Estimation of Slip Ratio and Side Slip Angle of Wheeled Planetary Rovers Based on Trace Imprint

This paper proposes a method to estimate the wheel slip ratio and side slip angle of wheeled rovers by processing images of wheel trace imprints. The proposed method extracts structural features from trace imprint images, such as the trace unit, trace contour, and angle between the centerline of the trace unit and contour. The relationships between the structural trace imprint features and the wheel slip ratio and side slip angle have been revealed after a study of the underlying mechanism of trace imprint formation, with consideration of the kinematics of the wheel lug and lug-soil interaction. These relationships are then used to estimate wheel slip ratio and side slip angle. Compared with the existing estimation methods, the proposed method can estimate longitudinal slippage and lateral drift simultaneously that typically occur in planetary rovers during traverse of cross slopes. The effectiveness of the proposed method has been demonstrated by experiments using a rover wheel test-bed under various conditions.