Study on a micro-knife and its vibration signal acquisition system

A micro-knife which is driven by two bulk PZT-4 ceramic plates works in an ultrasonic vibration mode. This length and width of the selected micro-knife are 17 mm and 10 mm respectively. We can estimate resonant frequencies in the longitudinal direction and the transverse direction, which are 227 KHz and 452 KHz. By impedance measurement, the resonance and anti-resonance frequencies of PZT-4 plates are obtained. Then we can choose proper PZT-4 plates to drive the micro-knife and observe their vibration using high-power digital microscope and a CCD device on precision optical vibration isolation platform. It was found that if the shape of the micro-knife is linear symmetrical, there is no any displacement in transverse direction, while if the shape of the micro-knife is unsymmetrical, the displacement in transverse direction will occur besides the longitudinal direction, which is consistent with the theory. At last, we studied micro-knives vibration signal acquisition system based on digital signal processing (DSP) and phase locked loop (PLL). The circuit and software of the system were developed. The vibration voltage signal result was simulated. And we can lock the vibration voltage frequency. This method can provide an effective method for accurate measurement and control of the PZT-driven micro/nano devices.