Engine throttle control with disturbance observer

The dynamic response of the electric throttle control (ETC) system is vital to the automobile engine control performance. In this article, we report a new control design with the disturbance observer approach for the servo control of the engine throttle valve. Previous researches assumed a linear mass-spring-damper model with stiction around the limp-home position. We discovered, through closed-loop system identification experiments, that the torque-displacement relation around the limp home position is also linear, but with high stiffness. For the servo control of the ETC system, we analyze the nonlinear spring effect on the robustness of the resulting closed-loop system, and discovered that a control design based on the low spring constant area is robust to the ten-fold spring constant variation in the limp home region. We design and implement a two-degree-of-freedom control system with a disturbance observer structure in the feedback loop. The experiment results show very good command response regardless the preload spring effect and excellent disturbance rejection performance against the friction force.