VERY PRECISE CONTROL OF THE TORQUE REFERENCE OF THE POWERTRAIN OF A LAND VEHICLE DURING A BRAKING PHASE

Abstract

A control method is implemented in a vehicle comprising a powertrain designed to supply the drive wheels with torque based on a torque setpoint. This method includes a step (10-50) in which the torque setpoint is determined based on the sum of a first acceleration setpoint to be supplied to the drive wheels and an estimate of the resistive acceleration experienced by the vehicle. This resistive acceleration, when the vehicle is braking, is a function of the acceleration measured at the drive wheels, the theoretical acceleration the vehicle would experience if traveling on a flat road with a predefined mass, and the braking deceleration experienced by the vehicle. Figure 3

Description

Title of the invention: HIGHLY ACCURATE CONTROL OF THE TORQUE SETPOINT OF THE GMP OF A LAND VEHICLE DURING A BRAKING PHASE Technical field of the invention

[0001] The invention relates to land vehicles comprising a powertrain (or GMP) providing drive wheels with a torque which is a function of a torque setpoint, and more precisely the control of this torque setpoint. State of the art

[0002] Certain land vehicles, possibly of the automobile type, comprise a powertrain (or GMP) arranged so as to provide their drive wheels with a torque depending on a torque setpoint (called at the wheels) which has just been determined. This torque setpoint is used to control the torque producers of the GMP (namely each driving machine (thermal or electric) of the latter), but also to choose the appropriate ratio of the gearbox when the latter is automated.

[0003] Generally, the torque setpoint is determined as a function of the sum of a first setpoint, defining the acceleration to be provided by the GMP at the driving wheels, and an estimate of a resistive acceleration representative of the resistive forces undergone by the vehicle at the instant considered. Currently, each estimate of resistive acceleration is determined by subtracting the acceleration actually measured at the driving wheels from the theoretical acceleration that the vehicle would have if it were traveling on a flat road with a predefined mass.

[0004] A disadvantage of this method of determining the resistive acceleration estimate lies in the fact that it induces an overestimation of this resistive acceleration during the braking phases, and therefore the generation of an excessively high torque setpoint then requiring, for example, unnecessary downshifts in the gearbox when overtaking another vehicle. It will be understood in fact that the deceleration of the vehicle is integrated into the resistive acceleration estimate and therefore the latter is overestimated, which induces a reduction in driving pleasure, in particular in terms of longitudinal acceleration.

[0005] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0006] It proposes in particular for this purpose a control method, on the one hand, intended to be implemented in a land vehicle comprising a powertrain capable of providing drive wheels with a torque as a function of a torque setpoint, and, on the other part, comprising a step in which this torque setpoint is determined as a function of a sum of a first acceleration setpoint to be provided at the drive wheels and an estimate of a resistive acceleration experienced by the vehicle.

[0007] This control method is characterized by the fact that in its step, when the vehicle is in a braking phase, the resistive acceleration estimate is determined as a function of an acceleration measured at the driving wheels, of a theoretical acceleration that the vehicle would have if it were traveling on a flat traffic lane with a predefined mass, and of a braking deceleration experienced by the vehicle.

[0008] Thus, throughout the duration of a braking phase, the calculation of the resistive acceleration estimate can take into account the braking deceleration of the vehicle, and therefore there is no longer any risk of overestimating this resistive acceleration, which makes it possible to maintain driving pleasure during this braking phase.

[0009] The control method according to the invention may include other characteristics which may be taken separately or in combination, and in particular:

[0010] - in its step, one can determine the estimate of resistive acceleration in a braking phase by subtracting the acceleration measured at the drive wheels and braking deceleration from the theoretical acceleration;

[0011] - in its step, we can determine each estimate of resistive acceleration in outside of a braking phase by subtracting the acceleration measured at the drive wheels from the theoretical acceleration that the vehicle would have if it were traveling on a flat road with a predefined mass;

[0012] - in its step, we can determine the first acceleration instruction in subtracting a speed setpoint from an actual current vehicle speed;

[0013] - in its step, we can determine a second total acceleration setpoint to be provided by the powertrain at the drive wheels by summing the first acceleration setpoint and resistive acceleration estimate, then this second total acceleration setpoint can be converted into a torque setpoint;

[0014] - in its step, when the vehicle includes a driving assistance function suitable for controlling vehicle movements during an autonomous driving phase (at least partial), the estimate of resistive acceleration can be determined based on the acceleration measured at the drive wheels, theoretical acceleration and braking deceleration when the vehicle is in a braking phase during an autonomous driving phase (at least partial).

[0015] The invention also provides a computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing a control method of the type presented above, in a land vehicle comprising a powertrain capable of supplying drive wheels with torque as a function of a torque setpoint, in order to control this torque setpoint.

[0016] The invention also proposes a control device, on the one hand, intended to equip a land vehicle comprising a powertrain capable of supplying to drive wheels a torque as a function of a torque setpoint, and, on the other hand, comprising at least one processor and at least one memory arranged to carry out the operations consisting of determining this torque setpoint as a function of a sum of a first acceleration setpoint to be supplied to the drive wheels and an estimation of a resistive acceleration undergone by the vehicle.

[0017] This control device is characterized by the fact that its processor and memory are also arranged to carry out the operations consisting, when the vehicle is in a braking phase, in determining the estimate of resistive acceleration as a function of an acceleration measured at the driving wheels, of a theoretical acceleration that the vehicle would have if it were traveling on a flat traffic lane with a predefined mass, and of a braking deceleration undergone by the vehicle.

[0018] The invention also proposes a land vehicle comprising a powertrain capable of supplying drive wheels with a torque as a function of a torque setpoint, and a control device of the type presented above.

[0019] For example, this vehicle may also include a driving assistance function capable of controlling movements of the vehicle during an autonomous driving phase (at least partially).

[0020] Also for example, this vehicle can be of the automobile type. Brief description of the figures

[0021] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0022] [Fig. 1] schematically and functionally illustrates an exemplary embodiment of a land vehicle comprising a thermal GMP, a supervision computer, a driving assistance computer and a control device according to the invention,

[0023] [Fig.2] schematically and functionally illustrates an exemplary embodiment of a supervision computer comprising an exemplary embodiment of a control device according to the invention, and

[0024] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention. Detailed description of the invention

[0025] The invention aims in particular to propose a control method, and an associated DC2 control device, intended to allow very precise control of the torque setpoint cc which defines the torque to be supplied by the GMP of a land vehicle V to the drive wheels of the latter (V), at least during braking phases.

[0026] In the following, it is considered, by way of non-limiting example, that the land vehicle V is a motor vehicle. This is for example a car, as illustrated in [Fig.l]. But the invention is not limited to this type of land vehicle. It in fact relates to any type of land vehicle comprising a powertrain (or GMP) capable of providing the drive wheels with a torque which is a function of a determined torque setpoint.

[0027] [Fig.l] schematically shows a (land) vehicle V comprising, in particular, a GMP transmission chain with a thermal motor MMT and a coupling device DC1 associated with a gearbox BV, a supervision computer CS, and a control device DC2 according to the invention.

[0028] It should be noted that the GMP could also be of the hybrid type (electric and thermal) or of the all-electric type.

[0029] As illustrated, the transmission chain also comprises, here, a drive shaft AM and a transmission shaft AT.

[0030] The operation of the transmission chain (and therefore of the GMP) is supervised by the supervision computer CS.

[0031] The GMP here being purely thermal, as an illustrative example, it comprises a thermal motor MMT comprising a crankshaft (not shown) which is fixedly secured to the engine shaft AM in order to drive the latter (AM) in rotation. This thermal motor MMT is capable of operating according to a speed to provide a first torque cl, on order of the supervision computer CS. In addition, it (MMT) is capable of being coupled to the primary shaft AP of the gearbox BV via the coupling device DC1. The latter (DC1) is capable of delivering a second torque c2 from the first torque cl produced by the thermal motor MMT, in particular for at least one train T1 of driving wheels.

[0032] For example, the coupling device DC1 may be a clutch. But in an alternative embodiment it could be a torque converter.

[0033] Also for example, the train T1 can be located in the front part PVV of the vehicle V. It is preferably, and as illustrated, coupled to the transmission shaft AT via a differential (here front) DV. But in a variant this train T1 could be that referenced T2 which is located in the rear part PRV of the vehicle V.

[0034] Also for example, the gearbox BV can be automated. But in a variant this gearbox BV could be manual.

[0035] It will be noted, as illustrated non-limitingly in [Fig.l], that the vehicle V may also, possibly, include a driving assistance computer CF ensuring at least one driving assistance function FAC for controlling the movements of the vehicle V in phases of autonomous driving (at least partially). For example, this driving assistance function FAC may be responsible for regulating the speed of the vehicle V and the distance between vehicles (it is then often designated by the English acronym ACC ("Adaptive Cruise Control")).

[0036] In an autonomous driving phase controlled by the driving assistance function FAC, the supervision computer CS sends to this driving assistance function FAC at least one estimate of the torque which is supplied to the drive wheels by the GMP and a minimum torque which is achievable by (or which can supply) the GMP at the drive wheels. Upon receipt of these torque estimates and minimum torque, the driving assistance function FAC determines for the supervision computer CS a torque setpoint cc which defines the torque which it wants the GMP to supply to the drive wheels and which cannot be less than the minimum torque.

[0037] It will be noted that the driving assistance computer CF and the supervision computer CS can, for example, communicate via an internal communication network RC of the vehicle V, possibly multiplexed, as illustrated non-limitingly in [Fig.l].

[0038] As mentioned above, the invention proposes in particular a control method intended to allow very precise control of the torque setpoint cc which defines the torque to be supplied by the GMP of the vehicle V to the drive wheels of the latter (V), at least during the braking phases.

[0039] This (control) method can be implemented at least partially by the control device DC2 (illustrated at least partially in FIGS. 1 and 2) which comprises for this purpose at least one processor PR1, for example a digital signal processor (or DSP ("Digital Signal Processor")), and at least one memory MD. This control device DC2 can therefore be produced in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). For example, it can be a microcontroller.

[0040] The memory MD is live in order to store instructions for the implementation by the processor PR1 of at least part of the control method. The processor PR1 may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is understood to mean any type of device capable of carrying out at least one electrical or electronic operation.

[0041] In the example illustrated non-limitingly in Figures 1 and 2, the control device DC2 is part of the driving assistance computer CF. But this is not obligatory. Indeed, the control device DC2 could comprise its own dedicated computer, or could be part of another computer embedded in the vehicle V (here a vehicle) and providing at least one other function, such as for example the supervision computer CS.

[0042] As illustrated non-limitingly in [Fig. 3], the (control) method, according to the invention, comprises a step 10-50 which is implemented each time that a torque setpoint cc must be determined in the vehicle V for its GMP.

[0043] Step 10-50 of the method comprises a sub-step 20 in which one (for example the control device DC2) determines the estimate of resistive acceleration ear as a function of an acceleration amr measured at the driving wheels, of a theoretical acceleration atv that the vehicle V would have if it were traveling on a flat traffic lane with a predefined mass, and of a braking deceleration dfv experienced by the vehicle V.

[0044] Step 10-50 of the method also comprises a sub-step 50 in which one (for example the control device DC2) determines the torque setpoint cc as a function of the sum of a first acceleration setpoint cal defining the acceleration that the GMP must provide at the level of the drive wheels and the resistive acceleration estimate ear determined in sub-step 20.

[0045] By taking into account the braking deceleration of the vehicle V in this way, the calculation of the resistive acceleration estimate ear during a braking phase is very precise and not overestimated. As a result, the torque setpoint cc determined in sub-step 50 is adapted to the current situation, and therefore does not risk inducing unnecessary downshifts in the gearbox BV, in particular when overtaking another vehicle. This results in maintaining driving pleasure during the braking phases, in particular in terms of longitudinal acceleration.

[0046] For example, the braking deceleration dfv can be determined as a function of at least one physical quantity measured or estimated by at least one sensor on board the vehicle V and / or a percentage of depression of the brake pedal of the vehicle V.

[0047] Also for example, and as illustrated non-limitingly in [Fig. 3], the method can also comprise a sub-step 10 in which one (for example the control device DC2) can detect a start of braking when the pressure observed or measured in a master cylinder of the braking system of the vehicle V becomes greater than a chosen threshold. For example, this threshold can be between 0.3 bar and 0.5 bar. Also for example, this threshold can be variable to take into account a hysteresis effect.

[0048] In this case, as long as the pressure observed or measured in the master cylinder is lower than the chosen threshold, it is considered that the vehicle V is not in a braking phase, and therefore the resistive acceleration estimate ear is conventionally determined in a sub-step 30 of step 10-50 described later. On the other hand, when the observed or measured pressure in the master cylinder is greater than the chosen threshold, it is considered that the vehicle V is in a braking phase, and therefore the resistive acceleration estimate ear is determined in sub-step 20. This resistive acceleration estimate ear is then used to calculate the torque setpoint cc in sub-step 50.

[0049] In an alternative embodiment, one (for example the control device DC2) can detect the start of braking in the event of reception of a signal emitted by an “all or nothing” type sensor associated with the brake pedal of the vehicle V (it will be understood that such a signal is emitted when the percentage of depression of the brake pedal exceeds a predefined value).

[0050] Also for example, in sub-step 20 of step 10-50 one (for example the control device DC2) can determine the estimate of resistive acceleration ear in a braking phase by subtracting the measured acceleration amr and braking deceleration dfv from the theoretical acceleration atv. In this case, one has the relation ear = atv -amr - dfv. But other modes of determining the estimate of resistive acceleration ear can be envisaged as long as they use at least the measured acceleration amr, the theoretical acceleration atv and the braking deceleration dfv.

[0051] As indicated above, step 10-50 may comprise a sub-step 30 in which one (for example the control device DC2) may determine each estimate of resistive acceleration ear outside of a braking phase by subtracting the measured acceleration amr from the theoretical acceleration atv. In this case, we have the relationship ear = atv - amr. It will be understood that in this case the braking deceleration dfv is zero because we are outside of a braking phase.

[0052] Also for example, and as illustrated non-limitingly in [Fig.3], step 10-50 of the method can also comprise a sub-step 40 in which one (for example the control device DC2) can determine the first acceleration setpoint cal by subtracting a speed setpoint cv from a current actual speed vrv of the vehicle V. In this case, one has the relationship cal = vrv - cv.

[0053] Also for example, the speed instruction cv can be provided by the driving assistance function FAC. But it can have another origin. Thus, it can, for example, have been provided by the driver of the vehicle V.

[0054] Also for example, the theoretical acceleration atv can be determined as a function of the actual speed vrv, by means of at least one equation or within a stored correspondence table.

[0055] It will be noted that in sub-step 50 of step 10-50 one (for example the control device DC2) can determine a second setpoint ca2, defining the total acceleration to be provided by the GMP at the driving wheels, by summing the first acceleration setpoint cal and the resistive acceleration estimate ear dé completed in sub-step 20 or 30 (we then have the relation ca2 = cal + ear). In this case, in sub-step 50, we (for example the control device DC2) can then convert this second total acceleration setpoint ca2 into a torque setpoint cc. The latter (cc) is then transmitted to the supervision computer CS (for example via the internal communication network RC).

[0056] It will also be noted that the method according to the invention may possibly be implemented only when, as illustrated in [Fig.l], the vehicle V comprises a driving assistance function FAC controlling at least some of its movements during an autonomous driving phase (at least partial). In this case, in sub-step 20 the resistive acceleration estimate ear is determined as a function of the measured acceleration amr, theoretical acceleration atv and braking deceleration dfv only on condition that the vehicle V is in a braking phase during an autonomous driving phase (at least partial) controlled by the driving assistance function FAC.

[0057] However, it is possible to envisage that the method is systematically implemented in the vehicle V, whether the latter (V) includes or does not include a driving assistance function FAC or whether it includes an activated or inactivated driving assistance function FAC.

[0058] It will also be noted, as illustrated non-limitingly in [Fig. 2], that the driving assistance computer CF (or the computer of the control device DC2) may also comprise a mass memory MM1, in particular for storing the braking deceleration dfv, the measured acceleration amr, the theoretical acceleration atv, the speed setpoint cv and the actual speed vrv, as well as any intermediate data involved in all its calculations and processing. Furthermore, this driving assistance computer CF (or the computer of the control device DC2) may also comprise an input interface IE for receiving at least the braking deceleration dfv, measured acceleration amr, theoretical acceleration atv, speed setpoint cv and actual speed vrv, possibly after having shaped and / or demodulated and / or amplified them, in a manner known per se, by means of a digital signal processor PR2.In addition, this CF driving assistance calculator (or the DC2 control device calculator) can also include an IS output interface, in particular to deliver each message containing the determined cc torque instruction.

[0059] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the electronic circuit (or hardware) type, such as for example the processor PR1, is capable of implementing the control method described above to very precisely control the setpoint of cc torque defining the torque to be supplied by the GMP of the land vehicle V to the drive wheels of the latter (V), at least during braking phases.

Claims

Claims

1. Control method for a land vehicle (V) comprising a powertrain capable of supplying to drive wheels a torque as a function of a torque setpoint, said method comprising a step (10-50) in which said torque setpoint is determined as a function of a sum of a first acceleration setpoint to be supplied at said drive wheels and an estimate of a resistive acceleration undergone by said vehicle (V), characterized in that in said step (10-50), when said vehicle (V) is in a braking phase, said estimate of resistive acceleration is determined as a function of an acceleration measured at said drive wheels, of a theoretical acceleration that said vehicle (V) would have if it were traveling on a flat traffic lane having a predefined mass, and of a braking deceleration undergone by said vehicle (V).

2. Method according to claim 1, characterized in that in said step (10-50) said estimate of resistive acceleration in a braking phase is determined by subtracting said acceleration measured at said drive wheels and braking deceleration from said theoretical acceleration.

3. Method according to claim 1 or 2, characterized in that in said step (10-50) each estimate of resistive acceleration outside of a braking phase is determined by subtracting said acceleration measured at said drive wheels from said theoretical acceleration.

4. Method according to one of claims 1 to 3, characterized in that in said step (10-50) said first acceleration setpoint is determined by subtracting a speed setpoint from an actual current speed of said vehicle (V).

5. Method according to one of claims 1 to 4, characterized in that in said step (10-50) a second total acceleration setpoint is determined to be provided by said powertrain at said drive wheels by summing said first acceleration setpoint and resistive acceleration estimate, then this second total acceleration setpoint is converted into said torque setpoint.

6. Method according to one of claims 1 to 5, characterized in that in said step (10-50), when said vehicle (V) comprises a function driving assistance system capable of controlling movements of said vehicle (V) during an autonomous driving phase, said resistive acceleration estimate is determined as a function of said acceleration measured at said drive wheels, theoretical acceleration and braking deceleration when said vehicle (V) is in a braking phase during an autonomous driving phase.

7. Computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the control method according to one of claims 1 to 6, in a land vehicle (V) comprising a powertrain capable of supplying drive wheels with a torque as a function of a torque setpoint, in order to control said torque setpoint.

8. Control device (DC2) for a land vehicle (V) comprising a powertrain suitable for supplying drive wheels with a torque as a function of a torque setpoint, said device (DC2) comprising at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting of determining said torque setpoint as a function of a sum of a first acceleration setpoint to be supplied to said drive wheels and an estimate of a resistive acceleration undergone by said vehicle (V), characterized in that said processor (PR1) and memory (MD) are further arranged to carry out the operations consisting, when said vehicle (V) is in a braking phase, of determining said estimate of resistive acceleration as a function of an acceleration measured at said drive wheels,of a theoretical acceleration that said vehicle (V) would have if it were traveling on a flat traffic lane with a predefined mass, and of a braking deceleration experienced by said vehicle (V).,

9. Land vehicle (V) comprising a powertrain capable of supplying drive wheels with torque as a function of a torque setpoint, characterized in that it further comprises a control device (DC) according to claim 8.

10. Land vehicle according to claim 9, characterized in that it further comprises a driving assistance function capable of controlling movements of said vehicle (V) during an autonomous driving phase.

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