EP0702139A1 - Method and device for the suppression of longitudinal oscillations of a motorised automotive vehicle - Google Patents

Abstract

The procedure for suppressing longitudinal oscillations of the vehicle involves control of a parameter (P) which regulates the couple provided by the engine. This parameter is calculated in such a way that the engine provides a couple (Ccor) equal to an optimum couple (Copt). The optimum couple corresponds to the request for acceleration (gamma-d) produced by the river, corrected by a correction value (lamda, V). The correction value is proportional to a variable (V) which is calculated from measurements of the instantaneous acceleration (gamma-c) of the body work of the vehicle as a function of time.

Description

The present invention relates to a method and a device for suppressing longitudinal oscillations of a motor vehicle, by controlling at least one parameter for controlling the engine torque, in response to a request for acceleration of the vehicle by the driver. .

These longitudinal oscillations arise in particular during a variation of the acceleration of the vehicle or of the engine torque, of a clutch phase, or even of the passage of an obstacle on a road.

Methods and devices of this type are already known in the state of the art, which make it possible to make corrections and adjustments to the parameters for controlling the operation of an engine, to eliminate oscillations, by monitoring a parameter and by introducing into a control loop of this parameter, a constant, at instants determined as a function of the detection of the oscillations.

However, these methods and these devices have a certain number of drawbacks, in particular as regards the determination of the times of application of the correction, insofar as the latter does not occur permanently.

It is also known from the document FR-A-2 681 908, in the names of the Applicants, a method for correcting the control parameters of an internal combustion engine which consists, from a model estimating the engine torque and d '' a model for each gear ratio estimator, to develop a variable which is a linear combination of the first and second derivatives of the engine speed and represents the oscillations extracted from the engine speed, to apply a variable correction to this variable to determine the variation of the engine torque and from this variation, to determine the correction to be applied to the engine control parameter (s).

However, this method has a certain number of drawbacks, particularly in terms of the complexity of the modeling, the volume of real-time calculations necessary to obtain the correction and the fact that very little action is taken on the start of the oscillation. .

Also known from French patent application No. 93 03 605 filed March 29, 1993, in the names of the applicants, a process for controlling the operation of an internal combustion engine of a motor vehicle, by controlling at least a parameter P1 for controlling the operation of this engine, which consists in developing a filtered engine speed signal NF representative of oscillations of the engine speed N, and in controlling this filtered engine speed signal to 0, to dampen the oscillations of the engine speed , by calculating a correction to be made to the engine torque and determining the corresponding correction CP to be applied to said parameter for controlling the operation of the engine using a digital regulator whose parameters have been previously calculated from a engine torque estimator model into which the parameters for controlling engine operation and a filtered transmission estimator model are introduced For each gearbox ratio.

This method has the disadvantage of only taking into account in the calculation of the correction to be applied to the engine control parameter, the oscillations of the engine speed, and of requiring significant calculation means.

The object of the invention is therefore to propose a solution which is simple to implement in order to solve the problems of longitudinal oscillations mentioned above.

• a) déterminer en fonction du temps des valeurs d'accélération instantanée de la caisse du véhicule,
• b) déterminer une valeur optimum du couple moteur pour l'accélération demandée par le conducteur,
• c) élaborer une variable à partir des valeurs déterminées de l'accélération instantanée de la caisse du véhicule en fonction du temps,
• d) calculer une valeur de correction de couple proportionnelle à cette variable et fonction des caractéristiques intrinsèques du véhicule, à appliquer au couple moteur de valeur optimum,
• e) calculer une valeur de couple corrigée à partir des valeurs de couple optimum et de correction,
• f) calculer un paramètre corrigé de contrôle de couple du moteur correspondant à cette valeur de couple corrigée, et
• g) piloter le moteur en fonction de ce paramètre corrigé avec un retard par rapport à l'instant d'élaboration de la variable inférieur ou égal à un sixième de la période des oscillations longitudinales à supprimer du véhicule.

To this end, the subject of the invention is a method for suppressing the longitudinal oscillations of a motor vehicle, by controlling at least one parameter for controlling the engine torque, in response to a request for acceleration of the vehicle. by the driver, characterized in that it comprises the following stages:

• a) determine, as a function of time, instantaneous acceleration values of the vehicle body,
• b) determine an optimum value of the engine torque for the acceleration requested by the driver,
• c) develop a variable from the determined values of the instantaneous acceleration of the vehicle body as a function of time,
• d) calculate a torque correction value proportional to this variable and a function of the intrinsic characteristics of the vehicle, to be applied to the engine torque of optimum value,
• e) calculating a corrected torque value from the optimum torque and correction values,
• f) calculating a corrected engine torque control parameter corresponding to this corrected torque value, and
• g) control the engine as a function of this corrected parameter with a delay with respect to the instant of development of the variable less than or equal to one sixth of the period of longitudinal oscillations to be removed from the vehicle.

• la variable de l'étape c) est une valeur estimée de la dérivée de l'accélération de la caisse du véhicule par interpolation linéaire de celle-ci à partir des deux dernières valeurs mesurées de l'accélération instantanée de la caisse du véhicule en fonction du temps.
• la variable de l'étape c) est une valeur de la composante ondulatoire de l'accélération instantanée de la caisse du véhicule mesurée à un instant précédent séparé de l'instant d'élaboration de la variable par un quart de la période des oscillations longitudinales à supprimer du véhicule.

This process can possibly have some of the following advantageous characteristics:

• the variable in step c) is an estimated value of the derivative of the acceleration of the vehicle body by linear interpolation thereof from the last two measured values of the instantaneous acceleration of the vehicle body as a function time.
• the variable of step c) is a value of the wave component of the instantaneous acceleration of the vehicle body measured at a previous instant separated from the instant of development of the variable by a quarter of the period of the longitudinal oscillations to remove from the vehicle.

• a) des moyens adaptés pour déterminer en fonction du temps des valeurs d'accélération instantanée de la caisse du véhicule,
• b) des moyens adaptés pour déterminer une valeur optimum du couple moteur pour l'accélération demandée par le conducteur,
• c) des moyens adaptés pour élaborer une variable à partir des valeurs déterminées de l'accélération instantanée de la caisse du véhicule en fonction du temps,
• d) des moyens adaptés pour calculer une valeur de correction de couple proportionnelle à cette variable et fonction des caractéristiques intrinséques du véhicule, à appliquer au couple moteur de valeur optimum,
• e) des moyens adaptés pour calculer une valeur de couple corrigée à partir des valeurs de couple optimum et de correction,
• f) des moyens adaptés pour calculer un paramètre corrigé de contrôle de couple du moteur correspondant à cette valeur de couple corrigée, et
• g) des moyens adaptés pour piloter le moteur en fonction de ce paramètre corrigé avec un retard par rapport à l'instant d'élaboration de la variable inférieur ou égal à un sixième de la période des oscillations longitudinales à supprimer du véhicule.

The subject of the invention is also a device for suppressing longitudinal oscillations of a motor vehicle, by controlling at least one parameter for controlling the torque of the engine in response to a request for acceleration of the vehicle by the driver, characterized in that it comprises:

• a) means adapted to determine, as a function of time, values of instantaneous acceleration of the vehicle body,
• b) means suitable for determining an optimum value of the engine torque for the acceleration requested by the driver,
• c) suitable means for developing a variable from the determined values of the instantaneous acceleration of the vehicle body as a function of time,
• d) means suitable for calculating a torque correction value proportional to this variable and as a function of the intrinsic characteristics of the vehicle, to be applied to the engine torque of optimum value,
• e) means suitable for calculating a corrected torque value from the optimum torque and correction values,
• f) means suitable for calculating a corrected motor torque control parameter corresponding to this corrected torque value, and
• g) means adapted to control the engine as a function of this parameter corrected with a delay with respect to the time of development of the lower variable or equal to one sixth of the period of longitudinal oscillation to be removed from the vehicle.

• la figure 1 représente un organigramme illustrant le fonctionnement du procédé selon l'invention ;
• la figure 2 représente un schéma synoptique illustrant la structure d'un dispositif pour la mise en oeuvre du procédé selon l'invention.

The present invention will be better understood in the light of the description which follows, given solely by way of example and with reference to the appended drawings in which:

• FIG. 1 represents a flowchart illustrating the operation of the method according to the invention;
• FIG. 2 represents a block diagram illustrating the structure of a device for implementing the method according to the invention.

The implementation of the method according to the invention requires the control of the engine torque delivered by the vehicle engine, by command of one or more engine control parameters. Depending on the type of engine used, these control parameters could be, for example, the ignition advance for internal combustion engines, the quantity of fuel admitted for internal combustion engines, or even the intensity or the voltage. power supply for electric motors for so-called electrically propelled vehicles.

In all cases, the control parameter (s) are chosen so that the engine torque is controlled almost instantaneously, that is to say for example at each half-turn of the crankshaft for heat engines.

In addition, in order to control the effects of engine control, the value of the engine torque must be determined periodically during vehicle operation.

This value of the engine torque can be measured or calculated in the case of a heat engine from an engine torque estimator model and from data representative at all times of measurement values of all or part of the following parameters: position of the vehicle acceleration control, engine speed, pressure in the engine intake manifolds, ignition advance, fuel richness, quantity of fuel admitted, temperature of air admitted, etc.

In the case where the engine torque is calculated from, among other things, the engine speed, the latter is determined for example every 10 milliseconds or every half-turn of the crankshaft for thermal engines.

The parameters for controlling the motor torque, the parameters taken into account in determining the motor torque or the measurement frequencies are given here by way of example but in no way limit the scope of the invention.

Similarly, the implementation of the method according to the invention requires knowledge as a function of time of the values of the instantaneous acceleration of the vehicle body.

Thus, measurements of the instantaneous acceleration of the vehicle body must be made periodically during the advancement of the vehicle with a frequency comparable to the frequency used for controlling the engine torque.

In Figure 1, there is shown a flowchart illustrating the operation of the method according to the invention.

Thus, a requested acceleration value γ _d by the driver via the vehicle's acceleration pedal is measured in step 2.

Similarly, a value of the engine speed noted R _m of an engine M is measured in step 4 by means of an appropriate sensor placed on the shaft of the engine M.

From the values γ _d and R _m , the calculation of an optimum torque of the motor denoted C _opt is carried out in step 6 from a conventional mapping process.

At the same time, the instantaneous acceleration values of the body of the vehicle as a function of time using an appropriate sensor attached to the body of the vehicle.

These instantaneous acceleration values of the vehicle body are noted γ _c .

From these values γ _c of the instantaneous acceleration of the vehicle body, measured at a frequency greater than the frequency of the oscillations to be removed from the vehicle, a variable V is developed in step 10.

According to a first embodiment of the method according to the invention, the variable V is an estimated value of the derivative of the instantaneous acceleration of the vehicle body at the time of calculation. This estimate is made by linear interpolation of the derivative from the last two measured values of the instantaneous acceleration of the vehicle body as a function of time.

Conventionally, this variable V is equal to the difference between the last two measured values of the instantaneous acceleration of the vehicle body divided by the time period separating the last two moments of measurement.

According to a second mode of implementation of the method according to the invention, the variable V is a value of the wave component of the instantaneous acceleration of the vehicle body calculated at an instant preceding the instant of development of the variable and separated from it by a quarter of the period of longitudinal oscillation to be removed from the vehicle.

This variable V is equal to the difference between the value of the instantaneous acceleration of the vehicle body measured at an instant preceding the instant of development of the variable and separated from it by a quarter period of the longitudinal oscillations at delete from the vehicle and the instantaneous acceleration value from the vehicle body calculated at the same time as if the engine were rigidly coupled to the vehicle without play and without elasticity.

To avoid the pitfalls of correction divergence and the absence of correction during the first quarter of period caused by this raw variable, part of the engine torque contained in this variable will not be calculated a quarter period before its elaboration but at the time of that -this.

From this variable V, in step 12, using a proportionality coefficient λ as a function of the intrinsic characteristics of the vehicle, a torque correction value λ.V is calculated which is proportional to the variable V.

The proportionality coefficient noted λ is calculated from the intrinsic characteristics of the vehicle considered at the time of calculation.

In particular, the coefficient λ can be determined from the proper pulsation of the oscillations to be removed from the vehicle for each speed ratio, from a damping coefficient due to the tires, from a characteristic coefficient of the transmission stiffness for each ratio of speed, mass of the vehicle body, the moment of inertia of the engine torque, and the rotating elements of the transmission, as well as the ratio between the forward speed of the vehicle and the engine rotation speed .

This last parameter in fact characterizes the gearbox ratio used for vehicles fitted with a gearbox.

The various parameters used for calculating the proportionality coefficient λ are updated periodically and in particular whenever the intrinsic characteristic parameters of the vehicle change or are likely to change, as is the case, for example, after the vehicle has stopped.

We can also determine the coefficient λ experimentally by carrying out a succession of tests, and retaining for λ the value that led to the best result.

In step 14, we calculate from the optimum torque C _opt and the correction value of the torque λ.V a corrected value of the torque denoted C _cor obtained by summing the optimum torque C _opt and the correction value λ.V.

From this corrected torque C _cor , a corrected engine torque control parameter, denoted P, is calculated in step 16 from a conventional model linking the engine torque control parameter and the delivered torque. by this engine in response to the application of this parameter.

Finally, the motor M is piloted in step 18 as a function of the parameter P calculated in the previous step.

In order to make it possible to permanently limit the longitudinal oscillations of the vehicle, the method as described can be implemented cyclically during the entire operating time of the vehicle.

In the case where the vehicle is subjected to a variation in acceleration from an original value to a target value of opposite sign, there is, at a given instant, a total absence of power transmission from the engine to the drive wheels of the vehicle, this period corresponding to the passage time of the clearance of said transmission.

During this period, the instantaneous acceleration of the vehicle body no longer results from the action of the engine. It is almost zero and corresponds only to the action of the braking forces due to the different vehicle components and acceleration due to vehicle weight, which is a function of the gradient of the road.

Under these conditions, in order to be able to implement the method as described previously in the first mode of implementation of the method, which requires knowledge of the derivative of instantaneous acceleration, the passage of the game is detected by detection of a break in the evolution of the acceleration curve of the vehicle, or by any other appropriate means, and the value of the derivative of the instantaneous acceleration of the vehicle body measured immediately is used for the implementation of the method before the start of the period corresponding to the passage of the game and which is made to increase in absolute value along a constant slope during the game. This constant slope will have to pass the derivative of the instantaneous acceleration to a value between one and two times its value in 0.1 seconds.

In Figure 2 is shown schematically a device for implementing the method according to the invention.

This comprises a set of conventional type sensors 20, 22, 24 connected to a computer 30 capable of processing the information received from the sensors according to programs stored in a memory 40 and as a function of characteristic parameters of the vehicle stored in a memory 42 .

The purpose of this computer 30 is to adjust the control parameter (s) P of the motor M and to store certain parameters from the sensors in a temporary memory 44, with a view to their subsequent reuse.

We will prefer to use during the game, a corrected couple C _cor which will be a linear extrapolation as a function of time of the corrected couple C _cor before the game whose coefficient proportionality is between 0 and 0.33 of the derivative of the optimum torque C _opt during the game.

The set of sensors includes at least one instant acceleration sensor 20 linked to the vehicle body, an engine speed sensor 22 and a sensor associated with the vehicle acceleration control 24 for measuring the driver's acceleration request .

As described above, many other measurement values can advantageously be taken into account in the implementation of the method.

In particular, appropriate sensors connected to the computer 30 must be added in the case where the proportionality coefficient λ used for the calculation of the correction to be made to the engine torque depends on vehicle parameters which are liable to change as a function of time and thus allowing their updating in memory 42.

In the program memory 40, there are stored, for use by the computer 30, algorithms for conventional calculation of the optimum torque C _opt as a function of the acceleration demand γ _d of the driver, algorithms for calculating the value of correction of the torque λ.V to be applied to the optimum torque as a function of the instantaneous acceleration γ _c measured from the vehicle body over time, algorithms for calculating the corrected torque C _cor from the optimum torque C _opt and the correction value λ.V, algorithms for calculating the values of the motor control parameter (s) P as a function of the values of the corrected torque C _cor , and algorithms for calculating the value of the instantaneous acceleration of the body of the vehicle as if the engine were rigidly coupled to the vehicle without play and without elasticity.

Characteristic data of the vehicle, whether or not resulting from experimental measurements, and useful to the computer for determining the values of the motor control parameters, are stored in memory 42.

In the case where the intrinsic characteristics of the vehicle stored in the memory 42 can vary over time, the computer 30 modifies in the memory 42 the values of the intrinsic characteristics having been updated using data from appropriate sensors.

The temporary memory 44 is used by the computer 30 to store data received from the sensors which are used at later times during the implementation of the method.

This is particularly the case for the values of the instantaneous acceleration of the vehicle body.

It will then be understood that, as a function of this different information, the computer commands at least one parameter P of control of the engine torque to suppress the longitudinal oscillations of the vehicle, resulting from the driver's acceleration requests, according to the different calculation algorithms described above by implementing the method according to the invention.

Claims (4)

1. Method for eliminating the longitudinal oscillations of a motor vehicle, by controlling at least one parameter for controlling the engine torque in response to a request for acceleration of the vehicle by the driver, characterized in that it involves the following steps: a) determine (in 8) as a function of time the instantaneous acceleration values (γ _c ) of the vehicle body, b) determine (in 6) an optimum value of the engine torque (C _opt ) for the acceleration requested (γ _d ) by the driver, c) develop (at 10) a variable (V) from the determined values of the instantaneous acceleration (γ _c ) of the vehicle body as a function of time, d) calculate (in 12) a torque correction value (λ.V) proportional to this variable (V) and a function of the intrinsic characteristics of the vehicle, to be applied to the engine torque of optimum value (C _opt ), e) calculate (in 14) a corrected torque value (C _cor ) from the optimum torque and correction values, f) calculating (at 16) a corrected parameter (P) of engine torque control corresponding to this corrected torque value (C _cor ), and g) control (at 18) the motor as a function of this corrected parameter (P) with a delay with respect to the instant of development of the variable (V) less than or equal to one sixth of the period of the longitudinal oscillations to be eliminated of the vehicle. 2.- Method according to claim 1, characterized in that the variable (V) of step c) is an estimated value of the derivative of the acceleration of the vehicle body by linear interpolation thereof from the last two measured values of the instantaneous acceleration of the vehicle body as a function of time. 3.- Method according to claim 1, characterized in that the variable V of step c) is a value of the wave component of the instantaneous acceleration of the vehicle body calculated at a previous instant separated from the instant d elaboration of the variable by a quarter of the period of longitudinal oscillations to be removed from the vehicle. 4.- Device for eliminating longitudinal oscillations of a motor vehicle, by controlling at least one parameter for controlling the engine torque in response to a request for acceleration of the vehicle by the driver, characterized in that it comprises : a) means (20) adapted to determine, as a function of time, values of instantaneous acceleration of the vehicle body, b) means (30) adapted to determine an optimum value of the engine torque (C _opt ) for the acceleration requested by the driver, c) means (30) adapted to develop a variable from the determined values of the instantaneous acceleration of the vehicle body as a function of time, d) means (30) adapted to calculate a torque correction value proportional to this variable and as a function of the intrinsic characteristics of the vehicle, to be applied to the engine torque of optimum value, e) means (30) adapted to calculate a corrected torque value from the optimum torque and correction values, f) means (30) adapted to calculate a corrected torque control parameter of the motor corresponding to this corrected torque value, and g) means (30) adapted to control the engine as a function of this parameter corrected with a delay with respect to the instant of development of the variable less than or equal to one sixth of the period of longitudinal oscillations to be removed from the vehicle.

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