WO2022258920A1

WO2022258920A1 - Method for controlling an electrical assistance device

Info

Publication number: WO2022258920A1
Application number: PCT/FR2022/051082
Authority: WO
Inventors: Yohan WANDERLOID; Thomas PASUTTO
Original assignee: Electricite De France
Priority date: 2021-06-08
Filing date: 2022-06-08
Publication date: 2022-12-15
Also published as: FR3123562A1; CA3222544A1

Abstract

The present invention relates to a method for controlling an electrical assistance device (1) for a human-powered vehicle (100), the electrical assistance device (1) comprising at least one motor (2) for supplementing the human power, and comprising inertial acquisition means. The method comprises at least the following steps: (a) the acquisition of physical parameters from the at least one motor (2), these parameters including a rotational speed (ω) and a torque; (b) the obtaining of one or more physical parameters of the device (1), these parameters including at least an acceleration (A) and an inclination; (e) the estimation of an effort (Fut) applied by a user of the device (1), using the torque of the at least one motor (2), the acceleration (A) of the device (1) and the inclination of the device (1); (f) the determination of a phase of movement, at least as a function of the estimated effort, and the operation of the at least one motor (2), at least according to the phase of movement determined, the phase of movement being determined from among an acceleration phase, a cruising phase or a deceleration phase, between at least a state of operation of the electrical assistance device, in which the electrical assistance device supplements the human propulsion, and at least a state in which the at least one motor (2) is switched off, in which state the device (1) can be propelled by human propulsion alone.

Description

Title: Method for controlling an electric assistance device

FIELD OF THE INVENTION

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

STATE OF THE ART

In general, two types of wheelchairs are known. On the one hand, fully manual wheelchairs, which conventionally have two large rear wheels and two small front wheels. The front wheels are mobile in rotation around a transverse axis and the rear wheels are locked in rotation around this same transverse axis.

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

A second type of known wheelchairs are motorized wheelchairs.

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

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

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

The control of the wheelchair is always carried out with the ring handles. This solution is particularly advantageous because it provides assistance when the user is uphill 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 any manual wheelchair.

Another solution, to motorize a manual wheelchair, consists in adding to the wheelchair a device with a motorized wheel. Most often, this device takes the form of a front wheel, with a handlebar. The device is then attached to the front of the wheelchair. The handlebar functions like a motorcycle handlebar with a 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 motorized 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 mesh with complementary teeth of a tire of a wheel of the wheelchair, which does not have the disadvantages of the prior art.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to propose a method for controlling an electric assistance device for a human-powered vehicle.

According to a first aspect, the invention proposes a method for controlling an electric assistance device for a human-powered vehicle, the electric assistance device comprising at least one motor making it possible to supplement the human propulsion and comprising means of inertial acquisition, the method being characterized in that it comprises at least the following steps:

(a) acquisition of physical quantities of the at least one motor, including a speed of rotation and a torque;

(b) obtaining one or more physical quantities of the device, including at least an acceleration and an inclination;

(e) estimation of an effort of a user of the device, from the torque of the at least one motor, the acceleration of the device and the inclination of the device;

(f) determination of a movement phase at least as a function of the estimated effort and control of the at least one motor, at least as a function of the determined movement phase, the movement phase being determined from among a phase d acceleration, a cruising phase, or a deceleration phase, between at least one operating state of the electric assistance in which the electric assistance completes the human propulsion and at least one extinction state of the at least one motor in which only human propulsion can move the device. Thus, the method according to the invention makes it possible to adapt the electric assistance to the efforts of a user of the human-powered vehicle.

The method may comprise a step (d) of estimating a level of roughness of a ground on which the vehicle comprising the device is running.

The estimation of the roughness of step (d) can be carried out according to vibrations generated by rolling of the vehicle on the ground.

The estimation of the roughness of step (d) can be carried out according to the determination of a variation of a vertical component of the acceleration caused by vibrations generated by the rolling of the vehicle on the ground.

Step (d) may include estimating friction based on the roughness estimate from step (d).

The friction estimate may include a correction of the friction estimate by integration and/or linear regression.

The effort of the user in step (e) can be expressed as a sum of terms including at least the inclination of the device, the torque of the at least one motor and the acceleration of the device.

The sum expressing the effort of the user can also include the estimated friction.

If a speed of the device is greater than a first speed threshold and if the force level is greater than a first force threshold value, then it can be determined that the user is in the acceleration phase and the step (f) may include electrically energizing the at least one motor to place the device in the power assist operating state, or step (f) may include increasing the electrical voltage delivered to the at least one motor to position the device in a state of reinforcement of the electric assistance. If the speed of the device is greater than a first speed threshold and if the estimated force is less than a second force threshold value, then it can be detected that the user is in the deceleration phase and the step ( f) may comprise the electrical de-energization of the at least one motor, to position the device in the state of extinction of the at least one motor.

If the speed of the device is greater than a first speed threshold and if the estimated force is between a first force threshold value and a second force threshold value, then it can be determined that the user is in the cruising phase, and step (f) can comprise the variation or the maintenance of a setpoint of the at least one motor to maintain the device at a speed substantially equivalent to a speed acquired in step (b) or at a preset speed.

If different forces are estimated on each wheel and the difference in absolute value of these forces is greater than a third force threshold, and each force can be estimated is greater than a second force threshold, then it can be determined that the user is in the turn phase.

Step (f) may comprise the electrical de-energization of the at least one motor, to position the device in the state of extinction of the at least one motor.

Step (f) may comprise the application of a current differential to two respective motors, the current differential being proportional to a rotational speed difference between the two motors.

If the absolute value of the difference in the rotational speeds of each motor is less than a second speed threshold value and the level of effort is greater than the second level of effort, then it can be determined that the turn phase is finished. Step (f) may include the comparison of a speed of the device determined in step (b) with a third speed threshold value called the trigger speed.

If the speed of the device is greater than the trigger speed, then step (f) may comprise the progressive increase of a setpoint of the at least one motor until the speed of the device reaches a value of cruising speed threshold, then, step (f) can comprise the stabilization of a setpoint of the at least one motor to maintain the speed of the device substantially equal to the cruising speed threshold value.

According to a second aspect, the invention relates to an electric assistance device for a human-powered vehicle, configured to implement a method according to the invention, comprising at least one motor having a rotor connected to a pinion rubbing on a tire of a wheel of a vehicle and comprising inertial acquisition means, 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 suitable for controlling said at least a motor.

The controller can be adapted to transmit to said at least one motor a control setpoint transmitted by said at least one control member.

The electrical assistance device may comprise an inertial unit.

The control unit may be a computer adapted to execute the method according to the invention.

The human-powered vehicle can be a wheelchair comprising two rear wheels each having a tire, and comprising at least one electric assistance device according to the invention. The wheelchair comprising a seat and a chassis comprising a structure, the control member and the inertial unit can be fixed under the seat or integrated into the structure of the chassis.

According to another aspect, the invention relates to a computer program product comprising code instructions for the execution of a method according to the invention, when it is executed by a computer.

According to another aspect, the invention relates to 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, objects and advantages of the invention will become apparent from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended drawings in which: FIG. 1 is a partial representation, in perspective , a wheelchair fitted with an electric assistance device according to the invention, in the transport position.

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

FIG. 3 is a representation of an open box containing controllers and a piloting device according to the invention.

Figure 4 is a representation of a closed box containing controllers and a control device according to the invention. Figure 5 is a representation of a control box fixed under 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.

FIG. 8 is a block diagram of step (f) according to a first mode of operation.

FIG. 9 is a block diagram of step (f) according to a second mode of operation. In all the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

According to one aspect, the invention relates to a method of controlling an electric assistance 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.

Electric assistance device

The electric assistance device comprises at least one motor making it possible to supplement human propulsion,

The electric assistance device 1 notably comprises 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 motor 2, preferably electric. 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 external rotor 22. It could be an alternative to a more conventional 2 motor with an internal 22 rotor.

Rotor 22 is connected to pinion 4. Rotor 22 is mounted on stator 21 using 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, i.e. 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 rotate the tire 110 and move the wheelchair 100.

The pinion 4 may be toothed (that is to say it is not smooth and has a toothing, in other words a plurality of protruding elements improving the contact and the friction between the pinion 4 and the tire 110), smooth or can present a rough surface (by rough surface, it is understood a surface having a plurality of asperities increasing the friction between the pinion 4 and the tire 110 ). As will be seen, the tire 110 can also be cleverly toothed (so as to be able to mesh with the toothing of the pinion 4) in a complementary or smooth manner or can have a complementary rough surface. It is then understood that the force is transmitted much more effectively directly by support of the teeth or by 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 external flank 110c, see below) has the toothing (not shown) or the rough surface , which makes it possible to keep on the tread 110a a sculpture for a good grip on the ground of the tire 110.

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

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

The motor 2 is connected to the wheelchair by the mobile arm 6. As will be detailed, according to the embodiment presented here, the movable arm 6 makes it possible to maneuver the motor between three positions, a engaged position in which the toothing of the pinion 4 is in contact (ie meshed) with the toothing of the tire 110 (electrical 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 chair 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 move pinion 4 away from 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 be able 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 (i.e. in the transport position, the motor 2 is farther 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. In fact, 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 to be folded 100. The transport position, on the other hand, makes it possible to fold the wheelchair 100. Thus, these two positions (disengaged position and transport position) are complementary and have different effects.

The arm 6 is fixed to the structure of the wheelchair using for example a clamp 61 adapted to hook onto the structure of the wheelchair 100.

The clamp 61 has two half-jaws. The two jaw halves are screwed together. This assembly allows 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 .

Control unit

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

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

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

Typically, 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 setpoint issued by the control unit 303. In other words, the controllers 302 allow both to perform measurements and transmit command 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 therefrom a speed of rotation ω 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 other words, the controllers 302 make it possible to control the speed of rotation and the torque developed by the or the engines. At the same time, they allow access to the torque and speed information of the motor(s).

In the rest of the text, the term speed of the motor (or motors) will be understood to mean the linear speed measured at the level of the motors but related to the wheel in m/s; said linear speed is equal to the linear speed of the wheels when there is no slipping phenomenon in the transmission at pinion level, or at ground level, in this case said linear speed is the speed of the wheelchair relative on the ground.

The assistance supports the user by acting on the torque developed by the motor(s). It is possible to modify the torque of 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 electrical assistance device 1 also comprises inertial acquisition means which comprise at least one accelerometer and preferably at least one gyrometer and one magnetometer. In a particularly preferential way, 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 equal distance of two wheels. This arrangement minimizes the contribution of accelerations coming from the rotation of the device (forward/backward tilting corresponding to a rotation relative 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. Nevertheless, the gyrometer is an advantageous arrangement which makes it possible to gain in precision more particularly on the detection of the angle that the wheelchair makes with respect to the horizontal.

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 unit 303 and the controllers 302 can advantageously be grouped together in a box 300. This arrangement advantageously makes it possible to group together in a single protective box 300 the various electronic elements that can be fragile. The box 300 may have a shock-resistant structure, isolating any discharges of static electricity and impermeable to splashing water (or other liquids). The box 300 can for example be made of plastic or composite material. According to a particularly advantageous arrangement, the box 300 can be miniaturized to be integrated into the chair frame.

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. traditional, the two rear wheels 104, 105 have a diameter much greater than the diameter of the two front wheels 107. The two rear wheels 104,105 are each provided with a ring handle 106. The ring handles 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 flanks 110b and 110c, of which an internal flank 110b (oriented towards the middle of the chair 100 and an outer side 110c (oriented towards the outside of the chair 100 and on the side of which there is the annular handle 106).

The chair 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 wheels of greater size supporting the majority of the weight of its user, and therefore capable of transmitting a significant tractive effort to the ground without loss of grip between the tire and the ground). By misuse of language, we can say that at least one wheel 104, 105 of the wheelchair is provided with the device 1.

Preferably, the wheelchair 100 is equipped with at least two electric assistance devices 1, i.e. 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 a more efficient symmetrical propulsion, and even allows, if necessary, to rotate the chair 100 by applying different speeds or rotational torques to the left and to the right. In other words, this embodiment makes it possible to provide uniform assistance in a straight line while allowing assistance during turns. It is understood that it remains 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 or a complementary rough band of the pinion 4 connected to the rotor 22 of the said motor 2 of the electric assistance device 1

Advantageously, at least one of the flanks 110b, 110c, and in particular the inner flank 110b, and preferably each of the flanks 110b, 110c, has symmetrical helical toothing, complementary to the symmetrical helical toothing of pinion 4, or has a band rough. The use of symmetrical toothing, whether straight or helical, makes it possible to use the same type of tire 110 indiscriminately for the right rear 104 or left rear 105 wheels, i.e. 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 (presenting the symmetrical toothing on each of its sides 110b, 110c).

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

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

When driving, 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 at a distance 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 electrical assistance devices 1 into the transport position. In this position, the sprockets 4 are away 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 trunk of a vehicle. By being retracted under the seat 103, the electrical assistance devices 1 are less exposed to possible collisions, or shocks, which could damage them. In addition, this arrangement is particularly advantageous in the case of a foldable wheelchair 100.

In addition, as shown in Figure 5, the housing 300 and the inertial unit 301 are fixed under the seat 103. This arrangement advantageously protects the on-board electronics from bad weather, and does not change the balance of the chair 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 by the strength of his arms. 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 solely by the force of his arms. Control process

As stated above, the invention proposes a method for controlling one or more electrical assistance device 1 for a human-powered vehicle. The process mainly comprises the following steps (which will be detailed below):

(a) acquisition of physical quantities of the motors 2 including a speed of rotation w and a torque;

(b) obtaining one or more physical quantities of the device 1, including at least one acceleration A and one inclination;

(e) estimation of an effort of a user of the device 1, from the torque of the at least one motor 2, the acceleration A of the device 1 and the inclination of the device 1, to determine whether a vehicle user is accelerating, cruising, or decelerating; (f) control of the at least one motor 2, as a function of the determined acceleration or deceleration phase and as a function of a force estimated in step (e), 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 motors 2 in which only the human propulsion can move the device.

Thus, as will be detailed below, the method uses physical quantities of motors 2 (speed and torque) and physical quantities of device 1 to estimate user effort. Then, the estimated effort is used to control the motors 2. The estimation of a user's effort and its use to control the motors 2 is a particularly ingenious provision of the invention which makes it possible to make the electric assistance as efficient as possible for the user. Indeed, unlike the known devices in which the electric assistance is only a function of the speed or the acceleration), with the method according to the invention the assistance is as close as possible to the needs of a user. Indeed, as will be detailed below, in the case for example where the vehicle (wheelchair 100) rolls uphill on particularly rough ground. In this case, the wheelchair 100 will have a low speed and a low acceleration while the user must exert a lot of effort. In this example, the method according to the invention makes it possible to implement electrical assistance adapted to the efforts of the user (which in this example are high) and not directly to the speed or the acceleration (which in this example are weak). Thus, as will be detailed, the method according to the invention makes it possible to control the motors 2 by prioritizing the efforts of the user on the speed and the acceleration.

It is specified that an acceleration phase is a phase during which it is determined that the user seeks to increase the speed of the wheelchair 100. In an acceleration phase, the efforts of the user make it possible to increase the speed wheelchair 100.

Conversely, a deceleration phase is a phase in which the user seeks to reduce the speed of the wheelchair 100. Thus, in a deceleration phase, the efforts of the user brake the wheelchair in order to slow it down. Advantageously, the invention makes it possible to distinguish a phase of deceleration (which results from a choice of the user), from an external braking force, such as for example the action of the wind, a slope or a tire deflated.

A cruising phase is a phase in which the user maintains the wheelchair 100 at a substantially constant speed. In the cruising phase, the speed of the wheelchair 100 remains substantially identical (in other words, in the cruising phase the acceleration of the wheelchair 100 is substantially zero).

Acquisition of physical motor quantities - step (a) Physical quantities are acquired for each motor 2 independently. As will be described below, the independence of the measurements for each motor 2 makes it possible in particular to detect and control a turn phase.

Typically these measurements can be performed by variable speed drives each controlling a motor 2.

The measurement of the speed of rotation of motor 2 makes it possible to calculate the speed of rotation of a wheel to which it is connected and to calculate the torque developed by motor 2. Indeed, as specified above, each motor 2 is connected to a pinion which drives the sidewall of a tire 110 mounted on a wheel (i.e. the pinion rubs against the sidewall of the tire 110). By knowing the diameters of the pinion and the tire, it is easy to calculate the rotational speed of the wheel.

Similarly, by measuring the current absorbed by motor 2, it is easy to calculate the torque developed by motor 2.

Obtaining one or more physical quantities of the device - step (b)

As indicated previously, the method comprises obtaining one or more physical quantities of the device 1, including at least one acceleration and one inclination.

Typically these physical quantities can be obtained by the inertial unit or an accelerometer coupled or not to a gyroscope. In addition, the measurement can also be refined with a magnetometer.

Calculation of the inclination of the device

According to an advantageous arrangement, step (b) can comprise a calculation of the inclination of the device.

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

Advantageously, the inclination A of the device can be determined as follows: the accelerations communicated to the wheelchair by the user or by the assistance, and corresponding to the accelerations obtained by means of the controllers 302 or the motors 2, are subtracted from the measurements of acceleration from the inertial unit. 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 is rolling 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 errors which affect the measurements (bias, noise, drifts over time of the angular measurements). To limit these errors, filtering methods well known in signal processing can be implemented. For this purpose, filtering techniques can be used, such as moving averages or the average of the last N samples.

According to another arrangement, it is possible to determine the inclination A using the equation [Maths. 1].

Of course, it is also possible to determine the inclination of the device using the inertial unit, or any other method.

Anomaly detection - step (c)

In a particularly advantageous manner, the method according to the invention may comprise a step for detecting an anomaly. By anomaly, it is understood for example a slippage of a wheel, an overturning of the wheelchair 100 or even a slippage of the pinion 4 on a wheel.

The detection of an anomaly can be carried out by calculating a correlation value between the acceleration of the device and the speed of the at least one engine 2. Next, the correlation value is compared with an anomaly threshold value.

Thus, typically, in the event of overturning of the wheelchair, the device will have zero speed while the motors will have a high rotational speed because the wheels will be relieved of the constraints of the user's weight and the friction of the ground.

If the correlation value is greater than the anomaly threshold, then an anomaly is detected and step (f) comprises turning off the electrical voltage of the, or each, motor 2, to position the device 1 in the state of engine shutdown 2.

In other words, anomaly detection can consist of detecting an increase in acceleration exceeding a predetermined threshold corresponding to the inertia developed by the wheelchair and the user. This increase in acceleration may correspond to the sprocket slipping on the tire. It is then necessary to turn motors 2 off.

According to one embodiment, the correlation value can be calculated from the difference between a value of the acceleration of the device and the speed of the at least one motor.

In addition, anomaly detection can also be performed by comparing a variation of the inclination with respect to a horizontal axis. If the inclination A exceeds a defined threshold, then an anomaly is detected and step (f) comprises the electrical de-energization of the, or each, motor 2, to position the device 1 in the state of extinction of the motors 2.

In addition, another type of anomaly may be a speed of device 1 or motor 2 exceeding a previously set safety threshold.

In all cases, the detection of an anomaly causes the immediate stopping of the electric motors and therefore of the assistance. Early anomaly detection is particularly advantageous because it makes it possible to avoid an accident or a secondary accident. By early, it is understood that the anomaly detection is carried out at the earliest in the method according to the invention, as soon as the necessary quantities are acquired/obtained.

Estimation of a roughness level - step (d)

In a particularly advantageous and ingenious way, the method according to the invention comprises a step (d) of estimating a level of roughness of the ground on which the vehicle is rolling (i.e. typically the wheelchair 100). As will be described below, this step may be prior to estimating a user's effort.

Cleverly, the estimate of the roughness of the ground can be carried out according to the vibrations generated by the rolling of the wheelchair 100 on the ground.

Indeed, the asperities of the ground generate vertical jolts of the wheels. These jerks correspond to a variation of a vertical component of the acceleration of a wheel.

According to the embodiment proposed here, one can determine the vertical component of the acceleration according to [Maths. 2] by carrying out a sampling of measurements determined over a determined time step. For example, 50 samples can be taken with a step of 10ms.

From [Math. 2]. By calculating a moving average [Maths. 3] of the squares with a weighting of this mean, it is possible to adjust the sensitivity of the estimate. In other words, using a high weight (e.g. 100) the estimate is less sensitive to ground asperities. Conversely, by using a lower weighting, the estimate becomes more sensitive to the roughness of the ground.

Estimation of a friction level

According to a particularly clever arrangement of the invention, a level of friction F can be determined from the estimated roughness. The friction level F is determined as a function of the estimated roughness.

This estimate can then be refined by correcting the estimate of the level of friction.

Correction of friction level estimation

It may be necessary to correct the friction level F determined. For this, the method comprises the determination of an error due to friction ∈ _frot . Typically, the level of friction F can be corrected by integration and/or by linear regression.

According to a first embodiment, this method consists in integrating the forces undergone by the wheelchair 100 for a determined time (disregarding certain aberrant cases described below) in order to measure the force of friction of the ground without being disturbed by the forces of the user. The time determined for the integration is chosen so as not to be affected by the user's efforts on the wheels, while allowing rapid adaptation to external forces (roughness of the ground, wind, etc.).

According to this method, the error due to friction ∈ _frot can be determined according to [Maths. 4].

According to another embodiment, the error due to friction ∈ _frot can also be calculated by carrying out an integration with a sliding average which can be weighted, according to [Maths. 5].

A second method consists in saving the N previous measurements and obtaining a friction model by linear regression by recalculating the force undergone by the wheelchair [Maths. 6] which makes it possible to deduce the error due to friction, a coefficient of friction proportional to the speed squared and a coefficient of friction proportional to the speed by linear regression according to [Maths. 7]. This method makes it possible to take into account the frictions according to the variations of speed. While first method requires a readjustment time when changing gears.

Preferably, this determination is carried out over a predetermined period allowing an optimal estimation of the coefficient of friction as a function of the speed. Preferably, the duration may be about ten minutes.

These two methods make it possible to compensate for the change in friction linked to the speed.

Estimation of user effort - step (e)

The method according to the invention comprises a step of estimating an effort F _ut of a user. The estimation of an effort F _ut of a user is a particularly clever arrangement of the invention. Typically, the force F _ut of the user is estimated from the estimated level of friction, the inclination of the device 1, the torque of the motor 2 and the acceleration of the device 1. According to another embodiment, the force F _ut can be directly estimated from the inclination of the device 1, the torque of the motor 2 and the acceleration of the device 1, without taking into account the level of friction. According to this arrangement, the level of friction is not estimated and is replaced by the application of a predefined coefficient in the estimation of the force.

It is specified that the estimation of the force can be carried out for each wheel of the vehicle (the wheelchair 100 according to our example). The specific estimation for each wheel makes it possible to determine if a user is about to initiate a turn.

Indeed, in the case of a turn initiated by the user, the system will detect a difference in force applied by the user on each wheel. The difference in these forces makes it possible to detect that the user is engaging in a cornering phase and to adapt the assistance accordingly. The end of the turn will be detected when both wheels turn at the same speed. the system will then adapt its behavior according to the operating state desired by the user (braking, acceleration, cruising). It should be noted that when the system senses a sufficient braking force on both wheels, the system switches to the braking deceleration state even if it was in a cornering state.

The effort F _ut of the user is expressed as a sum of terms including at least the inclination of the device 1, the torque of the at least one motor 2 and the acceleration of the device 1.

Preferably, the sum expressing the effort of the user also includes the estimated level of friction.

According to the embodiment presented here, the estimation of an effort F _ut of the user is carried out using the relation [Maths 8].

As will be described below, the value of the effort (force) obtained makes it possible to adapt the electric assistance of the wheelchair.

Motion phase detection and motor control - step (f)

The force F _ut estimated in step (e) makes it possible to detect a movement phase from among several referenced phases: acceleration phase, deceleration phase, cruising phase or turning phase.

In other words, the various determinations, obtainings and estimates of the previous steps make it possible in particular to determine whether the user wishes to be in the stopping, acceleration, cruising, turning or decelerating phase.

Then, the motors (2) are driven in particular according to the detected movement phase.

More precisely, the use of the estimation of an effort F _ut of the user is particularly astute because it allows - at this stage - to determine a will of the user, that is to say to determine if the user is in accelerating, maintaining a substantially constant speed (cruising phase), or decelerating.

Thus, the use of an effort F _ut of the user makes it possible to precisely define the behavior of the wheelchair and of the user.

The fact of being based on the user's efforts makes it possible to minimize unwanted behavior by the user, such as for example a deceleration of the wheelchair on a rough surface, or a wheelchair that is difficult to move forward in sand or a slope.

Thus, by knowing both the physical quantities of the chair (speed, acceleration, inclination, current or motor torque) and the estimation of the effort F _ut of the user, it is possible to have a correct understanding of the situation and control the motors to best assist the user.

It is specified that the control of the motors is carried out between at least one operating state of the electric assistance in which the electric assistance completes the human propulsion by maintaining a substantially constant speed and at least one state of extinction of the motors 2 in which only human propulsion can move the chair 100.

In a particularly advantageous manner, the control of the motors 2 can be carried out according to two distinct modes.

According to a first mode M1 which only engages if the speed V of the wheelchair 100 is greater than a first speed threshold V _stop . Conversely, if it is detected that the speed V of the chair 100 is lower than the first speed threshold V _stop , the motors 2 are switched off (first condition C1 in FIG. 8).

If the speed of the wheelchair 100 is greater than the first speed threshold V _stop and the effort level F _ut is greater than a first effort threshold value F1 (condition C2 in FIG. 8), then it is determined that the user is in the acceleration phase and step (f) includes a command from the au least one motor 2 to position the device 1 in the operating state of the electrical assistance.

It is specified that in this case, alternatively, step (f) may include changing the instruction delivered to the controllers of the motors 2 to position the device 1 in a state of reinforcement of the electric assistance.

If the speed of the wheelchair 100 is greater than the first speed threshold V _stop and if the estimated effort F _ut is less than a second effort threshold value F2 (condition C3), then it is detected that the user is in deceleration phase and step (f) comprises the electrical de-energization of the at least one motor 2, to position the device 1 in the state of extinction of the at least one motor 2.

If the speed of the wheelchair 100 is greater than the first speed threshold and if the estimated effort F _ut is between the first effort threshold value F1 and the second effort threshold value F2 (condition C4), then it it is determined that the user is cruising. In this case, step (f) comprises the variation or maintenance of a setpoint of the at least one motor 2 to maintain the device 1 at a speed substantially equivalent to a speed acquired in step (b), or a decreasing speed depending on the level of assistance desired by the user.

In other words, in the cruising phase, the device 1 maintains a substantially constant or decreasing speed according to the user's wishes.

According to this first piloting mode, when different forces F _ut are estimated on each wheel and the difference in absolute value of these forces is greater than a third force threshold F _bend , and the estimated level of force is greater at the second effort threshold F2 (condition C5), then it is determined that the user is in the turning phase. In this case, step (f) includes applying a turn aid according to the level of help desired by the user. This can be done by applying a current differential to two respective motors 2, the current differential being proportional to a speed difference between the two motors 2. According to another arrangement, in the turn phase, the motors 2 can be turned off tension.

Typically, the current differential can be proportional to the speed difference between the motors. Thus, the setpoint of the motor whose rotation speed is the lowest is reduced, while conversely the setpoint increases on the opposite motor so as to accompany the rotational movement. This correction is only applied when the wheelchair trajectory is considered to be curved (so as not to amplify the trajectory oscillations when the wheelchair moves forward in a straight line).

When the absolute value of the difference in the speeds of rotation of each motor 2 is less than a second speed threshold value V _{thresholdendturn} and the force level F _ut is greater than the second force level F2 (condition C6), then it is determined that the user has completed their turn.

Thus, in other words, according to the first mode M1 shown schematically in FIG. 8, a mode in which the assistance engages and is maintained only if the chair is above a first speed threshold V _stop . If the user exerts sufficient force, the chair 100 will or will not help the user to accelerate depending on the chosen assistance configuration. When the user stops exerting an effort to advance the device. The assistance registers the speed and adapts the torque of the motors in order to maintain a constant speed in a straight line. If the user exerts a sufficient difference in force between the two wheels, the wheelchair will adapt or cut off the assistance to facilitate the turn. If the user brakes the device, the force exerted falls below a certain negative value, the assistance adapts or cuts off depending on the embodiment chosen. If the user relaxes his effort the system retains the speed and maintains it.

According to a particularly advantageous arrangement, the motor torque can be increased proportionally according to the estimated force according to a configuration chosen by the user.

According to a second control mode M2 shown schematically in FIG. 9, step (f) comprises comparing a speed of the device V determined in step (b) with a third speed threshold value Vstop2 called the trigger speed ( condition C7).

If the speed of the device is greater than the trigger speed Vstop2 (condition C8), then step (f) comprises the progressive increase of a setpoint of the at least one motor (2) until the speed of the device reaches a cruising speed threshold value. Then, step (f) comprises stabilizing a setpoint of the at least one motor (2) to maintain the speed of the device V substantially equal to the second speed threshold value V2.

According to this piloting mode, step (f) comprises comparing the estimated force Fut in step (e) with a third force threshold value F3. If the estimated force is less than the third force threshold value then step (f) comprises turning off the electrical voltage of the, or each, motor (2) to position the device (1) in the state extinction of at least one motor (2) (condition C7). Thus, if the user's efforts are relaxed, if the speed is above the stop threshold speed, the system will tighten towards its cruising speed.

In other words, according to the second control mode, above the second speed threshold, the wheelchair accelerates to reach a speed predefined by the user, when the user's efforts are below a third threshold of efforts, assistance cuts out. Process repetition

It is specified that the method is executed continuously, as shown schematically in FIG. 7. Preferably, the method is executed every 10 milliseconds.

[Math. 1].

A = arctan( —dVwheel — ax / az)

With: dVwheel the linearly reported acceleration of the wheelchair from the average speed of the wheels, ax is the measured horizontal acceleration, az is the vertical acceleration

[Math. 2].

With: a _zrms the effective value of the acceleration normal to the ground a _zn The acceleration in the direction normal to the ground measured by the accelerometer at time n.

N the number of samples

[Math. 3].

With: a _zrms Estimate of the effective value of the normal acceleration on the ground a _zn The normal acceleration on the ground measured by the accelerometer at instant n

N the weighting

[Math. 4].

With ∈ _frot Error in Newton due to the friction of the chair with the environment estimated independently of the speed δt Integration time chosen long enough to have a good estimate of the friction. But short enough to have a dynamic behavior (in our case several hundred ms) m User mass and chair

K Conversion constant (N /A) characteristic of the motor used, referred to the ground.

I _word Current (A) consumed by the motors ∈ = -1 or 1 Depending on the direction of the chair Cx Coefficient of friction proportional to speed squared (Ns ² /m ² )

C _α Coefficient of friction proportional to speed (N. s/m)

Vmot Speed of the motors relative to the ground considering that the roller is not skidding on the wheel (m/s). dVmot Acceleration of the motors relative to the ground (m/s ² ) g Gravitation (9.81 m/s ² )

K _r Estimated static friction coefficient in N [Maths. 5].

With: estimation of friction (N) with the environment at

instant n.

N= moving average weighting

[Math. 6]

With :

F _undergone Effort (N) undergone by the wheelchair [Math. 7]

[Math. 8]

With: F _ut Estimated user effort

Claims

1. Method for controlling an electric assistance device (1) for a human-powered vehicle (100), the electric assistance device (1) comprising at least one motor (2) making it possible to complete the human propulsion and comprising inertial acquisition means, the method being characterized in that it comprises at least the following steps:

(a) acquisition of physical quantities of the at least one motor (2), including a rotational speed (w) and a torque;

(b) obtaining one or more physical quantities of the device (1), including at least one acceleration (A) and one inclination;

(e) estimation of an effort (F _ut ) of a user of the device (1), from the torque of the at least one motor (2), the acceleration (A) of the device (1) and the inclination of the device (1);

(f) determination of a movement phase at least as a function of the estimated effort and control of the at least one motor (2), at least as a function of the determined movement phase, the movement phase being determined from among an acceleration phase, a cruising phase, or a deceleration phase, between at least one operating state of the electric assistance in which the electric assistance completes the human propulsion and at least one state of extinction of the at least one motor (2) in which only human propulsion can move the device (1).

2. Control method according to claim 1, comprising a step (d) of estimating a level of roughness of a ground on which the vehicle (100) comprising the device (1) is driving.

3. Control method according to claim 2, in which the estimation of the roughness of step (d) is carried out as a function of vibrations generated by rolling of the vehicle (100) on the ground.

4. Control method according to claim 3, in which the estimation of the roughness of step (d) is carried out according to the determination of a variation of a vertical component of the acceleration (a _rms ) caused by vibrations generated by the rolling of the vehicle (100) on the ground.

5. Control method according to any one of claims 2 to 4, step (d) comprises the estimation of the friction (F) as a function of the estimate of the roughness of step (d).

6. Control method according to claim 5, in which the estimation of the friction (F) comprises a correction of the estimation of the friction by integration and/or by linear regression.

7. Method according to any one of claims 1 to 6, in which the effort (F _ut ) of the user in step (e) is expressed as a sum of terms including at least the inclination of the device ( 1), the torque of the at least one motor (2) and the acceleration of the device (1).

8. Method according to claims 5 and 7 in combination, in which the sum expressing the effort (F _ut ) of the user also includes the estimated friction (F).

9. Control method according to any one of claims 1 to 8, in which, if a speed of the device (1) is greater than a first speed threshold (Vstop) and if the level of effort (F _ut ) is greater than a first force threshold value (F1), then it is determined that the user is in the acceleration phase and step (f) comprises electrically energizing the at least one motor (2 ) to position the device (1) in the electrical assistance operating state, or step (f) comprises increasing the electrical voltage supplied to the at least one motor (2) to position the device (1) in a state of power assist reinforcement.

10. Control method according to any one of claims 1 to 8, in which, if the speed of the device (1) is greater than a first speed threshold (V _stop ) and if the estimated force (F _ut ) is lower than a second effort threshold value (F2), then it is detected that the user is in the deceleration phase and step (f) comprises the electrical de-energization of the at least one motor (2) , to position the device (1) in the state of extinction of the at least one motor (2).

11. Control method according to any one of claims 1 to 8, in which, if the speed of the device (1) is greater than a first speed threshold (Vstop) and if the estimated force (F _ut ) is comprised between a first effort threshold value (F1) and a second effort threshold value (F2), then it is determined that the user is in the cruising phase, and step (f) comprises the variation or maintaining a setpoint of the at least one motor (2) to maintain the device (1) at a speed substantially equivalent to a speed acquired in step (b) or at a predefined speed.

12. Control method according to any one of claims 1 to 8, in which, if different forces (F _ut ) are estimated on each wheel and the difference in absolute value of these forces is greater than a third threshold of effort (F _turn ), and each estimated effort (F _ut ) is greater than a second effort threshold (F2), then it is determined that the user is in the turning phase.

13. Control method according to claim 12, in which step (f) comprises the electrical de-energization of the at least one motor (2), to position the device (1) in the state of extinction of the at least one engine (2)

14. Control method according to claim 12, in which step (f) comprises the application of a current differential to two respective motors (2), the current differential being proportional to a rotational speed difference between the two motors (2).

15. Control method according to any one of claims 12 to 14, in which, if the absolute value of the difference in rotational speeds of each motor (2) is less than a second speed threshold value (V _{thresholdendturn} ) and the effort level (F _ut ) is greater than the second effort level (F2), then it is determined that the turn phase is complete.

16. Control method according to any one of claims 1 to 8, in which step (f) comprises comparing a speed of the device (1) determined in step (b) with a third threshold value of speed (V _s top2) called triggering speed.

17. Control method according to claim 16, in which, if the speed of the device (1) is greater than the trigger speed (V _stop2 ), then step (f) comprises the progressive increase of a setpoint of the at least one motor (2) until the speed of the device (1) reaches a cruising speed threshold value, then, step (f) comprises the stabilization of a setpoint of the au at least one motor (2) to maintain the speed of the device (1) substantially equal to the cruising speed threshold value.

18. Electric assistance device (1) for a human-powered vehicle, configured to implement a method according to any one of claims 1 to 17, comprising at least one motor (2) having a rotor (22) connected to a pinion (4) which rubs against a tire (110) of a wheel (104, 105) of a vehicle and comprising inertial acquisition means, 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).

19. Electric assistance device (1) according to claim 18, characterized in that the controller (302) is adapted to transmit to said at least one motor (2) a control instruction issued by said at least one control device (303).

20. Electrical assistance device (1) according to any one of claims 18 or 19, comprising an inertial unit (301).

21. Electrical assistance device (1) according to any one of claims 18 to 20, wherein the control member (303) is a computer adapted to execute the method according to any one of claims 1 to 17.

22. Human-powered vehicle being a wheelchair (100) comprising two rear wheels (104, 105) each having a tire (110), characterized in that it comprises at least one electric assistance device (1) according to the any of claims 18 to 21.

23. Wheelchair (100) according to claims 20 and 22 in combination, comprising a seat (103) and a frame comprising a structure, the control member (303) and the inertial unit (301) being fixed under the seat ( 103) or integrated into the frame structure (102).

24. Computer program product comprising code instructions for performing a method according to any one of claims 1 to 17, when executed by a computer.

25. 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 17.