Low-power Electronics for Distributed Impact Detection and Piezoelectric Sensor Applications

Automated impact detection and characterization on aircraft and spacecraft has been an elusive goal due to the transitory nature of the detectable high-frequency signals involved. Invocon, Inc. has been awarded a NASA Phase 2 Small Business Innovation Research (SBIR) program to develop self-contained, miniaturized, piezoelectric sensory nodes with extremely low-power trigger modes that are synchronized within a radio frequency network. Each node will continuously monitor an accelerometer, acoustic emission sensor, or PZT element for an impact event, such as a micro-meteor impact or the foam impact that caused the Columbia tragedy. When a programmable threshold is exceeded, a low-latency signal acquisition circuit will capture the event as a digital waveform for post-processing and impact characterization including amplitude and time-of-arrival analysis. The innovative signal conditioning circuit design is capable of operation in the micro-watt range on average while constantly maintaining the capability to acquire and process very high frequency acoustic signals. Such performance can potentially provide operating lifetimes of 5 years on a single AA battery, or unlimited operation from scavenged power sources. Additionally, the system will provide a general purpose hardware platform on which Integrated Structural Health Monitoring (ISHM) algorithms and sensing techniques can be implemented. The same basic system design, with configurable sample rates, sensor interfaces, actuation outputs, and local processing algorithms, could be used for active or passive damage detection, locating leaks from pressurized vehicles and habitats through the produced airborne and surface-borne ultrasonic energy, or detecting crack propagation or delamination in structures through Acoustic Emission (AE) techniques. By allowing the development, demonstration, and potentially deployment of these ISHM capabilities on miniaturized devices optimized for low-power and distributed operation, the goals of ISHM will be more effectively achieved for aircraft and spacecraft. This paper shall provide a general description of the triggering capabilities, data acquisition circuit design, overall system design, and potential applications.