Development Of Low Frequency Accelerometer And Evaluation Of Uncertainty

Low-frequency vibration has a destructive impact on high-precision machining,measurement and control,which cannot be effectively reduced by passive isolation.It is necessary for active isolation to measure low-frequency micro-vibration with high-precision.Therefore,a low-frequency optical accelerometer was developed to solve the problem.The following works have been finished in this paper:1. A high precision displacement sensor was modified from DVD pickup head based on astigmatism principle.Voltage conversion circuits,operational amplifier circuit,and low-pass filter circuit were designed to match the displacement sensor.2. Vibration-sensitive structures of the accelerometer were analyzed and optimized.The expression of the natural frequency with respect to parameters was obtained through a mathematical model of cantilever.The appropriate material and structural parameters of the cantilever were determined.An optimization scheme of symmetrical vibration-sensing structure was proposed to address the shortcomings of cantilever,whose feasibility were verified by simulation.3. The two accelerometers were calibrated and tested separately using a homemade vibration generator as an exciter and a high-precision eddy current sensor as a reference.The experimental results demonstrate that the symmetrical accelerometer has better performance than the cantilever accelerometer.The symmetrical accelerometer has a frequency response range of 1-10 Hz,a sensitivity of 10.8 V/g,a resonance frequency of46.5 Hz,and a resolution of 2.6×10^-3g.The performance of the symmetrical accelerometer in measuring low frequency and low amplitude dynamic response was verified.4. The main error sources and uncertainty of the symmetrical accelerometer was analyzed in detail.The uncertainty components caused by the indication error,uncertainty evaluation result of 3.4×10^–4 g（k=2）was obtained.Methods and results for accelerometer uncertainty evaluation are provided.