Predictive path parameterization for constrained robot control

For robotic systems tracking a given geometric path, this paper addresses the problem of satisfying input and state constraints. According to a prediction of the evolution of the robot from the current state, a discrete-time device called path governor (PG) generates on line a suitable time-parameterization of the path to be tracked, by solving at fixed intervals a constrained scalar look-ahead optimization problem. Higher level switching commands are also taken into account by simply associating a different optimization criterion to each mode of operation. Experimental results are reported for a three-degree-of-freedom PUMA 560 manipulator subject to absolute position error, Cartesian velocity, and motor voltage constraints.