Modeling and automatic real-time motion control of wheeled mobile robots among moving obstacles: theory and applications

Abstract

Addresses the interesting and difficult problem of real-time planning and efficient motion control of a rigid mobile robot to dynamically avoid obstacle(s) as the latter moves. Most techniques described so far in the literature deal with the simpler problem of generating (generally off-line) a path among stationary obstacles. For practical purposes, however, obstacles are not always static and most interesting environments are in general not known precisely and/or time varying. In particular, robots capable of manoeuvring among moving obstacles will be capable of accomplishing a much larger and more versatile class of tasks. The authors tackle this problem from a different angle and present a powerful real-time collision avoidance technique using complex potential functions and conformal mapping. Based on complex potential models, a feedback controller with constant robot curvilinear velocity is derived for the automatic guidance and motion control of the mobile robot. The goals of the velocity feedback are twofold: (1) lowering the overhead of the higher level decision-making control and placing it in the lower level motion control, (2) allowing the robot to smoothly rotate and translate with a constant curvilinear speed to account for the physical limitation of the robot device dynamics. The idea is to navigate through the environment using only sensory information, which makes the method insensitive to physical changes such as moving obstacles. At the heart of the technique is the exploitation of the powerful and fundamental tool of conformal mapping to derive the path solution for obstacles of arbitrary shapes. Finally application results are presented which indicate the potential value of the theory and methodology. >