SENSORS: High-Fidelity, Broadband, MEMS Displacement Sensor Arrays for Intelligent Structural Health Monitoring*

We propose an Intelligent Structural Health Monitoring (ISHM) System based on a radical improvement in the accuracy and resolution of displacement (hence strain) measurement, fabricating a wide-band high-fidelity PZT-based sensor of micron size. To accomplish this we propose new methods of growing the conical sensor elements, and unique self-assembly techniques that avoid expensive off-site CMOS wafer fabrication. Custom low noise micro-circuitry will be developed in CMOS to match the high impedance/low capacitance piezo-sensing element, with the option of locating small (7 mm2) 12-bit A/D conversion at sensor node. The packaging and delivery system will be designed to optimize sensor capabilities and applicabilities. Integral to the development of the sensor itself, we will develop an interpretation scheme that utilizes the accurate waveforms output by our sensors to determine structural health based on the actual physics of damage and wave propagation. Our system facilitates the optimum use of many new materials. For example, the life cycle cost of high-value aerospace structures can be reduced significantly if continuous and autonomous condition-based maintenance systems are installed and integrated into the structure. According to estimates, over 25% of the life cycle cost of an aircraft, which includes pre-production, production and post-production costs, can be attributed to operation and support, involving inspection and maintenance of the airframe. This vision - a structure requesting service when needed - can only be accomplished with the development of our intelligent structural health monitoring system. Intellectual and societal contributions from this project include: >New method for growing single and poly-crystal PZT micro-cones >Novel methods for self-assembly of cone, backing mass, and CMOS >Orders of magnitude improvements in low-noise circuitry and micro A/D >New approach to sensor packaging and delivery (roll-of-tape) >Physics-based waveform interpretation - rational identification of damage >Rapid, cheap data acquisition allowing verification of constitutive models >Test bed for true interdisciplinary research (faculty and students) >Safer, more efficient structures of all kinds - airframes, buildings, cars, etc. >Integration of advanced sensor system into practical use *This project is not officially supported through CITRIS funds, but the faculty and topical affiliations are sufficiently strong that it is listed here for referral and convenience.