Design of an Active Low Frequency Vibration Isolation System for Atom Interferometry by Using Sliding Mode Control

Abstract

Active vibration isolation is gaining increased attention in the ultra-high precision application of atom interferometry to effectively treat the unavoidable ground vibration. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. The system level simulation model is established by Simulink software, The simulation results demonstrate the asymptotic stability of the system and the robustness of the control algorithm. Compared with the conventional lead-lag compensation type controller, the algorithm adopted uses sliding mode control, taking advantage of its easy computer implementation and its robust high performance properties. With the feedback path closed, the system acts like a spring system with a natural resonance frequency of 0.02 Hz. The vibration noise in the vertical direction is about 20 times reduced during 0.1 and 2 Hz, The experimental results verify that the isolator has significant vibration isolation performance, and it is very suitable for applications in high precision gravity measurement.

Desired Compensation Adaptive Robust Control of an Active Vibration Isolation System

“…Vibration isolation system is widely used in industrial equipment [1,2], building structure [3,4], and commercial vehicles [5][6][7], to protect the isolating object, such as human and structure, from being damaged by vibration with certain frequency regions. Especially in recent years, with the rapid development of nanoprecision technology, ultraprecision positioning devices, nanolevel measuring instruments, which are extensively used in medical research, biotechnology, semiconductor manufacturing, and space exploring, are demanding an increasingly need for high-performance vibration isolation system [8][9][10][11][12][13][14]. According to the source, vibration can be divided into two categories, the ground vibration which is caused by geodetic pulsation, wind blowing, automobile moving, people walking, and so forth, transferred via the suspension of the system, and the load vibration which is caused by inertial force from a moving load or other disturbance directly acted on the isolation system [15].…”

“…For the system in(8), with the DCARC control law(13) and the parameter adaptation law(14), the following results hold (A) In general, all signals in system (8) are bounded.Furthermore, the positive definite function V s is defined as…”