Linear Control Analysis & Review for Systema (LCARS) � Utilization of Complex Thermal Transfer Functions

Date

7/12/2021

Journal Title

Journal ISSN

Volume Title

Publisher

50th International Conference on Environmental Systems

Abstract

Due to the extremely demanding thermal stability environment of high precision optical instruments, thermal analyses are focusing on the effect of small disturbances on a nominal operational state. Thermal performance requirements for some of these missions are formulated in the frequency domain and have to be evaluated within the frequency measurement bandwidth (MBW). The standard methods to verify the thermal requirements in the frequency domain are based on transient thermal analysis in the time domain and subsequent Fourier transformation. Depending on the thermal model size, this approach requires running extensive and time consuming transient thermal analysis. Due to the extremely stable thermal environment of these systems, an approach to linearize the thermal network around a steady state operating point is adequate.

LCARS is an AIRBUS internal tool that allows transferring the non-linear thermal network into a standard linear control system for one specific steady state point and subsequent transfer into the frequency domain via the Laplace transform. LCARS retrieves the information of the thermal network (temperature, coupling and capacity) from the �commercial� solver outputs (Systema or ESATAN) and generates a linear control system. Via different implemented methods, this system can then be analysed in the frequency domain. This approach avoids calculating multiple transient analyses and subsequent application of the Fourier transform, and is therefore a very time efficient and precise analysis tool.

The LCARS analysis tool has been extended during the last years to complex transfer functions calculating now not only the amplitude (gain), but as well the phase, which allows analysing phase shifts along the thermal path(s) from noise source(s) to sensitive equipment or I/Fs, and subsequently thermo-elastic distortion analyses in the frequency domain. The paper will recap the different analysis approaches and will focus on the derivation of the complex thermal transfer functions.

Description

Erik Hailer, Airbus Defence and Space GmbH
Johannes Burkhardt, Airbus Defence and Space GmbH
Martin Altenburg, Airbus Defence and Space GmbH
ICES207: Thermal and Environmental Control Engineering Analysis and Software
The 50th International Conference on Environmental Systems was held virtually on 12 July 2021 through 14 July 2021.

Keywords

Thermal Analysis, Frequency Measurement Bandwidth, Frequency Domain, Fourier Transformation, Laplace Transformation, Transfer Function

Citation