JP5507180B2 - Electric wheelchair - Google Patents

Description

  The present invention relates to a control device for an electric wheelchair, and more particularly to a control device that controls the rotational position of a drive caster provided in the electric wheelchair.

  In recent years, an aging society has further progressed, and electric wheelchairs have begun to be used not only on roads and hospitals but also in general residences. Since the moving space is small in a general residence, it is difficult to turn with a large turning radius, and an operation for rotating the electric wheelchair itself is required on the spot. Moreover, the electric wheelchair utilized in a general residence is required to move not only in the front-rear direction but also in the left-right direction, for example, in housework in the kitchen. Therefore, as shown in Patent Documents 1 to 3, there has been proposed an electric wheelchair that can move in all directions by expanding the degree of freedom of movement.

  The electric wheelchair shown above has a base member on which a chair is attached upward, and a drive caster attached to the base member. In this drive caster, a support shaft on which a wheel is supported is rotatably attached to a base member, and the drive direction of the wheel can be directed in a desired movement direction. And the drive direction of a wheel is turned by the control apparatus of an electric wheelchair in the moving direction instruct | indicated by the passenger with a joystick, and an electric wheelchair moves to the direction which a passenger intends by rotating a wheel in that direction.

JP 2008-136837 A JP 2008-212272 A JP 2008-213570 A

  In the electric wheelchair as described above, for example, when the electric wheelchair is moved to the left and right alternately, the driving direction of the wheels of the driving caster must be greatly rotated left and right in the moving direction. I must. Thus, when rotating the drive direction of a wheel largely, the drive direction of a wheel cannot be changed in a short time, and the responsiveness in the change of the moving direction of an electric wheelchair cannot be improved.

  Therefore, the present invention has been made in view of the above-described circumstances, and provides a control device capable of enhancing the responsiveness in changing the moving direction of an electric wheelchair in a control device for an electric wheelchair provided with a drive caster. .

In order to solve the above problems, an electric vehicle chair terminal of the present invention, a chair, a base member chair provided above, rotatably mounted on said base member having a wheel driven to rotate by the electric motor comprising a drive casters can be rotated in a direction for the purpose of driving direction of the wheel, and the dynamic direction detecting means drive, transfer and dynamic direction indicating means, the control device for supplying a control current to the electric motor, prior Symbol In the electric wheelchair that moves by rotating the wheel , the movement direction instruction means detects a target movement direction of the wheel with reference to a predetermined operation axis direction of the movement direction instruction means and supplies a first signal to the control device. and said drive direction detecting means supplies a second signal to detect the drive direction based on the operation axis to the control device, the control device supplies a control current to the electric motor And force means, based on said first signal and second signal, if the magnitude of the difference angle is the difference between the target movement direction and the driving direction is smaller than the predetermined angle, the difference angle The output means is instructed to rotate the drive caster by the rotation angle, and the direction of rotational drive of the wheels is made the same as before the first signal is supplied to the output means. And when the magnitude of the difference angle is greater than or equal to a predetermined angle based on the first signal and the second signal , an angle obtained by adding or subtracting approximately 180 ° to the difference angle is set as the rotation angle, The output means is instructed to rotate the drive caster by the rotation angle, and the output means is instructed to reverse the direction of rotational driving of the wheel before the first signal is supplied. Caster operation command means, and the drive caster is capable of directing the driving direction of the wheel in a desired direction by a control current from the output means . And the said predetermined angle is 80 degrees or more and 100 degrees or less, It is characterized by the above-mentioned.

  According to the present invention, when the difference angle, which is the difference in the target movement direction with respect to the drive direction of the drive caster, is 80 ° to 100 ° or more, that is, the difference in the target movement direction with respect to the drive direction is approximately 90 ° or more. In this case, an angle obtained by adding or subtracting about 180 ° from the difference angle is set as the rotation angle. When the difference angle is approximately 90 ° or more, a rotation angle that is an angle obtained by adding or subtracting approximately 180 ° from the difference angle is approximately 90 ° or less. Therefore, the direction of the wheel can be quickly changed by rotating the direction of the wheel by this rotation angle.

  The rotation angle is an angle obtained by adding or subtracting about 180 ° from the difference angle. When the direction of the wheel is rotated by this rotation angle, the direction of the wheel is directed in the same direction as when the rotation is performed by the difference angle. It is done. And the direction of the rotational drive of the wheel is reversed, and the drive direction of the wheel can be directed to the moving direction intended by the passenger by rotating the wheel in this direction.

It is a front view of the electric wheelchair in embodiment of this invention. It is a bottom view of the electric wheelchair in the embodiment of the present invention. It is a partial cross section figure of the drive caster in an embodiment of the invention. It is a block diagram of the control apparatus of the electric wheelchair in embodiment of this invention. It is a figure explaining the rotation angle of the drive caster in embodiment of this invention. It is a figure explaining the rotation angle of the drive caster in embodiment of this invention. It is a flowchart which shows the process of the information in the caster operation command means in embodiment of this invention. It is a figure explaining operation of a joystick and rotation of a drive caster. It is a figure explaining operation of a joystick and rotation of a drive caster. It is a figure explaining rotation of the drive caster to a stop position. It is a figure explaining the stop position of a drive caster.

  Next, an electric wheelchair using a drive caster according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view of an electric wheelchair, FIG. 2 is a bottom view of the electric wheelchair, and FIG. 3 is a partial cross-sectional view of a differential caster.

As shown in FIGS. 1 to 3, the electric wheelchair 1 includes a base member 2 made of a metal plate and first to third drive casters (3, 4, 5) attached to the base plate 2 downward. A battery 9 and a control device 10 installed in a housing portion 2a provided in the base member 2, a leg member (6, 6) standing above the base member 2, and a leg member (6) , 6) and a chair 7 attached by a seat 7a. A backrest 7b is integrally provided from the seat portion 7a of the chair 7, and armrests (7c, 7d) are integrally provided on both sides of the backrest 7b. One armrest 7c is attached with a joystick 8 as a moving direction instruction means. Here, the reference posture direction of the electric wheelchair 1 is determined by a predetermined operation axis direction of the joystick 8. In the present embodiment, the predetermined operation axis direction is set to the y-axis direction of the joystick 8, and this y-axis direction is defined as the reference posture direction of the electric wheelchair 1 (see FIG. 8).

  As shown in FIG. 2, in the base member 2, the first drive caster 3 is disposed at the rear center, the second drive caster 4 is disposed at the front left side, and the third differential caster 5 is disposed at the front right side. The first to third drive casters (3, 4, 5) are arranged at positions where a triangle is formed on the base member 2.

  Next, the first drive caster 3 provided in the electric wheelchair 1 will be described with reference to FIG. The structure of the second and third drive casters (4, 5) is the same as the structure of the first drive caster 3, and only the first drive caster 3 will be described. The second and third drive casters (4, 4) About each component of 5), the code | symbol same as the component of the 1st drive caster 3 is attached | subjected, and the description is abbreviate | omitted.

  The first drive caster 3 is disposed on the base member 2 from below, a mounting member 51, a bearing (57, 57) disposed on the inner periphery 51a of the mounting member 51, and an inner side of the bearing (57, 57). A slip ring folder 52 rotatably supported with respect to the attachment member 51, and a support shaft 53 attached to the slip ring folder 52 and rotatably supported with respect to the attachment member 51 via the slip ring folder 52. A connecting rod 54 that is tiltably attached to one end 53a of the support shaft 53 by a connecting pin 55, a pair of motors (60, 60) with a speed reducer attached to both ends of the connecting rod 54, and a speed reduction And a pair of wheels (91, 92) respectively linked to the output shafts (86, 86) of the motors with machines (60, 60).

  Further, the first drive caster 3 includes a slip ring 59 provided in the slip ring folder 52, a rotation detection device 100, and a cover body C that encloses the slip ring 59 and the rotation detection device 100. A feed line L1 for supplying a control current from the control device 10 is connected to the input part 59a of the slip ring 59, and the output part 59b of the slip ring 59 is controlled via the slip link 59 to the motor 60 with a speed reducer. A supply line L2 for supplying current is connected. Thus, by arranging the supply line (L1, L2) via the slip ring 59, the first drive caster 3 rotates with respect to the base member 2, and the supply line (L1, L2) is twisted. There is nothing.

The rotation detection device 100 includes a ring gear 101 that is integrally attached to the outer periphery of the slip ring folder 52, a pinion gear 102 that meshes with the ring gear 101, and a driving direction detection unit that is attached to the attachment member 51 and to which the pinion gear 102 is attached. As an encoder 103. The slip ring folder 52 rotates together with the support shaft 53 with respect to the attachment member 51 attached to the base plate 2, and the ring gear 101 attached to the slip ring folder 52 rotates in the same manner as the support shaft 53 rotates with respect to the base plate 2. I do. By detecting the rotation of the ring gear 101 by the encoder 103 via the pinion gear 102, the rotation position of the support shaft 53 indicating the rotation position that is the driving direction of the wheel 90 of the first drive caster 3 is detected by the encoder 103. The Here, the driving direction of the wheel 90 is obtained based on the y-axis direction of the joystick 8 (see FIG. 8).

  The motor 60 with a speed reducer includes an electric motor 70 and a speed reducer 80. The electric motor 70 includes a motor housing 73 and a rotor 71 that is rotatably disposed in the motor housing 73 and has a motor shaft 72. The motor housing 73 is attached to the motor flange 56 attached to the end of the connecting rod 54, whereby the electric motor 70 is tiltably linked to the support shaft 54 via the connecting rod 54. The speed reducer 80 is connected to the motor shaft 72 of the electric motor 70.

A pair of wheels (91, 92) are linked to the output shafts (86, 86) of the pair of motors with speed reducers (60, 60). The wheel 90 is integrally attached to the outer periphery of the first wheel 93 by a screw 95 attached to the output shaft 86 and covers the elastic ring body 96 and the opening of the first wheel 93. And a second wheel 94. The first wheel 93 is rotatably supported by bearings (58, 58) mounted on the outer periphery of the motor flange 56, whereby the wheel 90 is rotatable together with the output shaft 86 of the motor 60 with speed reducer. It has a configuration.

  Next, the control device 10 for the electric wheelchair 1 in the embodiment of the present invention will be described with reference to FIGS. The control device 10 includes an angle reading unit 11, an operation amount reading unit 12, a target angle calculation unit 13, a difference angle calculation unit 14, a memory 15, a caster operation command unit 16, a timer 17, an operation state determination unit 18, and a stop position command unit. 19, selection means 20, comparison means 21, and output means 22.

The angle reading means 11 is supplied with a signal (second signal) from an encoder (103, 103, 103) that detects the driving direction of the wheels (91, 92). Is determined. The operation amount reading means 12 is supplied with an xy signal (first signal) from a joystick (movement direction instructing means) 8 operated in the direction in which the passenger wants to move, and the operation amount reading means 12 reads this xy signal. Then, the target angle calculation means 13 obtains the direction of the vector synthesized from this xy signal, and sets this vector direction as the target movement direction φ. Here, the target movement direction is obtained based on the y-axis direction of the joystick 8 (see FIG. 8).

  The difference angle calculation means 14 is supplied with a signal corresponding to the driving direction θ from the angle reading means 11 and a signal corresponding to the target movement direction φ from the operation amount reading means 12. In the difference angle calculation means 14, the processing method differs depending on whether the value corresponding to the target moving direction φ is “large” or “small” with respect to the value corresponding to the driving direction θ, and FIG. 5 corresponds to the driving direction θ. FIG. 6 shows processing when the value corresponding to the target movement direction φ is “small” with respect to the value corresponding to the driving direction θ. Indicates.

  As shown in FIG. 5, when the value corresponding to the target moving direction φ is “large” with respect to the value corresponding to the driving direction θ, the difference angle ε, which is the difference between the target moving direction φ and the driving direction θ, is Processed as a “positive” value (ε> 0). As shown in FIG. 6, when the value corresponding to the target moving direction φ is “small” with respect to the value corresponding to the driving direction θ, the difference angle ε, which is the difference between the target moving direction φ and the driving direction θ, is Treated as a “negative” value (ε <0).

  In the memory 15, as reference difference angles, “+ 0 °”, “+ 90 °”, “+ 180 °”, “+ 270 °”, “+ 360 °”, “−0 °”, “−90 °”, “−180”. Data corresponding to “°”, “−270 °”, and “−360 °” are stored.

  Next, the operation | movement of the caster operation command means 16 is demonstrated based on FIG.5, FIG.6 and FIG.7. Here, FIG. 7 is a flowchart showing information processing in the caster operation command means 16. The caster operation command means 16 is supplied with a signal corresponding to the difference angle ε from the difference angle calculation means 14, compares the signal corresponding to the difference angle ε with the data stored in the memory 15, and rotates the rotation angle ξ. And the direction of rotational driving of the wheels 90 is determined. The rotation angle ξ refers to an angle at which the direction of the wheel currently directed in the moving direction of the electric wheelchair 1 is directed toward the target moving direction.

  First, the case where the difference angle ε is “positive” will be described with reference to FIGS. 5 and 7 (ε> 0). When processing by the caster operation command means 16 is started (S1), the signal corresponding to the difference angle ε and the reference difference angles (“+ 0 °”, “+ 90 °”, “+ 180 °”) stored in the memory 15 are stored. ”,“ + 270 ° ”,“ + 360 ° ”) (S2).

As shown in FIG. 5 (a1), when it is determined that the difference angle ε is not less than “+ 0 °” and less than “+ 90 °”, that is, the magnitude of the difference angle ε is less than “90 °”. In this case (| ε | <90 °), the caster operation command means 16 determines that the difference angle ε is set as the rotation angle ξ (S3) and moves the rotational drive direction of the wheel 90 from the joystick 8 to the target movement. It is determined to be “same” as before the direction θ is instructed (the first signal is supplied) (S4).

Further, as shown in FIGS. 5B1 and 5C1, when it is determined that the difference angle ε is not less than “+ 90 °” and not more than “+ 270 °”, that is, the magnitude of the difference angle ε is “90”. When the angle is not less than “°” and not more than “270 °” (90 ° ≦ | ε | ≦ 270 °), the caster operation command means 16 determines that the angle obtained by subtracting 180 ° from the difference angle ε is the rotation angle ξ. At the same time (S5), it is determined that the direction of rotational driving of the wheel 90 is "reverse" to that before the target movement direction θ is instructed from the joystick 8 (the first signal is supplied) (S6).

Further, as shown in FIG. 5 (d1), when it is determined that the difference angle ε exceeds “+ 270 °” and is not more than “+ 360 °”, the caster operation command unit 16 determines that the difference angle ε is 360 ° from the difference angle ε. Is determined to be the rotation angle ξ (S7), and the direction of rotational driving of the wheel 90 is indicated before the target movement direction θ is instructed from the joystick 8 (the first signal is supplied). It is determined to be “same” (S8).

  Next, a case where the difference angle ε is “negative” will be described with reference to FIGS. 6 and 7 (ε <0). Similarly to the above, when the processing by the caster operation command means 16 is started (S1), the signal corresponding to the difference angle ε and the reference difference angles (“−0 °”, “−” The data corresponding to “90 °”, “−180 °”, “−270 °”, “−360 °”) are compared (S2).

As shown in FIG. 6 (a2), when it is determined that the difference angle ε exceeds “−90 °” and is equal to or less than “−0 °”, that is, the magnitude of the difference angle ε is “90 °”. If the angle is less than (| ε | <90 °), the caster operation command means 16 determines that the difference angle ε is the rotation angle ξ (S3), and sets the direction of rotational driving of the wheel 90 to the joystick 8 Is determined to be the same as before the target movement direction θ is instructed (the first signal is supplied) (S4).

As shown in FIGS. 6B2 and 6C2, when it is determined that the difference angle ε is not less than “−270 °” and not more than “−90 °”, that is, the magnitude of the difference angle ε is When the angle is not less than “90 °” and not more than “270 °” (90 ° ≦ | ε | ≦ 270 °), the caster operation command unit 16 sets the angle obtained by adding 180 ° to the difference angle ε as the rotation angle ξ. Is determined (S9), and the rotational driving direction of the wheel 90 is determined to be "reverse" from that before the target movement direction θ is instructed from the joystick 8 (the first signal is supplied) (S10). ).

Further, as shown in FIG. 6 (d2), when it is determined that the difference angle ε is not less than “−360 °” and less than “−270 °”, the caster operation command means 16 sets the difference angle ε to 360. It is determined that the angle obtained by adding the angle is set as the rotation angle ξ (S7), and before the target movement direction θ is instructed from the joystick 8 as the rotation driving direction of the wheel 90 (the first signal is supplied). It is determined to be “same” (S8).

  Here, when FIG. 5 (d1) is compared with FIG. 6 (a2), the value of the difference angle ε is substantially the same. Therefore, as described above with reference to FIG. 6 (a2), FIG. 5 (d1) also corresponds to a case where the magnitude of the difference angle ε is less than “90 °” (| ε | <90 °), This is equivalent to setting the difference angle ε as the rotation angle ξ. Similarly, when FIG. 6 (d2) is compared with FIG. 5 (a1), the value of the difference angle ε is substantially the same. Therefore, as described above with reference to FIG. 5 (a1), FIG. 6 (d2) also corresponds to a case where the magnitude of the difference angle ε is less than “90 °” (| ε | <90 °), This is equivalent to setting the difference angle ε as the rotation angle ξ.

  As described above, when the magnitude (| ε |) of the difference angle ε is less than 90 °, the caster operation command means 16 determines that the difference angle ε is the rotation angle ξ, and rotates the wheel. If the difference angle magnitude (| ε |) is 90 ° or more, 180 ° is added to or subtracted from the difference angle ε. The rotation angle ξ is determined to be the rotation angle ξ, and the rotation driving direction of the wheel 90 is determined to be “reverse” from that before the target movement direction θ is instructed. Then, as will be described later, the determined rotation angle ξ and the direction of rotation drive are commanded to the output means 22. In the present embodiment, the control direction is changed depending on whether or not the magnitude (| ε |) of the difference angle ε is 90 ° or more, but it is needless to say that the control direction is not limited to 90 °. The direction may be changed depending on whether the angle is 100 ° or more.

  Next, the timer 17, the operation state determination means 18, the stop position command means 19, the selection means 20, the comparison means 21, and the output means 21 will be described with reference to FIG.

  The operation state determination means 18 is supplied from the operation amount reading means 12 with an xy signal formed when the passenger operates the joystick (movement direction instructing means) 8 in the direction in which he wants to move. Then, the operation state determination means 18 supplies a signal indicating that the xy signal is supplied to the timer 17 at predetermined intervals in a state where the xy signal is supplied. The timer 17 sequentially resets the count value every time the signal from the operation state determination means 18 is supplied, and further performs an increment operation of the count value.

  When the xy signal is not supplied from the operation amount reading unit 12 to the operation state determination unit 18 and a signal indicating that the xy signal is supplied is not supplied from the operation state determination unit 18 to the timer 17 for a predetermined time or more. The timer 17 counts up, and a signal indicating that the timer 17 has been counted up is supplied from the timer 17 to the operation state determination means 18. As described above, when the signal indicating that the count is up is supplied from the timer 17 to the operation state determination unit 18, the operation state determination unit 18 outputs a stop signal. In the present embodiment, the time for the timer 17 to count up is set to “4 seconds”.

  When the stop signal is supplied from the operation state determination means 18, the stop position command means 19 outputs a stop position signal indicating the stop position of the drive caster (3, 4, 5). The stop position of the drive casters (3, 4, 5) indicated by the stop position signal is the rotational position where the directions of the wheels 90 of the respective drive casters (3, 4, 5) are directed toward each other, that is, adjacent drives. The angle of the caster (3, 4, 5) in the direction of the wheel 90 is set to a rotational position at which the angle is 120 °.

  The selection means 20 is supplied with a command signal regarding the rotation angle ξ and the direction of rotation drive from the caster operation command means 16 and a stop position signal from the stop position command means 19. When the stop position signal from the stop position command means 19 is supplied to the selection means 20, this stop position signal is selected with priority, and the stop position signal from the stop position command means 19 determines the comparison means 21. Via the output means 22 for supplying a control current to the electric motor 70.

  The comparison means 21 is supplied with a signal corresponding to the current driving direction θ of the wheel 90 from the angle reading means 11, and a stop position signal from the stop position command means 19 and a signal corresponding to the driving direction θ. The stop position signal is supplied to the output means 22 until the driving direction θ of the wheel 90 matches the stop position signal from the stop position command means 19.

On the other hand, when the stop position signal from the stop position command means 19 is not supplied to the selection means 20, the command signal from the caster operation command means 16 is selected by the selection means 20, and the output means via the comparison means 21. 22 is supplied. The comparison means 21 compares the signal corresponding to the rotation angle ξ output from the caster operation command means 16 with the signal corresponding to the drive angle θ, and the wheels 90 from the caster operation command means 16 until the wheel 90 rotates by the rotation angle ξ. A command signal is supplied to the output means 22. In response to this command signal, the output means 22 supplies a control current to the electric motor 70, rotates the direction of the wheel 90 of the differential caster (3, 4, 5) by the rotation angle ξ, and thereby changes the direction of the wheel 90 to a new wheel. The direction is 90. Then, the wheel 90 is rotationally driven in the rotational drive direction corresponding to the command signal from the caster operation command means 16.

  Next, the first effect of the control device 10 according to the present invention will be described with reference to FIGS. FIG. 8 shows the drive caster (3) when the difference angle ε is less than 90 ° (| ε | <90 °) shown in FIGS. 5 (a1) (d1) and 6 (a2) (d2). , 4, 5). On the other hand, FIG. 9 shows a driving caster when the magnitude of the difference angle ε is 90 ° or more (| ε | ≧ 90 °) shown in FIGS. 5 (b1) (c1) and 6 (b2) (c2). The operation of (3,4,5) is shown.

  As shown in FIG. 8, when the magnitude of the difference angle ε is less than 90 ° (| ε | <90 °), the difference angle ε is set as the rotation angle ξ, and the drive caster (3 , 4, 5), the direction of the wheels (91, 92) is rotated. At this time, since the rotation angle ξ is less than 90 °, it does not take much time to rotate the direction of the wheels (91, 92) in the target direction. And the electric wheelchair 1 can be rapidly moved to a target moving direction by making the direction of rotational drive of a wheel (91,92) into the same direction as before the target moving direction was instruct | indicated.

  On the other hand, as shown in FIG. 9, when the magnitude of the difference angle ε is 90 ° or more (| ε | ≧ 90 °), an angle obtained by adding and subtracting 180 ° to the difference angle ε is set as the rotation angle ξ, and the rotation angle ξ The direction of the wheels (91, 92) of the drive casters (3, 4, 5) is rotated by an amount corresponding to. At this time, the rotation angle ξ is an angle obtained by adding and subtracting 180 ° to the difference angle ε, and is set to be less than 90 °. Therefore, it takes much time to rotate the direction of the wheels (91, 92) in the target direction. Is not required. And the electric wheelchair 1 can be quickly moved to a target moving direction by making the direction of rotational drive of a wheel (91,92) into the direction opposite to the direction before a target moving direction is instruct | indicated.

  Next, the second effect of the control device 10 of the present embodiment will be described based on FIGS. 10 and 11. As described above, when the joystick 8 is not operated by the passenger for a predetermined time or more, that is, when the electric wheelchair 1 is not operated, the drive casters (3, 4, 5) are in the stop position as shown in FIG. It is instructed to turn the direction of the wheel 90 toward. And the direction of the wheel 90 of a drive caster (3, 4, 5) is orient | assigned to the position shown in FIG.

  As shown in the figure, the stop position of the drive casters (3, 4, 5) is a direction in which the directions of the wheels 90 intersect at an angle of 120 °. Therefore, even if the wheel 90 of the drive caster (3, 4, 5) is not equipped with a brake mechanism, even if force is applied from various external directions when the electric wheelchair 1 is not operated, the electric wheelchair 1 is not moved. That is, the electric wheelchair 1 can be stably kept in a stopped state without providing a brake mechanism.

1 Electric wheelchair 2 Base member 3 First differential caster (drive caster)
4 Second differential caster (drive caster)
5 Third differential caster (drive caster)
7 Chair 8 Joystick (movement direction instruction means)
DESCRIPTION OF SYMBOLS 10 Control apparatus 11 Angle reading means 12 Operation amount reading means 13 Target angle calculation means 14 Difference angle calculation means 15 Memory 16 Caster operation command means 17 Timer 18 Operation state determination means 19 Stop position command means 20 Selection means 21 Comparison means 22 Output means 90 Wheel 103 Encoder (Drive direction detection means)

Claims (1)

A chair, a base member on which the chair is provided , a spindle attached to the base member from below and rotatably supported by the base member, an electric motor attached to one end of the spindle, and the electric motor A driving caster having a wheel that is driven to rotate by a motor, and capable of rotating the driving direction of the wheel in a target direction by the rotation of the supporting shaft relative to the base member; and the driving direction from the rotational position of the supporting shaft. In an electric wheelchair that includes a driving direction detecting means for detecting the target, a joystick for detecting a target moving direction of the driving caster, and a control device that supplies a control current to the electric motor, and that moves by rotational driving of the wheels,
The joystick detects a target moving direction of the wheel based on a predetermined operation axis direction of the joystick , and supplies a first signal to the control device;
The drive direction detection means detects the drive direction with reference to the operation axis direction and supplies a second signal to the control device;
The control device includes:
Output means for supplying a control current to the electric motor;
When the magnitude of the difference angle, which is the difference between the driving direction and the target moving direction, is less than a predetermined angle of 80 ° to 100 ° based on the first signal and the second signal The difference angle is set as a rotation angle, and the output means is instructed to rotate the drive caster by the rotation angle, and the direction of rotation driving of the wheel is made the same as before the first signal is supplied. Command the output means,
Based on the first signal and the second signal, wherein when the magnitude of the difference angle is the is the predetermined angle or more, an angle obtained by adding or subtracting an approximately 180 ° to the difference angle and the rotation angle, the drive A caster operation command for instructing the output means to rotate the caster by the rotation angle, and for instructing the output means to reverse the direction of rotational driving of the wheel to that before the first signal is supplied. Means, and
The electric wheelchair is capable of directing the driving direction of the wheel to the target moving direction by a control current from the output means.

Images