Smart materials-based structural vibration isolation for minimizing product quality variation using h _∞ - Based optimal control

An H _∞-Based optimal vibration isolation system using patch-type piezoelectric actuators and sensors, suitable for application on high-precision manufacturing equipment that is being affected by external disturbances, has been designed. Reductions of the force transmitted through the structure range from approximately 5 to 30 dB in the frequency band of interest. Robust stability, nominal performance and robust performance have all been verified using the structured singular value, μ and simulation testing for the set of plants within a derived uncertainty set. In addition, the H _∞ controller is compared to an LQG-optimal controller designed for the same structure. The LOG controller, while achieving nominal performance comparable to the H _∞ controller and being of significantly lower order, was shown to be unstable via μ-analysis and simulation testing. Thus, the LOG design should not be applied to a machine where there is significant in-band model uncertainty. Use of light-weight patch-type piezoelectric actuators and sensors provides a low-cost, easily-installable way of applying this technique to manufacturing equipment requiring isolation from low-frequency disturbances.