Integrated System ID and Control Design for an IC Engine Variable Valve Timing System

This paper applies integrated system modeling and control design process to a continuously variable valve timing (VVT) actuator system that has different control input and cam position feedback sample rates. Due to high cam shaft torque disturbance and high actuator open-loop gain, it is also difficult to maintain the cam phase at the desired constant level with an open-loop controller for system identification. As a result, multirate closed-loop system identification becomes necessary. For this study, a multirate closed-loop system identification method, pseudo-random binary signal $q$-Markov Cover, was used for obtaining linearized system models of the nonlinear physical system at different engine operational conditions; and output covariance constraint (OCC) controller, an $H2$ controller, was designed based upon the identified nominal model and evaluated on the VVT test bench. Performance of the designed OCC controller was compared with that of the well-tuned baseline proportional-integral (PI) controller on the test bench. Results show that the OCC controller uses less control effort and has significant lower overshoot than those of PI ones.