Traction Control of Planetary Rovers on Prescribed Trajectories with Wheel-Fighting Consideration

To reliably localize and control planetary rovers, their controllers must keep the wheels away from traction loss. In this paper, a fast traction control system for rovers is developed that tracks dynamic trajectories, leveraging their redundant control directions. Trajectory-tracking performance is guaranteed by stabilizing an input–output linearized nonholonomic model of the system. A novel methodology is proposed to determine the control actions that optimally distribute the tractive forces among the wheels without affecting the tracking performance. The methodology uses the knowledge of wheels’ friction coefficients and estimation of normal and tractive forces based on a nonholonomic rover model. The novelty is in redefining the optimization problem in both lateral and longitudinal directions, which requires minimum information about wheel–ground interactions and leads to linear optimality conditions. The notion of required force/moment at the rover’s center of mass is proposed to define reference directions for tractive forces and isolate fighting wheels whose tractive forces are suppressed by finding suboptimal control actions. The proposed traction control system is implemented on a six-wheel rover modeled after the Lunar Exploration Light Rover, and its efficacy against the conventional pseudo-inverse solution is demonstrated in a software-in-the-loop simulation environment of hard frictional ground using Vortex Studio.