Non-linear observer for slip estimation of skid-steering vehicles

Accurate estimation of slip is essential in developing autonomous navigation strategies for mobile vehicles operating in unstructured terrain. In this paper, a sliding mode observer is firstly constructed to estimate slip parameters based on the kinematics model of a skid-steering vehicle and trajectory measurement. The stability of the sliding mode observer is given in a mathematical context. Slip estimation schemes using an extended Kalman filter and direct mathematical inversion of the kinematic equations are also presented for comparison purposes. It is shown that the non-linear sliding mode observer is more accurate than the other two methods. The robustness and superior performance of the sliding mode observer is demonstrated using both simulation and experimental results. A camera based system is used to measure the vehicle trajectory during experimental validation