Robot Navigation in Multi-terrain Outdoor Environments

This paper presents a methodology for motion planning in outdoor environments that takes into account specific characteristics of the terrain. Instead of decomposing the robot configuration space into "free" and "occupied", we consider the existence of several regions with different navigation costs. In this paper, costs are determined experimentally by navigating the robot through the regions and measuring the influence of the terrain on its motion. We measure the robot's vertical acceleration, which reflects the terrain roughness. The paper presents a hybrid (discrete-continuous) approach to guide and control the robot. After decomposing the map into triangular cells, a path planning algorithm is used to determine a discrete sequence of cells that minimizes the navigation cost. Robot control is accomplished by a fully continuous vector field that drives the robot through the sequence of triangular cells. This vector field allows smooth robot trajectories from any position inside the sequence to the goal, even for a small number of large cells. Moreover, the vector field is terrain dependent in the sense it changes the robot velocity according to the characteristics of the terrain. Experimental results with a differential driven, all-terrain mobile robot illustrate the proposed approach.