EP0652359A1 - Method for controlling the operation of an internal combustion engine and apparatus for the implementation of such a method - Google Patents

Abstract

The present invention relates to a method and to a device for controlling the operation of an internal combustion engine. The device is characterised in that it comprises a multiplexer (4) and at least two maps (2, 3) connected to the inputs of the multiplexer (4) so as to act sequentially depending on the order number of the operating cycle of the motor (M) applied to the multiplexer (4). The invention finds an application in the motor vehicle field. <IMAGE>

Description

The present invention relates to a method of cyclic control of the operation of an internal combustion engine, as well as the device for the implementation of such a method.

Such a method is known, with map servo means stored in memory in a computer and making operating parameters of the engine correspond to control parameters of the latter.

The map that manages the engine's operation is generally determined on the test bench so as to optimize the engine's performance and minimize the emission of polluting gases from it.

We know that the motor slaved in this way is sometimes subject to chaotic behavior which is characterized by pressure instability and motor temperatures and this results in unpleasant vibrations of the motor and the emission of pollutants. This chaotic functioning is very difficult to master by current techniques.

The object of the invention is to avoid as much as possible the above chaotic behavior of an internal combustion engine so that the latter has a stable behavior.

To this end, the invention proposes a method for controlling the operation of an internal combustion engine provided with map servo means, stored in a computer, making the engine operating parameters correspond to control or control parameters. 'entry thereof and which is characterized in that it consists in involving at least two maps sequentially according to the serial number of the engine cycle.

Preferably, the method alternately involves two maps according to the parity of the engine cycle.

Each map defines the fuel injection time and the engine ignition angle as a function of the engine speed and the angle of the engine's intake throttle valve.

The method advantageously consists in defining an optimal mapping corresponding to a couple of input parameters comprising the angle of the throttle valve or a quantity representative of the intake flow and the engine speed, a pair of engine operating parameters comprising the injection time and the ignition angle, this mapping corresponding to the optimal engine performance with minimum emission of pollutants; detect the chaotic engine operating points on the test bench; replace, for each chaotic operating point, the torque operating parameters by a pair of pairs acting alternately, this pair of couples being progressively offset from the pair of optimal initial parameters; retain the pair which gives non-chaotic operation with the desired output; and determine on the test bench the pair of maps giving non-chaotic behavior for all the engine operating points while remaining close to its optimal behavior.

The invention also provides a device for implementing the above method and characterized in that it comprises a multiplexer and at least two maps connected to the inputs of the multiplexer so as to intervene sequentially according to the sequence number of the cycle motor applied to the multiplexer.

Advantageously, the device comprises two maps intervening alternately according to the parity of the motor cycle applied to the multiplexer.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which follows, given with reference to the single figure schematically representing a device for controlling the operation of an engine with internal combustion according to the invention.

The method and the device for controlling the operation of an internal combustion engine M in accordance with the invention will be described in the particular case where there is a single control parameter A which is the angle of the throttle valve d admission of the engine and two input parameters of the cartographic means 1 and which are the angle of the throttle valve and the engine speed. The engine operating parameters are the fuel injection time and the ignition angle of the fuel.

Referring to the figure, the device for controlling the operation of the engine comprises two maps 2, 3 in memory in a computer (not shown) and which are established by defining for each pair of values of the input parameters of the engine, knowing the angle of the throttle valve A and the engine speed R, a pair of pairs of values of the engine operating parameters P (injection time and ignition angle thereof), acting according to the parity Pa of the motor cycle applied to the control input of the multiplexer circuit 4.

To better understand the advantage of producing, by the device according to the invention, a sequence of alternating commands applied to the motor for get out of the chaotic behavior of it, it is necessary to give the theoretical explanations below.

We denote by xn the state of combustion in an engine for the engine cycle n, xn being a vector, the components of which could be the temperature and the pressure of the engine at the instant preceding the explosion phase therein. .

We admit that the mathematical sequence xn is a recurring sequence represented in a simplified way by the formula: $${\text{x}}_{\text{n + 1}}{\text{= λx}}_{\text{not}}{\text{(1- x}}_{\text{not}}\text{).}$$

We know, as explained for example in the review "Pour la science", n ° 170, pages 124 to 127, that such a sequence tends towards a single value for λ less than 3, oscillates between two values for λ between 3 and 3, 5 and becomes chaotic for λ greater than 3.57.

We also know that if we replace λ by a pair of coefficients a, b intervening alternately according to the parity of n, we obtain in a plane of coordinates a, b areas of stable behavior and areas of chaotic behavior. The behavior for a = b = λ is represented by the diagonal of the graph.

By varying λ, we vary xn and we see on the graph that the operation becomes chaotic from a limit value of λ.

To obtain other values of xn, we replace λ by a and b intervening alternately and we can thus find stable behaviors giving for xn values close to the desired values.

• on définit une cartographie optimale faisant correspondre à un couple de paramètres d'entrée constitué par l'angle du papillon des gaz A et le régime moteur R, un couple de paramètres de fonctionnement P constitué par le temps d'injection et l'angle d'allumage, cette cartographie correspondant au rendement optimal du moteur avec émissions minimales de polluants ;
• on détecte au banc d'essai les points de fonctionnement chaotiques du moteur ;
• pour chaque point de fonctionnement chaotique du moteur, on remplace le couple des paramètres de fonctionnement P par une paire de couples intervenant alternativement, cette paire de couple étant progressivement décalée par rapport au couple de paramètre initial et on retient la paire qui donne un fonctionnement non chaotique avec la sortie désirée; et
• on détermine au banc d'essai la paire de cartographies donnant pour tous les points de fonctionnement du moteur un comportement non chaotique de celui-ci tout en restant voisin de son comportement optimal.

The above observations lead to proceed as follows in the context of the process of the invention:

• an optimal mapping is defined which corresponds to a pair of input parameters constituted by the angle of the throttle valve A and the engine speed R, a pair of operating parameters P constituted by the injection time and the angle d 'ignition, this mapping corresponding to optimal engine performance with minimum pollutant emissions;
• chaotic engine operating points are detected on the test bench;
• for each chaotic operating point of the engine, the pair of operating parameters P is replaced by a pair of pairs acting alternately, this pair of pairs being progressively shifted with respect to the initial parameter torque and the pair is retained which gives non-chaotic operation with the desired output; and
• the pair of maps is determined on the test bench giving non-chaotic behavior for all the engine operating points while remaining close to its optimal behavior.

The above alternating control method thus rests on the fact that one can experimentally find a series of repeated commands to the motor in a stationary manner which produce a stable behavior of this motor. This then widens the space for possible motor adjustments and thereby increases the possibility of optimally adjusting the motor.

Claims (6)

Method for controlling the operation of an internal combustion engine provided with map servo means, stored in a computer, making operating parameters of the engine correspond to control or input parameters thereof, characterized in what it consists in sequentially involving at least two maps (2, 3) according to the serial number of the engine operating cycle (M). Method according to claim 1, characterized in that two maps (2, 3) operate alternately according to the parity of the engine cycle. Method according to claim 2, characterized in that each map (2; 3) defines the fuel injection time and the engine ignition angle (M) as a function of the engine speed (R) and the angle (A) of the engine intake throttle valve (M). Method according to claim 3, characterized in that it comprises the following steps: - define an optimal map corresponding to a couple of engine input parameters constituted by the angle (A) of the throttle valve and the engine speed (R), a couple of operating parameters (P) thereof consisting of the injection time and the ignition angle, this mapping corresponding to the optimal performance of the engine with minimum emission of pollutants; - detect the chaotic engine operating points on the test bench; - replace, for each chaotic operating point, the pair of operating parameters (P) with a pair of pairs acting alternately, this pair of pairs being progressively offset from the optimal pair and retain the pair which gives non-chaotic operation of the motor with the desired output; and - determine on the test bench the pair of maps giving non-chaotic behavior for all the engine operating points while remaining close to its optimal behavior. Device for controlling the operation of an internal combustion engine provided with map servo means stored in a computer, matching operating parameters of the engine to control parameters thereof, characterized in that it comprises a multiplexer (4) and at least two maps (2, 3) connected to the inputs of the multiplexer (4) so as to intervene sequentially according to the serial number of the motor cycle applied to the multiplexer (4). Device according to claim 5, characterized in that it comprises two maps (2, 3) acting alternately according to the parity of the motor cycle applied to the multiplexer (4).

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