A Study of the Wireless and Short Distance Interrogation System for Surface Acoustic Wave Torque Sensing

• Main Authors: Wu-Cheng Chung, 張武正
• Other Authors: None
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/31426330755586347796

碩士 === 國立中正大學 === 光機電整合工程所 === 94 === In this thesis, we have proposed a novel system that will be used to measure the torque of a spindle shaft in wireless way. The principle of the torque sensor is a passive SAW(surface acoustic wave) sensor. We interrogate the passive SAW sensor using a ISM-Band wireless interrogation system which is suitable for the short distance coupling. The advantages of our proposed system include wireless detection, compactness, and lower cost. Because of the batteryless feature, the sensor can be used for a long time life. In this research, we utilize a commercialized MAX7032 Transceiver IC and 8051 module to build up the active interrogation system. Iimportant requirements of the developed interrogation system is the frequency step sweep function and analog demodulation in ISM band from 433.3~434.3 MHz. The frequency sweep range must be match with the frequency response of the part of one-port passive SAW sensor which is designed at a resonator frequency around 433.92 MHz. A external variable capacitor is added to the passive SAW sensor to simulate the situations when different torques are applied to the SAW sensor. The resonance frequency shift will be observed on the SAW according to the added capacitance values. By scanning the interrogation frequency, we received reflected signals with changed amplitude from the SAW sensor. We then applied a curve-fitting algorithm to estimate the center frequency change. The experimental results have shown that we can precisely estimate the central frequency with an error less than 20 kHz compared with the measurement results from a commercial network analyzer.