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Smart Damping Materials using Shunt Control


D. Niederberger

Diss. ETH No. 16043

Vibration in modern structures like airplanes, satellites or cars can cause malfunctions, fatigue damages or radiate unwanted and loud noise. Since passive damping materials have reached their limits to damp vibration, new control designs with novel actuator systems have been proposed. These so called smart materials can control and suppress vibration in an efficient and intelligent way without causing much additional weight or cost.

In this thesis, the development and implementation of such novel smart materials to damp structural vibration is described. The proposed smart damping materials consist of piezoelectric transducers that are shunted to passive electronic circuits. These electronic shunt circuits are designed such that effective vibration suppression is achieved that is robust to variations within the structure. Additionally, some of the suggested smart damping materials do not require external power and are thus autonomous in operation.

The introduction of the first part thoroughly reviews several shunt circuits that have been proposed in the past. These shunt circuits are categorized into different groups and critically analyzed. We will see that most shunt circuits lose their damping performance with variations in the transducer capacitance and structural resonance frequencies.

In Part II, an online-tuned resonant shunt is introduced that automatically adapts itself for the optimal vibration suppression of one or several modes using a novel adaptation technique. It turns out that this new adaptation methodology tunes much faster than traditional methodologies and shows less miss-adjustment. Furthermore, implementation of the adaptation law is shown to be straight forward and realizable with a simple analog circuit.

Part III presents an autonomous shunt circuit that does not require external elec- trical power for operation. The proposed shunt circuit is based on a switching circuit. In the past, it was unclear how to switch these kinds of circuits in order to achieve optimal damping, because the system of interest is hybrid in nature. This work shows how to apply a hybrid system framework using a receding horizon optimal control methodology in order to obtain the optimal switching sequence. Additionally, a multi- parametric programming approach is presented that leads to the optimal switching law. Afterwards, the derived switching law is approximated and implemented with a simple analog circuit that does not need power for operation. Experiments demonstrate that this circuit achieves better vibration suppression than all other shunt circuits that do not need power for operation and have been proposed so far.

An investigation of different shunt damping applications is given in Part IV. First, the suitability of novel active fiber composites (AFCs) for shunt damping is investigated and discussed. Since the inherent capacitance of AFCs is rather low, AFCs are not particularly suitable for shunt damping. However, there are cases where their use is favorable. Afterwards, we describe how the idea of shunt damping can be extended to loudspeakers in order to damp acoustical noise in a duct system. It is demonstrated that the noise can be efficiently reduced without the need of an error sensor. This leads to many other interesting applications in the field of acoustics.

Finally, Part V concludes the main achievements of this thesis and future research directions are outlined.

Further Information


Type of Publication:

(03)Ph.D. Thesis

M. Morari

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% Autogenerated BibTeX entry
@PhDThesis { Xxx:2005:IFA_2210,
    author={D. Niederberger},
    title={{Smart Damping Materials using Shunt Control}},
    school={Swiss Federal Institute of Technology, Zurich},
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