Very precise control of the torque setpoint of the powertrain of a land vehicle during a braking phase

Abstract

A control method is implemented in a vehicle comprising a powertrain suitable for providing drive wheels with a torque that is a function of a torque setpoint. This method comprises a step (10-50) in which the torque setpoint is determined as a function of a sum of a first acceleration setpoint to be provided at the drive wheels and of an estimation of a resistive acceleration experienced by the vehicle which, when the latter is in a braking phase, is a function of an acceleration measured at the drive wheels, of a theoretical acceleration that the vehicle would have if it circulated on a flat traffic lane while having a predefined mass, and of a braking deceleration experienced by the vehicle.

Description

DESCRIPTION TITLE: VERY PRECISE CONTROL OF THE TORQUE REFERENCE OF A LAND VEHICLE'S POWERTRAIN DURING A BRAKING PHASE The present invention claims priority from French application No. 2302808 filed on 24.03.2023, the content of which (text, drawings and claims) is incorporated herein by reference. Technical field of the invention

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

[0002] Some land vehicles, possibly automobiles, include a powertrain (or PWM) arranged to supply their drive wheels with torque based on a predetermined torque setpoint (called the wheel torque setpoint). This torque setpoint is used to control the PWM's torque generators (namely each drive unit (thermal or electric) within it), and also to select the appropriate gear ratio in the automated transmission.

[0003] Generally, the torque setting is determined by combining a first setting, defining the acceleration to be provided by the powertrain at the drive wheels, and an estimate of a resistive acceleration representative of the resistive forces experienced by the vehicle at the given moment. Currently, each resistive acceleration estimate is determined by subtracting the actual measured acceleration at the drive wheels from the theoretical acceleration the vehicle would experience if traveling on a flat road with a predefined mass.

[0004] One drawback of this method for determining resistive acceleration estimates is that it leads to an overestimation of this resistance during braking phases. This results in an excessively high torque requirement, which then necessitates, for example, unnecessary downshifting when overtaking another vehicle. It's understandable that the vehicle's deceleration is incorporated into the resistive acceleration estimate, leading to an overestimation and a reduction in driving pleasure, particularly in terms of longitudinal acceleration.

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

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

[0007] This control process is characterized by the fact that in its step, when the vehicle is in a braking phase, the resistive acceleration estimate is determined based on an acceleration measured at the drive wheels, a theoretical acceleration that the vehicle would have if it were traveling on a flat road with a predefined mass, and 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 vehicle's braking deceleration, and therefore there is no longer a risk of overestimating this resistive acceleration, which allows driving comfort to be maintained 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, we can determine the estimate of resistive acceleration in a braking phase by subtracting the acceleration measured at the level of the drive wheels and braking deceleration from the theoretical acceleration;

[0011] - in its step, we can determine each estimate of resistive acceleration outside of a braking phase by subtracting the acceleration measured at the level of 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 command by subtracting a speed command from an actual speed of the vehicle;

[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 we can convert this second total acceleration setpoint into a torque setpoint;

[0014] - in its stage, when the vehicle includes a driving assistance function to control vehicle movements during an autonomous driving phase (at least partial), the resistive acceleration estimate 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 proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing a control method of the type described above, in a land vehicle comprising a group a powertrain designed to provide drive wheels with torque based on 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 suitable for supplying drive wheels with 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 perform the operations consisting of determining this torque setpoint as a function of a sum of a first acceleration setpoint to be supplied at the level of the drive wheels and an estimate 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 perform the operations consisting, when the vehicle is in a braking phase, of determining the estimate of resistive acceleration based on an acceleration measured at the level of the drive wheels, a theoretical acceleration that the vehicle would have if it were traveling on a flat road with a predefined mass, and a braking deceleration suffered by the vehicle.

[0018] The invention also proposes a land vehicle comprising a powertrain capable of supplying drive wheels with 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 driver assistance function to control vehicle movements during a phase of autonomous driving (at least partial).

[0020] For example, this vehicle could also be a car. 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 example of an embodiment of a land vehicle comprising a thermal powertrain, a supervisory computer, a driver assistance computer and a control device according to the invention,

[0023] [Fig. 2] schematically and functionally illustrates an example of an embodiment of a supervisory computer comprising an example of an 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 the braking phases.

[0026] In what follows, we consider, by way of non-limiting example, that the land vehicle V is a motor vehicle. This is, for example, a car, as illustrated in Figure 1. However, the invention is not limited to this type of land vehicle. It relates to any type of land vehicle comprising a powertrain (or powertrain) capable of supplying the drive wheels with torque that is a function of a predetermined torque setting.

[0027] Figure 1 schematically represents a (land) vehicle V comprising, in particular, a transmission chain with a thermal engine MMT and a DC1 coupling device associated with a gearbox BV, a CS supervisory computer, and a DC2 control device according to the invention.

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

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

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

[0031] Since the powertrain is purely thermal, as an illustrative example, it includes a thermal drive unit (MMT) comprising a crankshaft (not shown) which is fixedly attached to the drive shaft (AM) to rotate the latter. This thermal drive unit (MMT) is designed to operate at a specific speed to provide a first torque c1, as instructed by the supervisory control unit (CS). Furthermore, it (MMT) is designed to be coupled to the primary shaft (AP) of the gearbox (BV) via the coupling device DC1. This device (DC1) is designed to deliver a second torque c2 from the first torque c1 produced by the thermal drive unit (MMT), specifically for at least one set of drive wheels (T1).

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

[0033] For example, the T1 axle can also be located in the front PW section of vehicle V. It is preferably, as illustrated, coupled to the AT driveshaft via a differential (here, the front one) DV. However, in a variant, this T1 axle could be the one referenced as T2, which is located in the rear PRV section of vehicle V.

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

[0035] It should be noted, as illustrated (but not limited to) in Figure 1, that the vehicle V may also, optionally, include a driver assistance control unit (CF) providing at least one driver assistance function (FAC) to control the vehicle V's movements during (at least partial) autonomous driving phases. For example, this FAC driver assistance function may be responsible for regulating the vehicle V's speed and the distance between vehicles (it is then often referred to by the English acronym ACC ("Adaptive Cruise Control")).

[0036] During autonomous driving controlled by the FAC (Front-Active Driving) system, the CS (Controller System) supervisory control unit sends the FAC at least one estimate of the torque supplied to the drive wheels by the powertrain and a minimum torque that the powertrain can deliver to the drive wheels. Upon receiving these torque and minimum torque estimates, the FAC determines a torque setpoint (cc) for the CS supervisory control unit. This setpoint defines the torque it wants the powertrain to deliver to the drive wheels, and it cannot be less than the minimum torque.

[0037] It should be noted that the CF driving assistance computer and the CS supervision computer can, for example, communicate via an internal RC communication network of the vehicle V, possibly multiplexed, as illustrated non-limitingly in Figure 1.

[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 vehicle's powertrain V to the drive wheels of the latter (V), at least during braking phases.

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

[0040] The MD memory is random access memory (RAM) to store instructions for the PR1 processor to implement at least part of the control process. The PR1 processor may include integrated circuits (or printed circuit boards), or several integrated circuits (or printed circuit boards) connected by wired or wireless connections. An integrated circuit (or printed circuit board) is defined as... any type of device capable of performing at least one electrical or electronic operation.

[0041] In the example illustrated (but not limited to) in Figures 1 and 2, the DC2 control unit is part of the CF driver assistance control unit. However, this is not mandatory. The DC2 control unit could have its own dedicated control unit, or it could be part of another control unit installed in the vehicle V (here, a vehicle) and performing at least one other function, such as the CS monitoring control unit.

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

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

[0044] Step 10-50 of the process also includes a substep 50 in which the torque setpoint cc is determined as a function of the sum of a first acceleration setpoint cal defining the acceleration that the GMP must provide at the drive wheels and the resistive acceleration estimate ear determined in substep 20.

[0045] Thanks to this consideration of vehicle V's braking deceleration, the calculation of the resistive acceleration estimate ear during a braking phase is very precise and not overestimated. Therefore, the torque setpoint cc determined in sub-step 50 is adapted to the current situation, and thus does not risk inducing unnecessary downshifts in the gearbox BV, particularly when overtaking another vehicle. This results in the maintenance of driving pleasure during braking phases, particularly 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 depressment of the brake pedal of the vehicle V.

[0047] For example, and as illustrated (but not limited to) in Figure 3, the method may also include a substep 10 in which a control device (e.g., DC2) can detect the onset of braking when the observed or measured pressure in a master cylinder of the vehicle's braking system (V) exceeds a chosen threshold. For example, this threshold may be between 0.3 bar and 0.5 bar. This threshold may also be variable to account for hysteresis.

[0048] In this case, as long as the observed or measured pressure in the master cylinder is below the chosen threshold, the vehicle V is considered not to be braking, and therefore the resistive acceleration estimate ear is determined conventionally in substep 30 of step 10-50 described later. Conversely, when the observed or measured pressure in the master cylinder is above the chosen threshold, the vehicle V is considered to be braking, and therefore the resistive acceleration estimate ear is determined in substep 20. This resistive acceleration estimate ear is then used to calculate the torque setpoint cc in substep 50.

[0049] In one embodiment, one (for example the DC2 control device) can detect the start of braking in the event of receiving a signal emitted by an "on or off" type sensor associated with the brake pedal of vehicle V (it will be understood that such a signal is emitted when the percentage of depressment of the brake pedal exceeds a predefined value).

[0050] Also, for example, in substep 20 of step 10-50, one (for example, the DC2 control device) can determine the estimate The resistive acceleration (ear) during braking is calculated by subtracting the measured acceleration (amr) and braking deceleration (dfv) from the theoretical acceleration (atv). In this case, the relationship is: ear = atv - amr - dfv. However, other methods for estimating the resistive acceleration (ear) can be considered, provided they use at least the measured acceleration (amr), the theoretical acceleration (atv), and the braking deceleration (dfv).

[0051] As mentioned above, step 10-50 may include a substep 30 in which one (for example, the DC2 control device) can determine each estimate of resistive acceleration ear outside of a braking phase by subtracting the measured acceleration arm from the theoretical acceleration atv. In this case, we have the relationship ear = atv - arm. 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 Figure 3, step 10-50 of the process can also include a substep 40 in which one (for example the control device DC2) can determine the first acceleration setpoint cal by subtracting a speed setpoint cv from an actual speed vrv during the vehicle V. In this case, we have the relationship cal = vrv - cv.

[0053] For example, the speed setting (cv) can also be provided by the FAC driver assistance function. However, it can also have another origin. For instance, it could have been provided by the driver of vehicle V.

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

[0055] Note 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 powertrain at the drive wheels, by summing the first acceleration setpoint cal and the resistive acceleration estimate ear determined in sub-step 20 or 30 (we then have the relationship ca2 = cal + ear). In In this case, in substep 50, one (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 supervisory computer CS (for example, via the internal communication network RC).

[0056] It should also be noted that the method according to the invention can potentially be implemented only when, as illustrated in Figure 1, the vehicle V includes a driver assistance function FAC controlling at least some of its movements during an autonomous driving phase (at least partial). In this case, in substep 20, the resistive acceleration estimate ear is determined as a function of the measured acceleration amr, theoretical acceleration atv, and braking deceleration dfv only if the vehicle V is in a braking phase during an autonomous driving phase (at least partial) controlled by the driver assistance function FAC.

[0057] But it is conceivable that the process is systematically implemented in vehicle V, whether the latter (V) includes or does not include a FAC driver assistance function or whether it includes an activated or deactivated FAC driver assistance function.

[0058] It should also be noted, as illustrated (but not limited to) in Figure 2, that the driver assistance control unit CF (or the control unit DC2) may also include a mass storage device MM1, specifically for storing the braking deceleration dfv, the measured acceleration arm, the theoretical acceleration atv, the speed setpoint cv, and the actual speed vrv, as well as any intermediate data involved in its calculations and processing. Furthermore, this driver assistance control unit CF (or the control unit DC2) may also include an input interface IE for receiving at least the braking deceleration dfv, measured acceleration arm, theoretical acceleration atv, speed setpoint cv, and actual speed vrv, possibly after having been shaped and / or demodulated and / or amplified, in a manner known per se, by means of a digital signal processor PR2.Furthermore, this CF driver assistance computer (or the device computer). DC2 control) may also include an IS output interface, notably to deliver each message containing the determined DC torque setpoint.

[0059] It should 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 type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the control method described above to control very precisely the torque setpoint cc 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 the 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 with 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 driving assistance function 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 at 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 a 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 which further comprises a driving assistance function capable of controlling the movements of said vehicle (V) during an autonomous driving phase.

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