Abstract
Successful operation of off-road mobile robots faces the challenge of mobility hazards posed by soft, deformable terrain, e.g. sand traps. The slip caused by these hazards has a significant impact on tractive efficiency, leading to complete immobilization in extreme circumstances. This paper addresses the interaction between dry frictional soil and the multi-legged wheelleg concept, with the aim of exploiting its enhanced mobility for safe, in-situ terrain sensing. The influence of multiple legs and different foot designs on wheel-leg-soil interaction is analyzed by incorporating these aspects to an existing terradynamics model. In addition, new theoretical models are proposed and experimentally validated to relate wheel-leg slip to both motor torque and stick-slip vibrations. These models, capable of estimating wheelleg slip from purely proprioceptive sensors, are then applied in combination with detected wheel-leg sinkage to successfully characterize the load bearing and shear strength properties of different types of deformable soil. The main contribution of this paper enables non-geometric hazard detection based on detected wheel-leg slip and sinkage.