Sinkage and slippage estimation for an articulated vehicle

This paper describes an approach to estimating in real-time the degree to which an articulated robotic vehicle is undergoing wheel slip andor sinkage in soft terrain. Robotic vehicles generally have hazard avoidance sensors which measure the shape of the sensible surface, and these can be used to predict what the articulation pose of the vehicle will be as it moves over the surface. An articulated vehicle (one with three or more wheels on each side) can directly measure the shape of the loadbearing surface by combining inclination and articulation sensing. Delays between the actual articulations and the expectations can be explained by wheel slippage. Differences between the expectation and the actual articulations can be explained by sinkage below the sensed surface. If one assumes that successive wheels on each side follow the same profile as the front wheel (sinking the same amount, if any, into the soil), then it is possible to estimate sinkage and slippage separately. A Maximum-A-Posteriori estimation procedure forinalizing this heuristic approach is developed and simulated, and the results presented and discussed