Response-time analysis for real-time tasks in engine control applications

Abstract

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. For this reason, these tasks are referred to as adaptive variable-rate (AVR). This paper presents an exact response time analysis for engine control applications consisting of periodic and AVR tasks scheduled by fixed priority. The proposed analysis is first presented for task sets with a single AVR task, and then extended to consider multiple AVR tasks related to a common rotation source. A number of experimental results are reported to validate the proposed approach and compare it against an existing sufficient test.