Nonlinear vibration isolation of inertial measurement unit

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2018
Dönmez, Ata
In engineering systems, dynamic parameters of systems such as acceleration, velocity, etc. are measured instantaneously to provide feedback for control systems. Since measurement equipment is sensitive to vibratory environment, performance of them is directly related to how effectively vibration is isolated. Linear vibration isolation systems have limitations due to static deflections and damping characteristic. Therefore, nonlinear elements can be used to improve isolation performance.In this thesis, firstly the vibration isolation of the engineering systems is considered. Then the problem is narrowed to inertial measurement units (IMUs) and the specific vibration isolation issues of the IMUs are studied. Mathematical model of linear six degrees of freedom vibration isolation system containing a mechanical structure mounted on elastomeric elements is achieved. For a given isolator position and mass properties of the system, system matrices are obtained. Modal properties of the isolated system, response to harmonic, random excitations and static deflections under static loadings are considered as critical parameters to evaluate effectiveness of the isolation. vi In shaker table, sine sweep and random vibration experiments are performed on an IMU suspended on commercial rubber isolators. Experiment and analysis software results are compared. In the next step, nonlinear elements such as high-static-low-dynamic-stiffness and special version of it, quasi-zero-stiffness, geometrically nonlinear damping and dry friction are implemented to a single degree of freedom system. The nonlinear differential equations of motion of the isolation system are converted into a set of nonlinear algebraic equations by using harmonic balance method, which are solved by using Newton’s method with arc-length continuation. Several case studies are performed and the effect of nonlinearities on the isolation performance is studied. Validation of the solution method is performed by both time simulations and experiments. Multi-Harmonic displacement profiles are applied to quad-lap elastomer isolator by means of servo position control. Dynamic properties of the rubber isolator under multi-harmonic displacement profile is investigated. Then, isolation performance is studied analytically for the rubber isolator whose dynamic properties are obtained experimentally.

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Citation Formats
A. Dönmez, “Nonlinear vibration isolation of inertial measurement unit,” M.S. - Master of Science, Middle East Technical University, 2018.