Linear Control Analysis & Review for Systema -- Utilization of Complex Thermo-Elastic Transfer Functions

Date

7/10/2022

Journal Title

Journal ISSN

Volume Title

Publisher

51st International Conference on Environmental Systems

Abstract

Due to the extremely demanding thermal stability environment of high precision optical instruments, thermal and thermo-elastic analyses are focusing on the effect of small disturbances on a nominal operational state. Performance requirements for some of these missions are formulated in the frequency domain and have to be evaluated within the frequency measurement bandwidth (MBW). In order to reduce computational effort and to improve numerical accuracy, the analysis is directly performed in the frequency domain which is preferable to the alternative of running multiple transient thermal analyses in the time domain and subsequent Fourier transformation. In previous papers (of the authors) such a methodology has been discussed in detail. It a) transfers the non-linear thermal network into a standard linear control system for one specific steady state point, b) subsequently transfers this system into the frequency domain via the Laplace transform, and c) calculates complex thermal transfer functions in the frequency domain. The associated S/W is Python based, and is part of the AIRBUS internal tool LCARS (Linear Control Analysis & Review for Systema). Expanding the methodology, the paper will discuss the derivation of complex thermo-elastic transfer functions, based on previously derived complex thermal transfer functions (reference) and the standard thermo-elastic distortion (TED) macro-node approach (reference). Further inputs to evaluate the margins with respect to thermo-elastic performance requirements are thermal noise models established for S/C external and internal noise sources. This application of the methodology is discussed exemplary for the ESA cornerstone mission LISA. The performance of a thermally compensated structure of the LISA instrument is analysed, detailing the influence of phase shifts and of amplitude attenuations in such a structure. Results of sensitivity analyses will be discussed, which allow to evaluate the capability of such a structural concept, to improve the TED performance.

Description

Erik Hailer, Airbus Defence and Space, DE
Johannes Burkhardt, Airbus Defence and Space, DE
Martin Altenburg, Airbus Defence and Space, DE
ICES207: Thermal and Environmental Control Engineering Analysis and Software
The 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.

Keywords

Linear Control, Frequency Domain, LCARS, Thermo-elastic, Transfer Function, TED

Citation