Mechanical Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2795
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Item Design of a Programmable Active Acoustic Metamaterial(2012) Smoker, Jason James; Baz, Amr; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Metamaterials are artificial materials engineered to provide properties which may not be readily available in nature. The development of such class of materials constitutes a new area of research that has grown significantly over the past decade. Acoustic metamaterials, specifically, are even more novel than their electromagnetic counterparts arising only in the latter half of the decade. Acoustic metamaterials provide a new tool in controlling the propagation of pressure waves. However, physical design and frequency tuning, is still a large obstacle when creating a new acoustic metamaterial. This dissertation describes active and programmable design for acoustic metamaterials which allows the same basic physical design principles to be used for a variety of application. With cloaking technology being of a great interest to the US Navy, the proposed design approach would enable the development of a metamaterial with spatially changing effective parameters while retaining a uniform physical design features. The effective parameters would be controlled by tuning smart actuators embedded inside the metamaterial structure. Since this design is based on dynamic effective parameters that can be electrically controlled, material property ranges of several orders of magnitude could potentially be achieved without changing any physical parameters. With such unique capabilities, physically realizable acoustic cloaks can be achieved and objects treated with these active metamaterials can become acoustically invisible.Item Virtual Reality Modeling of a Car Suspension with Active Control Capability(2009) Smoker, Jason James; Baz, Amr M.; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis presents the evolution of a full car model into virtual reality environment to visually demonstrate the dynamics of a car resulting from various inputs controlled both passively and actively. The model is a seven degree of freedom system that can be configured to be excited by either a bump or harmonic input. Active controls available to the system include the well known Linear Quadratic Regulator (LQR) as well as a new Nonlinear Energy Absorber (NEA) which utilizes both nonlinear springs and nonlinear damper. The mathematics of the plant, the kinematics of the system, and the visual specifications of the scene are integrated into a three-dimensional environment where the user can be immersed in the environment and witness in real-time the response of a specific configuration. This project was developed with the mindset that dynamic models of systems can be better understood through visual realization and interaction.