LPV Modeling and Switched Control for EGR Valves with Dry Friction

Engine EGR (exhaust gas recirculation) valves are highly nonlinear due to its nonlinear friction, especially at the low-velocity region, where the friction increases sharply, resulting in a large steady-state valve displacement error. Multiple friction factors are considered in this paper using a switched LPV (linear parameter-varying) model, where the scheduling parameter is the friction coefficient as a function of valve velocity. Switched gain-scheduling LPV controllers are designed with hysteresis switching logic using the linear matrix inequality (LMI) convex optimization approach. The LPV controller performance is compared with that of PID controllers in the simulation study, showing a notable improvement in the system response performance and robustness.