This paper presents a modified Tustin transformation which can be used in the design process to improve controller performance significantly by reducing control input fluctuations caused by unfavorable controller pole locations. An important application is the design of robust performance controllers, which can exhibit control input fluctuations due to the rigidity of the known optimal solutions. This modified Tustin transformation utilizes a scaling factor to map the stability region of the continuous domain to a region in the discrete domain which excludes the undesirable points near z = −1. In comparison to the standard Tustin transformation, this scaling factor affects the mapping of only the points in the continuous domain corresponding to high frequencies. Hence, a critical feature of this modified transformation is that it preserves the mapping from the origin in the continuous domain to point z = 1 in the discrete domain, because this pole location corresponds to integral control. This modified Tustin transformation is applied to the robust performance controller designs for the electrohydraulic actuator. The objective is to perform a number of controller designs with different scaling factors and then determine the design which provides the best compromise between improved controller performance and achieved system performance. The simulation results and experimental data demonstrate that a scaling factor equal to 1.2 improves controller performance and maintains system performance when compared to the controller design using the standard Tustin transformation. Specifically, the control input signal energy is reduced by 53%, the system overshoot is reduced by 47%, and the settling time is reduced by 42%.

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