JP7614162B2 - Electric wheelchair - Google Patents

Description

The technology disclosed in this specification relates to electric wheelchairs.

The electric wheelchair of Patent Document 1 can go up and down stairs. The electric wheelchair of Patent Document 1 has main wheels arranged on both sides of the chair, a support bar extending rearward from the chair, and auxiliary wheels located rearward of the main wheels. The main wheels are driven by a motor. The rear end of the support bar swings up and down by an actuator. The auxiliary wheels also swing up and down by an actuator. This electric wheelchair can go up and down stairs by lifting the auxiliary wheels and supporting the chair with the main wheels and support bar.

JP 2022-95277 A

It is possible to provide a front support bar that extends forward to prevent the chair from tipping forward when descending stairs. The front support bar can support the chair when it tilts forward. In that case, if both the front and rear support bars touch the ground and the main wheels lift off the ground, there is a risk that the entire electric wheelchair will slide down the stairs. This specification provides technology for an electric wheelchair with support bars at the front and rear of the chair, which prevents both support bars from touching the ground when descending stairs.

The electric wheelchair disclosed in this specification includes a chair, main wheels arranged on both sides of the chair, a front support bar, a rear support bar, and a controller. The main wheels are driven by a motor. The front support bar extends forward of the chair, and a front end of the front support bar is swung up and down by an actuator. The rear support bar extends backward of the chair, and a rear end of the front support bar is swung up and down by an actuator. When the electric wheelchair descends stairs, the controller determines the position of the front end of the front support bar as follows. That is, the controller determines the position of the front end based on one of the slope angle that a plane connecting the edges of each step of the stairs makes with the horizontal plane, and the edge position angle that a line connecting the edge of each step of the stairs that is closest to the center of the main wheels in the horizontal direction with the center of the main wheels makes with the direction perpendicular to the seat surface of the chair . The "edge of each step" refers to the right angle portion of the upper corner of each step of the stairs.

By determining the position of the front end as described above, the front end is held in a position above the edge of the stairs. If the electric wheelchair tilts forward and the rear support bar lifts off the ground, the front end of the front support bar will touch the stairs, preventing the chair from rotating forward. In this case, the front end and the main wheel are in contact with the ground, so the entire electric wheelchair will not slide down the stairs.

Details and further improvements of the technology disclosed in this specification are explained in the "Description of Embodiments" below.

FIG. 2 is a side view of the electric wheelchair of the embodiment (before climbing a step). 1A and 1B are diagrams illustrating a target posture angle and a slope angle of a chair. 11 is a graph showing an example of a relationship between the total value of a target attitude angle and a slope angle and a front end position. 11A and 11B are schematic diagrams showing the relationship between the edge position angle and the position of the front end portion. 1 is a graph for determining leading edge position versus edge position angle. Fig. 6A shows an example in which the front end position is selected based on the slope angle, and Fig. 6B shows an example in which the front end position is selected based on the edge position angle. 10 is a schematic diagram showing the relationship between the position of the rear end of the rear support bar and the contact point angle. FIG. 11 is a graph showing an example of a relationship between the position of the rear end of the rear support bar and the contact point angle.

An electric wheelchair 10 according to an embodiment will be described with reference to the drawings. FIG. 1 shows a side view of the electric wheelchair 10 according to the embodiment. The electric wheelchair 10 according to the embodiment includes a chair 11, main wheels 12, and a motor 13. The main wheels 12 are disposed on both sides of the chair 11 and are driven by the motor 13. Note that in FIG. 1, the main wheels 12 are drawn with dashed lines, and devices located behind the main wheels 12 (devices that are normally hidden by the main wheels 12 and cannot be seen) are drawn with solid lines so that the structure of the electric wheelchair 10 can be clearly seen.

The electric wheelchair 10 further comprises a front support bar 14, a rear support bar 15, and actuators 16 and 17. The front support bar 14 extends forward of the chair 11. The rear end of the front support bar 14 is supported by a pivot 18 so that it can swing. The actuator 16 is attached between the chair 11 and the front support bar 14. The actuator 16 is of a linear type, and when it expands and contracts, the front end 14a of the front support bar 14 swings up and down. A freely rotating auxiliary wheel is attached to the tip of the support bar 14.

The symbols "14a_U" and "14a_L" in FIG. 1 represent the movable range of the front support bar 14. The front end 14a_U represents the upper limit position of the front support bar 14 (i.e., the upper limit position of the front end 14a). The front end 14a_L represents the lower limit position of the front support bar 14 (i.e., the lower limit position of the front end 14a). As the front support bar 14 swings, the front end 14a moves between the position indicated by the front end 14a_U in FIG. 1 and the position indicated by the front end 14a_L.

The front support bar 14 is a device for preventing the electric wheelchair 10 (chair 11) from tipping forward. The front end 14a_L can be positioned below the horizontal floor F so that the front end 14a can be positioned directly above the step below the stairs when the electric wheelchair 10 is descending stairs.

The rear support bar 15 extends to the rear of the chair 11. The front end of the rear support bar 15 is supported by a pivot 18 so that it can swing. An actuator 17 is attached between the chair 11 and the rear support bar 15. The actuator 17 is of a linear type, and when it expands and contracts, the rear end 15a of the rear support bar 15 swings up and down. The pivot 18 is located behind the axle 12a of the main wheel 12 and below the axle 12a. In other words, the pivot 18 is located below and behind the axle 12a.

The rear end 15a of the rear support bar 15 has a sled shape. The center of gravity of the electric wheelchair 10 (including the weight of the seated user) is located behind the center (axis 12a) of the main wheels 12. Therefore, the rear end 15a of the rear support bar 15 is in contact with the floor F. By moving the rear end 15a up and down, the target attitude angle of the chair 11 (the rotation angle of the chair 11 around the axis 12a of the main wheels 12) can be adjusted.

The motor 13 and the actuators 16, 17 are controlled by a controller 20. The controller 20 is built into the chair 11. Various sensors 21 are also attached to the chair 11. The sensors 21 include a vehicle speed sensor that measures the speed of the electric wheelchair 10, an angle sensor that measures the attitude angle of the chair 11, and a road surface sensor that detects the shape of the surface on which the electric wheelchair 10 is traveling. When the electric wheelchair 10 goes up or down stairs, the road surface sensor detects the shape of the stairs. Illustration of the individual sensors is omitted.

The electric wheelchair 10 makes clever use of the front support bar 14 and rear support bar 15 to prevent tipping over when descending stairs.

When the electric wheelchair 10 descends stairs, the controller 20 determines the position of the front end 14a based on either the slope angle or the edge position angle. The controller 20 controls the front support bar 14 (actuator 16) so that the determined front end 14a is achieved. In the following, the position of the front end 14a is referred to as the "front end position." The position of the rear end 15a of the rear support bar 15 is referred to as the "rear end position."

The process of determining the front end position based on the slope angle will be described with reference to Figures 2 and 3. The slope angle As refers to the angle between the plane (slope plane SL) connecting the multiple edges 91 of the stairs 90 and the horizontal plane HL (see Figure 2). The "stair edge 91" refers to the right angle at the top of each step of the stairs 90, as shown in Figure 2. In Figure 2, some parts are omitted and the electric wheelchair 10 is depicted in a simplified form.

Here, we define the target posture angle At of the chair 11. The target posture angle At refers to the angle between an axis (front axis Cf) that faces forward and is parallel to the seat surface of the chair 11, and the horizontal plane HL. The axis perpendicular to the seat surface is called the vertical axis Cv (see Figure 2). The origin where the front axis Cf and the vertical axis Cv intersect is located at the center Ce of the main wheel 12. The front axis Cf and the vertical axis Cv are in a local coordinate system fixed to the chair 11.

As mentioned above, the posture angle of the chair 11 is adjusted by the position of the rear end 15a of the rear support bar 15 (rear end position). The controller 20 controls the rear support bar 15 so that the actual posture angle of the chair 11 coincides with the target posture angle At.

The controller determines the front end position using the sum of the slope angle As and the target attitude angle At (As+At) as a parameter so that the front end 14a is kept at a predetermined distance from the slope plane SL.

The front end position that maintains a predetermined distance from the slope plane SL depends on the geometric structure of the electric wheelchair 10. Therefore, the front end position that maintains a predetermined distance from the slope plane SL is determined in advance in the form of a map (or function) that outputs the front end position for the input value (As + At) and is stored in the controller 20. FIG. 3 shows an example of the relationship between the front end position and the sum of the slope angle As and the target attitude angle At. The vertical axis indicates the front end position. The front end position on the vertical axis is expressed as a percentage when the upper limit position (the position of the front end 14a_U) of the front support rod 14 described above is 0 [%] and the lower limit position (the position of the front end 14a_L) is 100 [%]. As mentioned above, the front end position that maintains a predetermined constant distance from the slope plane SL depends on the geometric structure of the electric wheelchair 10 and is determined in advance as shown in FIG. 3.

The front end position is determined based on the sum of the target posture angle At and the slope angle As. Therefore, if the actual posture angle of the chair 11 deviates from the target posture angle At and tilts forward, the front end 14a touches the staircase 90, preventing the chair 11 from tipping forward.

The process of determining the front end position based on the edge position angle will be described with reference to Figures 4 and 5. The edge position angle Ag refers to the angle between the edge (edge 91a in Figure 4) closest to the center Ce of the main wheel 12 in the horizontal direction and the line connecting the center Ce, and the vertical axis Cv of the local coordinate system (see Figure 4). For ease of explanation, the edge 91a closest to the center Ce of the main wheel 12 in the horizontal direction is referred to as the proximate edge 91a. The controller 20 determines the front end position so that a predetermined distance is maintained between the front end 14a and the proximate edge 91a in the vertical direction. This front end position depends on the edge position angle Ag.

The front end position that maintains a predetermined distance from the adjacent edge 91a in the vertical direction depends on the geometric structure of the electric wheelchair 10. The front end position that maintains a predetermined distance is determined in advance in the form of a map (or function) with the edge position angle Ag as an input value, and is stored in the controller 20. Figure 5 shows an example of the relationship of the front end position to the edge position angle Ag. The values on the vertical axis have the same meaning as those on the vertical axis of the graph in Figure 3.

While the electric wheelchair 10 is descending the stairs, the controller 20 determines the front end position based on the sum of the target attitude angle At and the slope angle As. This front end position is referred to as the slope front end position. At the same time, the controller 20 also determines the front end position based on the edge position angle Ag. This front end position is referred to as the edge front end position. The controller 20 compares the slope front end position with the edge front end position and selects the higher one. The controller 20 controls the front support bar 14 (actuator 16) so that the selected front end position is realized. The controller 20 repeats the determination of the front end position and the control of the front support bar 14 at a predetermined control period.

With reference to Figure 6, an example will be described in which the controller 20 selects either the slope front end position or the edge front end position. In Figure 6 (A), the proximal edge 91a is located rearward of the center Ce of the main wheel 12, and the edge position angle is angle Ag_a. The slope angle is angle As. At this time, the slope front end position (position of the front end 14a_sl) is higher than the edge front end position (position of the front end 14a_eg). The controller 20 selects the slope front end position (position of the front end 14a_sl) and controls the front support rod 14 (actuator 16) so that this position is realized.

In FIG. 6(B), the electric wheelchair 10 moves forward a little from the state in FIG. 6(A), and the adjacent edge moves to edge 91b. The adjacent edge 91b is located forward of the center Ce of the main wheel 12, and the edge position angle is angle Ag_b. The slope angle is angle As. At this time, the edge front end position (position of front end 14a_eg) is higher than the slope front end position (position of front end 14a_sl). The controller 20 selects the edge front end position (position of front end 14a_eg) and controls the front support bar 14 (actuator 16) to realize this position. In this way, if the posture angle of the chair 11 is tilted forward away from the target posture angle, the front end 14a comes into contact with the stairs, and a forward tipping is prevented.

The control of the rear support bar 15 will be described with reference to Figures 7 and 8. In Figure 7, the rear end 15a_U indicates the upper limit position of the rear support bar 15 (the upper limit position of the rear end 15a), and the rear end 15a_L indicates the lower limit position of the rear support bar 15 (the lower limit position of the rear end 15a).

As mentioned above, the posture of the chair 11 is determined by the position of the rear support bar 15. The controller 20 controls the rear support bar 15 (actuator 17) so as to realize the target posture angle. Instead of such control, the controller 20 may determine the rear end position (position of the rear end 15a) of the rear support bar 15 based on the contact point angle Ast, and control the rear support bar 15 (actuator 17) so as to realize the determined rear end position. Here, the contact point angle Ast refers to the angle formed by the line connecting the edge (edge 91c in the case of FIG. 7) with which the main wheel 12 is in contact and the center Ce of the main wheel 12, and the vertical axis Cv. The vertical axis Cv refers to an axis perpendicular to the seat surface of the chair 11. For convenience of explanation, the edge 91c with which the main wheel 12 is in contact is referred to as the contact edge 91c. The controller 20 determines the rear end position so that a predetermined distance is maintained between the line passing through the contact edge 91c and tangent to the wheel 12 and the rear end position.

The rear end position that maintains a predetermined distance from the line that passes through the contact edge 91c and is tangent to the wheel 12 depends on the contact point angle Ast. Therefore, such a rear end position is determined in advance in the form of a map (or a function) that outputs the rear end position for the input value (contact point angle Ast) and is stored in the controller 20. Figure 8 shows an example of the relationship between the rear end position and the contact point angle Ast.

The vertical axis in FIG. 8 indicates the rear end position. The front end position on the vertical axis is expressed as a percentage, with the upper limit position (position of rear end 15a_U) of the rear support bar 15 described above being 0% and the lower limit position (position of rear end 15a_L) being 100%. As mentioned above, the rear end position that maintains a predetermined distance from the line that passes through contact edge 91c and touches wheel 12 depends on the geometric structure and ground contact point angle Ast of electric wheelchair 10, and is determined in advance as shown in FIG. 8.

The rear end position targeted by the controller 20 is the current rear end position plus "gain x attitude error." The controller 20 controls the rear support rod 15 (actuator 17) so that the targeted rear end position is achieved.

The electric wheelchair 10 is equipped with a joystick that is operated by the seated user. Tilt the joystick forward to move the electric wheelchair 10 forward, and tilt the joystick backward to move the electric wheelchair 10 backward. When the joystick is in the neutral position, the electric wheelchair 10 stops. Increasing the angle at which the joystick is tilted forward increases the forward speed. Increasing the angle at which the joystick is tilted backward increases the backward speed of the electric wheelchair 10.

Depending on the situation, the electric wheelchair 10 needs to decelerate or stop against the user's operation for safety. The controller 20 determines the speed of the electric wheelchair 10 by multiplying the tilt of the joystick by a predetermined gain. There are several types of gains. Gain A is a gain according to the attitude control error, and is set to be smaller as the attitude control error increases. Gain B is a gain according to the slope angle, and is set to be smaller as the slope angle increases. Gain C is a gain according to the control error of the rear support bar 15, and is set to be smaller as the control error increases. Gain D is a gain according to the roll attitude error of the electric wheelchair 10, and is set to be smaller as the attitude error increases. Gain E is a gain according to the height of the step, and is zero when the step is larger than a predetermined threshold. When the step is smaller than the threshold, gain E is set to "1". The controller 20 determines the speed of the electric wheelchair 10 by multiplying the tilt of the joystick by the above-mentioned gains A to E. If the step is greater than a certain threshold, the gain E becomes zero and the electric wheelchair 10 stops moving.

Notes on the technology described in the examples are as follows. The shape of the stairs can be measured using a LiDAR sensor, a 3D image sensor, multiple distance sensors, etc. LiDAR is an abbreviation for "Light Detection and Ranging." A LiDAR sensor emits a laser in multiple directions and measures the distance to an obstacle (step) in each direction. The external shape of the obstacle (step) is obtained from the measured distance in each direction. A 3D image sensor photographs the stairs with two cameras and measures the shape of the stairs based on the principle of stereoscopic vision. The shape of the stairs can also be measured using a sensor in which multiple distance sensors are arranged so that laser light is emitted in parallel.

The controller 20 may estimate the edge position of the stairs relative to the body of the electric wheelchair 10, the inclination angle of the stairs (the slope angle described above), and the ground contact position of the main wheels, and control the front support bar 14 and the rear support bar 15 using a control map corresponding to these.

The electric wheelchair 10 may have a contact determination device that determines whether the front and rear support rods 14, 15 are in contact with the ground, and the controller 20 may change control depending on whether the front and rear support rods 14, 15 are in contact with the ground.

The controller 20 may also decelerate the speed of the electric wheelchair 10 depending on the control error of the posture of the front and rear support rods 14, 15.

The controller 20 may set the speed of the electric wheelchair 10 to zero if the height of a step in the traveling direction of the electric wheelchair 10 is greater than the radius of the main wheels 12. The "traveling direction" includes both forward and reverse.

The electric wheelchair 10 is equipped with power sources for the motor 13, actuators 16, 17, controller 20, and sensor 21 under the chair 11 (or inside the back of the chair 11), but the power sources are not shown in the figure.

The front support rods 14 may be provided on both sides of the chair 11, or only on one side of the chair 11. In the latter case, a cross bar is provided at the tip of the front support rod, and the front support rod and rear support rod can stably lift the main wheel. The rear support rods may also be located on both sides of the chair 11, or one rear support rod may be located in the center of the chair 11 in the left-right direction.

Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

10: Electric wheelchair 11: Chair 12: Main wheel 12a: Axle 13: Motor 14: Front support rod 14a: Front end 15: Rear support rod 15a: Rear end 16, 17: Actuator 18: Pivot 20: Controller 21: Sensor 90: Stairs 91: Edge

Claims (3)

An electric wheelchair,
A chair and
Main wheels are arranged on both sides of the chair and are driven by a motor;
A front support bar extending forward of the chair and having a front end that swings up and down;
A rear support bar extending rearward of the chair and having a rear end that swings up and down;
A controller for controlling the front support rod, the rear support rod, and the main wheels;
Equipped with
The center of gravity of the electric wheelchair is located rearward of the axis of the main wheels,
When the electric wheelchair descends stairs, the controller determines the position of the front end based on one of the slope angle that a plane connecting the edges of each step of the stairs makes with a horizontal plane and the edge position angle that a line connecting the edge of each step of the stairs that is closest to the center of the main wheel in the horizontal direction and the center makes with a direction perpendicular to the seat of the chair . The electric wheelchair of claim 1, wherein the controller selects the higher of the position of the front end determined based on the slope angle and the position of the front end determined based on the edge position angle. The electric wheelchair according to claim 1 or 2, wherein the controller sets the speed of the electric wheelchair to zero when the height of a step in the traveling direction of the electric wheelchair is greater than the radius of the main wheel.

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