Study on piezoelectric actuator with sensor

提出了一种利用40kHz超声波在空气中测量微米级位移的新方法，并进行了实验验证。利用反射法，利用单个换能器发射和接收的超声波信号之间的相位差φ来测量反射器的位移。为检测千分之一波长~下的位移，提出了一种测量发射与接收信号相位差φ的新方法。该方法引入参考信号，参考信号的个数为N。参考信号在发射信号中被锁定到恒定相位差θ_i（i=0,1,2，…），N)，取值范围为0 ~ 2π。相位差ψ i（i=0,1,2，…），N)，从换能器接收到的信号与参考信号之间通过相位检测得到。位移由相位差φ计算，用最小二乘法估计相位差ψ i。利用压电陶瓷换能器，利用40kHz的超声波在空气中进行了位移测量。测量了反射镜的1μm步长位移，该位移通过机械平移台可平移至10nm级精度。反射器的位移与实测位移呈良好的线性关系。位移测量分辨率为40nm，参考信号（N=12）。在没有MHz范围换能器的情况下，我们的方法对40kHz空气耦合超声换能器的位移测量具有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