❱ ❱ Modern speakers have the power and

quality to be able to provide an alternative to reverberant room testing

❱ ❱ Thales Alenia Space is working in partnership with Siemens PLM on alternative acoustic testing methods for satellite components

test and this difference needs to be accounted for in order to produce realistic test conditions, something Thales Alenia Space and Siemens engineers are engaged in.

SIMCENTER PRODUCTS At the heart of the work being done at Thales Alenia Space is the Siemens Simcenter suite comprising SCADAS hardware and Testlab software. The SCADAS hardware is both an output device that can provide signals for excitation and an input data acquisition (DAQ) device for taking sensor signals for measuring the response of the device under test. According to Massa, the Testlab software can handle the full flow of the test operation from setup through to DAQ as well as the visualisation of vibration profiles. “Having such flexibility within the software provides a powerful ability to perform not only analysis, but in-depth investigations,” he says.

SATELLITE TESTING At Thales Alenia Space, the acoustic test system uses SCADAS

hardware fitted with a multiple inputs multiple outputs (MIMO) controller and is combined with Simcenter Testlab. The objective is to reproduce the acoustic environment in the fairing of a satellite launcher. The test setup is designed to generate the high acoustic levels that excite the specimen during takeoff. The setup is comprised of 96 loudspeakers, stacked in 12 columns and adequately positioned in a circular configuration, and 96 amplifiers that deliver the required high power of 4x5 kilowatts (kW). The specimen being tested is placed at the centre of the five-meter cylinder of loudspeaker columns. The challenge is to reproduce a uniform diffuse acoustic field around the specimen and make sure that it is equivalent to that of an acoustic reverberant room. 16 microphones positioned around the specimen analyse the response and correct the signal input where necessary. The corrected values are reinserted in the loudspeakers in order to create a homogenous acoustic field. Using this MIMO closed-loop algorithm, the output matches

the reference profile, allowing the successful qualification of the reflector shell of an antenna subsystem as a demonstrator. n

Climatic & Vibration Testing 2018 Vol 1 No. 2 /// 3

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