Six-axis vibration isolation system using soft actuators and multiple sensors

Several types of Stewart platforms have been implemented by research groups to examine design and control issues in six-axis vibration isolation for space-based systems. Hood Technology Corporation and the University of Washington have taken the lessons learned from these various designs and developed a new hexapod that addresses the requirements of the Jet Propulsion Laboratory's planned spaceborne interferometry missions. This system is unique in its very soft axial stiffness (3-Hz corner frequency) for active isolation and pointing control, custom-designed voice coil actuator with a large displacement capability, and elastomeric flexures both for guiding the actuator and providing pivots at the end of each strut. In addition, there are four sensors in each strut for control topology design and evaluation. An overview of this unique six-axis isolator design and a summary of the control results for various sensor topologies, including multisensor and frequency-weighted isolation and pointing control, are presented. Controllers that experimentally achieved 20-25-dB reduction in vibration in all six degrees of freedom across the bandwidth of interest (5-20 Hz) are shown.