WO2007048950A1

WO2007048950A1 - Method and system for controlling the operation of an internal combustion engine with filtering of the engine rotational speed

Info

Publication number: WO2007048950A1
Application number: PCT/FR2006/050986
Authority: WO
Inventors: Pascal Rey; Alexandre Pineau
Original assignee: Renault S.A.S
Priority date: 2005-10-24
Filing date: 2006-10-03
Publication date: 2007-05-03
Also published as: FR2892461A1; FR2892461B1

Abstract

The invention concerns a system for controlling the operation of a motor vehicle internal combustion engine comprising a kinematic chain of torque transmission with a gearbox, including means for measuring (5) the engine instantaneous rational speed and means for filtering (4) oscillations of the measured instantaneous rotational speed. The invention is characterized in that it comprises computing means (1) for computing each time a modelled rotational speed based on the instantaneous transmission ratio of the gearbox and the running speed of the vehicle, the filtering means receiving in input said modelled rotational speed value and the measured value of the engine instantaneous rotational speed.

Description

Method and system for controlling the operation of an internal combustion engine with filtering of the rotational speed of the engine.

The present invention relates to the control of the operation of an internal combustion engine of a motor vehicle.

Such functional checks consist in managing the internal combustion engine by means of various sensors and actuator devices associated with a set of control laws or software strategies, stored in a computer on board the motor vehicle, called the "electronic control unit". (UCE).

The electronic control unit also contains in memory various characterization parameters or calibrations of the combustion engine. The electronic control unit receives information from all sensors whose vehicle is equipped, so as to allow the computer to know in real time the state of the engine. The electronic control unit also receives information regarding the driver's willingness to drive the vehicle. This will result in signals corresponding to actions, for example on the accelerator pedal or the brake pedal of the motor vehicle. From these different physical quantities received by the computer contained in the electronic control unit, it is able to control or regulate all the actuator devices of the engine for optimal operation.

Among the essential information for the control of the operation of an engine, figure in particular information on the instantaneous rotation speed of the engine. Indeed, most of the setpoints required for the control of the operation of an internal combustion engine are mapped according to the engine speed signal. This is particularly the case with the different torque values, the fuel quantity and the advance parameters. injection or ignition, supercharging pressure signals in the case of a supercharged engine, supply pressure signals in a common fuel supply rail, air flow signals, wealth, etc. In addition, the instantaneous rotation speed signal of the motor is often used in calculation algorithms, such as for example the algorithm for calculating the air flow fed into the engine. Finally, the signal of the instantaneous rotation speed of the engine is also used as a measurement value in different control loops, for example in a governor of the engine idling speed.

In summary, there are at least three types of use of information on the instantaneous engine rotation speed for controlling engine operation, namely:

1. in the development of the setpoints necessary for the control of the operation of the engine,

2. in calculation algorithms,

3. in control loops.

The information relating to the instantaneous rotation speed of the engine is generally obtained by a measurement by means of a Hall effect sensor, which makes it possible to measure the time between two teeth of a target fixed on the crankshaft of the combustion engine. The injection computer provides information on the instantaneous rotation speed of the engine which is determined every quarter turn of the engine. This information can be averaged over half a turn.

The instantaneous rotation speed signal of the engine is the image of the acceleration of the engine and the motor vehicle. The engine torque is applied to the road via a clutch or converter when the vehicle is equipped with a automatic transmission, then through a gearbox, a transmission device and the vehicle tires, in contact with the roadway. This set constitutes a kinematic chain which presents inertia, non-linearities due to games, friction, etc. , as well as resonances. As a result, in the case of a torque variation requested from the motor, a response on the instantaneous engine rotation speed signal which is not linear and which reveals a number of oscillations at each change of the speed of the motor. It has already been thought to limit the effect of these oscillations so that they are less felt by the driver and the passengers of the vehicle. For this purpose, driving approval strategies have been used to modulate the engine torque. In the case of a diesel engine, it is thus possible to add a corrective term to the torque demand made by the driver, as a function of the engine speed, the first derivative and the second derivative of the engine speed. The term corrective intervenes on the flow rate of the fuel injected in the case of a diesel engine, and on the ignition advance in the case of a gasoline engine. In both cases, the corrective term is not different from zero unless the entire vehicle driveline is in an oscillatory mode. It can thus be seen that these strategies do not suppress oscillations, but merely limit their effects.

US Patent 4,817,568 discloses a motor that can receive two types of fuel and provides for the control of a fresh air intake control valve, to filter on the measurement of the rotational speed of the engine.

Furthermore, the French patent application FR-A-2 855 219 (RENAULT) describes a method and a system for controlling the operation of an internal combustion engine of a motor vehicle in which the oscillations of the measured value of the instantaneous rotation speed of the engine are filtered. Different types of filtering are described. The object of the present invention is to prevent the propagation of the oscillations of the instantaneous rotation speed signal of the motor so as to eliminate or greatly reduce the oscillations that may result in the development of the setpoint signals necessary for the management of the operation. of the motor. The invention also aims to avoid any disturbance in the calculation algorithms and in the control loops, as well as any deviation on the tracking of the set values.

More specifically, the object of the present invention is to implement a simple and efficient filtering with elimination of the oscillations of the instantaneous rotation speed signal of the motor.

According to one embodiment, the method of controlling the operation of an internal combustion engine is adapted to a motor vehicle comprising a kinematic transmission chain torque with a gearbox. According to the method, information is used on the instantaneous rotation speed of the engine and a filtering of the oscillations of the instantaneous rotation speed signal of the engine is carried out. In addition, a rotational speed model is determined from the instantaneous transmission ratio of the gearbox and the speed of movement of the vehicle, the difference between the instantaneous engine rotation speed and the modeled rotation speed is filtered. and calculating a filtered rotational speed value with practically no oscillations.

Thus, in a particularly simple manner, an effective filtering of the value of the instantaneous rotation speed is obtained. The gearbox being perfectly identified, the modeled rotation speed is very close to the instantaneous rotation speed of the engine as measured. Furthermore, it can be seen that an error in the transmission ratio of the gearbox used for the modeling has only a small impact on the result of the filtering.

Preferably, the filtering indicated above is applied only in the situations where this filtering is necessary, that is to say in particular when oscillations are likely to occur, for example in transient phase of increasing or decreasing torque, or still during passage from a disengaged state to an engaged state or vice versa.

For this purpose, a situation of oscillations of the transmission kinematic chain is preferably detected in order to activate the filtering. It is also preferable to deactivate the filtering when the transmission kinematic chain is in the disengaged state, for which the modeling is not significant.

The filtering can also be deactivated when the difference between the measured instantaneous rotation speed and the modeled rotation speed is greater than a difference threshold, which means that a significant error has been made in the modeling, for example due to bad identification of the gearbox.

Finally, the filtering can be deactivated when the duration of the filtering reaches a threshold of duration. This deactivation can be done gradually.

The filtered rotation regime thus obtained is advantageously used during a time interval, for example 10 ms. Now the measurement of the instantaneous rotation speed is made for example at each top dead center while the measurement of the speed of the vehicle is made. for example every 20 ms. In this case, the filtered rotation regime is preferably resampled every 10 ms using a sliding average over, for example, four points.

The result of the filtering is advantageously subjected to a complementary filtering by means of a low-pass filter of high cut-off frequency with respect to the dynamics of the physical phenomenon which is of the order of 65 Hz, in order to suppress the measurement noise. which are likely to appear on the measured values of the instantaneous rotation speed and the speed of the vehicle. According to one embodiment, a system for controlling the operation of an internal combustion engine of a motor vehicle comprising a kinematic transmission chain of torque with a gearbox, comprises means for measuring the instantaneous rotation speed of the engine and the means for filtering oscillations of the instantaneous rotational speed signal measured. The system further comprises calculating means for calculating at each instant a rotational speed modeled from the instantaneous transmission ratio of the gearbox and the speed of movement of the vehicle, the filtering means receiving as input the value of this rotational speed modeled and the measured value of the instantaneous rotation speed of the engine.

The system may further include means for enabling and disabling the filtering means.

The system may also comprise means for detecting a situation of oscillations of the kinematic transmission chain, capable of acting, as a function of the detection, on the means for activating and deactivating the filtering means.

The system may further comprise means for detecting the disengaged or engaged state of the transmission kinematic chain, capable of acting, depending on the detection, on the means for activating and deactivating the filtering means.

The system may also comprise means for comparing the measured value of the instantaneous rotation speed of the engine with the value of the rotational speed modeled, capable of acting, as a function of the difference between these two values, on the means for activating and disable the filtering means.

The invention will be better understood from the study of the detailed description of an embodiment and implementation illustrated in particular by the appended drawings, in which:

FIG 1 schematically illustrates the main elements of a control system according to the invention;

FIGS. 2a to 2d show various curves illustrating the implementation of a control method according to the invention; and FIG. 3 is a diagram showing the main operations for the implementation of the filtering used in the present invention.

In the method and the system for controlling the operation of an internal combustion engine of a motor vehicle according to the invention, a modeling of the changes in the instantaneous rotation speed of the engine is used. The motor vehicle comprises a transmission transmission kinematic chain equipped with a gearbox. Such a gearbox can be characterized, for each transmission ratio of the gearbox, by a constant value of the vehicle speed divided by the rotational speed of the engine. This constant value is generally called V _mi i and is expressed in km / h by 1000 rpm of the engine. Thus, for example, the so-called "first" transmission ratio can be characterized in a vehicle determined by a value of V _mi i of 7 km / h per 1000 rpm, which means that such a vehicle moving with the gearbox engaged in the first gear ratio moves with a speed of 7 km / h for a rotational speed of the engine of 1000 rpm. In the same way, it is said, for example, that a "second" transmission ratio has a value of V _mi i of 14 km / h per 1000 rpm. The same determination can be made for all transmission ratios of the gearbox. Of course, the values indicated above are different according to the gearboxes. Generally speaking, when the transmission ratio of the gearbox equipping the vehicle and the instantaneous speed of the vehicle are known, it is possible to calculate a rotational speed of the engine modeled and not including not the oscillations of the kinematic chain which are found in the measured value of the instantaneous rotation regime.

In the embodiment illustrated in FIG. 1, the system of the invention comprises calculation means 1 capable of calculating at each instant a modeled rotation speed N _mo d from the instantaneous transmission ratio R of the gearbox. BV referenced 2 and the speed of movement V of the vehicle measured by a sensor 3.

The system also comprises a filtering means 4 which receives as input the value N _mo d of the rotational speed modeled as well as the measured value N of the instantaneous rotation speed of the motor, as determined by a sensor 5. The filtering means 4 then determines, from these two input values, a filtered rotation regime N _f1H which can then be used to control the operation of the internal combustion engine.

Referring to FIG. 2a, it can be seen that the curve shown in dashed lines represents the variations in the instantaneous rotation speed of the motor N as a function of time t. FIG. 2a also shows in solid lines the value of the modeled engine speed N _mo d. As can be noted in FIG. 2c and by way of example, the first transmission ratio (R = I) is switched on. until the time t ₀ . Then, the gearbox is placed in the disengaged position, which is symbolized by the transmission ratio R = O. At time t _1; the second transmission ratio (R = 2) is switched on. Figure 2b shows the vehicle speed V in km / h as a function of time. We see that the speed, substantially constant up to the time t _1; varies thereafter.

The examination of FIG. 2a shows on the dashed curve which represents the variations of the instantaneous engine speed as measured, that the value N undergoes a certain number of oscillations related to the kinematic chain, oscillations which are particularly marked in the vicinity of time ti which corresponds to the transition from the disengaged state to the engaged state in the second gear ratio. On the other hand, the value of the modeled engine speed M _mo d does not include these oscillations, taking into account the way in which the modeling has been made, that is to say starting from the constant value V _mi i taking into account the gradual changes in the speed of the vehicle. It will be noted that the value N _mo d of the modeled rotation regime naturally follows the evolutions of the speed of the vehicle V.

The elaboration of the filtered rotational speed Nf ₁ U by the filtering means 4 of FIG. 1 is carried out for example by means of a low-pass filter with a cut-off frequency which can be between

1 and 3 Hz, insofar as the frequency of the oscillations of the kinematic chain is generally of the order of 3 Hz. This low - pass filter makes it possible to filter the difference ε between the instantaneous rotation regime N and the modeled regime. N _mo d- The difference between the gap ε before filtering and the distance ε after filtering makes it possible to recover only the oscillations of the kinematic chain. Alternatively, the same effect can be obtained by using a high-pass filter to filter the gap ε. The difference between the difference ε before filtering and the difference ε after filtering the instantaneous rotation speed N is then subtracted to obtain the filtered rotational speed Nf ₁ It devoid of oscillations.

FIG. 3 shows, by way of example, an embodiment of such a filtering. The values of the modeled rotation speed N _mo d and the instantaneous rotation speed as measured N are brought to a subtractor 6 which calculates the difference ε = NN _mo d- This gap ε is subjected to a low-pass filter 7 which sends a signal corresponding to the filtered difference or Efi _lt . A calculation element 8 calculates the difference γ = ε-εfi _lt . This difference γ, which corresponds to the oscillation of the measured value of the instantaneous rotation speed N, is subtracted from the value N in the calculation module 9 which transmits the filtered signal Nf ₁ U devoid of oscillations.

It should be noted that the notion of rotational speed modeled does not make sense when the transmission is in the disengaged position. This is the reason why between times to and t _1; no value of the modeled rotation regime is shown in Figure 2a. It is not useful or appropriate to filter when it is not necessary. It is therefore preferable to apply the filtering only when the operation of the motor is such that the measurement of the rotational speed may cause the appearance of oscillations due to the driveline. Such a situation occurs mainly during transient torque phases, increasing or decreasing passage or an end of change of transmission ratio during a transition between a disengaged situation and a geared situation. Moreover, as can be noted on the curve of FIG. 2a, the amplitude of the oscillations declines over time, so that it is not necessary to continue the filtering after a certain time. is readily determined in practice and may be in the range of 1 to 2 seconds.

Figure 2d shows the value of a signal A which is equal to 1 when the filtering is activated and to 0 when it is deactivated. It is observed that the filtering is deactivated in the example illustrated until the time t _1; then activated until the time t ₂ which is a time threshold determined by the experiment, from which the oscillations have practically disappeared.

From the time t ₂ , the activation signal A has progressively passed from the value 1 to the value 0 that it reaches at the time t ₃ which corresponds to the complete deactivation of the filtering system.

Finally, to avoid any risk of difficulty, in case of error for example in the identification of the transmission ratio of the gearbox, it is preferable to provide a deactivation of the filtering system when the difference between the rotation speed measured snapshot and the modeled rotation rate exceeds a certain threshold.

FIG. 4 illustrates the various tests that can thus be performed in an exemplary implementation of the method according to the invention.

In step 10, the existence of a situation of oscillations of the transmission kinematic chain is detected. In the case where this situation is detected, it is found in step 11 the disengaged or engaged state of the gearbox. If the gearbox is not in a disengaged state, it is then checked in step 12 whether the difference ε between the measured rotational speed N and the modeled rotation speed N _mo d does not exceed a threshold of gap S ₁ . If the result of the test is negative, the filter is activated in step 13, which corresponds to sending a corresponding signal to the input 14 of the filtering means 4 visible in FIG. 1. The next step 15 consists in verifying that the duration of the filtering does not exceed a threshold of duration T ₁ . As soon as the duration reaches the threshold T ₁ , the filtering is deactivated during step 16 by sending a signal on the input 14 of the filtering means 4 of FIG.

1.

By modeling the rotational speed of the heat engine, in accordance with the method of the invention and with the filtering carried out, a value of the rotation speed of the engine, suitably filtered and devoid of oscillations, is obtained in a particularly efficient manner. simple and efficient.

Claims

1-A method for controlling the operation of an internal combustion engine of a motor vehicle comprising a kinematic transmission chain of torque with a gearbox, in which information on the instantaneous rotation speed of the engine is used and a procedure is carried out. filtering the oscillations of the instantaneous rotational speed signal of the engine, characterized in that a rotational speed model is determined from the instantaneous transmission ratio of the gearbox and the speed of movement of the vehicle, the filter is filtered The difference between the instantaneous rotation speed of the motor and the modeled rotational speed is deduced by calculating a filtered rotational speed value with practically no oscillations.

2-Method according to the preceding claim, wherein it detects a situation of oscillations of the transmission kinematic chain to activate the filtering.

3-Method according to one of the preceding claims, wherein the filtering is deactivated when the transmission kinematic chain is in the disengaged state. 4-Process according to one of the preceding claims, wherein the filtering is deactivated when the difference between the measured instantaneous rotational speed and the modeled rotational speed is greater than a difference threshold.

5-process according to one of the preceding claims, wherein the filtering is deactivated when the duration of the filtering reaches a threshold of duration.

6-System for controlling the operation of an internal combustion engine of a motor vehicle comprising a kinematic chain for transmitting torque with a gearbox, comprising means (5) for measuring the instantaneous rotation speed of the motor and means for filtering (4) the oscillations of the measured instantaneous rotational speed signal, characterized in that it comprises a calculation means (1) for calculate at each instant a rotational speed modeled from the instantaneous transmission ratio of the gearbox and the speed of movement of the vehicle, the filtering means receiving as input the value of this modeled rotational speed and the measured value of the speed of rotation of the engine. The system of claim 6, further comprising means for enabling and disabling the filtering means.

8-System according to claim 7, further comprising means (10) for detecting a situation of oscillations of the transmission kinematic chain, capable of acting, depending on the detection, on the means for activating and deactivating the means filtering.

9-System according to claim 7, further comprising means (11) for detecting the disengaged or engaged state of the transmission kinematic chain, capable of acting, depending on the detection, on the means for activating and deactivating the filtering means.

10-System according to claim 7, further comprising means (12) for comparing the measured value of the instantaneous rotation speed of the motor with the value of the rotational speed model, able to act, according to the difference between these two values, on the means to activate and deactivate the filtering means.