Trajectory Tracking and Stair Climbing Capability Assessment for a Skid-Steered Mobile Robot

This paper presents derivation of a trajectory tracking and stair climbing stabilization controller for a 4-wheel driven skid-steered wheeled mobile robot (SSWR). The robot vehicle is modeled with six degrees of freedom (6DOF) rigid body equations which are later simplified for planar and pitched movement. An efficient control algorithm, called trajectory linearization control (TLC), is used to tackle the challenges posed by nonlinearities of the model. In TLC, state dynamics are linearized along the trajectory being tracked. Kinematics and dynamics of the vehicle are controlled individually by feedback loops, where the former constitutes the outermost loop. Simulation results promise trajectory tracking with desired accuracy. For the test prototype with current physical configuration, an upper limit is found on steepness of staircase it can safely climb. 3-sigma Monte Carlo analysis is used to show robustness of the controller to parametric perturbations.