Real-time measurement or estimation of crank-angle-resolved engine cylinder pressure may become commonplace in the next generation of engine controllers to optimize spark, valve timing, or compression ratio. Toward the development of a real-time cylinder pressure estimator, this work presents a crank-angle-resolved engine cylinder pressure estimation model that could accept inputs such as speed, manifold pressure and throttle position, and deliver crank-angle resolved cylinder pressure in real-time, at engine speeds covering the useful operating range of most engines. The model was validated by comparing simulated cylinder pressure with thirteen sets of cylinder pressure data, from two different commercial engines from two different OEMs. Estimated pressures were compared against the actual measured pressure traces. The average relative error is about 3% while the maximum relative error is 5%. Both can be improved with further tuning.
The long-term goal is to design an optimal hardware component for cylinder pressure estimation to be included in an embedded system for hardware-in-the-loop simulation or the next generation engine controllers. Toward that goal, the current model, which includes only the closed valve period at this time, was implemented in hardware. Tests show that the hardware-based model is capable of estimating crank-angle-resolved cylinder pressure at engine speeds up to 9000 rpm.