This article describes the design of a vibration isolation system for AFM(Atomic Force Microscope) to reduce the external mechanical oscillation down to a subatomic scale. The AFM senses forces between the tip and the sample. In order to measure the sample with orders of sub-nanometer resolution, there are many difficult problems such as floor vibration of building, acoustic noise, thermal drift, and hysteresis of piezo-actuator. Especially the reduction of floor vibration effecting to AFM is required to this ultra-precision system firstly. Because no distance change between tip and sample is the most important thing to AFM.
Especially this article shows different system composition and design method compared with the existing isolation system. Also eddy current damping is studied in comparing theoretical modeling to experimental result.
The vibration isolator constitutes of two metal plate suspended by coil spring and eddy current damper. It is designed symmetrically, so it can separate lateral mode and vertical mode. Also in order to reduce the leakage of magnetic flux greatly new concept of design is described calls 'closed loop eddy current damper'. And isolator is constructed by optimal design scheme. The object function is isolator's damped natural frequency and the reverse of slope rate at high frequencies. Therefore it is used by a multi-objective scheme. The experimental results of the isolation performance are well explained by the experiment. Thereby the progressive characteristics of vibration isolator with eddy current damping are clarified.
Damping force is based on the interaction of eddy currents and a magnetic field usually induced in a moving part. Recently eddy current damping is used in many areas. Especially it is powerful to this AFM vibration isolator which has very low vibration amplitude. Because it has no friction and coincides modeling with experimental results well. Also it has good performance. But the eddy current modeling is maintained at the qualitative level only. Therefore this article will describe more precise analysis. And modeling coinsides with experimental result well.
