Response-Time Analysis of Engine Control Applications under Fixed-Priority Scheduling

Engine control systems include computational activities that are triggered at predetermined angular values of the crankshaft, and therefore generate a workload that tends to increase with the engine speed. To cope with overload conditions, a common practice adopted by the automotive industry is to design such angular tasks with a set of modes that switch at given rotation speeds to adapt the computational demand. This paper presents an exact response time analysis for engine control applications consisting of periodic and engine-triggered tasks scheduled by fixed priority. The proposed analysis explicitly takes into account the physical constraints of the considered systems and is based on the derivation of dominant speeds, which are particular engine speeds that are proved to determine the worst-case behavior of engine-triggered tasks from a timing perspective. Experimental results are finally reported to validate the proposed approach and compare it against an existing sufficient test.