Selecting the Transition Speeds of Engine Control Tasks to Optimize the Performance

Engine control applications include functions that need to be executed at specific rotation angles of the crankshaft. The tasks performing these functions are activated at variable rates and are programmed to be adaptive with respect to the rotation speed of the engine to avoid overloading the CPU. Simplified control implementations are used at high speeds; for example, reducing the number of fuel injections or the complexity of the computations. Such different control implementations define execution modes with different execution times for different ranges of the rotation speed. The selection of the switching speeds for the operating modes of such tasks is an optimization problem, consisting in determining the optimal transition speeds that maximize the engine performance while guaranteeing schedulability. This article presents three methods for tackling such an optimization problem under a set of assumptions about the performance metrics: two heuristics and a branch and bound method that guarantees finding the optimal solution within a given speed granularity. In addition, a simple method to compute a performance upper bound is presented. The approach and the hypothesis are validated using a Simulink model of the engine and the computational tasks, considering the engine efficiency and the production of pollutants (NO 2 ) as metrics of interest. Simulation experiments show that the performance of proposed heuristics is quite close to that of the upper bound and the optimum within a finite granularity. </jats:p