DETERMINATION OF A VEHICLE REFERENCE SPEED FOR A DRIVER ASSISTANCE FUNCTION

Abstract

A method is implemented in a vehicle comprising a powertrain providing torque to two front drive wheels of a front-wheel drive axle and / or two rear drive wheels of a rear-wheel drive axle, each wheel having a travel speed, and a driving assistance function using a reference vehicle speed. This method includes a step (10-40) in which: - for each drive axle, a first value is determined equal to half the sum of the available travel speeds of its drive wheels, each unavailable travel speed being replaced by a zero value, then a second value is determined equal to the product of a percentage of the torque supplied to the drive axle in question and a maximum value between the first value determined for the latter and an auxiliary vehicle speed, and - the reference speed is determined by summing the second set of values. Figure 3

Description

Title of the invention: DETERMINATION OF A REFERENCE SPEED OF A VEHICLE FOR A DRIVER ASSISTANCE FUNCTION Technical field of the invention

[0001] The invention relates to land vehicles comprising at least one drive train having two drive wheels and at least one driving assistance function using a reference speed, and more specifically the determination of this reference speed within such vehicles. State of the art

[0002] Some land vehicles (generally of the automobile type) include a powertrain (or PWM) capable of providing torque for two front drive wheels of a front drive axle and / or two rear drive wheels of a rear drive axle, and at least one driver assistance function (or AD AS (“Advanced Driver Assistance System”)).

[0003] For example, a driver assistance function may be:

[0004] - a speed and distance control system between vehicles (or ACC (“Adaptive”) Cruise Control"),

[0005] - a simple speed regulator (or RW (“Vehicle Speed ​​Regulator”)),

[0006] - a speed limiter (or LVV (“Vehicle Speed ​​Limiter”)),

[0007] - a speed limiting device (or VLD ("Vehicle Speed ​​Limiter") - security function)), or

[0008] - an automatic parking assistance device (or CPK (“Control ParKing” "))•

[0009] Each driving assistance function is arranged to interact with the GMP for speed management and / or longitudinal acceleration needs by imposing either a maximum torque (particularly in the case of the LVV and BVV functions), or a minimum torque (particularly in the case of the ACC and RW functions), or by imposing a setpoint torque (particularly in the case of the CPK function).

[0010] The so-called "xVV" functions (namely LVV, BVV and RW) use a reference vehicle speed which is currently determined in three different ways, depending on whether only the front axle is driven (traction), only the rear axle is driven (propulsion), or both the front and rear axles are driven (4x4).

[0011] In the first way (traction) the reference speed is equal to half the sum of the speeds of movement of the front drive wheels (which are provided by sensors associated respectively with the two front drive wheels).

[0012] In the second method (propulsion) the reference speed is equal to half the sum of the speeds of movement of the rear drive wheels (which are provided by sensors associated respectively with the two rear drive wheels).

[0013] In the third way (4x4) the reference speed is equal to the sum, on the one hand, of a first product of a first percentage of the torque supplied to the front drive axle and half the sum of the speeds of movement of the front drive wheels, and, on the other hand, of a second product of a second percentage of the torque supplied to the rear drive axle and half the sum of the speeds of movement of the rear drive wheels.

[0014] This method of determination was initially chosen to prevent the occurrence of a runaway of a drive train in the event of slippage of drive wheel(s), and especially because it is the engine torque supplied to each drive train that is controlled by an ADAS function and therefore the speed information must be the speeds of movement of the drive wheels concerned.

[0015] However, this method of determination can pose a problem, or even prove dangerous, in certain real-life situations, particularly when one or more wheel sensors malfunction and therefore no longer provide a speed reading or provide an aberrant speed reading. This is due in particular to the fact that, in order for certain vehicle functions to remain available (such as the automatic engine shut-off function (or "start & stop")), it is necessary to require that each unavailable speed reading (not provided or aberrant) be set to zero (0 km / h).

[0016] It will be understood that by applying this last rule, the reference speed is halved, which prevents certain ADAS functions from maintaining a target speed. It is then necessary to deactivate all ADAS functions except the BVV function, since this is a safety function that protects against overspeeding to prevent risks of fire, tire blowout, or component failure. However, prohibiting the deactivation of the BVV function in the event of a failure of at least one wheel sensor can be potentially dangerous. Indeed, if the vehicle's speed is limited to 135 km / h by the BVV function, the driver will have to wait until the vehicle reaches a speed of 270 km / h for the speed limitation to become effective, since the reference speed is approximately half the vehicle's actual speed.

[0017] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0018] In particular, it proposes for this purpose a method for enabling the in situ determination of a reference speed of a land vehicle and comprising:

[0019] - a powertrain (or powertrain) designed to provide torque for two wheels two front drive wheels of a front-wheel drive system and / or two rear drive wheels of a rear-wheel drive system, each wheel being associated with a sensor specific to determining its speed, and

[0020] - at least one driver assistance function using this reference speed.

[0021] This determination method is characterized by the fact that it includes a step in which :

[0022] - for each drive train, a first value equal to half- is determined sum of the available travel speeds of its drive wheels, each unavailable travel speed being replaced by a zero value, then a second value equal to the product of a percentage of the torque supplied to the drive train in question and a maximum value between the first value determined for the latter and an auxiliary speed of the vehicle, and

[0023] - the reference speed is determined by summing these second values determined.

[0024] Thanks to the invention, as long as there are fewer than three faulty sensors (and therefore fewer than three unavailable travel speeds), a sufficiently precise reference speed is available and therefore usable by an AD AS function, and consequently the availability of the vehicle is maximized because the AD AS limiting function (BVV) remains operational.

[0025] The determination method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0026] - in a first embodiment, in its stage, in the presence of a front axle engine and a non-driven rear axle (traction), we can determine a first value equal to half the sum of the available travel speeds of the front drive wheels, then a second value equal to the maximum value between the first value determined and the auxiliary speed, and we can consider that the reference speed is this second determined value;

[0027] - in a second embodiment, in its step, in the presence of a train front non-motorized and rear motorized (propulsion) axle, we can determine a first value equal to half the sum of the available travel speeds of the rear drive wheels, then a second value equal to the maximum value between this first determined value and the auxiliary speed, and we can consider that the reference speed is this second determined value;

[0028] - in a third embodiment, in its stage, in the presence of a train front motor and rear motor (4x4), we can determine a first value equal to half the available travel speeds of the front drive wheels, and a first second value equal to the product of a first percentage of the torque supplied to the front motor and a first maximum value between this first determined value and the auxiliary speed, we can determine a second first value equal to half the available travel speeds of the rear drive wheels, and a second second value equal to the product of a second percentage of the torque supplied to the rear motor and a second maximum value between this second determined value and the auxiliary speed, and we can determine the reference speed by summing these first and second determined values;

[0029] - in its step, the auxiliary speed can be equal to a sum of the speeds available movement speeds divided by a number of available movement speeds;

[0030] - in the presence of the last option, in its step, when the number of speeds If the number of available travel spaces is strictly less than two, an alarm can be triggered requiring the vehicle to stop, addressed to at least one driver of the vehicle;

[0031] - Alternatively, in its step, the auxiliary speed may be equal to a speed of vehicle's cash value estimated using successive vehicle positions provided by a geolocation device present in the vehicle.

[0032] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing a determination method of the type presented above, in a vehicle comprising a powertrain (or PWM) suitable for providing torque for two front drive wheels of a front drive axle and / or two rear drive wheels of a rear drive axle, each wheel being associated with a sensor suitable for determining its speed of movement, and at least one driving assistance function using a reference speed of the vehicle, to determine this reference speed.

[0033] The invention also proposes a determination device for equipping a vehicle comprising:

[0034] - a powertrain (or powertrain) capable of providing torque for two wheels two front drive wheels of a front-wheel drive system and / or two rear drive wheels of a rear-wheel drive system, each wheel being associated with a sensor specific to determining its speed, and

[0035] - at least one driver assistance function using this reference speed.

[0036] This determination device is characterized in that it comprises at least one processor and at least one memory arranged to perform the operations consisting of:

[0037] - for each drive train to be determined a first value equal to half- sum of the available travel speeds of its drive wheels, each unavailable travel speed being replaced by a zero value, then a second value equal to the product of a percentage of the torque supplied to the drive train in question and a maximum value between the first value determined for the latter and an auxiliary speed of the vehicle, and

[0038] - to determine the reference speed by summing these second values determined.

[0039] The invention also proposes a land vehicle, possibly of the automobile type, comprising:

[0040] - a powertrain (or powertrain) capable of supplying torque to two wheels two front drive wheels of a front-wheel drive system and / or two rear drive wheels of a rear-wheel drive system, each wheel being associated with a sensor specific to determining its speed of movement,

[0041] - at least one driver assistance function using this reference speed, and

[0042] - a determination device of the type of that presented above. Brief description of the figures

[0043] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0044] [Fig. 1] schematically and functionally illustrates an example of an embodiment of a vehicle comprising a determination device according to the invention, and a powertrain associated with a supervisory computer and comprising first and second electric drive machines and associated respectively with first and second independent drive trains,

[0045] [Fig.2] schematically and functionally illustrates an example of an embodiment of a supervisory computer comprising an example of an embodiment of a determination device according to the invention, and

[0046] [Fig.3] schematically illustrates an example of an algorithm implementing a determination method according to the invention. Detailed description of the invention

[0047] The invention aims in particular to propose a method of determination, and an associated determination device DD, intended to allow the determination of a reference speed vref which is used by at least one driving assistance function (or AD AS) of a land vehicle V.

[0048] In what follows, the land vehicle V is considered, by way of non-limiting example, to be of the automobile type. This is, for example, a car, as illustrated in [Fig. 1]. However, the invention is not limited to this type of land vehicle. It relates in fact to any type of land vehicle comprising a powertrain (or powertrain) including at least one drive machine capable of supplying engine torque to at least one drive train.

[0049] Furthermore, in what follows, by way of non-limiting example, the powertrain is considered to be purely electric (and therefore includes at least one electric drive unit). However, the powertrain could be hybrid (for example, thermal and electric).

[0050] Furthermore, in the following, by way of non-limiting example, the electric powertrain is considered to comprise first MM1 and second MM2 electric drive machines supplied with electrical energy by a low-pressure (LP) power source constituting a rechargeable (at least during charging) power (or "main" or "traction") battery. However, the first MM1 and second MM2 electric drive machines could be supplied with electrical energy by a fuel cell (for example, a hydrogen fuel cell).

[0051] Finally, in what follows, by way of non-limiting example, it is assumed that the first MM1 and second MM2 electric drive units are respectively associated with front axles T1 and rear axles T2 motors, and therefore the transmission chain allows for a four-wheel drive (or 4x4) mode. However, the first MM1 and second MM2 electric drive units could be associated with the same front axle T1 or rear axle T2 motor (and in this case the transmission chain only allows for a two-wheel drive (traction or propulsion) mode).

[0052] A (land) vehicle V comprising a purely electric GMP transmission chain (and therefore comprising (here) first MM1 and second MM2 electric driving machines), an on-board network RB, a service battery BS, an electrical power supply source (here a power (or main or traction) battery) BP, a converter CV, a supervisory computer CS, first CM1 and second CM2 machine computers, and a determination device DD according to the invention, is schematically represented in [Fig.1].

[0053] The CV converter is of the DC / DC type (“Direct Current / Direct Current”). It is therefore responsible for converting a direct current from a first voltage to a second voltage.

[0054] The RB on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0055] The auxiliary battery BS is responsible for supplying electrical energy to the on-board network RB, in addition, in this case, to that supplied by the converter CV powered by the The power supply (BP) is provided via a power grid, and sometimes, in this case, instead of the CV converter. For example, this service battery (BS) can be configured as a very low voltage battery (typically 12 V, 24 V, or 48 V). It is rechargeable, at least by the CV converter. In the following, we will assume, as a non-limiting example, that the service battery (BS) is a 12 V lithium-ion type.

[0056] The transmission chain has a GMP which is, here, purely electric and therefore which includes, in particular, first MM1 and second MM2 (electric) drive machines, first AMI and second AM2 drive shafts, and first ATI and second AT2 transmission shafts.

[0057] Here, "electric motor machine" means an electric machine arranged to provide a motor torque cmj (j = 1 or 2), defined by a torque setpoint cgj, to move the vehicle V when it is supplied with electrical energy (here) by the electrical power supply source BP (this is referred to as supplying a positive output torque), and possibly to recover regenerative braking torque cfr to decelerate the vehicle V (this is referred to as supplying a negative output torque).

[0058] The operation of the powertrain is supervised by a supervisory computer CS. The control of the first power unit MM1 is ensured by an associated first machine computer CM1, notably based on a first setpoint cgi (j = 1) provided by the supervisory computer CS, defining the first motor torque cml (j = 1) that the latter (CS) wants the first power unit MM1 to supply. The control of the second power unit MM2 is ensured by an associated second machine computer CM2, notably based on a second setpoint cg2 (j = 2) provided by the supervisory computer CS, defining the second motor torque cm2 (j = 2) that the latter (CS) wants the second power unit MM2 to supply.

[0059] It should be noted that the second machine computer CM2 and the supervisory computer CS communicate with each other, for example via a vehicle communication network V, possibly multiplexed. This communication allows, in particular, the supervisory computer CS to transmit to the second machine computer CM2 the second torque command cg2 (defining the second motor torque cm2 to be supplied) or a message ordering it to stop operating the second power machine MM2, and for the second machine computer CM2 to transmit status information to the supervisory computer CS.

[0060] The first drive machine MM1 is coupled to the first motor shaft AMI, to provide it with a first motor torque cml (defined by the first setpoint cgi) by rotational drive when it is (here) supplied with electrical energy by the power supply source BP via the power grid. This first shaft The AMI motor is here coupled to an RD reducer which is also coupled to the first ATI transmission shaft, itself coupled to a first Tl motor train and comprising right-hand drive wheels R1D and left-hand drive wheels R1G, preferably via a first differential DV.

[0061] It should be noted that the first (motor) assembly T1 is located here in the front PVV section of the vehicle V, and is therefore referred to hereafter as the front assembly. However, in a variant, this first assembly T1 could be the second (motor) assembly T2, which is located in the rear PRV section of the vehicle V.

[0062] The front right drive wheel R1D is associated with a front right sensor C1D designed to determine its travel speed vdld. The front left drive wheel R1D is associated with a front left sensor CIG designed to determine its travel speed vdlg.

[0063] The second drive machine MM2 is coupled to the second drive shaft AM2 to provide it with a second drive torque cm2 (defined by the second setpoint cg2) by rotational drive when it is (here) supplied with electrical energy by the power supply BP via the power grid. This second drive shaft AM2 is coupled to a DC coupling device which is also coupled to the second transmission shaft AT2, itself coupled to the second drive axle (or rear axle) T2 and comprising right-hand drive wheels R2D and left-hand drive wheels R2G, preferably via a second differential DR.

[0064] The second drive machine MM2 can also, optionally, be arranged to recover regenerative braking torque to decelerate the vehicle V. This regenerative braking torque, which is defined by a deceleration setpoint, can then be transformed into current intended to recharge the electrical power supply source BP (when it is a rechargeable battery and this is possible at the time considered).

[0065] The DC coupling device is arranged to couple or decouple the second power unit MM2 from the second drive shaft AT2, according to the requirements defined by the supervisory computer CS (and reported to the second machine computer CM2). For example, this DC coupling device could be a clutch (possibly hydraulic). But it could also be a dog clutch, for example. This DC coupling device can therefore be in an open state in which it (completely) decouples the second power unit MM2 from the second axle (or rear axle) T2, and at least one state other than open (for example, closed or slipping) in which it at least partially couples the second power unit MM2 to the second axle (or rear axle) T2. The open state and each state other than open constitute state information. It is assumed here that the second machine computer CM2 controls the state in which the DC coupling device is placed.But this. The final check could be performed by a computer dedicated to the DC coupling device.

[0066] The right rear drive wheel R2D is associated with a right rear sensor C2D which determines its speed vd2d. The left rear drive wheel R2D is associated with a left rear sensor C2G which determines its speed vd2g.

[0067] It will be noted that when the vehicle V comprises only one drive train Tj (j = 1 (front) or 2 (rear)) the wheels Rj'D and Rj'G (non-drive) of the other train Tj' (non-drive) are also associated respectively with right sensors Cj'D and left sensors Cj'G suitable for determining their travel speeds vdj'd and vdj'g.

[0068] The power supply BP here is a power (or main or traction) battery which may, for example, include electrical energy storage cells, possibly electrochemical (for example, lithium-ion (or Li-ion) or Ni-MH or Ni-Cd type). Also, for example, the power supply BP may be of the low-voltage type (typically 450 V by way of illustration). But it could also be of the medium-voltage or high-voltage type.

[0069] The CV converter is also responsible, here, during the driving phases of the vehicle V, for converting part of the electrical current stored in the electrical power supply BP to supply converted electrical current to the on-board network RB and the auxiliary battery BS (to recharge it).

[0070] It will be noted, as illustrated non-limitingly in [Fig.1], that the CV converter can be part of a CH charger responsible for controlling the recharging of the BP power supply source.

[0071] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], the vehicle V also includes a distribution box BD to which the auxiliary battery BS, the converter CV, and the on-board network RB are coupled. This distribution box BD is responsible for distributing the electrical energy stored in the auxiliary battery BS or produced by the converter CV into the on-board network RB to power the electrical components (or equipment) connected to the on-board network RB, according to power demands received (in particular from the powertrain control unit CS).

[0072] The vehicle V also includes at least one driver assistance function (or ADAS) using a reference speed vref, which must be determined in situ and representative of the actual speed of the vehicle V. For example, the vehicle V may include at least one ADAS function computer (CFA) controlling at least one ADAS function. For example, each ADAS function using a reference speed vref may be an xVV function (namely LVV (speed limiter), BVV (speed restriction device), or RW (cruise control)).

[0073] As mentioned above, the invention proposes in particular a determination method intended to allow the determination of the reference speed vref which is used by at least one AD AS function of the vehicle V controlled by the AD AS CFA function computer.

[0074] This (determination) method can be implemented at least partially by the determination device DD (illustrated at least partially in Figures 1 and 2), which comprises for this purpose at least one processor PR1, for example a digital signal processor (or DSP), and at least one memory MD. This determination device DD can therefore be implemented in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). By way of example, it could be a microcontroller.

[0075] The MD memory is random access memory (RAM) to store instructions for the implementation by the PR1 processor of at least part of the determination process. The PR1 processor may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is defined as any type of device capable of performing at least one electrical or electronic operation.

[0076] In the example illustrated, but not limited to, Figures 1 and 2, the DD determination device is part of the CS supervisory computer. However, this is not mandatory. Indeed, the DD determination device could comprise its own dedicated computer, which could then be coupled to the CS supervisory computer, or it could be part of another computer embedded in the vehicle V and performing at least one other function, such as the AD AS CFA function computer.

[0077] As illustrated non-limitingly in [Fig.3], the method (of determination), according to the invention, includes a step 10-40 which is implemented each time the reference velocity vref is to be determined.

[0078] Step 10-40 of the process includes a substep 10 in which a first value vlj is determined for each drive train Tj (j = 1 or 2), which is equal to half the sum of the available travel speeds vdjd and vdjg of its drive wheels, i.e. vlj = (vdjd + vdjg) / 2. It should be noted that when a travel speed is unavailable (because it is not supplied or is aberrant), it is replaced by a zero value (0 km / h).

[0079] Step 10-40 of the method also includes a substep 20 in which a second value v2j is determined for each drive train Tj (j = 1 or 2). This second value v2j is equal to the product of the percentage pcj of the torque cmj supplied to the drive train Tj in question and a maximum value vmaxj between the first value vlj determined for the latter (Tj) and an auxiliary speed vav. of vehicle V, let v2j = pcj * vmaxj, with vmaxj = max[vlj, vav]. Note that the percentage pcj is a value between 0 and 1, and pc2 = 1 - pci. The value pcj = 0 corresponds to the case where train Tj is not powered, and the value pcj = 1 corresponds to the case where only train Tj is powered. Furthermore, it is understood that when pcj = 0, the corresponding second value v2j is zero (v2j = 0).

[0080] Step 10-40 of the process also includes a substep 30 in which the reference velocity vref is determined (for example by the determination device DD) by summing the second values ​​v2j determined, i.e. vref = v21 + v22 = (pci * max[vll, vav]) + (pc2 * max[vl2, vav]).

[0081] Thus, as long as there are fewer than three faulty sensors CjD and CjG (and therefore fewer than three unavailable travel speeds vdjd and vdjg), a reference speed vref is available that is sufficiently accurate and therefore usable by an ADAS function. The availability of vehicle V is thus maximized, because the ADAS speed limiting function (BVV) remains operational.

[0082] Three embodiments of the process (and therefore also of the DD determination device) can be envisaged, depending on whether the vehicle V moves by traction, propulsion, or four-wheel drive (or 4x4) mode.

[0083] In the first embodiment (traction: front axle T1 driven and rear axle T2 undriven), in substep 10 of step 10-40, a first value vil can be determined (for example, by the determination device DD), equal to half the sum of the available travel speeds vdld and vdlg of the front right drive wheel R1D and left drive wheel R1G, i.e., vl1 = vdld + vdlg. It should be noted that it is not necessary to determine the other first value vl2 associated with the rear axle T2 because the percentage pc2 is equal to zero, and therefore the second associated value v22 is automatically zero.

[0084] Then, in substep 20 of step 10-40, a second value v21 can be determined (for example, by the determination device DD), which is equal to the maximum value vmaxl between the first determined value vil and the auxiliary speed vav, i.e., v21 = vmaxl, with vmaxl = max[vl 1, vav]. It is recalled that in the case of traction, the percentage pci is equal to one, and therefore the second value v21, defined by the product pci * vmaxl, is equal to vmaxl.

[0085] Then, in substep 30 of step 10-40, one (for example the determination device DD) can consider that the reference speed vref is the second value v21 determined, i.e. vref = v21. Indeed, we have v22 = 0 (because pc2 = 0) and therefore vref = v21 +v22 = v21.

[0086] In the second embodiment (propulsion: non-powered front axle T1 and powered rear axle T2), in substep 10 of step 10-40, a first value vl2 equal to half the sum of the available wheel travel velocities vd2d and vd2g can be determined (for example, by the determining device DD). The rear drive wheels are right R2D and left R2G, so vl2 = vd2d + vd2g. Note that it is not necessary to determine the other first value vil associated with the front axle Tl because the percentage pci is equal to zero and therefore the second associated value v21 is automatically zero.

[0087] Then, in substep 20 of step 10-40, a second value v22 can be determined (for example, by the determination device DD), which is equal to the maximum value vmax2 between the first determined value vl2 and the auxiliary speed vav, i.e., v22 = vmax2, with vmax2 = max[vl2, vav]. It should be noted that in the case of propulsion, the percentage pc2 is equal to one, and therefore the second value v22, defined by the product pc2 * vmax2, is equal to vmax2.

[0088] Then, in substep 30 of step 10-40, one (for example, the determination device DD) can consider that the reference velocity vref is the second value v22 determined, i.e., vref = v22. Indeed, we have v21 = 0 (because pci = 0) and therefore vref = v21 + v22 = v22.

[0089] In the third embodiment (4x4 mode: front axle T1 motor and rear axle T2 motor), in substep 10 of step 10-40, one (for example the determining device DD) can determine, on the one hand, a first first value vil equal to the half sum of the available travel speeds vdld and vdlg of the front drive wheels right R1D and left R1G, i.e. vl 1 = vdld + vdlg, and a second first value vl2 equal to the half sum of the available travel speeds vd2d and vd2g of the rear drive wheels right R2D and left R2G, i.e. vl2 = vd2d + vd2g.

[0090] Then, in substep 20 of step 10-40, one (for example the determination device DD) can determine, on the one hand, a first second value v21 which is equal to the product of a first percentage pci of the torque supplied to the front axle Tl engine and a first maximum value vmaxl between the first first value vil determined and the auxiliary speed vav, i.e. v21 = pci * vmaxl, with vmaxl = max[vl 1, vav], and on the other hand, a second second value v22 which is equal to the product of a second percentage pc2 of the torque supplied to the rear axle T2 engine and a second maximum value vmax2 between the second first value vl2 determined and the auxiliary speed vav, i.e. v22 = pc2 * vmax2, with vmax2 = max[vl2, vav].

[0091] Then, in substep 30 of step 10-40, one (for example the determination device DD) can determine the reference speed vref by performing the sum of the first v21 and second v22 second determined values, i.e. vref = v21 + v22.

[0092] It will be noted that in substep 20 of step 10-40, one (for example the determination device DD) can use an auxiliary velocity vav which is equal to the sum of the available displacement velocities vdjd and vdjg divided by the number nv of available displacement velocities vdjd and vdjg, i.e. vav = (S vdjd + vdjg) / nv.

[0093] It should also be noted that step 10-40 may include, as illustrated non-limitingly in [Fig. 3], a substep 40 in which, when the number nv of available travel speeds vdjd and vdjg is strictly less than two, i.e., nv < 2, one (for example, the determining device DD) may trigger the generation of an alarm requiring a (preferably immediate) stop of the vehicle V, addressed to at least the driver of the vehicle V. It will be understood that when at least three sensors CjD and CjG are faulty (and therefore there are at least three unavailable travel speeds vdjd and vdjg), it is no longer possible to determine the reference speed vref, and therefore it is essential to alert the driver so that he stops his vehicle V as quickly as possible.

[0094] The driver's alarm may be given by the illumination of a warning light (possibly dedicated) on the vehicle V (for example, on the instrument panel) or by the generation of at least one message. In the case of a message, this may be a text message displayed on at least one screen EA of the vehicle V (for example, on the instrument panel or a central instrument cluster) or on the screen of the driver's smartphone and / or an audible message broadcast by at least one speaker of the vehicle V or of that smartphone.

[0095] It should also be noted that in substep 40, one (for example the DD determination device) can also possibly prohibit the use of the (of each) ADAS function (at least non-safe).

[0096] In one variant, in substep 20 of step 10-40, one (for example the determination device DD) can use an auxiliary speed vav which is equal to a body speed of the vehicle V which is estimated by means of successive positions of the vehicle V provided by a geolocation device present in the vehicle V (permanently or temporarily (for example because it is fitted to the driver's smartphone)).

[0097] It should also be noted, as illustrated non-limitingly in [Fig. 2], that the CS supervisory computer (or the DD determination device computer) may also include a mass memory (MM), in particular to store at least the available travel speeds vdjd and vdjg and any percentages pcj, as well as any intermediate data involved in all its calculations and processing. Furthermore, this CS supervisory computer (or the DD determination device computer) may also include an IE input interface to receive at least the available travel speeds vdjd and vdjg and any percentages pcj for use in calculations or processing, possibly after having been shaped and / or demodulated and / or amplified, in a manner known per se, by means of a PR2 digital signal processor. In addition, this CS supervisory computer (or the DD determination device computer) may also include an IE input interface to receive at least the available travel speeds vdjd and vdjg and any percentages pcj for use in calculations or processing, possibly after having been shaped and / or demodulated and / or amplified, in a manner known per se, by means of a PR2 digital signal processor. DD determination) may also include an IS output interface, notably to deliver each message containing the determined vref reference speed, and each possible message requiring the generation of an alarm.

[0098] 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 type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the determination method described above to determine the reference speed vref which is used by at least one driver assistance function (or AD AS) of the vehicle V.

Claims

Demands

1. A method for determining a reference speed of a land vehicle (V) comprising i) a powertrain adapted to provide torque to two front drive wheels of a front drive axle (T1) and / or two rear drive wheels of a rear drive axle (T2), each wheel being associated with a sensor adapted to determine its travel speed, and ii) at least one driver assistance function using said reference speed, characterized in that it comprises a step (10-40) in which a) for each drive axle (T1, T2) is determined a first value equal to half the sum of the available travel speeds of its drive wheels, each unavailable travel speed being replaced by a zero value, and then a second value equal to the product of a percentage of said torque supplied to the drive axle (T1, T2) considered and a maximum value between the first value determined for the latter (T1,(t2) and an auxiliary speed of said vehicle (V), and (b) said reference speed is determined by summing said second determined values.

2. Method according to claim 1, characterized in that in said step (10-40), in the presence of a driven front axle (T1) and a non-driven rear axle (T2), said first value is determined equal to half the sum of the available travel speeds of the front drive wheels, then a second value is determined equal to said maximum value between said first determined value and said auxiliary speed, and b) said reference speed is considered to be said second determined value.

3. Method according to claim 1, characterized in that in said step (10-40), in the presence of a driven rear axle (T2) and a non-driven front axle (T1), said first value is determined to be equal to half the sum of the available travel speeds of the rear drive wheels, then a second value is determined to be equal to said maximum value between said first determined value and said auxiliary speed, and b) said reference speed is considered to be said second determined value.

4. The method according to claim 1, characterized in that in said step (10-40), in the presence of a driven front axle (T1) and a driven rear axle (T2), i) a first value is determined equal to half the sum of the available travel speeds of the front drive wheels, and a first second value equal to the product of a first percentage of the torque supplied to the front drive axle (T1) and a first maximum value between said first determined value and said auxiliary speed, ii) a second first value is determined equal to half the sum of the available travel speeds of the rear drive wheels, and a second second value equal to the product of a second percentage of the torque supplied to the rear drive axle (T2) and a second maximum value between said second determined value and said auxiliary speed, and iii) said reference speed is determined by summing said first and second determined values.

5. A method according to any one of claims 1 to 4, characterized in that in said step (10-40) said auxiliary speed is equal to a sum of the available travel speeds divided by a number of available travel speeds.

6. Method according to claim 5, characterized in that in said step (10-40) when said number of available travel speeds is strictly less than two, an alarm is triggered requiring a stop of said vehicle (V) addressed to at least one driver of said vehicle (V).

7. A method according to any one of claims 1 to 4, characterized in that in said step (10-40) said auxiliary speed is equal to a body speed of said vehicle (V) estimated by means of successive positions of said vehicle (V) provided by a geolocation device present in said vehicle (V).

8. Product computer program comprising an instruction set which, when executed by processing means, is suitable for implementing the determination method according to any one of claims 1 to 7, in a land vehicle (V) and comprising i) a powertrain suitable for providing torque for two front drive wheels of a front drive axle (T1) and / or two rear drive wheels of a rear drive axle (T2), each wheel being associated with a sensor suitable for determining its speed of movement, and ii) at least one driving assistance function using a reference speed of said vehicle (V), to determine this reference speed.

9. A determination device (DD) for a land vehicle (V) comprising i) a powertrain adapted to provide torque to two front drive wheels of a front drive axle (T1) and / or two rear drive wheels of a rear drive axle (T2), each wheel being associated with a sensor adapted to determine its speed of movement, and ii) at least one driving assistance function using said reference speed, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to perform the operations consisting of a) for each drive axle (T1, T2) of determining a first value equal to half the sum of the available speeds of its drive wheels, each unavailable speed of movement being replaced by a zero value, and then a second value equal to the product of a percentage of said torque supplied to the axle (T1,T2) engine considered and a maximum value between the first value determined for the latter (T1, T2) and an auxiliary speed of said vehicle (V), and b) to determine said reference speed by summing said second determined values.

10. Land vehicle (V) comprising i) a powertrain suitable for supplying torque to two front drive wheels of a front drive axle (T1) and / or two rear drive wheels of a rear drive axle (T2), each wheel being associated with a sensor suitable for determining its speed of movement, and ii) at least one driving assistance function using said reference speed, characterized in that it further comprises a determination device (DD) according to claim 9.

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