Robust parametrized controller design with an application to exhaust gas recirculation (EGR) system

An exhaust gas recirculation (EGR) control system for automotive application is briefly presented. Robustness is one of the main issues in this particular system due to nonlinearities, time delays, and the effects of complex exhaust gas dynamics. It was found that a good approximation of the system dynamics consists of a first order transfer function with a time delay where both transfer function coefficients and the time delay depend on the reference signal (desired EGR(%)). Moreover, it is sufficient to identify only four models corresponding to four different values of desired EGR (%) and assume interpolation for transfer function coefficients to characterize the system dynamics. Since the value of the reference signal is available in real time the controller design can be reduced to four controllers corresponding to four identified models and interpolation for coefficients of the controller transfer function in cases when the value of desired EGR (%) is between the assumed values. Simulation results for such designs are presented.