Design of H_∞ controller for precise positioning system

The control system of a positioning mechanism with resonance and Coulomb friction has been designed using H_∞ control theory, and the control performance has been verified by computer simulation and experimental analysis. DGKF type H_∞ control with scalar weighting factors and GD type H_∞ control with frequency-dependent weighting function based on integral action were utilized for designing the control system. The followings have been confirmed from this study: (1) H_∞ control has good robustness properties for a wide range of operating conditions in the presence of external disturbances such as Coulomb friction. (2) DGKF type H_∞ controller presents better convergence and robustness properties than GD type H_∞ controller.