JP7827072B2 - Electric vehicles - Google Patents

Description

The present invention relates to an electric vehicle.

Patent Document 1 discloses an electric wheelchair. This electric wheelchair includes an operating force detector, a motor for propelling the vehicle, and a control circuit. The operating force detector includes a handle protruding from the rear of the vehicle and a potentiometer.
When the operator moves the handle forward or backward from the neutral position, the output of the potentiometer changes in accordance with the displacement, and the output of the potentiometer is sent to a control circuit.
The control circuit obtains the displacement of the handle based on the output of the potentiometer.
The control circuit controls the motor to move the vehicle forward when the handle is displaced forward by the operator, and controls the motor to move the vehicle backward when the handle is displaced backward.

Japanese Patent Application Publication No. 10-336803

The control circuit controls the motor based on the displacement of the handle, and therefore controls the vehicle speed regardless of the walking speed of the operator.
Therefore, the walking speed of the operator and the vehicle speed do not necessarily match, and if there is a difference between the walking speed of the operator and the traveling speed of the electric wheelchair, the distance between the operator and the vehicle may become closer or farther. In such cases, the operator must adjust the amount of operation of the handlebars to walk in accordance with the vehicle speed, which poses a problem of poor operability.
The above-mentioned problem is not limited to electric wheelchairs, but occurs in any electric vehicle that detects the operating force of the operator and travels together with the operator.

An electric vehicle according to an embodiment of the present disclosure comprises a vehicle body, a drive mechanism for propelling the vehicle body, a control device for controlling the drive mechanism by providing a command value to the drive mechanism, a first grip movable in the fore-and-aft direction of the vehicle body, and a first operating unit having a first detection unit for detecting a first displacement amount of the first grip in the fore-and-aft direction relative to the vehicle body, and the control device comprises a processing unit that executes a generation process for generating the command value using a model including an elastic term based on the first displacement amount and a viscous term based on the derivative of the first displacement amount.

This disclosure provides good operability in electric vehicles.

FIG. 1 is a perspective view of an electric wheelchair according to an embodiment. FIG. 2 is a cross-sectional view of the first operating unit. FIG. 3 is a block diagram showing an example of a configuration for controlling the operation of a motor in an electric wheelchair. FIG. 4 is a diagram showing a manner in which an operator operates the electric wheelchair. FIG. 5 is a block diagram showing an example of the processing contents executed by the processing unit of the control device. FIG. 6 is a plan view of the electric wheelchair.

First, the contents of the embodiment will be listed and explained.
[Overview of the embodiment]
(1) An electric vehicle that is an embodiment of the present disclosure includes a vehicle body, a drive mechanism that drives the vehicle body, a control device that controls the drive mechanism by providing a command value to the drive mechanism, a first grip that can move in the fore-and-aft direction of the vehicle body, and a first operating unit that has a first detection unit that detects a first displacement amount of the first grip in the fore-and-aft direction relative to the vehicle body, and the control device includes a processing unit that executes a generation process that generates the command value using a model that includes an elastic term based on the first displacement amount and a viscous term based on a derivative value of the first displacement amount.

With the above configuration, the drive mechanism is controlled using a model including an elastic term based on the first displacement amount and a viscous term based on the derivative of the first displacement amount, so the drive mechanism can be controlled so that the movement of the vehicle body relative to the first displacement amount mimics mechanical impedance characteristics. As a result, when controlling the speed of the vehicle body to maintain a constant distance between the operator and the vehicle body, it is possible to prevent the operator from walking at the same speed as the vehicle body, resulting in good operability.

(2) In the above-described electric vehicle, it is preferable that the generation process includes a thrust calculation process that uses the model to determine a target thrust, which is a target value of thrust in the longitudinal direction, and a command value generation process that generates the command value based on the target thrust.
In this case, the control device can generate a command value based on the target thrust.

(3) Furthermore, if the electric vehicle further includes an acquisition unit that acquires speed information indicating the traveling speed of the vehicle body, it is preferable that in the propulsion force calculation process, the target propulsion force is calculated based on the calculation result of the model and the longitudinal deceleration force obtained based on the speed information.
In this case, the target thrust can be calculated by taking into account deceleration based on frictional forces and other factors that occur in response to the vehicle's speed, and by limiting the vehicle's running speed, thereby enabling more precise speed control and achieving better operability.

(4) It is preferable that the drive mechanism includes a pair of left and right drive wheels, a pair of motors that drive the pair of drive wheels, and a pair of drive circuits that drive the pair of motors based on the command value.
In this case, the control device can control the speed of the vehicle body by individually controlling the pair of motors.

(5) When an operator of an electric vehicle that is undergoing speed control attempts to turn the vehicle body in a predetermined direction via the first operating unit, the pair of drive circuits attempt to maintain an operating state based on the command value, and therefore control the pair of motors to generate torque for turning in the direction opposite to the predetermined direction. Therefore, the current values flowing through the pair of motors represent the external force acting on the vehicle body via the first operating unit.
Therefore, if the electric vehicle further includes a pair of current detection units that detect the currents flowing through the pair of motors, it is preferable that the processing unit executes an external force calculation process to determine the external force acting on the vehicle body based on a pair of current values detected by the pair of current detection units, and that in the generation process, the command value is generated based on the calculation result using the model and the external force.
This makes it possible to control the speed of the vehicle body based on the first displacement amount of the first operating unit and the external force acting on the vehicle body via the first operating unit.

(6) In a case where the electric vehicle further includes a pair of rotation detectors that detect the rotation speeds of the pair of motors, the generation process may include a thrust calculation process that uses the model to determine a target thrust, which is a target value of thrust in the longitudinal direction; a turning force calculation process that determines a target turning force, which is a target value of turning force in the turning direction of the vehicle body, based on the external force and the output of the pair of rotation detectors; and a command value generation process that generates a pair of command values for each of the pair of motors based on the target thrust and the target turning force.
In this case, the target force for moving the vehicle body can be controlled separately as a forward/rearward propulsion force and a turning force in the turning direction, thereby enabling the speed of each of the pair of motors to be controlled appropriately.

(7) When the external forces include an external force in the longitudinal direction and an external force in the turning direction, and the propulsion force calculation process calculates the target propulsion force based on the calculation results of the model and the external force in the longitudinal direction, the turning force calculation process may be configured to calculate the target turning force based on the external force in the turning direction and the outputs of the pair of rotation detectors.
In this case, by dividing the external force into an external force in the longitudinal direction and an external force in the turning direction, the target propulsive force and the target turning force can be calculated with higher accuracy.

(8) When the electric vehicle further includes a second operating unit having a second grip movable in the fore-and-aft direction and a second detection unit that detects a second displacement amount of the second grip in the fore-and-aft direction relative to the vehicle body, the first operating unit is provided on the left side of the vehicle body and the second operating unit is provided on the right side of the vehicle body, and the generation process includes a turning speed calculation process that calculates a target turning speed, which is a target value of the turning speed in the turning direction, based on the external force and the difference between the first displacement amount and the second displacement amount, the turning force calculation process calculates the target turning force based on the target turning speed and the output of the pair of rotation detectors.
In this case, for example, an upper limit and a lower limit may be set for the value obtained from the difference, and when the difference is extremely large or extremely small, an upper limit or a lower limit may be set for the value obtained from the difference, thereby providing a dead band for the difference. This places a limit on the movement in the turning direction based on the difference, making it possible to prevent the operator from making an unintended movement.

(9) Furthermore, if the electric vehicle further includes a wheelchair section, it is preferable that the vehicle body is the vehicle body of the wheelchair section.

[Details of the embodiment]
Preferred embodiments will now be described with reference to the drawings.
[Overall structure]
1 is a perspective view of an electric wheelchair according to an embodiment. This electric wheelchair 1 has a function of assisting the operator by driving the drive wheels of the electric wheelchair 1 when pushed from behind by the operator.

The electric wheelchair 1 comprises a wheelchair section 2 , a drive mechanism 4 , a control box 6 , a first operating section 10 , and a second operating section 12 .
The wheelchair section 2 is a typical wheelchair, and includes a vehicle body 2a mainly composed of a frame made of metal pipes or the like, a pair of main wheels 2b provided on the left and right sides of the vehicle body 2a, and a pair of casters 2c also provided on the vehicle body 2a. The vehicle body 2a has a seat 2a1 on which a passenger sits and a backrest 2a2.
The electric wheelchair 1 is constructed by mounting a drive mechanism 4, a control box 6, a first operating unit 10, and a second operating unit 12 on a wheelchair unit 2 that can be used as a wheelchair.

In the following description, the direction in which the occupant faces when riding in the electric wheelchair 1 (the direction in which the backrest portion 2a2 faces forward) is referred to as the forward direction, and the opposite direction is referred to as the rearward direction. Therefore, the occupant rides facing the front of the electric wheelchair 1. Additionally, the direction facing the left side as seen from the occupant's perspective is referred to as the leftward direction, and the direction facing the right side as seen from the occupant's perspective is referred to as the rightward direction.

The drive mechanism 4 includes a pair of drive units 14. The pair of drive units 14 are fixed to the left and right sides of the vehicle body 2a. The pair of drive units 14 are arranged on the vehicle inward side of the pair of main wheels 2b.
Each of the pair of left and right drive units 14 includes a base plate 14 a , an arm 14 b , a drive wheel 14 c , and a motor 15 .
The base plate 14a is fixed to the frame of the vehicle body 2a, thereby mounting the drive unit 14 to the wheelchair section 2.
The arm 14b is provided on the surface of the base plate 14a facing inward of the vehicle. The arm 14b is fixed to the base plate 14a so as to be swingable up and down. A motor 15 and a drive wheel 14c are provided at the tip of the arm 14b. The arm 14b supports the drive wheel 14c so that it can rotate freely. The arm 14b elastically biases the drive wheel 14c downward. As a result, the arm 14b presses the drive wheel 14c against the road surface to bring it into contact with the road.

The motor 15 is an in-wheel motor and is provided inside the drive wheel 14c. The rotor (not shown) of the motor 15 can rotate integrally with the drive wheel 14c. The stator (not shown) of the motor 15 is fixed to the arm 14b side. This allows the motor 15 to rotate and drive the drive wheel 14c. The motor 15 is connected to a battery, control device, etc. in the control box 6 via a cable (not shown). The cable is inserted into the arm 14b and connects the motor 15 to the control box 6.

The drive wheels 14c are supported by the arms 14b so as to be rotatable about central axes parallel to the left-right direction. The drive wheels 14c are driven to rotate by the motor 15 while in contact with the road surface.
The pair of left and right motors 15 drives the pair of left and right drive wheels 14c, causing the wheelchair section 2 (vehicle body 2a) to move.

The vehicle body 2a has a pair of left and right support pipes 2a3 that support the backrest 2a2. A pair of protrusions 2a4 that protrude rearward from the backrest 2a2 are provided at the upper ends of the pair of support pipes 2a3. The pair of protrusions 2a4 are pipes that have openings at their rear ends.
The first operating portion 10 and the second operating portion 12 are provided on the pair of protruding portions 2a4.
The first operating unit 10 is disposed on the upper left side of the backrest 2a2, and the second operating unit 12 is disposed on the upper right side of the backrest 2a2.
The first operating unit 10 has a first grip 20. The second operating unit 12 has a second grip 30.

FIG. 2 is a cross-sectional view of the first operating unit 10.
As shown in FIG. 2A, the first operating unit 10 has a potentiometer 21 in addition to the first grip 20.
The first grip 20 is attached to the tip of the protruding portion 2a4 on the left side of the vehicle. The first grip 20 has a tubular portion 20a and a bottom portion 20b. The bottom portion 20b closes the rear opening of the tubular portion 20a. The tubular portion 20a is attached to the outer periphery of the protruding portion 2a4. The tubular portion 20a is movable while sliding along the outer periphery of the protruding portion 2a4.
Therefore, the first grip 20 is movable along the axial direction of the protruding portion 2a4. The protruding portion 2a4 extends in the front-rear direction. Therefore, the first grip 20 is movable in the front-rear direction relative to the vehicle main body 2a.

The potentiometer 21 is a sensor (first detection unit) for detecting the amount of displacement in the front-rear direction of the first grip 20. The potentiometer 21 is provided inside the protrusion 2a4. The potentiometer 21 includes a main body 21a and a rod 21b.
The main body 21a is fixed to the protrusion 2a4.
The rod 21b extends rearward from the main body 21a. The rod 21b passes through the inside of the cylindrical portion 20a and the protruding portion 2a4. The rod 21b is movable in the axial direction relative to the main body 21a. The potentiometer 21 detects and outputs the amount of displacement of the rod 21b in the axial direction.
A tip end 21b1 of the rod 21b is fixed to the bottom portion 20b. Therefore, the rod 21b moves in the front-rear direction together with the first grip 20. This allows the potentiometer 21 to detect the amount of front-rear displacement of the first grip 20 relative to the vehicle body 2a.
The potentiometer 21 is connected to a control device (to be described later) in the control box 6. The output of the potentiometer 21 is given to the control device.

In addition to the potentiometer 21, a sleeve 22, a front bush 23, a rear bush 24, and a spring 25 are provided inside the protruding portion 2a4.
The sleeve 22 is a cylindrical member that is inserted into and fixed to the inner circumferential surface of the protruding portion 2a4.
The front bushing 23 , the rear bushing 24 , and the spring 25 are disposed on the inner circumferential side of the sleeve 22 .

The front bushing 23 has a cylindrical portion 23a and a bottom portion 23b. The cylindrical portion 23a is inserted into and fixed to the inner circumferential surface 22a of the sleeve 22. The bottom portion 23b is provided at an opening on the front side of the cylindrical portion 23a. The bottom portion 23b has a central hole 23b1. The rod 21b is inserted through the central hole 23b1.
The rear bushing 24 has a cylindrical portion 24a and a bottom portion 24b. The cylindrical portion 24a is inserted into and fixed to the inner circumferential surface 22a of the sleeve 22. The bottom portion 24b is provided at an opening on the rear side of the cylindrical portion 24a. The bottom portion 24b has a central hole 24b1. The rod 21b is inserted through the central hole 24b1.

The spring 25 is disposed between the front bushing 23 and the rear bushing 24. Thus, the rod 21b passes through the front bushing 23, the rear bushing 24, and the spring 25.
The rod 21b is provided with a front retainer 26a, a front snap ring 27a, a rear retainer 26b, and a rear snap ring 27b.
The front retaining ring 27a is provided on the front side of the spring 25. The front retaining ring 27a is fixed to the rod 21b. The front retaining ring 27a is fitted into a circumferential groove provided in the rod 21b. Therefore, the front retaining ring 27a can move integrally with the rod 21b in the axial direction.
The rear retaining ring 27b is provided on the rear side of the spring 25. The rear retaining ring 27b is also fixed to the rod 21b. The rear retaining ring 27b is fitted into a circumferential groove provided in the rod 21b. Therefore, the rear retaining ring 27b can move integrally with the rod 21b in the axial direction. In other words, the front retaining ring 27a and the rear retaining ring 27b are fixed to the rod 21b with a fixed distance in the axial direction.

The front retainer 26a, the rear retainer 26b, and the spring 25 are disposed between the front retaining ring 27a and the rear retaining ring 27b.
The front retainer 26a and the rear retainer 26b are annular members through which the rod 21b passes. The front retainer 26a and the rear retainer 26b hold the front end surface and the rear end surface of the spring 25.
The front retainer 26a is interposed between the front bushing 23 and the front end surface of the spring 25. The rear retainer 26b is interposed between the rear bushing 24 and the rear end surface of the spring 25.

2A shows the first grip 20 in a neutral position, which is the position when the first grip 20 is not being held by the operator or when the operator is not applying any operating force to the first grip 20.
When the first grip 20 is in the neutral position, the spring 25 biases the front retainer 26a toward the front bush 23. The spring 25 also biases the rear retainer 26b toward the rear bush 24. At this time, the front retainer 26a abuts against the cylindrical portion 23a of the front bush 23. The rear retainer 26b abuts against the cylindrical portion 24a of the rear bush 24.
In other words, when the first grip 20 is in the neutral position, the distance between the front retainer 26 a and the rear retainer 26 b is shorter than the free length of the spring 25 .

FIG. 2(b) shows a case where the first grip 20 has moved forward from the neutral position.
When the first grip 20 moves forward from the neutral position, the rod 21b also moves forward, causing the output of the potentiometer 21 to change.
When the first grip 20 and rod 21b move forward from the neutral position, the spring 25 is pressed forward by the rear retainer 26b and rear snap ring 27b. As a result, the rear retainer 26b moves away from the rear bush 24. When the first grip 20 moves further forward, the front snap ring 27a comes into contact with the bottom 23b of the front bush 23, as shown in FIG. 2B. As a result, the front snap ring 27a and the front bush 23 restrict the forward movement of the rod 21b.

FIG. 2(c) shows a case where the first grip 20 has moved rearward from the neutral position.
When the first grip 20 moves rearward from the neutral position, the rod 21b also moves rearward, causing the output of the potentiometer 21 to change.
When the first grip 20 and rod 21b move rearward from the neutral position, the spring 25 is pressed rearward by the front retainer 26a and front snap ring 27a. As a result, the front retainer 26a moves away from the front bushing 23. When the first grip 20 moves further rearward, the rear snap ring 27b comes into contact with the bottom 24b of the rear bushing 24, as shown in FIG. 2(c). As a result, the rear snap ring 27b and the rear bushing 24 restrict the rearward movement of the rod 21b.

With the above-described configuration, the first grip 20 can be elastically moved in the front-rear direction around the neutral position by the spring 25 .
The range of movement of the first grip 20 and the rod 21b in the front-rear direction is limited by the front bushing 23, the rear bushing 24, the front retaining ring 27a, and the rear retaining ring 27b.

The second operating unit 12 has the same configuration as the first operating unit 10, and includes a potentiometer 31 in addition to a second grip 30 (FIG. 2).
The second grip 30 is attached to the tip of the protrusion 2a4 on the right side of the vehicle, and is provided so as to be movable in the front-rear direction relative to the vehicle body 2a.
The potentiometer 31 is a sensor (second detection unit) for detecting the amount of displacement of the second grip 30 in the front-rear direction relative to the vehicle body 2a. The output of the potentiometer 31 is provided to the control device.

As shown in FIG. 1, the control box 6 is fixed to the frame portion on the lower right side of the seat portion 2a1.
The control box 6 houses a battery and a control device for controlling each part.

FIG. 3 is a block diagram showing an example of a configuration for controlling the operation of the motor in the electric wheelchair 1.
3, the electric wheelchair 1 includes a battery 16 and a control device 18. The battery 16 and the control device 18 are housed in the control box 6.
The battery 16 supplies power to the pair of motors 15 and each part that requires operating power.
The control device 18 has a function of controlling the drive mechanism 4 (the pair of motors 15) by giving command values to the drive mechanism 4, and controlling the speed of the vehicle body 2a.

The drive mechanism 4 including the pair of motors 15 has a pair of drive circuits 34. Each of the pair of motors 15 includes a motor body 15a and a rotation detector 15b.
The motor body 15a includes the main components of the motor, such as a rotor and a stator.
The rotation detector 15b is, for example, a Hall sensor provided on the motor body 15a. The rotation detector 15b detects the rotation state of the rotor of the motor body 15a. The rotation detector 15b is connected to the drive circuit 34 and the control device 18. The output of the rotation detector 15b is provided to the drive circuit 34 and the control device 18.

The pair of drive circuits 34 may be, for example, inverters. The pair of drive circuits 34 may be housed in the control box 6, or may be provided on the base plate 14a or the arm 14b.
The pair of drive circuits 34 are connected to the control device 18, the battery 16, and the pair of motors 15. One of the pair of drive circuits 34 is connected to the left motor 15. The other of the pair of drive circuits 34 is connected to the right motor 15. The pair of drive circuits 34 provide power from the battery 16 to the pair of motors 15.
The pair of drive circuits 34 have the function of providing drive power to the pair of motors 15 based on the speed command value given by the control device 18 and the output of the rotation detector 15b, and controlling the motors 15 so that they rotate at the speed indicated by the speed command value.

The pair of drive circuits 34 and the pair of motors 15 (motor bodies 15a) are connected by a pair of power lines 34a.
The pair of power lines 34a are provided with a pair of current detectors 36. The pair of current detectors 36 are current sensors that detect the current flowing through the pair of power lines 34a. In other words, the pair of current detectors 36 detect the current flowing through the pair of motors 15. The pair of current detectors 36 are connected to the control device 18. The outputs of the pair of current detectors 36 are provided to the control device 18.
The first operating unit 10 and the second operating unit 12 are also connected to the control device 18. As described above, the outputs of the first operating unit 10 (the potentiometer 21) and the second operating unit 12 (the potentiometer 31) are provided to the control device 18.

The control device 18 is composed of a computer or the like that includes a processing unit 38 consisting of a processor or the like, and a storage unit 40 consisting of a memory, hard disk, or the like. The storage unit 40 stores computer programs to be executed by the processing unit 38 and necessary information. The processing unit 38 realizes the various processing functions of the control device 18 by executing computer programs stored in a computer-readable, non-transitory recording medium such as the storage unit 40.

[Processing performed by the processing unit]
FIG. 4 is a diagram showing a state in which the operator operates the electric wheelchair 1. As shown in FIG.
An operator A of the electric wheelchair 1 holds the first grip 20 of the first operating unit 10 and the second grip 30 of the second operating unit 12 with both hands, and operates the electric wheelchair 1 by pushing the electric wheelchair 1 from behind.
At this time, the first grip 20 and the second grip 30 move relative to the vehicle body 2 a in the longitudinal direction. The first operating unit 10 and the second operating unit 12 provide outputs corresponding to the movements of the first grip 20 and the second grip 30 to the control device 18.
The control device 18 generates a speed command value based on the outputs from the first operating unit 10 and the second operating unit 12 and provides it to a pair of drive circuits 34 .

The output from the first operating unit 10 indicates the amount of longitudinal displacement of the first grip 20 relative to the vehicle body 2 a. The output from the second operating unit 12 indicates the amount of longitudinal displacement of the second grip 30 relative to the vehicle body 2 a.
The control device 18 determines the amount of longitudinal displacement of the first grip 20 and the amount of longitudinal displacement of the second grip 30 based on the output of the first operating unit 10 and the output of the second operating unit 12 .
The displacement amount is the distance between a reference position (e.g., a neutral position) that is set in advance within the movable range of both grips 20, 30 and the current positions of both grips 20, 30. When the reference position and the current positions coincide in the front-to-rear direction, the displacement amount is zero.
In the following description, the forward/backward displacement amount of the first grip 20 (first displacement amount) is referred to as the displacement amount x _{UI_L} , and the forward/backward displacement amount of the second grip 30 (second displacement amount) is referred to as the displacement amount x _{UI_R} .

The control device 18 discretely acquires the displacement amounts x _{UI_L} and x _{UI_R} over time and stores them in the storage unit 40, etc. The control device 18 refers to the stored displacement amounts x _{UI_L} and x _{UI_R} as needed, for example, when calculating the differential values of the displacement amounts x _{UI_L} and x _{UI_R} .

When the operator A holds and operates the first operating unit 10 and the second operating unit 12, the control device 18 controls the drive mechanism 4 so that the movement of the vehicle body 2a with respect to the displacement amount x _{UI_L} and the displacement amount x _{UI_R} is a movement that simulates the mechanical impedance characteristics.
That is, the control device 18 controls the drive mechanism 4 so that the distance H between the first grip 20 (second grip 30) and the vehicle body 2a is constant, while reproducing a movement in which the first grip 20 (second grip 30) and the vehicle body 2a are connected by a virtual spring 42 and a virtual damper 44, as shown in Figure 4.

Control of the drive mechanism 4 so that the distance H between the first grip 20 (second grip 30) and the vehicle body 2a is constant includes control so that the displacement amount x _{UI_L} and the displacement amount x _{UI_R} are maintained at 0 or at a predetermined set value.
As a result, when the operator A moves forward and presses the first grip 20 and the second grip 30 forward, the control device 18 controls the drive mechanism 4 to move the vehicle body 2a forward in accordance with the displacement amounts x _{UI_L} and x _{UI_R} by which the first grip 20 and the second grip 30 move when pressed forward.

FIG. 5 is a block diagram showing an example of the processing contents executed by the processing unit 38 of the control device 18.
The processing unit 38 has the function of executing a generation process 51 and an external force calculation process 50 .
The generation process 51 is a process for generating a speed command value based on the external force acting on the vehicle main body 2a, and the displacement amounts x _{UI_L} and x _{UI_R} .
The external force calculation process 50 is a process for determining an external force acting on the vehicle main body 2 a to be used in the generation process 51 .
The generation process 51 includes a thrust force calculation process 52 , a command value generation process 54 , a turning speed calculation process 56 , and a turning force calculation process 58 .
The processing unit 38 starts the process of controlling the speed of the vehicle body 2a, thereby executing the generation process 51 and the external force calculation process 50 as needed.

The outputs of the first operating unit 10 and the second operating unit 12 are used in the thrust calculation process 52 and the turning speed calculation process 56 .
The outputs of the pair of rotation detectors 15 b are used in the thrust force calculation process 52 and the turning force calculation process 58 .
The outputs of the pair of current detection units 36 are used in the external force calculation process 50 .

[External force calculation processing]
The external force calculation process 50 is a process for determining the external force acting on the vehicle body 2a.
The operator A grips the first operating unit 10 and the second operating unit 12 and operates the electric wheelchair 1 by pushing the electric wheelchair 1 from behind.
At this time, apart from the displacement of both grips 20, 30, an external force due to the operation of operator A acts on the vehicle body 2a via the first operating unit 10 and the second operating unit 12.
The processing unit 38 executes an external force calculation process 50 to determine the external force acting on the vehicle main body 2a.

Fig. 6 is a plan view of the electric wheelchair 1. Note that Fig. 6 shows only the main parts of the electric wheelchair 1 in a schematic manner.
6, point P is a point on the rotation axis C1 of the pair of drive wheels 14c, and is the midpoint between the pair of drive wheels 14c. In the following description, the direction around the central axis that passes through point P and extends in the vertical direction is referred to as the turning direction.
The control device 18 determines the external force acting on the vehicle body 2a by dividing it into an external force in the front-rear direction and an external force in the turning direction.

When operator A attempts to rotate the vehicle body 2a in a predetermined direction using both operating units 10, 12 while the speed of the electric wheelchair 1 is being controlled, the pair of drive circuits 34 controls the pair of motors 15 to generate torque to rotate the vehicle body 2a in the opposite direction to the predetermined direction, in order to maintain the operating state based on the speed command value. Therefore, the current value flowing through the pair of motors 15 represents the external force acting on the vehicle body 2a via the two operating units 10, 12 (external force due to operator A's operation).

For example, as shown in Figure 6, we will explain the case where operator A, for a stopped electric wheelchair 1, attempts to rotate the vehicle body 2a counterclockwise around the central axis passing through point P by pulling the first operating unit 10 backward and pushing the second operating unit 12 forward.
In this case, it is assumed that a speed command value of 0 is given to the pair of drive circuits 34 .

When the vehicle body 2a is turned by the operation of the operator A, the drive wheel 14c on the left side of the vehicle moves backward, and the drive wheel 14c on the right side of the vehicle moves forward.
At this time, the drive circuit 34 that controls the drive wheel 14c on the left side of the vehicle controls the motor 15 on the left side of the vehicle so as to generate torque that moves the drive wheel 14c on the left side of the vehicle forward.
Further, the drive circuit 34 that controls the drive wheel 14c on the right side of the vehicle controls the motor 15 on the right side of the vehicle so as to generate torque that moves the drive wheel 14c on the right side of the vehicle backward.

At this time, the current flowing through the pair of motors 15 is supplied in accordance with the turning operation of the vehicle body 2a. Therefore, the current flowing through the pair of motors 15 represents the external force acting on the vehicle body 2a via both operation units 10, 12. In the above example, the electric wheelchair 1 is described as being stopped, but the same applies to the electric wheelchair 1 as it travels while being speed-controlled.
Therefore, the processing unit 38 calculates the external force acting on the vehicle main body 2a based on the following equation (1).

In equation (1), F _op is the external force in the longitudinal direction, τ _op is the external force in the turning direction, r is the radius of the drive wheels 14 c, W is the distance between the pair of drive wheels 14 c (see FIG. 6 ), K _t is the torque constant of the motor 15 (motor generated torque per unit current), I _R is the current value obtained from the output of the current detection unit 36 on the right side of the vehicle, and I _L is the current value obtained from the output of the current detection unit 36 on the left side of the vehicle.
r, W, and _Kt are constants that are stored in advance in the storage unit 40 .
In equation (1), the external force F _op in the longitudinal direction is calculated based on the sum of the torques generated by the pair of motors 15, and the external force τ _op in the turning direction is calculated based on the difference between the torques generated by the pair of motors 15.

In the external force calculation process 50, the processing unit 38 calculates the external force F _OP in the forward/backward direction and the external force τ _OP in the turning direction based on the current values _IR and _IL that indicate the currents flowing through the pair of motors 15, as shown in the above formula (1).
In this way, in the external force calculation process 50, the external force acting on the vehicle body 2a is determined separately as an external force F _OP in the longitudinal direction and an external force τ _OP in the turning direction.

[Thrust force calculation processing]
The thrust calculation process 52 is a process for calculating a target thrust _Fth , which is a target value of the thrust in the longitudinal direction.
In the thrust calculation process 52, the processing unit 38 calculates the target thrust _Fth based on the following equation (2).

Equation (2) represents the Laplace transformed target thrust force F _th .
In equation (2), K is a virtual spring coefficient, D is a virtual damper coefficient, μ is a friction coefficient, M is a virtual mass of the electric wheelchair 1, v is the traveling speed of the electric wheelchair 1, α is a coefficient, s is a Laplace operator, and ω1 and ω2 are predetermined cutoff frequencies.

As shown in equation (2), the thrust calculation process 52 determines the target thrust _Fth using the displacement _{xUI_R} , displacement _{xUI_L} , the traveling speed v of the electric wheelchair 1, and the external force _Fop in the front-rear direction.
The first term in equation (2) shown below represents a model for realizing mechanical impedance characteristics.

The spring coefficient K in the first term is multiplied by the total displacement _xT of the displacements _{xUI_R} and _{xUI_L} . The product of the spring coefficient K and the total displacement _xT represents an elastic term based on the displacement. The spring coefficient K is the spring constant of the virtual spring 42 (FIG. 4) and is a preset constant.
The damper coefficient D in the first term is multiplied by a Laplace operator and the total displacement _xT . The product of the total displacement _xT and the Laplace operator represents the differential value of the displacement. Therefore, the product of the damper coefficient D, the Laplace operator, and the total displacement _xT represents a viscosity term based on the differential value of the displacement. The damper coefficient D is a coefficient indicating the viscosity of the virtual damper 44 (FIG. 4) and is a preset constant.
Thus, the first term includes an elastic term based on the displacement amount and a viscous term based on the differential value of the displacement amount.

In the first term, ω ₁ /(s+ω ₁ ) multiplied by the damper coefficient D is a low-pass filter with a cutoff frequency of ω _1. By multiplying the viscosity term by this low-pass filter, relatively high-frequency noise contained in the total displacement _xT is suppressed.

Furthermore, the above first term uses the total displacement _xT , which is the sum of the displacements _{xUI_R} and _{xUI_L} of both grips 20, 30. This is because, in addition to conforming to the calculation method for the external force FOP in the front-to-rear direction, even if a slight difference occurs between the displacements _{xUI_R} and _{xUI_L} , this difference can be absorbed and the target thrust force _Fth in the front-to-rear direction (the calculation result required to calculate the target thrust force _Fth ) can be appropriately calculated.

The second term in equation (2) shown below represents the deceleration force in the longitudinal direction of the vehicle body 2a.

The friction coefficient μ in the second term is a value for virtually setting the friction coefficient acting on the vehicle body 2a, and is a preset constant. The traveling speed v of the electric wheelchair 1 is determined based on the output of the pair of rotation detectors 15b. In other words, the pair of rotation detectors 15b constitute an acquisition unit that acquires speed information indicating the traveling speed of the vehicle body 2a.

The product of the friction coefficient μ and the traveling speed v indicates the friction force according to the speed of the electric wheelchair 1 .
The virtual mass M of the electric wheelchair 1 is an assumed value of the total mass of the electric wheelchair 1 and the occupant, and is a preset constant. The virtual mass M is multiplied by a Laplace operator and the traveling speed v. The product of the traveling speed v and the Laplace operator represents the differential value of the traveling speed v (the acceleration of the electric wheelchair 1). Therefore, the product of the virtual mass M, the Laplace operator, and the traveling speed v represents the deceleration force corresponding to the acceleration of the electric wheelchair 1.

The second term determines the friction force according to the speed of the electric wheelchair 1 and the deceleration force according to the acceleration of the electric wheelchair 1. The sum of these is the deceleration force in the front-rear direction of the vehicle body 2a.
The deceleration force in the longitudinal direction of the vehicle body 2a obtained in the second term is added to the calculation result of the first term.

In the second term, ω ₂ /(s+ω ₂ ) multiplied by the virtual mass M is a low-pass filter with a cutoff frequency of ω _2. This low-pass filter suppresses relatively high-frequency noise contained in the traveling speed v.

The third term in equation (2) shown below is a term for correcting for movement in the forward and backward directions.
Term 3: -αF _OP

The coefficient α in the third term is a variable that changes depending on the total displacement _xT .
αF _OP is a value that changes depending on the external force in the front-rear direction and the total displacement amount _xT , and is appropriately adjusted in accordance with the external force in the front-rear direction and the total displacement amount _xT .
An upper limit and a lower limit are set for αF _OP , which makes it possible to prevent the vehicle from decelerating or accelerating more than necessary.

The processing unit 38 calculates the target thrust _Fth based on the calculation result of the first term and the calculation results of the second and third terms.

[Turning speed calculation processing]
The turning speed calculation process 56 is a process for determining a target turning speed ω _yaw , which is a target value of the speed (turning speed) of the vehicle main body 2a in the turning direction.
In the turning speed calculation process 56, the processing unit 38 calculates the target turning speed ω _yaw based on the following equations (3) and (4).

In equation (3), C _comp is a gain for compliance control, I _comp is a virtual inertia coefficient, and D _comp is a virtual damper coefficient. The gain C _comp and the inertia coefficient I _comp are constants that are set in advance.
The damper coefficient D _comp is a variable that changes depending on the displacement amount x _{UI_R} and the displacement amount x _{UI_L} . The damper coefficient D _comp is expressed by the following equation (5).

In equation (5), D _const and β are preset constants.
As shown in the formula (5), the damper coefficient _Dcomp changes depending on the difference between the displacement amount _{xUI_R} and the displacement amount _{xUI_L} . More specifically, the damper coefficient _Dcomp is set to decrease as the difference between the displacement amount _{xUI_R} and the displacement amount _{xUI_L} increases.
Furthermore, an upper limit and a lower limit are set for the damper coefficient D _comp . When the damper coefficient D _comp exceeds the upper limit, it is set to the upper limit regardless of the difference between the displacement amounts x _{UI_R} and x _{UI_L} . When the damper coefficient D _comp falls below the lower limit, it is set to the lower limit regardless of the difference between the displacement amounts x UI_R and _{x UI_L} . This provides a dead zone for the damper coefficient D _comp with respect to the difference between the displacement amounts x _{UI_R} and x _{UI_L} .

The term in parentheses in the above equation (3) represents the difference between the external force τ _OP in the current turning direction and the external force based on the target turning speed and target turning acceleration. Among the terms in parentheses in equation (3), the product of I _comp and the target turning acceleration is an inertia term, and the product of the damper coefficient D _comp and the target turning speed is a viscosity term. Thus, the above equation (3) includes an inertia term and an elastic term.
Therefore, the processing unit 38 is configured to obtain the target rotation speed ω _yaw while reproducing the virtual inertia and the virtual damper. That is, the processing unit 38 obtains the target rotation speed ω _yaw by compliance control.

[Turning force calculation processing]
The turning force calculation process 58 is a process for determining a target turning force τ _yaw , which is a target value of the turning force in the turning direction of the vehicle main body 2a, based on the target turning speed ω _yaw and the outputs of the pair of rotation detectors 15b.
In the turning force calculation process 58, the processing unit 38 calculates the target turning force τ _yaw based on the following equation (6).

In equation (6), P _yaw is the proportional gain, D _yaw is the differential gain, v _R is the rotational speed (circumferential speed) of the right drive wheel 14c, v _L is the rotational speed (circumferential speed) of the left drive wheel 14c, and ω ₃ is a predetermined cutoff frequency.
The proportional gain P _yaw and the derivative gain D _yaw are preset constants.
The rotation speeds v _R and v _L are determined from the outputs of the pair of rotation detectors 15b.
In equation (6), (v _R - v _L )/W represents the yaw rate (current turning speed) of the vehicle body 2a. Therefore, ω _yaw - ((v _R - v _L )/W) represents the difference between the target turning speed ω _yaw and the current turning speed.
Equation (6) shows that the target turning force τ _yaw can be obtained by PD control.

The processing unit 38 calculates the target turning force τ _yaw based on the target turning speed ω _yaw calculated in the turning speed calculation process 56 and the rotational speeds v _R and v _L , as shown in equation (6).
In other words, the processing unit 38 determines the target turning force τ _yaw based on the external force acting on the vehicle main body 2a and the outputs of the pair of rotation detectors 15b.

Note that ω ₃ /(s + ω ₃ ) multiplied by the differential gain D _yaw is a low-pass filter with a cutoff frequency of ω _3. This low-pass filter suppresses relatively high frequency noise contained in the difference between the target rotation speed ω _yaw and the current rotation speed.

[Command value generation process]
The command value generation process 54 is a process for generating speed command values to be given to the pair of drive circuits 34 based on the target thrust force F _th and the target turning force τ _yaw .
In the command value generation process 54, the processing unit 38 calculates the output target forces of the left and right drive wheels 14c based on the following equation (7).

In equation (7), F _R represents the target output force of the right drive wheel 14 c, and F _L represents the target output force of the left drive wheel 14 c.
As shown in equation (7), the processing unit 38 calculates the output target forces F R and F L of the pair of drive wheels 14 _c based on the target thrust force F _th calculated in the thrust force calculation process 52 and the target turning force _{τ yaw} calculated in the turning force calculation process 58.

After determining the forces F _R and F _L that are the output targets of the drive wheels 14c, the processing unit 38 further determines a speed command value based on the following equation (8).

In equation (8), v _CR represents a speed command value given to the right drive circuit 34, and v _CL represents a speed command value given to the left drive circuit 34.

The processing unit 38 supplies the determined speed command values v _CR and v _CL to the pair of drive circuits 34 .
The speed command values v _CR and v _CL indicate the peripheral speeds of the pair of drive wheels 14 c. Therefore, the processing unit 38 converts the speed command values v _CR and v _CL into rotation speeds per unit time and provides them to the pair of drive circuits 34 .
The pair of drive circuits 34 to which the speed command values v _CR and v _CL are given drive control of the pair of motors 15 in accordance with the speed command values v _CR and v _CL .

As described above, the processing unit 38 of the control device 18 of this embodiment executes a generation process 51 that generates the speed command values v _CR and v _CL using a model (the first term in equation (1)) that includes an elastic term based on the displacement amounts of both operation units 10 and 12 and a viscosity term based on the differential value of the displacement amounts of both operation units 10 and 12.
According to this configuration, the target propulsive force _Fth is calculated using a model including an elastic term and a viscous term, and the speed command values _vCR and _vCL are generated, so that the drive mechanism 4 can be controlled so that the movement of the vehicle body 2a in response to the displacement of both operation units 10, 12 simulates the mechanical impedance characteristics. As a result, when the speed of the vehicle body 2a is controlled so that the distance between the operator A and the vehicle body 2a is constant, it is possible to prevent the operator A from walking at the same speed as the vehicle body 2a, and good operability can be obtained.

Furthermore, in the propulsive force calculation process 52, the target propulsive force Fth is calculated based on the calculation results of the above model and the longitudinal deceleration force (the second term in equation (1)) obtained based on the traveling speed of the vehicle main body 2a. Therefore, the target propulsive force _Fth can be calculated while taking into account deceleration based on frictional forces etc. that occur in accordance with the speed of the vehicle main body 2a, or while limiting the traveling speed of the vehicle main body _2a .

Furthermore, in the external force calculation process 50, the external force acting on the vehicle body 2a via both operation units 10, 12 is determined based on the outputs of the pair of current detection units 36.
In the generation process 51, a speed command value is generated based on the calculation results of the above model and the external force determined in the external force calculation process 50.
Therefore, the speed of the vehicle body 2a can be controlled based on the amount of displacement of both operation units 10, 12 and the external force acting on the vehicle body 2a.

The generation process 51 also includes a thrust force calculation process 52 that calculates the target thrust F _th , a turning force calculation process 58 that calculates the target turning force τ _yaw , and a command value generation process 54 that generates speed command values v _{CR and} v _CL for the pair of motors 15, respectively, based on the target thrust F _th and the target turning force τ _yaw .
This allows the target force for moving the vehicle body 2a to be determined separately as a propulsive force in the longitudinal direction and a turning force in the turning direction, thereby enabling the speed of each of the pair of motors 15 to be suitably controlled.

Furthermore, an external force calculation process 50 calculates an external force F _OP in the longitudinal direction and an external force τ _OP in the turning direction. A thrust calculation process 52 calculates a target thrust force F _th based on the calculation results using the above model and the external force F _OP in the longitudinal direction. A turning force calculation process 58 calculates a target turning force τ _yaw based on the external force τ _OP in the turning direction and the outputs of the pair of rotation detectors 15b.
In this way, by dividing the external force acting on the vehicle main body 2a into an external force F _OP in the longitudinal direction and an external force τ _OP in the turning direction, the target propulsive force and the target turning force can be calculated with higher accuracy.

In this embodiment, the turning speed calculation process 56 determines the target turning speed based on the external force acting on the vehicle main body 2a and the difference between the displacement x _{UI_R} and the displacement x _{UI_L} .
Furthermore, in the turning force calculation process 58, the target turning force τ _yaw is calculated based on the target turning speed and the outputs of the pair of rotation detectors 15b.
In this embodiment, an upper limit and a lower limit are set for the damper coefficient _Dcomp , which is a value determined by the difference between the displacement amounts _{xUI_R} and _{xUI_L} . Therefore, a dead zone for the damper coefficient _Dcomp is set for the difference between the displacement amounts _{xUI_R} and _{xUI_L} . This imposes a restriction on the movement in the turning direction based on the difference between the displacement amounts _{xUI_R} and _{xUI_L} , making it possible to prevent the operator A from making an unintended movement.

〔others〕
The embodiments disclosed herein are illustrative in all respects and are not restrictive.
For example, in the above embodiment, the vehicle main body 2a is provided with the first operating unit 10 and the second operating unit 12, but it is sufficient that at least one of the operating units is provided.

Furthermore, in the above embodiment, the processing unit 38 generates a speed command value and provides the speed command value to the pair of drive circuits 34 to drive and control the pair of motors 15, but the processing unit 38 may also be configured to generate a current command value indicating the current value to be provided to the motor 15 and provide the current command value to the pair of drive circuits 34 to drive and control the pair of motors 15.
In the above embodiment, the motor 15 is an in-wheel motor provided inside the drive wheel 14 c, but the motor 15 may be provided outside the drive wheel 14 c. In this case, the motor 15 drives the drive wheel 14 c from outside.

In addition, while the above embodiment illustrates the case of an electric wheelchair 1, the present invention can also be applied to electric vehicles other than wheelchairs, such as carts and wagons, which are equipped with electric drive mechanisms.

The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the claims.

DESCRIPTION OF SYMBOLS 1 Electric wheelchair 2 Wheelchair section 2a Vehicle body 2a1 Seat section 2a2 Backrest section 2a3 Support pipe 2a4 Protrusion section 2b Main wheel 2c Caster 4 Drive mechanism 6 Control box 10 First operation section 12 Second operation section 14 Drive unit 14a Base plate 14b Arm 14c Drive wheel 15 Motor 15a Motor body 15b Rotation detector 16 Battery 18 Control device 20 First grip 20a Cylindrical section 20b Bottom section 21 Potentiometer 21a Body section 21b Rod 21b1 Tip section 22 Sleeve 22a Inner peripheral surface 23 Front bush 23a Cylindrical section 23b Bottom section 23b1 Center hole 24 Rear bush 24a Cylindrical section 24b Bottom section 24b1 Center hole 25 Spring 26a Front retainer 26b Rear retainer 27a Front retaining ring 27b Rear retaining ring 30 Second grip 31 Potentiometer 34 Drive circuit 34a Power line 36 Current detection unit 38 Processing unit 40 Memory unit 42 Spring 44 Damper 50 External force calculation processing 52 Propulsion force calculation processing 54 Command value generation processing 56 Swing speed calculation processing 58 Swing force calculation processing A Operator C1 Rotation axis

Claims (7)

The vehicle body,
a drive mechanism for driving the vehicle body;
a control device that controls the drive mechanism by providing a command value to the drive mechanism;
a first operating unit including a first grip that is held by an operator and that receives an operation of pushing the vehicle body by the operator and that is movable in a front-rear direction of the vehicle body, and a first detection unit that detects a first displacement amount of the first grip in the front-rear direction relative to the vehicle body;
an acquisition unit that acquires speed information indicating a traveling speed of the vehicle body;
Equipped with
The control device
a processing unit that executes a generation process of generating the command value using a model including an elastic term based on the first displacement amount and a viscosity term based on a differential value of the first displacement amount,
The generation process includes:
a thrust calculation process for calculating a target thrust, which is a target value of the thrust in the longitudinal direction, using the model;
a command value generation process for generating the command value based on the target thrust,
In the propulsive force calculation process, the target propulsive force is calculated based on the calculation result of the model and the deceleration force in the longitudinal direction obtained based on the speed information. The drive mechanism includes:
A pair of left and right drive wheels;
a pair of motors that drive the pair of drive wheels;
The electric vehicle according to claim 1 , further comprising: a pair of drive circuits that drive a pair of motors based on the command value. The vehicle body,
a drive mechanism for driving the vehicle body;
a control device that controls the drive mechanism by providing a command value to the drive mechanism;
a first operating unit including a first grip that is held by an operator and that receives an operation of pushing the vehicle body by the operator and that is movable in a front-rear direction of the vehicle body, and a first detection unit that detects a first displacement amount of the first grip in the front-rear direction relative to the vehicle body;
Equipped with
The control device
a processing unit that executes a generation process of generating the command value using a model including an elastic term based on the first displacement amount and a viscosity term based on a differential value of the first displacement amount,
The drive mechanism includes:
A pair of left and right drive wheels;
a pair of motors that drive the pair of drive wheels;
a pair of drive circuits that drive a pair of motors based on the command values;
further comprising a pair of current detection units for detecting currents flowing through the pair of motors;
The processing unit
executes an external force calculation process to determine an external force acting on the vehicle body based on the pair of current values detected by the pair of current detection units;
In the generation process, the command value is generated based on the calculation result of the model and the external force. a pair of rotation detectors for detecting the rotation speeds of the pair of motors;
The generation process includes:
a thrust calculation process for calculating a target thrust, which is a target value of the thrust in the longitudinal direction, using the model;
a turning force calculation process for calculating a target turning force, which is a target value of the turning force in the turning direction of the vehicle body, based on the external force and the outputs of the pair of rotation detectors;
The electric vehicle according to claim 3 , further comprising a command value generation process for generating a pair of the command values for the pair of motors, based on the target propulsive force and the target turning force. the external force includes an external force in the front-rear direction and an external force in the turning direction,
In the thrust calculation process, the target thrust is calculated based on a calculation result of the model and the external force in the longitudinal direction;
The electric vehicle according to claim 4 , wherein the turning force calculation process determines the target turning force based on an external force in the turning direction and outputs from the pair of rotation detectors. a second operating unit including a second grip movable in the front-rear direction and a second detection unit configured to detect a second displacement amount of the second grip relative to the vehicle body in the front-rear direction;
the first operating unit is provided on the left side of the vehicle body,
The second operation unit is provided on the right side of the vehicle body,
the generation process includes a turning speed calculation process of calculating a target turning speed that is a target value of the turning speed in the turning direction based on the external force and a difference between the first displacement amount and the second displacement amount,
The electric vehicle according to claim 5, wherein the turning force calculation process determines the target turning force based on the target turning speed and outputs from the pair of rotation detectors. Further including a wheelchair portion;
The electric vehicle according to any one of claims 1 to 6, wherein the vehicle body is the vehicle body of the wheelchair section.