Study on piezoelectric actuator with sensor

提出了一种利用40 kHz超声波在空气中测量微米量级位移的新方法，并对其进行了实验评价。反射器的位移是由发射和接收的超声波信号之间的相位差φ通过反射法使用单个换能器测量的。针对超声波千分之一波长以下的位移检测问题，提出了一种测量发射信号与接收信号之间的相位差φ的新方法。该方法引入了N个参考信号。参考信号被锁定在发射信号中，以恒定的相位差θ_i(i=0，1，2，...，N)在0到2π的范围内。通过相位检测获得来自换能器的接收信号与参考信号之间的相位差ψ_i(i=0，1，2，…，N)。利用最小二乘法估计出的位相差φ与位相差ψ_i相结合，计算出位移。基于本方法的位移测量是利用40 kHz的超声波和压电陶瓷换能器在空气中进行的。测量了反射镜1μm步长的位移，通过机械平移工作台可实现10 nm量级的平移。反射镜的位移与被测位移之间呈良好的线性关系。位移测量与参考信号(N=12)的分辨率为40 nm。在没有mhz换能器的情况下，我们的方法在40 khz的空气耦合超声换能器的位移测量中具有1μm的分辨率。

A measurement method for displacement of micrometer-order using ultrasonic wave of 40kHz in air is newly proposed and evaluated experimentally. The displacement of an reflector is measured from the phase difference φ between the transmitting and received ultrasonic wave signals using a single transducer by reflection method. For detection of displacement under a thousandth of wavelength ~of ultrasonic wave, a novel measurement method of the phase difference φ between the transmitting and received signals is described. The reference signals, of which the number is N, are introduced in this method. The reference signals are locked in the transmitting signal to constant phase differences θ_i(i=0,1,2,...,N) within the range of 0 to 2π. The phase differences ψ_i(i=0,1,2,...,N) between the received signal from the transducer and the reference signals are obtained by phase detection. The displacement is calculated from the phase difference φ which is estimated by the least squares method with the phase differences ψ_i. The displacement measurements based on our method were carried out using ultrasonic wave of 40kHz in air with piezoelectric ceramic transducer. The displacement of 1μm steps of the reflector, which can be translated with 10nm-order accuracy by mechanical translation stage, is measured. The relation ship between the displacement of the reflector and the measured displacement shows good linearity. The displacement measurements have resolution 40nm with the reference signals(N=12). Without a transducer in MHz range, our method having the resolution of 1μm on the displacement measurement with air-coupled ultrasonic transducer of 40kHz is useful