Dynamic response reconstruction using passive components
Doktorsavhandling, 2012

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.

substructuring

controllability

experimental methods

model calibration

passive control

response reconstruction

model updating

drive signal identification

Time Waveform Replication

EC, Hörsalsvägen 11, Chalmers
Opponent: Assistant Professor Matthew Allen, Department of Mechanical Engineering, University of Wisconsin-Madison, Wisconsin, USA

Författare

Anders Johansson

Dynamik

Increased Controllability in Component Testing using Structural Modifications

23rd International Conference on Noise and Vibration Engineering 2008, ISMA 2008; Leuven; Belgium; 15 September 2008 through 17 September 2008,; (2008)p. 999-1007

Paper i proceeding

Comparison of Several Error Metrics for FE Model Updating

Proceedings of the 25th International Modal Analysis Conference (IMAC-XXV), February 19-22, Orlando, Florida, USA,,; (2007)

Konferensbidrag (offentliggjort, men ej förlagsutgivet)

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

Proceedings, International Conference on Noise and Vibration Engineering, ISMA2012; International Conference on Uncertainty in Structural Dynamics, USD2012. Editors : P. Sas, D. Moens, S. Jonckheere. KU Leuven (Belgium), 17 - 19 September 2012,; (2012)p. 2367-2381

Paper i proceeding

Vid vissa typer av dynamiska prov, exempelvis utmattningsprov, eftersträvas att i möjligaste mån reproducera en komponents mekaniska miljö under ordnade former i laboratorie. För att denna typ av prov ska ge meningsfulla resultat krävs att överensstämmelsen mellan struktursvar från fältundersökningar och dito från laboratoriet är god. För att kunna återskapa en given tidshistorik krävs dock generellt att uppsättningen lastvägar in i systemet renderar ett styrbart system. Om så inte är fallet kan högre laster och stora avvikelser från fältundersökningen i struktursvaret uppkomma. En metod för att undvika detta har utvecklats. Eftersom målet vid laboratorieprov är att återskapa en specifik uppmätt signal som representerar komponentens mekaniska miljö strävas här efter att modifiera systemet på ett sådant sätt att avvikelsen från fältundersökningarna minimeras.

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. In most situations, standard control algorithms will ensure a test output which is close to the reference signal; however, if there are vibrational modes 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. 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. In introducing passive control components, this thesis presents such an approach.

Ämneskategorier

Maskinteknik

Beräkningsmatematik

Fundament

Grundläggande vetenskaper

ISBN

978-91-7385-681-2

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3362

EC, Hörsalsvägen 11, Chalmers

Opponent: Assistant Professor Matthew Allen, Department of Mechanical Engineering, University of Wisconsin-Madison, Wisconsin, USA

Mer information

Skapat

2017-10-07