cart

Abstract

A cart includes a control unit configured to: if a provisional target fore-aft speed is equal to or higher than a fore-aft speed upper limit, or if a provisional target lateral speed is equal to or higher than a lateral speed upper limit, multiply the provisional target fore-aft speed by a correction coefficient to thereby set a target fore-aft speed, and multiply the provisional target lateral speed by the correction coefficient to thereby set a target lateral speed; and if the provisional target fore-aft speed is less than the fore-aft speed upper limit and the provisional target lateral speed is less than the lateral speed upper limit, set the provisional target fore-aft speed to the target fore-aft speed, and set the provisional target lateral speed to the target lateral speed.

Description

Technical Field

[0001] The present invention relates to a cart. Background Art

[0002] JP2004-114800A discloses a power-assisted stroller including a handle that detects a user's operating force, and a power-assist control device that drives a drive wheel based on the operating force input to the handle to drive and steer the stroller. The stroller detects a turning state and decelerates or stops when turning, thereby suppressing unintended acceleration caused by incorrect operation during turning.

[0003] The cart according to JP2004-114800A detects a turning state and performs deceleration control when the cart is in a turning state. Therefore, even if excessive operations are input when the cart is moving straight or horizontally, the speed (velocity) is not limited. Summary of the Invention

[0004] In view of the above background, an object of the present invention is to provide a cart capable of limiting speed in response to excessive operation.

[0005] To achieve such an object, one aspect of the present invention provides a cart 1, comprising: a body 2; at least one omnidirectional wheel 3, the at least one omnidirectional wheel being provided at the body and being configured to move the body in all directions along a floor; a drive unit 4, the drive unit being configured to drive each omnidirectional wheel; a handle 5, the handle being provided at the body and being configured to receive a user's operation; a load sensor 6, the load sensor being configured to detect a front-rear load and a lateral load applied to the handle; and a control unit 7, the control unit being configured to control the drive unit based on the front-rear load and the lateral load detected by the load sensor, wherein the control unit is configured to: set a tentative target front-rear speed of the body based on the front-rear load, and set a tentative target front-rear speed of the body based on the lateral load The method further comprises setting a provisional target lateral speed of the vehicle body based on a load, multiplying the provisional target front-rear speed by a correction coefficient to set a target front-rear speed when the provisional target front-rear speed is equal to or higher than a front-rear speed upper limit or when the provisional target lateral speed is equal to or higher than a lateral speed upper limit, and multiplying the provisional target lateral speed by the correction coefficient to set a target lateral speed, the correction coefficient being set to be greater than 0 and equal to or less than 1, setting the provisional target front-rear speed to the target front-rear speed when the provisional target front-rear speed is less than the front-rear speed upper limit and the provisional target lateral speed is less than the lateral speed upper limit, and setting the provisional target lateral speed to the target lateral speed, and controlling the drive unit based on the target front-rear speed and the target lateral speed.

[0006] According to this aspect, when the provisional target longitudinal speed is equal to or higher than the longitudinal speed upper limit, or when the provisional target lateral speed is equal to or higher than the lateral speed upper limit, a correction coefficient is set to limit the target longitudinal speed and the target lateral speed. Thus, a cart can be provided that can limit its speed in response to excessive operation.

[0007] In the above aspect, preferably, the smaller of a first value and a second value is set as the correction coefficient, the first value is calculated by dividing the longitudinal speed upper limit by the provisional target longitudinal speed, and the second value is calculated by dividing the lateral speed upper limit by the provisional target lateral speed.

[0008] According to this aspect, the target longitudinal speed is set to be equal to or less than the longitudinal speed upper limit, and the target lateral speed is set to be equal to or less than the lateral speed upper limit. Furthermore, the ratio of the target longitudinal speed to the target lateral speed becomes equal to the ratio of the provisional target longitudinal speed to the provisional target lateral speed, thereby maintaining the direction of travel of the cart.

[0009] In the above aspect, preferably, the at least one omnidirectional wheel includes a pair of omnidirectional wheels arranged at intervals in the lateral direction, the load sensor is configured to detect a torque around a vertical axis in addition to the front and rear loads and the lateral load, and the control unit is configured to set a target angular velocity of the vehicle body based on the torque, and control the drive unit based on the target front and rear velocity, the target lateral velocity and the target angular velocity.

[0010] According to this aspect, the target angular velocity is not limited regardless of the user's operating force. Therefore, the cart can be rotated according to the user's intention.

[0011] In the above aspect, preferably, the control unit sets the target angular velocity independently of the correction coefficient.

[0012] According to this aspect, the target angular velocity is not limited regardless of the user's operating force. Therefore, the cart can be rotated according to the user's intention.

[0013] In the above aspect, preferably, the drive unit includes a plurality of electric motors 25, and the control unit is configured to: set a first rotational speed of each electric motor based on the target front-rear speed, set a second rotational speed of each electric motor based on the target lateral speed, set a third rotational speed of each electric motor based on the target angular velocity, and set a provisional target rotational speed of each electric motor based on the first rotational speed, the second rotational speed, and the third rotational speed; when the provisional target rotational speed of at least one of the plurality of electric motors is higher than the maximum rotational speed, set the target rotational speed of each electric motor based on the product of a motor rotational speed correction coefficient and the first rotational speed, the product of the motor rotational speed correction coefficient and the second rotational speed, and the third rotational speed, the motor rotational speed correction coefficient being set to be greater than 0 and equal to or less than 1; and when the provisional target rotational speeds of all electric motors are equal to or less than the maximum rotational speed, set the provisional target rotational speed to the target rotational speed.

[0014] According to this aspect, even if the target rotation speed of each electric motor falls below the maximum rotation speed, the third rotation speed for achieving the target angular velocity is not limited. Therefore, the cart can be turned according to the user's intention.

[0015] In the above aspect, preferably, the motor speed correction coefficient is set based on the following equation 1, where "kr" represents the motor speed correction coefficient, "rm" represents the maximum speed, "r1" represents the first speed, "r2" represents the second speed, and "r3" represents the third speed.

[0016] [Equation 1] kr = (rm - |r3|) / (|r1| + |r2|)

[0017] According to this aspect, when the provisional target rotation speed is higher than the maximum rotation speed, the target rotation speed is set to the maximum rotation speed.

[0018] In the above aspect, preferably, a reference point of the target angular velocity is arranged at a midpoint of a line segment connecting the pair of omnidirectional wheels.

[0019] According to this aspect, the cart can be efficiently turned.

[0020] In the above aspects, preferably, each omnidirectional wheel includes: a pair of drive discs 18, which are rotatably supported by the vehicle body and coaxially arranged to face each other; a plurality of drive rollers 18B, which are arranged at intervals in the circumferential direction on the outer peripheral portion of each drive disc, each drive roller being supported to rotate around an axis inclined to the circumferential direction of the drive disc; and a main wheel 19 formed in an annular shape, which is arranged between the pair of drive discs, contacts the drive rollers, and is configured to rotate around a central axis and an annular axis, the plurality of electric motors include four electric motors 25 corresponding to the corresponding drive discs and configured to rotate the corresponding drive discs, and the control unit is configured to set a target rotational speed of each electric motor based on the target front-rear speed, the target lateral speed and the target angular speed.

[0021] According to this aspect, the cart can move straight, translate, and rotate.

[0022] Another aspect of the present invention provides a cart 1 including: a vehicle body 2; at least one omnidirectional wheel 3 provided at the vehicle body and configured to move the vehicle body in all directions along a floor; a drive unit 4 configured to drive each omnidirectional wheel; a handle 5 provided at the vehicle body and configured to receive a user's operation; a load sensor 6 configured to detect a load applied to the handle; and a control unit 7 configured to control the drive unit based on the load detected by the load sensor, wherein the control unit is configured to: set a tentative target velocity vector of the vehicle body based on the load; if the magnitude of the tentative target velocity vector is equal to or greater than an upper limit, multiply the tentative target velocity vector by a correction coefficient to thereby set a target velocity vector, the correction coefficient being set to be greater than 0 and equal to or less than 1; if the magnitude of the tentative target velocity vector is less than the upper limit, set the tentative target velocity vector as the target velocity vector; and control the drive unit based on the target velocity vector.

[0023] According to this aspect, when the magnitude of the provisional target speed vector is equal to or greater than the upper limit, the correction coefficient is set and the target speed vector is limited. Therefore, a cart capable of limiting speed in response to excessive operation can be provided.

[0024] In the above aspect, preferably, a value calculated by dividing the upper limit by the magnitude of the tentative target speed vector is set as the correction coefficient.

[0025] According to this aspect, the target velocity vector is set to be equal to or less than the upper limit. In addition, the direction of the target velocity vector becomes the same as the direction of the tentative target velocity vector, so that the traveling direction of the cart can be maintained.

[0026] Therefore, according to the above aspects, it is possible to provide a cart capable of limiting speed in response to excessive operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a perspective view of a cart according to one embodiment;

[0028] Figure 2 It is a plan view of the cart;

[0029] Figure 3 is a cross-sectional view of the omnidirectional wheel;

[0030] Figure 4 It is a side view of the main wheel;

[0031] Figure 5 is a block diagram showing a control unit of the cart;

[0032] Figure 6 is a flowchart showing a control process performed by the control unit; and

[0033] Figure 7 It is a plan view showing the orientation of the cart. DETAILED DESCRIPTION

[0034] Hereinafter, an embodiment of a cart according to the present invention will be described with reference to the accompanying drawings. Hereinafter, each direction is defined based on the cart.

[0035] like Figure 1 As shown, the cart (vehicle) 1 includes: a body 2; at least one omnidirectional wheel 3, which is provided at the body 2 and is configured to move the body 2 in all directions along the floor; a drive unit 4, which is configured to drive each omnidirectional wheel 3; a handle 5, which is provided at the body 2 and is configured to accept a user's operation; a load sensor 6, which is configured to detect a load applied to the handle 5; and a control unit 7, which is configured to control the drive unit 4 based on the load detected by the load sensor 6.

[0036] The vehicle body 2 extends in the front-to-back direction. The rear portion 2A of the vehicle body 2 extends further upward than the front portion 2B. The front portion 2B of the vehicle body 2 is provided with a support base 11 for supporting other devices. Devices supported by the support base 11 include, for example, inspection equipment such as an X-ray scanner. These devices can be fastened to the support base 11. The control unit 7, battery, and various sensors can be housed within the rear portion 2A of the vehicle body 2.

[0037] In this embodiment, a pair of omnidirectional wheels 3 are provided at the lower portion of the rear portion 2A of the vehicle body 2. In addition, a left caster 13 and a right caster 13 are supported by the lower portion of the front portion 2B of the vehicle body 2 via a suspension. The suspension includes an arm 14, a spring 15, and a shock absorber 16. The arm 14 is arranged below the vehicle body 2 and extends in the lateral direction. The spring 15 and the shock absorber 16 are arranged between the vehicle body 2 and the arm 14. Each caster 13 is arranged below the lateral end of the arm 14. Each caster 13 includes a fork 13A connected to the arm 14 to rotate around an axis extending in the vertical direction, and a wheel 13B supported by the fork 13A to rotate around an axis extending in the horizontal direction. The fork 13A is free to rotate relative to the arm 14, and the wheel 13B is free to rotate relative to the fork 13A.

[0038] like Figure 2 As shown, a pair of omnidirectional wheels 3 are arranged at intervals in the lateral direction. In this embodiment, a pair of omnidirectional wheels 3 are arranged on the lower left and lower right sides of the rear portion 2A of the vehicle body 2. Figure 3 As shown, each omnidirectional wheel 3 includes a frame 17 , a pair of drive discs 18 rotatably supported by the frame 17 , and an annular main wheel 19 disposed between the pair of drive discs 18 .

[0039] like Figure 1 and Figure 3 As shown, the frame 17 includes an upper frame 17A coupled to the lower portion of the vehicle body 2 and a pair of side frames 17B extending downward from the lateral ends of the upper frame 17A. A support shaft 21 extending in the lateral direction is provided between the lower ends of the pair of side frames 17B. The pair of drive plates 18 are rotatably supported by the support shaft 21. The pair of drive plates 18 are configured to rotate about the axis Y1 of the support shaft 21. The lateral position of each drive plate 18 is adjusted (fixed) relative to the support shaft 21. The drive plates 18 face each other at a certain interval in the lateral direction.

[0040] Drive discs 18 are arranged on either side of an annular main wheel 19 and are configured to apply friction to the main wheel 19, causing it to rotate about its central axis and an annular axis. Each drive disc 18 includes a disc-shaped base 18A rotatably supported by the frame 17 and a drive roller 18B rotatably supported by the outer periphery of the base 18A. The drive rollers 18B are tilted relative to each other and in contact with the main wheel 19. The base 18A is coaxially arranged with the support shaft 21.

[0041] Each drive disc 18 has an opposing surface. The opposing surface of one drive disc 18 faces away from the opposing surface of the other drive disc 18. A driven pulley 18C is provided on the opposing surface of each drive disc 18. The driven pulley 18C is provided coaxially with the drive disc 18. The drive unit 4 is provided at the lower portion of the vehicle body 2. The drive unit 4 includes a plurality of electric motors 25 corresponding to each drive disc 18. In the present embodiment, four electric motors 25 are provided to correspond to the four drive discs 18. A drive pulley 26 is provided on the output shaft of each electric motor 25. The drive pulley 26 and the driven pulley 18C corresponding to each other are connected by a belt 27. When each electric motor 25 rotates independently of each other, each drive disc 18 rotates independently of each other.

[0042] like Figure 4 As shown, the main wheel 19 has an annular shape and is arranged between the pair of drive discs 18 so as to be coaxial therewith. The main wheel 19 is in contact with the drive roller 18B and can rotate around the central axis and the annular axis. The main wheel 19 includes an annular core member 31 and a plurality of driven rollers 32 rotatably supported by the core member 31. The plurality of driven rollers 32 are arranged at equal intervals in the circumferential direction of the core member 31. Each driven roller 32 is supported by the core member 31 so as to rotate around the axis A1 (annular axis) of the annular core member 31. More specifically, each driven roller 32 can rotate around the tangent of the core member 31 at a corresponding position relative to the core member 31. When receiving an external force, each driven roller 32 rotates relative to the core member 31.

[0043] The main wheel 19 is arranged along the outer periphery of the pair of drive disks 18 and contacts the multiple drive rollers 18B of each drive disk 18. The drive rollers 18B of each drive disk 18 contact the inner periphery of the main wheel 19, thereby holding the main wheel 19 from both lateral sides. Furthermore, the drive rollers 18B of the left and right drive disks 18 contact the inner periphery of the main wheel 19, thereby regulating (suppressing) radial displacement of the drive disks 18 about the axis Y1. Therefore, the main wheel 19 is supported by the left and right drive disks 18, and the center axis of the main wheel 19 (core member 31) is arranged coaxially with the axis Y1 of the left and right drive disks 18. The multiple driven rollers 32 of the main wheel 19 contact the multiple drive rollers 18B of the left and right drive disks 18.

[0044] In each omnidirectional wheel 3, when the pair of drive discs 18 rotate at the same rotational speed and in the same direction, the main wheel 19 rotates along with the pair of drive discs 18. That is, the main wheel 19 rotates forward or backward about its own rotational axis, which aligns 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 member 31. In each omnidirectional wheel 3, when the rotational speeds of the pair of drive discs 18 differ, a component force is applied from the drive rollers 18B of the left and right drive discs 18 to the driven rollers 32 of the main wheel 19. This component force is a force in a direction perpendicular to the circumferential (tangential) force caused by the rotation of the pair of drive discs 18. Because the axis of each drive roller 18B is tilted relative to the circumferential direction of the drive rollers 18B (drive discs 18), a component force is generated due to the difference in rotational speed between the pair of drive discs 18. This component force causes the drive rollers 18B to rotate relative to the base 18A, and the driven rollers 32 to rotate relative to the core member 31. Therefore, the main wheel 19 generates a driving force in the lateral direction.

[0045] When the left and right omnidirectional wheels 3 rotate forward at the same speed, the cart 1 moves forward. When the left and right omnidirectional wheels 3 rotate backward at the same speed, the cart 1 moves backward. When a speed difference occurs between the forward and backward rotations of the left and right omnidirectional wheels 3, the cart 1 turns right or left. When the driven rollers 32 of the main wheels 19 of the left and right omnidirectional wheels 3 rotate, the cart 1 translates right or left.

[0046] like Figure 1 and Figure 2 As shown, a handle holder 35 protruding upward is provided at the upper portion of the rear portion 2A of the vehicle body 2. The handle 5 is supported by the handle holder 35 via a load sensor 6. The load sensor 6 can be composed of a three-axis load sensor configured to detect loads along two axes perpendicular to each other in a horizontal plane and moments around a vertical axis (z-axis). In the present embodiment, the load sensor 6 is configured to detect the front and rear loads, lateral loads, and moments around a vertical axis applied to the handle 5. The front and rear loads are loads in the front and rear directions (x-axis direction). The lateral loads are loads in the lateral direction (y-axis direction). The load sensor 6 includes a main body portion and an input portion provided in the main body portion. The main body portion is connected to the handle holder 35.

[0047] The handle 5 includes a lateral portion 5A extending in the lateral direction and a pair of front and rear portions 5B extending forward from lateral ends of the lateral portion 5A. A lateral center portion of the lateral portion 5A is coupled to an input portion of the load sensor 6.

[0048] like Figure 2As shown, when the user applies an external force fh and a moment mhz to the position rh of the handle 5, the load sensor 6 detects a detected force fs (detected load) and a detected moment msz at the sensor position rs. The detected force fs includes a front-to-back load fs1 as a component in the front-to-back direction and a lateral load fs2 as a component in the lateral direction.

[0049] The control unit 7 is composed of an electronic control unit (ECU) including a processor such as a CPU, a non-volatile memory such as a ROM, a volatile memory such as a RAM, and the like. The processor executes operation processing according to a program stored in the non-volatile memory, so that the control unit 7 controls the drive unit 4. The control unit 7 may be composed of a single piece of hardware or a unit including multiple pieces of hardware. In addition, the functions of the control unit 7 may be at least partially performed by hardware such as an LSI, an ASIC, and an FPGA, or may be performed by a combination of software and hardware.

[0050] like Figure 5 As shown, the control unit 7 is connected to the load sensor 6 and the drive unit 4. The load sensor 6 outputs a detection signal to the control unit 7. The control unit 7 outputs a control signal to the drive unit 4.

[0051] The control unit 7 controls the drive unit 4 based on detection signals from the load sensor 6. The load sensor 6 is interposed between the vehicle body 2 and the handle 5. The load sensor 6 detects the magnitude and direction of the operating force (load) applied by the user to the handle 5. The control unit 7 can determine the target longitudinal velocity vt1, target lateral velocity vt2, and target angular velocity ωt of the cart 1 based on the detection signals from the load sensor 6, and can also determine the control amount of each electric motor 25 of the drive unit 4 based on the target longitudinal velocity vt1, target lateral velocity vt2, and target angular velocity ωt.

[0052] The control unit 7 is based on Figure 6 The driving unit 4 is controlled according to the flowchart shown. First, the control unit 7 obtains the detection force fs (detected load) and the detection moment msz detected by the load sensor 6 based on the detection signal from the load sensor 6 (S1). The detection force fs includes the front-rear load fs1 and the lateral load fs2.

[0053] Subsequently, the control unit 7 sets a provisional target longitudinal speed vtp1 of the vehicle body 2 based on the longitudinal load fs1, and sets a provisional target lateral speed vtp2 of the vehicle body 2 based on the lateral load fs2 (S2). The provisional target longitudinal speed vtp1 can be set, for example, by multiplying the longitudinal load fs1 by a predetermined coefficient K1. Furthermore, the provisional target lateral speed vtp2 can be set, for example, by multiplying the lateral load fs2 by a predetermined coefficient K2. The method for setting the provisional target longitudinal speed vtp1 and the provisional target lateral speed vtp2 is not limited to this.

[0054] Subsequently, the control unit 7 determines whether the provisional target longitudinal speed vtp1 is equal to or higher than the longitudinal speed upper limit vu1 or whether the provisional target lateral speed vtp2 is equal to or higher than the lateral speed upper limit vu2 (S3). The longitudinal speed upper limit vu1 and the lateral speed upper limit vu2 are preset values.

[0055] If the provisional target fore-and-aft speed vtp1 is equal to or higher than the fore-and-aft speed upper limit vu1, or if the provisional target lateral speed vtp2 is equal to or higher than the lateral speed upper limit vu2 (YES in S3), the control unit 7 sets a correction coefficient kv to reduce the target speed (S4). The correction coefficient kv is set to a value greater than 0 and equal to or less than 1. The correction coefficient kv may be a preset value. Alternatively, the smaller of a first value and a second value may be set as the correction coefficient kv. The first value is calculated by dividing the fore-and-aft speed upper limit vu1 by the provisional target fore-and-aft speed vtp1. The second value is calculated by dividing the lateral speed upper limit vu2 by the provisional target lateral speed vtp2.

[0056] Following step S4 , the control unit 7 sets the target longitudinal speed vt1 by multiplying the provisional target longitudinal speed vtp1 by the correction coefficient kv, and sets the target lateral speed vt2 by multiplying the provisional target lateral speed vtp2 by the correction coefficient kv ( S5 ).

[0057] When the provisional target front-to-back speed vtp1 is less than the front-to-back speed upper limit vu1 and the provisional target lateral speed vtp2 is less than the lateral speed upper limit vu2 (the determination result of S3 is No), the control unit 7 sets the provisional target front-to-back speed vtp1 as the target front-to-back speed vt1 and sets the provisional target lateral speed vtp2 as the target lateral speed vt2 (S6).

[0058] After setting the target fore-aft velocity vt1 and target lateral velocity vt2 in step S5 or step S6, the control unit 7 sets the target angular velocity ωt for the cart 1 based on the detection torque msz and the detection force fs (S7). For example, the target angular velocity ωt can be set by multiplying a specified value by a specified coefficient k3. The specified value is obtained by adding the detection torque msz to the outer product of the relative position rs (sensor position) of the load sensor 6 relative to the reference point rc and the detection force fs ((rs - rc) × fs) + msz). The target angular velocity ωt is set around the reference point rc. The reference point rc can be set at a position that matches the center of gravity of the cart 1 when viewed from above. Furthermore, setting the reference point rc closer to the handle 5 reduces the couple required for lateral movement, thereby enabling lateral movement with less force. In this embodiment, the reference point rc is located at the midpoint of the line segment connecting the pair of omnidirectional wheels 3. The processing of step S7 can be performed after step S1 or S2.

[0059] The control unit 7 controls the drive unit 4 based on the target longitudinal velocity vt1, the target lateral velocity vt2, and the target angular velocity ωt (S8). The control unit 7 sets a target rotation speed rt for each electric motor 25 based on the target longitudinal velocity vt1, the target lateral velocity vt2, and the target angular velocity ωt. The control unit 7 then controls the current supplied to each electric motor 25 so that the rotation speed of each electric motor 25 reaches the target rotation speed.

[0060] An example of how the control unit 7 controls the drive unit 4 will be described below. First, the control unit 7 refers to a first map to set a first rotational speed r1 for each electric motor 25 based on the target fore-aft speed vt1. The first map defines the relationship between the target fore-aft speed vt1 and the rotational speed of each electric motor 25. Subsequently, the control unit 7 refers to a second map to set a second rotational speed r2 for each electric motor 25 based on the target lateral speed vt2. The second map defines the relationship between the target lateral speed vt2 and the rotational speed of each electric motor 25. Subsequently, the control unit 7 refers to a third map to set a third rotational speed r3 for each electric motor 25 based on the target angular speed ωt. The third map defines the relationship between the target angular speed ωt and the rotational speed of each electric motor 25. Subsequently, the control unit 7 adds the first rotational speed r1, the second rotational speed r2, and the third rotational speed r3 of each electric motor 25 to calculate a provisional target rotational speed rtp for each electric motor 25 (rtp = r1 + r2 + r3). When the provisional target speed rtp of at least one electric motor 25 is higher than the maximum speed rm, that is, when at least one provisional target speed rtp is higher than the maximum speed rm, the control unit 7 multiplies the motor speed correction coefficient kr by the first speed r1 and the second speed r2, thereby calculating the target speed rt (rt = kr × r1 + kr × r2 + r3). ​​The motor speed correction coefficient kr is set to be greater than 0 and equal to or less than 1. The maximum speed rm may be a preset value. The motor speed correction coefficient kr is determined based on the maximum speed rm, the first speed r1, the second speed r2, and the third speed r3. The motor speed correction coefficient kr may be set based on, for example, the following equation 1.

[0061] [Equation 1] kr = (rm - |r3|) / (|r1| + |r2|)

[0062] According to Equation 1, when the provisional target speed rtp is higher than the maximum speed rm, the target speed rt is set to the maximum speed rm. Furthermore, the motor speed correction coefficient kr may be a preset value. When no provisional target speed rtp of the electric motor 25 is higher than the maximum speed rm, that is, when all provisional target speeds rtp are equal to or lower than the maximum speed rm, the control unit 7 sets the provisional target speed rtp to the target speed rt. The control unit 7 then refers to the fourth map, thereby setting the current value It supplied to each electric motor 25 based on the target speed rt of each electric motor 25. The fourth map defines the relationship between the target speed rt and the current value It supplied to each electric motor 25.

[0063] According to the above embodiment, when the provisional target longitudinal speed vtp1 is equal to or higher than the longitudinal speed upper limit vu1 or the provisional target lateral speed vtp2 is equal to or higher than the lateral speed upper limit vu2, the correction coefficient kv is set to limit the target longitudinal speed vt1 and the target lateral speed vt2. Therefore, it is possible to provide a cart 1 capable of limiting its speed in response to excessive operation.

[0064] In addition, the provisional target fore-and-aft speed vtp1 and the provisional target lateral speed vtp2 are corrected by a common correction coefficient kv, and therefore, the ratio of the target fore-and-aft speed vt1 to the target lateral speed vt2 becomes the same as the ratio of the provisional target fore-and-aft speed vtp1 to the provisional target lateral speed vtp2. In addition, even if the provisional target rotation speed rtp of at least one electric motor 25 is higher than the maximum rotation speed rm, each provisional target rotation speed rtp of the electric motor 25 is corrected to a value equal to or lower than the maximum rotation speed rm, so that the ratio of the target fore-and-aft speed vt1 and the target lateral speed vt2 to the target angular speed ωt does not change. Therefore, even when the speed of the cart 1 is limited, the traveling direction of the cart 1 is maintained. In addition, regardless of the operating force of the user, the target angular speed ωt is not limited. Therefore, the cart 1 can be turned according to the user's intention. Therefore, as Figure 7 As shown, the direction of the cart 1 each time when the speed of the cart 1 is limited becomes equal to the direction of the cart 1 each time when the speed of the cart 1 is not limited.

[0065] The reference point rc of the target angular velocity ωt is arranged at the midpoint of the pair of omnidirectional wheels 3. Therefore, the cart 1 can be turned efficiently.

[0066] While specific embodiments of the present invention have been described above, the present invention is not limited to the aforementioned embodiments, and various modifications and variations are possible within the scope of the present invention. For example, the control unit 7 may set the provisional target velocity vector vtp of the vehicle body 2 based on the load detected by the load sensor 6. The control unit 7 may multiply the provisional target velocity vector vtp by a correction coefficient kv, which is set to be greater than 0 and equal to or less than 1, thereby setting the target velocity vector vt when the magnitude of the provisional target velocity vector vtp is equal to or greater than the upper limit vu. The provisional target velocity vector vtp may be set based on the provisional target fore-aft velocity vtp1 and the provisional target lateral velocity vtp2. The value obtained by dividing the upper limit vu by the magnitude of the provisional target velocity vector vtp may be set as the correction coefficient kv.

Claims

1. A cart, comprising: body; at least one omnidirectional wheel provided at the vehicle body and configured to move the vehicle body in all directions along a floor; a drive unit configured to drive each omnidirectional wheel; a handle provided on the vehicle body and configured to receive an operation from a user; a load sensor configured to detect a fore-aft load and a lateral load applied to the handle; and a control unit configured to control the drive unit based on the front-rear load and the lateral load detected by the load sensor, Wherein, the control unit is configured as follows: A provisional target longitudinal speed of the vehicle body is set based on the longitudinal load, and a provisional target lateral speed of the vehicle body is set based on the lateral load, When the provisional target longitudinal speed is equal to or higher than the longitudinal speed upper limit or when the provisional target lateral speed is equal to or higher than the lateral speed upper limit, the provisional target longitudinal speed is multiplied by a correction coefficient to thereby set a target longitudinal speed, and the provisional target lateral speed is multiplied by the correction coefficient to thereby set a target lateral speed, the correction coefficient being set to be greater than 0 and equal to or less than 1, When the provisional target longitudinal speed is less than the longitudinal speed upper limit and the provisional target lateral speed is less than the lateral speed upper limit, the provisional target longitudinal speed is set as the target longitudinal speed and the provisional target lateral speed is set as the target lateral speed, and The drive unit is controlled based on the target front-rear speed and the target lateral speed.

2. The cart according to claim 1, wherein: The smaller of a first value and a second value is set as the correction coefficient, the first value is calculated by dividing the longitudinal speed upper limit by the provisional target longitudinal speed, and the second value is calculated by dividing the lateral speed upper limit by the provisional target lateral speed.

3. The stroller according to claim 1 or 2, wherein: The at least one omnidirectional wheel includes a pair of omnidirectional wheels arranged at intervals in the transverse direction, The load sensor is configured to detect a moment about a vertical axis in addition to the fore-aft load and the lateral load, and The control unit is configured to: A target angular velocity of the vehicle body is set based on the moment, and The drive unit is controlled based on the target front-rear velocity, the target lateral velocity, and the target angular velocity.

4. The cart according to claim 3, wherein: The control unit sets the target angular velocity independently of the correction coefficient.

5. The cart according to claim 4, wherein: The drive unit includes a plurality of electric motors, and The control unit is configured to: setting a first rotational speed of each electric motor based on the target fore-aft speed, setting a second rotational speed of each electric motor based on the target lateral speed, setting a third rotational speed of each electric motor based on the target angular speed, and setting a provisional target rotational speed of each electric motor based on the first, second, and third rotational speeds, When the provisional target speed of at least one of the plurality of electric motors is higher than a maximum speed, the target speed of each electric motor is set based on a product of a motor speed correction coefficient and the first speed, a product of the motor speed correction coefficient and the second speed, and the third speed, the motor speed correction coefficient being set to be greater than 0 and equal to or less than 1, and When the provisional target rotation speed of all electric motors is equal to or lower than the maximum rotation speed, the provisional target rotation speed is set as the target rotation speed.

6. The cart according to claim 5, wherein: The motor rotation speed correction coefficient is set based on the following equation 1, where "kr" represents the motor rotation speed correction coefficient, "rm" represents the maximum rotation speed, "r1" represents the first rotation speed, "r2" represents the second rotation speed, and "r3" represents the third rotation speed, [Equation 1] kr = (rm - |r3|) / (|r1| + |r2|).

7. The stroller according to claim 5 or 6, wherein: The reference point of the target angular velocity is arranged at a midpoint of a line segment connecting the pair of omnidirectional wheels.

8. The cart according to claim 7, wherein: Each omni wheel includes: a pair of drive plates rotatably supported by the vehicle body and coaxially arranged to face each other; a plurality of drive rollers arranged on an outer peripheral portion of each drive disc at intervals in a circumferential direction, each drive roller being supported so as to rotate about an axis inclined to the circumferential direction of the drive disc; and a main wheel formed in an annular shape, the main wheel being arranged between the pair of drive discs, contacting the drive roller, and configured to rotate about a central axis and an annular axis, The plurality of electric motors include four electric motors corresponding to respective drive discs and configured to rotate the respective drive discs, and The control unit is configured to set a target rotation speed of each electric motor based on the target front-rear speed, the target lateral speed, and the target angular speed.

9. A cart, comprising: body; at least one omnidirectional wheel provided at the vehicle body and configured to move the vehicle body in all directions along a floor; a drive unit configured to drive each omnidirectional wheel; a handle provided on the vehicle body and configured to receive an operation from a user; a load sensor configured to detect a load applied to the handle; as well as a control unit configured to control the driving unit based on the load detected by the load sensor, Wherein, the control unit is configured as follows: setting a provisional target velocity vector of the vehicle body based on the load, When the magnitude of the provisional target speed vector is equal to or greater than an upper limit, the provisional target speed vector is multiplied by a correction coefficient to thereby set a target speed vector, the correction coefficient being set to be greater than 0 and equal to or less than 1, When the magnitude of the provisional target speed vector is smaller than the upper limit, the provisional target speed vector is set as the target speed vector, and The drive unit is controlled based on the target velocity vector.

10. The cart according to claim 9, wherein: A value calculated by dividing the upper limit by the magnitude of the provisional target speed vector is set as the correction coefficient.

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