Volume 9, Number 3 • May/June 2001

Smart Structures Monitor Spacecraft Health

Material degradation and contamination due to long-term exposure to the space environment is a serious hazard for space structures. These materials have many damage-detection mechanisms and failure prediction methodologies yet to mature. In addition, once placed in orbit, the structures are difficult to inspect.

Environmental factors degrade materials and structures through surface erosion, impacts due to micrometeorites, outgassing, launch, deployment and operational loads, vibration, and thermal cycling. These effects can severely reduce both the strength and stiffness of a composite material. In order to successfully use composite vehicles and platforms in space, provisions for monitoring structural degradation must be incorporated into the design of the structure—“smart” aerospace structures. The data obtained from this monitoring can be used to automatically modify the control algorithms of the structures in real-time.

Innovative Dynamics, Inc., (IDI) of Ithaca, New York, developed a technology for monitoring the structural health of spacecraft applications. The system, designed specifically for composite structures, uses an array of embedded piezoelectric elements and a broadband excitation source to excite modal structural frequencies. Specific flaws can be detected using pattern recognition techniques.

A smart structure is a structure instrumented with arrays of sensors, computers and actuators that monitor its load environment and structural integrity throughout its life and take corrective action when required.

According to Gail Hickman, vice president of research and development for Innovative Dynamics, “This technology would significantly boost the reliability, maintainability and performance of future aerospace structures. The sensor arrays will play the role of the nervous system, a computer architecture will play the role of the brain and actuators will play the role of muscles.”

This work was funded under an SBIR program sponsored by NASA’s Jet Propulsion Laboratory. The system consists of piezoelectric sensors integrated throughout the structure and a hierarchical computing architecture to process the sensor information and respond as damage is detected. The system works by mechanically exciting the structure with broadband energy and monitoring changes in the structural vibration response. Shape, amplitude and distortion of the vibration signals provide useful information concerning the location and severity of the damage. Pattern recognition techniques are used to analyze the vibration signature and assess the damage. The use of multiple sensors provides a means of locating the damage as well.

For more information, contact Gail Hickman of Innovative Dynamics, 607/257-0533, info@idiny.com. You can also visit IDI’s Web site at http://www.idiny.com. Please mention you read about it in Innovation.