Effect of number of wheels on high speed UGV traversability: Online terrain assessment approach

This paper addresses the problem of determining the maximum allowable speed (V _max ) of Unmanned Ground Vehicles (UGVs) traversing off-road heterogeneous rough/complex terrain. The maximum speed is calculated based on online terrain assessment and the vehicle’s characteristics; this speed achieves the high speed navigation without exceeding a predefined allowable range of transmitted force and moments (i.e., moments in the roll and pitch directions) to the vehicle’s frame. The proposed system enables UGV’s to change their speed autonomously and transit between terrains with different characteristics (e.g., pavement, rocky) safely. This paper proposes a computationally inexpensive approach to process acquired data and assess the terrain roughness. The proposed Roughness Index (RI) is used to represent the terrain roughness on a scale from 0.0 (highly rough to be traversed by a particular vehicle) to 1.0 (perfectly flat/smooth surface). A general vehicle model (workable for any vehicle size and wheel configuration) is presented in this paper. A closed form expression of the maximum allowable vehicle speed is developed. Simulation results obtained on real vehicles (e.g., military tank LEOPARD I) show the effect of increasing the number of wheels to improve the capability of a ground vehicle to traverse rough terrains at high speeds. In addition, the proposed terrain assessment system is a key module in UGVs navigation systems enabling them to be truly autonomous by providing the navigation system with the necessary information for path and speed planning.