This paper presents a steering controller for autonomous vehicles during lane-change process with unreliable steering systems. A steering system model with a brushless direct current (BLDC) motor as actuator is built, which includes the nonlinearities of the steering system. The characteristics of the nonlinearities of delay, friction and backlash are investigated. Based on the above analysis, a model reference adaptive controller (MRAC) is implemented as the steering controller. Simulations are carried out to validate the effectiveness of the proposed controller. Results show that the controller has satisfying lane-change performance on vehicles with unreliable steering factors, and has strong robustness against even growing nonlinearities.

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