Active health monitoring of an aircraft wing with an embedded piezoelectric sensor/actuator network: II. Wireless approaches

摘要

The objective of this study is to develop a wireless ultrasonic structural health monitoring (SHM) system for aircraft wing inspection. In part I of the study (Zhao et al 2007 Smart Mater. Struct. 16 1208-17), small, low cost and light weight piezoelectric (PZT) disc transducers were bonded to various parts of an aircraft wing for detection, localization and growth monitoring of defects. In this part, two approaches for wirelessly interrogating the sensor/actuator network were developed and tested. The first one utilizes a pair of reactive coupling monopoles to deliver 350 kHz RF tone-burst interrogation pulses directly to the PZT transducers for generating ultrasonic guided waves and to receive the response signals from the PZTs. It couples enough energy to and from the PZT transducers for the wing panel inspection, but the signal is quite noisy and the monopoles need to be in close proximity to each other for efficient coupling. In the second approach, a small local diagnostic device was developed that can be embedded into the wing and transmit the digital signals FM-modulated on a 915 MHz carrier. The device has an ultrasonic pulser that can generate 350 kHz, 70 V tone-burst signals, a multiplexed A/D board with a programmable gain amplifier for multi-channel data acquisition, a microprocessor for circuit control and data processing, and a wireless module for data transmission. Power to the electronics is delivered wirelessly at X-band with an antenna-rectifier (rectenna) array conformed to the aircraft body, eliminating the need for batteries and their replacement. It can effectively deliver at least 100 mW of DC power continuously from a transmitter at a range of 1 m. The wireless system was tested with the PZT sensor array on the wing panel and compared well with the wire connection case.