Based on insufficient studies of the tractive performance of a planetary rover's rigid wheels in soft soil and hard mixed soil terrains, a method for studying the tractive performance is presented. The Wong-Reece' interaction model was used as the dynamic model for wheel-soil contact. The sinkage model and the drawbar pull force model were modified and then verified with experimental results. Based on the Hertz contact theory, a nonlinear friction spring damping model was adopted as the

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... drock contact model. An additional terrain hardness array was introduced for setting and recognizing the mixed terrain with ground mechanics parameters. With the platform for co-simulating the navigation and dynamics of a planetary rover, the simulation program was developed to dynamically simulate the whole planetary rover with two wheel-ground contact models. Taking the Mars rover as an example, its whole model was established with the MSC.Adams software. The dynamic simulation of the Mars rover on the soft terrain and mixed terrain was carried out respectively. The simulation results show that the Mars rover's velocity fluctuates greatly on the mixed terrain, and that the Mars rover gains greater drawbar pull force when traveling on the mixed terrain than on the only soil terrain.