Now a new plan is put forward that an optimal tension controller is designed by using tension state equation, and still further the tension comp.

A state dependent Riccati equation (SDRE) based controller was designed, and the controller's gain relates to the state, which results in complexity in computing but good effects of control.

This paper discussed the structure and principle of EPS system, established the state space equation of EPS, designed PID close loop controller, and set the parameters.