

[0022] , of the floor surface for each of the wheels, and the propulsion force F(i) (where i is an argument indicating the number of the wheel) of each of the wheels with respect to the floor surface, the threshold Th may be set to be less than or equal to the minimum value of the upper limit value τ(i) represented by Equation (3).

Equation

[0019] According to this aspect, the threshold can be set appropriately and simply.<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Flowchart showing the control procedure executed by the control device according to the second embodiment. [Figure 9] Flowchart showing the control procedure executed by the control device according to the third embodiment. [Figure 10] Flowchart showing a modified example of the control procedure performed by the control device according to the first embodiment. [Figure 11] A schematic diagram showing the propulsive force of the omnidirectional wheels 3, the centrifugal force of the bogie, and the couple when the bogie is moving backward. [Modes for carrying out the invention]

[0024] <<First Embodiment>> Hereinafter, an embodiment of the trolley according to the present invention will be described with reference to the drawings. Hereinafter, each direction will be defined with the trolley as the reference point.

[0025] As shown in Figure 1, the trolley 1 comprises a body 2, at least one omnidirectional wheel 3 provided on the body 2 that moves the body 2 in all directions along the floor surface, a drive unit 4 that drives each of the omnidirectional wheels 3, a handle 5 provided on the body 2 that receives input from the user, a force sensor 6 that detects the load applied to the handle 5, and a control device 7 that controls the drive unit 4 based on the load detected by each of the force sensors 6.

[0026] The vehicle body 2 extends in the front and rear directions. The rear part 2A of the vehicle body 2 extends upward above the front part 2B. The front part 2B of the vehicle body 2 is provided with a support base 11 for supporting other devices. The devices supported by the support base 11 include, for example, inspection equipment such as an X-ray scanner. The devices may be fastened to the support base 11. Inside the rear part 2A of the vehicle body 2, a control device 7, a battery, and various sensors may be provided.

[0027] In this embodiment, a pair of omnidirectional wheels 3 are provided at the lower part of the rear 2A of the vehicle body 2. In addition, left and right casters 13 are supported at the lower part of the front 2B of the vehicle body 2 via a suspension. The suspension is located below the vehicle body 2 and has arms 14 that extend to the left and right, and a spring 15 and a shock absorber 16 positioned between the vehicle body 2 and the arms 14. Each caster 13 is located below the left and right ends of the arms 14. Each caster 13 has a fork 13A that is rotatably coupled to the arm 14 about an axis that extends vertically, and a wheel 13B that is rotatably supported on the fork 13A about an axis that extends horizontally. The fork 13A rotates freely relative to the arm 14, and the wheel 13B rotates freely relative to the fork 13A.

[0028] As shown in Figure 2, the pair of omnidirectional wheels 3 are positioned with a gap between them to the left and right. In this embodiment, the pair of omnidirectional wheels 3 are positioned on the lower left and lower right of the rear 2A of the vehicle body 2. As shown in Figure 3, each omnidirectional wheel 3 has a frame 17, a pair of drive discs 18 rotatably supported by the frame 17, and an annular main wheel 19 positioned between the pair of drive discs 18.

[0029] As shown in Figures 1 and 3, the frame 17 has an upper frame 17A connected to the lower part of the vehicle body 2, and a pair of side frame portions 17B extending downward from both the left and right ends of the upper frame portion 17A. A support shaft 21 extending from left to right is spanned across the lower ends of the pair of side frame portions 17B. A pair of drive disks 18 are rotatably supported on the support shaft 21. The pair of drive disks 18 rotate about the axis Y1 of the support shaft 21. The position of each drive disk 18 in the left-right direction is restricted with respect to the support shaft 21. The drive disks 18 face each other at a distance in the left-right direction.

[0030] The drive disks 18 are positioned on either side of the annular main wheel 19, and apply frictional force to the main wheel 19, causing it to rotate around its central axis and annular axis. The drive disk 18 has a disc-shaped base 18A that is rotatably supported by the frame 17, and a plurality of drive rollers 18B that are rotatably supported on the outer circumference of the base 18A at an angle to each other and in contact with the main wheel 19. The base 18A is positioned coaxially with the support shaft 21.

[0031] Driven pulleys 18C are provided on opposite sides of each drive disk 18. The driven pulleys 18C are mounted coaxially with the drive disks 18. The drive unit 4 is located at the bottom of the vehicle body 2 and has a plurality of electric motors 25 corresponding to each drive disk 18. In this embodiment, four electric motors 25 are provided corresponding to four drive disks 18. A drive pulley 26 is provided on the output shaft of each electric motor 25. The corresponding drive pulleys 26 and driven pulleys 18C are connected by a belt 27. Each electric motor 25 rotates independently of each other, causing each drive disk 18 to rotate independently of each other.

[0032] As shown in Figure 4, the main wheel 19 is annular in shape, coaxially positioned between a pair of drive disks 18, in contact with a plurality of drive rollers 18B, and rotatable around a central axis and an annular axis. The main wheel 19 has an annular core 31 and a plurality of driven rollers 32 rotatably supported on the core 31. The plurality of driven rollers 32 are arranged at equal intervals in the circumferential direction of the core 31. Each driven roller 32 is rotatably supported on the annular core 31 about the axis A1 (annular axis) of the annular core 31. Each driven roller 32 can rotate about a tangent to the core 31 at its respective position relative to the core 31. Each driven roller 32 rotates relative to the core 31 when subjected to an external force.

[0033] The main wheel 19 is positioned along the outer circumference of a pair of drive disks 18 and is in contact with a plurality of drive rollers 18B provided on each drive disk 18. The drive rollers 18B of each drive disk 18 are in contact with the inner circumference of the main wheel 19, clamping the main wheel 19 from both the left and right sides. In addition, the drive rollers 18B of the left and right drive disks 18 restrict the radial displacement of the drive disks 18 around the axis Y1 by contacting the inner circumference of the main wheel 19. As a result, the main wheel 19 is supported by the left and right drive disks 18, and the central axis of the main wheel 19 (core body 31) is positioned coaxially with the axis Y1 of the left and right drive disks 18. The main wheel 19 is in contact with a plurality of drive rollers 18B of the left and right drive disks 18 at the plurality of driven rollers 32.

[0034] In each omnidirectional wheel 3, when a pair of drive discs 18 rotate in the same direction at the same rotational speed, the main wheel 19 rotates together with the pair of drive discs 18. That is, the main wheel 19 rotates forward or backward around its own axis of rotation, which coincides with the axis Y1. At this time, the drive rollers 18B of the drive discs 18 and the driven rollers 32 of the main wheel 19 do not rotate relative to the core body 31. In each omnidirectional wheel 3, when there is a difference in rotational speed between a pair of drive discs 18, a component force perpendicular to the circumferential (tangential) force caused by the rotation of the pair of drive discs 18 acts from the left and right drive rollers 18B to the driven rollers 32 of the main wheel 19. Because the axis of the drive roller 18B is inclined with respect to the circumferential direction of the drive roller 18B, a component force is generated between the drive discs 18 due to the difference in rotational speed. This component force causes the drive roller 18B to rotate relative to the base 18A, and the driven roller 32 to rotate relative to the core body 31. As a result, the main wheel 19 generates a driving force in the left-right direction.

[0035] The trolley 1 moves forward as the left and right omnidirectional wheels 3 rotate forward at the same speed. The trolley 1 moves backward as the left and right omnidirectional wheels 3 rotate backward at the same speed. The trolley 1 turns to the right or left as speed is generated in the forward and backward rotation of the left and right omnidirectional wheels 3. The trolley 1 moves parallel to the right or left as the driven rollers 32 of each main wheel 19 of the left and right omnidirectional wheels 3 rotate.

[0036] As shown in Figures 1 and 2, a handle holder 35 protruding upward is provided on the upper part of the rear 2A of the vehicle body 2. The handle 5 is supported by the handle holder 35 via a force sensor 6. The force sensor 6 is preferably a three-axis force sensor that detects loads along two mutually orthogonal axes on the horizontal plane and a moment about the vertical axis (z axis). In this embodiment, the force sensor 6 detects a front-rear load (x axis), a load in the front-rear direction (x axis), a left-right load (y axis), and a moment about the vertical axis (z axis) applied to the handle 5. The force sensor 6 has a main body and an input unit provided on the main body. The main body is coupled to the handle holder 35.

[0037] The handle 5 has horizontal sections 5A extending to the left and right, and a pair of vertical sections 5B extending forward from both the left and right ends of the horizontal sections 5A. The central part of the horizontal section 5A in the left-right direction is connected to the input section of the force sensor 6.

[0038] As shown in Figure 2, when the user applies an external force fh and moment mhz to the position rh of the handle 5, the force sensor 6 detects a detected force fs and a detected moment msz at the sensor position rs. The detected force fs includes a longitudinal load fs1, which is the longitudinal component, and a lateral load fs2, which is the lateral component.

[0039] The control unit 7 is an electronic control unit (ECU) that includes a processor such as a CPU, non-volatile memory (ROM), and volatile memory (RAM). The control unit 7 controls the drive unit 4 by executing arithmetic processing in accordance with a program stored in the non-volatile memory using the processor. The control unit 7 may be configured as a single piece of hardware, or as a unit consisting of multiple pieces of hardware. Furthermore, at least a portion of each functional part of the control unit 7 may be implemented by hardware such as an LSI, ASIC, or FPGA, or by a combination of software and hardware.

[0040] As shown in Figure 5, the control device 7 is connected to the force sensor 6 and the drive unit 4. The force sensor 6 outputs a detection signal to the control device 7. The control device 7 outputs a control signal to the drive unit 4.

[0041] The control device 7 controls the drive unit 4 based on signals from the force sensor 6. The force sensor 6 is interposed between the vehicle body 2 and the handle 5. The force sensor 6 detects the magnitude and direction of the operating force (load) applied by the user to the handle 5. The control device 7 determines the target longitudinal speed vt1, target lateral speed vt2, and target angular velocity ωt of the trolley 1 based on signals from the force sensor 6, and then determines the control amount of each electric motor 25 of the drive unit 4 based on the target longitudinal speed vt1, target lateral speed vt2, and target angular velocity ωt.

[0042] The control device 7 controls the drive unit 4 based on the flowchart shown in Figure 6. First, the control device 7 controls the detected force f detected by the force sensor 6 based on the signal from the force sensor 6. s And the detection moment msz is obtained (S1). Detection force f s This includes the front-to-rear load fs1 and the left-to-right load fs2.

[0043] Next, the control device 7 sets the target longitudinal speed vt1 of the vehicle body 2 based on the longitudinal load fs1, the target lateral speed vt2 of the vehicle body 2 based on the lateral load fs2, and the target angular velocity ωt of the vehicle body 2 around the vertical axis based on the moment msz around the vertical axis (S2).

[0044] When the longitudinal load fs1 is directed forward, the control device 7 sets the target longitudinal speed vt1 to be directed forward. In this embodiment, when the target longitudinal speed vt1 is directed forward, that is, when the trolley 1 is moving forward, the target longitudinal speed vt1 is set to be positive. Conversely, when the target longitudinal speed vt1 is directed backward, that is, when the trolley 1 is moving backward, the target longitudinal speed vt1 is set to be negative.

[0045] The target longitudinal velocity vt may be set, for example, by multiplying the longitudinal load fs1 by a predetermined coefficient k1. Similarly, the target lateral velocity vt2 may be set, for example, by multiplying the lateral load fs2 by a predetermined coefficient k2. Furthermore, the target angular velocity ωt may be set, for example, by multiplying the moment msz about the vertical axis by a predetermined coefficient k3. The target angular velocity ωt is set with respect to a reference point rc. The reference point rc may be set to a position that coincides with the center of gravity G of the trolley 1 in a plan view. In this embodiment, the reference point rc is located at the midpoint of the line segment connecting a pair of omnidirectional wheels 3. Note that the methods for setting the target longitudinal velocity vt1, target lateral velocity vt2, and target angular velocity ωt are not limited to these.

[0046] However, for the sake of simplicity, we will assume that the lateral load fs2 applied by the operator moving the trolley 1 is normally sufficiently small compared to the front-to-back load fs1, or that the coefficient k2 is sufficiently small compared to the coefficients k1 and k3.

[0047] Next, the control device 7 calculates the thrust force F(i) that the left and right omnidirectional wheels 3 should output in order to output the target longitudinal velocity vt1 and target angular velocity ωt, respectively (S3). However, i in the thrust force F(i) represents an argument (index) determined for each omnidirectional wheel 3, for example, i may be set to 1 for the left omnidirectional wheel 3 and 2 for the right omnidirectional wheel 3.

[0048] Next, the control device 7 uses the thrust force F(i) to calculate the upper limit τ(i) defined for each of the omnidirectional wheels 3. The upper limit τ(i) is expressed by the following equation (4).

[0049]

number

[0050] In equation (4), L1 represents the distance in the longitudinal direction of the vehicle from the center of gravity G to the left and right all-directional wheels 3, and L2 represents the distance in the width direction (left-right direction of the vehicle) from the center of gravity G to the left and right all-directional wheels 3. max This indicates the maximum static friction force of the left and right all-directional wheels 3 against the floor surface.

[0051] Next, the control device 7 extracts the minimum value of i in the upper limit value τ(i) and sets a predetermined value less than or equal to that minimum value as the threshold Th. In this embodiment, since there are two omnidirectional wheels 3, the control device 7 sets the threshold Th so as to satisfy the following equation (5) (S4).

[0052]

number

[0053] In equation (5), min(τ(1),τ(2)) represents the minimum values ​​of τ(1) and τ(2). The control device 7 may set the threshold Th to the minimum value of the upper limit τ(i) as shown in equation (5), or it may set the threshold Th to a value obtained by multiplying the minimum value of the upper limit τ(i) by a predetermined positive constant less than 1.

[0054] Once the threshold Th has been calculated, the control device 7 calculates the product of the target longitudinal velocity vt1 and the target angular velocity ωt and determines whether it is less than or equal to the threshold Th, that is, whether it satisfies equation (6) (S5).

[0055]

number

[0056] When the product of the target longitudinal speed vt1 and the target angular speed ωt is less than or equal to Th (Yes in S5), the control device 7 sets the target rotational speed rt for each of the electric motors 25 based on the target longitudinal speed vt1, the target lateral speed vt2, and the target angular speed ωt (S6).

[0057] Once the target rotational speed rt for each of the electric motors 25 has been set, the control device 7 controls the current supplied to each electric motor 25 so that the rotational speed of each electric motor 25 reaches the target rotational speed, thereby controlling each electric motor 25 (S7).

[0058] When the product of the target longitudinal velocity vt1 and the target angular velocity ωt is not less than or equal to the threshold Th, that is, when the calculated product of the target longitudinal velocity vt1 and the target angular velocity ωt is greater than the threshold Th (No in S5), the control device 7 performs a correction process to correct the target longitudinal velocity vt1 so that the product of the target angular velocity ωt is less than or equal to the threshold Th (S8).

[0059] In this embodiment, during the correction process, the control device 7 obtains a correction value vt1' that satisfies the following equation (7), and corrects the target longitudinal speed vt1 by setting this correction value vt1' as the target longitudinal speed vt1.

[0060]

number

[0061] The control device 7 may set the correction value vt1' to the value obtained by dividing the threshold Th by the target angular velocity ωt (i.e., the value on the right side of equation (7)), or it may set the correction value vt1' to the value on the right side of equation (7) multiplied by a predetermined positive constant less than 1.

[0062] Once the correction process is complete (S8), the control device 7 calculates the thrust force F(i) for each of the wheels 3 in all directions using the corrected target longitudinal velocity vt1 and target angular velocity ωt (S3). Then, the control device 7 calculates a threshold Th using equations (4) and (5) (S4) and determines whether the product of the corrected target longitudinal velocity vt1 and the target angular velocity ωt is less than or equal to the threshold Th (S5). If the product of the corrected target longitudinal velocity vt1 and the target angular velocity ωt is less than or equal to the threshold Th, the control device 7 sets the target rotational speed rt for each of the electric motors 25 (S6) and controls the electric motors 25 (S7). If the product of the corrected target longitudinal velocity vt1 and the target angular velocity ωt is greater than the threshold Th, the correction process is performed again (S8).

[0063] Next, we will explain the effects of the trolley 1 configured in this way.

[0064] If the lateral load fs2 applied by the worker moving the trolley 1 is sufficiently smaller than the longitudinal load fs1 (or if the coefficient k2 is sufficiently smaller than the coefficients k1 and k3), the trolley 1 will rotate while undergoing circular motion at an angular velocity of the target angular velocity ωt. At that time, the centrifugal force F acting on the trolley 1 is expressed as F = m × vt1 × ωt.

[0065] As shown in Figure 7, the centrifugal force F acting on the trolley 1 is distributed to each of the omnidirectional wheels 3, and each of the omnidirectional wheels 3 is subjected to a load of F / 2 directed outward in the direction of rotation. In addition, to prevent rotation of the trolley 1 around its center of gravity G due to this load, a couple f is generated on each of the omnidirectional wheels 3. This couple f acts such that the sum of the resultant force f and F / 2 is directed in the direction of the center of gravity G of the trolley 1.

[0066] Given the condition that the sum of the resultant forces with F / 2 acts in the direction of the center of gravity G of the trolley 1, the couple f satisfies equation (8) below.

[0067]

number

[0068] For the omnidirectional wheels 3 located closer to the pivot center, the couple f acts forward regardless of whether the bogie 1 is moving forward or backward (see Figure 7). On the other hand, for the omnidirectional wheels 3 located further away from the pivot center, the couple f acts backward regardless of whether the bogie 1 is moving forward or backward (see also Figure 11).

[0069] A couple of forces f and a thrusting force F(i) act on the omnidirectional wheel 3 in the direction of rotation. Therefore, the sum of the couple of forces f and the thrusting force F(i) is the maximum static friction force F. max When the following conditions are met, i.e., when equation (9) is satisfied, the slip in the turning direction of each of the omnidirectional wheels 3 can be reduced.

[0070]

number

[0071] By solving equations (8) and (9) simultaneously, we obtain the following equation (10) relating to vt1 × ωt: F = m × vt1 × ωt.

[0072]

number

[0073] In other words, when each of the omnidirectional wheels 3 satisfies equation (10), each of the omnidirectional wheels 3 becomes less likely to slip in the turning direction. Therefore, a trolley 1 capable of performing appropriate turning movements can be provided.

[0074] Furthermore, the threshold Th in equation (5) corresponds to the minimum value on the right-hand side of equation (10). Therefore, by using equations (4) and (5), it is possible to appropriately and simply set the threshold Th, which indicates the upper limit of the product of the target longitudinal speed and the target angular speed to prevent slippage of the omnidirectional wheel 3 in the turning direction.

[0075] In this embodiment, when the product of the target longitudinal speed vt1 and the target angular velocity ωt is less than or equal to the threshold Th (Yes in S5), the control device 7 controls the omnidirectional wheels 3 so that the longitudinal speed becomes the target longitudinal speed vt1 and the angular velocity becomes the target angular velocity ωt. As shown in equation (5), the threshold Th is set to be less than or equal to the minimum value of equation (10), so that the product of the target longitudinal speed vt1 and the target angular velocity ωt satisfies equation (10). This makes it less likely for the omnidirectional wheels 3 to slip.

[0076] Furthermore, when the product of the target longitudinal velocity vt1 and the target angular velocity ωt is greater than the threshold Th (No in S3), the control device 7 corrects the target longitudinal velocity vt1 until its product with the target angular velocity ωt is less than or equal to the threshold Th (S8). As a result, the output product of the longitudinal velocity and angular velocity satisfies equation (7), making it less likely for the all-directional wheels 3 to slip.

[0077] Furthermore, during the correction process, the control device 7 can easily obtain the correction value vt1' by calculating the right-hand side of equation (7). Therefore, the control device 7 can easily correct the target longitudinal speed vt1.

[0078] <<Second Embodiment>> In the second embodiment, the correction process performed by the control device 7 when the product of the target longitudinal speed vt1 and the target angular speed ωt is greater than the threshold Th (No in S6) differs from that of the first embodiment, but the other configurations are the same as in the first embodiment, so the other configurations will not be described.

[0079] As shown in Figure 8, in the second embodiment, when the product of the target longitudinal velocity vt1 and the target angular velocity ωt is greater than the threshold Th (No in S5), the control device 7 performs a correction process to correct the target angular velocity ωt so that the product of the target longitudinal velocity vt1 and the target angular velocity ωt is less than or equal to the threshold Th (S18).

[0080] In this embodiment, during the correction process, the control device 7 obtains a correction value ωt' that satisfies the following equation (11), and corrects the target angular velocity ωt by setting this correction value ωt' as the target angular velocity ωt.

[0081]

number

[0082] The control device 7 may set the correction value ωt' to the value obtained by dividing the threshold Th by the target angular velocity ωt (i.e., the value on the right side of equation (11)), or it may set the correction value ωt' to the value on the right side of equation (11) multiplied by a predetermined positive constant less than 1.

[0083] Once the correction process is complete (S18), the control device 7 calculates the thrust force F(i) for each of the wheels 3 in all directions using the target longitudinal velocity vt1 and the corrected target angular velocity ωt (S3). Then, the control device 7 calculates a threshold Th using equations (4) and (5) (S4) and determines whether the product of the target longitudinal velocity vt1 and the corrected target angular velocity ωt is less than or equal to the threshold Th (S5). If the product of the target longitudinal velocity vt1 and the corrected target angular velocity ωt is less than or equal to the threshold Th, the control device 7 sets the target rotational speed rt for each of the electric motors 25 (S6) and controls the electric motors 25 (S7). If the product of the target longitudinal velocity vt1 and the corrected target angular velocity ωt is greater than the threshold Th, the correction process is performed again (S18).

[0084] Next, the effects of the trolley 1 configured in this way will be explained. When the product of the target longitudinal speed vt1 and the target angular velocity ωt is greater than the threshold Th (No in S5), the control device 7 corrects the target angular velocity ωt until the product of the target longitudinal speed vt1 and ωt is less than or equal to the threshold Th (S18). As a result, the product of the output longitudinal speed and angular velocity satisfies equation (10), making it less likely for the all-directional wheels 3 of the trolley 1 to slip. Thus, a trolley capable of performing appropriate turning movements can be provided.

[0085] Furthermore, during the correction process, the control device 7 can easily obtain the correction value ωt' by calculating the right-hand side of equation (11). Therefore, the control device 7 can easily correct the target angular velocity ωt.

[0086] <<Third Embodiment>> In the second embodiment, the trolley 1 differs in the correction process performed by the control device 7 when the product of the target longitudinal speed vt1 and the target angular speed ωt is greater than the threshold Th (No in S5). Since the other configurations are the same as in the first embodiment, the other configurations will not be explained.

[0087] As shown in Figure 9, in the second embodiment, when the product of the target longitudinal velocity vt1 and the target angular velocity ωt is greater than the threshold Th (No in S5), the control device 7 performs a correction process to correct the target angular velocity ωt and the target longitudinal velocity vt1, respectively, so that the product of the target angular velocity ωt and the target longitudinal velocity vt1 is less than or equal to the threshold Th (S28).

[0088] In this embodiment, the control device 7 obtains a longitudinal velocity correction value vt1' and an angular velocity correction value ωt' that satisfy the following equations (12) and (13) during the correction process. Subsequently, the control device 7 corrects the target longitudinal velocity vt1 by replacing the target longitudinal velocity vt1 with the longitudinal velocity correction value vt1', and corrects the target angular velocity ωt by replacing the target angular velocity ωt with the angular velocity correction value ωt'.

[0089]

number

[0090] The control device 7 may set the longitudinal speed correction value vt1' to the value on the right side of equation (12), or to the value obtained by multiplying the value on the right side of equation (12) by a predetermined positive constant less than 1. The control device 7 may set the angular velocity correction value ωt' to the value on the right side of equation (13), or to the value obtained by multiplying the value on the right side of equation (13) by a predetermined positive constant less than 1.

[0091] Once the correction process is complete (S28), the control device 7 calculates the thrust force F(i) for each of the wheels 3 in all directions using the corrected target longitudinal velocity vt1 and the corrected target angular velocity ωt (S3). Then, the control device 7 calculates the threshold Th using equations (4) and (5) (S4) and determines whether the product of the corrected target longitudinal velocity vt1 and the corrected target angular velocity ωt is less than or equal to the threshold Th (S5). If the product of the corrected target longitudinal velocity vt1 and the corrected target angular velocity ωt is less than or equal to the threshold Th, the control device 7 sets the target rotational speed rt for each of the electric motors 25 (S6) and controls the electric motors 25 (S7). If the product of the corrected target longitudinal velocity vt1 and the corrected target angular velocity ωt is greater than the threshold Th, the correction process is performed again (S28).

[0092] Next, the effects of the trolley 1 configured in this way will be explained. When the product of the target longitudinal speed vt1 and the target angular velocity ωt is greater than the threshold Th (No in S5), the control device 7 corrects the target longitudinal speed vt1 and the target angular velocity ωt until the product of the target longitudinal speed vt1 and the target angular velocity ωt is less than or equal to the threshold Th (S28). As a result, the output product of the longitudinal speed and angular velocity satisfies equation (10), making it less likely for the all-directional wheels 3 of the trolley 1 to slip. Thus, a trolley capable of performing appropriate turning movements can be provided.

[0093] Furthermore, in the correction process, the control device 7 can easily obtain the longitudinal velocity correction value vt1' and the angular velocity correction value ωt' by calculating the right-hand side of equations (12) and (13). Therefore, the control device 7 can easily correct the target longitudinal velocity vt1 and the target angular velocity ωt.

[0094] <<Variation>> As a modification of the first to third embodiments described above, the control device 7 may be configured to perform correction processing only when the trolley 1 is moving backward, that is, only when the target longitudinal speed is negative.

[0095] Figure 10 illustrates a flowchart of a modified version of the first embodiment. The control device 7 corrects the target longitudinal speed vt1 only when the target longitudinal speed is negative (S38).

[0096] Next, we will explain the effects of this modified configuration.

[0097] The omnidirectional wheels 3 located on the side furthest from the center of rotation are generally required to output a greater thrust F(i) than those on the side closer to the center of rotation.

[0098] On the other hand, in the omnidirectional wheel 3 located closer to the pivot center, the couple f always acts forward, while in the omnidirectional wheel 3 located further from the pivot center, the couple f always acts backward.

[0099] When the trolley 1 moves forward, as shown in Figure 7, each of the omnidirectional wheels 3 outputs a thrust force F(i) in the forward direction. Therefore, when the trolley 1 moves forward, the direction of the thrust force F(i) and the couple f are opposite for the omnidirectional wheels 3 located on the side furthest from the center of rotation.

[0100] When the bogie 1 moves backward, as shown in Figure 11, each of the omnidirectional wheels 3 outputs a thrust force F(i) towards the rear. Therefore, when the bogie 1 moves backward, the direction of the thrust force F(i) and the couple f are the same (rearward) for the omnidirectional wheels 3 located on the side farther from the center of rotation, making slip more likely to occur in the omnidirectional wheels 3 located on the side farther from the center of rotation.

[0101] By performing a correction process only when the target forward / backward speed is negative, that is, when the bogie 1 is moving backward, the slip of the all-direction wheels 3 can be reduced, especially when the all-direction wheels 3 are prone to slipping during backward movement. Furthermore, the processing that the control device 7 needs to perform is reduced, thus simplifying the processing that the control device 7 performs to control the bogie 1.

[0102] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments and can be broadly modified and implemented.

[0103] In other embodiments, instead of the force sensor 6, sensors capable of detecting forward / backward loads, left / right loads, and moments around the vertical axis applied to the handle 5 may be used. For example, the sensors may be configured by combining a number of independent load sensors.

[0104] In the above embodiment, the trolley 1 was equipped with omnidirectional wheels 3, but the embodiment is not limited to this. Any embodiment in which the trolley 1 is equipped with a pair of left and right wheels that can be driven based on a target longitudinal speed and a target angular speed, instead of the omnidirectional wheels 3, is acceptable. [Explanation of symbols]

[0105] 1: Dolly 2: Vehicle body 3: All-directional wheel 3 (an example of a wheel) 4: Drive Unit 5: Handle 6: Force sensor (an example of a sensor) 7: Control device

Claims

1. It is a trolley, The car body and, A pair of left and right wheels provided on the vehicle body, Each of the aforementioned wheels is driven by a left and right drive unit that drives each of the aforementioned wheels, A handle provided on the vehicle body that accepts user input, A sensor that detects the forward and backward load applied to the handle, and the moment around the vertical axis, The drive unit has a control device, The control device is Based on the aforementioned front and rear loads, the target front and rear speed of the vehicle body is set. Based on the moment around the vertical axis, the target angular velocity of the vehicle body around the vertical axis is set. A trolley that controls the drive unit based on the corrected target longitudinal speed and target angular velocity, after performing a correction process on the target longitudinal speed so that the product of the target longitudinal speed and target angular velocity is less than or equal to the threshold when the product of the target longitudinal speed and target angular velocity is greater than a predetermined threshold.

2. The trolley according to claim 1, wherein the control device corrects the target forward and backward speed in the correction process to a value less than or equal to the value obtained by dividing the threshold by the target angular velocity.

3. It is a trolley, The car body and, A pair of left and right wheels provided on the vehicle body, Each of the aforementioned wheels is driven by a left and right drive unit that drives each of the aforementioned wheels, A handle provided on the vehicle body that accepts user input, A sensor that detects the forward and backward load applied to the handle, and the moment around the vertical axis, The drive unit has a control device, The control device is Based on the aforementioned front and rear loads, the target front and rear speed of the vehicle body is set. Based on the moment around the vertical axis, the target angular velocity of the vehicle body around the vertical axis is set. A trolley that controls the drive unit based on the corrected target angular velocity and the target forward / backward velocity, after performing a correction process on the target angular velocity so that the product of the target forward / backward velocity and the target angular velocity is less than or equal to the threshold when the product of the target forward / backward velocity and the target angular velocity is greater than a predetermined threshold.

4. The trolley according to claim 3, wherein the control device corrects the target angular velocity to a value less than or equal to the value obtained by dividing the threshold by the target forward and backward velocity in the correction process.

5. It is a trolley, The car body and, A pair of left and right wheels provided on the vehicle body, Each of the aforementioned wheels is driven by a left and right drive unit that drives each of the aforementioned wheels, A handle provided on the vehicle body that accepts user input, A sensor that detects the forward and backward load applied to the handle, and the moment around the vertical axis, The drive unit has a control device, The control device is Based on the aforementioned front and rear loads, the target front and rear speed of the vehicle body is set. Based on the moment around the vertical axis, the target angular velocity of the vehicle body around the vertical axis is set. A trolley that controls the drive unit based on the corrected target angular velocity and the corrected target forward / backward velocity, after performing a correction process on the target angular velocity and the target angular velocity so that the product of the target forward / backward velocity and the target angular velocity is less than or equal to the threshold when the product of the target forward / backward velocity and the target angular velocity is greater than a predetermined threshold.

6. The trolley according to claim 5, wherein the control device corrects the target longitudinal speed by replacing it with a longitudinal speed correction value vt1' that satisfies the following equation (1) and the target angular speed with an angular speed correction value ωt' that satisfies the following equation (2), when the threshold value is Th, the target longitudinal speed is vt1 and the target angular speed is ωt. [Math 1]

7. Let m be the mass of the bogie, and L be the distance from the center of gravity to the wheels in the longitudinal direction of the vehicle. １ The distance in the vehicle width direction from the center of gravity to the wheel is L. ２ , the maximum static friction force F of the wheel with respect to the floor surface ｍａｘ The trolley according to any one of claims 1 to 6, wherein, when the thrust force F(i) of each of the wheels relative to the floor surface is (where i is an argument indicating the wheel number), the threshold Th is set to be less than or equal to the minimum value of the upper limit τ(i) represented by equation (3). [Math 2]

8. The control device performs the correction process only when the trolley is moving backward, according to any one of claims 1 to 7.

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