Motion planning of a wheeled mobile robot with slip-free motion capability on a smooth uneven surface

Abstract

The motion of a wheeled mobile robot on uneven terrain leads to asymmetry in the position of the wheel-terrain contact locations. This asymmetry has important kinematic and dynamic implications for several of the wheeled mobile robots studied in literature. It leads to kinematic slipping at the wheel-ground contacts-this slip is required for the vehicle to possess functional mobility. This slip leads to unpredictable load distribution in the system and poor dead-reckoning. This article presents a motion planning algorithm for a class of terrain adaptive mobile robots (TAMR) that possess slip-free motion capability on uneven terrain. The motion planning algorithm can be divided into two phases. Phase I is a global (coarse) search for a potentially feasible path on the uneven terrain. Phase II involves refining this path using a thorough mechanics (kinematic/force analysis) approach to confirm its feasibility. It should be noted that the kinematic analysis on uneven terrain involves solution of a mixed holonomic-nonholonomic set of equations with characteristics that are distinct from that of mobile robots on even ground. This article only addresses "smooth" uneven terrain whose curvature characteristics are such that a wheel never possesses multiple contacts with the terrain.