Aktivna ćelija metamaterijala za nerecipročnu transmisiju vibracija

master's thesis

• Title (english): Active metamaterial cell for non-reciprocal vibration transmission
• Author: Marin Jalšić
• Mentor: Neven Alujević (mentor)
• Committee member: Ivica Skozrit (predsjednik povjerenstva)
• Committee member: Igor Karšaj (član povjerenstva)
• Committee member: Nikola Vladimir (član povjerenstva)
• Committee member: Marko Jokić (član povjerenstva)
• Committee member: Petar Ilinčić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2021-07-16, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

U ovom radu osmišljena je ćelija aktivnog metamaterijala koja ne podliježe principu dinamičke recipročnosti. Izveden je matematički model elektromehaničkog sustava s koncentriranim parametrima kojim se opisuje dinamičko ponašanje ćelije. Unutar metamaterijala implementirane su dvije decentralizirane povratne veze po brzini vibracija, pri čemu parovi mjernih i pogonskih članova povratnih veza nisu kolocirani.
Takav model iskorišten je kako bi se provela detaljna analiza stabilnosti s posebnim naglaskom na određivanje parametara pasivnog sustava za koje uključivanje povratne veze osigurava zadovoljavajuću rezervu stabilnosti. Pokazuje se da je, uz zanemarivanje dinamičkog odziva mjernih i pogonskih članova moguće osigurati bezuvjetnu stabilnost aktivnog sustava, a ukoliko pretvornici posjeduju vlastitu dinamiku tada sustav postaje uvjetno stabilan.
Performanse regulacijskog sustava kvantificirane su razmatranjem H2 norme karakterističnih prijenosnih funkcija sustava prilikom zamjene točaka uzbude i odziva. Time je omogućen uvid u ovisnost fenomena gubitka dinamičke recipročnosti sustava, kao i njegovih mogućnosti suzbijanja vibracija u željenom smjeru o pojačanju povratnih veza.
Matematički model verificiran je eksperimentalnim prototipom ćelije koja je izrađena tehnologijom 3D ispisa. Eksperimentalni je postav opremljen senzorima, kao i elektrodinamičkim vibratorima koji su potrebni za ostvarivanje povratnih veza. Na izrađenom prototipu ćelije aktivnog metamaterijala provedena su mjerenja u slučaju da je povratna veza otvorena, a sustav pasivan te u slučaju da su povratne veze zatvorene, čime sustav postaje aktivan. Mjerenjima je zabilježen značajan gubitak dinamičke recipročnosti u sustavu sa zatvorenim povratnim vezama, kao i iznimno smanjenje transmisije vibracija u željenom smjeru u usporedbi s pasivnim sustavom.

Abstract (english)

In this thesis a cell of an active metamaterial, which does not obey the principle of dynamic reciprocity, is developed. A lumped parameter mathematical model of the electromechanical system is derived, which describes the dynamic behaviour of the cell. Within the metamaterial cell two decentralized velocity feedback loops are implemented, where the sensor-actuator pairs are non-collocated.
The derived model is used to conduct a detailed analysis of the system in terms of stability, paying special attention to the selection of parameters of the passive system which would ensure good stability margins. It is shown that, when the dynamics of the sensors and actuators are neglected, the system can be made unconditionally stable, whereas when these dynamics are taken into account no such property can be guaranteed, and the system is conditionally stable.
Performance of the control system is quantified by considering the H2 norm of the characteristic transfer functions of the system when the points of excitation and response are switched. This kind of performance analysis gives insight into the phenomenon of reciprocity loss, as well as the ability of the system to suppress vibrations in a desired direction, as they depend on feedback gain.
The theoretical model is verified using an experimental prototype of the metamaterial cell, which is 3D printed. The experimental setup is equipped with sensors and electrodynamic shakers which are necessary for the realisation of feedback loops. Measurements were made both with and without feedback, for comparison between the passive and active case. Considerable loss of dynamic reciprocity is registered when feedback is present, as well as a substantial reduction in vibration transmission in the desired direction, as compared to the passive case.

• Keywords: aktivna kontrola vibracija; dinamička recipročnost; aktivni metamaterijali; stabilnost; matematički modeli s koncentriranim parametrima; eksperimentalna verifikacija matematičkih modela
• Keywords (english): active vibration control; dynamic reciprocity; active metamaterials; stability; lumped parameter mathematical models; experimental verification of mathematical models
• Language: croatian
• URN:NBN: urn:nbn:hr:235:617289
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2023-07-15
• Created on: 2021-07-13 12:46:49