Identification of Ground Vehicle Steering System Backlash

This paper presents an identification method for the backlash embedded in ground vehicle steering systems. A backlash model relates the steering system output—road-wheel steering angle (RWSA) to the input—hand-wheel steering angle (HWSA). An accurate backlash model is helpful in achieving a better control performance or a more precise reference model for vehicle dynamic control. The proposed identification procedure consists of two parts. First, the unmeasurable RWSA is estimated by manipulating equations of a two degrees-of-freedom vehicle lateral dynamics model, where the signals related to the vehicle motion are obtained from an inertial measurement unit and global positioning system, and the estimation problem is transformed to solving an algebraic equation by optimization tools. Second, by applying a recursive general identification algorithm, parameters that characterize the steering system backlash model are identified recursively from the reconstructed RWSA and measured HWSA. Vehicle road tests have been carried out and the experimental results show effectiveness of the proposed identification method. The developed algorithm can be applied both on-line and off-line, and its on-line implementation process is also presented.