The fluctuating lift of a helicopter rotor gives rise to undesirable vibration over a broad frequency range which in some cases may extend to as low as 3 Hz. Vibration isolation over this frequency range is very difficult to achieve with either a purely passive or an active vibration isolation system. A passive system will work well at high frequencies, but it will always have a low-frequency resonance where excitation will be amplified rather than reduced. An active system may work well at low frequencies, but it will have trouble meeting the frequency response requirements at high frequencies. The investigation of the feasibility of combining an active and a passive system was conducted to gain the advantages of both. The report shows that an active system may be used to control the resonant response of a passive system while preserving the isolation achieved at high frequencies. Isolation over a broad frequency range may be obtained by this means with only a small amplification of response at low frequencies. (Author).

The feasibility of using an active control in the landing gear system of an aircraft to reduce wing fatigue damage resulting from ground induced bibrations during taxiing is considered. The characteristics of three vehicle models are discussed: a single landing gear system, a tricycle landing gear system and a system of five landing gears. Mathematical expressions for the runway inputs to each vehicle model are obtained in the form of random inputs represented by Gauss-Markov processes. The model for a linear hydraulic actuator which is used as the active control element in the landing gear system is presented. (Author).

A guide to the application of viscoelastic damping materials to control vibration and noise of structures, machinery, and vehicles Active and Passive Vibration Damping is a practical guide to the application of passive as well as actively treated viscoelastic damping materials to control vibration and noise of structures, machinery and vehicles. The author — a noted expert on the topic — presents the basic principles and reviews the potential applications of passive and active vibration damping technologies. The text presents a combination of the associated physical fundamentals, governing theories and the optimal design strategies of various configurations of vibration damping treatments. The text presents the basics of various damping effective treatments such as constrained layers, shunted piezoelectric treatments, electromagnetic and shape memory fibers. Classical and new models are included as well as aspects of viscoelastic materials models that are analyzed from the experimental characterization of the material coefficients as well as their modeling. The use of smart materials to augment the vibration damping of passive treatments is pursued in depth throughout the book. This vital guide: Contains numerical examples that reinforce the understanding of the theories presented Offers an authoritative text from an internationally recognized authority and pioneer on the subject Presents, in one volume, comprehensive coverage of the topic that is not available elsewhere Presents a mix of the associated physical fundamentals, governing theories and optimal design strategies of various configurations of vibration damping treatments Written for researchers in vibration damping and research, engineers in structural dynamics and practicing engineers, Active and Passive Vibration Damping offers a hands-on resource for applying passive as well as actively treated viscoelastic damping materials to control vibration and noise of structures, machinery and vehicles.

Integrating active control of both sound and vibration, this comprehensive two-volume set combines coverage of fundamental principles with the most recent theoretical and practical developments. The authors explain how to design and implement successful active control systems in practice and detail the pitfalls one must avoid to ensure a reliable and stable system. Extensively revised, updated, and expanded throughout, the second edition reflects the advances that have been made in algorithms, DSP hardware, and applications since the publication of the first edition.