Motorized wheelchair

Abstract

The invention relates to a motorized wheelchair (10) comprising: a lower module (20), a pair of drive wheels (22) mounted on the lower module, and a motor drive (221) configured to rotationally drive the pair of drive wheels, an upper module (60) comprising a seat (62) and a ground contact member (63), the upper module being mounted so as to be articulated with the lower module by a pivot (50), so that the upper module and the lower module pivot relative to one another about the pivot under the effect of a control force exerted on the lower module by a user seated on the seat, and a control unit configured to detect a change in inclination of the lower module relative to the horizontal caused by the control force, and to generate a control moment by means of the motor drive on at least one of the drive wheels in order to re-establish an initial inclination of the lower module.

Description

[0001] DESCRIPTION

[0002] TITLE: Motorized Wheelchair

[0003] technical field

[0004] The present invention relates to a motorized wheelchair, particularly for use by persons with reduced mobility.

[0005] State of the art

[0006] There are various motorized wheelchairs with a self-balancing motorized base and a pair of drive wheels mounted on it. These wheelchairs move on their two drive wheels. Movement is achieved by the user and their seat tilting in the corresponding direction. The shift in the center of gravity caused by the user's movements engages the drive wheels, propelling the wheelchair forward. If the user wishes to remain stationary, for example, to handle objects, this movement can be not only inconvenient and require constant attention to maintain a stable center of gravity, but also dangerous, especially when handling objects requiring careful handling, such as a container of boiling water or power tools.

[0007] To allow the user to maintain a stationary position, the motorized base of some wheelchairs is equipped with a system of deployable crutches. These crutches ensure the user's stability when stopped and provide safety when handling objects.

[0008] However, the aforementioned systems have the disadvantage of immobilizing the wheelchair, so that if the user wishes to move again, it is necessary to retract the crutches, and then redeploy them if they wish to immobilize again, so that the use of this type of wheelchair is tedious, especially indoors.

[0009] In document EP 3 081 472, the motorized base of the wheelchair is equipped with retractable front and rear outriggers fitted with wheels. However, this system presents a risk of falling during movement if the center of gravity shifts. Furthermore, deploying the outriggers is time-consuming.

[0010] It is therefore desirable to offer a motorized wheelchair of simple design which provides the user with good stability and maneuverability in a stationary position, good versatility, while ensuring good safety, particularly in the event of loss of traction.

[0011] Summary

[0012] Embodiments relate to a motorized wheelchair comprising: a lower module; a pair of drive wheels mounted on the lower module; a motor configured to rotate the pair of drive wheels; an upper module comprising a seat and a ground contact member, the upper module being mounted articulated with the lower module by a pivot, to pivot relative to each other around the pivot under the effect of a control force exerted on the lower module by a user seated on the seat; and a control unit configured to detect a change in the inclination of the lower module relative to the horizontal caused by the control force, and to generate a control torque using the motor on at least one of the drive wheels in order to restore an initial inclination of the lower module.

[0013] Thanks to this configuration, the wheelchair offers excellent versatility, particularly when moving around. Because the upper module can pivot relative to the lower module, the user can choose to move with the ground contact point either resting on the ground or raised. When the ground contact point is on the ground, the user can move safely and stably. Furthermore, the ground support of the ground contact point attached to the upper module, combined with the articulation between the upper and lower modules, allows the user wishing to remain stationary to lean or shift their center of gravity, for example, to manipulate or pick up an object, without causing imbalance or a change in the tilt of the lower module, and therefore without the wheelchair moving.This allows the user to avoid having to compensate for an unexpected movement of the wheelchair and eliminates any safety risks when handling dangerous objects, while also offering immediate mobility, for example, to reach another nearby object, without being immobilized or having to wait for crutches to retract. This feature makes the wheelchair particularly suitable for use in indoor spaces, such as a kitchen.

[0014] Furthermore, tilting the ground contact element is easily achieved by the user applying a push or pull on the lower module. When the ground contact element is raised, the user can move at high speeds while minimizing the risk of the ground contact element encountering an obstacle and causing a fall. In addition, in this position, the wheelchair is particularly well-suited for off-road use, for example, on rocky and / or steep terrain, thanks to the tilt control of the lower module provided by the control unit. Tilting the ground contact element into the raised position also makes it safer to navigate obstacles such as logs in the forest, steps, or curbs.Indeed, the user can guide the ground contact device over the obstacle and then test the drive wheels' grip on it without risk of losing balance. In fact, if the drive wheels slip on the obstacle, they remain in front of it, and the wheelchair remains balanced on three points.

[0015] Finally, in the event of a loss of traction, while the wheelchair is moving on its drive wheels only, it can regain a stable equilibrium by returning to a position of support on the ground at at least three points thanks to the ground contact system, thus preventing the user from falling. This feature therefore offers a particularly important safety guarantee and psychological comfort, since the user knows that the risk of falling due to loss of traction is limited.

[0016] According to one embodiment, each of the drive wheels is mobile in rotation around an axis of rotation passing through a center of the drive wheel, the axes of rotation of the drive wheels and an axis of rotation of the pivot being parallel to each other to within a few degrees at most.

[0017] According to one embodiment: the pivot axis is located at a distance less than or equal to 30 mm from the pivot axis of rotation of each drive wheel; and / or the pivot axis of rotation of each drive wheel and the pivot axis of rotation are located in the same frontal plane when the ground contact member and the drive wheels are in contact with a flat ground, the frontal plane extending perpendicularly to a rear-to-front direction of movement of the wheelchair; and / or the pivot axis of rotation coincides with the pivot axis of rotation of each drive wheel; and / or the pivot axis of rotation is located below the pivot axis of rotation of the drive wheels in the frontal plane.

[0018] According to one embodiment, the control unit is configured to control the wheel drive in order to keep the lower module substantially horizontal, in a direction towards the front or the rear of the wheelchair.

[0019] According to one embodiment, the control unit is configured to control the motorization of the wheels: according to a first operating mode in which the wheelchair is in contact with the ground on both drive wheels and on the ground contact element; and according to a second operating mode in which the wheelchair is in contact with the ground on only the two drive wheels, the ground contact element being in a raised position relative to the ground.

[0020] According to one embodiment, the wheelchair includes a control element coupled to the control unit, the control element being configured to control the control unit in order to control the motorization of the wheels to keep fixed or move the wheelchair in a forward or backward direction, switching to the first operating mode when the user exerts a push on the control element in the forward direction, having an intensity less than a push threshold value; and switching to the second operating mode when the user exerts a push on the control element in the forward direction, having an intensity greater than the push threshold value.

[0021] According to one embodiment: the control element is mounted on a first chassis of the lower module, via an elastomer cushion connection device; and / or the control element is formed by a part of the first chassis.

[0022] According to one embodiment, the control member includes at least one force sensor arranged to detect a directional instruction to the left and / or to the right of the wheelchair, the control unit being configured to control the motorization of the wheels according to the directional instruction.

[0023] According to one embodiment, the drive wheel motorization comprises: a respective drive motor coupled to each drive wheel; or a single drive motor mounted in the lower module and coupled to both drive wheels.

[0024] According to one embodiment, the ground contact member comprises at least one idler wheel, and / or at least one sliding contact member.

[0025] According to one embodiment, the pivot is coupled to the lower module so as to be mobile along a back-to-forth movement direction of the wheelchair, the control unit being configured to control an actuator in order to adjust the position of the pivot along the back-to-forth movement direction in response to a command applied to a control element by the user.

[0026] According to one embodiment, the wheelchair includes a braking device arranged to cooperate with at least one of the drive wheels and comprising a retracted position in which the drive wheel can rotate freely and a deployed position in which the drive wheel is locked in rotation. According to one embodiment, the braking device is fixed to the upper module and / or includes a braking element arranged to cooperate with each of the drive wheels.

[0027] Embodiments may also relate to a method of using the wheelchair defined above, the method of use comprising: a first mode of operation in which the wheelchair is fixed or moves on the ground, on the two drive wheels and on the ground contact element; a second mode of operation in which the wheelchair is fixed or moves on the ground on the two drive wheels, the ground contact element being raised relative to the ground; and steps consisting of: activating the second mode of operation from the first mode of operation, under the effect of a pushing force exerted by the user on the control element directed towards the front of the wheelchair and having an intensity greater than a threshold push value;and activate the first operating mode from the second operating mode, when the user releases the control element or exerts a reverse push on it, to achieve a thrust force with an intensity lower than the thrust threshold value.

[0028] Brief description of the figures

[0029] The present invention will be better understood with the aid of the following description of exemplary embodiments with reference to the accompanying figures, in which identical reference symbols correspond to structurally and / or functionally identical or similar elements.

[0030] Figure 1 is a schematic perspective view of the front of a motorized wheelchair, according to one embodiment,

[0031] Figure 2 is a schematic side view of the wheelchair, according to one embodiment,

[0032] Figure 3 is a schematic front view of the wheelchair, according to one embodiment,

[0033] Figure 4 schematically represents the control and drive components of the wheelchair, according to one embodiment,

[0034] Figure 5 is a schematic front view of a part of the wheelchair, according to one embodiment,

[0035] Figure 6 is a schematic perspective view of the front of a motorized wheelchair, according to another embodiment,

[0036] Figure 7 is a schematic side view of the wheelchair, according to another embodiment. Figure 8 is a schematic front view of the wheelchair, according to another embodiment.

[0037] Detailed description

[0038] Figures 1 to 3 represent a motorized wheelchair 10, according to one embodiment. For clarity, structural or geometric elements are not shown to scale in these figures. The wheelchair 10 is represented in a coordinate system (X, Y, Z) comprising:

[0039] - a longitudinal direction X corresponding to a theoretical back-to-forth movement direction of the wheelchair,

[0040] - a lateral direction Y corresponding to a left-right direction of the wheelchair and transverse to the longitudinal direction X, and

[0041] - a top-bottom direction Z corresponding to a direction transverse to the longitudinal direction X and the lateral direction Y.

[0042] The wheelchair is described below in relation to:

[0043] - a horizontal plane PO defined as extending along the X and Y directions (figures 2 and 3),

[0044] - a median plane P1 extending along the X and Z directions (figure 3), and therefore perpendicular to the horizontal plane PO, and

[0045] - a frontal plane P2 extending along the lateral Y and up-down Z directions (figure 2), and therefore perpendicular to the horizontal plane PO and the median plane P1.

[0046] According to an embodiment illustrated in Figures 1 to 3, the wheelchair 10 comprises a lower module 20, an upper module 60, and at least one pivot 50. The lower module 20 includes a first frame 21, a pair of drive wheels 22, and a motor 221 for driving the two drive wheels 22 in rotation about respective axes Y1a, Y1b passing through the center of one of the wheels. The lower module 20 includes one or more axles 220, each drive wheel 22 being mounted on the first frame 21 by means of a single axle 220 or a respective axle. The drive wheels 22 can be mounted on either side of the first frame 21, for example, on the outside of the first frame 21.

[0047] The upper module 60 includes a second chassis 61 supporting a seat 62 and at least one ground contact element 63. The seat 62 is intended to accommodate a user, for example in a seated position.

[0048] The lower module 20, in particular the first chassis 21, and the upper module 60, in particular the second chassis 61, are mounted articulated relative to each other by means of the pivot 50, allowing the second chassis 61 and the first chassis 21 to pivot relative to each other around an axis Y2 extending along the Y direction, under the effect of a control force exerted on the first chassis 21 by the user. The control force can be a push (forward) or a pull (backward), along the X direction.

[0049] The drive system comprises a single drive motor for rotating the two drive wheels 22, or alternatively, two motors 221, each driving one of the drive wheels. In one embodiment, the drive wheels 22 are rotated independently by the drive system 221. This allows the rotational speed of one drive wheel 22 to be varied independently of the other. Varying the respective rotational speeds of the drive wheels 22 makes it possible to turn the wheelchair 10 to one side or the other, or even to rotate on its own axis when the speed of the wheelchair 10 along the longitudinal direction X is zero or low, or when the respective directions of rotation of the wheels are opposite to each other.

[0050] The axles 220 of the drive wheels 22 can, for example, be oriented respectively along the axes of rotation Y1a and Y1b. The axles 220 can be aligned with each other so that the axes of rotation Y1a and Y1b and the reference axis Y1 coincide. Alternatively, the axles 220, i.e., the axes of rotation Y1a and Y1b, can form a non-zero angle with respect to each other so that the drive wheels 22 have a camber angle.

[0051] According to an embodiment illustrated in the figures, the axes of rotation Y1a, Y1b of the drive wheels 22, and the axis of rotation Y2 of the pivot 50 are substantially parallel to each other. The term "parallel" should be understood here, unless otherwise indicated, as potentially meaning that the reference axis Y1 and the axis of rotation Y2 coincide.

[0052] According to one embodiment, the rotation axis Y2 coincides with the reference axis Y1, or is disposed at a distance D less than or equal to 30mm below the reference axis Y1 in the front plane P2 to provide greater stability of the upper module 60.

[0053] According to one embodiment, the position of the center of gravity of the upper module 60 in the presence of the user seated on the seat 62, is adjustable along the X direction, in particular to fix it in line with the Y2 axis or slightly in front of this axis.

[0054] The wheelchair 10 includes a control system 30 configured to detect a change in inclination of the first chassis 21 relative to the horizontal along the direction X, caused by the control force applied in that direction, and to control each drive motor 221 to apply a control torque to at least one of the drive wheels 22 in response to the change in inclination.

[0055] According to one embodiment, the axis of rotation Y1 or Y1a, Y1b of the drive wheels 22 is disposed under the seat 62, for example in line with the center of gravity of the upper module 60 when the user is seated on the seat 62, and the ground contact member 63 can be disposed in front of the drive wheels 22.

[0056] The reference axis Y1 and the rotation axis Y2 of the pivot 50 are arranged in the same frontal plane P2 when the wheelchair 10 is stationary and on a flat surface. This configuration has the advantage of allowing natural balancing of the first frame 21 relative to the drive wheels 22 in a stationary position. In other words, in this arrangement of the axes Y1 and Y2 in the stationary position of the wheelchair 10, the control system 30 does not have to apply any moment to the drive wheels 22, and the user therefore does not have to compensate for any displacement of the wheelchair 10. This arrangement reduces to zero the moment exerted by the weight of the upper module 60 on the pivot axis 50 relative to the center of gravity of the lower module 20, thereby eliminating the need for the control system 30 to stabilize the first frame 21 or to rotate the drive wheels 22.The wheelchair 10 then remains in balance and the user does not have to compensate for the movement of the first chassis 21 by action on the control device 25.

[0057] According to one embodiment, the control system 30 is configured to control the wheel drive according to first and second operating modes, whether stationary or moving (forward, backward, or rotating left or right). In the first operating mode, the wheelchair 10 is maintained in contact with the ground by both drive wheels 22 and the ground contact element 63. In the second operating mode, the wheelchair 10 is maintained in contact with the ground by only the two drive wheels 22, the ground contact element 63 being raised relative to the ground.

[0058] In both operating modes, the control unit 30 can maintain a resting state in which the wheelchair 10 is stationary, with the drive speed of the drive wheels 22 being zero, and a moderate-speed movement state, with the drive wheels 22 rotating at a moderate speed. In the second operating mode, the control unit 30 can also control the drive of the drive wheels 22 at higher speeds.

[0059] According to one embodiment, the wheelchair 10 includes a control element 25 enabling: - the activation of the first operating mode and the control of forward movement (along the X direction) of the wheelchair 10 at a moderate speed, by the user applying to the control element 25 an initial forward thrust with an intensity lower than a threshold thrust value, and

[0060] - to activate the second operating mode by the user applying a second forward thrust (along the X direction) to the control unit 25, with an intensity greater than the threshold thrust value.

[0061] In practice, applying the second push to the control element 25 causes the wheelchair 10 to rear up by lifting the contact element 63 off the ground. The threshold value of this push depends on the position, along the X direction, of the center of gravity of the upper module 60 with the user seated on the seat 62, relative to the position of the Y2 axis of the pivots 50 along this direction. Indeed, it is understandable that the further forward the center of gravity is positioned on the wheelchair, the greater the force required to tilt the upper module backward and lift the contact element 63 off the ground.

[0062] The control unit 25 can be mounted on the first chassis 21, for example via an elastomer cushion connection device 251, for example a silent block connection device.

[0063] As illustrated in Figures 1 to 3, the control unit 25 includes a control handle 250. The control unit 25 can, for example, be positioned on or at the level of an armrest 240, for example the left armrest of the wheelchair 10.

[0064] According to one embodiment, the first and second modes of operation are activated by exerting the first and second pushes respectively on a part of the first chassis 21, for example on a side post 24 and / or one and / or the other of the armrests 240.

[0065] The control unit 25 includes at least one force sensor 45 configured to detect a force to the left or to the right of the wheelchair 10 (Figure 4). In one embodiment, the force sensor 45 includes a Hall effect sensor with bidirectional sensing capability, for example, in this case, along a left-right direction. The force sensor 45 can also be mounted directly on one of the side posts 24 and / or armrests 240.

[0066] In one embodiment, the wheelchair's motorization system includes a drive motor 221 coupled to each drive wheel 22, for example, mounted in each drive wheel. Incorporating the drive motors 221 into the drive wheels 22 allows, in particular, for a reduction in the number of mechanical parts to be incorporated into the first frame 21. In one embodiment, each drive motor 221 is brushless.

[0067] According to another embodiment, the wheelchair motorization comprises a single drive motor 221 coupled to the two drive wheels 22, for example mounted in or on the first chassis 21.

[0068] The second frame 61 comprises a cross member 66, two side posts 67 each fixed to a respective end of the cross member 66, and a linkage 68 connecting the cross member to the ground contact member 63. The seat 62 can be fixed to the second frame 61, for example, to the side posts 67 or to the cross member 66, for example in an adjustable position along the X axis.

[0069] The ground contact element 63 is configured to move in contact with the ground when the wheelchair 10 moves. The ground contact element 63 may include, but is not limited to, one or two idler wheels, and / or at least one sliding contact element. An idler wheel is a non-driven guide wheel adapted to rotate about an axis parallel to the median plane P1. In the example shown in Figures 1 to 3, the ground contact element 63 has a single idler wheel. The sliding contact element may be a ski or a skate, for example, for movement on sand or snow. A footrest 64 may be provided, for example, attached to the connecting linkage 68, on either side of the single idler wheel or between the two idler wheels.

[0070] According to one embodiment, the first frame 21 comprises a rectangular base 23 and one or two side posts 24 extending on each side of the wheelchair 10. The side posts 24 can be fixed to the base 23, and on either side of the armrests 240. In the wheelchair 10 of the illustrated example, the base 23, the side posts 24 and the armrests 240 delimit between themselves an interior space which accommodates the upper module 60 (figure 1).

[0071] The side uprights 24 may, for example, include, but are not limited to, solid panels, perforated panels, and / or tubular structures. One of the side uprights 24 may support the control unit 25. The drive wheels 22 may be mounted externally on the base 23 or on the side uprights 24.

[0072] In one embodiment, to pivotally mount the upper module 60 to the lower module 20, the base 23 comprises a pair of cheeks 28, each with a hole into which the pivot 50 with axis of rotation Y2 is engaged. In the examples shown in Figures 1 and 3, the base 23 comprises two pairs of cheeks 28, each pair of cheeks being connected to a lateral support 67 by a respective pivot 50 centered on the axis of rotation Y2. The wheelchair 10 then has two pivots 50, each supported by a pair of cheeks 28 fixed to the base 23. Of course, the upper module 60 can be attached to the frame 21 by a single pivot.

[0073] Figure 4 shows the CSYS 30 control system, according to one embodiment. The control system 30 includes one or more SNS sensors, 45, one or more MEM memories, and an MC control unit connected to the sensors, to each drive motor 221 and to each memory, and an ALM power supply to power each drive motor 221 and the control system 30. The SNS sensors may include, in particular, one or more gyroscopic sensors, one or more accelerometers, and one or more speed sensors.The control system 30 includes at least one sensor configured to detect the change in inclination of the first chassis 21 relative to the horizontal, caused by the application of the control force, the control unit MC being configured to control the motorization 221 in order to generate a non-zero control moment applied to the first chassis 21 allowing the inclination of the first chassis 21 relative to the horizontal to be maintained substantially constant.

[0074] The control system 30 is thus configured to ensure the balancing of the first frame 21, keeping it horizontal. The control torque can be applied to at least one drive wheel 22 by the motor 221. The effect of the control torque on the first frame 21 can, if necessary, be combined, for each drive wheel 22, with the instantaneous rotational speed of the respective drive wheel 22. Thus, depending on the instantaneous rotational speed of the drive wheels 22 and the direction of the control torque, the application of the control torque can result in acceleration, stabilization, or braking of the wheelchair 10.

[0075] The ALM power source can include one or more batteries, for example a Li-ion battery. Other types of power sources are also possible.

[0076] The base 23 may include a watertight housing 29, notably to house the ALM power supply, the control system 30 being for example housed in one of the armrests 240. The MC control unit may include a microprocessor or a microcontroller.

[0077] The control system 30 can be configured to implement a method for using the wheelchair 10. This method may include:

[0078] - an operating stage in the first operating mode, during which the wheelchair 10 rests on the ground on the two drive wheels 22 and on the ground contact member 63; and - an operating stage in the second operating mode, during which the wheelchair 10 rests on the ground on the two drive wheels 22, the ground contact member 63 being raised relative to the ground.

[0079] Wheelchair 10 is configured as follows:

[0080] - to switch from the first operating mode to the second operating mode, when the user exerts a forward push on the control unit 25 or an armrest 240, in the direction X and with an intensity greater than the thrust threshold value, and

[0081] - to switch from the second operating mode to the first operating mode when the user releases the control element 25, 240 or exerts a reverse push on it, to reach a push force having an intensity lower than the push threshold value.

[0082] According to an embodiment illustrated in Figure 5, the position of the rotation axis Y2 is adjustable along the X direction to adjust the tilting capacity of the upper module 60 forwards or backwards, particularly depending on the slope of the ground PO. For this purpose, the side panels 28 can be fixed to the base 23 by slides 27 oriented along the X direction and coupled to an actuator 26 allowing adjustment of the position of the side panels in the slides. The motor is connected to a control unit 31, for example, located on one of the armrests 240 so that it can be operated by the user seated on the seat 62. The control system 30 is then configured to control the actuator 26 according to the commands transmitted by the user via the control unit 31.

[0083] Figures 6 to 8 depict a motorized wheelchair 10' according to another embodiment. The wheelchair 10' differs from the wheelchair 10 essentially in that it includes a braking device comprising movable, for example, pivoting, brake elements 71. The brake elements 71 are arranged to be able to clamp against one of the drive wheels 22, in particular to lock the wheels when the wheelchair is stationary. Thus, each of the brake elements 71 comprises a retracted position in which the drive wheel can rotate freely and a deployed position in which the drive wheel is locked to rotate.

[0084] To support the brake elements 71, the second frame 61 of the upper module 60 of the wheelchair is modified by adding, for example, a crossbar 70 which can be attached to the connecting linkage 68, the brake elements 71 being pivotally mounted at each end of the crossbar 70. In the example shown in Figures 1 to 3, the first frame 21 (lower module 20) includes, on each side of the seat 62, two lateral uprights 24 fixed to the base 23 and connected to each other at the top by one of the armrests 240. In the example shown in Figures 6 to 8, the first frame 21 includes a single lateral upright 24' in a rear position, connected to one of the armrests 240, to allow passage of the bar 70. Note that the wheelchair may be equipped with only one brake element 71 to lock a single drive wheel 22.

[0085] It will be readily apparent to those skilled in the art that the present invention is susceptible to various embodiments and applications. In particular, it is not necessary for the lower module 20, or the first frame 21, to be kept horizontal along the X direction. Indeed, it is only important that the inclination of the lower module 20 relative to the horizontal along the X direction be kept constant, or rather, controlled to remain constant by the control unit 30.

[0086] Other structures can easily be imagined for the upper 60 and lower 20 modules. Thus, it is not necessary for these modules to be designed around a chassis.

Claims

DEMANDS 1. Motorized wheelchair (10) comprising: a lower module (20); a pair of drive wheels (22) mounted on the lower module; a motorization (221) configured to drive the pair of drive wheels in rotation; an upper module (60) comprising a seat (62) and a ground contact member (63), the upper module being mounted articulated with the lower module by a pivot (50), to pivot relative to each other around the pivot under the effect of a control force exerted on the lower module by a user seated on the seat; and a control unit configured to detect a change in inclination of the lower module relative to the horizontal caused by the control force, and to generate a control torque using the motorization on at least one of the drive wheels in order to restore an initial inclination of the lower module.

2. Wheelchair according to claim 1, wherein each of the drive wheels (22) is mobile in rotation about an axis of rotation (Y1a, Y1b) passing through a center of the drive wheel, the axes of rotation of the drive wheels and an axis of rotation (Y2) of the pivot (50) being parallel to each other to within a few degrees at most.

3. Wheelchair according to claim 2, wherein: the axis of rotation (Y2) of the pivot (50) is located at a distance (D) less than or equal to 30 mm from the axis of rotation (Y1a, Y1b) of each drive wheel (22); and / or the axis of rotation of each drive wheel and the axis of rotation of the pivot are located in the same frontal plane (P2) when the ground contact member (63) and the drive wheels (22) are in contact with a flat surface (PO), the frontal plane extending perpendicularly to a direction (X) of rear-to-front movement of the wheelchair (10); and / or the axis of rotation (Y2) of the pivot (50) coincides with the axis of rotation (Y1) of each drive wheel; and / or the axis of rotation (Y2) of the pivot (50) is arranged under the axis of rotation (Y1) of the drive wheels in the frontal plane (P2).

4. Wheelchair according to any one of claims 1 to 3, wherein the control unit (30) is configured to control the wheel drive (221) to maintain the lower module (20) substantially horizontal, in a direction (X) towards the front or rear of the wheelchair (10).

5. Wheelchair according to any one of claims 1 to 4, wherein the control unit (30) is configured to control the wheel drive (221): according to a first operating mode in which the wheelchair (10) is in contact with the ground (PO) on both drive wheels (22) and on the ground contact member (63); and according to a second mode of operation in which the wheelchair is in contact with the ground on only the two drive wheels, the ground contact element being in a raised position relative to the ground.

6. Wheelchair according to claim 5, comprising a control member (25, 240) coupled to the control unit (30), the control member (30) being configured to control the control unit in order to control the motorization (221) of the wheels to keep fixed or move the wheelchair (10) in a direction (X) forwards or backwards, to switch to the first operating mode when the user exerts a forward thrust on the control device, with an intensity lower than a threshold thrust value; and switch to the second operating mode when the user exerts a forward thrust on the control element, with an intensity greater than the thrust threshold value.

7. Wheelchair according to claim 6, wherein: The control unit (25) is mounted on a first chassis (21) of the lower module (20) via an elastomer cushion connection device (251); and / or the control unit is formed by a part (24, 240) of the first chassis.

8. Wheelchair according to any one of claims 6 and 7, wherein the control member (25) comprises at least one force sensor (45) arranged to detect a directional instruction to the left and / or to the right of the wheelchair (10), the control unit (30) being configured to control the motorization (221) of the wheels according to the directional instruction.

9. Wheelchair according to any one of claims 1 to 8, wherein the drive wheel (221) motorization comprises: a respective drive motor (221) coupled to each drive wheel (22); or a single drive motor mounted in the lower module (20) and coupled to both drive wheels.

10. Wheelchair according to any one of claims 1 to 9, wherein the ground contact member (63) comprises at least one idler wheel, and / or at least one sliding contact member.

11. Wheelchair according to any one of claims 1 to 10, wherein the pivot (50) is coupled to the lower module (20) so as to be movable along a rear-to-front direction (X) of movement of the wheelchair (10), the control unit (30) being configured to control an actuator (26) in order to adjust the position of the pivot (50) along the rear-to-front direction of movement in response to a command applied to a control member (31) by the user.

12. Wheelchair according to any one of claims 1 to 11, comprising a braking device (71) arranged to cooperate with at least one of the drive wheels (22) and comprising a retracted position in which the drive wheel can rotate freely and a deployed position in which the drive wheel is locked in rotation.

13. Wheelchair according to any one of claims 1 to 12, wherein the braking device is fixed to the upper module (60) and / or includes a braking element (71) arranged to cooperate with each of the drive wheels (22).

14. Method of using the wheelchair (10) according to any one of claims 1 to 13, the method of use comprising: a first mode of operation in which the wheelchair is fixed or moves on the ground (PO), on the two drive wheels (22) and on the ground contact element (63); a second operating mode in which the wheelchair is fixed or moves on the ground on its two drive wheels (22), the ground contact element (63) being raised relative to the ground; and steps consisting of: activate the second operating mode from the first operating mode, under the effect of a pushing force exerted by the user on the control unit (25, 240), directed towards the front (X) of the wheelchair and having an intensity greater than a threshold pushing value; and activate the first operating mode from the second operating mode, when the user releases the control element or exerts a reverse thrust on it, to achieve a thrust force with an intensity lower than the thrust threshold value.

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