Experimental and Analytical Approaches in a Virtual Shaker Testing Simulation Environment for Numerical Prediction of a Spacecraft Vibration Test

Abstract

A spacecraft is exposed to a variety of extreme dynamical loads during launch. As a result, spacecraft are tested on ground in a vibration test campaign to ensure and verify the global integrity of the structure and to screen the flight hardware for workmanship errors since safety and security are top priorities. Additionally, the gathered experimental test data can be used to validate and correlate mathematical models. During these tests especially in fixed-base sinusoidal vibration testing of large spacecraft, the dynamical interaction between the test specimen, the vibration controller and test facility is a critical issue affecting the closed-loop vibration control performance, the quality of subsequent numerical model validations or even damaging the entire testing setup. In order to assess the occurrence of such issues and to minimise their influence by adapting control parameters, virtual shaker testing intends to numerically replicate the entire vibration test chain. To successfully predict the actual experimental conditions, validated and reliable models need to be developed, replicating the control strategy as well as the shaker and test specimen dynamic behaviour as accurately as possible. In practice, such models are usually not available or accessible to the test engineer or analyst. Therefore, this paper reviews the current status of the work combining experimental and physical methodologies to numerically predict a sine vibration test. Two approaches are presented: (1) a purely experimental data driven approach based on measured data only, e.g. from system self-check data and (2) a hybrid data driven approach considering numerical shaker facility and structural dynamic test specimen models. Subsequently, the corresponding sine control closed-loop simulation results are correlated to real physical test data and consequently their advantages and disadvantages are discussed.