Unification and Application of Wheel Traction Models in Multiple Terrain Conditions

Outdoor wheeled mobile manipulators dynamically interact with both manipulated objects and the underlying terrain, which may experience wheel-induced shearing and flow. Terramechanics models describe wheel-terrain interaction stresses precisely, but fail to show the wheel tractive mechanics intrinsically. Through experimental investigation, this paper establishes a linear relationship between wheel driving torque and traction across terrains of varying deformability. We conceptualize wheel-induced soil flow as comprising two components: a rim-adherent synchronous rotation flow that extends the effective lever arm of drawbar pull, and a counter-directional shear flow that induces wheel slowdown. This framework elucidates velocity and traction losses from particle displacement. A unified wheel traction model is proposed, incorporating fluctuations induced by wheel lugs. Experimental validation confirms the model's accuracy, while its online parameter identification enhances superior adaptation efficiency to terrain variations compared to terra-mechanics models. Based on this framework, speed, traction, and energy losses due to terrain deformation are precisely predicted, thereby facilitating an analytical loss function for wheeled mobile manipulator optimization. The model also demonstrates potential for traction control applications in wheeled mobile platforms.