The artificial potential field method is frequently employed for obstacle avoidance both of mobile robots and of manipulator arms. This paper extends previous results for planar problems to the general n-dimensional case. The complexity is reduced by projecting the n-dimensional workspace onto a 2D subspace called operation plane. Furthermore, only the closest obstacles are taken into account when designing the artificial potential field. Still, global convergence is achieved. The methodology is illustrated with several numerical examples.

This paper introduces a sliding mode control strategy for tracking the gradient of an artificial potential field. The control methodology is applicable to fully actuated holonomic robotic systems with n-degrees of freedom. The controller yields exact tracking of the gradient lines and is invariant with respect to parametric uncertainty and disturbances in system dynamics. A detailed case study for mobile robots introduces the equilibrium point placement method for designing harmonic planar potential fields for circular obstacle security zones. Diffeomorph mappings can be utilized for more complex obstacle security zones. The gradient of the harmonic potential field is shown to always lead away from the obstacle security zone and to continuously approach the goal point.>

Autonomous navigation in unknown cluttered environments is one of the corner-stones of future applications of mobile robots. The complexity even of seemingly simple problems like point-to-point travel, to be solved in real-time, calls for a hierarchical system architecture. The authors present a three-layered path control system with three modules "global planning", "local navigation", and "collision avoidance". Each module is restricted to a subtask of limited competence and responsibility, allowing for on-line implementation within the associated time frame. Suitable module interaction provides the desired behavior of the overall system. This paper summarizes the main idea of each of the three modules. Experimental results with the Siemens mobile platform ROAMER illustrate the methodology and performance of the path control system in unprepared cluttered environments.>