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Dynamic response reconstruction using passive components

Anders T Johansson (Institutionen för tillämpad mekanik, Dynamik)
Göteborg : Chalmers University of Technology, 2012. ISBN: 978-91-7385-681-2.- 115 s.

In many testing applications within the field of structural dynamics, such as noise and vibration harshness, rattle and squeak, or durability testing in the automotive and truck industries, large hydraulic or electromagnetic actuators are used to excite the tested structure. Such actuators are mounted in the laboratory in a fixed configuration referred to here as a test rig. A frequent method for calculating the input to such test rigs is to replicate a certain reference signal, for instance dynamic responses from driving tests, to ensure that the test case is physically motivated. Versions of the Time Waveform Replication (TWR) method are often used to this end, iteratively calculating an input sequence used to excite a system such that its response replicates a desired reference. The TWR algorithm essentially estimates the unknown input by pseudo-inversion of the frequency domain transfer function. In most situations, TWR will ensure a test output which is close to the reference signal; however, if there are eigenmodes of the test specimen in the desired frequency range of the test which are uncontrollable, it can be shown that the required input force and/or the error between test output and desired reference will be large. Such problems remain even when reference-contributing modes are but marginally controllable. In a test rig such as described above, this controllability shortcoming may be impossible to prevent in the usual manner, \emph{i.e.} through changing the input configuration. This can cause poor reference replication whereby the validity of the test may be put into question. For such specific cases, where the possibilities of changing the input configuration is slim and controllability is lacking, a different approach is required. This thesis presents such an approach. It introduces the concept of passive control to the problem of response reconstruction: By attaching a modifying component to the tested structure, designed specifically to improve response reconstruction, the controllability of the system can improve. Two methods for designing such passive components are described. The first uses a high-quality finite element model of the tested structure and parameterized passive component, performing synthetic TWR experiments to evaluate its rig control properties. The second uses instead an experimentally derived model of the tested structure, which is coupled to the analytical model of the passive component through an experimental/analytical substructuring technique.

Nyckelord: experimental methods, Time Waveform Replication, response reconstruction, drive signal identification, passive control, model calibration, model updating, substructuring, controllability

Denna post skapades 2012-04-24. Senast ändrad 2013-09-25.
CPL Pubid: 157009


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Institutioner (Chalmers)

Institutionen för tillämpad mekanik, Dynamik


Tillämpad matematik
Teknisk mekanik

Chalmers infrastruktur

Relaterade publikationer

Inkluderade delarbeten:

Comparison of Several Error Metrics for FE Model Updating

Increased Controllability in Component Testing using Structural Modifications

An experimental approach to improve controllability in test rigs using passive components


Datum: 2012-05-25
Tid: 13:00
Lokal: EC, Hörsalsvägen 11, Chalmers
Opponent: Assistant Professor Matthew Allen, Department of Mechanical Engineering, University of Wisconsin-Madison, Wisconsin, USA

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Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie 3362