Design Of Adaptive Band-Stop Filter On Nano Movement Stage

With the constant development of high precision technology today,all kinds of precise instruments are widely used in all walks of life.And the key of realizing accurate control to these precise instruments is Nano Positioning and Scanning technique.Nano Positioning and Scanning technique often rely on Nano Movement Stage.But for Nano Stage,it will inevitably generate noise in the practical process,and affect the accuracy of movement.The noise from stage is more than one,and it can be divided into external noise and mechanical noise according to different sources.External noise could be filtered through low-pass filter,but for the mechanical noise,the process is not so easy to deal with.For Nano Movement Stage,the flexure guided mechanism is elastic,so the stage has a natural frequency.When signal frequency of external input close to the natural frequency,it will produce resonance and bring mechanical noise.At the same time,the change of load or flexure guided mechanism or mechanical structure in the test,will cause the natural frequency changing,so the resonance frequency is different.In order to solve this problem,the adaptive band-stop filter was designed for filtering resonance noise.The necessary parameters of filter were gotten adaptively by analyzing the spectrum of step response on Nano Stage.The design index of filter could be adaptively changed according to the variety of resonance frequency.This method avoid the tedious test processes which need to receive a fixed value as a try in advance and then debug design index continuously when design is using the traditional filter.It can shorten the work time,improve the efficiency,and get the desired band-stop filter quickly.According to the feature that Nano Movement Stage is using FPGA as a controller,this paper does research into the word length which has effect on IIR digital filter,and analysis the stability problem after quantization,and provide the method of coefficient quantization and truncation quantization.The shifting and adding operations are used to realize multiplier functions on IIR band-stop filter.This method optimizes the configuration of IIR system,reducing the total amount of computation,realizing fast operation,avoiding the problem that the multiplier IP core will be insufficient when the IIR filter order number is too high.MATLAB and ModelSim were used to demonstrate that adaptive IIR band-stop filter is able to effectively filter resonance noise on Nano Movement Stage,and ensure the stage movement accuracy.The proposed of adaptive band-stop filter,has a certain reference value on the filter design of the similar system and has good practicability.