Delay-dependent stability and added damping of SDOF real-time dynamic hybrid testing |
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Authors: | Fudong Chi Jinting Wang Feng Jin |
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Institution: | State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China |
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Abstract: | It is well-recognized that a transfer system response delay that reduces the test stability inevitably exists in real-time
dynamic hybrid testing (RTDHT). This paper focuses on the delay-dependent stability and added damping of SDOF systems in RTDHT.
The exponential delay term is transferred into a rational fraction by the Padé approximation, and the delay-dependent stability
conditions and instability mechanism of SDOF RTDHT systems are investigated by the root locus technique. First, the stability
conditions are discussed separately for the cases of stiffness, mass, and damping experimental substructure. The use of root
locus plots shows that the added damping effect and instability mechanism for mass are different from those for stiffness.
For the stiffness experimental substructure case, the instability results from the inherent mode because of an obvious negative
damping effect of the delay. For the mass case, the delay introduces an equivalent positive damping into the inherent mode,
and instability occurs at an added high frequency mode. Then, the compound stability condition is investigated for a general
case and the results show that the mass ratio may have both upper and lower limits to remain stable. Finally, a high-emulational
virtual shaking table model is built to validate the stability conclusions. |
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Keywords: | real-time dynamic hybrid testing root locus analysis delay-dependent stability Padé approximation added damping |
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