Control method for power assist device and power assist device

Abstract

This control method is executed by a control device in a power assist device comprising: a mounting bracket having a hollow passage portion through which a handrim of a wheelchair can pass, the mounting bracket being detachably mountable to the handrim in a state where the handrim is slidable through the hollow passage portion; a drive unit having a drive roller and an electric motor that drives the drive roller in a housing supported by the mounting bracket, the drive roller being configured to be in contact with the outer peripheral surface of a wheel of the wheelchair; and the control device that controls the electric motor. The control method includes: a reference target torque calculation processing that calculates a reference target torque of the electric motor on the basis of the operation amount of the power assist device by a user of the wheelchair; and a control processing that detects a slip between the wheel and the drive roller and limits the reference target torque on the basis of the detection result.

Description

Control method for electric assist device and electric assist device

[0001] The present invention relates to a control method for an electric assist device that can be attached to a wheelchair, and to an electric assist device.

[0002] Conventionally, technologies for electrifying manual wheelchairs have been proposed. For example, JP2021-514799A discloses an electric assist device that propels a manual wheelchair by rotating rollers that contact the wheels of the manual wheelchair with an electric motor.

[0003] In the conventional technology described above, the driving force of the drive roller may not be properly transmitted to the wheelchair wheels, potentially causing slippage between the wheelchair wheels and the drive roller. In this case, the wheelchair's maneuverability will be reduced.

[0004] The present invention aims to prevent slippage between the wheels and drive rollers of a wheelchair and to improve the maneuverability of the wheelchair.

[0005] One aspect of the present invention relates to an electric assist device comprising: a mounting bracket detachably attached to a handrim having a hollow passage through which a wheelchair handrim can pass, such that the handrim can slide within the hollow passage; a drive unit having a drive roller in contact with the outer surface of a wheelchair wheel and an electric motor for driving the drive roller, all housed in a housing supported by the mounting bracket; and a control device for controlling the electric motor. The control method is performed by the control device. This control method includes a reference target torque calculation process that calculates a reference target torque of the electric motor based on the amount of operation of the electric assist device by the wheelchair user, and a control process that detects slip between the wheel and the drive roller and limits the reference target torque based on the detection result.

[0006] Figure 1 is a side view showing the electric assist device mounted on the wheel of a manual wheelchair. Figure 2 is a top view of the electric assist device mounted on the wheel. Figure 3 is a front view of the electric assist device mounted on the wheel. Figure 4 is a side view showing an enlarged view of the main part of Figure 1. Figure 5 is a front view showing an enlarged view of the main part of Figure 3. Figure 6 is a cross-sectional view along line A-A in Figure 4. Figure 7 is an explanatory diagram of the electric motor and drive roller. Figure 8 is an explanatory diagram of the reduction gear. Figure 9 is a side view of the mounting bracket and battery unit excluding the drive unit. Figure 10 is a top view of the battery unit. Figure 11 is a front view of the battery unit. Figure 12 is a cross-sectional view along line B-B in Figure 10. Figure 13 is a perspective view showing the drive switch provided in the drive unit. Figure 14 is a block diagram showing an example of the internal configuration of the electric assist device. Figure 15 is a diagram showing an example of providing a load cell to the electric assist device. Figure 16 is a flowchart showing an example of driving control processing. Figure 17 is a simplified diagram showing the relationship between the wheels and the drive rollers. Figure 18 is a flowchart showing an example of the driving control process. Figure 19 is a flowchart showing an example of the driving control process. Figure 20 is a top view showing the external configuration of the manual wheelchair. Figure 21 is a flowchart showing an example of the driving control process. Figure 22 is a top view showing the external configuration of the manual wheelchair. Figure 23 is a flowchart showing an example of the driving control process. Figure 24 is a top view showing the external configuration of the manual wheelchair. Figure 25 is a top view showing the external configuration of the manual wheelchair.

[0007] Embodiments of the present invention will be described below with reference to the attached drawings.

[0008] Figures 1 to 3 show an electric assist device 1 of one embodiment mounted on the wheel 2 of a manual wheelchair. The entire manual wheelchair is not shown, and only one wheel 2 (for example, the right side), which is the so-called rear wheel, is shown in Figures 1 to 3. The manual wheelchair has a general configuration, with a seat section where the user sits between the pair of wheels 2, and a pair of small-diameter front wheels at the front of the frame that supports the seat section and the wheels 2.

[0009] The wheel 2 is supported so as to be rotatable about the axle 3, and a handrim 5 for the user to rotate the wheel 2 with their own hand is provided outside the wheel 2. The handrim 5 is formed by connecting metal tubes or metal bars with a circular cross-section in an annular shape, and is arranged parallel to the wheel 2 slightly outside the wheel 2 and is configured to have a slightly smaller diameter than the outer diameter of the wheel 2. And it is fixed to the wheel 2 via a plurality of connecting pieces 6 provided at equal angular intervals.

[0010] The electric assist device 1 of one embodiment is configured to drive the adjacent wheel 2 attached to the handrim 5, and is provided for each of the left and right wheels 2. The figure illustrates the electric assist device 1 for the right wheel 2. The electric assist devices 1 provided on the left and right in this way are not fixed in the circumferential direction in the state of being mounted on the handrim 5, and the user sitting on the seat part supports the electric assist devices 1 in the circumferential direction with both hands. That is, when the electric assist device 1 drives the wheel 2, the user supports the reaction force acting on the electric assist device 1. In FIGS. 1 to 3, on the premise that the user is supporting by hand, the electric assist device 1 is drawn at the uppermost part of the wheel 2.

[0011] In the following description of the electric assist device 1, following the concepts of front-rear, left-right, and up-down of a manual wheelchair, the X direction shown in FIGS. 1 and 2 will be referred to as the "front-rear" direction, the Y direction as the "left-right" direction or "width" direction, and the Z direction as the "up-down" direction. Also, it is assumed that the electric assist device 1 is located at the uppermost part of the wheel 2 as shown in FIG. 1.

[0012] As shown in Figures 4 and 5, the electric assist device 1 of one embodiment comprises a mounting bracket 11 for attaching the entire electric assist device 1 to the handrim 5, a drive unit 12 for driving the wheel 2, and a battery unit 13 that serves as a power source, with these three components integrated into a single unit. The drive unit 12 has a drive unit housing 31 made of rigid synthetic resin as its first housing. The drive unit housing 31 is a rectangular box shape with relatively similar dimensions in the front-rear direction and left-right direction, and is located on the outer circumference side of the handrim 5. The battery unit 13 has a battery unit housing 32, also made of rigid synthetic resin, as its second housing. The battery unit housing 32 is an elongated box shape in the front-rear direction, and is located on the inner circumference side of the handrim 5.

[0013] As shown in Figures 9 to 12, the mounting bracket 11 is mainly composed of a tubular portion 16 with a circular cross-section that forms a hollow passage 15 curved in an arc shape through which the handrim 5 can pass. The tubular portion 16 is made of a hard synthetic resin with appropriate elasticity, and as shown in Figure 9, it extends forward and backward while curving in an arc shape with a curvature corresponding to the curvature of the handrim 5, and as shown in Figure 11, it has a roughly C-shaped cross-section with an open side portion facing the wheel 2. Because the tubular portion 16 has a roughly C-shaped cross-section, it is possible to attach the tubular portion 16 to the handrim 5 by utilizing the elasticity of the resin material. In the mounted state, the opening width of the side portion is smaller than the diameter of the handrim 5, so the mounting bracket 11 will not naturally fall off the handrim 5. The inner diameter of the tubular section 16, which has a roughly C-shaped cross-section, that is, the diameter of the hollow passage section 15, is set to be slightly larger than the diameter of the handrim 5, allowing the handrim 5 to pass through the hollow passage section 15 in the circumferential direction. In other words, the mounting bracket 11 is configured to move freely in the circumferential direction relative to the handrim 5.

[0014] As shown in FIGS. 9 and 10, a notch 17 is provided over a relatively large length range at the central portion of the tubular portion 16 in the longitudinal direction (front-rear direction) so as to avoid interference with the drive unit housing 31. In the range of this notch 17, the tubular portion 16 has a shape in which the upper portion is cut off so that only the lower portion (inner peripheral side portion) in the C-shaped cross section remains. The formation range of this notch 17 generally corresponds to the front-rear dimension of the drive unit housing 31. By providing the notch 17 in this way, the portion press-fitted into the handrim 5 is divided into two, so that the press-fitting into the handrim 5 becomes easy and the sliding resistance generated between the handrim 5 during running is reduced. In addition, it becomes possible to lower the height position of the drive unit 12.

[0015] At positions adjacent to both the front and rear ends of the notch 17 of the tubular portion 16, a pair of drive unit mounting portions 18 for supporting the drive unit 12 are provided. As shown in FIG. 11, each drive unit mounting portion 18 is provided with a circular shaft support hole 20, and each of a pair of cylindrical boss portions 33 (see FIG. 5) formed on the drive unit housing 31 is configured to be fitted into the shaft support hole 20 of the pair of drive unit mounting portions 18, respectively. Specifically, each drive unit mounting portion 18 is composed of a fixing piece 18a integrally formed with the tubular portion 16 and a cap 18b fixed to the fixing piece 18a by a screw 19 (see FIG. 9). By tightening the screw 19 after adjusting the angle of the drive unit 12 with respect to the mounting bracket 11, the boss portion 33 is fixed. That is, the inner diameter of the shaft support hole 20 is slightly smaller than the outer diameter of the boss portion 33. The pair of boss portions 33 and the corresponding pair of shaft support holes 20 are configured around a single common center line along the tangential direction of the handrim 5. Therefore, in a state where the screw 19 is loosened, the angle of the drive unit 12 can be adjusted with the above center line as the rotation center.

[0016] As shown in Figure 6, the drive unit 12 has a configuration in which a pair of electric motors 35, a drive roller 36, and a reduction gear 37 between them are housed in a drive unit housing 31. As shown in Figures 7 and 8, the pair of electric motors 35 are arranged in a front-to-back arrangement, and one drive roller 36 rotates via a reduction gear 37 consisting of the pinion 37a of each electric motor 35 and a relatively large-diameter gear 37b on the drive roller 36 side. As shown in Figure 6, the drive roller 36 is in contact with the outer circumferential surface of the wheel 2, thereby transmitting rotational torque from the drive roller 36 to the wheel 2. As mentioned above, the drive unit 12 is supported with respect to the mounting bracket 11 so that its angle can be adjusted, and by adjusting the angle in accordance with the actual position of the outer circumferential surface of the wheel 2 relative to the handrim 5, it is possible to reliably ensure that the drive roller 36 is in contact with the outer circumferential surface of the wheel 2.

[0017] The drive roller 36 is made of hard synthetic resin or metal, and its outer surface is treated with an appropriate anti-slip finish. As shown in Figure 6, both ends of the drive roller 36 are rotatably supported by the drive unit housing 31 via bearing members.

[0018] In the drive unit 12, as shown in Figure 6, the electric motor 35, the drive roller 36, and the reduction gear 37 between them are arranged so that their respective axes of rotation are parallel to each other, and the electric motor 35 and the drive roller 36 are located on opposite sides of the reduction gear 37. Furthermore, each axis of rotation (for example, the centerline 36a of the axis of rotation of the drive roller 36 is shown in Figure 6) is inclined so that the outer side in the width direction of the manual wheelchair is relatively lower. For example, it is inclined at about 30 to 60° with respect to the horizontal plane. This inclination of the axis of rotation of the drive unit 12 makes it possible to relatively reduce both the upward and lateral protrusion of the drive unit 12 from the wheels 2 of the manual wheelchair. In other words, if the axis of rotation were horizontal, the lateral protrusion of the drive unit 12 would be large. Also, if the electric motor 35 and the drive roller 36 were not arranged in series but stacked vertically, the upward protrusion would be large.

[0019] The uppermost part of the drive unit housing 31 covering the drive roller 36 has a generally flat shape that follows a horizontal plane, as shown in Figure 6. Also, as shown in Figures 2 and 4, a part of the front end of the drive unit housing 31 protrudes forward of the drive roller 36, forming a grip portion 31a that is easy for the user to hold. As shown in Figure 13, a drive SW (switch) 38 is provided on the side of the grip portion 31a. In one embodiment, the drive SW 38 is of the push-button type and is positioned so that it can be pressed by the thumb of the hand resting on the grip portion 31a. Furthermore, as will be described later, the drive unit 12 is equipped with a gravity sensor (for example, a 6-axis gravity sensor 54) for forward and reverse switching at an appropriate position.

[0020] As shown in Figures 9 to 12, the battery unit 13, which has a battery unit housing 32, is supported by being suspended from a mounting bracket 11, which mainly consists of an arc-shaped tubular portion 16. The battery unit housing 32 has a rectangular parallelepiped shape that is long in the front-to-back direction, with a front-to-back length dimension corresponding to the chord of the arc of the tubular portion 16. Inside it, as shown in Figures 6 and 12, a plurality of cylindrical batteries 39 are housed, arranged along the longitudinal direction of the battery unit housing 32. In addition, a circuit board 40, which is divided into several parts, is housed inside the battery unit housing 32. As shown in Figure 12, the battery unit housing 32 is equipped with an openable and closable battery cover 41 at the bottom for replacing the batteries 39.

[0021] As shown in Figures 11 and 6, the battery unit housing 32 (battery cover 41) has two projections 42 that extend long in the front-to-back direction at its bottom. These two projections 42 allow the electric assist device 1, which has been removed from the manual wheelchair, to stand upright on the floor without tipping over.

[0022] As shown in Figures 12 and 9, the mounting bracket 11 and the battery unit housing 32 are connected to each other via a pair of rail sections 44 so as to be slidable in the left-right direction (i.e., in the axial direction of the wheel 2). The rail section 44 consists of a convex rail section 44a molded as part of a synthetic resin molded product on the battery unit housing 32 side to have a substantially T-shaped cross-section, and a concave rail section 44b having a substantially T-shaped groove that slidably engages with the convex rail section 44a. As shown in Figure 12, the concave rail section 44b is molded integrally with the tubular section 16 of the mounting bracket 11 and is molded as a highly rigid part that is thicker than the wall thickness of the tubular section 16. As shown in Figure 9, the pair of rail sections 44 are located in front of and behind, respectively, a pair of drive unit mounting sections 18 that support the drive unit housing 31. The mounting bracket 11 and the battery unit housing 32 do not interfere with each other in areas other than the pair of rail sections 44.

[0023] As described above, the battery unit housing 32 is supported by the mounting bracket 11 via a pair of rail sections 44, allowing for adjustment of the position (left-right position) of the battery unit housing 32 relative to the mounting bracket 11 to match the distance between the handrim 5 and the wheel 2. This allows for adjustment of the clearance between the battery unit housing 32 and the wheel 2, for example. There are no special fixing means between the battery unit housing 32, whose position can be adjusted by the rail sections 44, and the mounting bracket 11; the position of the battery unit housing 32 is maintained by appropriate friction in the synthetic resin rail sections 44.

[0024] Figures 10 and 11 show the state when the rail section 44 is in the reference position. In this state, the tubular section 16 of the mounting bracket 11 (in other words, the handrim 5) is located in the center of the left-right dimension of the battery unit housing 32. That is, the amount of protrusion of the battery unit housing 32 from the handrim 5 in the left-right direction is approximately equal on both sides. Also, as shown in Figure 6, when the battery unit housing 32 is mounted on the manual wheelchair via the mounting bracket 11 together with the drive unit 12, the battery unit housing 32 does not protrude beyond the end of the drive unit housing 31 on the electric motor 35 side in the left-right direction. That is, the maximum amount of protrusion of the electric assist device 1 in the left-right direction is determined by the upper corner 31b (corresponding to the outer end) of the drive unit housing 31, and the amount of protrusion of the battery unit housing 32 in the left-right direction is smaller than this maximum amount of protrusion. In other words, when the electric assist device 1 is projected along the radial direction of the handrim 5 as shown in Figure 2, the amount of protrusion of the battery unit housing 32 is smaller than the maximum amount of protrusion of the outer end of the drive unit housing 31 in the left-right direction of the manual wheelchair. Such lateral protrusion is an important factor, for example, when passing through a relatively narrow corridor. Although not shown in the diagram, the battery unit 13 and the drive unit 12 are connected by a harness with detachable connectors at its ends, and power is supplied to the drive unit 12 through this harness.

[0025] In the electric assist device 1 of the embodiment configured as described above, the drive unit 12, mounting bracket 11, and battery unit 13 are integrated into one unit. Installation of the entire device is completed simply by attaching the mounting bracket 11 to the handrim 5 of a manual wheelchair while the unit remains integrated. Conversely, removal is completed by pulling the tubular portion 16 of the mounting bracket 11 off the handrim 5. Therefore, a simple electrification of a manual wheelchair can be easily achieved. The integrated electric assist device 1 contains all the elements necessary for operation, and there is no need to attach other parts to other parts of the manual wheelchair.

[0026] Furthermore, since the drive unit 12 is located on the outer circumference, or upper part, of the handrim 5, while the battery unit 13 is located on the inner circumference, the overall design can be made compact. In other words, the battery unit 13 can be placed using the empty space on the inner circumference of the handrim 5.

[0027] Furthermore, while the drive unit 12 rests on top of the mounting bracket 11, the battery unit 13 is suspended downward from the mounting bracket 11. Since the weight of the battery unit 13, including the battery 39, is relatively large, when the electric assist device 1 is attached to the handrim 5, the center of gravity of the electric assist device 1 is located on the inner circumference side of the handrim 5 (i.e., below the handrim 5 at the notch 17) due to the weight of the battery unit 13. As a result, the posture of the electric assist device 1 around the handrim 5 is stable, making it easy for the user to handle. In other words, the battery unit 13 also functions as a counterweight to stabilize the posture of the electric assist device 1 on the handrim 5.

[0028] Furthermore, as described above, the electric assist device 1, which consists of a drive unit 12, a mounting bracket 11, and a battery unit 13, allows for the attachment and detachment of the drive unit 12 and the battery unit 13 to the mounting bracket 11. Therefore, if the diameter (i.e., curvature) of the handrim 5 of a manual wheelchair varies, by preparing several mounting brackets 11 having tubular sections 16 with different curvatures, it is possible to accommodate various manual wheelchairs by simply changing the mounting bracket 11.

[0029] Next, the operation of a manual wheelchair equipped with the above-mentioned electric assist device 1 will be described. As mentioned above, the electric assist device 1 is attached to each of the left and right wheels 2 of the manual wheelchair, and is operated by a user seated in the seat with both hands placed on the left and right electric assist devices 1. For example, with the top of the wheel 2 as the reference position, if the user presses the drive switch 38 and tilts the electric assist device 1 forward, the drive roller 36 of the drive unit 12 drives the wheel 2 in the forward direction. If the left and right electric assist devices 1 are operated in the same way, the manual wheelchair will move forward. The fact that the electric assist device 1 has been tilted forward by the user is detected by a gravity sensor (for example, a 6-axis gravity sensor 54) built into the drive unit 12. Conversely, if the user presses the drive switch 38 and tilts the electric assist device 1 backward, the wheel 2 will be driven in the reverse direction. Therefore, if the left and right electric assist devices 1 are tilted backward simultaneously, the manual wheelchair will move backward. Furthermore, by operating one of the left and right electric assist devices 1 in the forward direction and the other in the reverse direction, the manual wheelchair can be turned around.

[0030] In the above explanation, the uppermost part of the wheel 2 was described as the reference position of the electric assist device 1. However, it is also possible to set a reference position at an angle other than the uppermost part (an angle tilted at an appropriate angle forward or backward). Even if the reference position is set at an appropriate angle, the gravity sensor can detect whether the electric assist device 1 has been tilted forward or backward from this reference position. Furthermore, the amount of displacement of the electric assist device 1 due to user operation (how much it has been tilted) can also be detected by the gravity sensor, and in one embodiment, the larger this displacement, the greater the torque with which the wheel 2 is driven.

[0031] [Example of internal configuration of electric assist device] Figure 14 is a block diagram showing an example of the internal configuration of the electric assist device 1.

[0032] The electric assist device 1 comprises an electric motor 35, a drive roller 36, a reduction gear 37, a drive switch 38, a battery 39, a roller 51, rotation speed sensors 52 and 53, a 6-axis gravity sensor 54, a load cell 55, an operation switch 56, a power switch 57, a light-emitting unit 58, a voltage sensor 59, a driver 60, a current sensor 61, a communication unit 62, a display unit 63, and a control device 70. The drive roller 36 and roller 51 are rollers installed on the wheels 2 of a manual wheelchair. The electric motor 35, drive roller 36, reduction gear 37, drive switch 38, and battery 48 correspond to the parts described above. These parts are just examples, and as will be described later, they can be omitted or other parts added as needed depending on the required processing.

[0033] The operation switch 56 acquires an operation signal corresponding to user operation and outputs it to the control device 70. For example, the operation switch 56 is used to change the zero point or change the control variable, etc.

[0034] Roller 51 is a roller that contacts the wheel 2 of the manual wheelchair and is connected to the rotation speed sensor 52.

[0035] The rotation speed sensor 52 is an encoder equipped with a roller that acquires the rotation speed of the wheel 2. For example, a roller 51 can be provided so as to be in contact with the wheel 2, and the rotation speed of the wheel 2 can be acquired by pressing the roller 51 against the wheel 2. Furthermore, the wheel speed of the wheel 2 can be calculated based on the rotation speed acquired by the rotation speed sensor 52. Alternatively, instead of providing the rotation speed sensor 52, a Hall element can be provided at a position where the spokes of the wheel 2 can be read (for example, at the position of the battery unit 13), and the rotation speed of the wheel 2 can be acquired based on the number of spokes of the wheel 2 acquired by this Hall element.

[0036] The rotation speed sensor 53 is an encoder that acquires the motor rotation speed of the electric motor 35. In Figure 14, an example is shown in which the rotation speed sensor 53 capable of measuring the rotation speed of the electric motor 35 is installed on the electric motor 35, but the rotation speed sensor 53 may also be installed in any path from the electric motor 35 to the drive roller 36.

[0037] The 6-axis gravity sensor 54 is a 6-axis gyroscope that acquires the tilt of the electric assist device 1.

[0038] The load cell 55 acquires the pressing force applied by the user to move the manual wheelchair. The load cell 55 will be described in detail with reference to Figure 15.

[0039] The drive switch 38 receives user input to move the manual wheelchair and outputs an operation signal corresponding to that user input to the control device 70. In other words, the drive switch 38 acquires the user's intention to drive the manual wheelchair.

[0040] The power switch SW57 is a switch for turning on the power to the electric assist device 1.

[0041] The light-emitting unit 58 is a light-emitting unit that indicates that the power supply of the electric assist device 1 is turned on. For example, an LED (light-emitting diode) can be used.

[0042] The voltage sensor 59 is a sensor that measures the voltage of the electricity supplied from the battery 39.

[0043] The driver 60 is a motor driver that operates the electric motor 35 based on the PWM signal transmitted from the control device 70.

[0044] The current sensor 61 is a sensor that acquires the motor current in order to control the torque of the electric motor 35.

[0045] The communication unit 62 is a communication device that communicates with the electric assist device 1, which is attached to the other wheel of the two left and right wheels. For example, each communication is performed using wired communication or wireless communication.

[0046] The display unit 63 is a display device that displays the setting content signals and status values ​​of the electric assist device 1.

[0047] The control device 70 controls each part of the electric assist device 1 based on a control program stored in a storage device (not shown). The control device 70 is implemented by a processing unit such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) and a storage device. This storage device is a storage medium that stores various kinds of information. For example, the storage device stores various kinds of information (such as control programs) that are necessary for the control device 70 to perform various processing tasks. The control device 70 also stores various kinds of information acquired via the communication unit 62. As the storage device, for example, ROM (Read Only Memory), RAM (Random Access Memory), SRAM (Static Random Access Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof can be used.

[0048] [Example of limiting the reference target torque using the contact force between the wheel and the drive roller] As described above, the electric assist device 1 rotates the wheel 2 of the manual wheelchair by bringing the drive roller 36, which is connected to the electric motor 35, into contact with the wheel 2 of the manual wheelchair. However, if the driving force of the drive roller 36 is not properly transmitted to the wheel 2, there is a risk of slippage between the wheel 2 and the drive roller 36. In this case, the operability of the manual wheelchair may be reduced. Therefore, in this embodiment, an example is shown in which slippage between the wheel 2 and the drive roller 36 of the manual wheelchair is prevented and the operability of the manual wheelchair is improved. First, an example is shown in which the reference target torque is limited using the contact force between the wheel 2 and the drive roller 36 to prevent slippage between the wheel 2 and the drive roller 36 of the manual wheelchair.

[0049] [Example of installation of equipment for measuring contact force] Figure 15 shows an example of installing a load cell 55 in the electric assist device 1. In Figure 15, the part where the load cell 55 is installed is enclosed by a dotted circle DE1 in a configuration diagram similar to that of the electric assist device 1 shown in Figure 5.

[0050] The load cell 55 is a sensor that converts the magnitude of the force applied to the sensor part into an electrical signal and measures the force (such as load and mass) applied to an object. For example, as shown in FIG. 15, in order to measure the pressing force for pressing the drive roller 36 against the wheel 2, it is possible to provide the load cell 55 at the part held by the user's hand. Thereby, the pressing force F in the downward direction of the gravitational direction can be directly measured. This pressing force F can also be grasped as the reaction force F of the drive roller 36 with respect to the wheel 2. Further, the direction in which the drive roller 36 presses against the wheel 2 is inclined by an angle θ from the gravitational direction. Note that the angle θ is the mounting angle of the drive roller 36.

[0051] Here, when the pressing force is F and the mounting angle is θ, the contact force between the wheel 2 and the drive roller 36 is Fcosθ.

[0052] Further, when the friction coefficient between the wheel 2 and the drive roller 36 is μ, the frictional force F between the wheel 2 and the drive roller 36 ｌｉｍ can be obtained by the following Equation 1. F ｌｉｍ = μFcosθ Equation 1

[0053] Further, when the radius of the drive roller 36 is r ｒ the limiting torque Tm ｌｉｍ can be obtained by the following Equation 2. Note that the limiting torque Tm ｌｉｍ is a value for limiting the reference target torque Tm ｔａｒ . The reference target torque will be described in detail with reference to FIG. 16. Tm ｌｉｍ = F ｌｉｍ × r ｒ Equation 2

[0054] [Example of Other Devices for Measuring Contact Force] Also, it is possible to measure the grounding force of the drive roller 36 installed on the wheel 2 by attaching a strain gauge to the boss portion 33 fitted into the circular shaft support hole 20. Thus, the contact force Fcosθ can also be measured using a strain gauge.

[0055] [Example of operation of electric assist device] Figure 16 is a flowchart showing an example of the driving control process in the electric assist device 1. This driving control process is executed by the control device 70 (see Figure 14) based on a program stored in the storage unit (not shown) of the control device 70. This driving control process will be explained with reference to Figures 1 to 15 as appropriate.

[0056] In step S101, the control device 70 reads the state of the drive switch 38, and in step S102, it determines whether the drive switch 38 is ON (pressed). If the drive switch 38 is OFF, the process proceeds to step S113, and the reference target torque is set to 0. On the other hand, if the drive switch 38 is ON, the process proceeds to step S103.

[0057] In step S103, the control device 70 reads the data from the 6-axis gravity sensor 54, and in step S104, calculates the tilt angle of the electric assist device 1 (tilt angle from the reference position). Here, the reference position may be set in advance, or it may be set based on the timing when the drive switch 38 is turned ON. In other words, the reference position can be set arbitrarily.

[0058] In step S105, the control device 70 controls the reference target torque Tm based on the inclination angle calculated in step S104. ｔａｒ Determine the following: the tilt angle and the reference target torque Tm. ｔａｒ The relationship between the two can be set in advance. Here, the tilt angle of the electric assist device 1 changes according to the amount of movement of the electric assist device 1 from its reference position. That is, the control device 70 sets the reference target torque Tm of the electric motor 35 based on the amount of operation of the electric assist device 1 by the user of the manual wheelchair. ｔａｒ This is calculated. In this way, the amount of movement of the electric assist device 1 can be used as the manipulated amount.

[0059] In step S106, the control device 70 controls the reference target torque Tm by the rate limiter. ｔａｒ The rate of change is limited to a certain upper limit. For example, if the inclination angle calculated in step S104 is large, the reference target torque Tm ｔａｒA large value is set as the reference target torque Tm. In this case, the reference target torque Tm is set as the large value. ｔａｒ Using this may increase the acceleration of wheel 2, potentially causing the manual wheelchair to move suddenly. Therefore, to prevent the manual wheelchair from moving suddenly, for example, a reference target torque Tm ｔａｒ If a large value is set, the reference target torque Tm will be set until that value is reached. ｔａｒ The rate of change of the reference target torque Tm is gradually increased, and this rate of change is limited to a certain upper limit. ｔａｒ If the upper limit is restricted, then from this point onward, the reference target torque Tm will be limited by that upper limit. ｔａｒ Use this instead.

[0060] In step S107, the control device 70 calculates the contact force Fcosθ between the wheel 2 and the drive roller 36 based on the pressing force F (see Figure 15) measured by the load cell 55. As described above, instead of using the load cell 55, the contact force Fcosθ may be measured using strain gauges.

[0061] In step S108, the control device 70 sets the limiting torque Tm based on the contact force Fcosθ calculated in step S107. ｌｉｍ The limiting torque Tm is calculated using equations 1 and 2 as described above. ｌｉｍ It is possible to calculate this.

[0062] In step S109, the control device 70 controls the reference target torque Tm determined in step S105. ｔａｒ The value is the limiting torque Tm calculated in step S108. ｌｉｍ Determine whether the value is greater than or equal to the reference target torque Tm. ｔａｒ The value of the limiting torque Tm ｌｉｍ If the value is greater than or equal to the specified value, proceed to step S110. Meanwhile, the reference target torque Tm ｔａｒ The value of the limiting torque Tm ｌｉｍ If the value is less than the reference target torque Tm, proceed to step S111. ｔａｒ This is set as the final target torque.

[0063] In step S110, the control device 70 controls the reference target torque Tm determined in step S105. ｔａｒ Instead, the limiting torque Tm calculated in step S108 ｌｉｍ The setting is to use the following: that is, the limiting torque Tm ｌｉｍ This is set as the final target torque.

[0064] In step S111, the control device 70 calculates the ON duty cycle for PWM control of the electric motor 35 based on the final target torque. As described above, the reference target torque Tm ｔａｒ The value of the limiting torque Tm ｌｉｍ If the value is greater than or equal to the limiting torque Tm, the final target torque will be set to the limiting torque Tm. ｌｉｍ The reference target torque Tm is set. ｔａｒ The value of the limiting torque Tm ｌｉｍ If the value is less than the reference target torque Tm ｔａｒ This is set as the final target torque.

[0065] In step S112, the control device 70 outputs a drive signal to the driver 60 according to the ON duty cycle calculated in step S111, and controls the drive torque of the electric motor 35.

[0066] Thus, the limiting torque Tm is based on the contact force Fcosθ. ｌｉｍ Calculate the reference target torque Tm ｔａｒ By limiting this, slip between the wheel 2 and the drive roller 36 can be suppressed, improving operability. Furthermore, because it can be controlled in a feedforward manner, it can be controlled relatively easily.

[0067] [Example of limiting the reference target torque using the rotational acceleration of the drive roller and the predicted acceleration of the wheel] Next, an example of limiting the reference target torque using the rotational acceleration of the drive roller 36 and the predicted acceleration of the wheel 2 of the manual wheelchair is shown. Here, an example of limiting the reference target torque is shown using the relationship between the predicted acceleration of the wheel 2 of the manual wheelchair (rotational acceleration of the wheel 2), which can be calculated based on the reference target torque, and the rotational acceleration of the drive roller 36, which is calculated based on the actual rotational speed of the electric motor 35. For example, if the predicted rotational acceleration of the wheel 2 is greater than or equal to the rotational acceleration of the drive roller 36, it is considered that slip may occur between the wheel 2 and the drive roller 36. In this case, the reference target torque is limited.

[0068] [Example of the relationship between the wheel and the drive roller] Figure 17 is a simplified diagram showing the relationship between the wheel 2 and the drive roller 36. In Figure 17, the radius of the drive roller 36 is r ｒ Let the radius of wheel 2 be r. ｔ Here is an example.

[0069] The rotational speed ωm of the drive roller 36 can be calculated based on the rotational speed of the electric motor 35 measured by the rotational speed sensor 53 and the gear ratio of the reduction gear 37. Furthermore, the rotational acceleration of the drive roller 36 can be calculated based on the rotational speed ωm of the drive roller 36. For example, the rotational acceleration ωm of the drive roller 36 can be calculated using the following equation 3.

[0070]

[0071] Furthermore, the actual torque of the electric motor 35 is Tm ａｃｔ Assuming this is the case, the predicted torque Tc of wheel 2 can be calculated, for example, using the following equation 4.

[0072]

[0073] Furthermore, if the total inertia of a manual wheelchair is I, the predicted rotational acceleration ωc_pre of the wheels of the manual wheelchair can be calculated, for example, using the following equation 5.

[0074]

[0075] [Example of operation of electric assist device] Figure 18 is a flowchart showing an example of the driving control process in the electric assist device 1. This driving control process is executed by the control device 70 (see Figure 14) based on a program stored in the storage unit (not shown) of the control device 70. This driving control process will be explained with reference to Figures 1 to 17 as appropriate.

[0076] Note that steps S101 to S106 and S111 to S113 are the same as the steps S101 to S106 and S111 to S113 shown in Figure 16. Therefore, in Figure 18, the same reference numerals are used for the processes that are common to Figure 16, and their descriptions are omitted.

[0077] In step S121, the control device 70 calculates the rotational acceleration of the drive roller 36 based on the rotational speed of the electric motor 35 measured by the rotational speed sensor 53. For example, the rotational acceleration of the drive roller 36 can be calculated using the above-described equation 3.

[0078] In step S122, the control device 70 controls the reference target torque Tm determined in step S105. ｔａｒ (or, Tm ａｃｔ Based on the above, the accelerating wheel acceleration (rotational acceleration) of the manual wheelchair's wheel 2 is calculated. For example, the accelerating wheel acceleration of the manual wheelchair's wheel 2 can be calculated using equations 4 and 5 described above.

[0079] In step S123, the control device 70 determines whether the accelerating wheel acceleration of the wheel 2 calculated in step S122 is less than the rotational acceleration of the drive roller 36 calculated in step S121. If the accelerating wheel acceleration of the wheel 2 is greater than or equal to the rotational acceleration of the drive roller 36, there is a possibility of slippage between the wheel 2 and the drive roller 36, so the process proceeds to step S124. On the other hand, if the accelerating wheel acceleration of the wheel 2 is less than the rotational acceleration of the drive roller 36, there is a low possibility of slippage between the wheel 2 and the drive roller 36, so the process proceeds to step S111.

[0080] In step S124, the control device 70 controls the reference target torque Tm determined in step S105.ｔａｒ The final target torque is set by limiting it to a certain value. Here, the limiting value is, for example, the reference target torque Tm. ｔａｒ It is possible to sequentially set values ​​by decreasing the value by α [%] each time. Alternatively, the reduced value may be fixed when the slip between the wheel 2 and the drive roller 36 becomes minimal.

[0081] Here, various conditions can be assumed for slip to occur between the wheel 2 and the drive roller 36. For example, slip may occur due to a large reference target torque, but it is also possible that slip may occur due to insufficient pressure applied by the user. Furthermore, even with the same pressure, slip may occur when the manual wheelchair is traveling on a slope. For this reason, it is difficult to set a value that will not cause slip when the conditions are unknown. Therefore, values ​​are sequentially set by decreasing them by α [%] each time, and the reference target torque Tm is set accordingly. ｔａｒ It is preferable to use a control method that gradually reduces the value.

[0082] For example, α can be set to a value of approximately 10-20%. Note that α can be set appropriately based on experiments or simulations. Furthermore, if the user's actions are fixed or increasing, this restriction may be released after a specified period of time has elapsed. This restriction may also be released if the user performs a reset operation.

[0083] In this way, the reference target torque Tm is determined based on the rotational acceleration of the drive roller 36 and the accelerating wheel acceleration of the manual wheelchair's wheels 2. ｔａｒ By limiting this, slip between the wheel 2 and the drive roller 36 can be suppressed, improving operability. Furthermore, because it can be controlled in a feedback manner, it can also respond to changes in the coefficient of friction between the wheel 2 and the drive roller 36. In addition, for example, since the rotation speed sensor 53 is often easier to install than the load cell 55, the electric assist device 1 that performs the driving control processing shown in Figure 18 can be manufactured at a lower cost than the electric assist device 1 that performs the driving control processing shown in Figure 16.

[0084] [Example of limiting the reference target torque using the slip ratio between the wheel and the drive roller] Next, an example of limiting the reference target torque using the slip ratio between the wheel 2 and the drive roller 36 will be described. In this example, the slip ratio between the wheel 2 and the drive roller 36 is calculated and used using the rotational speeds measured by a rotational speed sensor 52 that measures the rotational speed of the roller 51 in contact with the wheel 2, and a rotational speed sensor 53 that measures the rotational speed of the electric motor 35. For example, if the drive roller 36 is commanding torque to increase the rotation in the direction in which the wheel 2 is rotating (including the stopped state), the slip ratio on the drive side can be used. On the other hand, if the drive roller 36 is commanding torque to decrease the rotation in the direction in which the wheel 2 is rotating, the slip ratio on the braking side can be used.

[0085] For example, the rotational speed of the drive roller 36 is ω ｒ Let the rotation speed of wheel 2 be ω ｃ In this case, the slip ratio r of the wheel 2 relative to the drive roller 36 is ｓｌｉｐ１ This can be calculated using the following equation 6. As described above, the radius of the drive roller 36 is r ｒ Let the radius of wheel 2 be r. ｔ The slip ratio r calculated using Equation 6 is as follows. ｓｌｉｐ１ This can also be understood as the slip ratio of the drive side.

[0086]

[0087] Also, the rotational speed of the drive roller 36 is ω ｒ Let the rotation speed of wheel 2 be ω ｃ In this case, the slip ratio r of the drive roller 36 relative to the wheel 2 ｓｌｉｐ２ The slip ratio r calculated using Equation 7 can be calculated using the following equation 7. ｓｌｉｐ２ This can also be understood as the slip ratio on the braking side.

[0088]

[0089] [Example of operation of electric assist device] Figure 19 is a flowchart showing an example of the driving control process in the electric assist device 1. This driving control process is executed by the control device 70 (see Figure 14) based on a program stored in the storage unit (not shown) of the control device 70. This driving control process will be explained with reference to Figures 1 to 18 as appropriate.

[0090] Note that steps S101 to S106 and S111 to S113 are the same as the steps S101 to S106 and S111 to S113 shown in Figure 16. Therefore, in Figure 19, the same reference numerals are used for the processes that are common to Figure 16, and their descriptions are omitted.

[0091] In step S131, the control device 70 acquires the rotational speed of the electric motor 35 measured by the rotational speed sensor 53 and the rotational speed of the wheel 2 measured by the rotational speed sensor 52. The control device 70 can also calculate the rotational speed of the drive roller 36 based on the rotational speed of the electric motor 35 and the gear ratio of the reduction gear 37.

[0092] In step S132, the control device 70 calculates the slip ratio between the wheel 2 and the drive roller 36 based on the rotational speed of the drive roller 36 and the rotational speed of the wheel 2 obtained in step S131. For example, the slip ratio can be calculated using the above-mentioned equations 6 and 7. For example, if the drive roller 36 is commanded to apply torque in the direction that increases the rotation of the wheel 2 (including the stopped state), the slip ratio r on the drive side can be calculated using equation 6. ｓｌｉｐ１ It is possible to calculate and use the following. Also, for example, if the drive roller 36 is commanding torque in the direction that weakens the rotation of the wheel 2, the slip ratio r on the braking side can be calculated using Equation 7. ｓｌｉｐ２ It is possible to calculate and use this.

[0093] In step S133, the control device 70 determines whether the slip ratio between the wheel 2 and the drive roller 36 calculated in step S132 is less than or equal to a certain value. In this case, if the slip ratio is a negative value, it may determine whether the absolute value of the slip ratio is less than or equal to a certain value. If the slip ratio is less than or equal to the certain value, the process proceeds to step S111. On the other hand, if the slip ratio is greater than the certain value, the process proceeds to step S134.

[0094] In step S134, the control device 70 adjusts the reference target torque Tm determined in step S105 so that the slip ratio between the wheel 2 and the drive roller 36 calculated in step S132 is less than or equal to a certain value. ｔａｒ It limits the reference target torque Tm. For example, the reference target torque Tm ｔａｒ By sequentially setting values ​​that decrease by β [%] each time, it is possible to keep the slip ratio between the wheel 2 and the drive roller 36 below a certain value. Alternatively, similar to the process in step S124 of Figure 18, the torque of the electric motor 35 may be controlled so that the slip ratio is below a certain value. Note that β may be the same value as α described above, or it may be a different value. Furthermore, β can be set appropriately based on experiments or simulations.

[0095] In this way, the reference target torque Tm is based on the slip ratio between the wheel 2 and the drive roller 36. ｔａｒ By limiting this, slip between the wheel 2 and the drive roller 36 can be suppressed, improving operability. Furthermore, because it can be controlled in a feedback manner, it can also respond to changes in the coefficient of friction between the wheel 2 and the drive roller 36.

[0096] [Example of limiting the reference target torque using the slip ratio between the wheel and the drive roller] Next, we will explain an example of limiting the reference target torque by calculating the friction coefficient μ between the wheel 2 and the drive roller 36 using the slip ratio between the wheel 2 and the drive roller 36. The method for calculating the slip ratio between the wheel 2 and the drive roller 36 is the same as in the example shown in Figure 19.

[0097] [Example of calculating the friction coefficient between a wheel and a drive roller based on the slip ratio] Here, it is known that the relationship between the slip ratio between wheel 2 and drive roller 36 and the friction coefficient μ between wheel 2 and drive roller 36 shows a specific trend. Therefore, a slip ratio-friction coefficient characteristic, which shows the characteristics of the slip ratio and friction coefficient as a coefficient curve, is set in advance, and it is possible to determine the friction coefficient μ from the slip ratio using this slip ratio-friction coefficient characteristic. Note that the slip ratio-friction coefficient characteristic can be set as appropriate based on experiments or simulations.

[0098] [Example of calculating the friction coefficient between the wheel and drive roller based on the slip ratio] Using the friction coefficient μ obtained based on the slip ratio through the calculation process described above, the limiting torque Tm ｌｉｍ It is possible to calculate the limiting torque Tm using the contact force Fcosθ calculated in step S107 and the friction coefficient μ obtained by the calculation process described above. ｌｉｍ It is possible to calculate the limiting torque Tm using equations 1 and 2. ｌｉｍ It is possible to calculate this.

[0099] Furthermore, from this point onward, the limiting torque Tm ｌｉｍ The coefficient of friction μ used in calculating the slip ratio may be sequentially updated to the coefficient of friction μ determined based on the slip ratio.

[0100] In this way, the limiting torque Tm is used using the friction coefficient between the wheel and the drive roller based on the slip ratio. ｌｉｍ By calculating this, slip between the wheel 2 and the drive roller 36 can be suppressed, improving operability. Furthermore, by combining FF and FB, a controllably robust device can be realized.

[0101] [Example of limiting the standard target torque when moving straight] Next, we will explain an example of setting the final target torque when the manual wheelchair 10 is operated to move straight.

[0102] Figure 20 is a simplified top view showing the external configuration of the manual wheelchair 10. The manual wheelchair 10 is equipped with a right wheel 2a and a left wheel 2b. A right-side electric assist device 1a (not shown) is attached to the right wheel 2a, and a left-side electric assist device 1b (not shown) is attached to the left wheel 2b. The right-side electric assist device 1a and the left-side electric assist device 1b are capable of exchanging various types of information using wired or wireless communication. The right wheel 2a and the left wheel 2b correspond to the wheel 2 described above. The right-side electric assist device 1a and the left-side electric assist device 1b correspond to the electric assist device 1 described above. In the following description, each part of the right-side electric assist device 1a will be denoted by the reference numeral a, and each part of the left-side electric assist device 1b will be denoted by the reference numeral b. Furthermore, Figure 20 schematically shows the magnitudes of the torques calculated by the electric assist device 1a on the right and the electric assist device 1b on the left, respectively, using arrows.

[0103] Figure 20 shows an example where the reference target torque TT1a for the right electric motor 35 is calculated, and the reference target torque TT1b for the left electric motor 35 is calculated. Also, similar to the example shown in Figure 16 above, an example is shown where the limiting torque LT1a for the right reference target torque TT1a is calculated, and the limiting torque LT1b for the left electric motor 35 is calculated for the reference target torque TT1b. In this case, if the limiting torque LT1a for the right is set as the final target torque for the right, and the limiting torque LT1b for the left is set as the final target torque for the left, a difference will occur between the right wheel 2a and the left wheel 2b, which may reduce maneuverability (straight-line stability).

[0104] Therefore, in this example, if the difference in the amount of operation between the right-side electric assist device 1a and the left-side electric assist device 1b is below a threshold, the right-side limiting torque LT1a and the left-side limiting torque LT1b are adjusted to match the lower value (right-side limiting torque LT1a). That is, the right-side limiting torque LT1a is set to the right-side final target torque CT1a, and the left-side final target torque CT1b is set to match the right-side limiting torque LT1a. A specific example of this process will be explained in detail with reference to Figure 21.

[0105] Here, we show an example in which the difference in the operating amounts of the left and right electric assist devices 1a and 1b is used as the difference in the reference target torques TT1a and TT1b of the left and right electric motors 35, but we are not limited to this. For example, the difference in the operating amounts of the left and right electric assist devices 1a and 1b, or the difference in the contact force measured by the load cell 55 can be used as the difference in the operating amounts of the left and right electric assist devices 1a and 1b.

[0106] [Example of operation of the electric assist device] Figure 21 is a flowchart showing an example of the driving control process in the electric assist device 1. This driving control process is executed by the control device 70 (see Figure 14) based on a program stored in the storage unit (not shown) of the control device 70. In Figure 21, only the process of setting the final target torque when the manual wheelchair 10 is operated to move straight, as shown in Figure 20, is illustrated, and the explanation of other processes is omitted. Figures 16, 18, and 19 can be applied to other processes. In Figure 21, the control device 70 refers to either or both of the control devices 70a and 70b. In this driving control process, Figures 1 to 20 will be explained with appropriate reference.

[0107] In step S141, the control device 70 acquires each torque (reference target torque, limiting torque) from the other electric assist device. As a result, the control device 70 acquires the torques for both the left and right sides.

[0108] In step S142, the control device 70 calculates the difference between the right-side reference target torque TT1a and the left-side reference target torque TT1b, and determines whether the difference is less than or equal to a threshold. If the difference is less than or equal to the threshold, it is considered to be an operation to move straight, and the process proceeds to step S143. On the other hand, if the difference is greater than the threshold, it is considered not to be an operation to move straight, and the driving control process terminates. The threshold shown here is a reference value for determining whether the user has performed an operation to move straight. This threshold can be set as appropriate based on experiments or simulations.

[0109] In step S143, the control device 70 adjusts the limiting torque LT1b on the left side to the lower of the two limiting torques LT1a on the right side (the limiting torque LT1a on the right side). In the example shown in Figure 20, the control device 70 sets the limiting torque LT1a on the right side as the final target torque CT1a on the right side, and also sets the final target torque CT1b on the left side to match the limiting torque LT1a on the right side. In this way, if both of the left and right reference target torques are limited, the smaller of the values ​​of the limited reference target torques is set as the final target torques on both sides. It is also conceivable that one of the left or right reference target torques may be limited. In this case, the value of the reference target torque on the limited side is set as the final target torques on both sides.

[0110] For example, the left and right control devices 70 exchange control signals with each other to transmit a reference target torque, limiting torque, etc., to the other. Then, the control device 70 on the side being limited (the left control device 70 in the example shown in Figures 20 and 21) can take the lead in executing the control. This is just one example, and other control methods are also possible. For example, both control devices 70 may independently perform calculation processing, comparison processing, etc., and execute control based on the results exchanged between them.

[0111] In this way, when the manual wheelchair 10 is operated in a straight line, by matching the lower of the two limiting torques of the left and right wheels 2a and 2b to the other, it is possible to prevent the occurrence of a difference between the left and right wheels 2a and 2b, thereby improving operability (straight-line stability).

[0112] [Example of limiting the reference target torque during turning] Next, we will explain an example of setting the final target torque when the manual wheelchair 10 is turned.

[0113] Figure 22 is a simplified top view showing the external configuration of the manual wheelchair 10. Note that each component and arrow shown in Figure 22 corresponds to Figure 20.

[0114] Figure 22 shows an example where the reference target torque TT2a for the right-hand electric motor 35 is calculated, and the reference target torque TT2b for the left-hand electric motor 35 is calculated. Also, similar to the example shown in Figure 16 above, an example is shown where the limiting torque LT2a for the right-hand reference target torque TT2a is calculated, and the limiting torque LT2b for the left-hand electric motor 35 is calculated for the reference target torque TT2b. In this case, if the limiting torque LT2a for the right-hand side is set as the final target torque for the right side, and the limiting torque LT2b for the left-hand side is set as the final target torque for the left side, the vehicle may turn in the opposite direction to what the user intended, potentially reducing operability (stability during turning).

[0115] Therefore, in this example, if the difference in the amount of operation between the right-side electric assist device 1a and the left-side electric assist device 1b is greater than or equal to a threshold, the larger of the right-side reference target torque TT2a and the left-side reference target torque TT2b (the right-side reference target torque TT2a) is used as the reference, and the difference between the left and right sides is adjusted to a constant value. That is, the difference value DV1 between the right-side reference target torque TT2a and the left-side reference target torque TT2b is calculated, and the value obtained by subtracting the difference value DV1 from the right-side limit torque LT2a is used as the reference, and the final target torque CT2b on the left side is set. A specific example of this process will be explained in detail with reference to Figure 23.

[0116] [Example of operation of the electric assist device] Figure 23 is a flowchart showing an example of the driving control process in the electric assist device 1. This driving control process is executed by the control device 70 (see Figure 14) based on a program stored in the storage unit (not shown) of the control device 70. In Figure 23, only the process of setting the final target torque when the manual wheelchair 10 is turned is illustrated as shown in Figure 22, and the explanation of other processes is omitted. Figures 16, 18, and 19 can be applied to other processes. In Figure 23, the control device 70 refers to either or both of the control devices 70a and 70b. In this driving control process, Figures 1 to 22 will be explained with appropriate reference.

[0117] In step S151, the control device 70 acquires each torque (reference target torque, limiting torque) from the other electric assist device. As a result, the control device 70 acquires the torques for both the left and right sides.

[0118] In step S152, the control device 70 calculates the difference between the reference target torque TT1a on the right side and the reference target torque TT1b on the left side, and determines whether the difference is greater than or equal to a threshold. If the difference is greater than or equal to the threshold, it is considered to be an operation to turn, and the process proceeds to step S153. On the other hand, if the difference is less than the threshold, it is considered not to be an operation to turn, and the operation of the driving control process is terminated. The threshold shown here is a reference value for determining whether or not the user has performed an operation to turn, and may be the same value as the threshold shown in Figure 21, or it may be a different value. This threshold can be set as appropriate based on experiments or simulations.

[0119] In step S153, the control device 70 adjusts the difference between the right and left reference target torques to a constant value, using the larger value (right reference target torque TT2a) as the reference target torque TT2a on the right and the left reference target torque TT2b on the left as the reference. In the example shown in Figure 22, the control device 70 calculates the difference value DV1 between the right reference target torque TT2a and the left reference target torque TT2b, and sets the value obtained by subtracting the difference value DV1 from the right limiting torque LT2a as the reference limiting torque LT2a on the right as the final target torque CT2b on the left. However, as shown in Figure 24, it is preferable not to set a driving force opposite to the direction of operation as the driving force on the side with the smaller amount of operation.

[0120] In this manner, if the larger of the left and right reference target torques, or both reference target torques, is restricted, the restricted value of the reference target torque with the larger value is set as the final target torque for the electric assist device on the side with the larger reference target torque. Simultaneously, the value obtained by subtracting the difference from the restricted value of the reference target torque with the larger value is set as the final target torque for the electric assist device on the side with the smaller reference target torque. If only the reference target torque with the smaller value of the left and right reference target torques is restricted, the same restriction process as described above for the case where the larger value, or both reference target torques, are restricted may be applied, or it may be omitted.

[0121] Figure 24 is a simplified top view showing the external configuration of the manual wheelchair 10. Note that each component and arrow shown in Figure 24 corresponds to Figure 22.

[0122] Figure 24 shows an example where the reference target torque TT3a for the right electric motor 35 is calculated, and the reference target torque TT3b for the left electric motor 35 is calculated. Also, similar to the example shown in Figure 16 above, an example is shown where the limiting torque LT3a for the right reference target torque TT3a is calculated, and the limiting torque LT3b for the left electric motor 35 is calculated for the reference target torque TT3b. In this case, if the processing shown in Figures 22 and 23 is applied and the difference between the left and right sides is adjusted to a constant value based on the larger value (the reference target torque TT3a for the right side), the final target torque of the left wheel 2b may be set in the opposite direction to what the user intends, potentially reducing operability (stability during turning).

[0123] Therefore, in this example, when the difference in the amount of operation between the right-side electric assist device 1a and the left-side electric assist device 1b exceeds a threshold, the wheel 2 is prevented from rotating in the opposite direction to the user's operation direction. Specifically, the difference value DV2 between the right-side reference target torque TT3a and the left-side reference target torque TT3b is calculated, and the value obtained by subtracting the difference value DV2 from the right-side limiting torque LT3a is used as the reference. If the direction of the final target torque corresponding to this value is in the opposite direction as shown in Figure 24, the left-side final target torque is set to 0.

[0124] Thus, when a user of the manual wheelchair 10 performs a turning operation, by adjusting the difference between the left and right reference target torques to a constant value, based on the larger of the two reference target torques, it is possible to prevent the wheelchair from turning in the opposite direction to the user's intention. It is also possible to prevent the wheels from rotating in the opposite direction to the user's operation. These measures make it possible to improve operability (stability during turning).

[0125] [Example of providing one control device for two electric assist devices] Figure 25 is a simplified top view showing the external configuration of the manual wheelchair 10. Note that each component shown in Figure 25 corresponds to Figures 20, 22, and 23.

[0126] The above example shows an example in which control devices 70a and 70b are provided for each of the left and right electric assist devices 1a and 1b. Here, each of the left and right electric assist devices 1a and 1b can exchange information via communication units 62a and 62b. Therefore, it is also possible to provide a control device 70 for only one of the left and right electric assist devices 1a and 1b, and for that control device 70 to control both the left and right electric assist devices 1a and 1b.

[0127] For example, as shown in Figure 25, it is possible to provide a control device 70 to the right-side electric assist device 1a, while not providing a control device 70 to the left-side electric assist device 1b. In this case, the control device 70 can exchange various information with the left-side electric assist device 1b via the communication units 62a and 62b, and control the left-side electric assist device 1b. However, the electric assist device 1b without the control device 70 needs to be equipped with an electric motor, various measuring units, etc., in addition to the communication unit 62b.

[0128] Although Figure 25 shows an example where the control device 70 is installed on only one of the left and right electric assist devices 1a and 1b, the control device 70 may also be installed outside the left and right electric assist devices 1a and 1b. For example, the control device 70 can be installed so as to be attachable to any part of the manual wheelchair 10. In this case, the control device 70 is provided with a communication unit, and the control device 70 can exchange various information with the left and right electric assist devices 1a and 1b via its communication unit, communication units 62a and 62b, and control the left and right electric assist devices 1a and 1b.

[0129] Thus, in this embodiment, by electrically rotating the drive roller 36 through user operation and bringing the drive roller 36 into contact with the wheel 2 of the manual wheelchair, it is possible to implement slip prevention control for the electric assist device 1 for the manual wheelchair, which generates driving force for the manual wheelchair. In other words, by measuring the state leading to slip (free spin) of the easily attachable electric assist device 1 for the manual wheelchair and limiting the torque of the electric motor 35, it is possible to prevent slip and improve the operability of the electric assist device 1.

[0130] Furthermore, since the user can obtain the corresponding driving force by moving the left and right electric assist devices 1 forward and backward, it is possible to easily achieve driving that conforms to the user's intentions.

[0131] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the mounting bracket 11 is mainly composed of a tubular portion 16 with a substantially C-shaped cross-section, but the mounting bracket 11 is not limited to such a configuration, and any structure is acceptable as long as it has a hollow passage portion 15 that is curved in an arc shape through which the handrim 5 can pass. For example, the mounting bracket 11 may have a two-part structure so that it can be attached to the handrim 5 in a detachable manner. Also, although an example in which the electric assist device 1 is equipped with a battery unit 13 has been shown, the battery unit 13 may be provided outside the electric assist device 1, and the electric assist device 1 may receive power from the external battery unit 13.

[0132] [Configuration Example and Effects of This Embodiment] The control method according to this embodiment is a control method executed by the control device 70 in an electric assist device 1 comprising: a mounting bracket 11 that is detachably attached to the handrim 5 in a state in which the handrim 5 of the manual wheelchair 10 can slide, having a hollow passage portion 15 through which the handrim 5 of the manual wheelchair 10 can pass; a drive unit 12 having a drive roller 36 that contacts the outer circumferential surface of the wheel 2 of the manual wheelchair 10 and an electric motor 35 that drives the drive roller 36, all housed in a housing supported by the mounting bracket 11; and a control device 70 that controls the electric motor 35. This control method includes a reference target torque calculation process (step S105) that calculates a reference target torque for the electric motor 35 based on the amount of operation of the electric assist device 1 by the user of the manual wheelchair 10, and a control process (steps S107-S110, S121-S124, S131-S134, S141-S143, S151-S153) that detects slip between the wheel 2 and the drive roller 36 and limits the reference target torque based on the detection result. Furthermore, the program according to this embodiment is a program that causes a computer to execute each of these processes. In other words, the program according to this embodiment is a program that causes a computer to realize each of the functions that the control device 70 of the electric assist device 1 can execute.

[0133] With this configuration, if the driving force of the drive roller 36 is not properly transmitted to the wheel 2 of the manual wheelchair 10, and slip occurs between the wheel 2 and the drive roller 36 of the manual wheelchair 10, it is possible to detect the slip between the wheel 2 and the drive roller 36 and prevent the slip from occurring based on the detection result. This makes it possible to improve the operability of the manual wheelchair 10.

[0134] In the control method according to this embodiment, an acquisition process (step S107) for acquiring the contact force between the wheel 2 and the drive roller 36 is further included, and a limiting torque calculation process (step S108) for calculating a limiting torque based on the contact force is also included, and in the control process (steps S109 to S110), the reference target torque is limited based on the limiting torque.

[0135] With this configuration, a limiting torque is calculated based on the contact force between the wheel 2 and the drive roller 36, and by limiting the reference target torque, slip between the wheel 2 and the drive roller 36 can be suppressed, thereby improving operability. Furthermore, because it can be controlled in a front-wheel-drive manner, it can be controlled relatively simply.

[0136] In the control method according to this embodiment, in the control process (steps S109 to S110), if the reference target torque is greater than or equal to the limit torque, the limit torque is set to the reference target torque.

[0137] With this configuration, when the reference target torque is less than the limiting torque, the reference target torque is used as the final target torque, and when the reference target torque is equal to or greater than the limiting torque, the reference target torque is limited, thus enabling appropriate control according to the value of the reference target torque. Furthermore, when the reference target torque is less than the limiting torque, the reference target torque is used as the final target torque, and the limiting process of the reference target torque using the limiting torque is omitted, thereby reducing the computational load on the control device 70.

[0138] The control method according to this embodiment further includes an acquisition process (step S131) ​​for acquiring the rotational speed of the electric motor 35 and the rotational speed of the wheel 2, a slip ratio calculation process (step S132) for calculating the slip ratio between the wheel 2 and the drive roller 36 based on the rotational speed of the electric motor 35 and the rotational speed of the wheel 2, and a friction coefficient calculation process (processing by the control device 70) for calculating the friction coefficient between the wheel 2 and the drive roller 36 based on the slip ratio. In the limiting torque calculation process (step S108), the limiting torque is calculated based on the contact force and its friction coefficient.

[0139] This configuration makes it possible to suppress slip between the wheel 2 and the drive roller 36 by using an appropriate coefficient of friction that takes into account the slip ratio between the wheel 2 and the drive roller 36. This improves operability. Furthermore, by combining FF and FB, it is possible to realize a controllably robust device.

[0140] The control method according to this embodiment further includes a first acceleration calculation process (step S121) that calculates the rotational acceleration of the drive roller 36 based on the rotational speed of the electric motor 35, and a second acceleration calculation process (step S122) that calculates the wheel acceleration at which the wheels 2 of the manual wheelchair 10 can be accelerated based on a reference target torque. In the control process (steps S123 to S124), the reference target torque is limited based on the rotational acceleration and the wheel acceleration.

[0141] With this configuration, by limiting the reference target torque based on the rotational acceleration of the drive roller 36 and the accelerating wheel acceleration of the wheel 2, slip between the wheel 2 and the drive roller 36 can be suppressed, thereby improving operability. Furthermore, because it can be controlled in a fast-forward manner, it can also accommodate changes in the coefficient of friction between the wheel 2 and the drive roller 36.

[0142] In the control method according to this embodiment, during the control process (steps S123 to S124), if the predicted wheel acceleration of the wheel 2 is greater than or equal to the rotational acceleration of the drive roller 36, the reference target torque is limited to a constant value.

[0143] With this configuration, when the predicted wheel acceleration of wheel 2 is less than the rotational acceleration of the drive roller 36, the reference target torque is set as the final target torque, and when the predicted wheel acceleration of wheel 2 is equal to or greater than the rotational acceleration of the drive roller 36, the reference target torque is limited to a constant value, thus enabling appropriate control according to the rotational acceleration of the drive roller 36 and the wheel acceleration of wheel 2. Furthermore, when the predicted wheel acceleration of wheel 2 is less than the rotational acceleration of the drive roller 36, the reference target torque is used as the final target torque, and the limiting process of the reference target torque using the limiting torque is omitted, thereby reducing the computational load on the control device 70.

[0144] The control method according to this embodiment further includes an acquisition process (step S131) ​​for acquiring the rotational speed of the electric motor 35 and the rotational speed of the wheel 2, and a slip ratio calculation process (step S132) for calculating the slip ratio between the wheel 2 and the drive roller 36 based on the rotational speed of the electric motor 35 and the rotational speed of the wheel 2. In the control process (steps S133 to S134), the reference target torque is limited based on the slip ratio.

[0145] With this configuration, by limiting the reference target torque based on the slip ratio between the wheel 2 and the drive roller 36, slip between the wheel 2 and the drive roller 36 can be suppressed, thereby improving operability. Furthermore, because it can be controlled in a fast-forward manner, it can also accommodate changes in the friction coefficient between the wheel 2 and the drive roller 36.

[0146] In the control method according to this embodiment, the control process (steps S133 to S134) limits the reference target torque so that the slip ratio between the wheel 2 and the drive roller 36 does not exceed a certain value.

[0147] With this configuration, appropriate control is possible according to the slip ratio between the wheel 2 and the drive roller 36 in order to limit the reference target torque so that the slip ratio between the wheel 2 and the drive roller 36 does not exceed a certain value. Furthermore, when there is no slip ratio between the wheel 2 and the drive roller 36, or when the slip ratio is below a certain value, the reference target torque is used as the final target torque, and the limiting process of the reference target torque using the limiting torque is omitted, thereby reducing the computational load on the control device 70.

[0148] In the control method according to this embodiment, two electric assist devices 1a and 1b are attached to the left and right wheels 2a and 2b of the manual wheelchair 10, respectively. In the control process (steps S141 to S143), the reference target torques of the two electric assist devices 1a and 1b before limitation are obtained. If the difference between the two reference target torques is less than or equal to a predetermined value, and either of the two reference target torques is limited, the value of the limited reference target torque is set as the final target torque for the two electric assist devices 1a and 1b. If both of the two reference target torques are limited, the smaller of the two limited reference target torque values ​​is set as the final target torque for the two electric assist devices 1a and 1b.

[0149] With this configuration, when the user of the manual wheelchair 10 operates in a straight line, the left and right wheels 2a and 2b can be made to differ in their torque by matching the lower of the two limiting torques of the left and right wheels, thereby improving maneuverability (straight-line stability).

[0150] In the control method according to this embodiment, two electric assist devices 1a and 1b are attached to the left and right wheels 2a and 2b of the manual wheelchair 10, respectively. In the control process (steps S151 to S153), the reference target torques of the two electric assist devices 1a and 1b before restriction are obtained. If the difference between the two reference target torques is greater than a predetermined value, and the larger of the two reference target torques, or both of the reference target torques, is restricted, the restricted value of the reference target torque with the larger value is set as the final target torque of the electric assist device with the larger reference target torque, and the value obtained by subtracting the difference from the restricted value of the reference target torque with the larger value is set as the final target torque of the electric assist device with the smaller reference target torque.

[0151] With this configuration, when a user of the manual wheelchair 10 performs a turning operation, the difference between the left and right reference target torques is adjusted to a constant value based on the larger value, thereby preventing the wheelchair from turning in the opposite direction to the user's intention. This improves operability (stability during turning).

[0152] In the control method according to this embodiment, two electric assist devices 1a and 1b are attached to the left and right wheels 2a and 2b of the manual wheelchair 10, respectively. The control device 70 is provided on either of the two electric assist devices 1a and 1b, or outside of the two electric assist devices 1a and 1b. For example, as shown in Figure 25, the control device 70 can be provided on the electric assist device 1a.

[0153] This configuration eliminates the need to provide a control device 70 in both the two electric assist devices 1a and 1b, thereby reducing the manufacturing costs of the two electric assist devices 1a and 1b. Furthermore, if both electric assist devices 1a and 1b are equipped with a control device 70, each control device 70 must perform the calculation processing. However, by providing only one control device 70, it is possible to eliminate redundant and unnecessary calculation processing in both devices, thereby reducing the amount of computation.

[0154] The electric assist device 1 is an electric assist device that is attached to a manual wheelchair 10. The electric assist device 1 has a hollow passage 15 through which the handrim 5 of the manual wheelchair 10 can pass, and includes a mounting bracket 11 that is detachably attached to the handrim 5 so that the handrim 5 can slide within the hollow passage 15, a drive unit 12 which has a drive roller 36 that contacts the outer circumferential surface of the wheel 2 of the manual wheelchair 10 and an electric motor 35 that drives the drive roller 36, and a control device 70 that controls the electric motor 35. The control device 70 calculates a reference target torque of the electric motor 35 based on the amount of operation of the electric assist device 1 by the user of the manual wheelchair 10, detects slip between the wheel 2 and the drive roller 36, and limits the reference target torque based on the detection result. Furthermore, the program according to this embodiment is a program that causes a computer to execute each of these processes. In other words, the program according to this embodiment is a program that causes a computer to realize each of the functions that the control device 70 of the electric assist device 1 can execute. Furthermore, if the program is recorded on a computer-readable recording medium, that recording medium constitutes this embodiment.

[0155] With this configuration, if the driving force of the drive roller 36 is not properly transmitted to the wheel 2 of the manual wheelchair 10, and slip occurs between the wheel 2 and the drive roller 36 of the manual wheelchair 10, it is possible to detect the slip between the wheel 2 and the drive roller 36 and prevent the slip from occurring based on the detection result. This makes it possible to improve the operability of the manual wheelchair 10.

[0156] Furthermore, each process in this embodiment is executed based on a program that causes a computer to perform various processing procedures. This embodiment can also be understood as an embodiment of a program that realizes the function of executing each of these processes, and a recording medium that stores that program. For example, by performing an update process to add a new function to the control device of an electric assist device, the program can be stored in the storage device of the electric assist device. This makes it possible to have the updated control device of the electric assist device perform each of the processes shown in this embodiment.

[0157] Although embodiments of the present invention have been described above, these embodiments merely illustrate examples of how the present invention can be applied, and are not intended to limit the technical scope of the present invention to the specific configurations of the embodiments described above.

Claims

1. An electric assist device comprising: a mounting bracket detachably attached to a handrim having a hollow passage through which a wheelchair handrim can pass, such that the handrim can slide within the hollow passage; a drive unit having a drive roller in contact with the outer surface of the wheelchair wheel and an electric motor for driving the drive roller, within a housing supported by the mounting bracket; and a control device for controlling the electric motor, wherein a control method performed by the control device includes: a reference target torque calculation process for calculating a reference target torque of the electric motor based on the amount of operation of the electric assist device by the wheelchair user; and a control process for detecting slip between the wheel and the drive roller and limiting the reference target torque based on the detection result.

2. A control method for an electric assist device according to claim 1, further comprising: an acquisition process for acquiring the contact force between the wheel and the drive roller; and a limiting torque calculation process for calculating a limiting torque based on the contact force, wherein the control process limits the reference target torque based on the limiting torque.

3. A control method for an electric assist device according to claim 2, wherein in the control process, if the reference target torque is equal to or greater than the limiting torque, the limiting torque is set to the reference target torque.

4. A control method for an electric assist device according to claim 2, further comprising: an acquisition process for acquiring the rotational speed of the electric motor and the rotational speed of the wheel; a slip ratio calculation process for calculating a slip ratio between the wheel and the drive roller based on the rotational speed of the electric motor and the rotational speed of the wheel; and a friction coefficient calculation process for calculating a friction coefficient between the wheel and the drive roller based on the slip ratio, wherein the limiting torque calculation process calculates the limiting torque based on the contact force and the friction coefficient.

5. A control method for an electric assist device according to claim 1, further comprising: a first acceleration calculation process for calculating the rotational acceleration of the drive roller based on the rotational speed of the electric motor; and a second acceleration calculation process for calculating the wheel acceleration that the wheel can accelerate based on the reference target torque, wherein the control process limits the reference target torque based on the rotational acceleration and the wheel acceleration.

6. A control method for an electric assist device according to claim 5, wherein, in the control process, the reference target torque is limited to a constant value when the wheel acceleration is greater than or equal to the rotational acceleration.

7. A control method for an electric assist device according to claim 1, further comprising: an acquisition process for acquiring the rotational speed of the electric motor and the rotational speed of the wheel; and a slip ratio calculation process for calculating the slip ratio between the wheel and the drive roller based on the rotational speed of the electric motor and the rotational speed of the wheel, wherein the control process limits the reference target torque based on the slip ratio.

8. A control method for an electric assist device according to claim 7, wherein the control process limits the reference target torque so that the slip ratio does not exceed a certain value.

9. A control method for an electric assist device according to any one of claims 1 to 8, wherein two of the electric assist devices are attached to the left and right wheels of the wheelchair, and in the control process, the reference target torques of the two electric assist devices before restriction are obtained, and if the difference between the two reference target torques is less than or equal to a predetermined value, if either of the two reference target torques is restricted, the value of the restricted reference target torque is set as the final target torque for the two electric assist devices, and if both of the two reference target torques are restricted, the smaller of the values ​​of the restricted reference target torques is set as the final target torque for the two electric assist devices.

10. A control method for an electric assist device according to any one of claims 1 to 8, wherein two of the electric assist devices are attached to the left and right wheels of the wheelchair, and in the control process, the reference target torques of the two electric assist devices before restriction are obtained, and when the difference between the two reference target torques is greater than a predetermined value, the one with the larger value, or both of the reference target torques, is restricted, the restricted value of the one with the larger reference target torque is set as the final target torque of the electric assist device with the larger reference target torque, and the value obtained by subtracting the difference from the restricted value of the one with the larger reference target torque is set as the final target torque of the electric assist device with the smaller reference target torque.

11. A method for controlling an electric assist device according to any one of claims 1 to 8, wherein two of the electric assist devices are attached to the left and right wheels of the wheelchair, and the control device is provided in either of the two electric assist devices or outside of the two electric assist devices.

12. An electric assist device attached to a wheelchair, comprising: a mounting bracket detachably attached to the handrim having a hollow passage through which the handrim of the wheelchair can pass, and the handrim sliding within the hollow passage; a drive unit having a drive roller in contact with the outer surface of the wheelchair wheel and an electric motor for driving the drive roller, and a control device for controlling the electric motor, wherein the control device calculates a reference target torque of the electric motor based on the amount of operation of the electric assist device by the wheelchair user, detects slip between the wheel and the drive roller, and limits the reference target torque based on the detection result.

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