An effective pole-zero cancellation in feedforward controllers for nonminimum phase systems

A new pole-zero cancellation technique using a modified series approximation is proposed for the feedforward controller for nonminimum phase systems. The gain of the system with the proposed feedforward controller is close to 1 for wider frequency range, in comparison with other techniques. The tracking error of this method depends on the p-th order difference of the desired trajectory. Therefore, this method could give smaller tracking error in various reference trajectories and in high speed operation. The tracking errors are analyzed and compared with other methods in terms of the location of an unstable zero and the reference trajectory. The effectiveness of the proposed method is shown in the simulation.