Low Frequency Band Expansion Technology For Absolute Speed Signals In Ultra-low Frequency Vibration Isolation

In recent years,due to the development of science and technology,the accuracy and stability of various instruments and equipment have been improved.The impact of various vibrations become more prominent and how to effectively isolate low frequency and ultra-low frequency vibration has become a hot and difficult research.Compared with the passive vibration isolation technology,active vibration isolation technology has a smaller vibration transmission rate and has a greater vibration isolation bandwidth,which have been widely used in precision testing and ultra-precision manufacturing equipment.Magnetic vibration velocity sensor is an important part of the active vibration isolation system.Due to the limitation of the environment,the sensor can't meet the requirements of small volume and low frequency signal detection at the same time.Therefore,it is of great practical value to choose a reasonable compensation scheme,a well-designed compensation circuit and a compensation software to meets the performance requirements without changing the mechanical structure of the sensor.In this paper,the performance requirements of the vibration isolation system are analyzed,and the working characteristics of all kinds of absolute vibration sensors are analyzed and compared.Finally,the key technical indexes and sensor models are determined.Based on the analysis of the structure and working principle of the magnetoelectric velocity sensor,the dynamic model of the sensor is established,the transfer function of the sensor is constructed,and the amplitude and frequency characteristics of the sensor are obtained,then the low frequency measurement of the sensor is analyzed according to the transfer function.Last proposed for the limitations of the sensor low-frequency expansion program,and finally to determine the use of zero-pole compensation method for low-frequency sensor expansion.Due to the need for more accurate transfer function,this paper also studied a variety of magnetic speed sensor test methods,such as DC excitation method,sinusoidal excitation signal method and vibration table method.The advantages and disadvantages of each method are analyzed.Combined with various factors,the DC excitation method is used to test the sensor parameters,and the hardware circuit and software are designed to obtain the accurate transfer function of the sensor.According to the measured transfer function and zero pole compensation method,the corresponding hardware and software are designed to complete the signal processing.The experimental results show that the relative error of the center frequency measurement of DC excitation method is 0.35% and the relative error of damping ratio is 0.92%.The test parameters are used for the zero pole compensation network,and the low frequency signal detection experiment is carried out to verify the low frequencyexpansion function of the extended circuit and software to the magnetoelectric speed sensor.The experimental results show that the core frequency of the sensor can be reduced from 4.8Hz to 0.28 Hz by hardware circuit and software method,and the aim of the sensor low band expansion can be realized.