Method for controlling the torque of a vehicle wheel motor and associated torque controller

Abstract

Method for controlling the torque of a wheel motor of a vehicle and associated torque controller. The invention relates to a method for controlling the torque of at least one wheel motor (10) of a vehicle (1000), the method comprising: determining the effective slip of at least one wheel of the vehicle driven by said wheel motor, implemented without obtaining, by the torque controller, a data representative of the vehicle's orientation; and controlling the torque of said wheel motor, as a function of the determination of the effective slip of said wheel. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for controlling the torque of a wheel motor of a vehicle and associated torque controller technical field

[0001] The present invention belongs to the general field of vehicle drive systems in which at least some of the wheels are equipped with "wheel motors". More particularly, it relates to torque control of one or more wheel motors, for example, powered by an electrical source. It also relates to a torque controller for one or more wheel motors, as well as a vehicle in which such a controller is installed. Previous technique

[0002] So-called "motor land vehicles" generally include axles that carry wheels and support the vehicle body relative to the wheels. These axles are driven in rotation by a motor located at a distance from the wheels, via a transmission mechanism.

[0003] Other vehicle drive solutions exist, including systems called "wheel motors." A wheel motor is an assembly in which the motor is mounted on the wheel and provides a driving or braking function for that wheel. In this way, the torque applied to the wheel is directly controlled by its motor. This technological solution notably eliminates the need for a wheel drive differential.

[0004] However, current torque control solutions generate significant costs related to the use of vehicle steering angle sensors, which are due in particular to the environment in which these sensors are installed - these sensors being regularly subjected to shocks, vibrations, and / or the presence of dust - but also to the constraints in terms of expected reliability on this type of sensor. Description of the invention

[0005] The present invention aims to remedy all or part of the disadvantages of the prior art, in particular those set out above, by proposing a solution which improves the traction and grip of the vehicle, through an optimal allocation and distribution of power to the wheel motors of this vehicle.

[0006] To this end, and according to a first aspect, the invention relates to a method for controlling the torque of a wheel motor of a vehicle, the method being implemented by a torque controller mounted within the vehicle and comprising:

[0007] - a determination of an effective slip of at least one wheel of the vehicle (1000) driven by said wheel motor, implemented without the torque controller obtaining data representative of a vehicle orientation; and;

[0008] - a control of the torque of said wheel motor, depending on the determination of a effective sliding of said wheel.

[0009] In this application, "vehicle orientation data" refers to an angle measurement taken on the vehicle's steering system, which reflects a change in the vehicle's trajectory orientation relative to a straight trajectory. This orientation data corresponds, for example, to an angle measurement of the steering wheel(s) relative to the chassis, or to an angle measurement of the steering wheels of a first steering axle relative to a second steering axle.

[0010] In general, it is considered that the steps of a process should not be interpreted as being linked to a notion of temporal succession.

[0011] In particular embodiments, the method for controlling the torque of a wheel motor may further include one or more of the following characteristics, taken individually or in all technically possible combinations.

[0012] In particular embodiments, the wheel motor is an electric wheel motor.

[0013] In particular embodiments, the vehicle comprises a plurality of wheels equipped with a wheel motor, and the controller is then configured to control the torque of each of the wheel motors of the plurality of wheels.

[0014] Thus, in this particular embodiment, the torque controller is configured to act centrally on the different wheel motors of the vehicle, and considers, for this purpose, the data associated with the different wheel motors of the vehicle to allocate the torque of a specific wheel motor.

[0015] In particular embodiments, the method further comprises determining a value representative of the effective slip of each of the wheels as a function of a steering radius of the vehicle, and determining said steering radius, as a function of data representative of the speeds of the wheels of the plurality, and as a function of at least one dimension of said vehicle.

[0016] Thus, in accordance with this particular embodiment, the turning radius of the vehicle is not obtained by analyzing data from a steering angle sensor installed on the steering wheel of the vehicle or more generally linked to a steering control of the vehicle or on a joint of the vehicle or on a pivot point of the vehicle, but determined from a processing of data from the wheels and / or the wheel motors that drive them.

[0017] In particular embodiments, at least one dimension of said vehicle includes a radius value of a wheel of the plurality, at least one track value and / or at least one wheelbase value of the vehicle.

[0018] Generally, the track width of a vehicle is defined as the distance between the two wheels of the same axle. More precisely, the track width corresponds to the distance between the centers of the contact patches of the wheels of the same axle, measured when the vehicle is empty (i.e., unloaded). The same vehicle may have front and rear track widths of different lengths.

[0019] The wheelbase is defined as the distance between the outermost axle axes of a vehicle. When articulated, a vehicle can have several wheelbase values, for example a first value corresponding to the front part of the vehicle, and a second value corresponding to the rear part.

[0020] In particular embodiments, the method further includes determining a representative value of the effective slip of each of the wheels as a function of a steering radius of the vehicle, and obtaining said steering radius from an association table linking a steering radius to at least one dimension of said vehicle.

[0021] In particular embodiments, this association table is determined by machine learning.

[0022] In particular embodiments, the representative value of the effective slip is further determined as a function of the rotational speeds of the wheel motors and a reference speed of the wheels of the plurality.

[0023] In particular embodiments, the method further includes determining, for each of the wheel motors of the vehicle, a limiting torque as a function of the representative value of the effective slip of the wheel driven by said wheel motor, and as a function of a representative value of an optimal slip of said wheel.

[0024] In particular embodiments, the method further includes allocating a torque to each wheel motor of the vehicle, according to an overall torque setpoint and said limit torques.

[0025] In particular embodiments, the overall torque setpoint is determined as a function of a vehicle speed setpoint and an estimated vehicle speed, the method further comprising an estimation of the vehicle speed as a function of the turning radius and the reference speed of the wheels of the plurality.

[0026] In particular embodiments, the vehicle comprises a plurality of wheels equipped with a wheel motor, and the controller is configured to control the torque of a single wheel motor of one wheel, without obtaining data representative of the rotational speeds of the other wheel motors of the vehicle.

[0027] Alternatively, the controller may be common to one axle or common to all wheel motors of the machine, and be configured to control the torque of each wheel motor without obtaining data representative of the rotational speeds of the other wheel motors of the vehicle.

[0028] In particular embodiments, the determination of effective slip includes a determination that the rotational speed of the controlled wheel motor increases significantly over a predetermined period, while the linear acceleration of said vehicle is less than a threshold value over that same period.

[0029] In particular embodiments, the linear acceleration of said vehicle is determined by an inertial measurement unit equipping said vehicle.

[0030] In particular embodiments, an inertial unit is integrated into one wheel motor or all wheel motors of the vehicle.

[0031] In particular embodiments, the control of the torque of a particular wheel motor without obtaining representative data of the rotation speeds of the other wheel motors of the vehicle is implemented by taking into account an estimate of the slope on which the vehicle is located; this slope estimation can in particular be carried out by an inertial measurement unit equipping the vehicle.

[0032] In particular embodiments, the control of the torque of a particular wheel motor, without obtaining representative data of the rotational speeds of the other wheel motors of the vehicle, is implemented as a function of an estimate of a slip / skip angle, a vehicle load, the attitude or attitude of the vehicle, the yaw rate, the temperature of the wheel motors and / or the electrical consumption of the wheel motors.

[0033] According to a second aspect, the invention relates to a computer program comprising instructions for implementing a torque control method according to the invention, when said program is executed by a processor.

[0034] This program may use any programming language, and be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0035] According to a third aspect, the invention relates to a computer-readable recording medium on which the computer program according to the invention is recorded.

[0036] The information or recording medium can be any entity or device capable of storing the program. For example, the medium can include a storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a hard disk drive.

[0037] On the other hand, the information or recording medium can be a transmissible medium such as an electrical or optical signal, which can be transmitted via an electrical or optical cable, by radio, or by other means. The program according to the invention can, in particular, be downloaded onto an Internet-type network.

[0038] Alternatively, the information or recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the process in question.

[0039] According to a fourth aspect, the invention relates to a torque controller for at least one wheel motor of a vehicle, the controller being configured to implement a torque control method according to the invention.

[0040] According to a fifth aspect, the invention relates to a vehicle comprising a plurality of wheel motors and in which a torque controller according to the invention is mounted.

[0041] According to a sixth aspect, the invention relates to a wheel in which a torque controller according to the invention is embedded. Brief description of the drawings

[0042] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures:

[0043] [Fig-1] [Fig.1] is a front view representation of a vehicle in which is embedded a torque controller, according to an example of implementation of the invention;

[0044] [Fig.2A] [Fig.2A] is a top view representation of an articulated vehicle in a turn;

[0045] [Fig.2B] [Fig.2B] is a top view representation of a non-articulated vehicle in a turn;

[0046] [Fig.3] [Fig.3] represents modules embedded in a torque controller, according to a particular implementation method of the invention;

[0047] [Fig.4] [Fig.4] represents modules embedded in a torque controller, according to a particular implementation method of the invention;

[0048] [Fig.5] [Fig.5] schematically represents an example of the hardware architecture of a torque controller;

[0049] [Fig.6] [Fig.6] represents, in flowchart form, a particular method of implementing an overall method of controlling the torque of at least one wheel motor, for example executed by the torque controller of [Fig.3];

[0050] [Fig.7] [Fig.7] represents, in flowchart form, a particular method of implementing step S160 of determining a limit torque of at least one wheel motor of a vehicle 1000;

[0051] [Fig.8] [Fig.8] represents, in the form of a flowchart, a particular method of implementing an overall method of controlling the torque of a wheel motor, for example executed by the torque controller of [Fig.4];

[0052] [Fig.9] [Fig.9] is a top view representation of an articulated vehicle in a turn, and the notations considered for determining its turning radius;

[0053] [Fig. 10] [Fig. 10] is a top view representation of a three-wheeled vehicle in a turn, and the notations considered for determining its turning radius;

[0054] [Fig. 11] [Fig. 11] is a top view representation of the notations considered for determining the turning radius and the effective slip of the wheels of an articulated vehicle having several wheelbase values ​​and several track values;

[0055] [Fig. 12] [Fig. 12] is a representation of a drive device, according to a particular embodiment of the invention; and,

[0056] [Fig. 13] [Fig. 13] represents modules embedded in a torque controller, according to a particular embodiment of the invention. Description of the implementation methods

[0057] Fig. 1 is a front view representation of a vehicle in which a torque controller is mounted, according to an example of an implementation of the invention.

[0058] Generally speaking, a "vehicle" in the sense of the invention corresponds to any motorized land vehicle, that is to say any vehicle capable of traveling on the ground or on rails, and which can be powered by a mechanical force generated by one or more motors.

[0059] In particular embodiments, the vehicle is a wheel loader, a multi-function tool carrier, a forklift, a tandem roller, a compact mini track loader or an autonomous agricultural machine.

[0060] As illustrated in [Fig. 1], the vehicle 1000 is, in this example, an articulated loader. The distinguishing feature of a loader is its ability to quickly transport or move a large quantity of materials, particularly during earthmoving work. To achieve this, the loader 1000 is equipped, among other things, with a loader bucket 300, a stabilizer (also called a "counterweight") 500, and a cab 400.

[0061] In this example, the vehicle 1000 is also equipped with four wheels 100. A drive device is associated with at least one front wheel and at least one rear wheel. Preferably, each wheel 100 of the vehicle 1000 is equipped with a drive device 10, and in this case, the vehicle 1000 comprises four drive devices, to form a transmission of a 1000 four-wheel drive vehicle 100.

[0062] It should be noted that the number of wheels 100 equipping the vehicle 1000 does not constitute a limiting factor of the invention. The following developments can in fact be easily generalized by a person skilled in the art to the case where the vehicle is equipped with a number of wheels other than four.

[0063] Each drive device 10 includes, in particular, a motor, typically an electric motor. It should be noted, however, that there are no limitations on the energy source powering the motor. The following developments can easily be adapted by those skilled in the art to cases where the motor is of the hydraulic type, for example, with axial pistons.

[0064] The [Fig. 12] is a representation of a drive device, according to a particular embodiment of the invention.

[0065] As illustrated in [Fig. 12], the drive device 10 comprises an electric motor 11, a parking brake 12, a gearbox 13, and a speed controller 14 for the electric motor. This drive device further comprises an inertial measurement unit (IMU) 15 connected to the speed controller 14, as well as a sensor 16 for the rotational speed of the electric motor 10. An inertial measurement unit (IMU) is composed of a set of sensors for measuring linear accelerations and rotational velocities, enabling the estimation of the motion of a point of interest in its six degrees of freedom: three translational degrees modeled by the linear velocity vector of the point, and three rotational degrees modeled by the instantaneous rotation vector of the frame of reference. An inertial measurement unit therefore has six sensors: three accelerometers and three gyroscopes.

[0066] The reducer 13 includes a housing which is, for example, fixed to the chassis frame of the vehicle 1000. The reducer 13 also includes an output hub, rotatably mounted relative to the housing. The output hub of the drive device 10 carries a wheel 100, and said drive device 10 supports the body of the vehicle 1000 relative to said wheel 100.

[0067] Alternatively, the wheel motor has a rotating housing, and the drive device 10 therefore does not include an output hub.

[0068] Returning to the description of [Fig. 1], the vehicle 1000 further includes a torque controller 200 of at least one of the wheel motors whose functionalities are described in more detail with reference to Figures 3 to 11.

[0069] In a particular embodiment, a centralized architecture is considered, and the torque controller is embedded in the vehicle body or in its engine. In this particular case, the torque controller is, for example, integrated into the electronic control unit (ECU). (the Anglo-Saxon terminology) of the vehicle 1000. Alternatively, but still considering a centralized architecture, the torque controller 200 is integrated into one of the vehicle's wheels, called the "master wheel." In this case, all traction management is performed by this master wheel. Alternatively, but still considering a centralized architecture, the torque controller 200 is integrated into each of the wheels equipped with an in-wheel motor, but only one wheel, called the "master wheel," performs the control at any given time.

[0070] The wheel motors are then connected, via one or more data buses, to the torque controller 200, the functionalities of which are described in more detail with reference to figures 3 to 11.

[0071] According to a particular implementation, the data buses are CAN type buses (acronym for "Controller Area Network"), for example conforming to the ISO 118987 standard. The use of CAN type buses is advantageous since it allows several electronic devices to be connected to the same cable, thus avoiding the use of dedicated cables for the transport of each piece of information.

[0072] Alternatively, a distributed architecture is considered, in which each wheel incorporates a torque controller configured to determine the torque to be applied by that wheel's in-wheel motor. In this case, all traction management is performed by a so-called "plug and play" (or ready-to-use) wheel. More precisely, traction management is performed autonomously by the wheel(s), requiring nothing more than a power source and a torque or speed command. It is therefore important to note that when such a distributed architecture is considered, it may be advantageous to send a slip signal from that wheel to a higher-level controller in the vehicle, for example, to alert the driver that the wheel is slipping.

[0073] Figure 2A is a top-view representation of an articulated vehicle in a turn, in which the invention can be implemented. As illustrated in Figure 2A, the vehicle 1000 comprises four wheels 100p£, 1 00p^, 100p£, 100 and has a central articulation point connecting the front section FP and the rear section RP of the chassis. Thus, to make a turn, the front section FP pivots on the horizontal plane relative to the rear section. The steering angle therefore depends directly on the articulation angle. This property is advantageous since it allows articulated vehicles (such as articulated loaders) to be used for tasks requiring high maneuverability.

[0074] Figure 2B is a top-view representation of a non-articulated vehicle in a turn, in which the invention can be implemented. As illustrated in Figure 2B, to make a turn, the wheels 100p£, 100pp, 100p£, 1 OOpp of the non-articulated vehicle pivot, for example around an axis located at each end of an axle and perpendicular to that axle.

[0075] Figure 3 represents modules embedded in a torque controller, according to a particular embodiment of the invention. In this particular embodiment, the architecture is centralized, and the torque controller 200 according to the invention is then configured to control all the wheel motors of the vehicle, taking into account, for a given wheel motor, the information from said wheel motor, but also the data from the other wheel motors of the vehicle.

[0076] As illustrated in [Fig.3], the torque controller 200 includes a MOD_OBS module, referred to as the "observation module", comprising several sub-modules:

[0077] - a M0D_WS module for determining the wheel speeds of the vehicle, also configured to determine a so-called "reference speed";

[0078] - a MOD_TURN module for estimating a turning radius R of the vehicle, in function of the reference Vppp speed;

[0079] - a MOD_VS module for estimating the vehicle's Vypc speed, based on the reference speed V ppp and turning radius R;

[0080] - a MOD_SR module for estimating the slip rate kj_pppp of each wheel 100j=pppL, depending on the rotation speeds ^FL, ^FR, ^RL, ^RR of the wheel motors of the vehicle, the reference speed, and the turning radius R.

[0081] The torque controller 200 further comprises:

[0082] - a CTRL_SR determination controller, for each of the wheel motors of the vehicle, of a limiting torque TLpp, TLpp, TLpp, TLpp as a function of the effective slip kj-p ppp of the wheel driven by the wheel motor, and as a function of the representative value of an optimal slip kSpp of this wheel;

[0083] - a CTRL_SD controller for determining an overall torque setpoint TG, in based on a speed setpoint Vppp and the estimated speed Vypp of the vehicle; and,

[0084] - a MOD_TQ module for torque allocation based on limiting torques T Lpp, TLpp, TLpp, TLpp and the overall torque setpoint TG. This MOD_TQ module is further configured to transmit, to each wheel motor of the vehicle, a torque setpoint Tpp, Tpp, Tpp, Tpp to be applied by these wheel motors.

[0085] Figure 4 represents modules embedded in a torque controller, according to another particular embodiment of the invention. Unlike the particular embodiment illustrated in Figure 3, which considered a centralized architecture, the embodiment of Figure 4 considers the case of a distributed architecture. The 200 torque controller is then configured to control the torque of a single wheel motor, and for example embedded within that wheel.

[0086] As illustrated in [Fig. 4], this torque controller 200 includes a MOD_OBS module, also called an "observation module", which includes, in particular:

[0087] - a MOD_AL sub-module for obtaining inertial data. This data inertial values ​​are, for example, determined by an inertial measurement unit connected to this MOD_AL acquisition module, such as the inertial measurement unit 15 described with reference to [Fig. 12]; and,

[0088] - a sub-module M0D_VR for obtaining the rotation speed of the wheel motor. This rotational speed is determined, for example, by a speed sensor connected to this MOD_AL acquisition module, such as sensor 16 described with reference to [Fig.12],

[0089] This torque controller 200 further comprises:

[0090] - a MOD_DET module for calculating an estimated linear speed, and for determining that the evolution of this estimated linear velocity over a predetermined period is greater than a first threshold value, while the linear acceleration is less than a second threshold value during this same period; and,

[0091] - a MOD_CTRL module for determining a torque Tj to be applied by the wheel motor that it controls.

[0092] Fig. 5 schematically represents an example of the hardware architecture of a torque controller 200.

[0093] As illustrated in [Fig. 5], the torque controller 200 has the hardware architecture of a computer. Thus, the torque controller 200 includes, in particular, a processor 1, random access memory 2, read-only memory 3 and non-volatile memory 4. It also has communication means 5.

[0094] The read-only memory 3 of the torque controller 200 constitutes a storage medium according to the invention, readable by the processor 1, on which a computer program PROG according to the invention is stored, comprising instructions for executing steps of the torque control process according to the invention. The PROG program defines functional modules of the torque controller 200, which rely on or control the hardware elements 1 to 5 of the torque controller mentioned above. These functional modules are illustrated in [Fig. 3] or [Fig. 4] by way of no limitation, and are described in more detail below with reference to different embodiments.

[0095] In the embodiments described below, the communication means 5 enable the torque controller 200 to transmit instructions to the wheel motors relating to the torque value to be achieved. To this end, the means of communication 5 includes a wired or wireless communication interface, capable of implementing any suitable communication protocol.

[0096] Figure 6 represents, in flowchart form, a particular method of implementing an overall method for controlling the torque of at least one wheel motor, for example executed by the torque controller 200 of Figure 3. This torque controller 200 is configured to centrally control the torques of all the wheel motors of a vehicle 1000 comprising four wheels 100 FL, 100 FR, 100 RL, 100 RR all equipped with wheel motors.

[0097] The overall torque control method includes a first step S100 for obtaining the effective rotational speeds ^FL, ^FR, ^RL, ^RR of the vehicle's wheel motors. This step S100 is implemented, for example, by the M0D_WS sub-module of the MOD_OBS observation module described with reference to [Fig. 3]. According to a particular implementation, the rotational speeds are determined by rotation sensors, such as sensor 16 illustrated in [Fig. 12], installed on the wheel motors, and transmitted to said M0D_WS module.

[0098] The overall control method further includes a step SI 10 of determining the estimated speed Vj = FL FR RL RR of the vehicle wheels, as a function of the effective rotational speeds ^i = FL, FR, RL, RR of the wheel motors, and the radius Rj = pp pp pp pp of said wheels. Generally, the estimated speed V is expressed as Vj × Rr. Without slippage, the estimated speed and the actual speed have identical values. However, in the case of slippage, only the estimated speed corresponds to this expression.

[0099] During this same SI step 10, a so-called "reference speed" Vpgp is determined. Assuming that at least one wheel of the vehicle is in contact with the ground, the wheel with the lowest slip rate then becomes the one providing the reference speed. When a positive torque (or "drive torque") is applied by the wheel motors, the reference speed Vppp is expressed as follows: Vref = min(v fl , V fd V fd V FL ) , with MIN() being the minimum operator. Conversely, when a negative torque (or "braking torque") is applied by the wheel motors, the reference speed Vref is expressed, for example, as VrEF = MAX( ^FL' V FL' FL' V Fl) , with MAX() being the maximum operator.

[0100] Alternatively, the reference speed VpFF is an average of the speeds of the same axle. According to another embodiment, the reference speed corresponds to the average of the speeds of the wheels of an axle, each of which may optionally be weighted by the

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114] torque allocated to them. In the specific case where the rear axle of the vehicle illustrated in Figure 11 is considered, the reference speed Vppp is expressed, for example, as follows: V ref = (V rl +V r J / 2 = (Rrl*«+RrR*W a- b2 p - VR -«R- « ~ Rp^R^Tl^ r rl = r r-^ "b.. r rr = r r + ~I tj — n Èl — , / p 2 . t 2 t 2 ^1 ^FL— UF~ 2 ~\-KR +-^2 ' 2 RFR = RF + "T = + £22 " £12 _|_ with Rr the turning radius of the rear part of the vehicle, Rp the turning radius of the front part of the vehicle, a the angular velocity around the center of rotation C', the track of the front part of the vehicle, b2 the track of the rear part of the vehicle, the distance between the pivot and the axle center of the front part of the vehicle, and L2 the distance between the pivot and the axle center of the rear part of the vehicle, Then, during an S120 step, a turning radius R of the vehicle is determined, based on representative wheel speed data, and based on at least one dimension of said vehicle. This S120 step is implemented, for example, by the MOD_TURN submodule of the MOD_OBS observation module described with reference to [Fig.3]. In a particular embodiment illustrated by Figure 9, assuming that the vehicle 1000-1 has four wheels and is articulated at its center, that the inner wheels (e.g., the front-left and rear-left wheels) have the same speed vlef t, that the outer wheels (e.g., the front-right and rear-right wheels) have the same speed vright, and that the center of the front axle and the rear axle also have the same speed, then: ^left=^FL=^RL = Rixa =(R3 - |)xa Vright = VFR = Vrr = R2 xa = (R3 + |) et R3=-^f xb / 2 J vlett vnglit /

[0115] with a the angular velocity around the center of rotation C', b the wheelbase of the vehicle, and R3 the turning radius of the vehicle 1000.

[0116] In another particular embodiment illustrated by [Fig. 10], assuming that the vehicle 1000-2 comprises three wheels, then:

[0117] VFL = a [0H8] v FR = r2x a = (R1+b)xa

[0119] r ~ V R = R3xa = y(R1+f) +a 2 xa

[0120] VFR-VFL a- b

[0121] and p _ Vfl xb VpR-VpL

[0122] with a the angular velocity around the center of rotation C, b the wheelbase of the vehicle, a the track width of the vehicle, VR the speed of the rear wheel and Rj the radius of

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] rotation of the front-left wheel of the vehicle 1000-2. In another embodiment illustrated by [Fig. 11] – and corresponding to a generalization of the embodiment illustrated with reference to [Fig. 9] – assuming that the vehicle 1000-3 has four wheels and is articulated, then: V FL = R-fl xa = (RP - y ) x oc V pr =Rpp x <x = (R p + ~ jx ot VRL = RrL X OC = (Rr - ^x cl V RR = RrR Rp = ^Rr + L^ - L^ R~

[0130] with a the angular velocity around the center of rotation C, by the track of the front part of the vehicle, the track of the rear part of the vehicle, Lj the distance between the pivot and the axle center of the front part of the vehicle, L2 the distance between the pivot and the axle center of the rear part of the vehicle, Rr the turning radius of the rear part of the vehicle and Rp the turning radius of the front part of the vehicle.

[0131] Returning to Figure 6, the overall torque control method further includes a step S130 for estimating the effective slip ki of each of the vehicle's wheels, based on a representative data point for the rotational speeds of the wheel motors, the vehicle's turning radius, and a representative data point for a reference speed V ppp of the wheels. This step S130 is implemented, for example, by the MOD_SR sub-module of the MOD_OBS observation module described with reference to the [Fig.3].

[0132] In a particular embodiment, the effective slip k^ of each of the The slip rate of a vehicle's wheels is expressed as a ratio called the "slip rate". Generally, a slip rate k of a wheel 100j of radius F, having an estimated linear speed V and driven by a wheel motor 102 with a rotational speed , is expressed as follows:

[0133] k. _ x rr^i with abs() the absolute value operator. Ki~ abs(V^

[0134] Considering again the method of implementation illustrated by Figure 9, and in assuming that a driving torque is applied, that the front wheel left is the slowest (and therefore does not slip or slips very little), so the reference speed Vppp corresponds to the speed V p^ ceche front left wheel.

[0135] Furthermore, VFL = MpL X Rp^ and _ ^fl * r~vfl _ q FL absty^

[0136] The slip rate kRL of the left rear wheel is expressed as follows:

[0137]

[0138]

[0139] _ ^RL X r~Vp.L ^RL X r'V FL . RL ab$(VF^ The slip rate kpp of the right front wheel is expressed as follows: _mpr x r-VFR ~FR ab^VFR) MVpL x

[0140] And the slip rate kpp of the right rear wheel is expressed as follows:

[0141] ru xr4V x^ RR ab^vj ab^V x

[0142] Thus, this kj value, representing the effective slip of a wheel, is determined based on data specific to said wheel motor, such as its rotational speed, and based on at least one dimension of said vehicle, such as the radius of at least one wheel of the vehicle, a track width, and / or a wheelbase value of the vehicle. In other words, this kj value, representing the effective slip of the wheel, is not determined from data representing the vehicle's orientation generated by a steering angle sensor on the vehicle's steering wheel or generated by a steering angle sensor installed at the pivot joint of an articulated vehicle.

[0143] The overall torque control method further includes a step S140 for estimating the vehicle speed, based on the turning radius and based on of a reference speed. This S140 step is implemented for example by the MOD_VS sub-module of the MOD_OBS observation module described with reference to [Fig.3],

[0144] Considering again the implementation method illustrated by Figure 9, and still assuming that a drive torque is applied, that the front left wheel is the slowest, and that consequently the reference speed VRFF corresponds to the speed VFF of this front left wheel, the speed VyFc of the vehicle is expressed as follows: , R.. Vv EC = (v fl x^

[0145] Then, during a step S150, an overall torque setpoint TG is determined, based on the estimated vehicle speed VyFc and a speed setpoint Vgpp. This step S150 is implemented, for example, by the CTRL_SD controller for determining an overall torque setpoint described with reference to [Fig. 3]. This CTRL_SD controller is, for example, a PID (Proportional, Integral, Derivative) controller with feedforward action.

[0146] The overall torque control method further includes a step S160 of determining, for each of the wheel motors of the vehicle, a limit torque TLFF TLfr, TLpp TLpp as a function of the effective slip kj of the wheel driven by the wheel motor, and as a function of the optimal slip k$FF of this wheel 100. The step S160 includes the steps S1600, S1610, S1620 and S1630 described below with reference to [Fig.7], and is implemented for example by the CTRL_SR controller for determining a limit torque described with reference to [Fig.3].

[0147] In a particular embodiment, these limit torque values ​​TLFF TLpR, TLrf, TLRp are further determined as a function of at least one criterion among a slip / skip angle, a vehicle load, attitude or trim, yaw rate (this is an angular rate), the temperature of the wheel motors 10y and the electrical consumption of the wheel motors 10y.

[0148] Then, during a step S170, a torque value TFF TFR, TRF, TRRest is allocated to each of the wheel motors, depending on the limit torques TLfl, TLFR, T^RL' ^RR and the overall torque setpoint TG. This step is implemented, for example, by the MOD_TQ torque allocation module described with reference to [Fig.3].

[0149] According to a first illustrative example, if the overall torque TG is 40Nm, and the vehicle includes four wheel motors each having a limit torque of 20 Nm, then the overall torque value is equally distributed among the four wheel motors. In other words, each wheel motor will receive a command to apply a torque of 10 Nm.

[0150] According to a second illustrative example, if the overall torque TG is 40 Nm, and the vehicle comprises four wheel motors 10i=Fp Fp pp pp and the limit torques are as follows: TLfl = 2, TLFR = 20, TLrl = 3, TLRR = 20, then wheel motor 10j=p£ will be allocated a torque TFF of 2 Nm corresponding to its limit torque, wheel motor 10^=RF will be allocated a torque TRF of 3 Nm corresponding to its limit torque, and the remaining 35 Nm to be allocated will be equally distributed between the last two motors 1 Qj-FR RR. In other words, the two motors 10j=FR RR will be allocated a torque TFR, TRR of 17.5 Nm.

[0151] Finally, the overall torque control process includes a step S180 in which the torques allocated during step S170 are transmitted to the respective wheel motors, and applied by them.

[0152] It is important to recall at this stage that the number of wheels 100 equipping the vehicle 1000 does not constitute a limiting factor of the invention. The preceding developments concerning torque allocation are in fact easily adaptable by a person skilled in the art if the vehicle is equipped with a number of wheels other than four.

[0153] Fig. 7 represents, in flowchart form, a particular method of implementing step S160 of determining a limit torque of at least one wheel motor of a vehicle 1000.

[0154] As illustrated in Figure 7, the control method comprises a first step S1600 during which at least one kSFF value representing an optimal slip of at least one wheel 100j of the vehicle 1000 driven by at least one wheel motor 10 is obtained. In a particular embodiment, this kSFF value representing an optimal slip corresponds to an optimal slip rate of a wheel. In a particular embodiment, several optimal slip rates are obtained, each associated with one of the wheels of the vehicle. In a particular embodiment, the controller is dedicated to controlling the torque of a single wheel motor, and a single optimal slip rate associated with the wheel whose wheel motor is controlled by this controller is then obtained during this step S1600.

[0155] The optimum slip rate is determined, for example, according to the type of surface, and / or the type of wheel or tire.

[0156] In a particular embodiment, this optimum slip rate is determined by a machine learning model.

[0157] In particular implementation modes, this machine learning model is implemented in the form of neural networks (convolution, perceptron, autoencoder, recurrent, etc). According to a particular implementation, the neural networks considered are recurrent neural networks of the "long short-term memory" type ("Long Short-Term Memory", LSTM, according to Anglo-Saxon terminology).

[0158] Furthermore, it is important to note that there are no limitations attached to the type of training technique used to obtain this machine learning model. Any technique implementing a learning algorithm (or "machine learning" in Anglo-Saxon terminology) and providing, as output, a value representing the optimal slip of a wheel, given input data, can be considered in the context of the invention (for example, support vector machine, logistic regression, etc.). In other words, the learning model is independent of the training method used to train this model.

[0159] In addition, any training criterion known to a person skilled in the art can be considered during the training phase of this machine learning model, such as the least squares method or cross-entropy minimization.

[0160] The control process further includes a step S1610 of obtaining the k1 values ​​representative of an effective slip of the wheels 100, determined during the step S130 of estimating the effective slip k} of each of the wheels described with reference to [Fig.6].

[0161] The control method further includes a step S1620 in which the representative values ​​of optimal slip kSE? and effective slip kj are compared. This comparison step S1620 is carried out for each of the vehicle's wheels.

[0162] Finally, an S1630 step is implemented in which so-called "limit torque" values ​​are determined for each of the wheel motors of the vehicle.

[0163] Figure 8 represents, in flowchart form, a particular method of implementing an overall method for controlling the torque of a wheel motor, for example executed by the torque controller of Figure 4. Unlike the method described with reference to Figure 7, this overall method of torque control is implemented by a controller dedicated to controlling the torque of a single wheel motor, and for example integrated within that wheel.

[0164] As illustrated in [Fig. 8], this overall torque control method includes a first step S200 for obtaining inertial data. This S200 data acquisition step is implemented, for example, by the M0D_AL inertial data acquisition sub-module described with reference to [Fig. 4]. As discussed in more detail below, this inertial data is determined, for example, by an inertial measurement unit installed at within the drive system, such as the inertial measurement unit 16 described with reference to [Fig. 12]. These inertial data correspond to linear accelerations and / or angular velocities of rotation. As an example, we subsequently consider the case where these inertial data correspond to linear accelerations, referred to as "measured linear accelerations".

[0165] The overall control method further includes a step S210 for obtaining the rotational speed with ï = FL, FR, RL OR RR of a wheel motor of the vehicle. This step is implemented for example by the submodule M0D_VR described with reference to [Fig.4].

[0166] Then, during a step S220, the torque controller 200 calculates an estimated linear speed, based on the rotational speed of the wheel motor obtained during the acquisition step S210, and the radius R of the wheel driven by this wheel motor. More precisely, this estimated linear speed is expressed as Vj — (Oj X Rr

[0167] The method further includes a step S230 of determining that the estimated linear acceleration over a predetermined period (e.g., 20 s) is greater than a first threshold value, while the measured linear acceleration is less than a second threshold value (e.g., 5 m / s²) over the same period. These steps S220 and S230 are implemented, for example, by the M0D_DET module described with reference to [Fig. 4].

[0168] If this is the case (e.g., if the estimated linear acceleration during the predetermined period is greater than the first threshold value, while the measured linear acceleration is less than the second threshold value during the same period), a step S240 is implemented in which the torque of the wheel driven by the aforementioned wheel motor is controlled. More precisely, a torque Tj to be applied by the wheel motor is determined.

[0169] As an example, consider the case of a four-wheeled vehicle traveling in a straight line, with all four wheels aligned. Assume that during the journey, one of the wheels rolls onto a patch of black ice and begins to "slip." In other words, the angular / rotational velocity of this wheel increases significantly, without this resulting in an increase in the vehicle's linear speed. Since the vehicle remains at a relatively constant speed, the linear acceleration detected by the inertial measurement unit in a horizontal plane and in the direction in which the vehicle is moving is low or even zero. In this particular embodiment, the control device 200 detects this difference between the linear acceleration determined from the inertial data and the speed estimated by measuring the rotation of the wheel motor, and adjusts the torque accordingly.

[0170] Figure 13 shows modules embedded in a torque controller, according to a particular embodiment of the invention. This torque controller is configured to control the torque of a single wheel motor, and for example, embedded within this wheel.

[0171] As illustrated in [Fig. 13], this torque controller comprises:

[0172] - a MOD_OBS_SL slope observation module connected to a tachometer TCH, and to an IMU inertial measurement unit;

[0173] - a MOD_OBS_AT altitude observation module connected to the module MOD_OBS_SL observation of a slope and to the IMU inertial measurement unit;

[0174] - a MOD_PRED module for predicting estimated rotational speeds, connected to the MOD_OBS_SL module for observing a slope, to the MOD_OBS_AT module for observing an altitude and to a MOD_OBS_TR module for determining a traction force.

[0175] - and a MOD_DEC decision module connected to the MOD_PRED module of prediction, as well as to the MOD_OBS_SL module for observing a slope.

[0176] In a particular embodiment, the slope observation module MOD_OBS_SL takes as inputs wheel rotation speeds OJj and a raw acceleration &RAW measured by an inertial measurement unit (IMU). This slope observation module MOD_OBS_SL is configured to generate, from these inputs, a so-called "refined" acceleration (resp. a refined rotation speed), that is, an acceleration devoid of the projection term of the support reaction opposing gravity. This refined acceleration is determined, for example, by applying a Kalman filter to the raw acceleration ^RAW measured by the IMU. This slope observation module MOD_OBS_SL is also configured to determine longitudinal and transverse accelerations qt.

[0177] The MOD_OBS_AT altitude observation module takes as input these longitudinal and transverse accelerations ^t, as well as wheel accelerations ^ROT measured by the IMU inertial measurement unit. It is configured to estimate the roll R and pitch P of the part fixed to the wheel chassis, for example by applying a complementary filtering algorithm or Kalman filtering to these input data.

[0178] The MOD_PRED prediction module, for its part, takes as input the estimated longitudinal and transverse accelerations, roll R and pitch P, a traction force determined by the MOD_OBS_TR module, as well as parameters P characterizing the vehicle such as its mass, wheel radius, etc. This MOD_PRED module is configured to predict different wheel accelerations (resp. different wheel rotation speeds ^i, EST) corresponding to different adhesion conditions, using a dataset maintained over a horizon of several time steps.

[0179] In particular implementation modes, this MOD_PRED prediction module includes a machine learning model, for example implemented in the form of neural networks (convolution, perceptron, auto-encoder, recurrent, etc.).

[0180] Furthermore, it is important to note that there are no limitations attached to the type of training technique used to obtain this machine learning model. Any technique implementing a learning algorithm (or "machine learning") and providing, as output, an estimated acceleration (or rotational speed) of the wheel as a function of grip conditions can be considered in the context of the invention (for example, support vector machine, logistic regression, etc.). In other words, the learning model is independent of the training method used to train it.

[0181] In addition, any training criterion known to a person skilled in the art can be considered during the training phase of this machine learning model, such as the least squares method or cross-entropy minimization.

[0182] Finally, the MOD_DEC decision module takes as input these different predicted / estimated wheel accelerations (resp. EST rotational speeds) and the "refined" acceleration (resp. refined rotational speed), to estimate the slip / slip of this wheel, and thus apply a torque control algorithm, for example similar to that described with reference to [Fig.5].

Claims

Demands

1. A method for controlling the torque of at least one wheel motor (10) of a vehicle (1000), the method being implemented by a torque controller (200) mounted within the vehicle and comprising: • a determination (S 130, S230) of an effective slip of at least one wheel (100) of the vehicle (1000) driven by said at least one wheel motor, implemented without obtaining, by the torque controller, a data representative of a vehicle orientation; and, ; • a control (S 170, S240) of the torque of said at least one wheel motor, as a function of the determination of an effective slip of said wheel.

2. A method of torque control according to claim 1, the vehicle (1000) comprising a plurality of wheels (100) equipped with a wheel motor (10), the controller being configured to control the torque of each of the wheel motors.

3. A torque control method according to claim 2, wherein the determination of the effective slip is a determination (S 130) of a value (kj) representative of the effective slip of each of the wheels as a function of a steering radius (R) of the vehicle, and the method further comprises a determination (S 120) of said steering radius (R) as a function of representative wheel speed data (100) of the plurality and as a function of at least one dimension of said vehicle.

4. A torque control method according to claim 3, wherein at least one dimension of said vehicle comprises a radius value of a wheel of the plurality, at least one track value and / or at least one wheelbase value of the vehicle (1000).

5. A torque control method according to claim 2, wherein the determination of the effective slip is a determination (S 130) of a value (kj) representative of the effective slip of each of the wheels as a function of a steering radius (R) of the vehicle, and the method further comprises obtaining said steering radius (R) from an association table linking a steering radius to at least one dimension of said vehicle.

6. A method for controlling torque according to any one of claims 3 to 5, the value (kJ) representing the effective slip being further determined as a function of the rotational speeds (wi) of the wheel motors and a reference speed (V ppp) of the wheels of the plurality.

7. A method for controlling torque according to any one of claims 3 to 6, further comprising a determination (S 160), for each of the wheel motors (10) of the vehicle (1000), of a limiting torque as a function of the value (k^) representing the effective slip (k^) of said wheel (100), and as a function of a value representing an optimal slip (kSpp) of said wheel (100).

8. A method of torque control according to claim 7, further comprising an allocation (S 170) of torque to each wheel motor of the vehicle, as a function of an overall torque setpoint and said limit torques.

9. A method of torque control according to claim 8, the overall torque setpoint being determined as a function of a setpoint (V VSET^ of vehicle speed and an estimated speed (Vypçj) of the vehicle (1000), the method further comprising an estimation (S 140) of the speed (Vypy) of the vehicle as a function of the turning radius (R) and the reference speed (Vppp) of the wheels of the plurality.

10. A method of torque control according to claim 1, the vehicle (1000) comprising a plurality of wheels (100) equipped with a wheel motor (10), and the controller is configured to control the torque of a single wheel motor of one wheel (100), without obtaining data representative of the rotational speeds of the other wheel motors of the vehicle.

11. A torque control method according to claim 10, wherein the determination (S 130, S230) of effective slip comprises a determination that the rotational speed of the controlled wheel motor increases significantly during a predetermined period, while the linear acceleration of said vehicle is less than a threshold value during said period.

12. A control method according to claim 11, the linear acceleration of said vehicle being determined by an inertial measurement unit equipping said vehicle.

13. A computer program (PROG) containing instructions for implementing a torque control method according to one of any of claims 1 to 12, when said program is executed by a processor.

14. Torque controller (200) of at least one wheel motor (10) of a vehicle (1000), the controller being configured to implement a torque control method according to any one of claims 1 to 12.

15. Vehicle (1000) comprising a plurality of wheel motors (10), and in which is mounted a torque controller (200) according to claim 14.

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