Vibration suppression

In a design one has to identify the mode(s) to suppress. It usually requires a special type of finite element analysis (FEA), called modal analysis. At CSA detailed FE models use MSC.Nastran (MSC.Software, Santa Ana, CA., USA), running on dual processor HP/Linux machines. Dynamic models typically require less detail than static stress models in order to accurately capture the modal shapes. FE results show the vibrations as strain energy identifying regions of high strain energy shows where vibration suppression methods should be applied. 

Restriction of achievable feed bandwidth and performance capability of machines High stiffness and damping with low mass required Active vibration suppression by semi-active and active ancillary systems (e.g., adaptive mass damper, adaptive friction damper)... 

Vibration, Fig. 9 Mirror surface machining after suppressing undesirable vibration (a) Diamond cutting with vibration-suppressed machining center, (b) Aluminum alloy machined by ordinary cutting, (c) Hardened die steel machined by elliptical vibration cutting (Shamoto et al. 2005)... 

SELF-POWERED MEDICAL DEVICES FOR VIBRATION SUPPRESSION... 

Piezoelectricity, energy harvesting, vibration suppression, piezoelectric fibre composites, wearable... 

Figure 2 Vibration suppression and energy harvesting circuit block diagram...

ABSTRACT Smart structures usually incorporate some control schemes that allow them to react against disturbances. In mechanics we have in mind suppression of mechanical vibrations with possible applications on noise and vibration isolation. A model problem of a smart beam with embedded piezoelectric sensors and actuators is used in this paper. Vibration suppression is realized by using active control. Classical mathematical control usually gives good results for linear feedback laws under given assumptions. The design of nonlinear controllers based on fuzzy inference rules is proposed and tested in this chapter. 

The objective in this study is to determine the vector of active control forces u t) snbjected to some performance criteria and satisfying the dynamical equations of the structure, such that to reduce in an optimal way the external excitations and to meet the above mentioned requirements. The investigations may be implemented in the time domain as well as in the frequency domain. The problem for vibration suppression is solved by both LQR and H2, Hjnf optimal performance criteria. These methods actually design the controlled system and do not take into account the external influence (e.g. the loading). The LQR method is only outlined in this paper. Technical details and results of the other control methods can be found in previons pnblications (Marinova et al. 2005, Stavronlakis et al. 2005, 2007). 

Stavroulakis, G.E., Eoutsitzi, G., Hadjigeorgiou, V., Marinova, D.G. Baniotopoulos, C.C. 2005. Design and Robust Optimal Control of Smart Beams with Application on Vibrations Suppression, Advances in Engineering Software, 36, 806-813. 

In this study, adaptive control algorithms have been utilized for designing active controllers for smart structure test articles. Adaptive control schemes require only a limited a priori knowledge about the system in order to be controlled. The availability of limited control force and inherent deadband and saturation effects of shape memory actuators are incorporated in the selection of the reference model. The vibration suppression properties of smart structures were successfully demonstrated by implementing the conventional model reference adaptive controllers on the smart structure test articles. The controller parameters converged to steady state values within 8 s for both direct and indirect MRACs. 

Davis, L. Hyland, D. Yen, G. and Das, A. Adaptive neural control for space structure vibration suppression. Smart Mater. Struct., 8(1999), pp. 753-766... 

Meyer, J.L. Harrington, W.B. Agrawal, B.N. and Song, G. Vibration suppression of a spacecraft flexible appendage using smart material. Smart Mater. Struct., 7 (1998), pp. 95-104... 

Wang, J. F., Lin, C. C., Chen, B. L. (2003). Vibration suppression for high speed railway bridges using tuned mass dampers. International Journal of Solids and Structures, 40(2), 465-491. doi 10.1016/S0020-7683(02)00589-9... 

Ali, S. F, Padhi, R. (2009). Active vibration suppression ofnonlinear beams using optimal dynamic inversion. Journal of Systems and Control Engineering, 223(5), 657-672. 

It should be noted that many of the issues can be dealt with an improved design or stmctural modifications. This is the case, for example, for flutter- and vortex-induced vibration suppressions on bridge deck, obtained by means of section modifications or aerodynamic countermeasures (e.g., deflectors, fairings, and flaps). Similarly, an appropriate designed cable cross section and surface can minimize cable vibration. 

Another aspect is the integration of Energy Harvesting (EH) methods with vibration suppression and control devices, for supplying power to autonomous sensors for SHM applications or for self-powered damper systems. Applications are expected using electromagnetic dampers (Shen and Zhu 2014) and piezoelectric or other materials once issues related to fatigue and real-life stresses are resolved. 

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