Method for compensating resistive forces applied to a vehicle

Abstract

This method for compensating resistive forces applied to a vehicle (V) comprising an electric motor includes the following steps: Conversion (step 1) of a representative value (X) of the accelerator pedal deflection into a reference force ( ); Application (step 3) of the reference force ( ) to at least one drive wheel of the vehicle (V); Determination (step 5) of a reference acceleration ( ) by dividing the reference force ( ) by the mass of the vehicle (V); Measurement (step 7) of the effective acceleration ( ) of the vehicle (V); Calculation (step 9) of a correction force ( ) from the reference and effective accelerations ( ); and Application (step 11) of the correction force ( ) to said wheel. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Method for compensating resistive forces applied to a vehicle technical field

[0001] The present invention relates to a method for compensating resistive forces applied to a vehicle.

[0002] In particular, the present invention relates to a method for compensating the feeling of acceleration for a given depress of the accelerator pedal.

[0003] In general, the invention applies to any vehicle equipped with an electric motor, and in particular to hybrid or electric motor vehicles. Prior art

[0004] Motor vehicles have historically responded to a torque control law at their wheels known as "open loop".

[0005] More specifically, when the driver of a vehicle presses the accelerator pedal, a vehicle and / or engine control unit interprets this press as an intention to accelerate, also known as the "driver's intention." The value representing the pedal press is translated into a setpoint for the percentage of maximum engine power at its operating speed, corresponding, within the limits of transmission efficiency, to the power supplied to the drive wheels for propelling the vehicle, and then into a setpoint for engine torque. This engine torque setpoint also corresponds to a driving force to be applied to the wheels, taking into account the dynamic radius of the tires.

[0006] However, a motor vehicle is generally not equipped with any means capable of monitoring driving conditions and adapting the applied torque accordingly. This lack of adaptation can lead to several unpleasant situations from the driver's point of view, all of which correspond to the fact that the vehicle does not behave in the same way, for the same accelerator pedal depressment, depending on the nature of the road, and in particular depending on the resistive forces applied to the vehicle. One such resistive force is, for example, the incline of the slope.

[0007] Thus, for the same depressment of the accelerator pedal, a driver will have different sensations of acceleration or deceleration depending on the slope in which he is located.

[0008] Other resistive forces are highlighted in the fundamental principle of dynamics below, applied to the vehicle:

[0009] ma = S- _ FF _ F _ p 1 M'oue 4 he here t

[0010] with m the mass of the vehicle, a its acceleration, the force applied to F wi-oue vehicle wheels, Cmot the engine torque,1 the radius of a wheel, wroue the wheel rotation speed, œmot the engine rotation speed, Fa the aerodynamic drag force, Fro the rolling resistance force, Fp the slope resistance force, and Finert the inertial resistance force of the vehicle. Description of the invention

[0011] The present invention therefore aims to overcome the aforementioned disadvantages and to provide a vehicle driver, for a given depressment of the accelerator pedal, with the same feeling of acceleration or deceleration regardless of the slope or the speed at which the vehicle is located.

[0012] The present invention relates to a method for compensating resistive forces applied to a vehicle comprising an electric motor, the method comprising the following steps:

[0013] - Conversion of a value representing the deflection of a pedal acceleration into a reference force;

[0014] - Application of the reference force to at least one drive wheel of the vehicle;

[0015] - Determination of a reference acceleration by dividing the reference force by the mass of the vehicle;

[0016] - Measurement of the effective acceleration of the vehicle;

[0017] - Calculation of a correction force from the reference and effective accelerations; And

[0018] - Application of the correction force to said wheel.

[0019] Thus, the resistive forces are compensated, and the driver will experience the same sensation of acceleration or deceleration for the same depress of the accelerator pedal. In particular, this advantage is also achieved in a vehicle driving mode in which the driver controls deceleration by slightly lifting their foot off the accelerator pedal. Such a mode is sometimes called "One pedal" in English.

[0020] In one embodiment, the calculation step includes a substep of determining an acceleration error by subtracting the reference acceleration from the effective acceleration.

[0021] Advantageously, the calculation step includes a substep of filtering the reference and effective accelerations before the substep of determining an acceleration error.

[0022] Advantageously, the calculation step includes a substep of calculating the correction force from the acceleration error and using a PID controller and / or a "Fuzzy" controller, and / or an MPC controller.

[0023] In one embodiment, the method includes a step of detecting a change in the direction of the vehicle's gear lever and a step of applying a factor of -1 to the correction force when such a change in direction is detected.

[0024] In one embodiment, the calculation step includes a substep of limiting the value of the correction force as a function of the speed and / or acceleration of the vehicle.

[0025] Advantageously, the step of applying the corrective force to the wheel is subject to at least one condition including reaching a particular representative value of brake pedal depressurization and / or reaching a particular vehicle traction state and / or activating a particular driving assistance mode.

[0026] In a particular embodiment, if at least one condition is not met, the method includes a step of setting the value of the applied correction force to zero and a step of memorizing the last non-zero value of the applied correction force, this last non-zero value being applied again once at least one condition is met again.

[0027] The present invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the computer to implement the steps of the process as defined above.

[0028] The present invention also relates to a motor vehicle comprising a computer and a computer-readable data carrier, the computer program as defined above being recorded on the data carrier. Brief description of the drawings

[0029] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0030] [Fig.1] is a schematic representation of the steps in a resistive force compensation process according to the invention; and

[0031] [Fig.2] is a schematic representation of the sub-steps of a calculation step of a correction force of the process according to the invention. Detailed description of at least one embodiment

[0032] A method for compensating resistive forces applied to a vehicle V has been schematically represented in [Fig.1].

[0033] Vehicle V comprises an electric motor and a gear lever. For example, it is a hybrid or electric motor vehicle comprising at least one drive wheel.

[0034] The method is implemented for a vehicle dynamics V summarized by the following fundamental principle of dynamics:

[0035] ma = Ftol + Fres

[0036] with m the mass of the vehicle, a its acceleration, Ftot the total force applied to the wheels of the vehicle by the electric motor, Fres the total resistance force, which includes for example the resistance forces detailed previously, namely the aerodynamic resistance force Fa, Fro the rolling resistance force, Fp the slope resistance force, and Finert the inertia resistance force of the vehicle.

[0037] The method includes a step 1 of converting a value X representing the depressment of an accelerator pedal into a reference force Fref.

[0038] This step 1 uses the transposition of the driver's depressment of the accelerator pedal into a value X representing said depressment of the accelerator pedal.

[0039] The conversion is carried out according to a control law specific to the vehicle's driving mode. For example, depressing the accelerator pedal is interpreted as the driver's intention to accelerate and is therefore converted into a reference force designed to propel the vehicle forward. Conversely, when the driver lifts their foot off the accelerator pedal, this action is interpreted as the driver's intention to slow down and is therefore converted into a reference force designed to brake the vehicle. The reference force can also be zero, so that the vehicle is "freewheeling" and subject only to resistive forces.

[0040] Next, a step 3 is carried out, applying the reference force to at least one drive wheel of the vehicle V.

[0041] This step 3 is more precisely carried out by applying a reference torque Cref to the wheel of the shape:

[0042] Cref = Fref xr

[0043] with Fref the reference force applied to the wheels of the vehicle, Cref the reference torque, etr the radius of a wheel.

[0044] At the same time, a step 5 is carried out to determine a reference acceleration ^ef by dividing the reference force Fref by the mass m of the vehicle, such that:

[0045] a ^ref w

[0046] This reference acceleration is an acceleration representative of the acceleration desired by the vehicle driver when depressing the pedal accelerator.

[0047] On the other hand, a step 7 is carried out to measure the effective acceleration of the vehicle aeiï. This effective acceleration is obtained, for example, by direct measurement using an accelerometer, or by indirect calculation from the speed, or by GPS data.

[0048] From these effective and reference accelerations aeff and a step 9 of calculation of a correction force FCO)T is carried out.

[0049] Finally, a step 11 is carried out of applying the correction force to at least one drive wheel, in the same way as for the reference force, the reference force and the correction force being added together.

[0050] The correction force is an additional force exerted on the wheel and allowing to compensate for the resistive forces highlighted by the difference in value between the effective and reference accelerations fleff eta^.

[0051] Thus, instead of using an open-loop acceleration system which requires the driver to press harder on the accelerator pedal to compensate for a resistive force on the vehicle, the method according to the invention proposes a closed loop allowing the total force applied to the wheels of the vehicle to be adapted.

[0052] Schematically represented in [Fig.2] are sub-steps of step 9 of calculation of the correction force.

[0053] More precisely, step 9 of calculating the correction force includes, for example, a substep 13 of determining an acceleration error e by subtracting the effective acceleration from the reference acceleration. Thus:

[0054] e ~ 'h-ef " aeff

[0055] Optionally, substep 13 for determining the acceleration error is preceded by substep 15 for filtering the effective and reference accelerations. This filtering is more particularly a time synchronization of the two values ​​of effective and reference acceleration.

[0056] Furthermore, step 9 for calculating the correction force includes a substep 17 for calculating the correction force based on the acceleration error. More specifically, substep 17 calculates the correction force in such a way as to reduce the acceleration error.

[0057] This calculation substep 17 is carried out with a controller, for example a PID controller and / or a "Fuzzy" controller, and / or an MPC controller ("Model Predictive Control" in Anglo-Saxon terms).

[0058] Optionally, a substep 19 is performed to limit the value of the correction force. The limitation is, for example, based on the vehicle's speed and / or acceleration. The limitation can be performed by linear filtering, or by first-order nonlinear filtering, or even by second-order nonlinear filtering.

[0059] The limitation makes it possible in particular to limit the dynamics of the regulator as well as the absolute value of the correction force.

[0060] In particular, this limitation substep 19 makes it possible not to apply too large a correction force, or too rapid changes in correction force, which could surprise the driver of the vehicle and be unpleasant for his driving.

[0061] For the limitation in absolute value of the correction force, it is for example possible to limit the correction force to 3000 Newton for vehicle speeds ranging from 0 to 7 km / h, and then to limit the correction force more and more as the vehicle speed increases: for example, limit the correction force to 1500 Newton for a speed of 15 km / h.

[0062] Optionally, step 11 of applying the correction force to the wheel is subject to at least one condition C.

[0063] At least one condition includes, for example, reaching a specific representative value for brake pedal depressurization and / or reaching a specific traction state of the vehicle and / or activating a specific driver assistance mode. A specific driver assistance mode is, for example, the "speed limiter" mode.

[0064] For this purpose, step 9 of calculating the correction force includes a substep 21 of checking at least one condition C.

[0065] Following this substep 21, if at least one condition is not met, the process includes a step of setting the value of the applied correction force to zero (step not shown) and a step 23 of memorizing the last non-zero value Fmem of the applied correction force is carried out.

[0066] The last non-zero value is reapplied to the drive wheel once at least one condition is met again. This mechanism allows the vehicle to have an optimal response when restarting on an incline, for example.

[0067] Optionally, the method further includes a step 25 for detecting a change in the direction of the vehicle's gear selector lever and a step 27 for applying a factor of -1 to the calculated correction force when such a change in direction is detected, i.e., when shifting from forward to reverse or vice versa, particularly, in the case of a vehicle equipped with an automatic transmission, shifting the lever from the "D" (drive) position to the "R" (reverse) position or vice versa. This facilitates maneuvering on a slope when such maneuvers involve the vehicle changing its direction of travel.

[0068] In a specific embodiment, this process is a computer-implemented method.

[0069] The invention further relates to a computer program comprising instructions which implement the process as described above when executed by computer.

[0070] A computer running the program is, for example, the vehicle's on-board computer or the powertrain computer including the electric motor.

[0071] Vehicle V includes, for example, a computer and a data carrier readable by said computer, the data carrier having recorded said computer program.

Claims

Demands

1. A method for compensating resistive forces (Fres) applied to a vehicle (V) comprising an electric motor, characterized in that it comprises the following steps: - Conversion (step 1) of a representative value (X) of the depressment of an accelerator pedal into a reference force (^ref); - Application (step 3) of the reference force (^ref) to at least one drive wheel of the vehicle (V); - Determination (step 5) of a reference acceleration (aref) by dividing the reference force (^ref) by the mass (m) of the vehicle (V); - Measurement (step 7) of the effective acceleration (aeff) of the vehicle (V); - Calculation (step 9) of a correction force (Fcorr) from the reference and effective accelerations (^ref); and - Application (step 11) of the correction force (FCon) to said wheel;step (11) of applying the correction force (F_corr) to the wheel being subject to at least one condition including reaching a particular representative value of brake pedal depressurization and / or reaching a particular traction state of the particular vehicle and / or the activation of a particular driving assistance mode, the method comprising, if at least one condition is not met, a step of zeroing the value of the correction force applied and a step (23) of memorizing the last non-zero value of correction force applied, this last non-zero value (F_mem) being reapplied once at least one condition is again met.;

2. A method according to claim 1, wherein the calculation step (9) includes a substep (13) of determining an acceleration error (e) by subtraction between the reference acceleration (^ref ) and the effective acceleration (^eff).

3. A method according to claim 2, wherein the calculation step (9) comprises a substep (15) of filtering the reference accelerations and effective (ttref ; aeff) before substep (13) of determining an acceleration error (e).

4. A method according to any one of claims 2 and 3, wherein the calculation step (9) includes a substep (17) of calculating the correction force (Fcon.) from the acceleration error (e) and using a PID controller and / or a "Fuzzy" controller, and / or an MPC controller.

5. A method according to any one of claims 1 to 4, comprising a step (25) of detecting a change in direction of the vehicle's gear lever (V) to go from forward to reverse or vice versa, and a step (27) of applying a factor of -1 to the correction force (FCOrr) when such a change in direction is detected.

6. A method according to any one of claims 1 to 5, wherein the calculation step (9) includes a substep (19) of limiting the value of the correction force (FCOiT) as a function of the speed and / or acceleration of the vehicle.

7. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the process according to any one of claims 1 to 6.

8. Motor vehicle (V) comprising a computer and a computer-readable data carrier, the computer program according to claim 7 being stored on the data carrier.

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