Optimal Profile Tracking for an Electro-Hydraulic Variable Valve Actuator using Trajectory Linearization

The camless valve is able to provide flexible engine valve profiles (timing, duration, lift, etc.) to improve the performance of internal combustion engines. To provide a precise valve profile of an electro-hydraulic variable valve actuator (EHVVA) for the desired engine performance, an optimal tracking controller for the valve rising duration and profile is designed in this paper. A nonlinear model, elaborating the system pressure dynamics determining the valve rising duration, is developed and linearized along the desired rising valve trajectory. Based on the trajectory linearization, a linear quadratic tracking (LQT) controller is designed with Kalman optimal state estimation. The equilibrium control resulted from the trajectory linearization is used as the LQT feedforward control. The control performance is compared with that of baseline controllers through both simulation study and bench tests. The transient and steady-state validation results confirm the effectiveness of proposed control scheme.