Fast computation of wheel-soil interactions for safe and efficient operation of mobile robots

Hazardous terrains pose a crucial challenge to the operation of mobile robots, especially for military applications such as surveillance, casualty extraction, etc. To enable their safe and efficient operations, it is necessary to detect the terrain type and to modify operation and control strategies in real-time. Fast wheel-terrain interaction models suitable for real-time applications are thus important. In this paper, closed-form analytical expressions of the integrated stress equations were derived by quadratic approximation of the stresses along the wheel-soil interface. Meanwhile, the bulldozing resistance and the influence of grousers are also modeled for more accurate prediction of the vehicle motion. A non-iterative method was proposed to estimate the wheel-soil contact geometry, i.e., the entry angle, according to the wheel load, by approximating the vertical pressure distribution with a sinusoidal function or linear function depending on the sinkage exponent of the soil. Computation efficiency is improved by avoiding traditional recursive solution of the model under binary search. Online prediction and real-time control could be possible by using the developed closed-from wheel-soil interaction model and the entry angle estimator.