Coordinated path following control of multiple wheeled robots using linearization techniques

The paper addresses the problem of steering a fleet of wheeled robots along a set of given spatial paths, while keeping a desired inter-vehicle formation pattern. This problem arises for example when multiple vehicles are required to scan a given area in cooperation. In a possible mission scenario, one of the vehicles acts a leader and follows a path accurately, while the other vehicles follow paths that are naturally determined by the formation pattern imposed. The paper solves this and other related problems using a simple algorithm that builds on linearization techniques and gain scheduling control theory. Using this set-up, path following (in space) and inter-vehicle coordination (in time) are almost decoupled. Path following for each vehicle amounts to reducing a conveniently defined generalized error vector to zero. Vehicle coordination is achieved by adjusting the speed of each of the vehicles along its path, according to information on the position of all or some of the other vehicles. No other information is exchanged among the robots. The set-up adopted allows for a simple analysis of the resulting coordinated path following control system. The paper describes the structure of the coordination system proposed and addresses challenging problems of robustness with respect to certain types of vehicle failures.