Investigation of Interface Impedance in SISO and MIMO Shaker Testing, Allen et al., SCLV 2021
Shakers are routinely used to reconstruct the environments on systems ranging from small, inexpensive components to multi-billion dollar spacecraft. The primary goal of these tests is to reproduce the response, and hence the stresses and failures, that the component would experience during flight. From this standpoint it may prove beneficial if the impedance at the interface to the shaker or shakers matches that of the desired environment. On the other hand, conventional wisdom dictates that shaker tests are more likely to be successful if the fixtures connecting the component to the shaker are as rigid as possible, ideally driving the fixed-base resonances of the system out of the bandwidth of interest. Traditionally, environments are reproduced on large shakers that focus on one axis at a time, but recently there has been increasing interest in multi-axis shaker systems or on using several smaller shakers simultaneously with stingers between the shaker and the component. This work presents the results of a series of tests that were performed recently to explore these issues. The dynamic environment on a small component was measured during a flight on a sounding rocket, and various strategies were explored to reproduce that environment on the component, including a single-axis test, and a multi-input-multi-output test using six shakers with various interface fixtures. The results help to elucidate some of the challenges that may arise and the extent to which it may be beneficial to match the impedance in the flight environment.
Presented at the 2021 Spacecraft and Launch Vehicle Dynamic Environments Workshop (virtual) hosted by Aerospace Corporation
Authors: Matt Allen, Matt Tuman, Washington de Lima & Eric Dodgen