Robust vibration isolation by frequency-shaped sliding surface control with geophone dynamics

The Frequency-Shaped Sliding Surface Control (FSSSC) has been recently applied to the Active Vibration Isolation System (AVIS) and the robust skyhook performance is experimentally validated. However, the performance of this approach is theoretically limited by the sensor dynamics. This paper generalizes the FSSSC approach as a two-step AVIS control design method. The first step is to design the sliding surface which determines the designed performances. The second step is to design the regulator which guarantees the convergence of the system dynamics. As long as this convergence is guaranteed, the designed performances would be realized. The vibration isolation of the original plant is therefore transformed to the regulation of a new system which is composed of the original plant and the sliding surface. As the regulator design has been well studied in the literature, this paper focuses on the sliding surface design. An example sliding surface design to achieve low-frequency vibration isolation is provided. The FSSSC of an example 1-DOF plant using both original and the improved sliding surface are compared. Theoretical calculations show that the improved sliding surface has no theoretical performance limit and achieves robust vibration isolation at much lower frequencies than the original design.