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).

This book discusses efforts to control the low-frequency vibration transmission of typical power equipment and pipeline systems of ships, exploring the use of active and passive hybrid vibration isolation and adjustable dynamic vibration absorption technologies. It also proposes an adaptive feed-forward control strategy and studies a distributed feed-forward control hardware system. In addition, the book presents a three-way dynamic vibration absorption theory used to design a pipeline-system adjustable dynamic vibration absorber, which offers a number of advantages, such as compact structure, easy assembly and disassembly, low power consumption, excellent vibration control effect and wide frequency band adjustable ability, etc. This book is a valuable resource for researchers and engineers in the fields of noise and vibration control, active control systems, active vibration isolation and adaptive dynamic vibration absorption.

With progress in technology, the problem of protecting human-beings, ma chines and technological processes from !>Ources of vibration and impact has become of utmost importance. Traditional "classical" methods of pro tection, based upon utilising elastic passive and dissipative elements, turn out to be inefficient in many situations and can not completely satisfy the complex and often contradictory claims imposed on modern vibration protection systems which must provide high performance at minimum di mensions. For these reasons, active vibration protection systems, which are actually systems of automatic control with independent power sources, are widely used nowadays. Appearing and developing active systems require that traditional ap proaches to the analysis and synthesis of vibration protection systems must be revised. Firstly, there exists the necessity to re-state the problem of vi bration protection from mechanical actions as an equivalent problem in closed-loop control systems design, which is to be solved by the methods of control theory. Furthermore, it turns out that certain inherent proper ties of active systems must be taken into account for a proper design. In the majority of cases, the dynamic models of the objects to be protected and the bases to which these objects are to be attached must be revised. They are no longer considered as rigid bodies but elastic bodies with weak dissipation.

Online version: Technical papers portion of the SAE Digital Library references thousands of SAE Technical Papers covering the latest advances and research in all areas of mobility engineering including ground vehicle, aerospace, off-highway, and manufacturing technology. Sample coverage includes fuels and lubricants, emissions, electronics, brakes, restraint systems, noise, engines, materials, lighting, and more. Your SAE service includes detailed summaries, complete documents in PDF, plus document storage and maintenance

This major work is the first to treat the active control of both sound and vibration in a unified way. It outlines the fundamental concepts, explains how a reliable and stable system can be designed and implemented, and details the pitfalls . It covers sound in ducts, sound radiation, sound transmission into enclosures, structural vibration and isolation, electronic control system design, and sensors and actuators.