System and Control Design of a Voice Coil Actuated Mechanically Decoupling Two-Body Vibration Isolation System

Structural modes such as decoupling of a mechanical subsystem are in general unwanted effects in high precision positioning systems. This paper introduces intentional decoupling as a design choice by using a connecting flexure-damper configuration that allows high bandwidth control of a stiff first subsystem and lower bandwidth control of a bulky second subsystem at the same time. An experimental setup of a single degree of freedom system with one body intentionally decoupling above 190 Hz is developed and analyzed, showing good agreement with the analytical modeling. A model-based H_∞-controller to actively control the position of the first body is designed and the damping in the system is revealed as an important design parameter to reduce the control effort around the decoupling frequency. It is demonstrated that with the derived controller, the first and the second body of the resulting prototype can simultaneously be controlled with bandwidths of 1.4 kHz and 180 Hz, respectively. When exposed to a disturbance profile with 12.4 μm root mean square (rms) value in the laboratory environment, the remaining rms positioning errors for the actively and passively controlled subsystems are as small as 0.12 μm and 0.81 μm, respectively.