Transport Auxiliary Equipment

Abstract

To provide a transfer assist device for appropriately assisting cornering of a bed with casters.SOLUTION: A transfer assist device 1 includes first and second mecanum wheels 21R and 21L to be attached to a bed 10, and first and second motors 22R and 22L drivingly connected to the first and second mecanum wheels 21R and 21L, first and second current sensors SW1 and SW2 for detecting signals corresponding to rotating states of the first and second mecanum wheels 21R and 21L, a six-axial sensor SW5 for detecting the turning of the bed 10 around a rotary shaft perpendicular to a transfer surface F, and a controller 4. When it is determined that the bed 10 is moving forward or backward and is not turning, the controller 4 assists manual push movement in a longitudinal direction, however, when it is determined that the bed 10 is turning while moving forward or backward, assists manual push movement in both the longitudinal direction and the lateral direction.SELECTED DRAWING: Figure 16

Description

[Technical Field]

[0001] The present disclosure relates to a transport assist device. [Background technology]

[0002] For example, Patent Document 1 discloses an auxiliary propulsion system that uses Mecanum wheels in the drive unit. This auxiliary propulsion system includes a pair of Mecanum wheels connected to a chassis, a motor that drives each Mecanum wheel, and a control system that detects changes in the rotation speed of each motor.

[0003] According to Patent Document 1, when the chassis moves in a predetermined direction, the operator applies a force in the same direction. When each Mecanum wheel rotates due to the applied force, the resulting change in rotation speed is reported to the control system. Based on this report, the control system starts the electric rotation of the motor. This electric rotation assists the movement of the chassis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2016-525977 Summary of the Invention [Problem to be solved by the invention]

[0005] Now, consider a situation where the configuration described in Patent Document 1 is applied to a bed with casters and the bed is cornered. In this case, the bed is pushed forward and backward while turning, so it is possible to consider assisting the bed in the forward and backward directions.

[0006] However, after extensive research, the inventors realized that simply providing assistance in the front-to-rear direction during cornering would result in an excessively small cornering radius, which could cause interference between the front or rear end of the bed and the corners of passageways such as crossroads or T-junctions. Such interference is inconvenient for cornering assistance.

[0007] The technology disclosed herein has been made in consideration of the above points, and its purpose is to appropriately assist cornering of a caster-equipped bed. [Means for solving the problem]

[0008] A first aspect of the present disclosure relates to a transport assist device for assisting manual pushing of a caster-equipped bed. The transport assist device includes first and second Mecanum wheels attached to the underside of the bed and in contact with the transport surface of the bed, first and second motors drivingly connected to the first and second Mecanum wheels, respectively, a status sensor that detects signals corresponding to the rotation states of the first and second Mecanum wheels, a rotation sensor that detects rotation of the bed around a rotation axis perpendicular to the transport surface, and a controller that controls the first and second motors. The controller determines whether the bed is moving forward or backward based on the detection signals of the status sensor and the rotation sensor, and and determining whether the bed is turning. When the controller determines that the bed is moving forward or backward and not turning, the controller drives the first and second Mecanum wheels via the first and second motors to assist the manual push movement in the forward and backward direction, whereas when the controller determines that the bed is turning while moving forward or backward, the controller drives the first and second Mecanum wheels via the first and second motors to assist the manual push movement in both the forward and backward direction and a lateral direction that is perpendicular to the forward and backward direction and extends along the conveying surface.

[0009] According to the first aspect, the controller assists manual push movement not only in the forward and backward directions but also in the lateral direction. When cornering a bed, it is thought that force is also applied in the radial direction of the cornering, i.e., in the lateral direction of the bed. Therefore, by assisting with such lateral force, the bed can slide laterally when cornering. This increases the cornering radius and reduces interference between the front or rear end of the bed and the corner of the aisle. This makes it possible to appropriately assist cornering of a caster-equipped bed.

[0010] According to a second aspect of the present disclosure, the status sensor may be configured with first and second current sensors that detect induced currents flowing in the first and second motors when the first and second mecanum wheels rotate, respectively. The controller estimates a vertical acceleration indicating the acceleration of the first and second mecanum wheels in the forward / backward direction and a lateral acceleration indicating the acceleration of the first and second mecanum wheels in the lateral direction based on the detection signals of the first and second current sensors, respectively, and executes a first control that sets a command rotation speed of the first and second motors to follow the manual push movement based on at least one of the vertical acceleration and the lateral acceleration. When the controller determines that the bed is turning while moving forward or backward, it may execute the first control based on the vertical acceleration for the forward / backward direction, while adjusting the lateral acceleration for the lateral direction so that it decreases by a predetermined ratio greater than 0, and execute the first control based on the adjusted lateral acceleration.

[0011] According to the second aspect, by detecting the induced current, it is possible to estimate the torque that caused the induced current (the torque that tries to rotate the Mecanum wheel) and, by extension, the acceleration corresponding to that torque. By estimating the acceleration of each wheel, it is possible to estimate the direction in which an external force is acting.

[0012] Then, assistance is provided in the forward and backward directions to allow the bed to follow the manual push movement, while the acceleration in the lateral direction is reduced and a first control is performed based on this acceleration. Reducing the acceleration in the lateral direction is equivalent to estimating the external force acting in the lateral direction to be smaller than the external force that actually acts. By underestimating the external force, assistance is provided in the lateral direction that is not sufficient to allow the bed to follow the manual push movement. As a result, excessive sliding in the lateral direction (sliding more than intended by the carrier) is suppressed, and the cornering radius can be kept within an appropriate range. This is advantageous in providing appropriate assistance for cornering of a caster-equipped bed.

[0013] Furthermore, according to a third aspect of the present disclosure, the predetermined ratio may be set to shift the rotation center of the bed from the center position of the first and second Mecanum wheels toward the front end of the bed.

[0014] According to the third aspect, by shifting the swivel center of the bed toward the front end, it is possible to achieve a motion in which the rear end of the bed swivels more than the front end when cornering. By swivel- ing the rear end more, it is possible to reduce interference between the rear end and the corners of the aisle. This is advantageous in providing appropriate assistance for cornering of the caster-equipped bed.

[0015] Furthermore, according to a fourth aspect of the present disclosure, when the controller determines that the bed is moving forward or backward and not rotating, it executes the first control based on the vertical acceleration and executes the second control that increases the command rotation speed, and when the controller determines that the bed is rotating while moving forward or backward, it executes the first control and the second control in sequence based on the vertical acceleration for the forward / backward direction, and executes the first control based on the adjusted lateral acceleration for the lateral direction, and does not execute the second control.

[0016] According to the fourth aspect, by performing the second control in the forward / backward direction, the bed not only follows the manual push movement but also reduces the burden on the carrier by the amount of the increased commanded rotation speed. This improves the comfort of pushing the bed in the forward / backward direction and provides the carrier with an appropriate "sense of assistance." On the other hand, the second control is intentionally not performed in the lateral direction. This suppresses excessive sliding in the lateral direction (sliding more than the carrier intended) and keeps the cornering radius within an appropriate range. This is advantageous in providing appropriate assistance to the cornering of the caster-equipped bed.

[0017] According to a fifth aspect of the present disclosure, the first and second Mecanum wheels may be arranged side by side in the horizontal direction, each of the first and second Mecanum wheels having a wheel body that rotates around a rotation axis extending in the horizontal direction, and a plurality of barrel-shaped rollers that are arranged along the outer periphery of the wheel body and each rotate around an inclined axis that is inclined with respect to both the front-to-rear direction and the horizontal direction, and the inclined axis of the first Mecanum wheel may be inclined with respect to the inclined axis of the second Mecanum wheel so as to be line-symmetrical with respect to the front-to-rear direction.

[0018] The fifth aspect of the present invention allows the first and second Mecanum wheels to rotate in opposite directions, generating a thrust that causes the bed to turn. This configuration is effective in providing appropriate assistance to the cornering of a caster-equipped bed.

[0019] Furthermore, according to a sixth aspect of the present disclosure, when the controller determines that the bed is moving forward or backward and not rotating, it may set each command rotation speed to rotate both the first and second Mecanum wheels forward or backward, and in setting the command rotation speed, it may set the absolute values ​​of the command rotation speed for the first Mecanum wheel and the second Mecanum wheel to be equal, and when it determines that the bed is rotating while moving forward or backward, it may set the command rotation speed so that the absolute values ​​of the command rotation speed for the first Mecanum wheel and the second Mecanum wheel are different.

[0020] According to the sixth aspect, by making the absolute value of the command rotation speed equal during forward and backward movement, more stable forward and backward movement can be achieved regardless of the direction of the caster. On the other hand, by intentionally making the absolute value different during cornering, cornering along a desired trajectory can be achieved. [Effects of the Invention]

[0021] As described above, according to the present disclosure, it is possible to appropriately assist a caster-equipped bed in cornering. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a side view illustrating an example of the overall configuration of a transport assist device and a bed with casters. FIG. [Figure 2] 1 is a bottom view illustrating an example of the overall configuration of a transport assist device and a bed with casters. FIG. [Figure 3] FIG. 2 is a perspective view illustrating the configuration of a transport assist device. [Figure 4] FIG. 2 is a plan view illustrating the configuration of a transport assist device. [Figure 5] FIG. 2 is a side view illustrating the configuration of a transport assist device. [Figure 6] FIG. 2 is a block diagram illustrating the configuration of a control system of the transport assist device. [Figure 7] 10A and 10B are diagrams for explaining the operation of the first and second Mecanum wheels. [Figure 8] FIG. 2 is a diagram for explaining a detection target of a six-axis sensor. [Figure 9] 4 is a flowchart illustrating main processing performed by a controller. [Figure 10] 10 is a flowchart illustrating a process related to determination of a movement direction. [Figure 11] FIG. 2 is a control block diagram illustrating a configuration of compliance control. [Figure 12] FIG. 1 is a conceptual diagram for explaining the basic concept of compliance control. [Figure 13] FIG. 10 is a diagram illustrating an example of a change in speed increase amount relative to the rotation speed. [Figure 14] FIG. 10 is a diagram illustrating an example of a command rotation speed obtained by speed increase control. [Figure 15] 10 is a flowchart illustrating compliance control and speed increase control. [Figure 16] 10 is a flowchart illustrating a control relating to cornering. [Figure 17] FIG. 10 is a diagram illustrating an example of a trajectory of a bed during cornering. [Figure 18] 10 is a flowchart illustrating a safety limit control. [Figure 19] FIG. 17 is a diagram corresponding to FIG. 17 and shows a conventional example of the trajectory of the bed. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0024] FIG. 1 is a side view illustrating the overall configuration of a transport assistance device 1 and a bed with casters 10, and FIG. 2 is a bottom view illustrating the overall configuration of the transport assistance device 1 and a bed with casters 10. As shown in FIG.

[0025] 3 is a perspective view illustrating the configuration of the transport auxiliary device 1, FIG. 4 is a plan view illustrating the configuration of the transport auxiliary device 1, and FIG. 5 is a side view illustrating the configuration of the transport auxiliary device 1.

[0026] Fig. 6 is a block diagram illustrating the configuration of the control system of the transport assist device 1, Fig. 7 is a diagram for explaining the operation of the first and second Mecanum wheels 21R, 21L, and Fig. 8 is a diagram for explaining the detection target of the six-axis sensor SW5.

[0027] As shown in Figures 1 and 2, a transport assistance device 1 according to this embodiment is attached to a bed with casters (hereinafter simply referred to as "bed") 10. This bed 10 is equipped with a plurality of casters 14 including front wheels 14F and rear wheels 14B, and is intended to be used, for example, as a medical bed. The transport assistance device 1 is a device for assisting the manual movement of such a bed 10.

[0028] Hereinafter, the longitudinal direction of bed 10, i.e., the direction in which a person lies on bed 10, will be referred to as the "front-to-back direction" or "longitudinal direction," the direction toward the feet along the front-to-back direction will be referred to as the "front," and the direction toward the pillow will be referred to as the "rear."

[0029] Similarly, the short direction of the bed 10, that is, the direction perpendicular to the front-to-back direction on a horizontal plane, is defined as the "left-to-right direction" or "lateral direction," and the direction along this left-to-right direction toward the depth of the paper in FIG. 1 is defined as the "right," and the direction along this left-to-right direction toward the front of the paper in FIG. 1 is defined as the "left" (see FIG. 2 for details). Note that the "left-to-right direction" here refers to the left-to-right direction when viewed from the rear to the front. In the following description, "lateral movement" refers to movement along this left-to-right direction. The left-to-right direction (lateral direction) can also be defined as the direction perpendicular to the front-to-back direction and extending along the transport surface F (the floor surface along which the bed 10 travels).

[0030] The bed 10 is supported by the carrier 100. In the illustrated example, the bed 10 is supported at one end (e.g., the rear end) in the front-to-rear direction. The transport assist device 1 operates to assist the carrier 100 in manually pushing and moving the bed 10.

[0031] 1, the bed 10 includes a bed body 11 on which a mattress (not shown) is placed, a frame 12 that supports the bed body 11 from below, a lifting unit 13 that raises and lowers the bed body 11 relative to the frame 12, and a plurality of casters 14 (four in the illustrated example) arranged on the underside of the bed 10. When used as a medical bed, the bed 10 weighs, for example, between 60 kg and 300 kg.

[0032] Here, the bed body 11 has a headboard 11h arranged at the rear end side of the bed 10, a footboard 11f arranged at the front end side opposite the rear end side in the front-to-rear direction, and side rails 11s arranged on both the left and right sides of the bed 10.

[0033] Of these, the headboard 11h is supported from the rear by the carrier 100 to manually move the bed 10. The headboard 11h functions as a support part to which the carrier 100 applies force. A handle, a grip, or other member may be attached to the headboard 11h or integrated with the headboard 11h, thereby making these members the support part. The footboard 11f, the side rails 11s, etc. may also be supported.

[0034] As shown in FIG. 2, the frame 12 is configured in a rectangular frame shape, and its four sides are formed by a front frame 12F, a right frame 12R, a left frame 12L, and a rear frame 12B.

[0035] Here, the front frame 12F is disposed on the front side of the bed 10 and extends in the left-right direction. The right frame 12R is disposed on the right side of the bed 10 and extends in the front-rear direction. The left frame 12L is disposed on the left side of the bed 10 and extends in the front-rear direction. The rear frame 12B is disposed on the rear side of the bed 10 and extends in the left-right direction.

[0036] 1 and 2, the front wheels 14F and rear wheels 14B that make up the plurality of casters 14 are arranged at the four corners of the underside of the bed 10. Two front wheels 14F and two rear wheels 14B are provided along the left-right direction. The plurality of casters 14 support the frame 12, the lifting section 13, and the bed body 11 on the conveyance surface F.

[0037] Each caster 14 is a so-called free caster and includes a mounting portion 14a fixed to the underside of the bed 10, a fork portion 14b that can rotate about a rotation axis Oc relative to the mounting portion 14a, and a wheel 14c that is rotatably supported by the fork portion 14b. The rotation axis Oc of each fork portion 14b extends in the vertical direction (the height direction of the bed 10). The rotation axis of each wheel 14c extends along a horizontal plane. This rotation axis is tilted in the left-right direction as the fork portion 14b rotates relative to the mounting portion 14a.

[0038] The transport auxiliary device 1 is disposed so as to bridge between a midpoint in the front-to-rear direction of the right frame 12R and a midpoint in the front-to-rear direction of the left frame L. The transport auxiliary device 1 is disposed between the front wheels 14F and the rear wheels 14B in the front-to-rear direction, and is disposed in the center of the bed 10 in the left-to-right direction.

[0039] 1 to 6, the transportation auxiliary device 1 includes a storage box 6, a fixture 7, first and second Mecanum wheels 21R, 21L, first and second motors 22R, 22L, a controller 4, first and second current sensors SW1, SW2 as status sensors, first and second rotation sensors SW3, SW4, and a six-axis sensor SW5 as a rotation sensor (the first and second motors 22R, 22L and the sensors SW1 to SW5 are only shown in FIG. 6). Hereinafter, of the first and second Mecanum wheels 21R, 21L, the first Mecanum wheel 21R is assumed to be located on the right side, and the second Mecanum wheel 21L is assumed to be located on the left side.

[0040] Of these elements, the controller 4 and the six-axis sensor SW5 are housed in the housing box 6, while the mounting fixture 7, the first and second Mecanum wheels 21R, 21L, the first and second motors 22R, 22L, the first and second current sensors SW1, SW2, and the first and second rotation sensors SW3, SW4 are located outside the housing box 6.

[0041] As described above, the storage box 6 stores the controller 4. The storage box 6 is disposed between the first Mecanum wheel 21R and the second Mecanum wheel 21L in the left-right direction.

[0042] The storage box 6 is attached to a fixture 7 together with the first and second Mecanum wheels 21R, 21L, and is attached to the bottom of the bed 10 via this fixture 7. The fixture 7 is detachable from the bottom of the bed 10. In other words, the transport assistance device 1 according to this embodiment can be retrofitted to the bed 10 and can be detached as needed.

[0043] More specifically, as shown in Figures 2 to 5, the mounting fixture 7 according to this embodiment has a front rail member 71f, a rear rail member 71b, and first and second arm members 72R and 72L that rotatably support the first and second Mecanum wheels 21R and 21L, respectively.

[0044] The front rail member 71f and the rear rail member 71b are spaced apart in the front-to-rear direction and span the front-to-rear center of the right frame 12R and the front-to-rear center of the left frame 12L, respectively. The front rail member 71f and the rear rail member 71b are detachable from the right frame 12R and the left frame 12L. The first and second Mecanum wheels 21R, 21L and the storage box 6 are arranged between the front rail member 71f and the rear rail member 71b in the front-to-rear direction.

[0045] 3 and 4, the first arm member 72R is swingably supported by the rear rail member 71b. The front end of the first arm member 72R rotatably supports the first Mecanum wheel 21R. The first arm member 72R is positioned between the first Mecanum wheel 21R and the storage box 6 in the left-right direction.

[0046] One end of a first tension spring 75R is anchored to the upper end of the first arm member 72R, and the other end of the first tension spring 75R is anchored to a first bracket 76R fixed to the front rail member 71f.

[0047] 3 and 4, the second arm member 72L is swingably supported by the rear rail member 71b, similar to the first arm member 72R. The front end of the second arm member 72L rotatably supports the second Mecanum wheel 21L. The second arm member 72L is positioned between the second Mecanum wheel 21L and the storage box 6 in the left-right direction.

[0048] One end of a second tension spring 75L is secured to the upper end of the second arm member 72L, and the other end of the second tension spring 75L is secured to a second bracket 76L fixed to the front rail member 71f (see also FIG. 5).

[0049] As shown in FIGS. 1 and 2, the first and second Mecanum wheels 21R, 21L are attached to the lower part (bottom) of the bed 10. The first and second Mecanum wheels 21R, 21L are in contact with the conveying surface F of the bed 10. The conveying surface F is only shown in FIG. 1. The first and second Mecanum wheels 21R, 21L are disposed rearward of the front wheels 14F and in front of the rear wheels 14B. In this embodiment, the first and second Mecanum wheels 21R, 21L are disposed side by side in the left-right direction, which is the short side direction, as shown in FIG. 2.

[0050] In detail, as shown in Figures 3 to 5, the first Mecanum wheel 21R has a first wheel body 211R that rotates around a first rotation axis Oy1, and a plurality of first barrel-shaped rollers 212R that are arranged along the outer periphery of the first wheel body 211R and each rotates around a first inclined axis Or that is inclined with respect to the first rotation axis Oy1.

[0051] On the other hand, the second Mecanum wheel 21L has a second wheel body 211L that rotates around a second rotation axis Oy2, and a plurality of second barrel-shaped rollers 212L that are arranged along the outer periphery of the second wheel body 211L and each rotate around a second inclined axis Ol that is inclined in a direction different from the first inclined axis Or relative to the second rotation axis Oy2.

[0052] Here, both the first and second rotation axes Oy1 and Oy2 extend in the left-right direction. The first tilt axis Or is tilted with respect to the second tilt axis Ol so as to be symmetrical with respect to the front-to-rear direction (see the axis of symmetry Os in FIG. 4). In other words, if a plane extending in the up-down and front-to-rear directions is taken as a mirror plane, the first tilt axis Or and the second tilt axis Ol extend so as to be mirror-symmetrical with respect to the mirror plane.

[0053] Furthermore, when viewed from above (when viewed from a plane) as in Figure 4, the first and second inclined axes Or, Ol each extend from the inside to the outside in the left-right direction (from the center in the left-right direction to the right or left) as they move from the rear to the front along the fore-and-aft direction.

[0054] Specifically, the first inclined axis Or extends from the center to the right in the front-rear direction, while the second inclined axis Ol extends from the center to the left in the front-rear direction.

[0055] More specifically, the tilt angle θr of the first tilt axis Or relative to the first rotation axis Oy1 is set to 45° in plan view. Similarly, the tilt angle θl of the second tilt axis Ol relative to the second rotation axis Oy2 is also set to 45° in plan view. Note that the tilt direction and tilt angle of each barrel-shaped roller 212R, 212L are not limited to these examples. For example, the entire conveyance auxiliary device 1 may be rearranged from the state illustrated in FIG. 2 to a state rotated a predetermined angle around the z-axis extending in the vertical direction.

[0056] As described above, the first and second Mecanum wheels 21R, 21L are connected to each other via the front rail member 71f and the rear rail member 71b shown in Fig. 3 etc. Therefore, the first and second Mecanum wheels 21R, 21L move together in the front-rear and left-right directions and rotate together around a rotation axis perpendicular to the horizontal plane.

[0057] The first and second motors 22R, 22L are drivingly connected to the first and second Mecanum wheels 21R, 21L, respectively. Specifically, the first and second motors 22R, 22L are each configured as a so-called three-phase DC brushless motor. Both the first and second motors 22R, 22L are electrically connected to the controller 4 and are controlled by the controller 4.

[0058] The first and second motors 22R, 22L are supplied with motor currents corresponding to the torque loads during their respective rotations. The motor currents can be used to switch the rotation speeds of the first and second motors 22R, 22L and their rotation directions between forward and reverse.

[0059] The first motor 22R is connected to the first Mecanum wheel 21R so as to transmit a driving force (torque). The second motor 22L is connected to the second Mecanum wheel 21L so as to transmit a driving force (torque).

[0060] When the first motor 22R rotates, its driving force is transmitted to rotate the first Mecanum wheel 21R. Similarly, when the second motor 22L rotates, its driving force is transmitted to rotate the second Mecanum wheel 21L.

[0061] In this embodiment, the first Mecanum wheel 21R is configured to rotate forward by rotating the first motor 22R in the normal direction, and the first Mecanum wheel 21R is configured to rotate backward by rotating the first motor 22R in the reverse direction. Similarly, in this embodiment, the second Mecanum wheel 21L is configured to rotate forward by rotating the second motor 22L in the normal direction, and the second Mecanum wheel 21L is configured to rotate backward by rotating the second motor 22L in the reverse direction.

[0062] The first motor 22R is built into the first Mecanum wheel 21R, and the second motor 22L is built into the second Mecanum wheel 21L. By building the first and second motors 22R and 22L into the wheels in this way, the entire transport auxiliary device 1 can be simplified and made compact.

[0063] In addition, the first and second current sensors SW1 and SW2, which serve as state sensors, detect signals corresponding to the rotational states of the first and second Mecanum wheels 22R and 22L.

[0064] Specifically, the first current sensor SW1 detects the induced current flowing through the first motor 22R when the first Mecanum wheel 21R rotates. That is, when the first Mecanum wheel 21R rotates due to an external force, the rotor and stator of the first motor 22R rotate relative to each other, generating an induced current. The induced current detected by the first current sensor SW1 corresponds to the q-axis current.

[0065] Here, the magnitude of the induced current is proportional to the torque acting on the first Mecanum wheel 21R when the first Mecanum wheel 21R rotates due to an external force. The magnitude of this torque is related to the magnitude of the external force received by the bed 10 and, ultimately, the amount of change in speed of the bed 10 due to the external force. The sign of the induced current is related to the direction of rotation of the first Mecanum wheel 21R when the first Mecanum wheel 21R rotates due to an external force. The sign of the induced current is opposite to the sign of the motor current that flows when the first motor 22R is driven.

[0066] The second current sensor SW2 detects the induced current flowing through the second motor 22L when the second Mecanum wheel 21L rotates. In other words, when the second Mecanum wheel 21L rotates due to an external force, the rotor and stator of the second motor 22L rotate relative to each other, generating an induced current. The induced current detected by the second current sensor SW2 corresponds to the q-axis current.

[0067] Here, the magnitude of the induced current is proportional to the torque acting on the second Mecanum wheel 21L when the second Mecanum wheel 21L rotates due to an external force. The magnitude of this torque is related to the magnitude of the external force received by the bed 10 and, ultimately, the amount of change in speed of the bed 10 due to the external force. The sign of the induced current is related to the direction of rotation of the second Mecanum wheel 21L when the second Mecanum wheel 21L rotates due to an external force. The sign of the induced current is opposite to the sign of the motor current that flows when the second motor 22L is driven.

[0068] For example, if an external force causes the first Mecanum wheel 21R to rotate forward and the second Mecanum wheel 21L to rotate backward at the same time, the first current sensor SW1 will detect an induced current with the same sign as when the first motor 22R is rotated in the reverse direction, and the second current sensor SW2 will detect an induced current with the same sign as when the second motor 22L is rotated in the forward direction.

[0069] As will be described in detail below, the controller 4 according to this embodiment is configured to provide assistance in the forward direction, i.e., in the direction of action of the external force, by feeding back the torque related to the induced current (more specifically, by rotating the first and second motors 22R, 22L at a command rotation speed corresponding to the torque).

[0070] Furthermore, the first and second rotation sensors SW3 and SW4 detect the rotation speeds of the first and second motors 22R and 22L, respectively. Specifically, the first and second rotation sensors SW3 and SW4 according to this embodiment are each configured as encoders. The first rotation sensor SW3, which functions as an encoder, detects the rotation speed and rotation angle of the first motor 22R, and the second rotation sensor SW4, which also functions as an encoder, detects the rotation speed and rotation angle of the second motor 22L.

[0071] 8, the six-axis sensor SW5 as a rotation sensor detects the rotation of the bed 10 around a rotation axis (z-axis in FIG. 8) perpendicular to the conveying surface F. More specifically, the six-axis sensor SW5 is configured to be able to detect at least the angular velocity of the rotation angle (so-called yaw angle ψ) around the z-axis along the vertical direction.

[0072] More specifically, the six-axis sensor SW5 according to this embodiment can detect not only the angular velocity of the yaw angle ψ, but also acceleration in three directions along the x-axis extending in the front-to-back direction, the y-axis extending in the left-to-right direction, and the z-axis extending in the up-to-down direction, the angular velocity of the rotation angle around the x-axis (the so-called roll angle φ), and the angular velocity of the rotation angle around the y-axis (the so-called pitch angle θ). The detection signals of the six-axis sensor SW5 are input to the controller 4.

[0073] The controller 4 controls the first and second motors 22R, 22L based on electrical signals input from the various sensors SW1 to SW5. The controller 4 has a CPU, a memory, and an input / output bus, and is configured by, for example, a control board.

[0074] Specifically, the controller 4 according to this embodiment sets the command rotation speeds of the first and second motors 22R, 22L based on the detection signals input from the various sensors SW1 to SW5. The controller 4 inputs motor currents corresponding to the set command rotation speeds to the first and second motors 22R, 22L. As a result, the first and second motors 22R, 22L rotate at the command rotation speeds set by the controller 4.

[0075] At this time, the first Mecanum wheel 21R rotates at the same rotation speed as the first motor 22R, and the second Mecanum wheel 21L rotates at the same rotation speed as the second motor 22L. In other words, setting the command rotation speeds of the first and second motors 22R and 22L is equivalent to setting the command rotation speeds of the first and second Mecanum wheels 21R and 21L.

[0076] Furthermore, by changing the sign of each command rotation speed, the rotation direction of the first motor 22R and the second motor 22L can be changed individually. By changing the rotation direction of each motor 22R, 22L, the corresponding Mecanum wheels 21R, 21L can be switched between forward rotation and backward rotation.

[0077] In this embodiment, when the first Mecanum wheel 21R located on the right side is rotated forward, a thrust force can be applied to the transport auxiliary device 1 and the bed 10 diagonally forward to the left (arrow A in FIG. 7). 11 7). On the other hand, when the second Mecanum wheel 21L located on the left side is rotated forward, the transport assist device 1 can apply a thrust force to the bed 10 diagonally forward to the right (see arrow A in FIG. 7). 12 (See

[0078] 7, for example, when both the first and second Mecanum wheels 21R and 21L are rotated forward, the leftward thrust applied by rotating the first Mecanum wheel 21R forward and the rightward thrust applied by rotating the second Mecanum wheel 21L forward cancel each other out, and a forward thrust can be applied to the entire transport assist device 1. This thrust can assist the forward movement of the bed 10.

[0079] Similarly, when the first Mecanum wheel 21R located on the right side is rotated backward, a thrust force can be applied to the transport auxiliary device 1 and the bed 10 obliquely backward to the right (arrow A in FIG. 7). 21 7). On the other hand, when the second Mecanum wheel 21L located on the left side is rotated backward, the transport assist device 1 can apply a thrust force to the bed 10 obliquely backward to the left (see arrow A in FIG. 7). 22 (See

[0080] 7, for example, when both the first and second Mecanum wheels 21R, 21L are rotated backward, the rightward thrust applied by rotating the first Mecanum wheel 21R backward and the leftward thrust applied by rotating the second Mecanum wheel 21L backward cancel each other out, and a rearward thrust can be applied to the entire transport assist device 1. This thrust can assist the rearward movement of the bed 10.

[0081] On the other hand, when one of the first and second Mecanum wheels 21R, 21L is rotated forward and the other is rotated backward, the transport auxiliary device 1 applies a thrust to the bed 10 in the left and right directions.

[0082] In the example shown in the lower left of FIG. 7, a thrust in the right direction is applied to the bed 10 by rotating the first Mecanum wheel 21R backward and rotating the second Mecanum wheel 21L forward.

[0083] Furthermore, when only one of the first and second Mecanum wheels 21R, 21L is rotated forward or backward, the transport auxiliary device 1 applies a thrust to the bed 10 in an oblique direction.

[0084] In the example shown in the lower right of Figure 7, by rotating only the second Mecanum wheel 21L forward, the bed 10 can be propelled diagonally forward to the right. On the other hand, by rotating only the first Mecanum wheel 21R forward, the bed 10 can be assisted in moving diagonally forward to the left (not shown).

[0085] The transport assistance device 1 is configured to assist the transporter 100 in transporting the bed 10 through the thrust applied as described above by operating the first and second motors 22R, 22L based on the detection signals of various sensors SW1 to SW5.

[0086] To achieve such assistance, the controller 4 according to this embodiment determines the direction in which the external force acts (hereinafter simply referred to as the "direction of action") based on the detection signals of the various sensors SW1 to SW5, and operates the first and second motors 22R, 22L to exert a thrust along the direction of action.

[0087] For example, if it is determined that an external force is acting from the rear toward the front as a result of the headboard 11h being pushed forward from the rear, the controller 4 rotates both the first and second motors 22R, 22L forward, thereby rotating both the first and second Mecanum wheels 21R, 21L forward, which makes it possible to assist the forward movement of the bed 10 as shown in the upper left of FIG.

[0088] Furthermore, the first and second Mecanum wheels 21R, 21L are allowed to rotate forward and backward even when the corresponding motors 22R, 22L are not driven, which reduces wobbling when the bed 10 is manually pushed and stabilizes the transport of the bed 10.

[0089] The assistance provided by the controller 4 will be described in detail below with reference to FIG. 9 and other figures.

[0090] Here, FIG. 9 is a flowchart illustrating the main processing performed by the controller 4. FIG. 10 is a flowchart illustrating processing related to determining the direction of movement. FIG. 11 is a control block diagram that schematically illustrates the configuration of compliance control. FIG. 12 is a conceptual diagram for explaining the basic concept of compliance control. FIG. 13 is a diagram illustrating changes in the speed increase amount relative to the rotation speed. FIG. 14 is a diagram illustrating an example of a command rotation speed obtained by speed increase control. FIG. 15 is a flowchart illustrating compliance control and speed increase control.

[0091] Moreover, Fig. 16 is a flowchart illustrating control relating to cornering, Fig. 17 is a diagram illustrating the trajectory of the bed 10 when cornering, and Fig. 18 is a flowchart illustrating safety limit control.

[0092] First, in step S1 of FIG. 9, the controller 4 reads the detection signals of the five sensors SW1 to SW5 described above.

[0093] In the following step S2, the controller 4 estimates the accelerations of the first and second Mecanum wheels 21R, 21L individually based on the detection signals of the first and second current sensors SW1, SW2.

[0094] Hereinafter, the acceleration of the first Mecanum wheel 21R will be referred to as the “first acceleration,” and the acceleration of the second Mecanum wheel 21R will be referred to as the “second acceleration.” Both the first and second accelerations are the time derivatives of the translational velocity, that is, so-called tangential accelerations.

[0095] The magnitude of the induced current detected by each of the first and second current sensors SW1 and SW2 is proportional to the torque (particularly the torque caused by the reaction force) acting on the first and second Mecanum wheels 21R and 21L as they rotate. Based on this proportional relationship, the controller 4 individually estimates the first torque acting on the first Mecanum wheel 21R and the second torque acting on the second Mecanum wheel 21L. In this case, a proportionality coefficient pre-stored in the controller 4 can be used to convert the induced current to torque.

[0096] The controller 4 according to this embodiment assists the movement of the bed 10 by driving the first and second motors 22R and 22L against the reaction forces corresponding to the first and second torques.

[0097] In order to realize such an assist, the controller 4 estimates a first acceleration corresponding to the first torque and a second acceleration corresponding to the second torque based on the following equations (1) and (2).

[0098] a r =(-1) T r / (R m) …(1) a l =(-1) T l / (R m) …(2) In the above equations (1) and (2), T r [Nm] is the first torque, T l [Nm] is the second torque. r [m / s 2 ] is the first acceleration corresponding to the first torque, and a l [m / s 2 ] is the second acceleration corresponding to the second torque.

[0099] Additionally, R [m] is the tire radius of each of the first and second Mecanum wheels 21R, 21L, and m [kg] is the mass of each of the first and second Mecanum wheels 21R, 21L. In this embodiment, the tire radius and mass are the same for the first Mecanum wheel 21R and the second Mecanum wheel 21L.

[0100] In the following step S3, the controller 4 estimates the translational acceleration of the first and second Mecanum wheels 21R, 21L based on the detection signals of the first and second current sensors SW1, SW2.

[0101] Specifically, the controller 4 estimates the first and second accelerations a based on the detection signals of the first and second current sensors SW1 and SW2. r ,a l are used to estimate the vertical acceleration indicating the translational acceleration of the first and second Mecanum wheels 21R, 21L in the front-to-rear direction, and the lateral acceleration indicating the translational acceleration of the first and second Mecanum wheels 21R, 21L in the lateral direction.

[0102] More specifically, when the first and second Mecanum wheels 21R and 21L are configured as shown in FIGS. 3 to 5, the controller 4 controls the first acceleration a r and the second acceleration a l The vertical acceleration is estimated by adding the first acceleration a r and the second acceleration a l The lateral acceleration is estimated by calculating the difference between the calculated values. The details of these calculations are shown in the following equations (3) and (4).

[0103] a x =(a r +a l ) / twenty three) a y =(a r -a l ) / twenty four) In the above equations (3) and (4), a x [m / s 2 ] is the vertical acceleration, and a y [m / s 2 ] is the lateral acceleration. The sign of equation (3) is defined as positive for the front and negative for the rear. The sign may be reversed between the front and rear. Similarly, the sign of equation (4) is defined as positive for the left and negative for the right. The sign may be reversed between the left and right.

[0104] Note that the relational expressions such as equations (3) and (4) also hold true for the rotation speeds of the first and second motors 22R and 22L (that is, the rotation speeds of the first and second Mecanum wheels 21R and 21L).

[0105] where r r [rpm] is the rotation speed of the first motor 22R in the front-rear direction (hereinafter also referred to as "first rotation speed"), and r l [rpm] is the rotation speed of the second motor 22L in the front-rear direction (hereinafter also referred to as the "second rotation speed"). r is the rotation speed detected by the first rotation sensor SW3, and the second rotation speed r l is the rotation speed detected by the second rotation sensor SW4.

[0106] And r x [rpm] is the rotation speed of the first and second motors 22R, 22L in the front-rear direction (hereinafter, also referred to as "vertical rotation speed"), and r y Let [rpm] be the total rotation speed of the first and second motors 22R, 22L in the left-right direction (hereinafter also referred to as the "horizontal rotation speed"). When the first and second Mecanum wheels 21R, 21L are configured and arranged as in this embodiment, the following equations (5) and (6) hold.

[0107] r x =(r r +r l ) / twenty five) r y =(r r -r l ) / 2 …(6) The above equations (5) and (6) can be transformed into the following equations (7) and (8). As shown in the following equations (7) and (8), r x and r y By setting r r and r l can be uniquely determined.

[0108] r r =r x +r y …(7) r l =r x -r y …(8) Furthermore, by multiplying both sides of the above equations (7) and (8) by a constant (=πR / 30) that depends on the tire radius R and the ratio of the circumference of a circle to its circumference, a similar relational expression can be obtained for the velocity. r Let [m / s] be the velocity of the first Mecanum wheel 21R in the forward / backward direction, and v l Let [m / s] be the velocity of the second Mecanum wheel 21L in the forward / backward direction. And v x [m / s] is the overall speed of the first and second Mecanum wheels 21R, 21L in the longitudinal direction (hereinafter also referred to as the "longitudinal speed"), and v y Let [m / s] be the overall speed of the first and second Mecanum wheels 21R, 21L in the left-right direction (hereinafter also referred to as the "lateral speed"). When the first and second Mecanum wheels 21R, 21L are configured and arranged as in this embodiment, the following equations (9) and (10) hold.

[0109] In this case, "velocity" refers to the translational velocity (tangential velocity) of an object undergoing angular motion.

[0110] v x =(v r +v l ) / 2 …(9) v y =(v r -v l ) / 2 …(10) The above equations (9) and (10) can be transformed into the following equations (11) and (12). As shown in the following equations (11) and (12), v x and v y By setting v r and v l can be set uniquely.

[0111] v r =v x +v y …(11) v l =v x -v y…(12) In addition, by utilizing the relationship between the equations, for example, the longitudinal velocity v x and / or lateral velocity v y When the command values ​​of are determined, the vertical rotation speed r required to realize those command values ​​is r and lateral rotation speed r l can be uniquely determined, and the vertical rotation speed r r and / or lateral rotation speed r l The first rotation speed r corresponding to r and the second rotation speed r l It is possible to determine the following.

[0112] Next, based on the detection signals of the first and second rotation sensors SW3 and SW4, the controller 4 allows the first and second Mecanum wheels 21R and 21L to be driven on the condition that the rotation speed of the first and second Mecanum wheels 21R and 21L becomes equal to or greater than a predetermined value (first threshold value).

[0113] Specifically, in step S4 following step S3, the controller 4 determines whether or not either one of the following relational expressions (13) and (14) is satisfied. Through this determination, it is possible to confirm whether or not the bed 10 is actually being transported (whether or not the bed 10 is actually moving).

[0114] r x ≧T1 …(13) r y ≧T1 …(14) In the above equations (13) and (14), T1 [1 / s] is the first threshold value. The magnitude of the first threshold value is stored in advance in the memory of the controller 4, and is set to be equal in the above equations (13) and (14).

[0115] Here, if both of the above formulas (13) and (14) are not satisfied, the controller 4 determines that the bed 10 is not being transported and does not allow the first and second motors 22R, 22L to be driven (step S4: NO). In this case, the control process proceeds to step S5. In this step S5, the controller 4 sets the command rotation speeds of the first and second motors 22R, 22L to zero.

[0116] If the process proceeds to step S5, the command rotation speeds of the first and second motors 22R, 22L (more specifically, the assist speeds described below) are maintained at zero in the subsequent steps S7 to S9 (steps S7 to S9 will be described in detail later). In this case, the controller 4 ends the flow shown in FIG. 9 without driving the first and second motors 22R, 22L.

[0117] On the other hand, if at least one of the above formulas (13) and (14) is satisfied, the controller 4 determines that the bed 10 is actually being transported by an external force, and allows the first and second motors 22R and 22L to be driven (step S4: YES). In this case, the control process proceeds to step S6. In this step S6, the controller 4 sets the command rotation speed (assist rotation speed) of each of the first and second motors 22R and 22L to assist the manual movement caused by the external force. This assist rotation speed is determined by the vertical rotation speed r x and horizontal rotation speed r y This corresponds to the command value.

[0118] Steps S11 to S15 in Fig. 10 each illustrate the processing executed in step S6 in Fig. 9. That is, when the control process proceeds to step S6, the controller 4 starts step S11 in Fig. 10.

[0119] In step S11, the controller 4 calculates the vertical acceleration a estimated in step S3 of FIG. x and lateral acceleration a y Specifically, the controller 4 according to this embodiment determines the direction of movement of the bed 10 based on the vertical acceleration a xand lateral acceleration a y Based on this, it is determined whether the movement direction of the bed 10 is the front-rear direction (whether the bed 10 is moving forward or backward) or the left-right direction.

[0120] More specifically, in step S11, the controller 4 determines whether the following relational expression (15) is satisfied.

[0121] |a y | <T2 …(15) In the above equation (15), T2 [m / s 2 ] is the second threshold. The magnitude of the second threshold is stored in advance in the memory of the controller 4, and is read out as needed.

[0122] Here, if the above formula (15) is not satisfied, the controller 4 determines that the movement direction of the bed 10 is the left-right direction, and proceeds to step S12 (step S11: NO). Details of the processing when proceeding to step S12 will be described later.

[0123] On the other hand, if the above formula (15) is satisfied, the controller 4 determines that the movement direction of the bed 10 is the front-rear direction, and advances the control process to step S13 (step S11: YES).

[0124] In step S13, the controller 4 determines whether or not the bed 10 is rotating around the z-axis shown in Fig. 8 based on the detection signal of the six-axis sensor SW5. More specifically, in step S13, the controller 4 determines whether or not the following relational expression (16) is satisfied.

[0125] |a ψ |≧T3 …(16) In the above equation (16), a ψ [1 / s 2 ] is the angular acceleration of the yaw angle, and T3[1 / s 2] is the third threshold. The magnitude of the third threshold is stored in advance in the memory of the controller 4, and is read out as needed.

[0126] Here, if the above formula (16) is not satisfied, the controller 4 determines that the bed 10 is not rotating (is not rotating), and advances the control process to step S14.

[0127] The case where the process proceeds to step S14 corresponds to the case where it is determined that the bed 10 is moving forward or backward and not rotating. In this case, the controller 4 performs the subsequent steps to calculate the vertical acceleration a obtained by the first and second current sensors SW1 and SW2. x and lateral acceleration a y Based on this, both the compliance control as the first control and the speed increase control as the second control are executed.

[0128] On the other hand, if the above formula (16) is satisfied, the controller 4 determines that the bed 10 is turning (is turning), and advances the control process to step S15.

[0129] The case where the process proceeds to step S15 corresponds to the case where it is determined that the bed 10 is turning while moving forward or backward (i.e., the bed 10 is cornering). In this case, the controller 4 executes control that is optimized for cornering and that assists manual pushing movement in both the forward / backward direction and the left / right direction.

[0130] The processes performed in steps S12 and S14, and the process performed in step S15 will be described in order below. When proceeding to these steps, the controller 4 drives the first and second Mecanum wheels 21R, 21L via the first and second motors 22R, 22L based on the movement direction determined in step S11 so as to assist the movement of the bed 10 along that movement direction. During this process, the controller 4 according to this embodiment executes compliance control as a first control and speed increase control as a second control.

[0131] Compliance control is a process in which the controller 4 controls the acceleration estimated in step S3 (i.e., the vertical acceleration a x and lateral acceleration a y In this compliance control, the controller 4 controls the bed 10 based on a speed command in the front-rear direction or the left-right direction, that is, a vertical speed v x and lateral velocity v y Set the command value.

[0132] As explained in relation to equations (9)-(12), the longitudinal velocity v x and lateral velocity v y By setting the command value of the first rotation speed r r and the second rotation speed r l The command value is uniquely determined.

[0133] Below, the vertical velocity v x and lateral velocity v y The command values ​​of the vertical speed command V x and lateral speed command V y The first rotation speed r of each of the motors 22R and 22L is called r and the second rotation speed r l The command values ​​of the first command speed R r and second command rotation speed R l It is called.

[0134] In this embodiment, the longitudinal speed command Vx and lateral speed command V y and the first command rotation speed R is set to follow the movement of the bed 10. r and second command rotation speed R l is equivalent to setting

[0135] On the other hand, the speed increase control is executed by the controller 4 based on the acceleration estimated in step S3 and the command rotation speed set in the compliance control. In this speed increase control, when the absolute value of the acceleration referred to in the compliance control is equal to or greater than a predetermined value (a fourth threshold T4 described later), the controller 4 increases the longitudinal speed command V set in the compliance control. x and lateral speed command V y (Especially, each speed command V x ,V y (absolute value of

[0136] In this embodiment, the vertical speed command V x and lateral speed command V y Increasing the first command speed R r and second command rotation speed R l (Especially, each command rotation speed R r ,R l is equivalent to increasing the absolute value of

[0137] First, a case where the control process proceeds to step S12 or step S14 will be described. Here, steps S31 to S36 in Fig. 15 exemplify the processing executed in step S12 or S14 in Fig. 10, respectively. That is, when the control process proceeds to step S12 or S14, the controller 4 executes each step in order starting from step S31 in Fig. 15.

[0138] For example, when the process proceeds from step S12 to the flow of FIG. 15, that is, when it is determined that the "movement direction=left / right direction", the controller 4 calculates the lateral acceleration a y and performs compliance control based on the lateral velocity command Vy The speed increase control is performed based on the above.

[0139] On the other hand, when the process proceeds from step S14 to the flow of FIG. 15, that is, when it is determined that the "movement direction=front-rear direction", the controller 4 calculates the vertical acceleration a x and performs compliance control based on the longitudinal velocity command V x The speed increase control is performed based on the above.

[0140] The following will describe in detail the case where the process proceeds from step S14 to the flow of Fig. 15. In the flow of Fig. 15, step S31 relates to compliance control, and steps S32 to S34 relate to speed increase control.

[0141] First, in step S31, the controller 4 inputs the longitudinal acceleration a x Enter the vertical velocity v x The command value of the input vertical acceleration a x is estimated based on the detection signals of the first and second current sensors SW1 and SW2, and the longitudinal acceleration a x This corresponds to the estimated value (measured value) of

[0142] In this control block, s is a Laplace operator, and M represents the inertia of the bed 10 and the transport assist device 1. Furthermore, D is a damping coefficient between the support position of the bed 10 (e.g., the headboard 11h) of the transporter 100 and the first and second Mecanum wheels 21R, 21L, and K is a spring multiplier between the support position and the first and second Mecanum wheels 21R, 21L. The values ​​of M, D, and K are set in advance and stored in the controller 4.

[0143] If the transport auxiliary device 1, the bed 10, and the transported person 100 are considered to be rigid bodies, the vertical velocity v generated when the first and second Mecanum wheels 21R and 21L rotate due to the application of an external force will be xchanges in synchronization with the moving speed of the bed 10 and the conveyed person 100 in the forward and backward direction, and the magnitudes thereof also match each other. In this case, the vertical acceleration a x By integrating the measured value of , the vertical speed command V that follows the manual push movement of the bed 10 is obtained. x This will be obtained.

[0144] However, in reality, the frame 12 of the bed 10, the mounting fixture 7 of the transport auxiliary device 1, etc. are interposed between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L. Due to the deflection of the frame 12, etc., the actual vertical speed v x will change with a delay from the moving speed of the bed 10 and the person being carried 100, or a deviation in value will occur between the moving speed and the moving speed.

[0145] The control block shown in Figure 11 is a model of the effects of such delays and deviations. This control block calculates the physical quantity corresponding to the force (longitudinal acceleration a x , lateral acceleration a y ) is used as input, and the speed command (longitudinal speed command V x , lateral speed command V y ) is the output of compliance control.

[0146] In Figure 11, first, the vertical acceleration a x The actual measured value of the vertical acceleration a is input to the first block B1 after passing through the subtractor P2. x The measured value of is time-integrated. The output of the first block B1 is the vertical acceleration a x The longitudinal speed command V x The controller 4 calculates the current longitudinal speed command V x By adding or integrating the correction amount ΔV to the vertical speed command V x Set.

[0147] The output from block B1 is multiplied by D / M in second block B2, and then input to subtractor P2 via adder P1. The multiplied value input to subtractor P2 is the vertical acceleration a x This feedback is subtracted from the actual measured value of the longitudinal speed command V x (particularly, damping occurring between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L).

[0148] The output from block B1 is also input to the third block B3. In this third block B3, the correction amount ΔV is further integrated over time. The output from the third block B3 is multiplied by K / M in the fourth block B4, and then input to the subtractor P2 via the adder P1. The multiplied value input to the subtractor P2 is multiplied by the vertical acceleration a in the same way as the multiplied value via the second block B2. x This feedback is intended to incorporate a restoring force proportional to the amount of displacement (particularly, a restoring force caused by the deflection between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L).

[0149] Vertical acceleration a x By reflecting these two feedbacks in the above, the acceleration of the bed 10 (particularly the acceleration at the support position of the person 100) is estimated, taking into account deflection, damping, etc. The acceleration is integrated over time in the first block B1 to obtain a speed that follows the movement of the bed 10.

[0150] Furthermore, signal processing (for example, processing using a delay operator) may be performed on the way from the adder P1 to the subtractor P2 to compensate for the time lag caused by feedback.

[0151] For example, as shown in the upper diagram of Fig. 12, when the transport assistance device 1, the bed 10, and the transported person 100 are moving at a constant speed, the acceleration estimated by the first and second current sensors SW1 and SW2 is zero. Figure 11 The vertical acceleration a input to the control block xbecomes zero, and the correction amount ΔV output from the control block also becomes zero. In this case, the transport auxiliary device 1 does not accelerate or decelerate.

[0152] On the other hand, as shown in the center diagram of Fig. 12, when the person 100 is moving faster than the transportation assistance device 1, the acceleration estimated by the first and second current sensors SW1 and SW2 is positive. In this case, an external force is being applied to the bed 10 to push it down (see arrow F1). In this case, Figure 11 The vertical acceleration a input to the control block x becomes positive, and the correction amount ΔV output from the control block also becomes positive. At this time, the restoring force related to the fourth block B4 acts in a direction that increases the correction amount ΔV (see arrow F3). As a result, the transport assistance device 1 accelerates with a delay after the application of the external force so that the speed becomes equal to that of the bed 10 and the transported person 100.

[0153] On the other hand, as shown in the lower diagram of Fig. 12, when the person 100 is moving behind the transportation assistance device 1, the acceleration estimated by the first and second current sensors SW1 and SW2 becomes negative. In this case, an external force that pulls the bed 10 in is being applied (see arrow F2). In this case, Figure 11 The vertical acceleration a input to the control block x becomes negative, and the correction amount ΔV output from that control block also becomes negative. At that time, the restoring force related to the fourth block B4 acts in a direction to reduce the correction amount ΔV (see arrow F4). As a result, the transport assistance device 1 decelerates with a delay after the application of the external force so as to be at the same speed as the bed 10 and the transported person 100.

[0154] In the following steps S32 to S34, the controller 4 executes the above-mentioned speed increase control. When executing this speed increase control, the controller 4 increases the speed command value by a larger amount as the rotation speeds detected by the first and second rotation sensors SW3 and SW4 increase (see FIG. 13).

[0155] Specifically, in step S32, the controller 4 calculates the longitudinal velocity v x The larger the velocity increment v off Set the vertical velocity v x Instead of the vertical rotation speed r x The larger the velocity increment v off may be set.

[0156] Also, if the flow proceeds from step S12 to the flow of FIG. 15, the vertical speed v x Instead of the lateral velocity v y That is, the controller 4 determines the velocity increase amount v based on the moving direction determined in step S11 of FIG. off The following settings are made:

[0157] In the following step S33, the controller 4 determines whether the following relational expression (17) is satisfied: x is equal to or greater than a predetermined value. Through this determination, it is possible to detect whether the bed 10 is being pushed in the direction of movement (detecting the pushing force).

[0158] |a x |≧T4 …(17) In the above equation (17), T4 [m / s 2 ] is a fourth threshold value (predetermined value). The magnitude of the fourth threshold value T4 as a predetermined value is stored in advance in the memory of the controller 4, and is read out as needed.

[0159] If the flow of FIG. 15 is proceeded from step S12, the vertical acceleration a x Instead of lateral acceleration a y is compared. That is, the controller 4 determines whether or not the acceleration in the movement direction determined in step S11 of FIG.

[0160] Here, if the above equation (17) is satisfied (i.e., the vertical acceleration ax is equal to or greater than a predetermined value), the controller 4 determines that the bed 10 is being pressed, and advances the control process to step S34 (step S33: YES).

[0161] In step S34, the controller 4 calculates the speed command (vertical speed command V x ) with a speed increase of v off The controller 4 uses the added value thus obtained as the final speed command (assist speed) (step S36). The assist speed in the longitudinal direction is calculated by adding the above-mentioned longitudinal speed command V x The assist speed in the left and right direction is calculated by the above-mentioned lateral speed command V x is.

[0162] In addition, the speed increase v off Instead of calculating and adding it to the speed command, it is also possible to calculate an increase magnification (>1) that increases as the rotation speed detected by the first and second rotation sensors SW3 and SW4 increases, and multiply the speed command by the increase magnification to perform speed increase control.

[0163] On the other hand, if the above equation (17) is not satisfied (i.e., the vertical acceleration a x is less than the predetermined value), the controller 4 determines that the bed 10 is not being pushed, and proceeds to step S35 (step S33: NO).

[0164] In step S35, the controller 4 executes the third control to reduce the speed command after the second control.

[0165] Specifically, in step S35, the controller 4 calculates the speed increase amount v off After subtracting Δv2 from the value at that time, the control process proceeds to step S34. off The subtraction amount Δv2 may be constant. When the subtraction amount Δv2 is set to a constant, if the state where the bed 10 is not pushed is repeated, the speed increase amount v offwill gradually decrease. Also, when performing this subtraction, the speed increase amount v off is configured not to be less than zero. Thereby, an assist speed for following the movement of the bed 10 is ensured.

[0166] For example, when proceeding from step S33 to step S34 in the n-th loop, the vertical speed command V x will increase by the speed increase amount v x corresponding to the vertical speed v off . Then, when proceeding from step S33 to step S35 in the (n + 1)-th loop, the speed increase amount v off will be subtracted from the value at the time of the n-th loop. Thereafter, when the situation of proceeding from step S33 to step S35 is repeated, the vertical speed command V x will decrease toward the value calculated in step S31.

[0167] FIG. 14 is a diagram comparing the assist rotation speed (broken line) when compliance control is executed and speed increase control is not executed, and the assist rotation speed (solid line) when both compliance control and speed increase control are executed. The circles in FIG. 14 indicate the timings (the timings when the determination in step S33 becomes YES) at which the bed 10 is determined to be pushed.

[0168] When only compliance control is executed, the assist rotation speed rises after lagging behind the movement of the bed 10 and then changes to a value that follows the movement.

[0169] On the other hand, when both compliance control and speed increase control are executed, each time the bed 10 is determined to be pushed, the assist rotation speed rises steeply (for example, refer to t = t1, t2, t3). On the other hand, if the period during which it is determined that the bed 10 is not being pushed continues, the assist rotation speed after rising will gradually decrease over time (for example, refer to t1 < t < t2, t2 < t < t3).

[0170] Then, when the processing in step S36 is completed, the control process ends the flows in FIGS. 10 and 15 and proceeds to step S7 in FIG.

[0171] The explanation regarding Fig. 15 also applies to the case where the process proceeds from step S12 to the flow of Fig. 15. In that case, in the above explanation, the word "vertical" should be replaced with the word "horizontal" and the word "front-rear" should be replaced with the word "left-right." The same applies to various mathematical expressions. In this case, the predetermined values ​​such as the fourth threshold T4 may be the same or different in the front-rear direction and the left-right direction.

[0172] On the other hand, when the process proceeds from step S13 to step S15, the controller 4 sets the assist rotation speeds in both the longitudinal and lateral directions for cornering in order to assist the bed 10 in cornering.

[0173] Here, steps S41 to S44 in Fig. 16 respectively exemplify the processing executed in step S15 in Fig. 10. That is, when the control process proceeds to step S15, the controller 4 Figure 16 Each step is executed in order starting from step S41.

[0174] First, in step S41, the controller 4 calculates the lateral acceleration a estimated in step S3 of FIG. y is adjusted to decrease at a predetermined rate greater than 0. Specifically, the controller 4 adjusts the vertical acceleration a x The value estimated in step S3 is maintained for the lateral acceleration a y is converted as shown in the following equation (18).

[0175] a y '=c y *a y …(18) In the above equation (18), c indicates a predetermined ratio y is set in advance according to the dimensions, weight, configuration, etc. of the bed 10 and the transport auxiliary device 1, and is stored in the controller 4. y is less than 1 (0 <cy <1, and more specifically, less than 0.5 (0 <c y <0.5).

[0176] This predetermined ratio c y is set so as to shift the rotation center Ot of the bed 10 from the center position Pc of the first and second Mecanum wheels 21R, 21L toward the front end of the bed 10 (see FIG. 17).

[0177] The central position Pc here may be the central position of the first and second Mecanum wheels 21R, 21L in the left-right direction, as shown in FIG. 4, and may be the position where the first and second rotation axes Oy1, Oy2 intersect in the front-rear direction.

[0178] In the next step S42, the controller 4 calculates the longitudinal acceleration a estimated in step S3 in the longitudinal direction. x Based on this, compliance control is executed as the first control.

[0179] In particular, the controller 4 according to this embodiment uses the longitudinal acceleration a estimated in step S3 in the longitudinal direction. x Based on this, both the compliance control and the speed increase control as the second control are executed in sequence. Details of the compliance control and the speed increase control in the longitudinal direction are as described with reference to Fig. 15. By executing step S42, the controller 4 sets the speed command in the longitudinal direction as described above.

[0180] In other words, in the forward and backward directions, a speed command (and thus the command rotation speeds of the first and second motors 22R, 22L) is calculated to follow the forward and backward movement of the bed 10, and control is executed to raise the speed command (command rotation speeds) in synchronization with the bed 10 being pushed.

[0181] In the next step S43, the controller 4 calculates the lateral acceleration a in the left-right direction (lateral direction) after adjustment in step S41. yBased on this, compliance control is performed as the first control.

[0182] In particular, the controller 4 according to this embodiment adjusts the lateral acceleration a y ', and then the speed increase control as the second control is not executed. In this case, the controller 4 executes the processes other than steps S32 to S35 in FIG. 15, and sets the speed command in the left and right direction.

[0183] In other words, in the left-right direction, control is executed to calculate a speed command (and thus the command rotation speed of the first and second motors 22R, 22L) that slightly follows the lateral movement of the bed 10, but control to raise the speed command (command rotation speed) in synchronization with the bed 10 being pushed is intentionally not executed.

[0184] In the following step S44, the controller 4 sets the speed command set in step S42 as the assist speed in the longitudinal direction, and sets the command rotation speed set in step S43 as the assist speed in the lateral direction.

[0185] When the flow relating to step S12, step S14, and step S15 in Fig. 10 is completed, the control process proceeds to step S7 in Fig. 9. In this step S7, the controller 4 adjusts the longitudinal speed command V x or lateral speed command V y The first command rotation speed R is calculated using the following equations (19) and (20), which are defined in the same way as the above equations (5) and (6). r and the second command speed R l Convert to and.

[0186] R r =60*(V x +V y ) / (2π·R) …(19) R l =60*(V x -V y ) / (2π·R) …(20) In the above equations (19) and (20), "R" is the tire radius. In this embodiment, when assisting in the longitudinal direction, V x ≠0 and V y = 0, and when assisting left and right, V x =0 and V y ≠0, and when assisting cornering, V x ≠0 and V y ≠0.

[0187] For example, when the controller 4 determines that the moving direction of the bed 10 is the forward / backward direction (when the process has gone through step S14), the controller 4 controls the first and second command rotation speeds R so that both the first and second Mecanum wheels 21R and 21L rotate forward or backward, as illustrated in the upper left and upper right of FIG. r ,R l In addition, when setting, the absolute values ​​of the command rotation speeds of the first Mecanum wheel 21R and the second Mecanum wheel 21L are made equal (R r =R l ).

[0188] First and second command rotation speeds R r ,R l By making the absolute values ​​of equal, movement along the front-to-rear direction can be stabilized regardless of the orientation of each caster 14.

[0189] Furthermore, when the controller 4 determines that the moving direction of the bed 10 is the left-right direction (when the process has gone through step S12), it controls the first and second command rotation speeds R to rotate one of the first and second Mecanum wheels 21R, 21L forward and the other backward, as illustrated in the lower left of FIG. r ,R l In addition, when setting the rotation speed, the absolute values ​​of the command rotation speeds of the first Mecanum wheel 21R and the second Mecanum wheel 21L are set to be equal (R r =-R l ).

[0190] Furthermore, when the controller 4 determines that the bed 10 is cornering (when the process has gone through step S12), it controls the first and second command rotation speeds R to rotate at least one of the first and second Mecanum wheels 21R and 21L, as illustrated in the lower right of FIG. r ,R l In this setting, the absolute values ​​are set differently for the first Mecanum wheel 21R and the second Mecanum wheel 21L (|R r |≠|R l |).

[0191] Thereafter, in step S8 following step S7, the controller 4 executes safety control processing. Details of this processing are as shown in steps S51 and S52 in FIG.

[0192] First, in step S51, the controller 4 calculates the command rotation speed R set through the flow of FIG. r ,R l is equal to or greater than a predetermined fifth threshold T5. Here, the magnitude of the fifth threshold T5 is stored in advance in the memory of the controller 4, and is read out as needed.

[0193] If the determination in step S51 is YES, the controller 4 advances the control process to step S52. In step S52, the controller 4 calculates each command rotation speed R r ,R l is changed to the fifth threshold T5.

[0194] On the other hand, if the determination in step S51 is NO, the controller 4 skips step S52 and returns. r ,R l The magnitude of remains below the fifth threshold T5.

[0195] In this way, the controller 4 according to this embodiment controls the first and second command rotational speeds R after the speed increase control as the second control. r,R l is less than the predetermined threshold value (fifth threshold value T5) (step S51: NO), the first and second command rotation speeds R r ,R l and maintain the value of the first and second command speeds R r ,R l is equal to or greater than the fifth threshold T5 (step S51: YES), the first and second command rotation speeds R r ,R l to a fifth threshold T5.

[0196] 9, the controller 4 drives the first and second Mecanum wheels 21R and 21L via the first and second motors 22R and 22L, respectively, to assist the movement of the bed 10 along the movement direction. At this time, the command rotation speed R determined through the above-mentioned steps S5, S6, and S7 is used. r ,R l The first and second motors 22R and 22L are driven so as to realize the above.

[0197] As a result, when the bed 10 is pushed forward or backward or left and right, assistance is provided in the direction of movement, while when the bed 10 is turning while moving forward or backward, that is, when the bed 10 is cornering, the first and second Mecanum wheels 21R, 21L are driven via the first and second motors 22R, 22L so that the hand-pushing movement is assisted in both the forward and backward directions and the left and right directions.

[0198] As a result, instead of turning around the center position Pc as in the case of assistance only in the longitudinal direction, turning is achieved while sliding the bed 10 sideways. For example, when turning right as shown in Fig. 17, in addition to an external force that pushes the bed 10 forward, an external force that slides the bed 10 to the left (the opposite direction to the turning direction) acts, so by feeding back and assisting this external force, cornering that slides the bed 10 to the left (a drift, so to speak) is achieved.

[0199] This allows cornering with the turning center Ot shifted toward the front end of the bed 10 as shown in FIG. 17, making it possible to turn the bed 10 along a trajectory as shown in the same figure.

[0200] If lateral assistance were not provided, the bed 10 would follow a trajectory with the center of rotation Ot at the center position Pc of the first and second Mecanum wheels 21R, 21L, as shown in the conventional example in Figure 19. This trajectory has a small cornering radius, which is inconvenient as it may cause interference between the bed 10 and corners of the aisle, etc.

[0201] Furthermore, although not shown, when turning left, in addition to an external force that pushes the bed 10 forward, an external force that slides the bed 10 to the right (the opposite direction to the turning direction) acts, and by feeding back and assisting this external force, cornering that slides the bed 10 to the right is realized. In this case as well, it is possible to achieve a smooth trajectory as shown in Figure 17.

[0202] As described above, according to this embodiment, the controller 4 assists manual push movement not only in the forward and backward directions but also in the lateral directions (see steps S43 and S44 in FIG. 16). When cornering the bed 10, it is thought that force is also applied in the radial direction of the cornering, i.e., in the lateral direction of the bed. Therefore, by assisting with such lateral force, the bed 10 can slide laterally when cornering. This increases the cornering radius and reduces interference between the front or rear end of the bed 10 and the corners of the aisle. This makes it possible to appropriately assist the bed 10 in cornering.

[0203] 9, by detecting the induced current, it is possible to estimate the torque that caused the induced current (torque that tends to rotate the first and second Mecanum wheels 21R, 21L), and therefore the acceleration corresponding to that torque. By estimating the acceleration of each Mecanum wheel 21R, 21L, it is possible to estimate the direction in which the external force is acting.

[0204] Then, assistance is provided in the forward and backward directions to allow the bed 10 to follow the manual pushing movement, while in the lateral direction, as illustrated in step S41 of FIG. 16, the acceleration in that direction is reduced and compliance control is performed based on the acceleration. Reducing the acceleration in the lateral direction is equivalent to estimating the external force acting in that direction to be smaller than the external force that actually acts. By underestimating the external force, assistance is provided in the lateral direction that is not sufficient to allow the bed 10 to follow the manual pushing movement. As a result, excessive sliding in the lateral direction (sliding more than intended by the transporter 100) is suppressed, and the cornering radius can be kept within an appropriate range. This is advantageous in providing appropriate assistance for cornering of the bed 10.

[0205] Also, as explained using Figure 17, by shifting the turning center Ot of the bed 10 toward the front end, it is possible to realize an operation in which the rear end side turns more than the front end side when cornering the bed 10. By turning the rear end side more, it is possible to suppress interference between the rear end part and the corner of the passage. This is advantageous in appropriately assisting the cornering of the bed 10.

[0206] Furthermore, as illustrated in step S42 of FIG. 16, by performing speed increase control in the forward / backward direction, the bed 10 not only follows the manual push movement but also reduces the load on the person 100 by the amount of the increased commanded rotation speed. This improves the comfort of pushing the bed 10 in the forward / backward direction, and provides the person 100 with an appropriate "assistance feeling." On the other hand, as illustrated in step S43 of FIG. 16, the speed increase control is intentionally not performed in the lateral direction. This prevents excessive sliding in the lateral direction (sliding more than intended by the person 100) and keeps the cornering radius within an appropriate range. This is advantageous in providing appropriate assistance to the cornering of the bed 10.

[0207] Furthermore, by configuring and arranging the first and second Mecanum wheels 21R, 21L as shown in Figures 3 to 5 and 7, when the first Mecanum wheel 21R and the second Mecanum wheel 21L are rotated in opposite directions, a thrust can be generated that causes the bed 10 to turn. This configuration is effective in appropriately assisting the bed 10 in cornering.

[0208] Furthermore, by making the absolute value of the command rotation speed equal during forward and backward movement, more stable forward and backward movement can be achieved regardless of the orientation of the caster 14. On the other hand, by intentionally making the absolute value different during cornering, cornering along a desired trajectory can be achieved.

[0209] <Other embodiments> In the above embodiment, the first and second current sensors SW1 and SW2 are used as status sensors for determining whether the bed 10 is moving forward or backward, but the present disclosure is not limited to such a configuration. For example, the first and second rotation sensors SW3 and SW4 or the six-axis sensor SW5 may be used as the status sensors.

[0210] Furthermore, in the above embodiment, the speed command (translation speed command value) is increased by the speed increase control, but such a configuration is not essential.

[0211] For example, in steps S32 to S34, a process for increasing the command rotation speed may be executed instead of the process related to the speed command. In this case, a process for converting the speed command into the command rotation speed is provided between steps S31 and S32. [Explanation of symbols]

[0212] 1. Transport auxiliary equipment 4 Controller 10 beds (castor beds) 14 Caster 14F front wheel 14B rear wheel 21R 1st Mecanum Wheel 211R 1st wheel body (wheel body) 212R No. 1 barrel roller (barrel roller) 21L 2nd Mecanum Wheel 211L Second wheel body (wheel body) 212L No. 2 barrel roller (barrel roller) 22R 1st motor 22L Second motor c y Predetermined ratio F Conveying surface Ot turning center PC center position Oy1 First rotation axis (rotation axis) Oy2 Second rotation axis (rotation axis) Or 1st tilt axis (tilt axis) Ol 2nd tilt axis (tilt axis) SW1 First current sensor (status sensor) SW2 Second current sensor (status sensor) SW5 6-axis sensor (rotation sensor)

Claims

1. A transport assist device for assisting manual movement of a bed with casters, First and second Mecanum wheels attached to a lower portion of the bed and in contact with a conveying surface of the bed; first and second motors drivingly connected to the first and second Mecanum wheels, respectively; a state sensor that detects a signal corresponding to the rotation state of the first and second Mecanum wheels; a rotation sensor that detects rotation of the bed around a rotation axis perpendicular to the conveying surface; a controller that controls the first and second motors, The state sensor includes first and second current sensors that detect induced currents flowing through the first and second motors when the first and second Mecanum wheels rotate, respectively; The controller determines whether the bed is moving forward or backward and whether the bed is turning based on the detection signals of the state sensor and the turning sensor, The controller When it is determined that the bed is moving forward or backward and not rotating, the first and second Mecanum wheels are driven via the first and second motors so as to assist the manual movement in the forward and backward directions; When it is determined that the bed is rotating while moving forward or backward, the first and second Mecanum wheels are driven via the first and second motors so as to assist the manual movement in both the front-to-rear direction and a lateral direction perpendicular to the front-to-rear direction and extending along the conveying surface, The controller further comprises: Based on the detection signals of the first and second current sensors, a longitudinal acceleration indicating the acceleration of the first and second Mecanum wheels in the longitudinal direction and a lateral acceleration indicating the acceleration of the first and second Mecanum wheels in the lateral direction are estimated, respectively; executes a first control for setting command rotation speeds of the first and second motors so as to follow the hand-pushing movement based on at least one of the vertical acceleration and the lateral acceleration; When the controller determines that the bed is rotating while moving forward or backward, With respect to the longitudinal direction, the first control is executed based on the longitudinal acceleration, With respect to the lateral direction, the lateral acceleration is adjusted so as to be reduced at a predetermined rate exceeding 0, and the first control is executed based on the adjusted lateral acceleration. A transport auxiliary device characterized by:

2. 2. The transport assist device according to claim 1, The predetermined ratio is set so as to shift the rotation center of the bed from the center position of the first and second Mecanum wheels toward the front end of the bed. A transport auxiliary device characterized by:

3. 2. The transport assist device according to claim 1, When the controller determines that the bed is moving forward or backward and not turning, the controller executes the first control based on the vertical acceleration and executes the second control of increasing the command rotation speed, When the controller determines that the bed is rotating while moving forward or backward, With respect to the longitudinal direction, the first control and the second control are executed in sequence based on the longitudinal acceleration; With respect to the lateral direction, the first control is executed based on the adjusted lateral acceleration, and the second control is not executed. A transport auxiliary device characterized by:

4. A transport assist device for assisting manual movement of a bed with casters, comprising: First and second Mecanum wheels attached to a lower portion of the bed and in contact with a conveying surface of the bed; first and second motors drivingly connected to the first and second Mecanum wheels, respectively; a state sensor that detects a signal corresponding to the rotation state of the first and second Mecanum wheels; a rotation sensor that detects rotation of the bed around a rotation axis perpendicular to the conveying surface; a controller that controls the first and second motors, The controller When it is determined that the bed is moving forward or backward and not rotating, the first and second Mecanum wheels are driven via the first and second motors so as to assist the manual movement in the forward and backward directions; When it is determined that the bed is rotating while moving forward or backward, the first and second Mecanum wheels are driven via the first and second motors so as to assist the manual movement in both the front-to-rear direction and a lateral direction perpendicular to the front-to-rear direction and extending along the conveying surface, The first and second Mecanum wheels are arranged side by side in the lateral direction, The first and second Mecanum wheels each include: a wheel body that rotates about a rotation axis extending in the lateral direction; a plurality of barrel-shaped rollers arranged along the outer periphery of the wheel body, each of which rotates around an inclined axis inclined with respect to both the longitudinal direction and the lateral direction; The tilt axis of the first Mecanum wheel is tilted so as to be line-symmetrical with respect to the tilt axis of the second Mecanum wheel with respect to the front-rear direction, The controller determines whether the bed is moving forward or backward and whether the bed is turning based on the detection signals of the state sensor and the turning sensor, The controller further comprises: When it is determined that the bed is moving forward or backward and not rotating, a command rotation speed is set so that both the first and second Mecanum wheels are rotated forward or backward, and in this setting, the absolute values ​​of the command rotation speeds of the first Mecanum wheel and the second Mecanum wheel are made equal; When it is determined that the bed is rotating while moving forward or backward, the command rotation speed is set so that the absolute values ​​of the first Mecanum wheel and the second Mecanum wheel are different. A transport auxiliary device characterized by:

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