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THE SHAKER PARAMETERS ESTIMATION, A FIRST STEP TO VIRTUAL SHAKER TESTING
Last modified: 2018-01-16
Abstract
In some cases, the increase in computing resources makes simulation methods more affordable. The increase in processing speed also allows real time analysis or even more rapid tests analysis offering a real tool for test prediction and design process optimization.
Vibration tests are no exception to this trend. The so called ‘Virtual Vibration Testing’ offers solution among others to study the influence of specific loads, to better anticipate the boundary conditions between the exciter and the structure under test, to study the influence of small changes in the structure under test, etc.
A physical vibration test can mainly be described by a closed-loop controlled excitation delivered by a shaker and introduced in the structure under test. The virtual vibration test will be nothing more than the complete modeling of this test loop (Fig. 1 left).
The subject of this article is to present a virtual shaker testing approach with a main focus on the shaker model characterization. Once the model is obtained, a state-space representation of the shaker system will be established.
The classical way of modeling a shaker is to consider the shaker as a simple mechanical structure augmented by an electrical circuit that makes the shaker move.
The shaker is modeled as a two or three degrees of freedom lumped parameters model while the electric circuit takes the coil impedance and the dynamic back-electromagnetic force into account.
The establishment of the equations (Fig. 1 right) of this model, describing the dynamics of the shaker, is presented in this article and is strongly related to the internal physical quantities of the shaker. Those quantities will be reduced into global parameters which will be estimated through experiments.
It is clear that without knowledge of those parameters, any model established would be perfectly useless.
A model of a small shaker will be established as the equations governing its behavior. The global parameters representing the internal functioning of the shaker will be identified and theoretical methods will be designed in order to characterize them.
Different experimental methods will be carried out in order to design an easy and practical method for the identification of the shaker parameters leading to a fully functional shaker method.
An experimental modal analysis will also be carried out to extract the modal parameters of the shaker and to combine them with the electrical measurements.
A last experimental validation of the model will be carried out and conclusions will be drawn.
Vibration tests are no exception to this trend. The so called ‘Virtual Vibration Testing’ offers solution among others to study the influence of specific loads, to better anticipate the boundary conditions between the exciter and the structure under test, to study the influence of small changes in the structure under test, etc.
A physical vibration test can mainly be described by a closed-loop controlled excitation delivered by a shaker and introduced in the structure under test. The virtual vibration test will be nothing more than the complete modeling of this test loop (Fig. 1 left).
The subject of this article is to present a virtual shaker testing approach with a main focus on the shaker model characterization. Once the model is obtained, a state-space representation of the shaker system will be established.
The classical way of modeling a shaker is to consider the shaker as a simple mechanical structure augmented by an electrical circuit that makes the shaker move.
The shaker is modeled as a two or three degrees of freedom lumped parameters model while the electric circuit takes the coil impedance and the dynamic back-electromagnetic force into account.
The establishment of the equations (Fig. 1 right) of this model, describing the dynamics of the shaker, is presented in this article and is strongly related to the internal physical quantities of the shaker. Those quantities will be reduced into global parameters which will be estimated through experiments.
It is clear that without knowledge of those parameters, any model established would be perfectly useless.
A model of a small shaker will be established as the equations governing its behavior. The global parameters representing the internal functioning of the shaker will be identified and theoretical methods will be designed in order to characterize them.
Different experimental methods will be carried out in order to design an easy and practical method for the identification of the shaker parameters leading to a fully functional shaker method.
An experimental modal analysis will also be carried out to extract the modal parameters of the shaker and to combine them with the electrical measurements.
A last experimental validation of the model will be carried out and conclusions will be drawn.