Electric wheelchair, drive system for mounting on electric wheelchair, control method for electric wheelchair, and program

Abstract

To reduce a burden on a caregiver when turning an electric wheelchair.SOLUTION: When a force (torque) for turning the wheel chair 100 to the left is detected, the control device 20 increases the rotation speed of the right wheel motor 25R from the rotation speed corresponding to the common reference speed Vs, and decreases the rotation speed of the left wheel motor 25L from the rotation speed corresponding to the common reference speed Vs. The control device 20 increases the rotation speed of the left wheel motor 25L from the rotation speed corresponding to the common reference speed Vs and decreases the rotation speed of the right wheel motor 25R from the rotation speed corresponding to the common reference speed Vs when the force turning the wheel chair 100 in the right direction is detected.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an electric wheelchair, a drive system for mounting on an electric wheelchair, a control method for an electric wheelchair, and a program. [Background technology]

[0002] The following Patent Document 1 discloses an electric wheelchair with an electric motor on each of the right and left wheels. The electric wheelchair has a grip on the rear side for an assistant to push it. In Patent Document 1, when the assistant operates the switch on the assistant operation unit, the left and right electric motors are driven so that the electric wheelchair travels at a constant speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-130921 Summary of the Invention [Problem to be solved by the invention]

[0004] To turn the electric wheelchair to the right, the caregiver must push harder on the left grip than on the right grip, and to turn the electric wheelchair to the left, the caregiver must push harder on the right grip than on the left grip. Such a turn can be a significant burden on the caregiver. For example, turning can be particularly burdensome for the caregiver if the electric wheelchair occupant is heavy. [Means for solving the problem]

[0005] (1) This disclosure proposes a drive system for mounting on an electric wheelchair having right and left wheels. The drive system includes a right wheel motor for driving the right wheel, a left wheel motor for driving the left wheel, a means for detecting an external force acting to turn the electric wheelchair, and a control device for controlling the right wheel motor and the left wheel motor based on a common reference speed. When the force acting to turn the electric wheelchair left is detected, the control device increases the rotational speed of the right wheel motor from the rotational speed corresponding to the common reference speed and decreases the rotational speed of the left wheel motor from the rotational speed corresponding to the common reference speed. When the force acting to turn the electric wheelchair right is detected, the control device increases the rotational speed of the left wheel motor from the rotational speed corresponding to the common reference speed and decreases the rotational speed of the right wheel motor from the rotational speed corresponding to the common reference speed. This drive system reduces the burden on a caregiver when turning an electric wheelchair while suppressing changes in the speed of the electric wheelchair.

[0006] (2) In the drive system of (1), when the force that turns the electric wheelchair is detected, the control device performs a first correction, which is either adding or subtracting a correction value, and controls one of the right wheel motor and the left wheel motor based on the result of the first correction, and performs a second correction, which is the other of adding or subtracting the correction value, and controls the other of the right wheel motor and the left wheel motor based on the result of the second correction.

[0007] (3) In the drive system of (1), the control device controls the right wheel motor based on an addition result obtained by adding a correction value to the common reference speed during the left turn, and controls the left wheel motor based on a subtraction result obtained by subtracting the correction value from the common reference speed during the right turn.

[0008] (4) The drive system described in (2) includes a right speed sensor that outputs a signal corresponding to the speed of the right wheel and a left speed sensor that outputs a signal corresponding to the speed of the left wheel. When a difference between the speed obtained from the right speed sensor and the speed obtained from the left speed sensor satisfies a predetermined condition, the control device relaxes at least one of the first correction and the second correction so as to reduce the difference between the rotation speed of the left wheel motor and the rotation speed of the right wheel motor. This makes it possible to prevent the turning speed from becoming excessively high.

[0009] (5) In the drive system described in any one of (1) to (4), the control device calculates the correction value based on at least one of the force for turning the electric wheelchair and the speed of the electric wheelchair, and a preset upper limit value for the correction value. This allows the correction value to be increased according to the force for turning the electric wheelchair while keeping it smaller than the upper limit value. Also, the correction value can be set to a value according to the speed of the electric wheelchair while keeping it smaller than the upper limit value.

[0010] (6) In the drive system described in any one of (1) to (5), the control device calculates the common reference speed according to the amount of operation applied to an operating member provided in the electric wheelchair. This allows the electric wheelchair to travel at a speed according to the amount of operation.

[0011] (7) In the drive system described in any one of (1) to (6), the control device calculates the correction value based on the external force acting on the electric wheelchair. This allows assistance to be obtained according to the force acting on the electric wheelchair, i.e., the force applied to the electric wheelchair by an assistant.

[0012] (8) In the drive system described in any one of (1) to (7), the control device calculates the force for turning the electric wheelchair based on the angular velocity of the electric wheelchair about a vertical axis.

[0013] (9) The drive system described in any one of (1) to (8) includes a right speed sensor that outputs a signal corresponding to the speed of the right wheel and a left speed sensor that outputs a signal corresponding to the speed of the left wheel. The control device controls the right wheel motor and the left wheel motor based on the difference between the average of the right wheel speed and the left wheel speed and the common reference speed. When the control device detects the force that turns the electric wheelchair, the control device adds a correction value to one of the average and the common reference speed to control one of the right wheel motor and the left wheel motor, and subtracts a correction value from one of the average and the common reference speed to control the other of the right wheel motor and the left wheel motor.

[0014] (10) In the drive system described in any one of (2) to (9), the control device calculates the correction value based on the speed of the electric wheelchair. This makes it possible to suppress turning at high speeds.

[0015] (11) In the drive system described in (10), the correction value calculated when the speed of the electric wheelchair is a first speed that is smaller than a threshold value is greater than the correction value calculated when the speed of the electric wheelchair is a second speed that is larger than a threshold value. This makes it possible to prevent sharp turns at high speeds.

[0016] (12) In the drive system described in any one of (1) to (11), the control device detects an operation performed by an assistant on an operating member provided on the electric wheelchair and limits the common reference speed to a predetermined value or less based on the operation. This allows the wheel motors to assist turning while keeping the speed of the electric wheelchair low. As a result, turning can be easily performed in narrow spaces.

[0017] (13) In the drive system described in any one of (2) to (13), the control device receives a command from the user to change the upper limit of the correction value, thereby preventing turning assistance of a magnitude unintended by the user.

[0018] (14) In the drive system of (2), when the common reference speed is lower than the correction value, the control device makes the rotation speed of one of the right wheel motor and the left wheel motor a positive value by the first correction, and makes the rotation speed of the other of the right wheel motor and the left wheel motor a negative value by the second correction. This makes it possible to reduce the space required for turning and to lighten the load required for turning.

[0019] (15) The electric wheelchair proposed in this disclosure has the drive system described in any one of (1) to (14), the right wheel, and the left wheel.

[0020] (16) This disclosure proposes a control method for an electric wheelchair having a right wheel, a left wheel, a right wheel motor for driving the right wheel, and a left wheel motor for driving the left wheel. This control method includes the steps of detecting an external force acting to turn the electric wheelchair and controlling the right wheel motor and the left wheel motor based on a common reference speed. The control steps include the steps of increasing the rotational speed of the right wheel motor from a rotational speed corresponding to the common reference speed and decreasing the rotational speed of the left wheel motor from a rotational speed corresponding to the reference speed, which are executed when the force to turn the electric wheelchair left is detected. The control steps also include the steps of increasing the rotational speed of the left wheel motor from a rotational speed corresponding to the reference speed and decreasing the rotational speed of the right wheel motor from a rotational speed corresponding to the reference speed, which are executed when the force to turn the electric wheelchair right is detected. This control method can reduce the burden on a caregiver when turning the electric wheelchair while suppressing changes in the speed of the electric wheelchair.

[0021] (17) The present disclosure also proposes a program for causing a computer to function as a control device for an electric wheelchair having a right wheel, a left wheel, a right wheel motor for driving the right wheel, and a left wheel motor for driving the left wheel. This program causes the computer to function as means for detecting an external force acting to turn the electric wheelchair and control means for controlling the right wheel motor and the left wheel motor based on a common reference speed. The control means includes means for increasing the rotational speed of the right wheel motor from a rotational speed corresponding to the common reference speed and decreasing the rotational speed of the left wheel motor from a rotational speed corresponding to the common reference speed when the force for turning the electric wheelchair to the right is detected. The control means also includes means for increasing the rotational speed of the left wheel motor from a rotational speed corresponding to the common reference speed and decreasing the rotational speed of the right wheel motor from a rotational speed corresponding to the common reference speed when the force for turning the electric wheelchair to the right is detected. This program reduces the burden on the caregiver when turning an electric wheelchair while suppressing changes in the wheelchair's speed. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view of an electric wheelchair. [Figure 2] FIG. 2 is a block diagram of a drive system of the electric wheelchair. [Figure 3] FIG. 3 is a block diagram showing functions executed by the control device shown in FIG. 2. [Figure 4A] FIG. 2 is a diagram for explaining an outline of control executed by a control device. [Figure 4B] FIG. 10 is a diagram for explaining turning in a reverse mode. [Figure 5A] FIG. 10 is a diagram illustrating an example of the relationship between the speed influence rate used in calculating the corrected speed and the wheelchair speed. [Figure 5B] FIG. 10 is a diagram illustrating an example of the relationship between a torque influence rate used in calculating a correction speed and a ratio of a detected input turning torque to a maximum value of the turning torque. [Figure 6A] FIG. 4 is a flowchart showing the flow of processing executed by the control device. [Figure 6B] FIG. 4 is a flowchart showing the flow of processing executed by the control device. [Figure 7] 10 is a time chart showing an example of changes in (a) input turning torque, (b) reference speed, and (c) output torque of a wheel motor. [Figure 8] 10 is a time chart showing another example of changes in (a) input turning torque, (b) reference speed, and (c) output torque of a wheel motor. DETAILED DESCRIPTION OF THE INVENTION

[0023] The electric wheelchair, drive system, control method for an electric wheelchair, and program proposed in this disclosure will be described below.

[0024] In the following description, the Y1 and Y2 directions shown in Fig. 1 are referred to as the front and rear, respectively. The Z1 and Z2 directions shown in Fig. 1 are referred to as the top and bottom, respectively, and the X1 and X2 directions shown in Fig. 1 are referred to as the right and left, respectively.

[0025] As shown in Fig. 1, the electric wheelchair 100 has a right wheel 2R and a left wheel 2L. The wheelchair 100 also has a right wheel motor 25R (see Fig. 2) for driving the right wheel 2R, and a left wheel motor 25L (see Figs. 1 and 2) for driving the left wheel 2L. The rotation of the wheel motors 25R and 25L may be transmitted to the wheels 2R and 2L via a speed reduction mechanism, or may be transmitted directly to the wheels 2R and 2L without going through a speed reduction mechanism.

[0026] The right wheel motor 25R may be provided on the hub of the right wheel 2R, and the left wheel motor 25L may be provided on the hub of the left wheel 2L. In other words, the wheel motors 25R, 25L may be so-called in-wheel motors. The positions at which the wheel motors 25R, 25L are arranged are not limited to the example shown in FIG. 1. For example, the wheel motors 25R, 25L may be provided at different positions on the hubs of the wheels 2R, 2L, and their torque may be transmitted via a transmission mechanism such as a chain.

[0027] As shown in Figure 1, the wheelchair 100 has a seat 6 disposed between the right wheel 2R and the left wheel 2L, and a backrest 9 disposed behind the seat 6 to support the back of an occupant sitting in the seat 6. It also has armrests 8 disposed on the right and left sides of the seat 6 for the occupant to rest their arms on. The wheels 2R and 2L, the seat 6, the backrest 9, the armrests 8, etc. are supported by a body frame 4.

[0028] 1, the wheelchair 100 has left and right handle grips 7 extending rearward from the backrest 9 for the caregiver to grasp with their hands. While holding the left and right handle grips 7, the caregiver moves the wheelchair 100 by pushing it forward or pulling it backward.

[0029] As shown in FIG. 1, the wheelchair 100 has a front operation input unit 51. The front operation input unit 51 is provided, for example, in front of the right armrest 8 and is operated by the occupant sitting in the seat 6. The front operation input unit 51 may have a travel operation stick 51a. The travel operation stick 51a can be tilted from its neutral position forward, to the right, to the left, or diagonally relative to any of these. The front operation input unit 51 has a sensor (not shown) that detects the tilt angle and tilt direction of the travel operation stick 51a, and inputs signals corresponding to the tilt angle and tilt direction to the control device 20 (see FIG. 2).

[0030] When the travel operation stick 51a is tilted, the control device 20 drives the wheel motors 25R and 25L at a speed corresponding to the tilt direction and angle. This allows the wheelchair 100 to move in the direction and at the speed desired by the occupant. When the travel operation stick 51a is returned to the neutral position, the control device 20 stops driving the wheel motors 25L and 25R.

[0031] As shown in Fig. 1, the wheelchair 100 has a rear operation input unit 52. The rear operation input unit 52 is provided, for example, on the right handle grip 7 and is operated by an assistant. As shown in Fig. 2, the rear operation input unit 52 has, for example, an assistant travel lever (operating member) 52a and a reverse selection switch (reverse selection input section) 52b. The rear operation input unit 52 inputs a signal to the control device 20 according to the amount of operation of the assistant travel lever 52a by the assistant.

[0032] The rear operation input unit 52 inputs a signal corresponding to the operation (ON / OFF operation) of the reverse selection switch 52b to the control device 20. When the reverse selection switch 52b is in the ON state, the reverse mode is selected, and the control device 20 drives the wheel motors 25R, 25L so that the wheelchair 100 moves backward at a speed corresponding to the operation of the assistance travel lever 52a. On the other hand, when the reverse selection switch 52b is in the OFF state, the forward mode is selected, and the control device 20 drives the wheel motors 25R, 25L so that the wheelchair 100 moves forward at a speed corresponding to the operation of the assistance travel lever 52a. Unlike the example shown in FIG. 2, the wheelchair 100 may have a forward selection switch for selecting the forward mode.

[0033] The rear operation input unit 52 may have an operating member other than the assist travel lever 52a. The control device 20 may then drive the wheel motors 25R, 25L so that the wheelchair 100 moves forward or backward at a speed corresponding to the operation of the operating member. For example, the rear operation input unit 52 may have a dial for setting the speed, a forward selection switch, and a reverse selection switch. When the forward selection switch is turned on, the control device 20 may drive the wheel motors 25R, 25L at a speed corresponding to the amount of operation of the dial so that the wheelchair 100 moves forward. When the reverse selection switch is turned on, the control device 20 may drive the wheel motors 25R, 25L at a speed corresponding to the amount of operation of the dial so that the wheelchair 100 moves backward.

[0034] 2, the rear operation input unit 52 may have a stop / turn switch 52c. When the stop / turn switch 52c is operated, the wheelchair 100 remains stopped (the center position of the wheelchair 100 does not change) and drives the wheel motors 25R and 25L to assist the turn operation by the caregiver. The control when the stop / turn switch 52c is operated will be described later.

[0035] 2, the wheelchair 100 has a right speed sensor 31R that inputs a signal corresponding to the speed of the right wheel 2R to the control device 20, and a left speed sensor 31L that inputs a signal corresponding to the speed of the left wheel 2L to the control device 20. The speed sensors 31R and 31L are sensors that output signals corresponding to the rotational speeds, and may include, for example, encoders.

[0036] The positions at which the speed sensors 31R and 31L are attached are not particularly limited as long as they are positions at which signals corresponding to the speeds of the wheels 2R and 2L are output. For example, the speed sensors 31R and 31L may be attached to the wheels 2R and 2L or to the wheel motors 25R and 25L.

[0037] The control device 20 calculates the speed of the wheels 2R and 2L (forward and backward speed) and the speed of the wheelchair 100 based on the outputs (rotational speeds) of the speed sensors 31R and 31L and the radii of the wheels 2R and 2L. The speed of the wheelchair 100 may be, for example, the average of the speeds of the left and right wheels 2R and 2L. Hereinafter, the speed of the wheelchair 100 will be referred to as the "wheelchair speed." Furthermore, the speed obtained by multiplying the rotational speed of the right wheel 2R by the radius of the right wheel 2R will be referred to as the "right wheel speed," and the speed obtained by multiplying the rotational speed of the left wheel 2L by the radius of the left wheel 2L will be referred to as the "left wheel speed."

[0038] As shown in Fig. 2, the wheelchair 100 may have a turning torque sensor 32. The turning torque sensor 32 outputs a signal corresponding to the torque (turning torque) of the wheelchair 100 around an axis along the vertical direction (Z1-Z2 direction) of the wheelchair 100. The turning torque sensor 32 may be an angular velocity sensor. The control device 20 may calculate the turning torque based on the output of this angular velocity sensor.

[0039] The wheelchair 100 does not necessarily have to have the turning torque sensor 32. In this case, the control device 20 may calculate the turning torque based on the outputs of the speed sensors 31R and 31L, for example. This calculation by the control device 20 will be explained later.

[0040] 2, the control device 20 has a calculation unit 21 and a storage unit 22. The calculation unit 21 may have a central processing unit (CPU), a microprocessor, a field programmable gate array (FPGA), etc. The storage unit 22 includes a read only memory (ROM), a random access memory (RAM), etc., and stores programs executed by the calculation unit 21, tables used in the execution of the programs, etc.

[0041] The control device 20 executes a program stored in the storage device 22 in the calculation device 21, thereby controlling the wheel motors 25R and 25L in response to the operation of the operation input units 51 and 52. In the example disclosed in this specification, when the caregiver attempts to turn the wheelchair 100, the control device 20 drives the wheel motors 25R and 25L to assist the caregiver in turning the wheelchair 100. The control performed by the control device 20 will be described in detail later.

[0042] As shown in Figure 2, the wheelchair 100 has a right drive unit 26R and a left drive unit 26L. Current from the battery 11 is supplied to the drive units 26R and 26L. The control device 20 calculates a command value based on signals input from the operation input units 51 and 52. The right drive unit 26R uses the current from the battery 11 to supply a current according to the command value to the right wheel motor 25R. The left drive unit 26L uses the current from the battery 11 to supply a current according to the command value to the left wheel motor 25L.

[0043] The wheel motors 25R, 25L may be DC motors, for example. The drive units 26R, 26L include DC / DC converters and supply current corresponding to command values ​​to the wheel motors 25R, 25L. The wheel motors 25R, 25L may be AC ​​motors. In this case, the drive units 26R, 26L may include inverters that use current from the battery 11 to supply current at a frequency corresponding to the command values ​​to the wheel motors 25R, 25L.

[0044] The drive system of the electric wheelchair 100 may be composed of the control device 20 shown in Fig. 2, wheel motors 25R / 25L, drive units 26R / 26L, rear operation input unit 52, speed sensors 31R / 31L, etc. The drive system does not need to include the wheels 2R / 2L and seat 6 shown in Fig. 1 as components.

[0045] [Control device] 3 is a block diagram showing the functions of the control device 20. The control device 20 has, as its functions, a turning torque calculation unit 21a, an auxiliary condition determination unit 21b, a reference speed calculation unit 21c, a command value calculation unit 21m, and a parameter adjustment unit 21p. These functions are realized by the calculation unit 21 executing a program stored in the storage unit 22.

[0046] [Turning torque calculation section] When the caregiver turns the wheelchair 100 to the left (X2 direction, see Figure 1) while moving the wheelchair 100 forward, the caregiver pushes the right handle grip 7 forward more strongly than the left handle grip 7. This generates a leftward turning torque in the wheelchair 100. Conversely, when the caregiver turns the wheelchair 100 to the right (X1 direction, see Figure 1) while moving the wheelchair 100 forward, the caregiver pushes the left handle grip 7 forward more strongly than the right handle grip 7. This generates a rightward turning torque in the wheelchair 100. The turning torque calculation unit 21a detects the force (torque) acting from the outside (specifically, the caregiver) to turn the wheelchair 100. Hereinafter, this torque will be referred to as the "input turning torque."

[0047] As described above, one example of the wheelchair 100 may have a turning torque sensor 32. The turning torque sensor 32 is, for example, an angular velocity sensor. The turning torque calculation unit 21a may calculate the torque that the caregiver applies to the wheelchair 100 based on this angular velocity. The turning torque calculation unit 21a may calculate the input turning torque based on the time derivative of the angular velocity detected by the angular velocity sensor 32.

[0048] The sensor used to calculate the input turning torque is not limited to the turning torque sensor 32 (angular velocity sensor). For example, a sensor (magnetostrictive sensor) that outputs a signal corresponding to the twist of the handle grip 7 may be attached to the left and right handle grips 7. Then, the control device 20 may calculate the turning torque that the caregiver applies to the wheelchair 100 based on the output of the sensor (force applied in the right or left direction).

[0049] As yet another example, acceleration sensors may be attached to the right and left parts of the wheelchair 100. The control device 20 may then calculate the turning torque that the caregiver applies to the wheelchair 100 based on the difference between the acceleration of the right part and the acceleration of the left part obtained from these two acceleration sensors (in other words, the difference between the force acting on the right part and the force acting on the left part). The output of the acceleration sensor may be affected by the inclination of the location where the wheelchair 100 is traveling. Therefore, the calculation of the turning torque using the acceleration sensor may be performed only on flat ground.

[0050] In yet another example, the turning torque calculation unit 21a may calculate the input turning torque based on the right wheel speed obtained from the output of the right speed sensor 31R and the left wheel speed obtained from the output of the left speed sensor 31L. For example, the turning torque calculation unit 21a may calculate the input turning torque using the following equation (1).

number

[0051] As will be explained later, when the above-mentioned input turning torque is applied to the wheelchair 100 by the caregiver, the control device 20 controls the wheel motors 25R and 25L to assist such turning operation. Therefore, after the assistance of the turning operation starts, the torque caused by driving the wheel motors 25R and 25L also acts on the wheelchair 100. The turning torque calculation unit 21a may subtract the torque caused by driving the wheel motors 25R and 25L from the turning torque calculated by the above-mentioned processing. Then, the turning torque calculation unit 21a may use the result of this subtraction as the input turning torque applied by the caregiver.

[0052] For example, the turning torque calculation unit 21a may calculate the input turning torque by the following equation (2): In equation (2), the second term on the right side is the torque generated in the wheelchair 100 by driving the wheel motors 25R and 25L.

number

[0053] [Auxiliary condition determination section] As shown in FIG. 3, the assist condition determination unit 21b includes a start determination unit 21i. The start determination unit 21i determines whether a condition (assist start condition) for starting turning assistance by the wheel motors 25R and 25L is met. The assist start condition includes the condition regarding the input turning torque described above. For example, if the input turning torque is equal to or greater than a predetermined threshold, it is determined that the assist start condition is met, and turning assistance by the wheel motors 25R and 25L is started. This prevents erroneous detection of the caregiver's intention to turn and prevents the wheel motors 25R and 25L from starting assistance when the caregiver is operating without intending to turn. Note that turning assistance by the wheel motors 25R and 25L may be started if the input turning torque equal to or greater than a predetermined threshold continues for a predetermined period of time.

[0054] The assist start condition may include a condition regarding the speed of the wheelchair 100. For example, it may be determined that the assist start condition is satisfied when the input turning torque is equal to or greater than a predetermined threshold and the wheelchair speed is lower than the threshold. This makes it possible to prevent turning assistance from being provided when the speed of the wheelchair 100 is high.

[0055] When the difference between the right wheel speed VR and the left wheel speed VL satisfies a predetermined condition during turning, the auxiliary condition determination unit 21b relaxes at least one of the additive correction and the subtractive correction so as to reduce the difference between the rotation speed of the left wheel motor 25L and the rotation speed of the right wheel motor 25R. Here, relaxing the correction includes stopping the correction itself, reducing the correction speed Vc, etc.

[0056] The auxiliary condition determination unit 21b may include a stop determination unit 21j. The stop determination unit 21j determines whether a condition (auxiliary stop condition) for stopping the turning assistance by the wheel motors 25R and 25L is satisfied. For example, when the difference between the right wheel speed VR and the left wheel speed VL becomes larger than a threshold value, it may be determined that the auxiliary stop condition is satisfied, and the turning assistance by the wheel motors 25R and 25L may be stopped. This makes it possible to prevent the turning speed of the wheelchair 100 from becoming excessively high. The auxiliary condition determination unit 21b may stop only the additive correction when the difference between the right wheel speed VR and the left wheel speed VL becomes larger than a threshold value during turning.

[0057] [Correction Overview] The control device 20 controls the right wheel motor 25R and the left wheel motor 25L based on the common reference speed Vs. The common reference speed Vs functions as a target value set for the wheelchair speed. The common reference speed Vs is set based on, for example, the amount of operation of the assistance travel lever 52a. This allows the wheelchair 100 to travel at a speed that corresponds to the amount of operation. The common reference speed Vs may be a preset fixed value that does not depend on the amount of operation of the assistance travel lever 52a.

[0058] Hereinafter, driving with turning assistance by the wheel motors 25R and 25L will be referred to as "turning-assisted driving," and driving without turning assistance by the wheel motors 25R and 25L will be referred to as "normal driving."

[0059] [Normal driving] During normal driving, the control device 20 outputs a command value to the drive units 26R, 26L, which corresponds to the difference between the average of the right wheel speed VR and the left wheel speed VL ((VR + VL) / 2) and the common reference speed Vs. This drives the wheel motors 25R, 25L so that the wheelchair speed (average of the wheel speeds VR, VL) follows the common reference speed Vs.

[0060] As described above, the right wheel speed VR can be calculated based on, for example, the output (rotation speed) of the right speed sensor 31R and the radius of the right wheel 2R. Also, the left wheel speed VL can be calculated based on, for example, the output (rotation speed) of the left speed sensor 31L and the radius of the left wheel 2L. The average of the right wheel speed VR and the left wheel speed VL will be referred to below as the "left / right wheel average speed Vave."

[0061] [Turning Assistance] When the turning torque calculation unit 21a detects a force that turns the wheelchair 100, more specifically, when the above-mentioned assist start condition is satisfied, turning-assisted running is executed. During a left turn when a force that turns left is detected, the control device 20 increases the rotation speed of the right wheel motor 25R from the rotation speed corresponding to the common reference speed Vs, and decreases the rotation speed of the left wheel motor 25L from the rotation speed corresponding to the common reference speed Vs. As a result, the left turn is assisted by the wheel motors 25R and 25L while suppressing changes in the speed of the wheelchair 100.

[0062] Furthermore, when a force for turning right is detected, the control device 20 increases the rotation speed of the left wheel motor 25L from the rotation speed corresponding to the common reference speed Vs, while decreasing the rotation speed of the right wheel motor 25R from the rotation speed corresponding to the common reference speed Vs. This suppresses changes in the speed of the wheelchair 100, and the wheel motors 25R and 25L assist the turning right.

[0063] [Reference speed correction] The control device 20 calculates a reference speed for the right wheel 2R (right wheel reference speed Vs_R) and a reference speed for the left wheel 2L (left wheel reference speed Vs_L). FIG. 4A is a diagram for explaining the processing executed during turn-assisted running to the left. As shown in the diagram, during turn-assisted running to the left, the control device 20 adds (additive correction) a correction value (correction speed Vc) to the common reference speed Vs, for example, and sets the result of this addition correction as the right wheel reference speed Vs_R. The control device 20 also subtracts (subtractive correction) the same correction value (correction speed Vc) from the common reference speed Vs, and sets the result of this subtraction correction as the left wheel reference speed Vs_L.

[0064] The control device 20 then outputs a command value corresponding to the difference (Vs_R-Vave) between the right wheel reference speed Vs_R and the left and right wheel average speed Vave to the right drive unit 26R. As a result, the rotation speed of the right wheel motor 25R increases from the rotation speed corresponding to the common reference speed Vs.

[0065] The control device 20 also outputs a command value corresponding to the difference (Vs_L-Vave) between the left wheel reference speed Vs_L and the left and right wheel average speed Vave to the left drive unit 26L. As a result, the rotational speed of the left wheel motor 25L decreases from the rotational speed corresponding to the common reference speed Vs. This suppresses changes in the wheelchair speed, and the wheel motors 25R and 25L assist in turning left.

[0066] Similar processing is also executed during turn-assisted running in the right direction. Specifically, during turn-assisted running in the right direction, the control device 20 adds (additively corrects) a correction value (corrected speed Vc) to the common reference speed Vs, and sets the result of this addition correction as the left wheel reference speed Vs_L. The control device 20 also subtracts (subtractively corrects) the same correction value (corrected speed Vc) from the common reference speed Vs, and sets the result of this subtractive correction as the right wheel reference speed Vs_R.

[0067] The control device 20 then outputs a command value corresponding to the difference between the left wheel reference speed Vs_L and the left and right wheel average speed Vave to the right drive unit 26R. As a result, the rotation speed of the left wheel motor 25L increases from the rotation speed corresponding to the common reference speed Vs. The control device 20 also outputs a command value corresponding to the difference between the right wheel reference speed Vs_R and the left and right wheel average speed Vave to the right drive unit 26R. As a result, the rotation speed of the right wheel motor 25R decreases from the rotation speed corresponding to the common reference speed Vs. This suppresses changes in the wheelchair speed, while assisting the wheel motors 25R and 25L in turning to the right.

[0068] [Reference speed calculation section] The following describes in detail such control by the control device 20. As shown in Fig. 3, the reference speed calculation unit 21c has a common reference speed calculation unit 21d, a correction speed calculation unit 21e, and an individual wheel reference speed calculation unit 21f.

[0069] The common reference speed calculation unit 21d calculates the common reference speed Vs. For example, the common reference speed calculation unit 21d detects the operation amount (lever operation amount) of the assistance travel lever 52a and calculates the common reference speed Vs according to the lever operation amount. A map or a relational expression relating the lever operation amount and the common reference speed may be stored in advance in the storage unit 22.

[0070] When the reverse selection switch 52b is in the ON state, i.e., when the reverse mode is selected, the common reference speed calculation unit 21d may calculate a negative common reference speed Vs according to the lever operation amount. On the other hand, when the reverse selection switch 52b is in the OFF state, i.e., when the forward mode is selected, the common reference speed calculation unit 21d may calculate a positive common reference speed Vs according to the lever operation amount.

[0071] [Correction speed calculation section] The correction speed calculation unit 21e calculates a correction speed Vc to be added to or subtracted from the common reference speed Vs. The correction speed Vc may be set based on the input swing torque Th calculated by the swing torque calculation unit 21a. An upper limit Vc_max may be set in advance for the correction speed Vc. (Hereinafter, this upper limit Vc_max will be referred to as the "upper limit correction speed.") Then, the correction speed Vc may be calculated based on the swing torque Th and the upper limit correction speed Vc_max. The correction speed Vc may be calculated, for example, using the following equation (3):

number

[0072] The calculation process of the corrected speed Vc is not limited to the above example. The corrected speed calculation unit 21e may calculate the corrected speed Vc, for example, based on the turning torque Th detected by the turning torque calculation unit 21a and the speed of the wheelchair 100 (wheelchair speed Vwh). For example, the corrected speed Vc may be calculated based on the upper limit corrected speed Vc_max, the turning torque Th, and the wheelchair speed Vwh. The corrected speed Vc may be calculated, for example, using the following equation (4):

number

[0073] The speed influence ratio Rv may be, for example, relatively high when the wheelchair speed Vwh is in a low speed range and relatively low when the wheelchair speed Vwh is in a high speed range, or may gradually decrease as the wheelchair speed Vwh increases in some or all speed ranges.

[0074] 5A is a diagram showing an example of the relationship between the wheelchair speed Vwh and the speed influence rate Rv. A map showing such a relationship may be stored in the storage unit 22. The corrected speed calculation unit 21e may refer to this map and calculate the speed influence rate Rv according to the wheelchair speed Vwh.

[0075] In the example shown in FIG. 5A, in the low speed range (0 < Vwh ≤ Vwh1), the speed influence rate Rv is 100%, and in the medium speed range (Vwh2 < Vwh ≤ Vwh3), the speed influence rate Rv is 50%. Also, in the high speed range (Vwh3 < Vwh), the speed influence rate Rv gradually decreases according to the speed. The relationship between the wheelchair speed Vwh and the speed influence rate Rv is not limited to the example shown in FIG. 5A and may be changed as appropriate.

[0076] When using such a speed influence rate Rv, the corrected speed Vc calculated in the low speed range where the wheelchair speed Vwh is smaller than the speed Vwh1 is larger than that in the speed range (medium speed range or high speed range) where the wheelchair speed Vwh is larger than the speed Vwh1. As a result, the assistance for turning by the wheel motors 25R·25L also increases.

[0077] The torque influence rate Rt may gradually increase as the input turning torque Th increases, for example. FIG. 5B is a diagram showing an example of the relationship between the ratio of the input turning torque Th to the maximum value Th_max of the turning torque (turning torque ratio) and the torque influence rate Rt. A map representing such a relationship may be stored in the storage unit 22. The corrected speed calculation unit 21e may refer to this map and calculate the torque influence rate Rt according to the turning torque Th.

[0078] In the example shown in FIG. 5B, when the turning torque ratio is 10% or less, the torque influence rate Rt is 0. Also, when the turning torque ratio is higher than 10%, the torque influence rate Rt gradually increases as the turning torque ratio increases.

[0079] Although the wheelchair speed Vwh is used for calculating the corrected speed Vc, the turning torque Th may not be used. For example, the corrected speed calculation unit 21e may calculate the corrected speed Vc based on the upper limit corrected speed Vc_max and the wheelchair speed Vwh. In this case, the turning torque Th may not be used. The corrected speed calculation unit 21e may calculate the corrected speed Vc using, for example, the following formula (5).

Equation

[0080] [Each wheel reference speed calculation section (forward mode)] The individual wheel reference speed calculation unit 21f calculates a reference speed for the right wheel 2R (right wheel reference speed Vs_R) and a reference speed for the left wheel 2L (left wheel reference speed Vs_L).

[0081] When the wheelchair 100 turns left while moving forward, each wheel reference speed calculation unit 21f adds the corrected speed Vc to the common reference speed Vs (additive correction), and sets the result of this additive correction as the right wheel reference speed Vs_R. Also, each wheel reference speed calculation unit 21f subtracts the corrected speed Vc from the common reference speed Vs (subtractive correction), and sets the result of this subtractive correction as the left wheel reference speed Vs_L. That is, the reference speeds Vs_R·Vs_L are calculated as follows: Vs_R=Vs+Vc (additional correction) Vs_L=Vs-Vc (subtraction correction) (In the above two equations, Vs≧0, Vc>0)

[0082] By this processing, left turning is assisted by the wheel motors 25R and 25L. Furthermore, when the common reference speed Vs is low, the right wheel reference speed Vs_R becomes positive and the right wheel 2R moves forward, but the left wheel reference speed Vs_L becomes negative and the left wheel 2L moves backward, assisted by the left wheel motor 25L. As a result, turning in a narrow space is assisted.

[0083] When the wheelchair 100 turns right while moving forward, each wheel reference speed calculation unit 21f adds the correction speed Vc to the common reference speed Vs (additive correction) and sets the result of this addition correction as the left wheel reference speed Vs_L. Also, each wheel reference speed calculation unit 21f subtracts the correction speed Vc from the common reference speed Vs (subtractive correction) and sets the result of this subtractive correction as the right wheel reference speed Vs_R.

[0084] Here, "additive correction" means a correction that increases the wheel reference speed of one of the left wheel 2L and the right wheel 2R by the absolute value of the correction speed Vc compared to the common reference speed Vs. Conversely, "subtractive correction" means a correction that decreases the wheel reference speed of one of the left wheel 2L and the right wheel 2R by the absolute value of the correction speed Vc compared to the common reference speed Vs. Therefore, when the correction speed Vc is a positive value, Vs+Vc is an additive correction, and Vs-Vc is a subtractive correction. Conversely, when the correction speed Vc is a negative value, Vs+Vc is a subtractive correction, and Vs-Vc is an additive correction.

[0085] When the wheelchair 100 turns right while moving forward, the corrected speed Vc may be calculated as a negative value. For example, when the input turning torque Th is calculated using the above-mentioned formula (1) or formula (2), the input turning torque Th is calculated as a negative value when turning right. As a result, the corrected speed Vc calculated using formula (3) or formula (4) is also calculated as a negative value. In this case, the reference speed Vs_R·Vs_L may be calculated using the following formula: Vs_R=Vs+Vc (subtraction correction) Vs_L=Vs-Vc (additional correction) (In the above two equations, Vs≧0, Vc<0)

[0086] According to this processing, right turning is assisted by the wheel motors 25R and 25L. Furthermore, when the common reference speed Vs is low, the left wheel reference speed Vs_L becomes positive and the left wheel 2L moves forward, but the right wheel reference speed Vs_R becomes negative and the reverse movement of the right wheel 2R can be assisted by the left wheel motor 25L. As a result, turning in a narrow space is assisted.

[0087] The turning direction (left or right) of the wheelchair 100 can be determined based on the input turning torque Th calculated by the turning torque calculation unit 21a. For example, when the input turning torque Th is calculated from the above-mentioned formula (1), a positive input turning torque Th indicates a left turn, and a negative input turning torque Th indicates a right turn.

[0088] [Each wheel reference speed calculation section (reverse mode)] When the reverse selection switch 52b is in the on state, the reverse mode is selected. At this time, the common reference speed Vs calculated based on the lever operation amount may be a negative value. When the common reference speed Vs is calculated in this way, the additive correction and subtractive correction performed in the forward mode, that is, the correction of the wheel reference speeds Vs_L·Vs_R, may be performed as follows. In this specification, a left turn while reverse traveling means a turn in which the wheelchair 100 turns diagonally left, as shown in FIG. 4B(a). Furthermore, a right turn while reverse traveling means a turn in which the wheelchair 100 turns diagonally right, as shown in FIG. 4B(b).

[0089] When the wheelchair 100 turns left in the reverse mode (FIG. 4B(a)), each wheel reference speed calculation unit 21f adds the correction speed Vc to the common reference speed Vs (additive correction) and sets the result of the addition correction as the right wheel reference speed Vs_R. Also, each wheel reference speed calculation unit 21f may subtract the correction speed Vc from the common reference speed Vs (subtractive correction) and set the result of the subtractive correction as the left wheel reference speed Vs_L.

[0090] As described above, "additive correction" refers to a correction that increases the wheel reference speed of one of the left wheel 2L and the right wheel 2R by the absolute value of the correction speed Vc compared to the common reference speed Vs. Conversely, "subtractive correction" refers to a correction that decreases the wheel reference speed of one of the left wheel 2L and the right wheel 2R by the absolute value of the correction speed Vc compared to the common reference speed Vs.

[0091] When the wheelchair 100 turns left while moving backward, the corrected speed Vc may be calculated as a positive value. For example, when the input turning torque Th is calculated using the above-mentioned formula (1) or formula (2), the input turning torque Th is calculated as a positive value when turning left. As a result, the corrected speed Vc calculated using formula (3) or formula (4) is also calculated as a positive value. In this case, the reference speed Vs_R·Vs_L may be calculated using the following formula: Vs_R=Vs+Vc (additional correction) Vs_L=Vs-Vc (subtraction correction) (In the above two equations, Vs≦0, Vc>0)

[0092] As a result, turning to the left is assisted by the wheel motors 25R and 25L. Furthermore, when the absolute value of the common reference speed Vs (Vs<0) is small, the right wheel reference speed Vs_R becomes positive and the right wheel 2R moves forward, but the left wheel reference speed Vs_L becomes negative and the left wheel 2L moves backward, and the left wheel motor 25L can assist in turning in a narrow space.

[0093] Furthermore, when the wheelchair 100 turns right in the reverse mode (FIG. 4B(b)), each wheel reference speed calculation unit 21f subtracts the corrected speed Vc from the common reference speed Vs (subtraction correction), sets the result of the subtraction correction as the right wheel reference speed Vs_R, and adds the corrected speed Vc to the common reference speed Vs (addition correction), sets the result of the addition correction as the left wheel reference speed Vs_L. When the wheelchair 100 turns right in reverse, the corrected speed Vc may be calculated as a positive value. For example, when the input turning torque Th is calculated using the above-mentioned equation (1) or (2), the input turning torque Th is calculated as a positive value when turning left. As a result, the corrected speed Vc calculated using equation (3) or (4) is also calculated as a positive value. In this case, the reference speeds Vs_R·Vs_L may be calculated using the following equation: Vs_R=Vs+Vc (subtraction correction) Vs_L=Vs-Vc (additional correction) (In the above two equations, Vs≦0, Vc<0)

[0094] As a result, turning to the right is assisted by the wheel motors 25R and 25L. Furthermore, when the absolute value of the common reference speed Vs (Vs≦0) is small, the right wheel reference speed Vs_R becomes negative and the right wheel 2R moves backward, but the left wheel reference speed Vs_L becomes positive and the forward movement of the left wheel 2L can be assisted by the right wheel motor 25R. As a result, turning in a narrow space is assisted.

[0095] [Command value calculation section] The command value calculation unit 21m calculates a command value based on the difference (Vs_R-Vave) between the left and right wheel average speed Vave and the right wheel reference speed Vs_R, and outputs a signal corresponding to the command value to the right drive unit 26R. The command value calculation unit 21m also calculates a command value based on the difference (Vs_L-Vave) between the left and right wheel average speed Vave and the left wheel reference speed Vs_L, and outputs a signal corresponding to the command value to the left drive unit 26L. As the difference in speed increases, the command value also increases.

[0096] When normal driving is performed, in other words, when the assistance start condition is not satisfied, the wheel reference speed calculation unit 21f sets the common reference speed Vs to the right wheel reference speed Vs_R and the common reference speed Vs to the left wheel reference speed Vs_L. Then, the command value calculation unit 21m outputs a command value corresponding to the difference between the left and right wheel average speed Vave and the right wheel reference speed Vs_R to the right drive unit 26R. Also, the command value calculation unit 21m outputs a command value corresponding to the difference between the left and right wheel average speed Vave and the left wheel reference speed Vs_L to the left drive unit 26L.

[0097] By doing this, the torque (torque resulting from the corrected speed) additionally output by the left and right wheel motors 25R and 25L becomes 0, and no auxiliary torque is generated to turn the wheelchair 100. In other words, during normal driving, a current corresponding to the difference between the left and right wheel average speed Vave and the common reference speed Vs is supplied to both the right wheel motor 25R and the left wheel motor 25L, so no torque that would turn the wheelchair 100 is generated.

[0098] [Stop and turn assist unit] There are cases where the caregiver wants to turn the wheelchair 100 without substantially changing the position of the wheelchair 100. For example, the caregiver may change the direction of the wheelchair 100 in a narrow corridor. In such a case, if the wheelchair speed Vwh is 0 or close to 0, it becomes easier to turn with a small turning radius. To deal with such a situation, the wheelchair 100 may be provided with a stop / turn switch 52c (see FIG. 2). When the stop / turn switch 52c is turned on, the stop / turn assist unit 21g (see FIG. 3) sets the common reference speed Vs to a value equal to or less than a predetermined value (for example, substantially 0) regardless of the lever operation amount.

[0099] In this state, when the turning torque calculation unit 21a detects the turning torque Th, the correction speed calculation unit 21e, the wheel reference speed unit 21f, and the command value calculation unit 21m may execute the above-described processes. That is, the correction speed calculation unit 21e calculates the correction speed Vc based on the input turning torque Th, and the wheel reference speed unit 21f calculates the wheel reference speeds Vs_R·Vs_L based on the correction speed Vc and the common reference speed Vs (e.g., substantially 0). Then, the command value calculation unit 21m calculates a command value for the right wheel motor 25R based on the difference between the left and right wheel average speed Vave and the right wheel reference speed Vs_R, and calculates a command value for the left wheel motor 25L based on the difference between the left and right wheel average speed Vave and the left wheel reference speed Vs_L. This allows the turning of the wheelchair 100 to be assisted while maintaining the wheelchair speed at a small value.

[0100] The stop-turn switch 52c may be turned on, for example, when the switch is pressed and held down. In the on state, the stop-turn switch 52c may automatically transition to the off state, for example, when the turn ends. More specifically, the stop-turn switch 52c may automatically transition to the off state when the difference between the right wheel reference speed Vs_R and the left wheel reference speed Vs_L becomes smaller than a threshold value.

[0101] [Parameter adjustment section] The parameter adjustment unit 21p accepts a user operation (change command) and adjusts various parameters used in the above-mentioned processing. For example, the parameter adjustment unit 21p may accept a user operation and change the upper limit corrected speed Vc_max (see equation (3)) based on the operation. The parameter adjustment unit 21p may also adjust the assist start condition or the assist stop condition based on the user operation. For example, the parameter adjustment unit 21p may change the threshold value of the input turning torque Th, which is the condition for starting turning assistance, or change the wheelchair speed Vwh at which turning assistance is permitted.

[0102] As shown in Fig. 2, the wheelchair 100 may have an interface device 53 for receiving such user operations. The interface device 53 may be, for example, a touch panel or a display device equipped with a touch panel. The wheelchair 100 may also have a communication device 54 (see Fig. 2) that can communicate with a mobile terminal operated by the user.

[0103] [Processing flow] The following describes the flow of processing executed by the control device 20. Figures 6A and 6B are flow diagrams showing an example of the processing. The control device 20 repeatedly executes the processing shown in Figures 6A and 6B at a preset cycle.

[0104] First, the control device 20 (stop turn assist unit 21g) determines whether the stop turn switch 52c is in the on state (S101).

[0105] If the stop-turn switch 52c is not in the ON state, the control device 20 (common reference speed calculation unit 21d) detects the amount of lever operation and calculates the common reference speed Vs corresponding to that amount of lever operation (S102). Note that the amount of operation detected by the control device 20 in S102 is not limited to the amount of operation of the assistance travel lever 52a. For example, the rear operation input unit 52 may be provided with an operating member such as a dial or a button. The control device 20 may then detect the amount of operation performed on these members and calculate the common reference speed Vs corresponding to that amount of operation. The control device 20 also calculates the actual right wheel speed VR and left wheel speed VL based on the outputs of the speed sensors 31R and 31L (S103). The control device 20 (stop determination unit 21j) then determines whether the absolute value of the difference between the right wheel speed VR and the left wheel speed VL is smaller than a threshold value Vlim (S104).

[0106] If the absolute value is smaller than the threshold value Vlim ("Yes" in S104), the control device 20 (turning torque calculation unit 21a) calculates the input turning torque Th (S105). As described above, if the wheelchair 100 is provided with a turning torque sensor 32 (angular velocity sensor), the input turning torque Th may be calculated based on the output thereof. Alternatively, if such a sensor is not provided, the control device 20 may use equation (1) or equation (2) to calculate the input turning torque Th based on the wheel speeds VR·VL.

[0107] Next, the control device 20 (start determination unit 21i) determines whether the input turning torque Th is greater than a threshold value Tk (S106). If the input turning torque Th is greater than the threshold value Tk, the control device 20 determines that the assist start condition is satisfied. Note that in S106, the control device 20 may determine whether the average of the right wheel speed VR and the left wheel speed VL (left and right wheel average speed Vave) is smaller than a threshold value, in addition to whether the input turning torque Th is greater than the threshold value Tk. Then, if the left and right wheel average speed Vave is smaller than the threshold value, the control device 20 may determine that the assist start condition is satisfied.

[0108] If the assist start condition is satisfied ("Yes" in S106), the control device 20 (corrected speed calculation unit 21e) calculates the corrected speed Vc (S107). As described above, the corrected speed Vc is calculated, for example, with reference to equation (3) and based on the upper limit corrected speed Vc_max and the input turning torque Th. Alternatively, the corrected speed Vc may be calculated based on the upper limit corrected speed Vc_max, the input turning torque Th, and the wheelchair speed Vwh using equation (4).

[0109] Next, the control device 20 (each wheel reference speed calculation unit 21f) determines whether the wheelchair 100 is in forward mode (S108). Specifically, the each wheel reference speed calculation unit 21f determines whether the reverse selection switch 52b is in the on state. Here, if the reverse selection switch 52b is not in the on state, it is determined that the wheelchair 100 is in the forward mode.

[0110] When the wheelchair 100 is in forward mode ("Yes" in S108), the control device 20 (each wheel reference speed calculation unit 21f) adds the correction speed Vc to the common reference speed Vs and sets the result of the addition as the right wheel reference speed Vs_R (Vs+Vc, S111). Also, it subtracts the correction speed Vc from the common reference speed Vs and sets the result of the subtraction as the left wheel reference speed Vs_L (Vs-Vc, S111).

[0111] When the wheelchair 100 turns left, the corrected speed Vc may be calculated as a positive value in S107. For example, the corrected speed Vc calculated by equation (3) or (4) is calculated as a positive value when turning left. In this case, the reference speeds Vs_R·Vs_L are calculated by the following equation in S108. Vs_R=Vs+Vc (additional correction) Vs_L=Vs-Vc (subtraction correction) (In the above two equations, Vs>0, Vc>0)

[0112] Conversely, when the wheelchair 100 turns right, the corrected speed Vc may be calculated as a negative value in S107. For example, the corrected speed Vc calculated by equation (3) or (4) is calculated as a negative value when turning right. In this case, the reference speeds Vs_R·Vs_L are calculated by the following equation in S108. Vs_R=Vs+Vc (subtraction correction) Vs_L=Vs-Vc (additional correction) (In the above two equations, Vs>0, Vc<0)

[0113] Furthermore, when the wheelchair 100 is in reverse mode ("No" in S108), the control device 20 sets the common reference speed Vs corresponding to the lever operation amount detected in S102 to a negative value (Vs←Vs×(−1), S110). Then, the control device 20 (each wheel reference speed calculation unit 21f) adds the correction speed Vc to the common reference speed Vs, and sets the result of this addition as the right wheel reference speed Vs_R (Vs+Vc, S111). Also, it subtracts the correction speed Vc from the common reference speed Vs, and sets the result of this subtraction as the left wheel reference speed Vs_L (Vs−Vc, S111).

[0114] Even in the reverse mode, when the wheelchair 100 turns left, the corrected speed Vc is calculated as a positive value using equation (3) or equation (4). Then, the reference speeds Vs_R·Vs_L are calculated in S108 using the following equations. Vs_R=Vs+Vc (additional correction) Vs_L=Vs-Vc (subtraction correction) (In the above two equations, Vs<0, Vc>0)

[0115] Conversely, when the wheelchair 100 turns right, the corrected speed Vc is calculated as a negative value using equation (3) or equation (4). Then, the reference speeds Vs_R·Vs_L are calculated in S108 using the following equations. Vs_R=Vs+Vc (subtraction correction) Vs_L=Vs-Vc (additional correction) (In the above two equations, Vs<0, Vc<0)

[0116] Next, the control device 20 (command value calculation section 21m) calculates a command value based on the difference between the right wheel reference speed Vs_R obtained in S109 and the left and right wheel average speed Vave, and outputs a signal corresponding to the command value to the right drive unit 26R (S111). Similarly, the control device 20 calculates a command value based on the difference between the left wheel reference speed Vs_L and the left and right wheel average speed Vave, and outputs a signal corresponding to the command value to the left drive unit 26L (S111).

[0117] In S101, when the stop / turn switch 52c is in the on state ("Yes" in S101), the control device 20 (stop / turn assist unit 21g) sets the common reference speed Vs to 0 (S112). Then, the control device 20 executes the processes from S103 onwards. As a result, the wheelchair 100 turns with the assistance of the wheel motors 25R and 25L without changing its position.

[0118] Furthermore, if the absolute value of the difference between the right wheel speed VR and the left wheel speed VL is greater than the threshold value Vlim in S104 ("No" in S104), turning assistance by the wheel motors 25R and 25L is not appropriate. Therefore, the control device 20 sets the common reference speed Vs obtained in S102 as the right wheel reference speed Vs_R and the left wheel reference speed Vs_L without calculating the correction speed Vc (S113).

[0119] Similarly, if the input turning torque Th is smaller than the threshold value Tk in S106 ("No" in S106), it is determined that turning assistance by the wheel motors 25R and 25L is not necessary. Therefore, the control device 20 sets the common reference speed Vs obtained in S102 as the right wheel reference speed Vs_R and the left wheel reference speed Vs_L without calculating the correction speed Vc (S117).

[0120] Then, the control device 20 executes the process of S111. As a result, the torque (torque resulting from the corrected speed) additionally output by the left and right wheel motors 25R and 25L becomes 0, and no auxiliary torque is generated to turn the wheelchair 100. The left and right wheel average speed Vave follows the common reference speed Vs.

[0121] [Changes in reference speed, etc.] 7 is a time chart showing an example of changes in (a) input turning torque Th, (b) reference speeds Vs·Vs_R·Vs_L, and (c) output torque of wheel motors 25R·25L. Here, we will explain the changes when an assistant is trying to turn wheelchair 100 left.

[0122] At time t1, the input turning torque Th increases from 0 (FIG. 7(a)). Until time t2 is reached, the input turning torque Th is lower than the threshold value Tk (S106), so turning assistance does not start. Therefore, both the right wheel reference speed Vs_R and the left wheel reference speed Vs_L remain at the common reference speed Vs (FIG. 7(b)).

[0123] At time t2, when the input turning torque Th exceeds the threshold value Tk, turning assistance is initiated. Then, the corrected speed Vc is calculated based on the input turning torque Th (FIG. 7(b)). As a result, the right wheel reference speed Vs_R increases from the common reference speed Vs, while the left wheel reference speed Vs_L decreases from the common reference speed Vs.

[0124] Therefore, the difference ΔV_R between the left and right wheel average speed Vave and the right wheel reference speed Vs_R increases, and the difference ΔV_L between the left and right wheel average speed Vave and the left wheel reference speed Vs_L decreases. As a result, the output torque of the right wheel motor 25R increases from the output torque corresponding to the common reference speed Vs that was output up to time t2. As a result, the rotation speed of the right wheel motor 25R becomes higher than the rotation speed corresponding to the common reference speed Vs.

[0125] Conversely, the output torque of the left wheel motor 25L decreases from the output torque corresponding to the common reference speed Vs that was output up to time t2. As a result, the rotational speed of the left wheel motor 25L decreases below the rotational speed corresponding to the common reference speed Vs. This allows the wheel motors 25R and 25L to assist in turning the wheelchair 100.

[0126] In the example shown in Fig. 7, the input turning torque Th gradually increases until time t3, and therefore the correction speed Vc also gradually increases. As a result, the output torque of the right wheel motor 25R gradually increases, and the output torque of the left wheel motor 25L gradually decreases. During the period from time t3 to t4, the input turning torque Th gradually decreases, and therefore the correction speed Vc also gradually decreases. As a result, the output torque of the right wheel motor 25R gradually decreases, and the output torque of the left wheel motor 25L gradually increases.

[0127] 8 is a time chart showing another example of changes in (a) input turning torque Th, (b) reference speeds Vs·Vs_R·Vs_L, and (c) output torque of wheel motors 25R·25L. In FIG. 8, the changes up to time t3 are the same as in the example of FIG. 7, and therefore a description thereof will be omitted.

[0128] As described above, the stop determination unit 21j determines whether the assist stop condition is satisfied. The assist stop condition is, for example, that the absolute value of the difference between the right wheel speed VR and the left wheel speed VL is greater than the threshold value Vlim, as shown in S104 of FIG. 6A. In the example of FIG. 8, at time t3, the absolute value of the difference between the right wheel speed VR and the left wheel speed VL exceeds the threshold value Vlim. Therefore, from time t3 onwards, the corrected speed Vc according to the input turning torque Th is not calculated, and the common reference speed Vs is set as the right wheel reference speed Vs_R and the left wheel reference speed Vs_L (see FIG. 8(b)). Therefore, from time t3 onwards, both the output torque of the right wheel motor 25R and the output torque of the left wheel motor 25L are set based on the difference ΔV between the common reference speed Vs and the left / right wheel average speed Vave, and are set to the same value (the torque before the turning assistance started (the torque at time t2)). This causes the turning assistance by the wheel motors 25R and 25L to stop.

[0129] Unlike the example shown in FIG. 8, when the absolute value of the difference between the right wheel speed VR and the left wheel speed VL exceeds the threshold value Vlim, the correction speed Vc may be gradually decreased rather than being stopped.

[0130] [summary] (1) When a force (torque) that turns the wheelchair 100 leftward is detected, the control device 20 increases the rotational speed of the right wheel motor 25R from the rotational speed that corresponds to the common reference speed Vs and decreases the rotational speed of the left wheel motor 25L from the rotational speed that corresponds to the common reference speed Vs. Furthermore, when a force that turns the wheelchair 100 rightward is detected, the control device 20 increases the rotational speed of the left wheel motor 25L from the rotational speed that corresponds to the common reference speed Vs and decreases the rotational speed of the right wheel motor 25R from the rotational speed that corresponds to the common reference speed Vs. This makes it possible to reduce the burden on the caregiver when turning the wheelchair 100 while suppressing changes in the speed of the wheelchair 100.

[0131] (2) In (1), when a force that turns the wheelchair 100 to the left is detected, the control device 20 performs an additive correction, which is an addition of the correction speed Vc, and controls the right wheel motor 25R based on the result of the additive correction (right wheel reference speed Vs_R), and performs a subtractive correction, which is a subtraction of the correction speed Vc, and controls the left wheel motor 25L based on the result of the subtractive correction (left wheel reference speed Vs_L).

[0132] (3) In (1) or (2), when turning left, the control device 20 controls the right wheel motor 25R based on the addition result obtained by adding the correction speed Vc to the common reference speed Vs, and controls the left wheel motor 25L based on the subtraction result obtained by subtracting the correction speed Vc from the common reference speed Vs. When turning right, the control device 20 controls the left wheel motor 25L based on the addition result obtained by adding the correction speed Vc to the common reference speed Vs, and controls the right wheel motor 25R based on the subtraction result obtained by subtracting the correction speed Vc from the common reference speed Vs.

[0133] (4) In (2), when the difference between the right wheel speed VR obtained from the right speed sensor 31R and the left wheel speed VL obtained from the left speed sensor 31L satisfies a predetermined condition (VR-VL>Vlim or VR-VL<-Vlim), the control device 20 relaxes at least one of the additive correction and the subtractive correction, thereby preventing the turning speed from becoming excessively high.

[0134] (5) In any of (1) to (4), the control device 20 calculates the corrected speed Vc based on at least one of the input turning torque Th and the wheelchair speed Vwh, and a preset upper limit value for the corrected speed Vc (upper limit corrected speed Vc_max). This makes it possible to increase the corrected speed Vc in accordance with the force that turns the wheelchair 100, while keeping the corrected speed Vc at a value smaller than the upper limit corrected speed Vc_max. Also, the corrected speed Vc can be set to a value that corresponds to the wheelchair speed Vwh, while keeping the corrected speed Vc at a value smaller than the upper limit corrected speed Vc_max.

[0135] (6) In any of (1) to (5), the control device 20 calculates the common reference speed Vs according to the amount of operation of the assistance travel lever 52a. This allows the wheelchair 100 to travel at a speed according to the amount of operation. Note that the rear operation input unit 52 may be provided with an operation member such as a dial or button instead of the assistance travel lever 52a. The control device 20 may then detect the amount of operation of these and calculate the common reference speed Vs according to the amount of operation.

[0136] (7) In any of (1) to (6), the control device 20 calculates the corrected speed Vc based on the force (input turning torque Th) acting on the wheelchair 100. This allows assistance of a magnitude corresponding to the force applied to the wheelchair 100 by the caregiver to be obtained.

[0137] (8) In any of (1) to (7), the control device 20 calculates the force that turns the wheelchair 100 based on the angular velocity of the wheelchair 100 about the vertical axis.

[0138] (9) In any of (1) to (8), the control device 20 controls the right wheel motor 25R and the left wheel motor 25L based on the difference between the average of the right wheel speed and the left wheel speed (left and right wheel average speed Vave) and the common reference speed Vs. When the control device 20 detects a force that turns the wheelchair 100, it adds a correction speed Vc to one of the left and right wheel average speed Vave or the common reference speed Vs, and controls one of the right wheel motor 25R and the left wheel motor 25L based on the result of the addition. Also, it subtracts the correction speed Vc from one of the left and right wheel average speed Vave or the common reference speed Vs, and controls the other of the right wheel motor 25R and the left wheel motor 25L based on the result of the subtraction.

[0139] (10) In any of (2) to (9), the control device 20 calculates the corrected speed Vc based on the wheelchair speed Vwh. This makes it possible to suppress, for example, sudden turns at high speeds.

[0140] In (11) and (10), the corrected speed Vc calculated in the low-speed range where the speed of the wheelchair 100 is lower than the threshold Vwh1 (FIG. 5A) is greater than the corrected speed Vc calculated in the speed range (medium speed range, high speed range) where the speed of the wheelchair 100 is higher than the threshold Vwh1. This makes it possible to suppress sudden turns at high speeds.

[0141] (12) In any of (1) to (11), the control device 20 detects the operation of the stop / turn switch 52c and limits the common reference speed Vs to a predetermined value or less based on the operation. This allows the wheel motors 25R and 25L to assist the turning of the wheelchair 100 while keeping the speed low. As a result, the wheelchair can easily turn in a narrow space.

[0142] (13) In any of (2) to (13), the control device 20 receives a command from the user to change the upper limit value of the correction speed Vc (upper limit correction speed Vc_max). This prevents turning assistance of a magnitude unintended by the user.

[0143] In (14)(2), when the common reference speed Vs is lower than the correction speed Vc, the control device 20 performs additive correction to make the rotation speed of one of the right wheel motor 25R and the left wheel motor 25L a positive value, and performs subtractive correction to make the rotation speed of the other of the right wheel motor 25R and the left wheel motor 25L a negative value. This enables turning in narrow spaces with a light load.

[0144] [Other examples] It should be noted that the drive system proposed in the present disclosure is not limited to the above-described example.

[0145] [Example of correcting wheel speed] For example, in the above example, the common reference speed Vs is corrected by the correction speed Vc, but the wheel speeds VR·VL may be corrected by the correction speed Vc.

[0146] For example, when turning left, the correction speed Vc may be subtracted from the left and right wheel average speed Vave, and a command value corresponding to the difference between the subtraction result and the common reference speed Vs may be output to the right drive unit 26R. Alternatively, the correction speed Vc may be added to the left and right wheel average speed Vave, and a command value corresponding to the difference between the addition result and the common reference speed Vs may be output to the left drive unit 26L. This increases the output torque of the right wheel motor 25R, so that the rotation speed of the right wheel motor 25R becomes higher than the rotation speed corresponding to the common reference speed Vs. Conversely, the output torque of the left wheel motor 25L decreases, so that the rotation speed of the left wheel motor 25L becomes lower than the rotation speed corresponding to the common reference speed Vs.

[0147] Furthermore, when turning right, the correction speed Vc may be subtracted from the left and right wheel average speed Vave, and a command value corresponding to the difference between the subtraction result and the common reference speed Vs may be output to the left drive unit 26L. At this time, the correction speed Vc may be added to the left and right wheel average speed Vave, and a command value corresponding to the difference between the addition result and the common reference speed Vs may be output to the right drive unit 26R. As a result, the output torque of the left wheel motor 25L increases, so the rotation speed of the left wheel motor 25L becomes higher than the rotation speed corresponding to the common reference speed Vs. Conversely, the output torque of the right wheel motor 25R decreases, so the rotation speed of the right wheel motor 25R becomes lower than the rotation speed corresponding to the common reference speed Vs. [Other examples of reference speed]

[0148] In the above example, the speed in the longitudinal direction is used as the common reference speed Vs. However, the common reference speed Vs may be a reference value for the rotational speed of the wheels 2R and 2L or the rotational speed of the wheel motors 25R and 25L. In this case, the correction speed Vc calculated with reference to Figures 5A, 5B, etc. may be a correction value for the rotational speed of the wheels 2R and 2L.

[0149] In this case, when turning left, the control device 20 increases the rotation speed of the right wheel motor 25R from a reference rotation speed (common reference speed) and decreases the rotation speed of the left wheel motor 25L from the common rotation speed (common reference speed). Conversely, when turning right, the control device 20 increases the rotation speed of the left wheel motor 25L from the reference rotation speed (common reference speed) and decreases the rotation speed of the right wheel motor 25R from the common rotation speed (common reference speed). [Another example of correction speed]

[0150] In the above description, the corrected speed Vc is calculated using equation (3) or equation (4). Therefore, the corrected speed Vc is a positive value when turning left and a negative value when turning right. Therefore, when turning left, Vs+Vc is an additive correction and Vs-Vc is a subtractive correction. When turning right, Vs+Vc is a subtractive correction and Vs-Vc is an additive correction. However, the corrected speed Vc may be calculated to be a positive value both when turning left and right. In this case, Vs+Vc may be implemented as an additive correction and Vs-Vc may be implemented as a subtractive correction both when turning left and right. [Explanation of symbols]

[0151] 2L: left wheel, 2R: right wheel, 4: body frame, 6: seat, 7: handle grip, 8: armrest, 9: backrest, 11: battery, 20: control device, 21: calculation unit, 21a: turning torque calculation unit, 21b: auxiliary condition determination unit, 21c: reference speed calculation unit, 21d: common reference speed calculation unit, 21e: correction speed calculation unit, 21f: individual wheel reference speed calculation unit, 21g: stop turning assistance unit, 21i: start determination unit, 21j: stop determination unit, 21m: command value calculation unit, 21p: parameter adjustment unit, 22: memory unit, 25L : Left wheel motor, 25R: Right wheel motor, 26L: Left drive unit, 26R: Right drive unit, 31R: Right speed sensor, 31L: Left speed sensor, 32: Turning torque sensor, 51: Front operation input unit, 51a: Travel operation stick, 52: Rear operation input unit, 52a: Assisted travel lever, 52b: Reverse selection switch, 52c: Stop turning switch, 53: Interface device, 54: Communication device, 100: Electric wheelchair, Vs_L: Left wheel reference speed, Vs_R: Right wheel reference speed, Vwh: Wheelchair speed.

Claims

1. 1. A drive system for mounting on an electric wheelchair having a right wheel and a left wheel, comprising: a right wheel motor for driving the right wheel; a left wheel motor for driving the left wheel; means for detecting an external force acting to turn the electric wheelchair; a control device that controls the right wheel motor and the left wheel motor based on a common reference speed; and The control device During a left turn when the force causing the electric wheelchair to turn left is detected, the rotation speed of the right wheel motor is increased from the rotation speed corresponding to the common reference speed, and the rotation speed of the left wheel motor is decreased from the rotation speed corresponding to the common reference speed, When the force for turning the electric wheelchair to the right is detected, the rotation speed of the left wheel motor is increased from the rotation speed corresponding to the common reference speed, and the rotation speed of the right wheel motor is decreased from the rotation speed corresponding to the common reference speed. A drive system for mounting on an electric wheelchair.

2. When the force causing the electric wheelchair to turn is detected, the control device performing a first correction, which is either addition or subtraction of a correction value, and controlling one of the right wheel motor and the left wheel motor based on a result of the first correction; A second correction, which is the other of the addition and subtraction of the correction value, is performed, and the other of the right wheel motor and the left wheel motor is controlled based on the result of the second correction.

10. A drive system for mounting on a power wheelchair according to claim 1.

3. The control device During the left turn, the right wheel motor is controlled based on an addition result obtained by adding a correction value to the common reference speed, and the left wheel motor is controlled based on a subtraction result obtained by subtracting the correction value from the common reference speed. During the right turn, the left wheel motor is controlled based on an addition result obtained by adding a correction value to the common reference speed, and the right wheel motor is controlled based on a subtraction result obtained by subtracting the correction value from the common reference speed.

10. A drive system for mounting on a power wheelchair according to claim 1.

4. a right speed sensor that outputs a signal corresponding to the speed of the right wheel; a left speed sensor that outputs a signal corresponding to the speed of the left wheel; When a difference between the speed obtained from the right speed sensor and the speed obtained from the left speed sensor satisfies a predetermined condition, the control device relaxes at least one of the first correction and the second correction so as to reduce a difference between the rotation speed of the left wheel motor and the rotation speed of the right wheel motor.

3. A drive system for mounting on a power wheelchair according to claim 2.

5. The control device calculates the correction value based on at least one of the force for turning the electric wheelchair and the speed of the electric wheelchair, and a preset upper limit value for the correction value.

3. A drive system for mounting on a power wheelchair according to claim 2.

6. The control device calculates the common reference speed in accordance with an amount of operation applied to an operation member provided in the electric wheelchair.

10. A drive system for mounting on a power wheelchair according to claim 1.

7. The control device calculates the correction value based on the force acting on the electric wheelchair from the outside.

3. A drive system for mounting on a power wheelchair according to claim 2.

8. The control device calculates the force for turning the electric wheelchair based on the angular velocity of the electric wheelchair about a vertical axis.

10. A drive system for mounting on a power wheelchair according to claim 1.

9. a right speed sensor that outputs a signal corresponding to the speed of the right wheel; a left speed sensor that outputs a signal corresponding to the speed of the left wheel; the control device controls the right wheel motor and the left wheel motor based on a difference between the average of the right wheel speed and the left wheel speed and the common reference speed; When the control device detects the force that turns the electric wheelchair, adding a correction value to one of the average and the common reference speed, and controlling one of the right wheel motor and the left wheel motor based on the result of the addition; a correction value is subtracted from one of the average speed and the common reference speed, and the other of the right wheel motor and the left wheel motor is controlled based on the result of the subtraction; 10. A drive system for mounting on a power wheelchair according to claim 1.

10. The control device calculates the correction value based on the speed of the electric wheelchair.

3. A drive system for mounting on a power wheelchair according to claim 2.

11. The correction value calculated when the speed of the electric wheelchair is a first speed that is smaller than a threshold value is larger than the correction value calculated when the speed of the electric wheelchair is a second speed that is larger than a threshold value.

11. A drive system for mounting on a power wheelchair according to claim 10.

12. The control device detects an operation performed by an assistant on an operating member provided on the electric wheelchair, and limits the common reference speed to a predetermined value or less based on the operation.

10. A drive system for mounting on a power wheelchair according to claim 1.

13. The control device receives a command from a user to change the upper limit of the correction value.

10. A drive system for mounting on a power wheelchair according to claim 1.

14. When the common reference speed is lower than the correction value, the control device makes the rotation speed of one of the right wheel motor and the left wheel motor a positive value by the first correction, and makes the rotation speed of the other of the right wheel motor and the left wheel motor a negative value by the second correction.

3. A drive system for mounting on a power wheelchair according to claim 2.

15. A drive system according to claim 1; The right wheel and the left wheel Electric wheelchair with

16. A control method for an electric wheelchair having a right wheel, a left wheel, a right wheel motor for driving the right wheel, and a left wheel motor for driving the left wheel, comprising: detecting an external force acting to turn the electric wheelchair; controlling the right wheel motor and the left wheel motor based on a common reference speed; The control step includes: a step of increasing the rotation speed of the right wheel motor from the rotation speed corresponding to a common reference speed and decreasing the rotation speed of the left wheel motor from the rotation speed corresponding to the reference speed, the step being executed when the force causing the electric wheelchair to turn left is detected; a step of increasing the rotation speed of the left wheel motor from the rotation speed corresponding to a reference speed and decreasing the rotation speed of the right wheel motor from the rotation speed corresponding to the reference speed, which is executed when the force causing the electric wheelchair to turn right is detected; A method for controlling an electric wheelchair, comprising:

17. A program for causing a computer to function as a control device for an electric wheelchair having a right wheel, a left wheel, a right wheel motor for driving the right wheel, and a left wheel motor for driving the left wheel, the program comprising: means for detecting a force acting from the outside to turn the electric wheelchair; causing the computer to function as a control means for controlling the right wheel motor and the left wheel motor based on a common reference speed; The control means means for increasing the rotation speed of the right wheel motor from the rotation speed corresponding to the common reference speed and decreasing the rotation speed of the left wheel motor from the rotation speed corresponding to the common reference speed when the force causing the electric wheelchair to turn left is detected; means for increasing the rotation speed of the left wheel motor from the rotation speed corresponding to the common reference speed and decreasing the rotation speed of the right wheel motor from the rotation speed corresponding to the common reference speed when the force for turning the electric wheelchair to the right is detected. program.

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