In-situ evaluation of terrain mechanical parameters and wheel-terrain interactions using wheel-terrain contact mechanics for wheeled planetary rovers

Physical space exploration missions usually include exploring craters that are composed of various slopes and covered with fine regolith. Wheeled mobile robots (WMRs), commonly known as rovers, are widely used in these missions to find a host of information on topography, mineralogy, geological processes, etc. In traditional terramechanics theories, at least seven experiments under various slip ratios are required to estimate the terrain parameters and drawbar pull that determines a WMR's slope climbing capability. Moreover, the wheel sinkage—an important index that indicates whether the fine and soft planetary regolith would become a dangerous trap—cannot be estimated in-situ currently. In this paper, highly coupled terramechanics equations are simplified into closed-form analytical models, whose effectiveness is experimentally validated after wheels enter quasi-static conditions. Based on these validated equations, the goal of in-situ estimation of terrain parameters, drawbar pull, and wheel sinkage can be accomplished by directly measuring physically measureable quantities. Thus, wheeled rovers will have the ability to perceive the planetary regolith's mechanical properties and the wheels’ running condition by mounting an instrumental wheel that contains a rotation force/torque sensor.