WO2021074525A1

WO2021074525A1 - Method for controlling an electrical assistance device

Info

Publication number: WO2021074525A1
Application number: PCT/FR2020/051818
Authority: WO
Inventors: Thomas PASUTTO
Original assignee: Electricite De France
Priority date: 2019-10-14
Filing date: 2020-10-14
Publication date: 2021-04-22
Also published as: FR3101771B1; FR3101771A1

Abstract

The present invention relates to a method for controlling an electrical assistance device (1) for a human-powered vehicle, the electrical assistance device (1) comprising at least one motor (2) for supplementing the human power. The method comprises at least the following steps: (a) acquiring the rotation speed (ω) of the one or of each motor (2); (b) determining one or more physical quantities on the basis of the acquisition of step (a); (c) controlling the one or each motor (2), as a function of the determination of step (b), between at least one operating state of the electrical assistance, in which the electrical assistance supplements the human power, and at least one shutdown state of the electrical assistance, in which only the human power can move the device.

Description

Control method of an electrical assistance device

FIELD OF THE INVENTION

The present invention relates to the field of mobility for disabled people, and more particularly relates to a control method for an electric assistance device for a wheelchair.

STATE OF THE ART

In general, we know of two types of wheelchairs. On the one hand, fully manual wheelchairs, which typically feature two large rear wheels and two small front wheels. The front wheels are movable in rotation around a transverse axis and the rear wheels are locked in rotation around the same transverse axis.

Most often, an annular handle is arranged on the side of each rear wheel. The propulsion and guidance of the chair is provided either by the user using the ring handles to turn the rear wheels, or by a third person pushing the chair.

A second type of known wheelchairs are motorized chairs.

These chairs are often much more massive and heavier than manual chairs. Traditionally, these chairs include four or six wheels, of reduced diameter compared to the rear wheels of a manual chair. In addition, the chair incorporates electric motors, large batteries and a guidance system. In fact, known motorized chairs can only be operated with a guidance system. Most often, it is a handle of the "joystick" type. This arrangement makes the wheelchair particularly useful in the case of a multiple handicap, but prohibits any manual maneuver. In addition, since the wheelchair can only move with the force of the motors, it is necessary to have large capacity batteries, which weighs down the wheelchair enormously.

A third, less common type of wheelchair concerns manual wheelchairs transformed into electric wheelchairs.

Thus, for example, manual chairs are known in which a motor is integrated in the hub of each rear wheel. The motor is an electric assist motor. This means that the motors alone do not move the chair, but they provide additional force requiring less effort from the user.

The control of the chair is always carried out with the ring handles. This solution is particularly advantageous because it provides assistance when the user is climbing, for example, or to avoid fatigue over long distances.

However, this solution can only be used on a wheelchair specifically adapted for. In other words, this solution is not adaptable to every manual wheelchair.

Another solution for motorizing a manual wheelchair consists of adding a device with a motorized wheel to the wheelchair. Most often, this device takes the form of a front wheel, with a handlebar. The device is then attached to the front of the chair. The handlebars work like a motorcycle handlebar with one rotating handle to control engine speed, and another handle, to brake. This device is not an assistance system, but a complete motorization system. Thus, the user no longer uses his arms to move and orient the chair. In the event of a breakdown, as with a standard power chair, it is impossible for the user to move the chair.

Patent application FR 1901231 describes an electric assistance device for a wheelchair which comprises at least one motor having a rotor connected to a toothed pinion adapted to engage a complementary toothing of a tire of a wheel of the wheelchair, which does not have the disadvantages of the prior art. DISCLOSURE OF THE INVENTION

The present invention aims to provide a method for controlling an electric assistance device for a human-powered vehicle. The electrical assistance device includes at least one motor to supplement human propulsion. The method comprises at least the following steps:

(a) acquisition of the speed of rotation of the or each motor;

(b) determination of one or more physical quantities from the acquisition of step (a);

(c) control of the or each motor as a function of the determination of step (b), between at least one operating state of the electric assistance in which the electric assistance supplements the human propulsion and at least one state of 'extinction of the electric assistance in which only human propulsion can move the device.

The method may include a step (a ’) of acquiring inertial data by inertial acquisition means of the device.

The, or each, physical quantity determined in step (b) can be chosen from: a speed of the device, an acceleration of the device and / or an inclination of the device, and / or a speed difference between the left and right wheels . Step (c) can comprise the comparison of a speed of the device determined in step (b) with a first speed threshold value called the tripping speed, if the speed of the device is greater than or equal to the tripping speed , then step (c) includes setting electric voltage of, or of each, motor, to position the device in the operating state of the electric assistance.

Step (c) can comprise the comparison of a speed of the device determined in step (b) with a second speed threshold value called the stopping speed, if the speed of the device is greater than or equal to the speed d 'stopping, then step (c) comprises the gradual decrease or increase of a setpoint of the motor (s) in order to stabilize the speed of the device, or the electrical de-energization of the or each motor, for position the device in the state of extinction of the electric assistance.

Step (c) can comprise the comparison of an inclination of the device determined in step (b) with a first inclination threshold value called the trigger inclination, if the inclination of the device is greater than or equal to the trigger tilt, then step (c) may include energizing the, or each, motor to position the device in the electric assist operating state, or step (c) may include increasing the electrical voltage delivered to, or to each, motor to position the device in a state of boosting electrical assistance.

Step (c) can comprise the comparison of an inclination of the device determined in step (b) with a second threshold value of inclination, called the stop inclination, if the inclination of the device is greater than or equal to inclination of stop, then step (c) comprises the electrical de-energization of the, or each, motor, to position the device in the state of extinction of the electric assistance.

According to a second aspect, the invention relates to an electric assistance device for a wheelchair, adapted to implement a method according to the invention, comprising at least one motor having a rotor connected to a toothed pinion adapted to engage a set of teeth. complementary to a tire of a wheel of a wheelchair. The device comprises at least one controller suitable for measuring the speed of rotation of said at least one motor and at least one control member adapted to control said at least one motor.

The controller can be adapted to transmit to said at least one motor a control instruction sent by said at least one control member. The electrical assistance device may include an inertial unit.

The controller may be a computer suitable for carrying out the method according to the invention.

According to another aspect, the invention relates to a wheelchair comprising two rear wheels each having a tire having toothing. The wheelchair comprises at least one electric assistance device according to the invention.

The wheelchair may include a seat, the controller and the inertial unit being able to be fixed under the seat. According to another aspect, the invention relates to a computer program product comprising code instructions for carrying out a method according to the invention, when executed by a computer.

According to another aspect, the invention relates to a storage means readable by computer equipment on which a computer program product comprises code instructions for the execution of a method according to the invention.

DESCRIPTION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which should be read with reference to the appended drawings in which: FIG. 1 is a partial representation, in perspective , of a wheelchair provided with an electric assistance device according to the invention, in the transport position.

FIG. 2 is a partial representation, in perspective, of a wheelchair provided with an electric assistance device according to the invention, in the transport position, from another angle of view.

Figure 3 is a representation of an open housing containing controllers and a control member according to the invention.

Figure 4 is a representation of a closed housing containing controllers and a control member according to the invention. Figure 5 is a representation of a control box attached to the seat of a wheelchair.

Figure 6 is a diagram of a wheelchair according to the invention facing a slope.

FIG. 7 is a block diagram of a method for controlling an electric assistance device according to the invention.

In all of the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the invention relates to a method of controlling an electric assist device for a human powered vehicle. By human propulsion, it is understood a propulsion resulting from an effort of the human body. Thus, the vehicle can for example be a scooter, a bicycle, or a wheelchair as will be described below.

Electrical assistance device

The electrical assistance device includes at least one motor to supplement human propulsion,

The electrical assistance device 1 comprises in particular a motor 2, a pinion 4 and an arm 6.

More particularly, as can be seen in Figures 1 and 2, the electric assistance device 1 comprises a preferably electric motor 2. The motor 2 has a rotor 22 and a stator 21. According to the embodiment presented here, it is a motor 2 of the motor 2 type with an outer rotor 22. It could be an alternative to a more conventional motor 2 with internal rotor 22.

The rotor 22 is connected to the pinion 4. The rotor 22 is mounted on the stator 21 by means of ball bearings. Pinion 4 is driven directly by rotor 22. Alternatively, it can be driven by rotor 22 via a freewheel.

The pinion 4 is intended to cooperate with a tire 110 of a wheel 104, 105 of the wheelchair 100, ie to come into contact with a tread 110a or, preferably, a sidewall 110b of this tire 110, so to be able to transmit to it a force making it possible to set the tire 110 in rotation and move the wheelchair 100. The pinion is toothed, that is to say it is not smooth and has toothing, in other words a plurality of projecting elements improving the contact and friction between the pinion 4 and the tire. 110. As will be seen, the tire 110 is also cleverly toothed in a complementary manner, ie so as to be able to mesh with the toothing of the pinion 4. It is then understood that the force is transmitted much more efficiently directly by pressing the toothings. , and not by simple friction. Thus, preferably, in the case where the vehicle is a wheelchair 100, at least one of the sidewalls 110b, 110c of the tire 110

(preferably a so-called "internal" flank 110b because the wheel 104, 105 is often provided with an annular handle 106 on the side of the other so-called outer flank 110c, see below) has the toothing (not shown), which allows to keep a pattern on the tread 110a for good adhesion to the ground of the tire 110.

Alternatively, it is possible to use straight, helical or even herringbone teeth.

It is specified that in the case of helical or chevron toothing, at least one of the sidewalls of each tire 110, in particular the internal sidewall 110b may have toothing. Thus each tire 110 has teeth on at least one side and can equally well be used for a right wheel 104 or a left wheel 105 of the wheelchair 100, without being constrained by the particular geometry of the teeth when the latter has a symmetrical profile. In the first embodiment illustrated in FIGS. 1 to 4, identical tires 110 are used, each comprising a helical toothing with a symmetrical profile on an internal flank 110b, which toothing cooperates with identical pinions 4 (it is understood that they have identical toothings) arranged one from the right rear wheel 104 side and one from the left rear wheel 105 of the wheelchair 100.

Whatever the embodiment chosen (straight, helical or chevron toothing), it is preferable to use symmetrical toothing. By toothing symmetrical, it is understood, a toothing allowing the engagement and transmission of a force, whatever the direction of rotation of the pinion 4 (as opposed to an asymmetrical toothing in which a single direction of rotation of the pinion 4 would allow the transmission effort).

Advantageously, the teeth have a pitch of between 1 and 4 millimeters. In a particularly advantageous manner, the toothing has a pitch of approximately 3 millimeters, which makes it possible to have an optimal transmissible torque for a reduced noise level.

Pinion 4 is preferably made of metal, for example steel by superimposing stamped sheets with a thickness of between 0.5 and 2 mm or by milling.

The toothing of the sidewall 110b, 110c of the tire is preferably made of a rubber mixture with a Shore A hardness of preferably between 55 and 95 and even more preferably between 75 and 95 to promote the value of the driving force transmissible by the engine. . The toothing is molded at the same time as the tire 110 or else it can be attached to a tire 110 previously molded.

The motor 2 is connected to the wheelchair by the mobile arm 6.

As will be detailed, according to the embodiment presented here, the mobile arm 6 makes it possible to maneuver the motor between three positions, an engaged position in which the toothing of the pinion 4 is in contact (ie meshed) with the toothing of the tire 110. (electric assistance is then possible), a disengaged position in which the pinion 4 is not in contact with the tire 110 (ie not meshed with the toothing of the tire 110, in other words - slightly - away from the tire 110) (the wheelchair 100 returns to manual mode) and a transport position in which the pinion 4 is moved away from the tire 110 and retracted under the seat 103. In other words, the arm 6 makes it possible to approach or to move the pinion 4 away from the tire 110. It is remarkable that in the disengaged position, the motor 2 remains close to the wheel 104 or 105, and a fortiori in the disengaged position the pinion 4 is not retracted under the seat 103. In addition, as can be seen on Figures 3 and 4, a proximal portion 63 of the arm 6 fixed to the motor 2 is oriented along an axis substantially parallel to a plane of the rear wheel 104 or 105. This arrangement allows a user to easily position the assistance device electric 1 in the engaged position, if desired. Conversely, in the transport position, the motor is retracted under the seat 103, away from the wheel 104 or 105 (ie in the transport position, the motor 2 is further from the wheel 104 or 105 than in the disengaged position) . In addition, as can be seen in Figures 5 and 6, in the transport position the proximal part 61 of the arm 6 is oriented along an axis substantially perpendicular to the plane of the rear wheel 104 or 105.

The distinct presence of a disengaged position and a transport position is particularly advantageous. Indeed, the disengaged position is particularly practical when driving, the proximity of the motor 2 to the wheel 104 or 105 makes it possible to quickly engage the electric assistance device 1. On the other hand, the disengaged position does not allow the wheelchair 100 to be folded up. The transport position, for its part, allows the wheelchair 100 to be folded up. Thus, these two positions (disengaged position and transport position) are complementary and have different effects. different effects.

The arm 6 comprises a clamp 61 adapted to grip a tube 102 of the wheelchair 100.

The clamp 61 has two half-jaws. The two half-jaws are screwed together. This assembly makes it possible both to be able to fix, at will, the device 1 on a wheelchair 100, while guaranteeing maximum safety. In fact, when the two half-jaws are screwed on, they guarantee reliable holding of the device 1. Command organ

In addition, the electrical assistance device 1 comprises a control member 303 and one or more controllers.

Each controller 302 is suitable for measuring the speed of rotation ω of a corresponding motor 2. Thus, the electrical assistance device 1 comprises as many controllers 302 as there are motors 2.

The control unit 303 is adapted to control the or each motor 2. In other words, as will be detailed below, the control unit 303 is adapted to receive data acquired by the controllers 302, for process these data and issue a command instruction accordingly.

Typically, the controller 303 can be a computer.

As will be described below, each controller 302 is suitable for transmitting to a corresponding motor 2 a control instruction sent by the control unit 303. In other words, the controllers 302 make it possible both to perform measurements and transmit control instructions.

Typically, the controllers 302 can be components for measuring and controlling the voltage and the electric current at the terminals of each motor 2. Thus, by measuring the voltage and the current, it is possible to deduce a rotational speed ω therefrom. of the motor 2, and by acting on the electrical quantities, it is possible to modify the speed of rotation or the torque of the motor 2. In the context of a particular embodiment of the assistance device 1, the torque setpoint of the motor 2 is controlled by a vector control method or FOC (field-oriented control). These methods are well known to those skilled in the art and are not detailed here.

According to a particularly advantageous arrangement, the electric assistance device 1 also comprises inertial acquisition means. which include at least one accelerometer and preferably at least one gyrometer. In a particularly preferential manner, the inertial acquisition means can be an inertial unit 301. Advantageously, this inertial unit can be placed as close as possible to the axis of rotation of the rear wheels of the device 1, and at an equal distance. of the two wheels. This arrangement minimizes the contribution of the accelerations originating from the rotation of the device (forward / backward tilting corresponding to a rotation with respect to the axis of the rear wheels, or change of direction inducing a rotation along the vertical axis). In this particular embodiment, the use of a gyrometer is therefore not essential.

Preferably, the inertial unit 301 comprises an accelerometer using three degrees of freedom and a gyroscope using three other degrees of freedom. The inertial unit 301 makes it possible to determine the acceleration and the inclination A of the device 1. As shown in Figures 3, 4 and 5, the control member 303 and the controllers 302 can advantageously be grouped together in a housing 300. This arrangement advantageously makes it possible to group together in a single protective housing 300 the various electronic elements that can be used. fragile. The housing 300 may have an impact-resistant structure, insulating against any discharges of static electricity and waterproof against splashing water (or other liquids). The housing 300 can for example be made of plastic or composite material.

Wheelchair According to a second aspect, the invention relates to a wheelchair 100 equipped with one or more electric assistance devices 1.

Conventionally, the wheelchair 100 is a known manual wheelchair, comprising a frame made up of a plurality of tubes 102, a seat 103, two rear wheels 104, 105 and two front wheels 107. On the one hand Traditionally, the two rear wheels 104, 105 have a diameter significantly greater than the diameter of the two front wheels 107. The two rear wheels 104, 105 are each provided with an annular handle 106. The annular handles 106 allow a user to propel and steer the wheelchair 100.

In a particularly advantageous manner, each rear wheel 104,105 is provided with a tire 110. Each tire 110 has a tread 110a intended to come into contact with the ground, two sidewalls 110b and 110c, including an internal sidewall 110b (oriented towards the middle of the chair 100 and an outer flank 110c (facing the outside of the chair 100 and on the side of which there is the annular handle 106).

The wheelchair 100 is equipped with at least one electric assistance device 1 adapted to cooperate with at least one wheel 104, 105, in particular the rear wheel 104 right or left 105 (since these are the wheels of larger size. size supporting the majority of the weight of its user, and therefore capable of transmitting a significant traction force to the ground without loss of adhesion between the tire and the ground). By abuse of language, it could be said that at least one wheel 104, 105 of the wheelchair is provided with device 1.

Preferably, the wheelchair 100 is equipped with at least two electric assistance devices 1, ie at least one for each rear wheel 104 and 105, in particular one with the left rear wheel 105 and one with the wheel. rear right 104. Such an embodiment allows more efficient symmetrical propulsion, and even allows the chair 100 to turn, if necessary, by applying different rotational speeds or torques to the left and to the right. We understand that it is still possible to mount several devices 1 on a single wheel, so as to multiply the power.

As explained, said tire 110 of a wheel 104, 105 provided with the device 1 has a toothing complementary to a toothing of the pinion 4 connected to the rotor 22 of said motor 2 of the electric assistance device 1. Advantageously, at least one of the flanks 110b, 110c, and in particular the internal flank 110b, and preferably each of the flanks 110b, 110c, has a symmetrical helical toothing, complementary to the symmetrical helical toothing of the pinion 4. The use of 'symmetrical toothing, whether straight or helical, allows the same type of tire 110 to be used indiscriminately for the right rear wheels 104 or left rear 105, ie a configuration can be provided in which each of the rear wheels 104 is provided with a device 1, while having the same tire 110 (having the symmetrical toothing on each of its sidewalls 110b, 110c).

In another embodiment, use is made of a non-symmetrical toothing (for example of the type as described in the patent application WO2014086727 of the applicant) making it possible to further increase the transmissible torque. However, the use of such an asymmetric toothing requires having a specific left tire and a specific right tire, or else identical tires on the left and on the right, but with toothing on both sidewalls, thus slightly increasing the cost. Manufacturing.

Preferably, each motor 2 is fixed by an arm 6 near each rear wheel 104, 105. So that the pinion 4 connected to each motor 2 can be meshed with the teeth of the tire 110 of the rear wheel 104. , 105 correspondent.

During travel, the arms 6 make it possible to maneuver the pinions 4 between an engaged position in which the pinions 4 are each meshed with a toothing of the corresponding tire 110, and a disengaged position in which the pinions 4 are spaced apart from the tires 110.

In other words, in the engaged position, the pinions 4 are meshed with the tires and the motors 2 can apply a torque to the rear wheels 104, 105. In the disengaged position, the pinions are remote from the tires and the motors 2 cannot. apply no torque to the rear wheels 104, 105. In addition, the arms also make it possible to maneuver the electric assistance devices 1 in the transport position. In this position, the pinions 4 are remote from the tires 110 and are retracted under the seat 103. This arrangement is particularly useful when the wheelchair is placed for example in the boot of a vehicle. By being retracted under the seat 103, the electric assistance devices 1 are less exposed to possible snags, or shocks, which could damage them. In addition, this arrangement is particularly advantageous, in the case of a folding wheelchair 100.

In addition, as shown in FIG. 5, the box 300 and the inertial unit 301 are fixed under the seat 103. This arrangement advantageously makes it possible to protect the on-board electronics from bad weather, and not to modify the balance of the wheelchair too much. 100.

In use, a user can activate the electric assistance by placing the arms 6 in the engaged position. The motors 2 can then be triggered according to the method detailed below, and exert a torque on the rear wheels 104, 105. The force transmitted by the motors 2 will relieve the user who will have less effort to provide to move the chair. rolling 100 with the strength of his arms. It should be noted that the electric assistance alone does not allow the wheelchair 100 to be moved. The potentiometer makes it possible to adjust the power of the electric assistance provided. The user can at any time place the arms 6 in the disengaged or transport position, thus disconnecting the electric assistance. In the disengaged, or transport position, the user moves the wheelchair 100 using only the strength of his arms.

Control process

As stated above, the invention proposes a method for controlling one, or more, electric assistance device 1. The process mainly comprises the following steps:

(a) acquisition of the speed of rotation of the or each motor;

If the assistance device 1 comprises an inertial unit 301, the method may include a step (a ’) of acquiring accelerometric data from the inertial unit 301.

Preferably, the physical quantities determined in step (b) are chosen from: a speed V of the device, an acceleration of the device and / or an inclination A of the device, and / or a difference in speed AV between the devices. left and right wheels if the system has two motors. In a particularly preferential manner, the speed V of the device, the speed difference ΔV, its inclination A and its acceleration are all four determined.

It is specified that by inclination A it is understood orientation of the device 1 in a terrestrial reference mark (X ’, Y’, Z ’). In other words, the inclination A corresponds to the orientation of the proper frame of reference (X, Y, Z) of device 1 with respect to the terrestrial frame of reference (X ’, Y’, Z ’).

The joint use of the acceleration mours from the inertial unit, and of the speed measurements V, ΔV, advantageously make it possible to estimate the components of the gravity field involved in the calculation of the inclination A, by subtracting the accelerations linked to the propulsion or braking of the wheelchair. In a particularly advantageous manner, step (c) comprises the comparison of a speed of the device V determined in step (b) with a first threshold value of speed V1, called the tripping speed V1, if the speed of the device V is greater than or equal to the triggering speed V1, then step (c) comprises the electrical powering of, or each, motor 2, to position the device 1 in the operating state of the assistance electric.

In other words, this arrangement makes it possible to trigger the electric assistance only when the device 1 has reached or exceeded a certain speed. This prevents the assistance from being triggered when stationary or during maneuvering at reduced speed.

In addition, step (c) comprises comparing a speed of the device V determined in step (b) with a second speed threshold value V2 called the stopping speed V2, if the speed of the device is greater or equal to the stopping speed V2, then step (c) comprises the electrical de-energization of, or each, motor 2, in order to position the device 1 in the state of extinction of the electric assistance.

This arrangement makes it possible to switch off the electric assistance as soon as a given speed is reached or exceeded. The motor setpoint can be adjusted gradually (reduction of the setpoint when approaching V2), or binary through an all or nothing command. In other words, this provision makes it possible to restrict the speed of the device 1, to protect the user from a runaway effect and to comply with any regulations relating to the maximum authorized speed for an electrically assisted vehicle.

In addition, step (c) can comprise the comparison of an inclination A of the device determined in step (b) with a first threshold value of inclination A1 called the trigger inclination A1, if the inclination A of the device is greater than or equal to the trigger inclination A1, then step (c) comprises energizing the, or each, motor 2, or step (c) comprises increasing or decreasing the electric voltage supplied to, or each, motor to position the device in a state of boosting the electric assistance.

In other words, this provision relates to the case where the wheelchair 100 is climbing a slope. In this case, there are two options. Either the wheelchair 100 has not reached the triggering speed V1, but the gradient of the slope is such that it is necessary to trigger the electric assistance. Either wheelchair 100 already benefited from electric assistance, but the gradient is such that it is necessary to strengthen the electric assistance (i.e. increase the speed of rotation of motor 2) to relieve the user.

In addition, step (c) can comprise the comparison of an inclination A of the device determined in step (b) with a second threshold value of inclination A2 called the stop inclination A2, if the inclination of the device A is greater than or equal to the stop inclination A2, then step (c) comprises the electrical de-energization of the, or each, motor, to position the device in the state of extinction of the assistance electric.

In other words, this arrangement makes it possible to turn off the electric assistance when the wheelchair 100 descends a slope. This arrangement protects the user from excessive speed when descending.

More precisely, the inclination A is determined as follows: the accelerations communicated to the chair by the user or by the assistance, and corresponding to the accelerations obtained by means of the controllers 302 or of the motors 2, are subtracted from the acceleration measurements from the inertial platform. The data of the components of gravity in the frame of reference (X, Y, Z) of the wheelchair 100, is used to determine the angle a of the road on which the wheelchair rolls and its inclination with respect to the vertical, using of a cosine direction matrix (DCM). In practice, the information coming from the inertial unit 301 deviates from the ideal measurements because of the noises and the errors which affect the measurements (bias, noises, drifts over time of the angular measurements). To limit these errors, well-known filtering methods in signal processing can be implemented. To this end, a filtering technique based on the integration of a differential equation has been implemented within the framework of a particular embodiment. The components of the force of gravity measured in the reference frame of the chair, are introduced as input data of the differential equation [Math. 1]. At the mechanical level, this differential equation can be seen as a damped mass-spring system. It behaves like a resonant filter whose cut-off frequencies and the quality factor depend on the values of the coefficients B and C associated with the restoring force and the damping. The integration of this equation makes it possible to access the quantity y0 which corresponds to the filtered value of the slope on which the chair is located. For adequate values of parameters B and C, integration of the equation provides an estimate of the filtered tilt A. This integration is made in real time by the central unit, by treating the restoring force by means of an explicit Verlet diagram, and by impliciting the contribution of damping so as not to reduce the field of stability of the diagram digital [Maths. 3]. This solution could also be used to determine the roll angle between the chair and the road, but this information was not used in the present embodiment.

[Math. 1].

[Math. 2]

[Maths. 3].

With:: Components of the accelerations measured by the inertial platform ω: Average of the rotation speeds on the 2 wheels of the chair R: Radius of the wheels Δt: No time for integration (identical to the time step of the regulation loop)

B, C: Coefficients defining the behavior of the Angle and angular velocity filter filtered at time t = n Δt

Claims

1. A method of controlling an electric assistance device (1) for a human-powered vehicle, the electric assistance device (1) comprising at least one motor (2) making it possible to supplement the human propulsion, the method being characterized in that it comprises at least the following steps:

(a) acquisition of the speed of rotation (ω) of, or of each motor (2);

(b) determination of one or more physical quantities, including a speed (V) of the device (1), from the acquisition of step (a);

(c) control of the or each motor (2) as a function of the determination of step (b), between at least one operating state of the electric assistance in which the electric assistance complements the human propulsion and at least a state of extinction of the electric assistance in which only human propulsion can move the device, and comparison of a speed of the device determined in step (b) with a second speed threshold value called the stopping speed, if the speed of the device is greater than or equal to the stopping speed, then step (c) comprises the progressive reduction or increase of a set point of the motor (s) (2) in order to stabilize the speed of the device (1), or the electrical de-energization of, or each, motor (2), to position the device (1) in the state of extinction of the electric assistance.

2. A control method according to claim 1, comprising a step (a ’) of inertial data acquisition by inertial acquisition means of the device (1).

3. Control method according to one of claims 1 or 2, wherein one of the physical quantities determined in step (b) can be chosen from: an acceleration of the device (1) and / or an inclination (A ) of the device (1), and / or a speed difference (ΔV) between the left and right wheels.

4. The control method according to claim 3, wherein, step (c) comprises the comparison of a speed (V) of the device determined in step (b) with a first speed threshold value (V1) called. tripping speed (V1), if the speed of the device (1) is greater than or equal to the tripping speed (V1), then step (c) comprises the electrical energization of, or each, motor (2 ), to position the device (1) in the operating state of the electric assistance.

5. Control method according to any one of claims 3 or 4, wherein, step (c) comprises the comparison of an inclination (A) of the device (1) determined in step (b) with a first tilt threshold value (A1) called trigger tilt (A1), if the tilt (A) of the device (1) is greater than or equal to the trigger tilt (A1), then step (c) comprises electrically energizing the, or each, motor (2) to position the device (1) in the operating state of the electric assistance, or step (c) comprises increasing the electric voltage delivered to, or to each, motor (2) to position the device (1) in a state of strengthening of the electric assistance.

6. Control method according to any one of claims 3 to 5, wherein, step (c) comprises the comparison of an inclination (A) of the device determined in step (b) with a second threshold value. inclination (A2), called stop inclination (A2), if the inclination of the device (A) is greater than or equal to the stop inclination (A2), then step (c) comprises setting de-energized from the or each motor (2), to position the device (1) in the state of extinction of the electric assistance.

7. Electric assistance device (1) for a wheelchair (100), adapted to implement a method according to any one of claims 1 to 6, comprising at least one motor (2) having a rotor (22) connected to a toothed pinion (4) suitable for meshing a toothing (111) complementary to a tire (110) of a wheel (104, 105) of a wheelchair (100), the device being characterized in that it comprises at least one controller (302) adapted to measure the speed of rotation of said at least one motor (2) and at least one control member (303) adapted to drive said at least one motor (2).

8. Electrical assistance device (1) according to claim 7, characterized in that the controller (302) is adapted to transmit to said at least one motor (2) a control instruction sent by said at least one control member ( 303).

9. Electrical assistance device (1) according to any one of claims 7 or 8, comprising an inertial unit (301).

10. Electrical assistance device (1) according to any one of claims 7 to 9, wherein the controller (303) is a computer adapted to carry out the method according to any one of claims 1 to 7.

11. Wheelchair (100) comprising two rear wheels (104, 105) each having a tire (110) having a toothing (111), characterized in that it comprises at least one electric assistance device (1) according to the any of claims 8 to 11.

12. Wheelchair (100) according to claims 11 and 9 in combination, comprising a seat (103), the control member (303) and the inertial unit (301) being fixed under the seat (103).

13. A computer program product comprising code instructions for executing a method according to any one of claims 1 to 6, when executed by a computer.

14. Storage medium readable by computer equipment on which a computer program product comprises code instructions for the execution of a method according to one of claims 1 to 6.