Robust dynamic stiffness design of a linear servo system

As a popular controller used in the industrial servo drives, the pseudo derivative feedback with feedforward (PDFF) scheme has 3 parameters for tuning to achieve a good trade-off design between tracking and dynamic stiffness. However, the two parameters in the feedback path of the PDFF controller are restricted to constant for design simplicity that limits its dynamic stiffness. This paper presents a control design, namely "advanced PDFF controller," in that the PDFF scheme is kept, but two feedback constant gains are extended to be dynamic. An H^∞ mixed sensitivity design is presented to systemically obtain a robust controller for dynamic stiffness design in a linear servo system. Simulation and experimental results are given to show the effectiveness of the proposed design method.