WO2024195548A1 - Conveyance assistance device - Google Patents

Abstract

A conveyance assistance device (1) is provided with: first and second mecanum wheels (21R, 21L) that are attached to a bed (10); first and second motors (22R, 22L) that are drivingly connected to the first and second mecanum wheels; first and second current sensors (SW1, SW2) for detecting induction currents flowing through the motors (22R, 22L) during rotation of the wheels (21R, 21L); and a controller (4). The controller (4) estimates an acceleration of the bed (10) using the induction currents, sets a command rotational speed for each motor (22R, 22L) so as to follow the movement of the bed (10) on the basis of the acceleration, and increases the command rotational speed when the acceleration is equal to or greater than a predetermined value.

Description

Transport Auxiliary Equipment

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 certain direction, a force in the same direction is applied by the operator. When each Mecanum wheel rotates due to the applied force, the associated 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.

Special table 2016-525977 publication

When using a configuration such as that described in Patent Document 1, it is conceivable that when assisting the movement of an object such as a chassis, the command speed of the motor can be set to follow that movement.

However, simply having the bed follow the movement of the object will lack the "feeling of assistance" and the bed will feel heavy when pushed by the transporter. Further ingenuity is required to make the bed feel lighter.

The technology disclosed here was developed in consideration of these points, and its purpose is to make the object easier to press when assisting in its movement.

The first aspect of the present disclosure relates to a transport assist device for assisting the movement of an object caused by an external force. This transport assist device includes a wheel attached to the object, a motor drivingly connected to the wheel, a current sensor that detects an induced current flowing through the motor when the wheel rotates, and a controller that controls the motor, and the controller estimates the acceleration of the object based on the detection signal of the current sensor, executes a first control that sets a command rotation speed of the motor based on the acceleration so as to follow the movement of the object, and executes a second control that increases the command rotation speed set in the first control when the absolute value of the acceleration is equal to or greater than a predetermined value.

According to the first 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 wheel). By estimating this torque, it is possible to estimate the acceleration of the object. This acceleration increases according to the external force applied by the operator, so by determining whether the absolute value of the acceleration is equal to or greater than a predetermined value, it is possible to determine whether the object has been pushed.

By carrying out the second control in addition to the first control, it is possible not only to have the robot follow the object, but also to reduce the load on the transporter by the amount of the commanded rotation speed increased through the second control. This makes the object feel lighter when pressed, providing the transporter with an appropriate "feeling of assistance."

Furthermore, by executing the second control when the absolute value of the acceleration is equal to or greater than a predetermined value, in other words, when the object is pressed, it is possible to synchronize the timing when the transporter presses the object with the timing when the object becomes easier to press. This makes it possible to provide the transporter with a feeling of assistance that is neither too much nor too little. Also, by configuring the second control to be executed on the condition that the object is pressed, it is possible to avoid a situation in which the transport assistance device unintentionally starts to move on its own as a result of executing the second control when the object is not being pressed.

Furthermore, according to a second aspect of the present disclosure, the transport assist device may include a rotation sensor that detects the rotation speed of the motor, and when the controller increases the command rotation speed, the greater the rotation speed detected by the rotation sensor, the greater the increase in the command rotation speed.

It is believed that the harder the transporter pushes the object, the higher the detected rotation speed will be. According to the second aspect, the harder the transporter pushes the object, the stronger the thrust is used to assist the movement of the object. This makes it possible to provide assistance according to the magnitude of the external force, which is advantageous in making the object easier to press.

Furthermore, according to a third aspect of the present disclosure, the controller may be configured to reduce the command rotation speed after the second control when the absolute value of the acceleration falls below the predetermined value.

According to the third aspect, when the transporter pushes the object lightly or releases the object, the movement of the object is assisted with a weaker thrust. This makes it possible to realize assistance according to the magnitude of the external force, giving the transporter a feeling of assistance that is just right and preventing unintended self-propulsion of the transport assistance device.

Furthermore, according to a fourth aspect of the present disclosure, the transport assistance device may include a rotation sensor that detects the number of rotations of the motor, and the controller may allow the wheel to be driven on the condition that the number of rotations reaches or exceeds a predetermined value based on the detection signal of the rotation sensor.

According to the fourth aspect, when the rotation speed is less than a predetermined value, the drive of the wheel is limited. This makes it possible to execute the first control and the second control only when the object is actually being transported. This contributes to improving the usability of the transport assistance device.

Furthermore, according to a fifth aspect of the present disclosure, the transport assistance device includes a rotation sensor that detects the number of rotations of the wheel and an inclination sensor that detects the inclination angle of the transport surface along which the object moves, and the controller determines whether the transport surface is a slope based on the detection signal of the inclination sensor, and if the controller determines that the transport surface is not a slope, executes both the first control and the second control based on the acceleration obtained by the current sensor, while if the controller determines that the transport surface is a slope, it determines whether the object is ascending along the slope based on the detection signals of the rotation sensor and the inclination sensor, and if it determines that the object is ascending, it increases the acceleration obtained by the current sensor, executes the first control based on the increased acceleration, and does not execute the second control.

If the second control is performed when climbing a slope, the sense of assistance improves at the moment when the object begins to be pushed, but the sense of assistance does not improve thereafter (while the object is climbing). Therefore, according to the fifth aspect, when it is determined that the object is climbing a slope, the acceleration referenced in the first control is increased, and the first control is executed based on the increased acceleration. Increasing the acceleration is equivalent to overestimating the external force acting on the object than the actual external force. Overestimating the external force achieves assistance that exerts a thrust force greater than that required to follow the movement of the bed. This process is performed as long as the slope continues, so that a good sense of assistance can be continuously exerted while climbing a slope.

Furthermore, according to a sixth aspect of the present disclosure, the transport assistance device may include a rotation sensor that detects the number of rotations of the wheel, and an inclination sensor that detects the inclination angle of the transport surface along which the object is transported, and the controller may determine whether the transport surface is a slope based on the detection signal of the inclination sensor, and if the controller determines that the transport surface is not a slope, execute both the first control and the second control based on the acceleration obtained by the current sensor, while if the controller determines that the transport surface is a slope, determine whether the object is descending along the slope based on the detection signals of the rotation sensor and the inclination sensor, and if the controller determines that the object is descending, execute the first control based on the acceleration obtained by the current sensor and do not execute the second control.

If the second control is performed when going downhill, the object may be accelerated more than necessary, causing it to fall out of the carrier's hands. Therefore, according to the sixth aspect, when it is determined that the object is going downhill, only the first control is performed without increasing the acceleration, and the second control is not performed. This makes it possible to provide a sense of assistance that is appropriate when going downhill.

Furthermore, according to a seventh aspect of the present disclosure, during the first control, the controller may maintain the value of the command speed when the command speed is less than a predetermined threshold, and change the command speed to the threshold when the command speed is equal to or greater than the threshold.

According to the seventh aspect, the command rotation speed value can be maintained below the threshold value. This makes it possible to further improve the safety of the transport assistance device compared to conventional methods.

Furthermore, according to an eighth aspect of the present disclosure, the object may be a bed with casters, and the wheels may be attached to the bottom of the bed with casters.

In the eighth aspect, the object is a bed with casters. Even when assisting in the movement of a heavy object such as a bed with casters, the comfort of pushing the object by the carrier can be reduced.

As described above, the present disclosure makes it possible to reduce the pressure felt by the transporter when assisting in the movement of an object.

1 is a side view illustrating an example of the overall configuration of a transport assistance device and a bed with casters. 1 is a bottom view illustrating an example of the overall configuration of a transport assistance device and a bed with casters. FIG. FIG. 2 is a perspective view illustrating a configuration of a transport auxiliary device. FIG. 2 is a plan view illustrating a configuration of a transport auxiliary device. FIG. 2 is a side view illustrating a configuration of a transport auxiliary device. 4 is a block diagram illustrating a configuration of a control system of the transport assist device. FIG. 11A and 11B are diagrams for explaining the operation of the first and second Mecanum wheels. 1 is a diagram for explaining a detection target of a six-axis sensor; 4 is a flowchart illustrating main processing performed by a controller. 11 is a flowchart illustrating a process related to determination of a moving direction. FIG. 2 is a control block diagram illustrating a configuration of compliance control. FIG. 1 is a conceptual diagram for explaining a basic concept of compliance control. FIG. 13 is a diagram illustrating an example of a change in speed increase amount relative to the number of rotations. 11 is a diagram illustrating an example of a command rotation speed obtained by speed increase control. FIG. 11 is a flowchart illustrating a compliance control and a speed increase control. 10 is a flowchart illustrating a process relating to ascending/descending a slope. 4 is a flowchart illustrating a safety limit control.

The following describes an embodiment of the present disclosure with reference to the drawings.

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

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

FIG. 6 is a block diagram illustrating the configuration of the control system of the transport auxiliary device 1, and 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 6-axis sensor SW5.

The transport assistance device 1 is attached to a specific object. This transport assistance device 1 is a device for assisting the movement of an object by an external force (e.g., an external force applied by the transporter 100).

As shown in Figures 1 and 2, the object of this embodiment is 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 to be used, for example, as a medical bed.

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 short side of the bed 10, that is, the direction perpendicular to the front-to-rear direction on a horizontal plane, is defined as the "left-to-right direction" or "lateral direction", the direction toward the depth of the paper in FIG. 1 along that left-to-right direction is defined as the "right", and the 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-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 manual movement of the bed 10 supported by the carrier 100.

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 section 13 that raises and lowers the bed body 11 relative to the frame 12, and a number 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.

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 located 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.

Of these, the headboard 11h is supported from the rear by the carrier 100 in order to manually move the bed 10. The headboard 11h functions as a support part to which force is applied by the carrier 100. By attaching members such as a handle or grip to the headboard 11h or integrating them with the headboard 11h, these members may serve as the support part. The footboard 11f, side rails 11s, etc. may also be supported.

As shown in FIG. 2, the frame 12 is configured in a rectangular frame shape, with the four sides being 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-rear direction. The left frame 12L is located on the left side of the bed 10 and extends in the front-to-rear 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 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 multiple casters 14 support the frame 12, the lifting section 13, and the bed body 11 on 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 is tilted in the left-right direction by rotating the fork part 14b relative to the attachment part 14a.

The transport assistance device 1 is positioned 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 is positioned in the center of the bed 10 in the left-and-right direction.

As shown in Figures 1 to 6, the transport auxiliary device 1 includes a storage box 6, a mounting fixture 7, first and second Mecanum wheels 21R, 21L as wheels, first and second motors 22R, 22L, a controller 4, first and second current sensors SW1, SW2 as current sensors, first and second rotation sensors SW3, SW4 as rotation sensors, and a six-axis sensor SW5 as a tilt sensor (the first and second motors 22R, 22L and the sensors SW1 to SW5 are only shown in Figure 6). In the following, 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 the 6-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.

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

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

In more detail, 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.

Here, the front rail member 71f and the rear rail member 71b are spaced apart in the front-to-rear direction, and each spans the front-to-rear center of the right frame 12R and the front-to-rear center of the left frame 12L. 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 Figs. 3 and 4 is supported by the rear rail member 71b so that it can swing. The front end of the first arm member 72R rotatably supports the first Mecanum wheel 21R. In addition, the first arm member 72R is arranged to be positioned between the first Mecanum wheel 21R and the storage box 6 in the left-right direction.

Also, 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 as to be able to 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 also arranged to be positioned between the second Mecanum wheel 21L and the storage box 6 in the left-right direction.

Also, 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).

The first and second Mecanum wheels 21R, 21L are attached to the lower part (bottom) of the bed 10, as shown in Figures 1 and 2. The first and second Mecanum wheels 21R, 21L are in contact with the transport surface F of the bed 10. The transport surface F is only shown in Figure 1. The first and second Mecanum wheels 21R, 21L are also 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 so as to be aligned in the left-right direction, which is the short side direction, as shown in Figure 2.

In more 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 number 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 with respect 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 a number 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 with respect 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 relative to the second tilt axis Ol so as to be linearly 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 the 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.

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

More specifically, the inclination angle θr of the first inclined axis Or relative to the first rotation axis Oy1 is set to 45° in plan view. Similarly, the inclination angle θl of the second inclined axis Ol relative to the second rotation axis Oy2 is also set to 45° in plan view. Note that the inclination direction and inclination angle of each barrel-shaped roller 212R, 212L are not limited to these examples. For example, the entire transport 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.

As mentioned 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.

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.

The first and second motors 22R, 22L are supplied with a motor current corresponding to the torque load when they rotate. The motor current can be used to switch the rotation speed of the first and second motors 22R, 22L and between forward and reverse rotation.

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).

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

In this embodiment, the first Mecanum wheel 21R rotates forward when the first motor 22R rotates in the forward direction, and the first Mecanum wheel 21R rotates backward when the first motor 22R rotates in the reverse direction. Similarly, in this embodiment, the second Mecanum wheel 21L rotates forward when the second motor 22L rotates in the forward direction, and the second Mecanum wheel 21L rotates backward when the second motor 22L rotates 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 in the first and second motors 22R and 22L in this way, the entire transport assistance device 1 can be simplified and made compact.

The first current sensor SW1 also detects the induced current that flows 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 in 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 thus to the amount of speed change of the bed 10 caused by the external force. Furthermore, 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 the opposite sign 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 in 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 the second mecanum wheel 21L 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 thus to the amount of speed change of the bed 10 caused by the external force. Furthermore, 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 in response to an external force. The sign of the induced current is the opposite sign 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 perform 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).

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 with an encoder. 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 FIG. 8, the six-axis sensor SW5, which serves as an inclination sensor, detects the inclination angle of the transport surface F along which the bed 10 moves. In more detail, the six-axis sensor SW5 is configured to be capable of detecting at least the angular velocity of the rotation angle (the so-called pitch angle θ) around the y-axis extending in the left-right direction.

More specifically, the six-axis sensor SW5 according to this embodiment can detect not only the angular velocity of the pitch angle θ, but also the 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 z-axis (the so-called yaw angle ψ). The detection signal of the six-axis sensor SW5 is 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 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 each rotate at the command rotation speeds set by the controller 4.

At that 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.

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 to the transport assistance device 1 and the bed 10 in a diagonal forward left direction (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 to the bed 10 in a diagonal forward right direction (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, 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 in 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 assistance 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 assistance 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 FIG. 7, when both the first and second Mecanum wheels 21R, 21L are rotated backwards, the thrust to the right applied by rotating the first Mecanum wheel 21R backward and the thrust to the left 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 thrust to the rear. This thrust can assist in the movement of the bed 10 backwards.

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, the first Mecanum wheel 21R is rotated backward and the second Mecanum wheel 21L is rotated forward, thereby applying a thrust to the right to the bed 10.

In addition, 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 movement of the bed 10 can be assisted 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 type of 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 that direction of action.

For example, if it is determined that an external force is acting from the rear to 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 in the forward direction, thereby rotating both the first and second Mecanum wheels 21R, 21L forward. This makes it possible to assist the forward movement of the bed 10, as shown in the upper left of FIG. 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, and allows for stable transportation of the bed 10.

The assistance provided by the controller 4 will be explained in detail below with reference to FIG. 9 etc.

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 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 the change in the speed increase amount relative to the rotation speed. FIG. 14 is a diagram illustrating the command rotation speed obtained by speed increase control. FIG. 15 is a flowchart illustrating compliance control and speed increase control.

FIG. 16 is a flowchart illustrating processing related to going uphill and downhill. FIG. 17 is a flowchart illustrating safety limit control.

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

In the following step S2, the controller 4 estimates the acceleration of each of the first and second Mecanum wheels 21R, 21L individually 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 21L 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.

The magnitude of the induced current detected by the first and second current sensors SW1, SW2, respectively, is proportional to the torque (particularly the torque caused by the reaction force) acting on the first and second Mecanum wheels 21R, 21L when they rotate. Based on this proportional relationship, the controller 4 estimates the first torque acting on the first Mecanum wheel 21R and the second torque acting on the second Mecanum wheel 21L separately. In this case, the proportionality coefficient for converting the induced current to torque can be one that is pre-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 and 22L against the reaction forces corresponding to the first and second torques.

To achieve such 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 formulas (1) and (2), T _r [Nm] is the first torque, T _l [Nm] is the second torque, and a _r [m/s ² ] is the first torque. a l [m/s ² ] is a first acceleration corresponding to the second torque, and a _l [m/s 2 ] is a second acceleration corresponding to the second torque.

Otherwise, 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 estimates a vertical acceleration indicating the translational acceleration of the first and second mecanum wheels 21R, 21L in the front-rear direction and a lateral acceleration indicating the translational acceleration of the first and second mecanum wheels 21R, 21L in the lateral direction, respectively, using the first and second accelerations a _r , a _l estimated based on the detection signals of the first and second current sensors SW1, SW2.

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. The 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 vertical acceleration, and a _y [m/s ² ] is the lateral acceleration. The sign in the front and back may be reversed. Similarly, the sign in the formula (4) is positive on the left and negative on the right. The sign may be reversed between the left and right sides.

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-rear direction (hereinafter also referred to as the "vertical rotation speed"), and r _y [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.

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). Set r _x and _ry as shown in the following equations (7) and (8). In this way, r _r and r ₁ can be uniquely determined.

r _r = r _x + r _y …(7)
r _l = r _x - r _y (8)
In addition, a similar relational expression for the speed can be obtained 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 value of pi. That is, v _r [m/s] is the speed of the first Mecanum wheel 21R in the front-rear direction, and v _l [m/s] is the speed of the second Mecanum wheel 21L in the front-rear direction. _x [m/s] is the overall speed of the first and second Mecanum wheels 21R and 21L in the front-rear direction (hereinafter, also referred to as the "vertical speed"), and v _y [m/s] is the overall speed of the first and second Mecanum wheels 21R and 21L in the left-right direction. The speed of the first and second Mecanum wheels 21R, 21L as a whole (hereinafter, this will also be referred to as the "lateral speed"). In this arrangement, the following expressions (9) and (10) hold.

In this case, "velocity" refers to the translational speed (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), v _x and v _y are set. In this way, _vr and _vl can be uniquely set.

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, when the command values of the vertical speed v _x and/or the horizontal speed v _y are determined, the vertical rotation speed r _r and the horizontal rotation speed v y required to realize these command values can be calculated. It is possible to uniquely determine the number of rotations r 1 _r and the second number of rotations _{r 1 r corresponding} to the number of vertical rotations _r 1 _r and/or the number of horizontal rotations r 1 r.

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

Specifically, in step S4, which follows 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).

r _x ≧T1 (13)
r _y ≧T1 (14)
In the above formulas (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 expressed by the above formula (13). As described above, "r _x /r _y " in step S4 of FIG. 9 is the "value of r _x divided by r _y ". rather, it means "either r _x or r _y ."

Here, if neither of the above formulas (13) nor (14) is satisfied, the controller 4 determines that the bed 10 is not being transported, and does not allow the first and second motors 22R and 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 and 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 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 corresponds to the command value of the vertical rotation speed _rx and the horizontal rotation speed _ry described above.

Steps S11 to S16 in FIG. 10 each illustrate the processing executed in step S6 in FIG. 9. In other words, when the control process proceeds to step S6, the controller 4 starts step S11 in FIG. 10.

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

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 advances the control process to step S12 (step S11: NO). Details of the process 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/rearward direction, and advances the control process to step S13 (step S11: YES).

In the following steps S13 and S14, the controller 4 determines whether the conveying surface F is a slope based on the detection signal of the 6-axis sensor SW5, which serves as an inclination sensor.

Specifically, in step S13, the controller 4 calculates the inclination angle (road surface gradient) _θs of the conveying surface F based on the detection signal of the six-axis sensor SW5. This calculation can be performed based on, for example, the angular acceleration around the y-axis shown in FIG.

Next, in step S14, the controller 4 determines whether the following relational expression (16) is satisfied.

|θ _s |≧T3…(16)
In formula (16), T3 is a 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 appropriately as necessary.

If the above formula (16) is not satisfied, the controller 4 determines that the conveying surface F is a flat, non-sloping road, and advances the control process to step S15.

The case where the process proceeds to step S15 corresponds to the case where it is determined that the bed 10 is moving forward or backward and not ascending or descending a slope. In this case, the controller 4 performs the following steps to assist the manual movement of the bed 10 in the forward and backward directions, thereby executing both the compliance control as the first control and the speed increase control as the second control based on the vertical acceleration _ax and the lateral acceleration _ay obtained by the first and second current sensors SW1, SW2.

On the other hand, if the above formula (16) is satisfied, the controller 4 determines that the conveying surface F is a slope, and advances the control process to step S16.

The case where the process proceeds to step S16 corresponds to the case where it is determined that the bed 10 is moving forward or backward and ascending or descending a slope. In this case, the controller 4 executes control to assist the manual movement of the bed 10 in the forward and backward directions, and in particular executes control optimized for ascending or descending a slope.

The processes performed in steps S12 and S15, and step S16 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 so as to assist the movement of the bed 10 along the movement direction determined in step S11 above. During this process, the controller 4 according to this embodiment executes compliance control as the first control, and executes speed increase control as the second control.

The compliance control is executed 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 a velocity command in the front-rear or left-right direction, i.e., a command value of the vertical velocity _vx and the lateral velocity vy, so as to follow the movement of the bed ₁₀ as an object.

As described with respect to equations (9) to (12), by setting the command values of the longitudinal velocity _vx and the lateral velocity _vy , the command values of the first rotation speed _rr and the second rotation speed _rl 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 rotational speed _rr and the second rotational speed _rl of each motor 22R, 22L will be referred to as the first command rotational speed _Rr and the second command rotational speed _Rl, respectively.

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

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 _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 rotational speed _Rr and the second command rotational speed _Rl (particularly, the absolute values of each command rotational speed _Rr , _Rl ), respectively.

First, a case where the control process proceeds to step S12 or step S15 will be described. Here, steps S31 to S37 in FIG. 15 exemplify the processing executed in step S12 or S15 in FIG. 10, respectively. In other words, when the control process proceeds to step S12 or S15, the controller 4 executes each step in order starting from step S31 in FIG. 15.

For example, when the flow 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 velocity command _Vy obtained through the compliance control.

On the other hand, when the flow proceeds from step S15 to the flow of Fig. 15, that is, when it is determined that the "moving direction = longitudinal direction", the controller 4 executes compliance control based on the longitudinal acceleration _ax , and executes speed increase control based on the longitudinal speed command _Vx obtained through the compliance control. That is, " _ax / _ay " in step S31 of Fig. 15 does not mean " _ax divided by _ay ", but means "either _ax or _ay ".

Below, we will explain in detail what happens when you proceed from step S15 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 measurement 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 auxiliary device 1, the bed 10, and the transporter 100 are considered as rigid bodies, the vertical speed _vx generated when the first and second Mecanum wheels 21R, 21L rotate due to the application of an external force changes in synchronization with the forward and backward moving speeds of the bed 10 and the transporter 100, and the magnitudes of the speeds also match each other. In this case, by integrating the measured value of the vertical acceleration _ax over time, a vertical speed 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, 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 bending of the frame 12, etc., the actual vertical speed _vx changes with a delay from the moving speed of the bed 10 and the transporter 100, or a deviation occurs in value between the moving speed and the actual vertical 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 vertical 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 vertical acceleration _ax is integrated over time. The output of the first block B1 indicates a correction amount ΔV of the vertical speed command _Vx (a correction amount of the speed command value) corresponding to the magnitude of the vertical acceleration _ax . The controller 4 sets the vertical speed command _Vx by adding the correction amount ΔV to the current vertical speed command _Vx or integrating the correction amount ΔV.

The output from the block B1 is multiplied by D/M in the second block B2, 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 . This feedback is for incorporating damping proportional to the vertical speed 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 (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).

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 transported person 100) is estimated, taking into account bending, 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 auxiliary 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. 10 is zero, and the correction amount ΔV output from the control block is also zero. In this case, the transport auxiliary device 1 does not accelerate or decelerate.

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

On the other hand, as shown in the lower diagram of Fig. 12, when the transporter 100 moves behind the transport 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 is applied (see arrow F2). In this case, the vertical acceleration _ax input to the control block in Fig. 10 becomes negative, and the correction amount ΔV output from the control block also becomes negative. At that time, 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 decelerates with a delay from the application of the external force so as to be equal in speed to the bed 10 and the transporter 100.

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 speed detected by the first and second rotation sensors SW3 and SW4 increases (see FIG. 13). Note that the horizontal axis in FIG. 13 does not mean the value obtained by dividing the longitudinal speed by the lateral speed. The graph shown in FIG. 13 means that when setting the speed command value in the front-rear direction (longitudinal direction), the speed command value is set to be larger as the longitudinal speed _vx increases, and when setting the speed command value in the left-right direction (lateral direction), the speed command value is set to be larger as the lateral speed _vy increases.

Specifically, in step S32, the controller 4 sets the speed increase amount _voff so that it increases as the longitudinal speed _vx increases. Instead of the longitudinal speed _vx , the speed increase amount _voff may be set so that it increases as the longitudinal rotation speed _rx increases.

15 from step S12, the lateral velocity _vy is determined instead of the longitudinal velocity _vx . As described above, the controller 4 sets the velocity increase amount _{voff so that the velocity increase amount voff} increases as the lateral velocity _vy increases. In other words, the controller 4 sets the velocity increase amount _voff based on the moving direction determined in step S11 of FIG.

In the next step S33, the controller 4 determines whether or not the following relational expression (17) is satisfied. Step S33 is for determining whether or not 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 or not the bed 10 is being pushed in the moving direction (detecting the pushing force).

｜a _x ｜≧T4…(17)
In the above formula (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, etc. , which are read out as necessary.

15 from step S12, the lateral acceleration _ay is compared instead of the vertical acceleration _ax . In other words, the controller 4 determines whether the acceleration in the moving direction determined in step S11 in 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 forward/rearward direction is the aforementioned longitudinal speed command _Vx . The assist speed in the left/right direction is the aforementioned lateral speed command _Vy .

Note that, instead of calculating the speed increase amount _voff and adding it to the speed command, it is also possible to calculate an increase factor (>1) that increases as the rotation speeds detected by the first and second rotation sensors SW3, SW4 increase, and multiply the speed command by the increase factor 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 below a 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 of the speed increase _voff may be constant. If the subtraction amount Δv2 is set constant, the speed increase _voff will gradually decrease if the state in which the bed 10 is not being pushed is repeated. In addition, the speed increase _voff is configured not to become less than zero during this subtraction. 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 n-th loop, the longitudinal speed command _Vx is increased by the speed increase amount _voff corresponding to the longitudinal speed _vx . 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 in the n-th loop. When the process proceeds from step S33 to step S35 repeatedly, the longitudinal speed command _Vx decreases toward the value calculated in step S31.

FIG. 14 is a diagram comparing the assist rotation speed (dashed line) when compliance control is executed but 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 timing when it is determined that the bed 10 has been pressed (the timing when the determination in step S33 is YES).

When only compliance control is performed, the assist rotation speed rises with a delay from the movement of the bed 10, and then changes to a value that follows that movement.

On the other hand, when both compliance control and speed increase control are executed, the assist rotation speed rises 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 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).

More specifically, in Fig. 14, the period from when the assist rotation speed (assist speed) determined by compliance control starts to increase until it starts to decrease (the period from when the broken line increases until it starts to decrease) corresponds to the so-called "bed pushing" time, as shown in Fig. 12B. In this case, the determination in step S33 becomes YES as appropriate, and the speed increase amount _voff is set to a non-zero and positive value each time. For example, when the bed 10 is pushed relatively strongly (when it is pushed so strongly that the determination in step S33 becomes YES), the assist rotation speed rises sharply as described above, while when the bed 10 is pushed relatively weakly (when it is pushed so strongly that the determination in step S33 does not become YES), the assist rotation speed (assist speed) gradually decreases toward a value that follows the bed 10.

On the other hand, in Fig. 14, the period from when the assist rotation speed (assist speed) determined by compliance control starts to decrease (the period from when the dashed line starts to decrease until it reaches zero) corresponds to the so-called "bed retraction time" as shown in Fig. 12C. In this case, since the determination in step S33 is not YES, the speed increase amount _voff remains at its lower limit value (zero). As a result, the assist rotation speed (assist speed) decreases toward zero while being maintained at the value determined by compliance control.

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 FIG. 15 also applies to the case where the flow of FIG. 15 is proceeded to from step S12. 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 value T4 may be the same or different in the front-rear and left-right directions.

Next, we will explain what happens when the process proceeds to step S16 in FIG. 10. In this case, steps S41 to S44 in FIG. 16 are carried out in order.

First, in step S41, the controller 4 determines whether or not the bed 10 is moving up a slope, i.e., whether or not the bed 10 is climbing, based on the detection signals of the first and second rotation sensors SW3, SW4 and the six-axis sensor SW5.

The determination in step S41 is YES when the road surface gradient _θs is increasing forward and the moving direction is forward (longitudinal rotation speed _rx or longitudinal speed _vx > 0), or when the road surface gradient _θs is decreasing forward and the moving direction is backward (longitudinal rotation speed _rx or longitudinal speed vx < 0 ₎ .

On the other hand, the determination in step S41 is NO when the road surface gradient θ _s is increasing forward and the moving direction is backward, or when the road surface gradient θ _s is decreasing forward and the moving direction is forward.

The road surface gradient _θs referred to in the determination in step S41 may be the value calculated in step S13.

When the controller 4 determines that the bed 10 is ascending along a slope (step S41: YES), it increases the vertical acceleration _ax obtained by the first and second current sensors SW1, SW2, and then executes compliance control based on the increased vertical acceleration _ax ', without executing the speed increase control.

Specifically, in step S42, which follows when the determination in step S41 is YES, the controller 4 increases the vertical acceleration _ax obtained by the first and second current sensors SW1, SW2. The increase amount _Δax may be set to be larger as the road surface gradient _θs increases, for example.

Then, in step S43 following step S42, the controller 4 executes compliance control in the longitudinal direction based on the increased longitudinal acceleration a _x '. The details of step S43 are the same as those of step S31 relating to the longitudinal direction, except for whether or not the increased longitudinal acceleration a _x ' is used.

On the other hand, when the controller 4 determines that the bed 10 is descending along a slope (step S41: NO), the controller 4 executes compliance control based on the vertical acceleration _ax obtained by the first and second current sensors SW1 and SW2 without increasing the vertical acceleration _ax , and does not execute the speed increase control.

Specifically, in step S45 following the determination in step S41 being NO, the controller 4 sets the increase amount for the vertical acceleration _ax obtained by the first and second current sensors SW1, SW2 to zero, and maintains the value of the vertical acceleration _ax .

Then, in step S43 following step S45, the controller 4 executes compliance control in the longitudinal direction based on the non-increased longitudinal acceleration a _x ' (= a _x ). The details of step S43 are the same as those of step S31 described above.

Then, in step S44, which follows step S43, the controller 4 determines the final assist speed in the forward/rearward direction, similar to step S36 described above.

When climbing a slope, the vertical acceleration _ax continues to increase as long as the climbing state continues, as shown in steps S41 and S42 in Fig. 16. On the other hand, as described with reference to Fig. 14, the rise of the assist rotation speed in the speed increase control is approximately synchronized with the timing when the vertical acceleration _ax becomes equal to or exceeds a predetermined value, that is, the timing when an external force acts on the bed 10.

Therefore, to rephrase the process related to hill climbing, the controller 4 according to this embodiment judges whether the vehicle is traveling on flat ground or on an uphill slope, and based on the result of this judgment, when traveling on flat ground, it intermittently increases the commanded rotation speed of the motors (first and second motors 22R, 22L) so as to be synchronized with the timing at which an external force acts, and when climbing a slope, it maintains the increase in the commanded rotation speed as long as the uphill slope continues.

When the flows of steps S12, S15, and S16 in Fig. 10 are completed, the control process proceeds to step S7 in Fig. 9. In this step S7, the controller 4 converts the longitudinal speed command _Vx or the lateral speed command _Vy set as the assist rotational speed into a first command rotational speed _Rr and a second command rotational speed _Rl through the following equations (18) and (19) defined similarly to the above equations (5) and (6), respectively.

R _r =60*(V _x +V _y )/(2π・R)…(18)
R _l =60*(V _x −V _y )/(2π・R)…(19)
In the above formulas (18) and (19), "R" is the tire radius. In the present embodiment, V _x ≠ 0 and V _y = 0 during assistance in the forward/rearward direction, and V y = 0 during assistance in the left/right direction. During assistance, V _x =0 and V _y ≠0.

For example, when the controller 4 determines that the movement direction of the bed 10 is the forward/backward direction (when the process has gone through step S15), it sets the first and second command rotation speeds Rr, _Rl so that both the first and second mecanum wheels 21R, 21L rotate forward or backward, as illustrated in the upper left and upper right of FIG _{. 7, and when setting these, makes the absolute values of the command rotation speeds of the first mecanum wheel 21R and the second mecanum wheel 21L equal (Rr = Rl} ).

By making the absolute values of the first and second command rotational speeds R _r , 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, 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 part of FIG _{. 7, and also when setting these command rotation speeds, 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 )} .

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

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 FIG. 17.

First, in step S51, the controller 4 determines whether or not the absolute values of the command rotational speeds _Rr , _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 necessary.

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 each of the command rotational speeds _Rr and _Rl 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 _Rr and _Rl are maintained below the fifth threshold value T5.

In this manner, the controller 4 according to the present 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 a 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, 21L via the first and second motors 22R, 22L, respectively, so as to assist the movement of the bed 10 along the movement direction. At that time, the first and second motors 22R, 22L are driven, respectively, so as to realize the command rotational speeds _Rr , _Rl determined through the above-mentioned steps S5, S6, and S7. This realizes the assistance along the movement direction.

As described above, according to this embodiment, the torque (torque that tries to rotate the wheel) that caused the induced current can be estimated by detecting the induced current with the first and second current sensors SW1 and SW2. This makes it possible to estimate the accelerations a _x and a _y of the bed 10, as exemplified in step S3 of Fig. 9. Each of the accelerations a _x and a _y increases according to the external force applied by the carrier 100. Therefore, as shown in step S33 of Fig. 15, it is possible to determine whether the bed 10 has been pushed by determining whether each of the accelerations a _x and a _y is equal to or greater than a predetermined value.

Also, as shown in FIG. 15, by performing speed increase control as the second control in addition to compliance control as the first control, it is possible to not only make the bed 10 follow the bed, but also to reduce the load on the transporter 100 by the amount of the commanded rotation speed increased through the speed increase control. This makes it easier to push the bed 10, and provides the transporter 100 with an appropriate "feeling of assistance."

15, when the accelerations a _x and a _y are equal to or greater than the fourth threshold value, that is, when the bed 10 is pushed, the speed increase control is executed, thereby synchronizing the timing when the transporter 100 pushes the bed 10 with the timing when the bed 10 becomes easy to push. This allows the transporter 100 to be provided with a feeling of assistance that is neither too much nor too little. Also, by configuring the speed increase control to be executed on the condition that the bed 10 is pushed, it is possible to avoid a situation in which the transport assistance device 1 unintentionally moves on its own as a result of the speed increase control being executed when the bed 10 is not being pushed.

It is also believed that the harder the carrier 100 pushes the bed 10, the higher the detection values of the first and second rotation sensors SW3, SW4 will be. In this embodiment, as shown in steps S32 to S34 in Figures 13 and 15, the higher the detection value of the number of rotations, the stronger the thrust that assisted the movement of the bed 10. This makes it possible to realize assistance according to the magnitude of the external force, which is advantageous in making the bed 10 easier to push.

In addition, by implementing the process of step S35 in FIG. 15, when the transporter 100 lightly pushes the bed 10 or takes his/her hands off the bed 10, the movement of the bed 10 is assisted with a weaker thrust. This makes it possible to realize assistance according to the magnitude of the external force, giving the transporter a feeling of assistance that is just right, and also making it possible to prevent unintended self-propulsion of the transport assistance device 1.

Furthermore, as shown in steps S4 and S5 of FIG. 9, when the rotation speed is less than the first threshold value T1, the driving of the first and second Mecanum wheels 21R, 21L as wheels is limited. This makes it possible to execute compliance control and speed increase control only when the bed 10 is actually being transported. This contributes to improving the usability of the transport assistance device 1.

Furthermore, if the speed increase control is performed when climbing a slope, the sense of assistance is improved at the moment when the bed 1 starts to be pushed, but the sense of assistance is not improved thereafter (while the bed 1 is climbing). Therefore, as shown in steps S41 to S44 in FIG. 16, when it is determined that the bed 1 is climbing a slope, the vertical acceleration a _x referred to in the compliance control is increased, and compliance control is performed based on the increased vertical acceleration a _x '. Increasing the vertical acceleration a _x is equivalent to overestimating the external force acting on the bed 10 compared to the actual external force. Overestimating the external force realizes an assistance that exerts a thrust force greater than that which follows the movement of the bed 10. This process is performed as long as the bed 10 continues to climb a slope, so that a good sense of assistance can be continuously exerted while the bed 10 is climbing a slope.

Furthermore, if speed increase control is performed when going downhill, the bed 10 may be accelerated more than necessary, causing the bed 10 to slip out of the hands of the transported person 100. Therefore, as shown in steps S41 to S45 of Fig. 16, only compliance control is performed without increasing the vertical acceleration _ax , and speed increase control is not performed. This allows a sense of assistance appropriate for going downhill.

In addition, by implementing the safety limit control shown in FIG. 17, the command rotation speed value can be maintained below the fifth threshold value T5. This makes it possible to further improve the safety of the transport assistance device 1 compared to conventional methods.

The transport assistance device 1 according to this embodiment can also provide a lighter pressure on the transporter 100 when assisting in the movement of a heavy object such as the bed with casters 10 shown in Figures 1 and 2.

<Other embodiments>
In the above embodiment, a configuration using the first and second Mecanum wheels 21R, 21L as the wheels is disclosed, but such a configuration is not essential. The present disclosure can also be applied to wheels other than Mecanum wheels, for example, omni wheels. The number of wheels is also not limited to two. For example, when Mecanum wheels are used as in the present embodiment, the number may be four, and when omni wheels are used, the number may be three or four. In addition, the number of motors may be changed depending on the number of wheels.

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

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

1 Transport auxiliary device 4 Controller 10 Bed (object, bed with casters)
14 Caster 14F Front wheel 14B Rear wheel 21R First Mecanum wheel (wheel)
211R: First wheel body 212R: First barrel-shaped roller 21L: Second Mecanum wheel (wheel)
211L Second wheel body 212L Second barrel-shaped roller 22R First motor (motor)
22L Second motor (motor)
SW1 First current sensor (current sensor)
SW2 Second current sensor (current sensor)
SW3 1st rotation sensor (rotation sensor)
SW4 Second rotation sensor (rotation sensor)
SW5 6-axis sensor (tilt sensor)

Claims (8)

1. A transport assist device for assisting the movement of an object by an external force, comprising:
   a wheel attached to the object;
   a motor drivingly connected to the wheel;
   a current sensor for detecting an induced current flowing through the motor when the wheel rotates;
   A controller for controlling the motor,
   The controller:
   Estimating an acceleration of the object based on a detection signal of the current sensor;
   execute a first control for setting a command rotation speed of the motor so as to follow the movement of the object based on the acceleration;
   When the absolute value of the acceleration is equal to or greater than a predetermined value, a second control is executed to increase the command rotation speed set in the first control.
2. 2. The transport assist device according to claim 1,
   A rotation sensor is provided to detect the number of rotations of the wheel.
   The transport auxiliary device according to claim 1, wherein, when increasing the command rotation speed, the controller increases the command rotation speed to a greater extent as the rotation speed detected by the rotation sensor increases.
3. 2. The transport assist device according to claim 1,
   The transport auxiliary device according to claim 1, wherein the controller reduces the command rotation speed after the second control when an absolute value of the acceleration falls below the predetermined value.
4. 2. The transport assist device according to claim 1,
   A rotation sensor is provided to detect the number of rotations of the motor,
   The transport auxiliary device, wherein the controller allows the wheel to be driven when the number of rotations reaches or exceeds a predetermined number based on a detection signal from the rotation sensor.
5. 2. The transport assist device according to claim 1,
   A rotation sensor for detecting the number of rotations of the motor;
   a tilt sensor for detecting a tilt angle of a conveyance surface on which the object moves,
   The controller determines whether the conveying surface is a slope based on a detection signal from the tilt sensor,
   The controller:
   When it is determined that the conveying surface is not a slope, both of the first control and the second control are executed based on the acceleration obtained by the current sensor,
   When it is determined that the conveying surface is a slope, it is determined whether the object is ascending along the slope based on the detection signals of the rotation sensor and the inclination sensor, and when it is determined that the object is ascending, the acceleration obtained by the current sensor is increased, and the first control is executed based on the increased acceleration, and the second control is not executed.
6. 2. The transport assist device according to claim 1,
   A rotation sensor for detecting the number of rotations of the wheel;
   an inclination sensor that detects an inclination angle of a conveying surface along which the object is conveyed;
   The controller determines whether the conveying surface is a slope based on a detection signal from the tilt sensor,
   The controller:
   When it is determined that the conveying surface is not a slope, both of the first control and the second control are executed based on the acceleration obtained by the current sensor,
   When it is determined that the conveying surface is a slope, the conveying assistance device determines whether the object is descending along the slope based on the detection signals of the rotation sensor and the inclination sensor, and when it is determined that the object is descending, executes the first control based on the acceleration obtained by the current sensor and does not execute the second control.
7. 2. The transport assist device according to claim 1,
   After the second control, the controller
   If the command speed is less than a predetermined threshold, the command speed is maintained at its value;
   When the command rotational speed is equal to or greater than the threshold value, the command rotational speed is changed to the threshold value.
8. The transport auxiliary device according to any one of claims 1 to 7,
   the object is a bed with casters,
   A transport assistance device characterized in that the wheels are attached to the bottom of the castor-equipped bed.
   

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