Spark-ignition engine - Control functions

In this article, we propose a classification of motor control functions by level.

The first level defines the target values to be assumed by the basic variables controlling engine combustion, such as mixture proportioning, quantity of oxidant, combustion efficiency, etc., according to the vehicle's primary objectives, namely :

• compliance with exhaust emission standards;

• compliance with vapour emission standards;

• minimizing consumption ;

• respect for the driver's wishes in terms of vehicle speed profile;

• transmission response compensation ;

• compliance with start-up approval ;

• motor protection against knocking.

The second level consists of implementing the setpoints determined by the first level by controlling the various actuators appropriately.

The third level considers peripheral functionalities whose purpose is to monitor the correct operation of the system, and concerns diagnostics and operating safety.

This example of function classification is for teaching purposes only. In practice, however, functionalities are always organized into hierarchical modules, classified according to a logic specific to the motor control designer. This architecture is essential for a good understanding of the system, and to guarantee its upgradeability.

For "Notations and symbols", please refer to article [BM 2 970].

The complete study of the subject includes the articles :

- BM 2 970 "Spark ignition engine. Components and control strategy" ;

- BM 2 971 "Spark-ignition engine. Control functions" (this article).