Low-frequency vibration is a harmful factor that affects the accuracy of micro/nano-measuring machines. Low-frequency vibration cannot be completely eliminated by passive control methods, such as the use of air-floating platforms. Therefore, low-frequency vibrations must be measured before being actively suppressed. In this study, the design of a low-cost high-sensitivity optical accelerometer is proposed. This optical accelerometer mainly comprises three components: a seismic mass, a leaf spring, and a sensing component based on a four-quadrant photodetector (QPD). When a vibration is detected, the seismic mass moves up and down due to the effect of inertia, and the leaf spring exhibits a corresponding elastic deformation, which is amplified by using an optical lever and measured by the QPD. Then, the acceleration can be calculated. The resonant frequencies and elastic coefficients of various seismic structures are simulated to attain the optimal detection of low-frequency, low-amplitude vibration. The accelerometer is calibrated using a homemade vibration calibration system, and the calibration experimental results demonstrate that the sensitivity of the optical accelerometer is 1.74 V (m·s−2)−1, the measurement range of the accelerometer is 0.003–7.29 m·s−2, and the operating frequencies range of 0.4–12 Hz. The standard deviation from ten measurements is under 7.9 × 10−4 m·s−2. The efficacy of the optical accelerometer in measuring low-frequency, low-amplitude dynamic responses is verified.
Low-frequency vibration is one of the harmful factors that affect the accuracy of micro-/nano-measuring machines because its amplitude is significantly small and it is very difficult to avoid. In this paper, a low-cost and high-precision vibration generator was developed to calibrate an optical accelerometer, which is self-designed to detect low-frequency vibration. A piezoelectric actuator is used as vibration exciter, a leaf spring made of beryllium copper is used as an elastic component, and a high-resolution, low-thermal-drift eddy current sensor is applied to investigate the vibrator’s performance. Experimental results demonstrate that the vibration generator can achieve steady output displacement with frequency range from 0.6 Hz to 50 Hz, an analytical displacement resolution of 3.1 nm and an acceleration range from 3.72 mm s−2 to 1935.41 mm s−2 with a relative standard deviation less than 1.79%. The effectiveness of the high-precision and low-cost vibration generator was verified by calibrating our optical accelerometer.
A new micro accelerometer is proposed to measure and reduce low-frequency vibrations actively. It is mainly composed of a seismic mass, a leaf spring, and a focus probe modified from a digital versatile disc (DVD) pickup head. When a vibration occurs, the leaf spring will exhibit an elastic deformation; the seismic mass will move up and down due to the effect of inertia, whose displacement can be detected by the focus probe. Therefore, the measured acceleration can be obtained. The accelerometer was designed, and its proper parameters were obtained. The accelerometer was calibrated and tested using a high-precision vibration generator. The experimental results demonstrate that the proposed accelerometer has a sensitivity of 10.8 V/g, a resolution of 3.0 × 10 -4 g, and a working frequency range of 1-10 Hz. Also, the uncertainty of the accelerometer was analyzed in detail and an evaluation result of 7.0 × 10 -4 g (K = 2) was obtained. It can be used to detect the low-frequency microvibrations in high-precision measurement and machining fields.
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