Extended Command Governors for Constraint Enforcement in Dual-Stage Processing Machines

This manuscript presents a scheme for the constrained control of a dual-stage system used in precision manufacturing. The system consists of two stages, a fast and a slow stage, whose actuators have different bandwidths. The fast stage is primarily constrained in its range of operation, and the slow stage is primarily constrained in allowable velocity and acceleration. The constrained control is based on the extended command governor, which is a constraint-enforcement scheme used for closed-loop systems subject to state and control constraints. A method of dividing the motion between fast and slow stages is presented which is based on tracking a minimal-motion reference for the slow stage. The extended command governor scheme is modified to simultaneously ensure constraint-admissible tracking of the minimal-motion reference and machining of the desired manufacturing pattern. Numerical simulation results are reported, showing successful tracking and constraint enforcement.