Optimization of PID Control for Engine Electronic Throttle System Using Iterative Feedback Tuning

The Electronic Throttle Control (ETC) system is more and more used and increasingly becoming a standard part of the engine. It controls the amount of air intake into the cylinders by precisely positioning the throttle plate at the desired opening. An ETC system provides the possibility of improving the overall engine and vehicle performance because with such a mechanism, the engine controller can decide and set the throttle position not only based on driver intention, but also taking into consideration the specific engine operation mode information, such as safety factors, emission constraints, etc.

After the throttle position target is determined, the requirement for the ETC system is that the throttle plate should achieve the commanded position as accurately and as quickly as possible. In many cases the controller is designed by first establishing a model of the electronic throttle system using experimental identification. However, due to such nonlinear effects as static friction, dynamic friction, and nonlinear return springs etc., identification of a model for the electronic throttle system sometimes does not give good results. This makes a controller design based on the model far from optimal. Iterative Feedback Tuning (IFT) is a method for directly tuning the controller parameters based on the data of closed loop experiments without the need for an explicit model of the system. This property makes IFT an attractive method for ETC design. In this paper a Two-Degree-of-Freedom (2-DOF) Proportional-Integral-Derivative (PID) controller for an engine electronic throttle system is designed and the PID control gains are optimized using IFT. The application shows that the IFT method gives very good performance for controller tuning.