H∞/extension stability control of automotive active front steering system

In order to solve the contradiction between the control output and the control effect, especially in extreme conditions, this paper designs a H∞/extension controller based on active front steering system by introducing the extension control into H∞ mixed sensitivity control about sensitivity function S/T problem. The proposed controller can transform the control information under the unstable domain into the eligible value range by using dependent degree to tune the control output. And ultimately, the combination of H∞ norm and extension transformation extends the stable region of the system. The results of the simulation and vehicle test show that the proposed H∞/extension controller can effectively deal with the contradiction between the control effect and the control output under extreme condition, and achieve satisfactory control effect with the control output as small as possible under normal condition.