Integrated System Identification 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 fairly difficult to maintain the cam phase at the desired constant level with an open-loop controller. As a result, multirate closed-loop system identification is a necessity. For this study, multirate closed-loop system identification, PRBS q-Markov Cover, was used for obtaining linearized system models at different engine operational conditions; and the output covariance constraint (OCC) controller, an H₂ controller, was designed based upon the identified model and evaluated on the VVT test bench. Performances of the designed OCC controller was compared with those of the baseline PI controller on the test bench. Results show that the OCC controller uses less control effort and has less overshoot than those of PI ones.