Real-time control of non-minimum phase XY table system using trajectory-adaptive ZPETC

In XY Table system, perfect tracking control (PTC) with zero tracking error is desired. This can be achieved by introducing a feed-forward controller that acts as an inverse of the system closed-loop transfer function and cancelling all poles and zeros of the closed-loop system. Adding feed-forward controller in axis controller can prompt the response of the single axis. Consequently, minimize the tracking error of each individual axis. This result an overall transfer functions of unity between the desired output and the actual output. In non-minimum phase (NMP) system where one of the zeros located outside the unit circle, unfortunately, this feed-forward controller could not be implemented as this would result an unstable tracking control. Thus, this paper proposes a Trajectory-Adaptive ZPETC without factorization of zeros polynomial scheme in which the optimum set of α_k are automatically tuned online to reduce this NMP zeros problem. Simulation and experimental results of the real-time control of XY Table show that the tracking performance for lemniscates movement is significantly improved.