FR2718191A1 - Suppression oscillation along automobile longitudinal axis - Google Patents

Abstract

Characteristic oscillation periods and overall drive take-up times, experimentally determined, are entered in control unit memory. The unit receives operational input every e.g. 10ms covering e.g. instantaneous acceleration, accelerator pedal position, and prime mover variables, and controls engine or electric motor torque. If, e.g., decelerating (al) the driver calls for an acceleration (a2), the control unit initially raises the torque till it becomes slightly positive (CaO, ta1), maintaining this level by closed loop control for a period (Pal) corresponding to the drive take-up time under the conditions then obtaining. This period is previously determined experimentally; opt., its termination (ta2) is recognised from changed operational parameters. The torque is then (ta2) raised till the required acceleration (a2) is achieved(ta3).

Description

The present invention relates to a method and a device for deleting

  longitudinal oscillations of a motor vehicle, by controlling at least one torque control parameter delivered by this engine, as a function of the acceleration of the vehicle.

  These longitudinal oscillations are born

  particularly when the acceleration of the vehicle varies from an original value to a target value of opposite sign. 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 times determined according to the

oscillation detection.

  However, these methods and these devices have a certain number of drawbacks, in particular with regard to the determination of the times of application of the correction, insofar as the latter does not intervene.

permanently.

  It is also known from document FR-A-2

  681 908, in the names of the Claimants, a method of correcting

  tion of the control parameters of an internal combustion engine which consists, from an estimating model of the engine torque and a model for each estimating speed ratio of the transmission, to develop a variable which is a linear combination of 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 one or more

engine control parameters.

  However, this method has a certain number of drawbacks, particularly in terms of the complexity of the

  modeling, of the volume of real-time calculations required

  to obtain the correction and the fact that there is very little effect 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 plaintiffs, a process for checking the functioning

  ment of an internal combustion engine of a motor vehicle, by controlling at least one parameter Pl for controlling the operation of this engine, which consists of

  develop a NF filtered engine speed signal representing

  tif of engine speed oscillations N, and to control this engine speed signal filtered to 0, to dampen the engine speed oscillations, by calculating a correction

  to bring to the engine torque and determination of the correctness

  corresponding CP to apply to this parameter of

  check engine operation using a regulator

  digital tester whose parameters have been previously calculated from an engine torque estimator model into which the engine operation control parameters are introduced and a filtered transmission estimator model, 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 resolve the

  longitudinal oscillation problems mentioned above

  demment. To this end, the subject of the invention is a method of the aforementioned type characterized in that, in response to a request for variation of the acceleration of the vehicle from an original value to a target value of opposite sign: a) we adjust the control parameter to obtain the optimum engine torque as a function of the request for variation of the acceleration until the engine torque reaches a value close to zero and the sign of the target acceleration, b) the parameter is adjusted control to maintain the engine torque at an approximately equal value

  at said value close to zero and the sign of the acceleration

  target ration for an initial period of time

  completed according to the conditions of use of the vehicle and the intrinsic characteristics of it, and c) the control parameter is adjusted to make

  vary the engine torque and allow the vehicle to reach

  dre its target acceleration value after a second predetermined period of time depending on the conditions

  of vehicle use and intrinsic characteristics

secs of it.

  This process may possibly present some-

  nes of the following advantageous characteristics: - the first period of time corresponds to the passage time of the clearance of the vehicle transmission elements during a change in sign of the acceleration of the vehicle; the passage time of the game is determined

  experimentally for the different conditions of use

  vehicle station; - the clearance time of the clearance is calculated for each condition of use of the vehicle from a clearance value measured experimentally;

  - the end of the first corresponding time period-

  lays at the instant of passage through an extremum of the instantaneous engine speed of the vehicle engine when maintaining the engine torque of the vehicle at a value close to zero and of the sign of the target acceleration;

  - the end of the first corresponding time period-

  lays at the instant when the instantaneous acceleration of the vehicle bends significantly; - the second period of time has a duration

  roughly between half and eighty-five

  mes of a period of longitudinal oscillations & remove from the vehicle; - the second period of time is determined experimentally. According to another aspect, the invention also relates to a device for implementing this method. This device for eliminating longitudinal oscillations of a motor vehicle, by controlling at least one torque control parameter delivered by this engine, as a function of the acceleration of the vehicle, is characterized in that it comprises means adapted for, in response to a request for variation of the acceleration of the vehicle from an original value to a target value of opposite sign: a) adjusting the control parameter to obtain the optimum engine torque as a function of the request for variation of the acceleration, and detect the achievement by the engine torque of a value close to zero and of the sign of the target acceleration,

  b) adjust the control parameter for main-

  set the engine torque to a value approximately equal to said value close to zero and to the sign of the target acceleration for a first period of time determined as a function of the conditions of use of the vehicle and of the intrinsic characteristics of the latter, and c) adjust the control parameter to make

  vary the engine torque and allow the vehicle to reach

  dre its target acceleration value after a second predetermined period of time depending on the conditions

  of vehicle use and intrinsic characteristics

secs of it.

  The present invention will be better understood on

  light of the description which follows, given only

  by way of example and with reference to the appended drawings in which:

  - Figure 1 shows the evolution of access

  leration and engine torque of a vehicle depending on the

  time during a vehicle acceleration phase, illus-

  trant the implementation of the method according to the invention;

  - Figure 2 shows the evolution of access

  leration and engine torque of the vehicle depending on the

  time during a vehicle deceleration phase, illus-

  trant the implementation of the method according to the invention; - Figure 3 shows a block diagram illustrating the structure of a device for setting

  work of 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 for internal combustion engines, or even the intensity or the voltage.

  for the electric motors of motorisa-

  tion of 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

  say for example every turn of the crankshaft to

heat engines.

  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 thermal engine from a model estimating the engine torque and data representative at each instant of values of

  measurement of all or part of the following parameters: posi-

  tion of the vehicle acceleration control, engine speed, pressure in the engine intake manifolds, ignition advance, fuel richness, quantity of

  fuel admitted, air temperature 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 all

  the crankshaft U-turns for internal combustion 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 as

  example but in no way limit the scope of the information

vention.

  In FIG. 1, a variation of the acceleration of the vehicle requested by the driver in solid line and the variations of the engine torque obtained by applying the method according to time have been represented as a function of time

  the invention, in dotted lines, during an acquisition phase

  vehicle speeding up, the vehicle accelerating

  negative acceleration.

  The driver of the vehicle wishing to increase the speed of his vehicle, accelerates, for example by pressing the accelerator pedal if it is a private vehicle in order to define an increase in acceleration of an original value Yal . negative to a

target value Ya2 positive.

  In the example shown in FIG. 1, this request for modification of the acceleration, represented in solid line, from the value y., To the value Ya2 is carried out linearly as a function of the time between the instants tao and taf . After this instant ta, the driver maintains

acceleration to its value y2.-

  In response to such a request from the driver of the vehicle, the method according to the invention consists in controlling the engine torque of the vehicle engine until the acceleration reaches its value y, 2, according to the

  three operating phases described below.

  From the instant tao corresponding to the start of the request for variation of acceleration by the driver until an instant taj corresponding to the instant when the engine torque reaches a value Co ,, close to zero but positive, the sign of l Y.2 target acceleration is positive, the engine torque is controlled to correspond at all times to an optimum engine torque to obtain the acceleration requested by the driver of the vehicle. The optimum engine torque at each instant may be calculated by a conventional method of optimizing the acceleration of a vehicle, used for example in electronic accelerators, or even be determined empirically, the variation of the engine torque between t ,

  and ta1 not being critical for the implementation of the pro-

  yielded, it being understood that the engine torque must reach

  a CAD value close to zero and positive.

  In Figure 1, there is shown in dot lines

  tilled between taO and ta1 a linear increase in torque

  engine up to its C8o value. It goes without saying that an increase

  Nonlinear tion can also be considered.

  During a first period of time P81 extends

  from time ta1 to time t82, the value of the engine torque is maintained approximately at its value Co ,, close to

  zero but of positive sign thanks to a classic control

  motor torque by commanding a parameter at

  less of the motor by a closed loop system.

  In fact, the length of the first period of

  time is determined according to the conditions of use

  tion of the vehicle and its intrinsic characteristics. According to a first mode of implementation of the method according to the invention, this first period of time P.1 corresponds to the time of passage of the clearance of the transmission elements of the vehicle during a change of sign of

the acceleration of it.

  The passage time of the game can for example be determined experimentally for the different conditions of use of the vehicle. In fact, this clearance time of the clearance is a function of various characteristic parameters of the vehicle and in particular of the value of the clearance, of the transmission ratio, of the inertia

  engine and engine torque requested by the accelerator.

  For vehicles with a gearbox-

  its, whether manual or automatic, the passage time of the game must be determined for the different conditions of use of the vehicle for each report

of speeds.

  Indeed, a change in gearbox ratio modifies the vehicle's transmission chain and causes a change in an intrinsic characteristic of the vehicle, requiring a new determination of the

play time.

  According to a variant, a single measurement

  mental changeover time of the game is performed for each gear ratio in a particular condition of use of the vehicle, the times of

  passage of the game under different conditions of use

  the vehicle being calculated for each gear ratio from a mathematical estimator model and from

this experimental measurement.

  According to a second embodiment of the method according to the invention, the instant t, 2 corresponds to the instant of passage through a maximum of the engine speed

vehicle engine snapshot.

  According to a third embodiment, the instant t.2 corresponds to the instant where the instantaneous acceleration of the vehicle increases rapidly so

significant.

  In these latter two modes of implementation, it is necessary to provide means for measuring or calculating the instantaneous engine speed respectively and

  instant acceleration of the vehicle.

  These means being conventional we will not describe them

not in detail.

  In the case where time t, 2 cannot be

  determined by the criterion described in one of the two

  niers previous implementation modes, the instant t2 must be considered as reached after a predetermined period of time, in order to continue the implementation

of the process.

  From instant ta2 to instant t, 3, the couple

  motor is increased by adjusting the control parameter

  the of its operation so that the acceleration of the vehicle reaches the target value y, 2 defined by the driver in a second period of time P, 2 extending

from ta2 to ta3-

  This second period of time P, 2 is determined

  born according to the conditions of use of the vehicle

  and intrinsic characteristics of it.

  This second period of time is between half and four-fifths of a period of the longitudinal oscillations to be removed from the vehicle, and

  for example equal to three-quarters of it.

  The period of longitudinal oscillations to be removed from the vehicle is determined experimentally by subjecting the vehicle to the same type of acceleration

  without applying the process according to the invention.

  Knowing the value of the second period of time in the conditions of use of the vehicle and in

  according to its intrinsic characteristics, in particular

  link the speed ratio used, the engine torque is increased for example linearly with respect to time, as shown in dotted lines in FIG. 1, to allow the acceleration of the vehicle

  reach its target value Y 2 at time t, 3.

  It is of course possible to optimize the variation of the engine torque during this second period of time by using a conventional method of optimization of the engine torque. In FIG. 2, the evolution as a function of time of different parameters has been represented in a

  vehicle deceleration phase.

  A solid line shows a request for variation of vehicle acceleration with an original value

  Ydl positive to a target value Yd2 negative.

  This request therefore corresponds in this case to a deceleration. In dotted lines is represented the evolution

  of the engine torque of the vehicle as controlled by applica-

  tion of the process according to the invention.

  The implementation of the method is similar to the case of an acceleration phase described with regard to the

figure 1.

  In particular, as in the case of an acceleration

  ration, deceleration is divided into three phases

  successive engine torque checks.

  From instant tdo to instant tdl, corresponding to the instant when the engine torque reaches a close value Cdo

  from zero but negative, the target acceleration being negative

  ve, the engine torque is controlled to give acceleration

  vehicle ration, at all times, an optimized value

  from that requested by the driver.

  As in the previously mentioned case of an acceleration, there is shown in FIG. 2, a linear variation as a function of time from the engine torque to its

Cdo- value

  From instant tdl to instant td2, a first period of time Pd1 elapses during which the engine torque is maintained at a value roughly equal to the value Cdo.

  As in the case of an acceleration, the first

  1st period of time Pdl is determined according to

  vehicle operating conditions and characteristics

that are intrinsic to it.

  This first period of time Pdl corresponds for example to the time of passage of the clearance of the vehicle transmission elements, during a change of sign of

  the acceleration of it. It is determined experimentally.

or results from a calculation.

  According to other modes of implementation, the ins-

  as long as td2 corresponding to the end of this first period of time Pdl, can be determined by the detection of a minimum of the instantaneous engine speed or of a rapid and significant reduction in the instantaneous acceleration of the vehicle.

  In the case where the instant td2 cannot be determined

  undermined by validation of one of the preceding criteria, before the end of a predetermined period of time, the instant td2 is

  considered to have been reached at the end of this predefined period

  finished. A second period of time Pd2z extending between the times td2 and td3 corresponds to a reduction in the engine torque so that the vehicle reaches its value

target Yd2-

  This second period of time Pd2 is determined as a function of the conditions of use of the vehicle and of the intrinsic characteristics of the latter and, for example, has a duration equal to three-quarters of a period

  longitudinal oscillations of the vehicle to be suppressed.

  In the case of an internal combustion engine fitted with an injection device, this period of time Pd2 can be reduced to a duration equal to a quarter of the period of

  longitudinal oscillations to be suppressed by cutting the

  jection at time td3 thus defined.

  In Figure 3 is shown diagrammatically

  matic a device for implementing the

method according to the invention.

  This includes a set of sensors 10, 12, 14 connected to a computer 20 capable of processing the information received from the sensors according to programs stored in a memory 30 and according to parameters

  characteristics of the vehicle stored in a memory 32.

  The purpose of this computer 20 is to adjust the motor control parameter (s) P and to store certain parameters from the sensors in a temporary memory 34, with a view to later re-use of

these.

  The set of sensors includes at least one acceleration sensor 10 linked to the structure of the vehicle, an engine torque sensor 12, a speed sensor

  motor 13 and a sensor associated with the acceleration control

  tion 14 of the vehicle to measure variations in acceleration

  ration requested by the driver.

  As described above, many other measurement values can advantageously be taken into account.

  account in the implementation of the process.

  In particular, the engine torque may result from a direct measurement or from a calculation made from

other parameters measured.

  In the program memory 30 are stored, for use by the computer, the algorithms for determining the different time periods defined in the method and algorithms for calculating the values of the engine control parameters as a function

  data received by the computer.

  Characteristic data of the vehicle,

  whether or not experimental measurements, and useful for cal-

  culater for determining parameter values

  motor control, are stored in memory 32.

  Temporary memory 34 is used by the

  computer 20 for storing data reviewed by the cap-

  ters that are used at times after the

  during the implementation of the process.

  We can then see that, as a function of these differences

  information, the computer controls at least one parameter P of engine torque control to suppress the longitudinal oscillations of the vehicle, resulting from requests for variations in acceleration thereof, according to the different operating phases described above.

Claims (10)

  1.- Method for eliminating the longitudinal oscillations of a motor vehicle, by controlling at least one parameter (P) for controlling the torque delivered by this engine, as a function of the acceleration of the vehicle, characterized in that that, in response to a request to vary the acceleration of the vehicle from an original value (y.,; Ydl) to a target value (Y.2; Yd2) of opposite sign: a) the parameter (P ) control to obtain the optimum engine torque as a function of the request for variation of the acceleration until the engine torque reaches a value (cao; Cdo) close to zero and the sign of the target acceleration, b) the control parameter (P) is adjusted to maintain the engine torque at a value approximately equal to said value (Co; Cdo) close to zero and to the sign of the target acceleration during a first period (P.,;   Pdl) of time determined according to the conditions of use   reading of the vehicle and its intrinsic characteristics, and c) the control parameter (P) is adjusted to vary the engine torque and allow the vehicle to reach its target acceleration value (Y.2; Yd2) at   after a second period (Pa2; Pd2) of predetermined time   born according to the conditions of use of the vehicle   and intrinsic characteristics of it.   2. A method of eliminating the longitudinal oscillations of a motor vehicle according to claim 1, characterized in that the first period (Pal; Pd1) of time corresponds to the passage time of the clearance of the vehicle transmission elements during d 'a   change in sign of vehicle acceleration.   3.- A method of eliminating longitudinal oscillations of a motor vehicle according to claim 2, characterized in that the clearance time of the game is determined experimentally for   different conditions of use of the vehicle.   4. A method of eliminating longitudinal oscillations of a motor vehicle according to claim 2, characterized in that the time of   passage of the game is calculated for each use condition   sation of the vehicle from a play value measured experimentally. 5.- A method of eliminating longitudinal oscillations of a motor vehicle according to claim 1 or 2, characterized in that the end of the first period (Pal; Pal) of time corresponds to the instant of passage through an extremum the instantaneous engine speed of the vehicle engine when the vehicle engine torque is kept close to zero and of the target acceleration sign.   6.- Method for eliminating the longitudinal oscillations of a motor vehicle according to claim 1 or 2, characterized in that the end of the first period of time corresponds to the instant o the instantaneous acceleration of the vehicle bends of significantly.   7.- Method of suppressing long oscillations   of a following motor vehicle   any one of the preceding claims, character-   laughed in that the second period (P.2; Pd2) of time has   between half and eighty-five   mes from a period of longitudinal oscillations to remove from the vehicle.   8. A method of eliminating longitudinal oscillations of a motor vehicle according to claim 7, characterized in that the second   time period (P.2; Pd2) is roughly equal to the three-   quarters of the period of the oscillations.   9.- Method of suppressing long oscillations   gitudinal of a motor vehicle according to claim 7 or 8, characterized in that the second   period (P, 2; Pd2) of time is determined experimentally-   is lying. 10.- Device for suppressing longitudinal oscillations of a motor vehicle (M), by controlling at least one parameter (P) for controlling the   torque delivered by this engine, depending on the acceleration   tion of the vehicle, characterized in that it comprises   means (20) adapted for, in response to a demand for   riation of the vehicle acceleration from an original value (Ya .; Ydl) to a target value (Y.2; Yd2) of opposite sign: a) adjust the control parameter (P) to obtain the optimum engine torque in as a function of the acceleration variation request, and detect the achievement by the engine torque of a value (Co; Cdo) close to zero and of the sign of the target acceleration, b) adjust the parameter (P) of control to maintain the engine torque at a value approximately equal to said value (Co; Cdo) close to zero and to the sign of the target acceleration during a first period (Pl;   Pdl) of time determined according to the conditions of use   readout of the vehicle and its intrinsic characteristics, and c) adjust the control parameter (P) to vary the engine torque and allow the vehicle to reach its target acceleration value (Y2; Yd2) at   after a second period (Pa2; Pd2) of predetermined time   born according to the conditions of use of the vehicle   and intrinsic characteristics of it.