Electro-Mechanical Impedance Measurements in Space Environment with Miniaturized Hardware

Ever growing number of space systems raises a question about their safety and longevity. Over time, the complex space environment influences structural materials and electronics affecting mission objectives and performance. In order to determine the effect of space environment on spacecraft's structural condition, material properties and structural interfaces need to be assessed in space. Hence, it is suggested that active non-destructive measurements are employed to provide structural health information to the spacecraft's operator. Electro-mechanical impedance method is a promising approach to SHM of space structures due to its use of small unobtrusive piezoelectric sensors and lightweight hardware. In laboratory settings, this method typically utilizes bulky and heavy instruments, but for mid-frequency bands, a small and lightweight impedance measurement circuit could be built. A miniaturized impedance measurement analyzer was designed and built for applications requiring very small hardware mass. The development was driven by the intention to utilize the miniaturized analyzer for SHM of space structures in orbit. The impedance analyzer was designed and built from off-the-shelf components to enable impedance measurements in lower kHz frequency band. It was used to measure the impedance of a payload structure resembling a fixed plate. The aim of this measurement was to demonstrate data acquisition and storage by the miniaturized impedance logger and to compare its performance to laboratory scale instruments. The paper further discusses the effect of space environment on structures, describes and validates an analytical model for a fixed-fixed rectangular plate and provides analysis of the potential influence of thermal variation and radiation in space on electro-mechanical impedance signature.