By Christopher C. Fuller, S. J. Elliott, P. A. Nelson
This booklet is a significant other textual content to energetic keep an eye on of Sound via P.A. Nelson and S.J. Elliott, additionally released through educational Press.
It summarizes the foundations underlying lively vibration regulate and its sensible purposes via combining fabric from vibrations, mechanics, sign processing, acoustics, and regulate conception. The emphasis of the e-book is at the lively keep watch over of waves in constructions, the energetic isolation of vibrations, using allotted pressure actuators and sensors, and the lively keep watch over of structurally radiated sound. The feedforward keep watch over of deterministic disturbances, the energetic regulate of structural waves and the lively isolation of vibrations are lined intimately, in addition to the extra traditional paintings on modal suggestions. the rules of the transducers used as actuateors and sensors for such regulate recommendations also are given an in-depth description.
The reader will locate rather attention-grabbing the 2 chapters at the energetic keep watch over of sound radiation from buildings: energetic structural acoustic regulate. the cause of controlling excessive frequency vibration is usually to avoid sound radiation, and the rules and useful software of such options are awarded the following for either plates and cylinders. the amount is written in textbook kind and is geared toward scholars, working towards engineers, and researchers.
* Combines fabric from vibrations, sign processing, mechanics, and controls
* Summarizes new examine within the box
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Extra info for Active Control of Vibration
It is also of interest to evaluate the power carried by the beam for this form of excitation. Time-averaged power can be evaluated using the relationship in which instantaneous power is integrated over a period of motion. 6) where we use the previously stated convention that the actual, observed motion corresponds to the real part of the complex motion and T is a period of harmonic motion. 7) where (*) denotes complex conjugate and () denotes differentiation with respect to time. Using the above relations, the power in the beam for longitudinal motion is given by rI, = 1 2pc,S IF 12.
However, when the excitation frequency is such that ki= kn then the free wavenumber (or wavelength) also corresponds to the natural eigenvalue of the free system and the free waves reflect from the beam terminations INTRODUCTION TO WAVES IN STRUCTURES 43 with constructive interference and reinforce the beam motion. The net result is a large response associated with the resulting resonance. Behaviour such as this will be shown later to be critical to the performance of active vibration control systems in terms of stability, power requirements and performance.
3). In this case the moment of inertia and the density of the beam are normalised to a unit width of beam. Thus a modified moment of inertia, I ' = h3/12 and density p'= p/b are used in the previous relationships. 9) is also used. 12) where the external load p(x) now has units of force per unit area or pressure. 13) Eeff/' Flexural response of an infinite thin beam to an oscillating point force The flexural response of a semi-infinite or infinite beam to an oscillating point force is of interest and important to many of the analyses presented in later chapters.