Robust fixed-structure controller design of electric power steering systems

This paper presents a two-degree-of-freedom controller structure for electric power steering systems. The controller is synthesized using a hybrid linear matrix inequality and genetic algorithms optimization. Robust stability is studied for both sector-bounded and passive uncertainties resulting in a system of linear matrix inequalities (LMIs) and a linear matrix equality (LME). This system of LMIs/LME defines a guaranteed cost H₂ optimization subject to an H_infin-norm performance as well as a strict-positive-real constraints. Experimental results involving human-in-the-loop show that the control design did satisfy the criteria for robust control and performance. Furthermore, the ease-of-tuning of the proposed controller structure makes it possible to improve the steering ldquofeelrdquo.