This paper presents the gross motion characteristics of articulated wheeled vehicles with slip-free motion capability on several kinds of smooth uneven surfaces. These vehicles possess variable length axles to eliminate kinematic slipping at the wheel-surface contacts. A numerical procedure to solve for the combined holonomic-nonholonomic set of equations that result from considering the exact kinematics of rolling on uneven surfaces is presented. The article provides insight into the relationship between variations in the axle lengths and kinematic parameters such as path curvature and vehicle-surface contact geometry.

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.