Engine Control Using Torque Estimation

In recent years, the increasing interest and requirements for improved engine diagnostics and control has led to the implementation of several different sensing and signal processing technologies. In order to optimize the performance and emission of an engine, detailed and specified knowledge of the combustion process inside the engine cylinder is required. In that sense, the torque generated by each combustion event in an IC engine is one of the most important variables related to the combustion process and engine performance.

This paper introduces torque estimation techniques in the real-time basis for engine control applications using the measurement of crankshaft speed variation. The torque estimation scheme presented in this paper consists of two entirely different approaches, “Stochastic Analysis” and “Frequency Analysis”. The background as well as technical implementations of these approaches is presented in this paper, along with extensive results obtained from a four-cylinder S.I. engine while varying the engine speed and load. Both approaches are analyzed and compared in the sense of estimation accuracy and computational requirements, and feasibility for the real-time engine control application. Results show that both methods allow to estimate the indicated torque based on the crankshaft speed measurement while providing not only accurate but also relatively fast estimations during the computation processes.