Analysis and numerical evaluation of H∞ and H2 optimal design schemes for an electromagnetic shunt damper

This is the author accepted manuscript. The final version is available from American Society of Mechanical Engineers via the DOI in this record.The electromagnetic coupling effect can generate electromagnetic damping to suppress disturbance, which can be utilised for vibration serviceability control in civil engineering structures. An electrodynamic actuator is used as a passive electromagnetic damper (EMD). The EMD is assumed to be attached between the ground and the structure ideally. The kinetic energy of the vibrating structure can be converted to electrical energy to activate the electromagnetic damping. To induce appropriate damping, the two terminals of the damper need to be closed and cascaded with a resonant shunt circuit as an electromagnetic shunt damper (EMSD). In this study, an RLC oscillating circuit is chosen. For determination of optimal circuit components and comparing against the tuned mass damper (TMD), existing H∞ design formulae are applied. This work extends this with a detailed development of an H2 robust optimisation technique. The dynamic properties of a footbridge structure are then selected and used to verify the EMSD optimal design numerically. The vibration suppression performance is analytically equivalent to the dynamic characteristic of the TMD and has feasible installation and better damping enhancement. To further evaluate the potential application of the EMSD, multi-vibration mode manipulation via connecting multiple RLC resonant shunt circuits is adopted. The multiple RLC shunt circuit connecting to EMD is an alternative to the single-mode control of a traditional TMD. Therefore, the EMSD can, in principle, effectively achieve suppression of single and multiple vibration modes.Engineering and Physical Sciences Research Council (EPSRC

Seismic control of a SDOF structure through electromagnetic resonant shunt tuned mass-damper-inerter and the exact H2 optimal solutions

This paper proposes a novel inerter-based component dynamic vibration absorber, namely, electromagnetic resonant shunt tuned mass-damper-inerter (ERS-TMDI). To analyze the performances of the ERS-TMDI, the combined ERS-TMDI and a single degree of freedom system are developed. The H2 norm performances of the ERS-TMDI, whose aim is to minimize the root mean square (RMS) value of structure damage under random ground acceleration excitation, are introduced in comparison with the energy-harvesting series electromagnetic tuned mass dampers (ERS-TMDs), tuned mass-damper-inerter (TMDI) and the classical tuned mass damper (TMD). The closed-form solutions, including the optimal mechanical tuning ratio, the optimal electrical damping ratio, the optimal electrical tuning ratio and the optimal electromagnetic mechanical coupling coefficient, are obtained. It is shown that the ERS-TMDI is superior to both the classical TMD and the ERS-TMD systems for protection from structure damage. Specifically, from the frequency-domain analyses, a case study is performed to illustrate the effectiveness, robustness of the ERS-TMDI and the sensitivity to the parameter changes. From the time-domain analyses, four types of earthquakes are studied to demonstrate the performances of vibration suppression

Vibration control in cricket bats using piezoelectric-based smart materials

The vibrations of a Cricket bat are traditionally passively damped by the inherent damping properties of wood and flat rubber panels located in the handle of the bat. This sort of passive damping is effective for the high frequency vibrations only and is not effective for the low frequency vibrations. Recently, the use of Smart materials for vibration control has become an alternative to the traditional vibration control techniques which are usually heavy and bulky, especially at low frequencies. In contrast, the vibration controls with Smart materials can target any particular frequency of vibration. This has advantages such as it results in smaller size, lighter weight, portability, and flexibility in the structure. This makes it particularly suitable for traditional techniques which cannot be applied due to weight and size restrictions. This research is about the study of vibration control with Smart materials with the ultimate goal to reduce the vibration of the Cricket bat upon contact with a Cricket ball. The study focused on the passive piezoelectric vibration shunt control technique. The scope of the study is to understand the nature of piezoelectric materials for converting mechanical energy to electrical energy and vice versa. Physical properties of piezoelectric materials for vibration sensing, actuation and dissipation were evaluated. An analytical study of the resistor-inductor (R-L) passive piezoelectric vibration shunt control of a cantilever beam was undertaken. The modal and strain analyses were performed by varying the material properties and geometric configurations of the piezoelectric transducer in relation to the structure in order to maximize the mechanical strain produced in the piezoelectric transducer. Numerical modelling of structures was performed and field-coupled with the passive piezoelectric vibration shunt control circuitry. The Finite Element Analysis (FEA) was used in order for the analysis, optimal design and for determining the location of piezoelectric transducers. Experiments with the passive piezoelectric vibration shunt control of beam and Cricket bats were carried out to verify the analytical results and numerical simulations. The study demonstrated that the effectiveness of the passive piezoelectric vibration shunt control is largely influenced by the material properties of the structures to be controlled. Based on the results from simple beam evaluations, vibration reduction of up to 42% was obtained with the designed Smart Cricket bat. Finally, for the control circuit to automatically track the frequency shift of structures required in real applications, an adaptive filter protocol was developed for estimating multiple frequency components inherent in noisy systems. This has immediate application prospects in Cricket bats

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Recent Advances in Robust Control

Robust control has been a topic of active research in the last three decades culminating in H_2/H_\infty and \mu design methods followed by research on parametric robustness, initially motivated by Kharitonov's theorem, the extension to non-linear time delay systems, and other more recent methods. The two volumes of Recent Advances in Robust Control give a selective overview of recent theoretical developments and present selected application examples. The volumes comprise 39 contributions covering various theoretical aspects as well as different application areas. The first volume covers selected problems in the theory of robust control and its application to robotic and electromechanical systems. The second volume is dedicated to special topics in robust control and problem specific solutions. Recent Advances in Robust Control will be a valuable reference for those interested in the recent theoretical advances and for researchers working in the broad field of robotics and mechatronics

Measurements, Models, Systems and Design

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An inerter-based dynamic vibration absorber with concurrently enhanced energy harvesting and motion control performances under broadband stochastic excitation via inertance amplification

This paper examines the performance of a regenerative dynamic vibration absorber, dubbed energy harvesting-enabled tuned mass-damper-inerter (EH-TMDI), for simultaneous vibration suppression and energy harvesting in white noise excited damped linear primary structures. Single-degree-of-freedom (SDOF) structures under force and base excitations are studied as well as multi-degree-of-freedom (MDOF) structures under correlated random forces. The EH-TMDI includes an electromagnetic motor (EM), assumed to behave as a shunt damper, sandwiched between a secondary mass and an inerter element connected in series. The latter element resists relative acceleration at its ends through a constant termed inertance known to be readily scalable in actual inerter device implementations. In this regard, attention is herein focused on gauging the available energy for harvesting at the EM and the displacement variance of the primary structure as the inertance increases through comprehensive parametric investigations. This is supported by adopting simplified inertance-dependent tuning formulae for the EH-TMDI stiffness and damping properties and deriving in closed-form the response of white-noise excited EH-TMDI-equipped SDOF and MDOF systems through linear random vibration analyses. It is found that lightweight EH-TMDIs, having 1% the mass of the primary structure, achieve improved vibration suppression and energy harvesting performance as inertance amplifies. For SDOF structures with grounded inerter, the rate of improvement is higher as the inherent structural damping reduces and the EM shunt damping increases. For MDOF structures with non-grounded inerter, improvement rate is higher as the primary structure flexibility between the two EH-TMDI attachment points increases

Room Modal Equalisation with Electroacoustic Absorbers

The sound quality in a room is of fundamental importance for both recording and reproducing processes. Because of the room modes, the distributions in space and frequency of the sound field are largely altered. Excessive rise and decay times caused by the resonances might even mask some details at higher frequencies, and these irregularities may be heard as a coloration of the sound. To address this problem, passive absorbers are bulky and too inefficient to significantly improve the listening conditions. On the other hand, the active equalization methods may be complicated and costly, and the sound field might not be well controlled, because of the added sound energy in the room. Another approach is the active absorption, which consists in varying the impedance of a part of the enclosure boundaries, so as to balance the sound field thanks to the absorbed sound power into the active boundary elements. The thesis deals with the design and optimization of electroacoustic absorbers intended to specifically reduce the effect of the unwanted room modes. These active absorbers are closed box electrodynamic loudspeaker systems, whose acoustic impedance at the diaphragms is judiciously adjusted with passive or active components to maximize their absorption performance in the domain in which it is located. Several topologies merging sensor- and shunt-based methods are proposed resulting in an efficient and broadband sound absorption at low frequencies. A multiple degree-of-freedom target impedance that is assigned at the transducer diaphragms is then optimized to lower the modal decay times at best. The performance of the electroacoustic absorbers for the modal equalization is investigated in actual listening rooms, and their audible effect is subjectively evaluated. The overall combination of concepts and developments proposed in this thesis paves the way towards new active absorbers that may improve the listening experience at low frequencies in rooms