Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/89724
Title: Novel vibration control strategies using electromagnetic dampers : from fundamental to applications
Authors: Li, Jinyang
Degree: Ph.D.
Issue Date: 2020
Abstract: Over the years, various types of dampers have been researched, designed, manufactured, and applied to existing structures to achieve favorable vibration control performances. One emerging type, namely, electromagnetic damper (EMD), has recently received an increasing research interest among scholars and engineers owing to its unique feature of transforming structural kinetic energy into electrical energy instead of heat dissipation. This transformation enables exciting possibilities that are previously inconceivable. On the one hand, the analogue relations shared between electrical and mechanical systems enable the efficient emulation of mechanical dampers by using their electrical counterparts. Given the compact sizes of electrical elements, complex and adaptive damper design can be realized within electrical domain which can be barely achieved mechanically. On the other hand, the transformed electrical energy can be potentially harvested and stored for other usages. This thesis proposes and systematically investigates two novel EMD designs, termed Designs I & II that emphasize the aforementioned two advantages. By taking advantage of the analogue relations between mechanical and electrical systems, the first design can realize versatile mechanical damper behaviors by using a single EMD connected to different shunt circuits. We explore the existence of motor inner resistance as a major obstacle preventing wide applications of existing EMDs, and solve the issue by introducing negative impedance converter with voltage inversion (VNIC) module. Consequently, we validate the feasibility and effectiveness of the established EMD-VNIC system (Design I) through the following two applications: (1) vibration isolation table test emphasizing tuneable behaviors; and (2) vibration control of a full-scale 135m-long bridge cable. Nonetheless, Design I still requires a certain amount of energy input to drive the VNIC module, which is unfavorable from an energy perspective. Considering that kinetic energy of the controlled structures can potentially serve as a power source, we subsequently propose a novel self-powered control strategy (i.e., Design II) that offers simultaneous energy harvesting and actuation functions. In addition to the introduction of system topology and working principles, we first deploy Design II to realize versatile damper behaviors that are comparable with those achieved by Design I. Next, Design II further realizes an authentic self-powered active control of a single degree of freedom (SDOF) system under skyhook control algorithm. The above findings show that Design II utilizes the to-be-dissipated energy to provide active control, which is different from conventional practice of continuously injecting energy into the system. Finally, we discuss the feasibility of large-scale application of the proposed EMDs together with another novel damper type called eddy current damper (ECD) with respect to the concept of damping density. We also proposed practical ways of enlarging the damping densities of EMDs and ECDs. The comparison results among EMDs, ECDs, and market-available existing viscous fluid dampers reveal the great potential of novel damper types to replace traditional dampers and confirm their feasibilities and scalability in large-scale structures. Through a combination of theoretical, numerical, and experimental studies, this thesis explores several innovative vibration control strategies by using the salient features of EMDs. The outcome facilitates the potential applications of these devices to future smart mechanical and civil structures.
Subjects: Vibration -- Control
Electromagnetic devices -- Design and construction
Damping (Mechanics)
Hong Kong Polytechnic University -- Dissertations
Pages: xviii, 191 pages : color illustrations
Appears in Collections:Thesis

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