Effect of normal force dispersion on the mobility of wheeled robots operating on soft soil

A number of applications of wheeled robots, including planetary exploration rovers and rescue missions, require that the vehicle operates in a non-structured environment. Optimizing the vehicle mobility is of key importance in such applications. Reduced mobility can limit the ability of the robot to achieve the mission goals, or even render it immobile in extreme cases. In this paper, the effect of normal contact forces on mobility is reported. A performance indicator based on the force distribution is defined and used to compare different vehicle configurations. The validity of this indicator was assessed using both simulation and experimental results obtained for a six-wheel rover prototype. Results suggest that modifying the robot configuration to alter the normal force distribution can lead to increased traction force available at the wheel-terrain interfaces, thus improving the mobility.