JP7805328B2 - Transport Auxiliary Equipment - Google Patents

Description

This disclosure relates to a transport assistance device.

For example, Patent Document 1 discloses an auxiliary propulsion system that uses Mecanum wheels in the drive section. 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 rotational speed of each motor.

According to Patent Document 1, when the chassis moves in a specific direction, the operator applies a force in the same direction. When the applied force causes each Mecanum wheel to rotate, the resulting change in rotation speed is reported to the control system. Based on this report, the control system initiates the electric rotation of the motor. This electric rotation assists the movement of the chassis.

Special Publication No. 2016-525977

Now, consider a situation where the configuration described in Patent Document 1 is applied to a bed with casters and the bed is being cornered. In this case, the bed will be pushed forward and backward while turning, so it would be possible to assist the bed in the forward and backward directions.

However, after extensive research, the inventors realized that simply providing assistance in the fore-and-aft direction when 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 when it comes to cornering assistance.

The technology disclosed here was developed in light of these issues, and its purpose is to provide appropriate assistance for cornering of caster-equipped beds.

A first aspect of the present disclosure relates to a transport assist device for assisting manual pushing of a caster-equipped bed. This transport assist device comprises first and second Mecanum wheels attached to the underside of the bed and in contact with the bed's transport surface, first and second motors drivingly connected to the first and second Mecanum wheels, respectively, a status sensor that detects signals corresponding to the rotational 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 rotating. If the controller determines that the bed is moving forward or backward but not rotating, it drives the first and second Mecanum wheels via the first and second motors to assist the manual movement in the forward and backward direction. On the other hand, if the controller determines that the bed is rotating while moving forward or backward, it drives the first and second Mecanum wheels via the first and second motors to assist the manual movement in both the forward and backward direction and a lateral direction perpendicular to the forward and backward direction and extending along the conveying surface.

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 corner, i.e., in the lateral direction of the bed. Therefore, by assisting with this lateral force, the bed can be slid laterally when cornering. This increases the cornering radius and reduces interference between the front or rear end of the bed and the corners of the aisle. This makes it possible to appropriately assist cornering of a caster-equipped bed.

Furthermore, 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 through the first and second motors as the first and second Mecanum wheels rotate, respectively. The controller may estimate a vertical acceleration indicating the acceleration of the first and second Mecanum wheels in the fore-and-aft 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 execute first control to set command rotation speeds for 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 rotating while moving forward or backward, it may execute the first control based on the vertical acceleration for the fore-and-aft direction, while adjusting the lateral acceleration for the lateral direction so that it decreases by a predetermined ratio greater than zero, and execute the first control based on the adjusted lateral acceleration.

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 ultimately 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.

The system then provides assistance in the forward and backward directions to allow the bed to follow the manual push movement, while reducing the acceleration in the lateral direction and performing a first control based on that acceleration. Reducing the acceleration in the lateral direction is equivalent to underestimating the external force acting in that direction compared to the actual external force. 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.

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.

According to the third aspect, by shifting the bed's swivel center 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 swiveling 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 when cornering a caster-equipped bed.

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 may execute the first control based on the longitudinal acceleration and execute the second control to increase the command rotation speed; and when the controller determines that the bed is rotating while moving forward or backward, it may execute the first control and the second control in sequence based on the longitudinal acceleration for the forward-backward direction, and execute the first control based on the adjusted lateral acceleration for the lateral direction, and not execute the second control.

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, providing the carrier with an appropriate "sense of assistance." On the other hand, the second control is intentionally not performed in the lateral direction. This prevents excessive sliding in the lateral direction (sliding more than the carrier intended) and keeps the cornering radius within an appropriate range. This is advantageous for appropriately assisting the cornering of a caster-equipped bed.

Furthermore, 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 having a wheel body that rotates around a rotation axis extending in the horizontal direction, and a plurality of barrel-shaped rollers arranged along the outer periphery of the wheel body, each rotating around an inclined axis 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 symmetrically with respect to the inclined axis of the second Mecanum wheel with respect to the front-to-rear direction.

By configuring it as in the fifth aspect, when the first Mecanum wheel and the second Mecanum wheel are rotated in opposite directions, a thrust force can be generated that causes the bed to turn. This configuration is effective in appropriately assisting the cornering of a caster-equipped bed.

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 the command rotation speeds for both the first and second Mecanum wheels so that they rotate forward or backward, and when setting the command rotation speeds, it may set the absolute values of the command rotation speeds 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 speeds for the first Mecanum wheel and the second Mecanum wheel to have different absolute values.

According to the sixth aspect, by making the absolute value of the commanded 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 the desired trajectory can be achieved.

As described above, the present disclosure can provide appropriate assistance for cornering of a caster-equipped bed.

1 is a side view illustrating an example of the overall configuration of a transport assist device and a bed with casters. FIG. 1 is a bottom view illustrating an example of the overall configuration of a transport assist device and a bed with casters. FIG. FIG. 2 is a perspective view illustrating the configuration of a transport assist device. FIG. 2 is a plan view illustrating the configuration of a transport assist device. FIG. 2 is a side view illustrating the configuration of a transport assist device. FIG. 2 is a block diagram illustrating the configuration of a control system of the transport assist device. 10A and 10B are diagrams for explaining the operation of the first and second Mecanum wheels. FIG. 2 is a diagram for explaining a detection target of a six-axis sensor. 4 is a flowchart illustrating main processing performed by a controller. 10 is a flowchart illustrating a process related to determination of a movement direction. FIG. 2 is a control block diagram illustrating a configuration of compliance control. FIG. 1 is a conceptual diagram for explaining the basic concept of compliance control. FIG. 10 is a diagram illustrating an example of a change in speed increase amount relative to the rotation speed. FIG. 10 is a diagram illustrating an example of a command rotation speed obtained by speed increase control. 10 is a flowchart illustrating compliance control and speed increase control. 10 is a flowchart illustrating a control relating to cornering. FIG. 10 is a diagram illustrating an example of a trajectory of a bed during cornering. 10 is a flowchart illustrating a safety limit control. FIG. 17 is a diagram corresponding to FIG. 17 and shows a conventional example of a bed trajectory.

Embodiments of the present disclosure will be described below with reference to the drawings.

Figure 1 is a side view illustrating the overall configuration of the transport assistance device 1 and caster bed 10, and Figure 2 is a bottom view illustrating the overall configuration of the transport assistance device 1 and caster bed 10.

Furthermore, Figure 3 is a perspective view illustrating the configuration of the transport assistance device 1, Figure 4 is a plan view illustrating the configuration of the transport assistance device 1, and Figure 5 is a side view illustrating the configuration of the transport assistance device 1.

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

As shown in Figures 1 and 2, the 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 multiple casters 14, including front wheels 14F and rear wheels 14B, and is intended for use, for example, as a medical bed. The transport assistance device 1 is a device that assists in manually moving such a bed 10.

Hereinafter, the longitudinal direction of the bed 10, i.e., the direction in which a person lies on the 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."

Similarly, the shorter direction of the bed 10, that is, the direction perpendicular to the front-to-rear direction on a horizontal plane, is referred to 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 Figure 1 is referred to as the "right," and the direction along the front of the paper in Figure 1 is referred to as the "left" (see Figure 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-rear direction and extending along the transport surface F (the floor surface along which the bed 10 travels).

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 assistance device 1 operates to assist the carrier 100 in manually pushing and moving the bed 10.

As shown in FIG. 1, the bed 10 comprises 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 multiple 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.

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

Of these, the headboard 11h is supported from the rear by the carrier 100 when manually pushing the bed 10. The headboard 11h functions as a support part to which the carrier 100 applies force. By attaching handles, grips, or other components to the headboard 11h or integrating them with the headboard 11h, these components may also serve as a support part. The footboard 11f, side rails 11s, etc. may also be supported.

As shown in Figure 2, the frame 12 is rectangular, with its four sides made up of a front frame 12F, a right frame 12R, a left frame 12L, and a rear frame 12B.

Here, the front frame 12F is located at the front of the bed 10 and extends in the left-right direction. The right frame 12R is located on the right side of the bed 10 and extends in the front-to-back direction. The left frame 12L is located on the left side of the bed 10 and extends in the front-to-back direction. The rear frame 12B is located at the rear of the bed 10 and extends in the left-to-right direction.

As shown in Figures 1 and 2, the front wheels 14F and rear wheels 14B that make up the multiple casters 14 are located 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 multiple casters 14 support the frame 12, lifting section 13, and bed body 11 relative to the transport surface F.

Each caster 14 is a so-called free caster and has an attachment part 14a fixed to the underside of the bed 10, a fork part 14b that can rotate around a rotation axis Oc relative to the attachment part 14a, and a wheel 14c that is rotatably supported by the fork part 14b. The rotation axis Oc of each fork part 14b extends in the vertical direction (the height direction of the bed 10). The rotation axis of each wheel 14c extends along the horizontal plane. This rotation axis can be tilted left and right as the fork part 14b rotates relative to the attachment part 14a.

The transport assistance device 1 is positioned so as to bridge the midpoint of the right frame 12R in the fore-and-aft direction and the midpoint of the left frame L in the fore-and-aft direction. The transport assistance device 1 is positioned between the front wheels 14F and rear wheels 14B in the fore-and-aft direction, and in the center of the bed 10 in the left-and-right direction.

As shown in Figures 1 to 6, the transport assistance device 1 includes a storage box 6, a mounting 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 sensors SW1-SW5 are only shown in Figure 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.

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

As described above, the storage box 6 houses the controller 4. The storage box 6 is positioned between the first Mecanum wheel 21R and the second Mecanum wheel 21L in the left-right direction.

The storage box 6, together with the first and second Mecanum wheels 21R, 21L, is attached to the mounting fixture 7, which is then attached to the bottom of the bed 10 via the mounting fixture 7. The mounting 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 removed as needed.

More specifically, as shown in Figures 2 to 5, the mounting fixture 7 according to this embodiment includes 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.

Here, 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.

On the other hand, the first arm member 72R, located on the right side in Figures 3 and 4, 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. Furthermore, the first arm member 72R is positioned between the first Mecanum wheel 21R and the storage box 6 in the left-right direction.

In addition, one end of a first tension spring 75R is attached to the upper end of the first arm member 72R. The other end of this first tension spring 75R is attached to a first bracket 76R fixed to the front rail member 71f.

The second arm member 72L, located on the left side in Figures 3 and 4, is supported by the rear rail member 71b so that it can swing, just like 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.

In addition, one end of a second tension spring 75L is attached to the upper end of the second arm member 72L. The other end of this second tension spring 75L is attached to a second bracket 76L fixed to the front rail member 71f (see also Figure 5).

As shown in Figures 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 Figure 1. The first and second Mecanum wheels 21R, 21L are also positioned behind the front wheels 14F and in front of the rear wheels 14B. In this embodiment, the first and second Mecanum wheels 21R, 21L are aligned in the left-right direction, which is the short side direction, as shown in Figure 2.

More specifically, 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 rotate around a first inclined axis Or that is inclined relative to the first rotation axis Oy1.

On the other hand, the second Mecanum wheel 21L has a second wheel body 211L that rotates around a second rotation axis Oy2, and multiple 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.

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

Furthermore, when viewed from above (in a plan view) as shown in Figure 4, the first and second tilt axes Or and Ol each extend from the rear to the front along the front-to-rear direction, and from the inside to the outside in the left-to-right direction (from the center in the left-to-right direction to the right or left).

Specifically, the first tilt axis Or extends from the center in the left-right direction toward the right as it moves from the rear to the front along the front-to-rear direction. On the other hand, the second tilt axis Ol extends from the center in the left-right direction toward the left as it moves from the rear to the front along the front-to-rear direction.

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 transport assist device 1 may be repositioned from the state illustrated in Figure 2 to a state rotated a predetermined angle around the z-axis extending in the vertical direction.

As mentioned above, the first and second Mecanum wheels 21R, 21L are interconnected via the front rail member 71f and rear rail member 71b shown in Figure 3, etc. Therefore, the first and second Mecanum wheels 21R, 21L move integrally in the front-to-rear and left-to-right directions, and rotate integrally around a pivot axis perpendicular to the horizontal plane.

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 this controller 4.

When the first and second motors 22R, 22L rotate, a motor current corresponding to the torque load is supplied. The motor current can be used to switch the rotation speed of the first and second motors 22R, 22L and their forward and reverse rotation.

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

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

In this embodiment, the first Mecanum wheel 21R is configured to rotate forward when the first motor 22R is rotated in the forward direction, and the first Mecanum wheel 21R is configured to rotate backward when the first motor 22R is rotated in the reverse direction. Similarly, in this embodiment, the second Mecanum wheel 21L is configured to rotate forward when the second motor 22L is rotated in the forward direction, and the second Mecanum wheel 21L is configured to rotate backward when the second motor 22L is rotated in the reverse direction.

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 in this way, the entire transport assist device 1 can be simplified and made more compact.

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

Specifically, the first current sensor SW1 detects the induced current flowing through the first motor 22R when the first Mecanum wheel 21R rotates. In other words, 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.

Here, the magnitude of the induced current is proportional to the torque acting on the first Mecanum wheel 21R when it rotates in response 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 to 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 it rotates in response to an external force. The sign of the induced current is opposite to the motor current that flows when the first motor 22R is driven.

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.

Here, the magnitude of the induced current is proportional to the torque acting on the second Mecanum wheel 21L when it rotates in response 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 to 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 it rotates in response to an external force. The sign of the induced current is opposite to the motor current that flows when the second motor 22L is driven.

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. 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.

As described in detail below, the controller 4 according to this embodiment is configured to provide assistance in the forward direction, i.e., 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).

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, in this embodiment, the first and second rotation sensors SW3 and SW4 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.

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

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 forward/backward direction, the y-axis extending in the left/right direction, and the z-axis extending in the up/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.

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

Specifically, the controller 4 according to this embodiment sets the command rotation speeds for 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 each rotate at the command rotation speeds set by the controller 4.

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 for the first and second motors 22R and 22L is equivalent to setting the command rotation speeds for the first and second Mecanum wheels 21R and 21L.

In addition, 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 and backward rotation.

In this embodiment, when the first Mecanum wheel 21R located on the right side is rotated forward, a thrust force can be applied diagonally forward to the left to the transport assistance device 1 and the bed 10 (see arrow _A11 in FIG. 7). On the other hand, when the second Mecanum wheel 21L located on the left side is rotated forward, the transport assistance device 1 can apply a thrust force diagonally forward to the right to the bed 10 (see arrow _A12 in FIG. 7).

Therefore, for example, as shown in the upper left of Figure 7, 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 the transport assistance device 1 as a whole can apply a forward thrust. This thrust can assist the forward movement of the bed 10.

Similarly, when the first Mecanum wheel 21R located on the right side is rotated backward, a thrust force can be applied to the transport assist device 1 and the bed 10 in a diagonally rearward right direction (see arrow _A21 in FIG. 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 in a diagonally rearward left direction (see arrow _A22 in FIG. 7).

Therefore, for example, as shown in the upper right of Figure 7, 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 the transport assistance device 1 as a whole can apply a backward thrust. This thrust can assist in the backward movement of the bed 10.

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 assistance device 1 applies a thrust force in the left-right direction to the bed 10.

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

Furthermore, when only one of the first and second Mecanum wheels 21R, 21L is rotated forward or backward, the transport assistance device 1 applies a diagonal thrust to the bed 10.

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).

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

To achieve this assistance, the controller 4 according to this embodiment determines the direction in which the external force is acting (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 that direction of action.

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. This makes it possible to assist the bed 10 in moving forward, as shown in the upper left of Figure 7.

In addition, 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. This reduces wobbling when the bed 10 is pushed by hand, allowing for stable transport of the bed 10.

The assistance provided by the controller 4 will be explained in detail below, using Figure 9 and other figures.

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

Furthermore, Figure 16 is a flowchart illustrating cornering control. Figure 17 is a diagram illustrating the trajectory of the bed 10 when cornering. Figure 18 is a flowchart illustrating safety limit control.

First, in step S1 of Figure 9, the controller 4 reads the detection signals from the five sensors SW1 to SW5 mentioned above.

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

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, i.e., so-called tangential accelerations.

The magnitude of the induced current detected by 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 separately 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, the proportionality coefficient used to convert the induced current to torque can be a value previously stored in the controller 4.

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

To achieve this assistance, 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):

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, a _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.

In addition, 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.

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.

In detail, the controller 4 uses the first and second accelerations a _r and a _l estimated based on the detection signals of the first and second current sensors SW1 and SW2 to estimate a vertical acceleration indicating the translational acceleration of the first and second mecanum wheels 21R and 21L in the front-to-rear direction and a lateral acceleration indicating the translational acceleration of the first and second mecanum wheels 21R and 21L in the lateral direction, respectively.

More specifically, when the first and second Mecanum wheels 21R, 21L are configured as shown in Figures 3 to 5, the controller 4 estimates the vertical acceleration by adding the first acceleration a _r and the second acceleration a ₁ , and estimates the lateral acceleration by calculating the difference between the first acceleration a _r and the second acceleration a _1. Details of these calculations are shown in the following equations (3) and (4).

a _x = (a _r + a _l )/2...(3)
a _y = (a _r - _{a l} )/2...(4)
In the above equations (3) and (4), a _x [m/s ² ] is the longitudinal acceleration, and a _y [m/s ² ] is the lateral acceleration. The sign of equation (3) is defined so that the front is positive and the rear is negative. The sign may be reversed between the front and rear. Similarly, the sign of equation (4) is defined so that the left is positive and the right is negative. The sign may be reversed between the left and right.

Note that the relationship between equations (3) and (4) also holds true for the rotation speeds of the first and second motors 22R and 22L (i.e., the rotation speeds of the first and second Mecanum wheels 21R and 21L).

Here, r _r [rpm] is the rotation speed of the first motor 22R in the front-rear direction (hereinafter also referred to as the "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"). Of these rotation speeds, the first rotation speed r _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.

Let r _x [rpm] be the total rotation speed of the first and second motors 22R, 22L in the front-to-rear direction (hereinafter also referred to as the "vertical rotation speed"), and let _ry [rpm] be the total rotation speed of the first and second motors 22R, 22L in the left-to-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.

r _x = (r _r + r _l )/2...(5)
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), by setting _rx and _ry , _rr and _rl can be uniquely determined.

r _r = r _x + r _y …(7)
r _l = r _x - _r y (8)
Furthermore, by multiplying both sides of each of the above equations (7) and (8) by a constant (=πR/30) that depends on the tire radius R, pi, etc., a similar relationship can be obtained for the speed. That is, let _vr [m/s] be the speed of the first Mecanum wheel 21R in the longitudinal direction, and _vl [m/s] be the speed of the second Mecanum wheel 21L in the longitudinal direction. Then, let _vx [m/s] be 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 _vy [m/s] be the overall speed of the first and second Mecanum wheels 21R, 21L in the lateral 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 true.

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

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), by setting _vx and _{vy, vr and vl can be} uniquely set.

v _r = v _x + v _y (11)
v _l = v _x − _v y (12)
Furthermore, by utilizing the relationship between the equations, for example, when command values for the longitudinal speed _vx and/or the lateral speed _vy are determined, it is possible to uniquely determine the longitudinal rotation speed _rr and the lateral rotation speed _rl required to realize these command values, or to determine the first rotation speed _rr and the second rotation speed _rl corresponding to the longitudinal rotation speed _rr and/or the lateral rotation speed _rl .

Next, the controller 4 allows the first and second Mecanum wheels 21R, 21L to be driven, provided that the rotation speed of the first and second Mecanum wheels 21R, 21L reaches or exceeds a predetermined value (first threshold) based on the detection signals of the first and second rotation sensors SW3, SW4.

Specifically, in step S4, which follows step S3, the controller 4 determines whether either one of the following relational expressions (13) and (14) is satisfied. Through this determination, it is possible to confirm whether the bed 10 is actually being transported (whether the bed 10 is actually moving).

r _x ≧T1 (13)
r _y ≧T1 (14)
In the above formulas (13) and (14), T1 [1/s] is a first threshold value. The magnitude of the first threshold value is stored in advance in the memory of the controller 4 or the like, and is set to be equal in the above formulas (13) and (14).

Here, if both of the above equations (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.

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

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 step S6, the controller 4 sets command rotation speeds (assist rotation speeds) for the first and second motors 22R and 22L to assist the manual movement caused by the external force. These assist rotation speeds correspond to the command values for the vertical rotation speed _rx and the horizontal rotation speed _ry described above.

Steps S11 to S15 in Figure 10 each illustrate the processing executed in step S6 in Figure 9. In other words, when the control process proceeds to step S6, the controller 4 starts step S11 in Figure 10.

In step S11, the controller 4 determines the movement direction of the bed 10 based on the vertical acceleration _ax and lateral acceleration _ay estimated in step S3 of Fig. 9. In detail, the controller 4 according to this embodiment determines whether the movement direction of the bed 10 is the front-to-rear direction (whether the bed 10 is moving forward or backward) or the left-to-right direction based on the vertical acceleration _ax and lateral acceleration _ay .

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

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

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.

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 forward/backward direction, and proceeds to step S13 (step S11: YES).

In step S13, the controller 4 determines whether the bed 10 is rotating around the z-axis shown in Figure 8 based on the detection signal of the six-axis sensor SW5. More specifically, in step S13, the controller 4 determines whether the following relational expression (16) is satisfied:

｜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 value. The magnitude of the third threshold value is stored in advance in the memory of the controller 4, and is read out as needed.

Here, if the above formula (16) is not satisfied, the controller 4 determines that the bed 10 is not rotating (is not rotating) and proceeds to step S14.

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 execute both compliance control as the first control and speed increase control as the second control based on the longitudinal acceleration _ax and lateral acceleration _ay obtained by the first and second current sensors SW1 and SW2.

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

Proceeding to step S15 corresponds to a 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 optimized for cornering, which assists manual movement in both the forward/backward and left/right directions.

The processing performed in steps S12 and S14, and the processing performed in step S15 will be described below in order. When proceeding to these steps, the controller 4 will drive the first and second Mecanum wheels 21R, 21L via the first and second motors 22R, 22L to assist the movement of the bed 10 along the movement direction determined in step S11 above. During this process, the controller 4 in this embodiment will execute compliance control as a first control, and speed increase control as a second control.

Compliance control is performed by the controller 4 based on the acceleration estimated in step S3 (i.e., at least one of the vertical acceleration _ax and the lateral acceleration _ay ). In this compliance control, the controller 4 sets speed commands in the front-rear or left-right direction, i.e., command values for the vertical velocity _vx and the lateral velocity _vy , so that the speed commands follow the manual pushing movement of the bed 10.

As explained with regard to the equations (9) to (12), by setting the command values of the longitudinal velocity _{v_x} and the lateral velocity _{v_y} , the command values of the first rotation speed _{r_r} and the second rotation speed _{r_l} are uniquely determined.

Hereinafter, the command values of the longitudinal velocity _vx and the lateral velocity _vy will be referred to as the longitudinal velocity command _Vx and the lateral velocity command _Vy , respectively. Also, the command values of the first rotation speed _rr and the second rotation speed _rl of each motor 22R, 22L will be referred to as the first command rotation speed _Rr and the second command rotation speed _Rl, respectively.

Setting the longitudinal velocity command _Vx and the lateral velocity command _Vy by compliance control as in this embodiment is equivalent to setting the first command rotation speed _Rr and the second command rotation speed _Rl, respectively, so as to follow the movement of the bed 10.

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 referenced 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 _Vx and the lateral speed command _Vy (particularly the absolute values of the speed commands _Vx and _Vy ) set in the compliance control.

Increasing the longitudinal speed command _Vx and the lateral speed command _Vy by speed increase control as in this embodiment is equivalent to increasing the first command rotation speed _Rr and the second command rotation speed _Rl (particularly, the absolute values of each command rotation speed _Rr , _Rl ), respectively.

First, we will explain what happens when the control process proceeds to step S12 or step S14. Here, steps S31 to S36 in Figure 15 exemplify the processing executed in step S12 or S14 in Figure 10, respectively. In other words, when the control process proceeds to step S12 or S14, the controller 4 executes each step in order, starting with step S31 in Figure 15.

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 executes compliance control based on the lateral acceleration _ay , and also executes speed increase control based on the lateral speed command _Vy obtained through the compliance control.

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 = longitudinal direction", the controller 4 executes compliance control based on the longitudinal acceleration _ax , and also executes speed increase control based on the longitudinal speed command _Vx obtained through the compliance control.

The following describes in detail what happens when the process proceeds from step S14 to the flow in Figure 15. In the flow in Figure 15, step S31 relates to compliance control, and steps S32 to S34 relate to speed increase control.

First, in step S31, the controller 4 inputs the vertical acceleration _ax to the control block illustrated in Fig. 11 to calculate a command value for the vertical velocity _vx . The input vertical acceleration _ax is estimated based on the detection signals of the first and second current sensors SW1 and SW2, and corresponds to the estimated value (actual measured value) of the vertical acceleration _ax .

In this control block, s is the Laplace operator, and M represents the inertia of the bed 10 and the transport assistance device 1. Furthermore, D is the damping coefficient between the support position of the bed 10 by the transporter 100 (e.g., the headboard 11h) and the first and second Mecanum wheels 21R, 21L, and K is the 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.

If the transport assist device 1, the bed 10, and the transporter 100 are considered to be rigid bodies, the vertical velocity _vx generated when the first and second Mecanum wheels 21R, 21L rotate due to the application of an external force will change in synchronization with the forward and backward moving speeds of the bed 10 and the transporter 100, and the magnitudes of these speeds will also match. In this case, by integrating the measured value of the vertical acceleration _ax over time, a vertical velocity command _Vx that follows the manual pushing movement of the bed 10 can be obtained.

However, in reality, the frame 12 of the bed 10 and the mounting fixture 7 of the transport assist device 1 are interposed between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L. Due to bending of the frame 12, etc., the actual vertical speed _vx may change with a delay from the moving speed of the bed 10 and the transported person 100, or a deviation may occur between the actual vertical speed vx and the moving speed.

The influence of such delays and deviations is modeled in the control block shown in Fig. 11. This control block represents compliance control in which physical quantities corresponding to forces (longitudinal acceleration _ax , lateral acceleration _ay ) are input and velocity commands (longitudinal velocity command _Vx , lateral velocity command _Vy ) are output.

In Fig. 11, first, the actual measured value of the longitudinal acceleration _ax passes through a subtractor P2 and is then input to a first block B1. In this first block, the actual measured value of the longitudinal acceleration _ax is time-integrated. The output of the first block B1 indicates a correction amount ΔV of the longitudinal velocity command _Vx (amount of correction of the velocity command value) corresponding to the magnitude of the longitudinal acceleration _ax . The controller 4 sets the longitudinal velocity command _Vx by adding the correction amount ΔV to the current longitudinal velocity command _Vx or by integrating the correction amount ΔV.

Furthermore, 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 subtracted from the actual measured value of vertical acceleration _ax . This feedback is intended to incorporate damping proportional to the vertical velocity command _Vx (particularly, damping occurring between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L).

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 subtracted from the actual measured value of the vertical acceleration _ax , similar to the multiplied value via the second block B2. This feedback is intended to incorporate a restoring force proportional to the amount of displacement (in particular, a restoring force caused by the deflection between the support position of the bed 10 and the first and second Mecanum wheels 21R, 21L).

By reflecting the two feedbacks in the vertical acceleration _ax , the acceleration of the bed 10 (particularly the acceleration at the support position of the person being transported 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.

Furthermore, signal processing (e.g., processing using a delay operator) may be performed on the way from adder P1 to subtractor P2 to compensate for the time lag associated with feedback.

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

On the other hand, as shown in the center diagram of Figure 12, when the person 100 is moving faster than the transport assistance device 1, the acceleration estimated by the first and second current sensors SW1 and SW2 is positive. In this case, an external force pushing the bed 10 is being applied (see arrow F1). In this case, the longitudinal acceleration _ax input to the control block in Figure 11 is positive, and the correction amount ΔV output from that control block is also positive. In this case, 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 as to be at the same speed as the bed 10 and the person 100.

On the other hand, as shown in the lower diagram of Figure 12, if the person 100 is moving slower than the transport assistance device 1, the acceleration estimated by the first and second current sensors SW1 and SW2 will be negative. In this case, an external force that pulls the bed 10 is being applied (see arrow F2). In this case, the vertical acceleration _ax input to the control block in Figure 11 will be negative, and the correction amount ΔV output from that control block will also be negative. In this case, the restoring force related to the fourth block B4 acts in a direction that reduces the correction amount ΔV (see arrow F4). As a result, the transport assistance device 1 will decelerate with a delay from the application of the external force so as to be at the same speed as the bed 10 and the person 100.

In the following steps S32 to S34, the controller 4 executes the aforementioned speed increase control. When executing this speed increase control, the controller 4 increases the speed command value by a larger amount as the rotation speed detected by the first and second rotation sensors SW3 and SW4 increases (see Figure 13).

Specifically, in step S32, the controller 4 sets the speed increase amount _{v_off} so that it increases as the longitudinal speed _{v_x} increases. Instead of the longitudinal speed _{v_x} , the speed increase amount _{v_off} may be set so that it increases as the longitudinal rotation speed _{r_x} increases.

15 from step S12, the lateral velocity v _y is determined instead of the longitudinal velocity v _x . In other words, the controller 4 sets the velocity increase amount v _off based on the movement direction determined in step S11 of FIG.

In the following step S33, the controller 4 determines whether the following relational expression (17) is satisfied. Step S33 determines whether the absolute value of the vertical acceleration _ax 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).

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

15 from step S12, the lateral acceleration _ay is compared instead of the vertical acceleration _ax . That is, the controller 4 determines whether the acceleration in the movement direction determined in step S11 of FIG. 10 is equal to or greater than a fourth threshold value T4.

Here, if the above formula (17) is satisfied (i.e., if the absolute value of the vertical acceleration _ax is equal to or greater than a predetermined value), the controller 4 determines that the bed 10 is being pushed, and proceeds to step S34 (step S33: YES).

In step S34, the controller 4 adds the speed increase amount _voff to the speed command (longitudinal speed command _Vx ) calculated in step S31. The controller 4 sets the added value thus obtained as the final speed command (assist speed) (step S36). The assist speed in the longitudinal direction is the aforementioned longitudinal speed command _Vx . The assist speed in the lateral direction is the aforementioned lateral speed command _Vx .

It should be noted that instead of calculating the speed increase amount _voff 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, SW4 increases, and multiply the speed command by this increase magnification to perform speed increase control.

On the other hand, if the above formula (17) is not satisfied (i.e., if the absolute value of the vertical acceleration _ax is lower than the predetermined value), the controller 4 determines that the bed 10 is not being pushed, and proceeds to step S35 (step S33: NO).

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

Specifically, in step S35, the controller 4 subtracts Δv2 from the speed increase _voff at that time, and then advances the control process to step S34. The subtraction amount Δv2 from the speed increase _voff may be constant. If the subtraction amount Δv2 is set constant, the speed increase _voff will gradually decrease as the bed 10 is repeatedly placed in an unpushed state. Furthermore, during this subtraction, the speed increase _voff is configured not to become less than zero. This ensures an assist speed that can follow the movement of the bed 10.

For example, when the process proceeds from step S33 to step S34 in the nth loop, the longitudinal speed command _Vx is increased by the speed increase amount _voff corresponding to the longitudinal speed _vx . Thereafter, when the process proceeds from step S33 to step S35 in the (n+1)th loop, the speed increase amount _voff is subtracted from the value at the time of the nth loop. Thereafter, when the process proceeds from step S33 to step S35 is repeated, the longitudinal speed command _Vx decreases toward the value calculated in step S31.

Figure 14 is a graph comparing the assist rotation speed (dashed line) when compliance control is performed but speed increase control is not performed, with the assist rotation speed (solid line) when both compliance control and speed increase control are performed. The circles in Figure 14 indicate the timing at which it was determined that the bed 10 had been pressed (the timing at which the determination in step S33 was YES).

When compliance control alone is performed, the assist rotation speed rises with a delay after the bed 10 moves, and then fluctuates at a value that follows that movement.

On the other hand, if both compliance control and speed increase control are executed, the assist rotation speed will rise sharply each time it is determined that the bed 10 has been pushed (see, for example, t = t1, t2, t3). On the other hand, if a period of time continues during which it is determined that the bed 10 has not been pushed, the assist rotation speed after standing up will gradually decrease over time (see, for example, t1 < t < t2, t2 < t < t3).

When the processing of step S36 is completed, the control process ends the flows of Figures 10 and 15 and proceeds to step S7 of Figure 9.

The explanation regarding Figure 15 also applies when proceeding from step S12 to the flow of Figure 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 formulas. 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.

On the other hand, if the process proceeds from step S13 to step S15, the controller 4 sets the assist rotation speeds in both the vertical and horizontal directions for cornering to assist the bed 10 in cornering.

Here, steps S41 to S44 in Fig. 16 each exemplify the processing executed in step S15 in Fig. 10. That is, when the control process proceeds to step S15, the controller 4 executes each step in order from step S41 in Fig. 16 .

First, in step S41, the controller 4 adjusts the lateral acceleration _ay estimated in step S3 of Fig. 9 so as to decrease it at a predetermined rate greater than 0. Specifically, the controller 4 maintains the value of the vertical acceleration _ax estimated in step S3, while converting the lateral acceleration _ay as shown in the following equation (18).

_ay '= _cy * _ay ...(18)
In the above formula (18), c _y indicating the predetermined ratio is set in advance according to the dimensions, weight, configuration, etc. of the bed 10 and the transport assist device 1, and is stored in the controller 4. Specifically, the predetermined ratio c _y is set to less than 1 (0<c _y <1), and even more specifically, to less than 0.5 (0<c _y <0.5).

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 Figure 17).

Note that the central position Pc here refers to the central position of the first and second Mecanum wheels 21R, 21L in the left-right direction, as shown in Figure 4, and may also be the position where the first and second rotation axes Oy1, Oy2 intersect in the front-rear direction.

In the following step S42, the controller 4 executes compliance control as a first control in the longitudinal direction based on the longitudinal acceleration _ax estimated in step S3.

In particular, the controller 4 according to this embodiment sequentially executes both compliance control and speed increase control as a second control in the longitudinal direction based on the longitudinal acceleration ax estimated in step _S3 . Details of the compliance control and speed increase control in the longitudinal direction are as described with reference to Fig. 15. By executing step S42, the controller 4 sets a speed command in the longitudinal direction as described above.

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.

In the following step S43, the controller 4 executes compliance control as a first control in the left-right direction (lateral direction) based on the lateral acceleration a _y ' adjusted in step S41.

In particular, the controller 4 according to this embodiment executes compliance control for the lateral direction based on the adjusted lateral acceleration a _y ', and does not execute the speed increase control as the second control. In this case, the controller 4 executes the processes other than steps S32 to S35 in FIG. 15 to set a speed command in the left-right direction.

In other words, in the left-right direction, control is executed to calculate a speed command (and thus the command rotation speeds 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 speeds) in synchronization with the bed 10 being pushed is intentionally not executed.

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.

When the flows relating to steps S12, S14, and S15 in Fig. 10 are completed, the control process proceeds to step S7 in Fig. 9. In step S7, the controller 4 converts the longitudinal velocity command _Vx or the lateral velocity command _Vy set as the assist rotation speed into a first command rotation speed _Rr and a second command rotation speed Rl, respectively, through the following equations (19) and (20) which are determined similarly to the above equations (5 ₎ and (6).

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, Vx _≠ 0 and _Vy =0, when assisting in the lateral direction, _Vx =0 and _Vy ≠0, and when assisting in cornering, Vx _≠ 0 and _Vy ≠0.

For example, if the controller 4 determines that the movement direction of the bed 10 is the forward/backward direction (if the process has gone through step S14), it sets the first and second command rotation speeds Rr and _Rl 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. 7, and during this setting, the absolute values of the command rotation speeds for the first Mecanum wheel 21R and the second Mecanum wheel 21L are made equal ( _Rr = _Rl ).

By making the absolute values of the first and second command rotation speeds R _r and R _l equal, movement along the front-rear direction can be stabilized regardless of the orientation of each caster 14 .

Furthermore, when the controller 4 determines that the movement direction of the bed 10 is the left-right direction (when the process has gone through step S12), it sets the first and second command rotation speeds Rr and _Rl so that one of the first and second Mecanum wheels 21R, 21L rotates forward and the other rotates backward, as illustrated in the lower left of FIG. 7, and in this setting, the absolute values of the command rotation speeds of the first Mecanum wheel 21R and the second Mecanum wheel 21L are made equal ( _{Rr = -Rl} ).

Furthermore, when the controller 4 determines that the bed 10 is cornering (when the process has gone through step S12), it sets the first and second command rotation speeds _Rr , Rl so as to rotate at least one of the first and second Mecanum wheels 21R, 21L, as illustrated in the lower right of Fig. 7. When setting these command rotation speeds, different absolute values are set for the first Mecanum wheel 21R and the second Mecanum wheel 21L (| _{Rr |} ≠ | _Rl |) so that the turning center Ot is located at the position illustrated in Fig. 17.

Then, in step S8, which follows step S7, the controller 4 executes safety control processing. Details of this processing are shown in steps S51 and S52 of Figure 18.

First, in step S51, the controller 4 determines whether the absolute values of the command rotational speeds _Rr and _Rl set through the flow of Fig. 9 are equal to or greater than a predetermined fifth threshold value T5. Here, the magnitude of the fifth threshold value T5 is stored in advance in the memory of the controller 4, and is read out as needed.

If the determination in step S51 is YES, the controller 4 advances the control process to step S52. In step S52, the controller 4 changes the command rotational speeds R _r and R _l to a fifth threshold value T5.

On the other hand, if the determination in step S51 is NO, the controller 4 skips step S52 and returns to the main routine. In this case, the magnitudes of the command rotational speeds R _r and R _l are maintained below the fifth threshold value T5.

In this way, the controller 4 according to this embodiment is configured to maintain the values of the first and second command rotational speeds _Rr , _Rl when the first and second command rotational speeds _Rr , _Rl are less than the predetermined threshold value (fifth threshold value T5) (step S51: NO) after the speed increase control as the second control, and to change the first and second command rotational speeds _Rr , _Rl to the fifth threshold value T5 when the first and second command rotational speeds _Rr , _Rl are equal to or greater than the fifth threshold value T5 (step S51: YES).

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 first and second motors 22R and 22L are driven to realize the command rotation speeds _Rr and _Rl determined through the above-mentioned steps S5, S6, and S7.

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

This allows the bed 10 to turn while sliding sideways, rather than turning around the center position Pc as occurs when assistance is provided only in the forward/backward direction. For example, when turning right as shown in Figure 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 of the turning direction) acts, so by feeding back and assisting this external force, cornering is achieved in which the bed 10 slides to the left (a drift, so to speak).

As a result, cornering is achieved with the turning center Ot shifted toward the front end of the bed 10, as shown in Figure 17, making it possible to turn the bed 10 along the trajectory shown in the same figure.

If lateral assistance were not provided, the trajectory would be such that the center position Pc of the first and second Mecanum wheels 21R, 21L would be the turning center Ot, as shown in the conventional example in Figure 19. Such a trajectory would have a small cornering radius, which could cause interference between the bed 10 and corners of the aisle, etc., which is inconvenient.

Also, although not shown in the figures, 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 providing feedback and assisting this external force, cornering that slides the bed 10 to the right is achieved. In this case too, it is possible to achieve a smooth trajectory such as that shown in Figure 17.

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 Figure 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 forces, the bed 10 can be slid 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.

Furthermore, as illustrated in steps S2 and S3 of Figure 9, by detecting the induced current, it is possible to estimate the torque that caused the induced current (the torque that tends to rotate the first and second Mecanum wheels 21R, 21L), and ultimately 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.

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 shown in step S41 of Figure 16, the acceleration in that direction is reduced and compliance control is performed based on that 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.

Furthermore, as explained using Figure 17, by shifting the rotation center Ot of the bed 10 toward the front end, it is possible to achieve an operation in which the rear end of the bed 10 rotates more than the front end when cornering. By rotating the rear end more, it is possible to reduce interference between the rear end portion and the corners of the aisle. This is advantageous in appropriately assisting the cornering of the bed 10.

Furthermore, as shown in step S42 of Figure 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 transporter 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 transporter 100 with an appropriate "sense of assistance." On the other hand, as shown in step S43 of Figure 16, 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 transporter 100) and keeps the cornering radius within an appropriate range. This is advantageous in providing appropriate assistance to the cornering of the bed 10.

Furthermore, by configuring and arranging the first and second Mecanum wheels 21R, 21L as illustrated 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 force can be generated that causes the bed 10 to turn. This configuration is effective in appropriately assisting the cornering of the bed 10.

Furthermore, by making the absolute value of the commanded rotation speed equal when moving forward or backward, more stable forward or backward movement can be achieved regardless of the orientation of the caster 14. On the other hand, by intentionally making the absolute value different when cornering, cornering along the desired trajectory can be achieved.

<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.

Furthermore, in the above embodiment, the speed command (translational speed command value) was increased by speed increase control, but such a configuration is not essential.

For example, in steps S32 to S34, processing to increase the commanded rotation speed may be performed instead of processing related to the speed command. In this case, processing to convert the speed command into a commanded rotation speed would be provided between steps S31 and S32.

1 Transport auxiliary device 4 Controller 10 Bed (bed with casters)
14 Caster 14F Front wheel 14B Rear wheel 21R First Mecanum wheel 211R First wheel body (wheel body)
212R No. 1 barrel roller (barrel roller)
21L Second Mecanum Wheel 211L Second Wheel Body (Wheel Body)
212L No. 2 barrel roller (barrel roller)
22R First motor 22L Second motor c _y Predetermined ratio F Conveying surface Ot Turning center Pc Central position Oy1 First rotation axis (rotation axis)
Oy2 Second rotation axis (rotation axis)
Or First 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 (4)

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. 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. 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;
The transport assist device is characterized in that, 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 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 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: