Dynamic isotropic design and decentralized active control of a six-axis vibration isolator via Stewart platform.

the six-axis vibration isolation system is essential for high-precision space systems. Its architecture is always designed based on the cubic-configuration Stewart platform, whose six flexible modes generally have different natural frequencies resulting in multiple resonances at various frequencies such that a uniform capability of vibration isolation cannot be achieved for the six flexible modes. To solve this problem, the dynamic isotropic design of the isolator is studied to make the six nonzero natural frequencies identical. The free-floating state of the isolator is taken into account and six design criteria of the dynamic isotropy are obtained. The internal relation between the dynamic isotropy and the kinematic isotropy is revealed and discussed. A decentralized active controller is then investigated for the isolator of dynamic isotropy. The controller decouples the six-axis vibration control into six identical control of a single-axis vibration isolator. The same control gains in each single-axis isolator reaches the optimum simultaneously for all the flexible modes such that a best performance of vibration isolation can be achieved. Finally, we present an example of an isolator of dynamic isotropy. With the proportional plus integral compensator, the uniform corner frequency and optimal active damping can eventually be achieved. [ABSTRACT FROM AUTHOR]