Structural health monitoring using electro-mechanical impedance sensors

This paper reports recent achievements of novel structural health monitoring (SHM) techniques for damage diagnosis for critical members of civil, mechanical and aerospace structures using electro-mechanical impedance sensors. The basic concept of this technique is to use simultaneously both high-frequency structural excitations and responses employing piezoelectric sensors to monitor the local area of a structure for changes in structural impedance that would indicate imminent damage. In this paper, several principal software and hardware issues on these topics are described. A new impedance model is proposed that incorporates the effects of sensor and bonding defects for sensor self-diagnosis. Temperature effects-free impedance-based damage detection algorithm using effective frequency shifts based on cross-correlation coefficients is presented. In a sense of tailoring wireless sensing technology to the impedance methods, an active sensor node incorporating a miniaturized impedance sensing device, an on-board microcontroller, and a radio frequency (RF) telemetry is introduced. A data compression algorithm is embedded into the on-board chip of the active sensor node to enhance its local data processing-capability. Finally, this paper concludes with a discussion of further studies and future applications.