# Development of Active Microvibration Isolation System for Precision Space Payload
###### Abstract  
In this study, an active microvibration isolation system is developed for precision space payload. Vibrational environment affects the performance and reliability of measuring instruments. To improve the measurement accuracy of the precision space payload, an active vibration isolation system based on eight vibration isolation modules, which are applied for microvibration isolation on the satellite, is designed. A vibration suppression control strategy for multiple degrees of freedom is studied. A hybrid control method involving a feedback and a feedforward controller based on a nonlinear tracking differentiator and an nth-order weak integrator, respectively, was adopted to optimize the suppression effect of microvibration. As a result, the microvibration of the order of mg can be reduced to the order of \(\upmu\)g through the active control of modules. Research experiment results show that the root cumulative power spectral density of the systemic sensitive frequency band in the range of 0.5-200 Hz, i.e., microvibration frequency band in the optical reference cavity, has been reduced to in the order of \(\upmu\)g in three directions, which satisfied the requirements of aerospace engineering. active vibration isolation; hybrid control; low-frequency band; three-directional microvibration isolation; precision space payload +
Footnote †: journal: Applied Sciences  
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[PERSON], [PERSON], [PERSON], [PERSON], L. Development of Active Microvibration Isolation System for Precision Space Payload +
Footnote †: journal: Applied Sciences  
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Footnote 1: email: {  
(1) the optical reference cavity should be designed to minimize the sensitivity to vibration [15; 16], and (2) the transmission efficiency of microvibration should be suppressed as much as possible in the transmission path of microvibration [17; 18]. For the optical clock at an uncertainty level of 1 \(\times\) 10\({}^{-18}\) frequency, the frequency instability of the optical reference cavity of 3 \(\times\) 10\({}^{-16}\) is required. Moreover, the vibrational environment of the cavity cannot be higher than 1.5 \(\times\) 10\({}^{-5}\) g because the vibration sensitivity of the optical cavity will be under 2 \(\times\) 10\({}^{-11}\)/g [19] as per the existing conventional reference cavity design. The traditional passive vibration isolation system is widely used because of its high reliability and excellent high-frequency vibration isolation performance. However, in the lower frequency range, the passive vibration isolation system needs to reduce the resonant frequency as much as possible to obtain better vibration isolation performance [20; 21]. Nevertheless, the stability of this design makes it difficult to support such a precise system as an optical clock. Therefore, to fulfill the demand for high-precision vibration isolation in space, the active vibration isolation technology is the main method used. The active vibration isolation system developed at Eindhoven University of Technology adopts the design of multiple SISO control loops as a basis and uses a method with acceleration and position feedback to achieve a maximum suppression efficiency of 97% within 100 Hz, and optimizing the leveling performance [22]. The active vibration isolation system junction developed by Huazhong University of Science and Technology uses a centralized control method to suppress vibrations of 200 Hz by 94.8% through a sensor and actuator matrix and a controller design based on absolute velocity feedback [23]. The active vibration isolation systems of these ground tests have proven to exhibit excellent performance, but their volume and weight are relatively large, which are limited by space platform resources. For space high-precision payloads, the application of active vibration isolation technology is also gradually developing. The MVIS-II developed by the Kirtland Air Force Laboratory of the United States has a 20 dB attenuation effect in the frequency band greater than 5 Hz, and a flight test was carried out in 2006 [24].