Active isolation and damping of vibrations via Stewart platform

Abstract

In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples. The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orhtogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator: integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been done to test the isolator in micro-gravity environment. In the context of this research, another hexapod has been produced; a generic active damping and precision pointing interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.