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Output tracking control is a challenging problem. This paper introduces a new design procedure for output tracking control of nonminimum phase systems. This new controller achieves stable ε-tracking of a reference profile given in real time via a causal inversion approach. In this approach, the nonminimum phase system is first stably inverted on-line to obtain both desired (and stable) state and input trajectories. Then an H∞ optimal controller is used to stabilize the closed-loop system. In contrast to stable inversion, the causal inversion approach does not require precalculation. In contrast to nonlinear regulation, the causal inversion approach avoids the numerical intractability of solving nonlinear PDEs. As an example of the application, a causal inversion-based controller is designed for tip trajectory tracking of a one-link flexible manipulator. Simulation results demonstrate its effectiveness in output tracking.
Date of Publication: Jan. 2006