FR2918320A1 - Wheel sliding control system for motor vehicle, has regulating units including arbitration module that calculates final control signal of torque of propulsion engine based on calculated intermediate signals - Google Patents

Abstract

The system (10) has acquiring units (12, 14) acquiring rotational speeds (theta-d, theta-g) of wheels of a motor vehicle. Regulating units regulate a propulsion engine that controls sliding of the wheels based on the speed and have a rotational speed set point calculating module (16), and intermediate signal calculation modules (18, 20) that calculate intermediate control signals (u-d, u-g) of engine torque (C-M) when the signals are applied to the engine. An arbitration module (30) calculates a final control signal (u) of the torque based on the calculated intermediate signals.

Description

-1- SYSTEM FOR CONTROLLING TWO WHEELS OF A MOTOR VEHICLE

ACTIONABLE BY ONE ORGAN

  The present invention relates to a control system of the sliding of two wheels of a motor vehicle, the two wheels being operable with a single member.

  A slip of a wheel of the vehicle may appear during any phase of driving a vehicle, and in particular when the wheel torque is controlled by a torque delivered by a propulsion motor, as is the case for example a request for acceleration of the vehicle from the driver who presses an accelerator pedal. In such situations, it is important for the safety of the vehicle that the wheel slip is controlled, and this using the only active wheel actuator at this time, namely the propulsion engine.

  Two-wheel slip control systems of a vehicle mounted on the same axle thereof, using the torque delivered by the engine, are known. In this type of system, these wheel slips are estimated as a function of measured rotation speeds thereof, a motor torque setpoint calculated according to the estimated slippage and a single control of the engine torque, for example of the proportional integral type, is implemented according to the calculated setpoint, in order to reduce the largest estimated slip. However, it is observed that a single global control law does not ensure identical performance for a low and a strong slip undergone by the wheels. In addition, the largest slip is controlled, regardless of other slips. Moreover, the architecture of these systems is fixed and therefore does not allow to take into account different phases of life of the wheels, such as anti-slip, anti-packaging, or different specifications concerning the driving pleasure. The object of the present invention is to solve the aforementioned problems by proposing a two-wheel slip control system which makes it possible to differentiate the two wheels when ordering.

  For this purpose, the subject of the invention is a system for controlling the sliding of two wheels of a motor vehicle, the two wheels being actuable by means of a single member, said system comprising means for acquisition of a rotational speed of each of the two wheels and means for controlling said member as a function of the speeds acquired. According to the invention, the control means comprise: for each of the wheels, means for calculating an intermediate control signal of said member adapted to control the sliding of the wheel when it is applied to said member; and means for calculating a final control signal of said member as a function of the calculated intermediate signals. Thus, a calculation of an optimum control signal of the sliding of each of the wheels is implemented at any time. It then becomes possible to implement, at any time, type of slip or phase of life of wheels, an arbitration between these two control signals that are constantly present. For example, it may be chosen to control the wheel that slides the most for security reasons. It is also possible to choose to control the wheel that slides the least for reasons of driving pleasure to promote acceleration of the vehicle. It is also possible to choose a compromise between these two situations according to a predetermined driving / safety approval specification. According to particular embodiments of the invention, the system comprises one or more of the following characteristics: the means for calculating the intermediate signal comprise a regulator of the speed of rotation of the wheel on a predetermined speed of rotation command; the means for calculating the final signal are able to calculate the latter as a function of a type of wheel slip diagnosed; the means for calculating the final signal are able to calculate it according to predetermined approval and driving safety criteria; the means for calculating the final signal are able to calculate the latter according to the equation: u = Kxmax (ud, ug) + (1-K) xmin (ud, ug) where u is the final control signal, ud and uQ are the intermediate driving signals, and K is a predetermined setting parameter between 0 and 1; means for diagnosing a rolling state of each of the two wheels, and in that the parameter K equal to 1 when one of the two wheels is in a blocking state produced by a loss of adhesion subsequent to a braking engine; Means for diagnosing a rolling state of each of the two wheels, and in that the parameter K is less than 0.5 when at least one of the two wheels is diagnosed as having a runaway; the parameter K is equal to 0; - The diagnostic means are able to compare control errors concerning the rotational speeds of the two wheels, and in that a significant runaway of one of the two wheels is diagnosed when the corresponding control error is positive; means for diagnosing a rolling state of each of the two wheels, and in that the parameter K is greater than 0.5 when the large runaway is diagnosed as being controlled; the parameter K is equal to 1; - the runaway is diagnosed as controlled when the regulation errors associated with the two wheels are negative; and 15 - said member is a propulsion engine of the vehicle.

  The present invention will be better understood on reading the description which follows, given solely by way of example, and made in relation to the single appended figure which is a schematic view of a system according to the invention. In the figure, there is shown a system 10 for controlling the sliding of two wheels of a motor vehicle mounted on the same axle thereof, by means of a motor torque CM delivered by a propulsion engine of the vehicle. The system 10 comprises means 12, 14 for acquiring a rotation speed 9d, 9g of each of the wheels and a first module 16, connected to the acquisition means 12, 14. The module 16 calculates a setpoint 9c of speed of rotation as a function of the measured speeds and of data coming from other organs of the vehicle. More particularly, the module 16 determines the occurrence and the degree of slip undergone by the wheels and calculates the setpoint 9c to reduce or cancel the sliding thereof. This module 16 is conventional and will not be explained in more detail later. In the context of the invention, any type of setpoint calculation is suitable. According to the invention, the system 10 also comprises, for each of the wheels, a second module 18, 20 for calculation, connected to the means 12, 14 for acquiring the speed of rotation thereof and to the first module 16 for calculating the rotation speed reference 9,. The second module 18, 20 calculates as a function of the reference 9ca and the measurement 9d, 9g of the rotational speed, an intermediate control signal ud, ug of the engine torque G. More particularly, the second module 18, 20 calculation comprises a regulator consisting of a subtractor 22, 24 forming a regulation error d, cg, equal to the difference of the speed reference 9c and the measured speed 9d, 9g received at the input, and a block 26, 28 implementing a law regulating the speed measured on the set speed, for example of integral proportional type. The control signal ud, ug thus calculated has the effect, if it is actually applied to the motor, to cancel the control error d, cg, and thus to control the sliding of the wheel. A second module 18, 20 calculating therefore provides a control signal the wheel associated therewith and that decoupled vis-à-vis the other wheel. At each instant, the system 10 thus determines a signal which, if it is applied to the motor, optimally controls the sliding of the wheel, that is to say uses the motor torque CM only for the benefit of the control of the motor. sliding of this wheel. The system 10 finally comprises an arbitration module 30 connected to the second calculation modules 18, 20 and determining, as a function of the intermediate control signals ud, ug a final control signal u of the engine torque G.

  This arbitration module also receives, as input, diagnostic data from other wheel slip control systems, such as, for example, an anti-skid system, which diagnoses a runaway of a wheel consecutively loss of adhesion during an acceleration phase or a blockage of a wheel following a loss of adhesion during a braking phase by the engine, and an anti-lock wheel system, which diagnostics a blockage of a wheel following a loss of grip during a braking phase by brakes equipping the wheels, as is known per se. Preferably, the arbitration module 30 calculates the final control signal according to the equation: u = Kxmax (ud, ug) + (1-K) xmin (ud, ug) where K is a predetermined setting parameter between 0 and 1. Thus, the existence of the intermediate control signals ud, ug allows any type of arbitration between the wheel that slides the least and the wheel that slides the most by an appropriate choice of the parameter K. This choice K is carried out according to criteria of safety and driving pleasure as well as the life phase of the vehicle, namely the wheel diagnosis performed by anti-skid and anti-lock wheel systems. Thus, in the case where a racing wheel is diagnosed following a loss of grip during acceleration (we speak ASR mode), the choice of K = 0 has the effect of regulating the speed of the wheel that slides the most, that is to say the wheel having the lowest grip on a road on which rolls the vehicle. Thus, the choice of K = 0 results in a significant and rapid reduction of the motor torque CM and therefore increased safety. In the ASR mode, the choice of K = 1 has the effect of regulating the wheel that slides the least, that is to say the wheel has the strongest grip on the road, and therefore causes a moderate and slow reduction of motor torque CM and therefore increased motor skills.

  Preferably, the arbitration module 30 also receives as input the control errors d, cg, and carries out as a function thereof an additional diagnosis of the rolling condition of the wheels. The arbitration module thus implements, when the ASR mode is diagnosed, the following selection law for the parameter K: K 0.5, and preferably K = 0, if cg <0 or d <0. This choice favors safety in search of motor skills. Indeed, if the measured rotation speed 9d, 9g of at least one of the wheels is greater than the speed reference 9c, this means that the sliding of this at least one wheel is important, that is to say requires to be reduced; and ^ K> 0.5, and preferably K = 1, if cg 0 and d 0. This choice favors a resumption of motor skills, and more particularly, when K = 1, the rapid establishment of a slip level that maximizes motor skills. The fact that the two regulation errors are positive means that the significant slip diagnosed in ASR mode is now sufficiently attenuated to allow a better driving pleasure, namely a higher traction. In the case where a locking of a wheel is diagnosed following a loss of adhesion during a braking phase with the engine (we will speak of MSR mode), the choice of K = 0 has the effect of regulate the speed of the wheel that slips the least, resulting in a moderate and slow increase in the engine torque CM, and the choice of K = 1 has the effect of regulating the speed of the wheel that slides the most, resulting in a large and rapid increase in engine torque G.

  Preferably, when the MSR mode is diagnosed, the arbitration module selects K = 1 to ensure the stability of the vehicle. Indeed, in the MSR mode, the priority is to limit as effectively as possible a slip rather than regulate it precisely around a predetermined setpoint value. In addition, when the MSR mode is diagnosed and in addition the anti-skid system is activated, the arbitration module selects K = 0 to regulate the slip observed to a level sufficient to optimize the braking component. engine. This has the effect of reducing the action of the sliding control in MSR mode so that this command does not interfere with the anti-lock wheels. Indeed interference of these two types of control can be dangerous in certain situations.

  Of course, other embodiments are possible.

Claims (13)

  1. A system for controlling the sliding of two wheels of a motor vehicle, the two wheels being actuable by means of a single member, said system comprising means (12, 14) for acquiring a speed of rotation. each of the two wheels and means (12, 14, 16, 30) for controlling said member as a function of the speeds acquired, characterized in that the control means (12, 14, 16, 30) comprise: wheels, means (18, 20) for calculating an intermediate control signal of said member adapted to control the sliding of the wheel when it is applied to said member; and means (30) for calculating a final driving signal of said member as a function of the calculated intermediate signals.   2. System according to claim 1, characterized in that the means (18, 20) for calculating the intermediate signal comprise a regulator of the speed of rotation of the wheel at a predetermined speed of rotation.   3. System according to claim 1 or 2, characterized in that the means (30) for calculating the final signal are able to calculate it according to a type of wheel slip diagnosed.   4. System according to claim 1, 2 or 3, characterized in that the means (30) for calculating the final signal are able to calculate it according to predetermined approval criteria and driving safety.   5. System according to any one of the preceding claims, characterized in that the means (30) for calculating the final signal are able to calculate it according to the relationship: u = Kxmax (ud, ug) + (1-K ) xmin (ud, ug) where u is the final driving signal, ud and ug are the intermediate driving signals, and K is a predetermined setting parameter between 0 and 1. -8-   6. System according to claim 5, characterized it comprises means (30) for diagnosing a rolling state of each of the two wheels, and in that the parameter K equal to 1 when one of the two wheels is in a blocking state produced by a loss of adhesion following engine braking.   7. System according to claim 5 or 6, characterized in that it comprises means (30) for diagnosing a rolling state of each of the two wheels, and in that the parameter K is less than 0.5 when at least one of the two wheels is diagnosed as having runaway.   8. System according to claim 7, characterized in that the parameter K is equal to 0.   9. System according to claim 7 or 8 and claim 2 taken together, characterized in that the means (30) for diagnosis are able to compare control errors concerning the rotational speeds of the two wheels, and in that a significant runaway of one of the two wheels is diagnosed when the corresponding regulation error is positive. 20   10. System according to claim 7, 8 or 9, characterized in that it comprises means (30) for diagnosing a rolling state of each of the two wheels, and in that the parameter K is greater than 0, 5 when the large runaway is diagnosed as under control. 25   11. System according to claim 10, characterized in that the parameter K is equal to 1.   12. System according to claim 10 or 11 and claim 9 taken together, characterized in that the runaway is diagnosed as mastered when the control errors associated with the two wheels are negative.   13. System according to any one of the preceding claims, characterized in that said member is a propulsion engine of the vehicle. 10