Vibrating machinery must be isolated from a supporting structure if the vibration is likely to cause fatigue of components or annoyance to people due to direct vibration exposure or from the noise radiated by the vibrating structure. Active vibration isolation can be applied in these situations to extend the low frequency performance of passive vibration isolators. In this thesis, theoretical and experimental investigations are described for a vibrating rigid body that is passively and actively isolated from a beam and a cylinder, respectively. The focus of the work is to investigate the vibrational power transmitted by translational forces and rotational moments into the support structure. For the investigation of the simply supported beam, a classical mathematical model is examined and finite element modelling is used to predict the power transmission into the beam when active vibration control is used. The results show that power transmission by moments is significant and cannot be ignored when the vibrational power transmission into the support structure is actively controlled. To control the power transmission by translational forces and rotational moments, a novel six axis active vibration isolator and a novel six axis force transducer were constructed to be used in the experimental investigations. Using vibrational power transmission as a cost function to be minimized in active control experiments presents unique problems because negative values of translational power transmission are possible when power transmission from rotational moments is ignored or when phase errors occur in the transducer outputs. Active control attempts which converge the cost function to a negative value of power transmission along a particular axis can result in overall vibration levels in the structure which are greater than without active control. To prevent the increase in vibration levels, minimization of the squared value of power transmission is investigated as a potential cost function. A method is described to combine force and velocity signals into a signal which is proportional to the vibrational power transmission and is suitable for use with an existing filtered-x Least Mean Squares controller, so that the squared vibrational power transmission can be minimized. Experimental trials were performed to actively minimize the power transmission into a simply supported beam from a vibrating rigid body using a single axis and a six axis active vibration isolator. The purpose of the experimental work was to confirm the theoretical findings and to find a practical method to measure power transmitted by rotational moments. The vibrational power transmission from a vibrating rigid body that is passively and actively isolated from a cylinder was also investigated. The theoretical model of the cylinder was similar to the beam model, although the dynamics of the cylinder makes the solution more complicated. Two experimental trials were conducted to verify the theoretical model and involved the use of the single axis and the six axis active vibration isolators, respectively. / Thesis (Ph.D.)--School of Mechanical Engineering, 1999.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Young S. Shin, Ilbae Ham. Includes bibliographical references (p. 49). Also available online.

This thesis considers the use of chaos concepts in investigating the dynamics of two discontinuously nonlinear mechanical systems having two degrees of freedom. The nonlinearity considered is in the form of a discontinuous stiffness effect, and can cause the systems to exhibit chaotic motion. The first system is a rotor system with a bearing clearance effect. The second is a nonlinear vibration absorber, comprising a conventional linear absorber and a linear snubber stiffness, which the auxiliary mass intermittently contacts. Numerical integration is used in solving the equations of motion for each system. Equivalent physical rigs are tested. Both the theoretical and experimental results are analysed using chaos techniques such as phase plane portraits, Poincaré maps, frequency spectra and bifurcation diagrams. Comparison made between the differently acquired results shows that fairly good correlation is obtained in both systems, for realistic values of damping. Periodic, quasiperiodic and chaotic responses are exhibited by both systems, for different combinations of system parameters, with the responses of the systems being extremely sensitive to changes in these parameters. Investigations of the rotor system concluded that quasi-periodic responses are only possible if there is some form of cross-coupling present. An effective discontinuously nonlinear absorber is developed, theoretically. A reduction in the amplitude of the second resonance peak of the linear absorber is achieved. This enables the primary system to be operated over a wider frequency range without reaching the large amplitudes to the second resonance. The non-linear absorber also has the effect of attenuating the response from the auxiliary mass. Fatigue analysis is carried out to investigate the effect of chaotic motions on mechanical components. The analysis reveals the subharmonic motions are more damaging than chaotic motions, which are in turn more damaging than simple fundamental responses.

Thesis (M.S.)--Ohio University, November, 1987. / Title from PDF t.p.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Young W. Kwon, Young S. Shin. Includes bibliographical references (p. 51). Also available online.

No description available.

This thesis has been done at the company MarineDiesel Sweden, which is currently developing a diesel-powered outboard engine. The focus of the thesis is to design and size a trim/tilt-suspension unit, which secures the outboard to the boat. This system allows adjustments to be done to the outboard while driving in order to achieve better performance and a smoother ride.The methods used in this thesis are brainstorming/concept generation, concept selection, load analyses, CAD-modeling and FEM-analyses. One concept was chosen to proceed with, and further development was carried out. This involved design loops due to feedback from the company as well as the results from the FEM-analyses.The final result is a complete suspension unit, modeled and calculated strength wise, in order for it to fulfill the demands set on it. Four major parts were investigated using FEM, and analyzed in order to keep the stresses low as well as eliminating unnecessary material and thereby reducing weight. The material selected is aluminum, which is lightweight and possible to cast in order to produce complex geometries.

No description available.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Farrokh Ayazi; Committee Member: Dr. Mark G. Allen; Committee Member: Dr. Oliver Brand; Committee Member: Dr. Paul A. Kohl; Committee Member: Dr. Thomas E. Michaels.

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.