Tesi sul tema "Active vibration reduction"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Active vibration reduction.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-37 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Active vibration reduction".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Ganguli, ABHIJIT. "Chatter reduction through active vibration damping". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210980.
Abstract (sommario):
The aim of the thesis is to propose active damping as a potential control strategy for chatter instability in machine tools.The regenerative process theory explains chatter as a closed loop interaction between the structural dynamics and the cutting process. This is considered to be the most dominant reason behind machine tool chatter although other instability causing mechanisms exist.
The stability lobe diagram provides a quantitative idea of the limits of stable machining in terms of two physical parameters: the width of contact between tool and the workpiece, called the width of cut and the speed of rotation of the spindle. It is found that the minimum value of the stability limit is proportional to the structural damping ratio for turning operations. This important finding provides the motivation of influencing the structural dynamics by active damping to enhance stability limits of a machining operation.
A direct implementation of active damping in an industrial environment may be difficult. So an intermediate step of testing the strategy in a laboratory setup, without conducting real cutting is proposed. Two mechatronic "Hardware in the Loop" simulators for chatter in turning and milling are presented, which simulate regenerative chatter experimentally without conducting real cutting tests. A simple cantilever beam, representing the MDOF dynamics of
the machine tool structure constitutes the basic hardware part and the cutting process is simulated in real time on a DSP board. The values of the cutting parameters such as spindle speed and the axial width of cut can be changed on the DSP board and the closed loop interaction between the structure and the cutting process can be led to instability.
The demonstrators are then used as test beds to investigate the efficiency of active damping, as a potential chatter stabilization strategy. Active damping is easy to implement, robust and does not require a very detailed model of the structure for proper functioning, provided a collocated sensor and actuator configuration is followed. The idea of active damping is currently being implemented in the industry in various metal cutting machines as part of the European Union funded SMARTOOL project (www.smartool.org), intended to propose smart chatter control technologies in machining operations.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
2
Boffa, John. "Model Reduction of Large Structural Systems for Active Vibration Control". University of Technology, Sydney. Faculty of Engineering, 2006. http://hdl.handle.net/2100/338.
Abstract (sommario):
This thesis studies the applicability of the Dynamic model reduction method that is used for direct plant order reduction in the active vibration control of large and flexible structures. A comparison of the performances between the reduced models produced by the Dynamic model reduction method and those obtained by other common model reduction methods such as the Guyan method, and the Mode-displacement method have been carried out. By using a full analytical model of a twenty storey building as the reference, each three degrees of freedom model was compared by computer simulation. The open-loop frequency response simulation, open-loop earthquake simulation, and the closed-loop earthquake simulation were all used to initially evaluate the reduced models. The accuracy of the frequency responses was assessed with sinusoidal applied forces, and for the closed-loop dynamic analysis, an active mass damper at the top storey and a recorded earthquake excitation was used. When compared with the simulation results of the Guyan method, the Dynamic method has many advantages, especially in terms of its accuracy at the high frequency range. The Mode-displacement method produces reduced models that are good for dynamic analysis of open-loop systems, but it was found to be inconvenient for use in active control. Finally, the Dynamic model reduction method and Guyan method were compared using experimental test results. A 2.5m tall building model with 20 floors was used as the plant, with a linear motor installed at the top storey for the purposes of active-damping. Although the results of simulations would suggest that both models perform sufficiently, experimental testing proved that only the Dynamic model performs adequately for this specific application of active control. The problem associated with most model reduction methods, such as the Guyan, is that they are based on full-order models that were derived from the linear elastic theory. The versatility of the Dynamic model reduction method is such that it provides the option of obtaining system parameters directly from experiment, not just from theory. The experimental procedure ensures that the Dynamic model reduction method forms an accurate description of the real system dynamics. The applicability of this method for obtaining low-order plant models was demonstrated through real-time active control testing of the model structure, while it was subject to a sinusoidal excitation. The tests have shown that the Dynamic model reduction method can be used as an alternative approach for the model reduction of structural systems for the purpose of active vibration control.
3
Huyanan, Satienpong. "An active vibration absorber for chatter reduction in machining". Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486712.
Abstract (sommario):
In the early days of the manufacturing industry, the limiting factor in obtaining higher material removal rates was 'Chatter', an unstable cutting condition with excessive vibrations. Maximum productivity can only be obtained using the knowledge of the theory of regenerative chatter. In the era of modem manufacturing industry, where the greater quality and productivity are increasingly demanded, especially the requirement to understand and avoid chatter is even greater. The key answering to this challenge is to increase the rate of material removal while maintaining stable cutting conditions through reducing chatter during machining operations. In this regard, an active vibration absorber can be used to effectively reduce the undesired vibrations of the structure, thereby increasing the border line of chatter stability. However, to date there has been little attention in applying this technique in the application ofmilling chatter suppression, especially for a flexible workpiece. In this thesis, the stability of milling process dynamics is theoretically investigated using the method of semi-discretization. An alternative means of improving stability in milling is also presented by developing the extended method of semi-discretization for the milling systems with variable time delay. This can be used to predict not only the stability but also the chatter frequencies for milling with irregular pitch cutters. Motivated by an interest in practically improving the stability margin in the milling process, a practical and straightforward active vibration control system with acceleration feedback is implemented using a proof-mass actuator. Based on the general framework of virtual passive control, three controller strategies are first demonstrated and evaluated through a laboratory based vibration study, consisting of virtual sky-hook damper, virtual passive absorber and virtual passive-active absorber. The· results indicate that virtual passive absorber control could be a simple and robust solution to the application ofmachining chatter reduction. Through the initial study of the theory of regenerative chatter, analytical optimizations of dynamic vibration absorbers are developed for application to chatter suppression. The performance of a virtual passive absorber to suppress workpiece chatter during high speed machining is then experimentally investigated for each tuning scheme, including the virtual sky-hook damper scheme. The results demonstrate that although the performance of the active milling chatter suppression system is limited by the actuator saturation, the chosen control strategy can provide at least a 6-fold improvement in the workpiece stability using a small actuator.
4
Boffa, John. "Model reduction of large structural systems for active vibration control /". Electronic version, 2002. http://adt.lib.uts.edu.au/public/adt-NTSM20060317.113054/index.html.
5
Gan, Zengkang. "Adaptive control of an active seat for occupant vibration reduction". Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665426.
Abstract (sommario):
Vehicle occupants are typically exposed to unpleasant whole-body vibration (WBV) for extended period of time. It is well known that the transmission of unwanted vibration to the human body can lead to fatigue and discomfort. Moreover, the unwanted vibration normally distributed in the low-frequency range has been found as the main risk factor for lower back pain and lumbago, which seriously affect the health and working performance of occupants. Thus vibration cancellation on seats has attracted considerable interest in recent years. So far, for most vehicle seats, vibration isolation is achieved passively by using seat cushions and conventional energy absorbers, which have very limited performance in the low-frequency range. The work presented in this thesis forms a successful development and experimental study of an active seat and control algorithm for occupants’ WBV reduction under low frequency excitations. Firstly, a modelling study of the seat human subjects (SHS) and an extensive experimental measurement of the vibration transmissibility of a test dummy and vehicle seat are carried out. The biodynamic responses of SHS exposed to uncoupled vertical and fore-and-aft WBV is modelled. A comparison with the existing models is made and the results show that an improved fit with the aggregated experimental data is achieved. Secondly, an active seat is developed based upon the observations and understanding of the SHS and seat system. The characteristics of the active seat dynamics are identified through experimental tests found suitable for the development of an active seat to attenuate the vibration experienced by vehicle occupants. The vibration cancellation performance of the active seat is initially examined by feedforward plus proportional-integral (PI) control tests. Through these tests, the effectiveness of the actuators control authority is verified, but the limitations are also revealed. Because the active seat system is subject to non-linear and time-varying behaviour, a self-tuning fully adaptive algorithm is a prime requirement. The Filtered-x Least-Mean-Square (FXLMS) algorithm with the Fast-block LMS (FBLMS) system identification technique is found suitable for this application and is investigated through experimental tests. Substantial vibration reductions are achieved for a variety of input vibration profiles. An excellent capability of the active seat and control system for efficiently reducing the vibration level of seated occupants under low-frequency WBV is demonstrated.
6
Martinovic, Zoran N. "Sensitivity of active vibration control to structural changes and model reduction". Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53641.
Abstract (sommario):
The analytical study presented here is concerned with by two types of sensitivity of active vibration control of large space structures (LSS). The first one required for assessing robustness, is the sensitivity of the performance and stability of the control system to changes in structure and to model reduction. The second type is the sensitivity of the optimum design of the control system to changes in the structure. This sensitivity is of interest in assessing the need for integrated structure/control design.
Three direct rate feedback (DRF) control techniques are studied for a laboratory structure which has characteristics of LSS and then compared to standard linear quadratic (LQ) control. The baseline design of each control system is obtained first and then sensitivity analysis conducted.
An uncoupled DRF control law which minimized the sum of gains subject to requirements on performance was not robust to structural changes, and small changes in the structure caused notable increase in performance compared to that of the baseline design and therefore a potential gain from simultaneous structure/control design was indicated.
Two coupled DRF techniques are proposed. A Minimum Force DRF (MF-DRF) law minimized maximum force of any actuator, while a Linear Quadratic DRF (LQ-DRF) law minimized the standard quadratic performance index for initial conditions in the shape of the first six natural modes. Both techniques guaranteed system stability. The LQ control law was found to be only slightly better than the simpler MF·DRF law in terms of the quadratic performance index and poorer than the LQ-DRF law. However the LQ control requires model reduction and was found to be sensitive to errors in that process. For example, the LQ design lost its stability when the structure was modified by adding a non-structural mass to it.
A separate experimental study was conducted simultaneously with this study to verify theoretical results. Good agreement was found between analytical results and experimental measurements for the investigated control techniques.Ph. D.
7
LI, MINGFENG. "ACTIVE VIBRATION CONTROL OF A GEARBOX SYSTEM WITH EMPHASIS ON GEAR WHINE REDUCTION". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115131866.
8
Clements, Kristen Lynn. "Active control of an automobile suspension system for reduction of vibration and noise". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30359.
Abstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 79-82).
A new method for controlling road noise transmitted through the suspension system of an automobile was developed, using a Lincoln LS automobile as the target vehicle. In this vehicle, road surface roughness generates vibrations that are transmitted into the automobile primary through a single bushing (the "point 4 bushing") on each of the front suspension control arms. An electromagnetic actuator was designed, built, and tested on a Lincoln LS with simulated roads noise. The actuator applies a force across the point 4 bushing, in response to accelerations of the vehicle frame, just inboard of the bushing, with the goal of reducing the net forces transmitted into the vehicle frame, which ultimately produce unwanted interior noise. Several tonal controllers were developed, each designed to operate in a narrow frequency band, and to eliminate the cross member (frame) vibration just inside the point 4 bushing. The tonal controllers were able to eliminate cross member vibration at the desired frequency. Eliminating the cross member vibration resulted in modest reductions interior sound levels. A successful vibration control system (in this vehicle) would need to eliminate cross member vibrations over frequency range 100 to 200 Hz. However, a broadband controller with this electromagnetic actuator system proved to be difficult, due to undesirable non-minimum phase dynamics.
by Kristen Lynn Clements.
S.M.
9
Curtis, A. R. D. "The theory and application of quadratic minimization in the active reduction of sound and vibration". Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/52272/.
Abstract (sommario):
Active sound reduction is the use of active sources of sound, that is devices which are potentially sources of sound energy, to modify a preexisting sound field in such a way that the overall effect is a reduction in sound. Until recently the most common approach in active sound control was to attempt to achieve complete cancellation of the sound. This is possible at single points but is practically impossible over an appreciable region. A more modest and practical aim is to try to reduce the sound field by as much as possible by minimizing some overall measure of the amplitude of the sound field. This thesis examines the technique of sound field minimization. Candidate sound field measures which are suitable for minimization are presented and discussed. The quantities include acoustic energy, intensity and power flow as well as a practical measure, the sum of the squares of the signals from a number of sensors. Theoretical simulations and experimental implementations are used to evaluate sound field minimization techniques. The discussion and experiments are extended to the active reduction of structural vibrations.
10
Becker, Jens. "Semi-active control of friction dampers and feedforward tracking control design for structural vibration reduction". Tönning Lübeck Marburg Der Andere Verl, 2009. http://d-nb.info/995846200/04.
11
Huang, Haoyu. "A temperature controlled semi-active tuned mass damper using shape memory alloy for vibration reduction applications". Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720664.
Abstract (sommario):
This study developed a temperature controlled semi-active tuned mass damper (TMD) using shape memory alloy (SMA) for civil structural applications. It addressed the off-tuning issues caused by the variances in structural mass and stiffness when in service, since off-tuning of the TMD increases the structural response. The effect of in-service temperature on SMA can provide adaptive dynamic properties to TMD. Therefore, the natural frequencies can be adjusted to an optimal range. In this thesis, the material characterisation of SMA is studied through acting dynamic cyclic loading. It was found that Cu-Al-Mn SMA has a superior self-centring capacity, adequate fatigue life and a large damping ratio. By controlling the in-service temperature of a cantilever SMA beam, it was found that the stiffness of the SMA increases and the damping ratio reduces with higher temperatures in free vibration. It is important to note that these properties are increasingly sensitive to temperature when pre-stress is applied and the pre-stressed level is approximate to the phase transformation temperature. The potential for employing SMA with temperature control in a semi-active TMD system is considerable. The feasibility of this type of semi-active TMD was studied experimentally by mounting the SMA-based TMD on a cantilever beam to reduce the excessive vibration caused by off-tuning. For lateral loadings, the non-pre-stressed SMA was applied to a steel framed structure for addressing the off-tuning issues experienced under actions caused by earthquakes and wind by conducting shaking table tests. Cooling the SMA can effectively retune the structural frequencies and attenuate the vibration, but heating the SMA contributed limited effectiveness. This is because the damping losses and stiffness variance are relatively small while heating. In simulation studies, a timber floor-TMD system was modelled under vertical excitations. Both heating and cooling of the SMA can effectively retune the structure from its off-tuned state and can consequently reduce the excessive vibration. Moreover, temperature control of the SMA can shift the natural frequencies to avoid resonance under harmonic loadings. Based on the theoretical and experimental studies in this thesis, the temperature controlled semi-active TMD with SMA can address the off-tuning issues experienced by civil structures under various in-service excitations.
12
Brakna, Mohammed. "Sensor and actuator optimal location for dynamic controller design. Application to active vibration reduction in a galvanizing process". Electronic Thesis or Diss., Université de Lorraine, 2023. https://docnum.univ-lorraine.fr/ulprive/DDOC_T_2023_0152_BRAKNA.pdf.
Abstract (sommario):
Les objectifs de cette thèse sont de déterminer un modèle à la fois suffisamment précis mais numériquement exploitable pour proposer des méthodologies de placement de capteurs et d'actionneurs pour le contrôle actif de vibration dans une ligne de galvanisation. La galvanisation consiste à recouvrir un métal (dans notre étude : de l'acier) par une couche protectrice de zinc qui évite la corrosion due à l'air. L'épaisseur de cette couche doit être constante pour garantir les propriétés mécaniques et l'état de surface du produit. Dans une ligne de galvanisation, la bande d'acier en mouvement est chauffée puis plongée dans un bain de zinc liquide avant d'être essorée par des buses projetant de l'air. L'air pulsé, ainsi que la rotation des cylindres d'entrainement de la bande - entre autres - créent des vibrations qui viennent perturber l'essorage et donc la régularité du dépôt de zinc. Un contrôle actif est donc nécessaire, par exemple au moyen d'électro-aimants placés de part et d'autre de la bande d'acier en mouvement. Dans un premier temps, un modèle de comportement de la bande d'acier dans la ligne de galvanisation prenant en compte la présence et la propagation des vibrations a été obtenu par discrétisation spatiale d'une équation aux dérivées partielles. Ce modèle de type espace d'état a été validé en simulation et expérimentalement sur une ligne de galvanisation pilote d'ArcelorMittal Research à Maizières-lès-Metz. Une fois ce modèle établi, l'objectif de l'étude est la recherche du placement optimal de capteurs, pour mesurer le plus efficacement les vibrations de la bande, mais également d'actionneurs pour minimiser l'amplitude de ces vibrations par une loi de commande adaptée. Ces problèmes de placements optimaux sont au cœur des thématiques de contrôle actif des vibrations et se retrouvent dans de nombreux domaines d'application. Une méthode de placement basée sur la maximisation des Grammiens a été proposée en vue de réduire l'impact des perturbations sur le système. Différentes stratégies de contrôle ont été envisagées telles que le retour d'état observé et le retour d'état étendu observé pour améliorer les résultats en tenant compte de l'estimation des perturbations par un observateur PI (proportionnel-intégral). Des résultats de simulations et expérimentaux illustrent les résultats obtenusThe aims of the present PhD thesis are to determine a model that is both sufficiently accurate and numerically exploitable to propose optimal placement of sensors and actuators for active vibration control in a galvanizing line. A continuous hot-dip galvanizing process consists in covering a metal (here: a steel band) by a protective layer of zinc which avoids the corrosion due to the air. The thickness of this layer must be constant to guarantee the mechanical properties and surface condition of the product. In a galvanizing line, the moving steel strip is heated and then immersed in a liquid zinc bath before being wiped out by nozzles projecting air. The air flow, as well as the rotation of the driving rolls, among other things, creates vibrations affecting the wiping process and thus the regularity of the zinc deposit. Active control is therefore necessary, for example by means of electromagnets placed on either side of the moving steel strip. In a first step, a behavioral model of the steel strip taking into account the presence and propagation of vibrations was obtained by spatial discretization of a partial differential equation. This state space model was validated in simulation and experimentally on a pilot galvanizing line of ArcelorMittal Research in Maizières-lès-Metz. Once this model is established, the objective of the study is to find the optimal placement of sensors, to measure the vibrations of the strip as efficiently as possible, but also of actuators to minimize the amplitude of these vibrations by an appropriate control law. These problems of optimal placement are at the heart of the issues of active vibration control and are found in many fields of application. An optimal placement method based on Gramian maximization has been proposed in order to reduce the impact of disturbances on the system. Different control strategies have been considered such as (i) observed state feedback based on Kalman filter and LQ regulator; and (ii) extended observed state feedback to improve the results by also taking into account the disturbance estimation provided by a PI (proportional-integral) observer. Simulation and experimental results illustrate the thesis contributions
13
Wang, Peng. "Active vibration control in a specific zone of smart structures". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC007/document.
Abstract (sommario):
Cette recherche vise à résoudre un problème particulier du contrôle de vibration des structures intelligentes. Notre objectif est de réduire les vibrations dans une zone spécifique de la structure intelligente avec une perturbation qui couvre une large gamme de fréquences. De plus, dans cette zone spécifique, ni l'actionnement ni la détection ne sont possibles.Ici, nous faisons face à plusieurs défis principaux. Premièrement, nous devons contrôler les vibrations d’une zone spécifique de la structure, alors que nous n’avons accès aux mesures que dans d’autres zones. Deuxièmement, la large bande passante de la perturbation implique que nombreux modes doivent être contrôlés au même temps, ce qui nécessite l'utilisation de plusieurs actionneurs et capteurs. Cela conduit à un contrôleur MIMO difficile à obtenir avec les méthodes classiques de conception de contrôleur. Troisièmement, il faut éviter le problème de propagation, qui consiste à garantir la stabilité en boucle fermée lorsque le contrôleur basé sur un modèle est appliqué à la configuration réelle. Pour relever ces défis, nous étudions deux stratégies de contrôle: le contrôle centralisé et le contrôle distribué.Pour le contrôle centralisé, nous proposons une méthodologie qui nous permet d’obtenir un contrôleur MIMO simple permettant de relever ces défis. Tout d'abord, plusieurs techniques de modélisation et d’identification sont appliquées pour obtenir un modèle précis d'ordre faible de la structure intelligente. Ensuite, une méthode de synthèse basée sur le contrôle H_∞ avec un critère H_∞ particulièrement proposé est appliquée. Ce critère H_∞ intègre plusieurs objectifs de contrôle, y compris les défis principaux. En particulier, le problème de débordement se transforme en un problème de stabilité robuste et sera garanti en utilisant ce critère. Le contrôleur H_∞ obtenu est une solution standard du problème H_∞. Le contrôleur final est obtenu en simplifiant ce contrôleur H_∞ sans perdre la stabilité en boucle fermée ni dégrader les performances. Cette méthodologie est validée sur une structure de poutre avec des transducteurs piézoélectriques et la zone centrale est celle où les vibrations devraient être réduites. L'efficacité du contrôleur obtenu est validée par des simulations et des expériences.Pour le contrôle distribué, on considère la même structure de poutre et les mêmes objectifs de contrôle. Il existe des méthodes visant à concevoir des contrôleurs distribués pour les systèmes spatialement interconnectés. Cette recherche propose une méthode basée sur la FEM, associée à plusieurs techniques de réduction de modèle, permettant de discrétiser spatialement la structure de poutre et d'en déduire les modèles d’espace d'état des sous-systèmes interconnectés. La conception des contrôleurs distribués ne sera pas abordée dans cette rechercheThis research aims at solving a particular vibration control problem of smart structures. We aim at reducing the vibration in a specific zone of the smart structure under the disturbance that covers a wide frequency band. Moreover, at this specific zone, neither actuation nor sensing is possible.Here we face several main challenges. First, we need to control the vibration of a specific zone of the structure while we only have access to measurements at other zones. Second, the wide bandwidth of the disturbance implies that numerous modes should be controlled at the same time which requires the use of multiple actuators and sensors. This leads to a MIMO controller which is difficult to obtain using classical controller design methods. Third, the so-called spillover problem must be avoided which is to guarantee the closed-loop stability when the model-based controller is applied on the actual setup. To tackle these challenges, we investigate two control strategies: the centralized control and the distributed control.For centralized control, we propose a methodology that allows us to obtain a simple MIMO controller that accomplishes these challenges. First, several modeling and identification techniques are applied to obtain an accurate low-order model of the smart structure. Then, an H_∞ control based synthesis method with a particularly proposed H_∞ criterion is applied. This H_∞ criterion integrates multiple control objectives, including the main challenges. In particular, the spillover problem is transformed into a robust stability problem and will be guaranteed using this criterion. The obtained H_∞ controller is a standard solution of the H_∞ problem. The final controller is obtained by further simplifying this H_∞ controller without losing the closed-loop stability and degrading the performance. This methodology is validated on a beam structure with piezoelectric transducers and the central zone is where the vibration should be reduced. The effectiveness of the obtained controller is validated by simulations and experiments.For distributed control, we consider the same beam structure and the same control objectives. There exist methods aiming at designing distributed controllers of spatially interconnected system. This research proposes a FEM based method, combined with several model reduction techniques, that allows to spatially discretize the beam structure and deduce the state-space models of interconnected subsystems. The design of distributed controllers will not be tackled in this research
14
Beck, Benjamin Stewart. "Negative capacitance shunting of piezoelectric patches for vibration control of continuous systems". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45850.
Abstract (sommario):
The ability to reduce flexural vibrations of lightweight structures has been a goal for many researchers. A type of transducer-controller system that accomplishes this is a piezoelectric patch connected to an electrical impedance, or shunt. The piezoelectric patch converts the vibrational strain energy of the structure to which it is bonded into electrical energy. This converted electrical energy is then modified by the shunt to influence to mechanical response. There are many types of shunt circuits which have demonstrated effective control of flexural systems. Of interest in this work is the negative capacitance shunt, which has been shown to produce significant reduction in vibration over a broad frequency range. A negative capacitance circuit produces a current that is 180̊ out of phase from a traditional, passive capacitor. In other words, the voltage of the capacitor decreases as charge is added. The negative capacitance shunt consists of a resistor and an active negative capacitance element. By adding a resistor and negative capacitor to the electrical domain, the shunt acts as a damper and negative spring in the mechanical domain.
The performance of the negative capacitance shunt can be increased through proper selection of the shunt's electrical components. Three aspects of component selection are investigated: shunt efficiency, maximum suppression, and stability. First, through electrical modeling of the shunt-patch system, the components can be chosen to increase the efficiency of the shunt for a given impedance. Second, a method is developed that could be utilized to adaptively tune the magnitude of resistance and negative capacitance for maximum control at a given frequency. Third, with regard to stability, as the control gain of the circuit is increased, by adjusting the circuit parameters, there is a point when the shunt will become unstable. A method to predict the stability of the shunt is developed to aid in suppression prediction.
The negative capacitance shunt is also combined with a periodic piezoelectric patch array to modify the propagating wave behavior of a vibrating structure. A finite element method is utilized to create models to predict both the propagation constant, which characterizes the reduction in propagating waves, and the velocity frequency response of a full system. Analytical predictions are verified with experimental results for both a 1- and 2-D periodic array. Results show significant attenuation can be achieved with a negative capacitance shunt applied to a piezoelectric patch array.
Three electromechanical aspects are developed: design for maximum suppression, more accurate stability prediction, and increased power-output efficiency. First, a method is developed that may be used to adaptively tune the magnitude of resistance and negative capacitance for maximum suppression. Second, with regard to stability, a method is developed to predict the circuit components at which the circuit will obtain a stable output. Third, through electrical modeling of the shunt-patch system, the components are chosen to increase the power output efficiency of the shunt circuit for a given impedance.
The negative capacitance shunt is also combined with a periodic piezoelectric patch array to modify the propagating wave behavior of a vibrating structure. Analytical predictions are verified with experimental results for both a 1- and 2-D periodic array. Results show significant attenuation can be achieved with a negative capacitance shunt applied to a piezoelectric patch array.
15
Kim, Taeho, e Monika Ivantysynova. "Active Vibration Control of Axial Piston Machine using Higher Harmonic Least Mean Square Control of Swash Plate". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199412.
Abstract (sommario):
Noise emission is a major drawback of the positive displacement machine. The noise source can be divided into structure borne noise source (SBNS) and fluid borne noise source (FBNS). Passive techniques such as valve plate optimization have been used for noise reduction of axial piston machines. However, passive techniques are only effective for limited operating conditions or at least need compromises in design. In this paper, active vibration control of swash plate is investigated for vibration and noise reduction over a wide range of operating conditions as an additional method to passive noise reduction techniques. A 75cc pump has been modified for implementation of active vibration control using the swash plate. One tri-axial acceleration sensor and one angle sensor are installed on the swash plate and a high speed servovalve is used for the swash plate actuation. The multi-frequency two-weight least mean square (LMS) filter synthesizes the servovalve input signal to generate a destructive interference force which minimizes the swash plate vibration. An experimental test setup has been realized using Labview field-programmable gate array (FPGA) via cRIO. Simulation and experimental studies are conducted to investigate the possibility of active vibration control.
16
Bai, Hao. "Machine learning assisted probabilistic prediction of long-term fatigue damage and vibration reduction of wind turbine tower using active damping system". Thesis, Normandie, 2021. http://www.theses.fr/2021NORMIR01.
Abstract (sommario):
Cette thèse est consacrée au développement d'un système d'amortissement actif pour la réduction des vibrations du mât d'éoliennes en cas de vent avec rafales et de vent avec turbulence. La présence de vibrations entraîne souvent soit une déflexion ultime au sommet du mât d'éolienne, soit une défaillance due à la fatigue du matériau près du bas du mât d'éolienne. De plus, étant donné la nature aléatoire de l'état du vent, il est indispensable d'examiner ce problème d'un point de vue probabiliste. Dans ce travail, un cadre probabiliste d'analyse de la fatigue est développé et amélioré en utilisant le réseau de neurones résiduels. Un système d'amortissement utilisant un amortisseur actif, le Twin Rotor Damper, est conçu pour l'éolienne référentielle NREL 5MW. La conception est optimisée par un algorithme évolutionniste avec une méthode de réglage automatique des paramètres basée sur l'exploitation et l'explorationThis dissertation is devoted to the development of an active damping system for vibration reduction of wind turbine tower under gusty wind and turbulent wind. The presence of vibrations often leads to either an ultimate deflection on the top of wind tower or a failure due to the material’s fatigue near the bottom of wind tower. Furthermore, given the random nature of wind conditions, it is indispensable to look at this problem from a probabilistic point of view. In this work, a probabilistic framework of fatigue analysis is developed and improved by using a residual neural network. A damping system employing an active damper, Twin Rotor Damper, is designed for NREL 5MW reference wind turbine. The design is optimized by an evolutionary algorithm with automatic parameter tuning method based on exploitation and exploration
17
Sangili, Vadamalu Raja [Verfasser], Christian [Akademischer Betreuer] Beidl e Stephan [Akademischer Betreuer] Rinderknecht. "Estimation and Control Methods for Active Reduction of Engine-Induced Torsional Vibration in Hybrid Powertrains / Raja Sangili Vadamalu ; Christian Beidl, Stephan Rinderknecht". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/1193177944/34.
18
Vadamalu, Raja [Verfasser], Christian [Akademischer Betreuer] Beidl e Stephan [Akademischer Betreuer] Rinderknecht. "Estimation and Control Methods for Active Reduction of Engine-Induced Torsional Vibration in Hybrid Powertrains / Raja Sangili Vadamalu ; Christian Beidl, Stephan Rinderknecht". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/1193177944/34.
19
Min, Byung-Young. "A physics based investigation of gurney flaps for enhancement of rotorcraft flight characteristics". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33851.
Abstract (sommario):
Helicopters are versatile vehicles that can vertically take off and land, hover, and perform maneuver at very low forward speeds. These characteristics make them unique for a number of civilian and military applications. However, the radial and azimuthal variation of dynamic pressure causes rotors to experience adverse phenomena such as transonic shocks and 3-D dynamic stall. Adverse interactions such as blade vortex interaction and rotor-airframe interaction may also occur. These phenomena contribute to noise and vibrations. Finally, in the event of an engine failure, rotorcraft tends to descend at high vertical velocities causing structural damage and loss of lives.
A variety of techniques have been proposed for reducing the noise and vibrations. These techniques include on-board control (OBC) devices, individual blade control (IBC), and higher harmonic control (HHC). Addition of these devices adds to the weight, cost, and complexity of the rotor system, and reduces the reliability of operations. Simpler OBC concepts will greatly alleviate these drawbacks and enhance the operating envelope of vehicles.
In this study, the use of Gurney flaps is explored as an OBC concept using a physics based approach. A three dimensional Navier-Stokes solver developed by the present investigator is coupled to an existing free wake model of the wake structure. The method is further enhanced for modeling of Blade-Vortex-Interactions (BVI). Loose coupling with an existing comprehensive structural dynamics analysis solver (DYMORE) is implemented for the purpose of rotor trim and modeling of aeroelastic effects.
Results are presented for Gurney flaps as an OBC concept for improvements in autorotation, rotor vibration reduction, and BVI characteristics. As a representative rotor, the HART-II model rotor is used.
It is found that the Gurney flap increases propulsive force in the driving region while the drag force is increased in the driven region. It is concluded that the deployable Gurney flap may improve autorotation characteristics if deployed only over the driving region. Although the net effect of the increased propulsive and drag force results in a faster descent rate when the trim state is maintained for identical thrust, it is found that permanently deployed Gurney flaps with fixed control settings may be useful in flare operations before landing by increasing thrust and lowering the descent rate.
The potential of deployable Gurney flap is demonstrated for rotor vibration reduction. The 4P harmonic of the vertical vibratory load is reduced by 80% or more, while maintaining the trim state. The 4P and 8P harmonic loads are successfully suppressed simultaneously using individually controlled multi-segmented flaps.
Finally, simulations aimed at BVI avoidance using deployable Gurney flaps are also presented.
20
Farah, Philippe-Siad. "Étude de la réduction des vibrations des machines synchrones". Grenoble INPG, 1995. http://www.theses.fr/1995INPG0087.
Abstract (sommario):
Ce mémoire concerne l'étude de la réduction des vibrations des machines synchrones. L'objectif est de proposer une structure optimisée au plan vibratoire, et de mettre au point un dispositif de contrôle actif des vibrations. L'essentiel des informations utiles à la compréhension des mécanismes sources de vibrations est exposé au premier chapitre. Il est montré que le caractère non sinusoïdal de l'induction dans l'entrefer est source de vibrations (électromagnétiques. L'étude expérimentale, sujet du deuxième chapitre sert à définir les éléments de conception d'une machine optimisée au plan vibratoire. Un stator à encoches inclinées et un rotor à aimantations à saturation optimisées ont été retenues. Le troisième chapitre comprend la définition précise d'une maquette optimisée ainsi qu'une étape de validation expérimentale. Il est ici montré que l'usage d'aimants tuile au rotor et le recours à des techniques d'optimisation de structure constituent des outils efficaces pour la réduction des vibrations des machines synchrones. Le dernier chapitre est consacré à la mise en place d'un dispositif de compensation active des vibrations. Cette méthode, fiable et efficace a permis d'obtenir une réduction notable des vibrations, et ce avec des moyens simples et peu coûteux en énergie
21
Karim, Yassine. "Caractérisation robuste de liaisons amortissantes avec dispositifs piezo-électriques pour la réduction de vibrations de structures". Phd thesis, Conservatoire national des arts et metiers - CNAM, 2013. http://tel.archives-ouvertes.fr/tel-00953330.
Abstract (sommario):
L'étude présentée dans ce document a pour objet l'étude de différents modes de réduction de vibrations dans les structures avec liaisons. Le premier mode étudié se base sur la dissipation d'énergie apportée par la déformation d' éléments piézoélectriques connectés à un circuit électrique adapté. Le second mode proposé se base sur la propriété de la liaison boulonnée à changer les fréquences propres d'une structure en fonction du serrage appliqué. Cette propriété est utilisée avec plusieurs lois de contrôle du serrage afin d'éviter les plages de fréquences critiques. Ensuite une étude probabiliste est effectuée pour déterminer la robustesse de la réduction de vibrations par rapport à la variation de certains paramètres du modèle. Cette étude de robustesse est effectuée à travers des méthodes stochastiques non-intrusives, parmi lesquelles une méthode originale proposée. Elle permet une réduction de la taille du modèle stochastique à résoudre, ce qui réduit très considérablement le temps de calcul sans perte de qualité significative.
22
Brinkschulte, Lars, Marina Graf e Marcus Geimer. "Reinforcement learning: a control approach for reducing component damage in mobile machines". Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71113.
Abstract (sommario):
This paper presents an active component damage reducing control approach for driving manoeuvres of a wheel loader. For this purpose, the front and rear axle loads will be manipulated by force pulses induced into the machine chassis via the lifting cylinders of the function drive. The associated control approach is based on the principles of Reinforcement Learning. The essential advantage of such methods against linear control approaches is that no descriptive system properties are required, but the algorithm automatically determines the system behaviour. Due to the high number of necessary training runs, the algorithm is designed and taught using a validated wheel loader simulation model. After over 850 training runs, an optimal strategy for damping the axle loads could not yet be determined. In spite of the unprecedented convergence, initial improvements of the damage values have already been achieved on tracks that deviate from the training track. Some of these results show a 4.9 % lower component damage compared to a machine setting with no damping system. The results and limits of this strategy are discussed due to a comparison with other scientific active vibration damping approaches. Currently, a linear control method (P-PI-controller) has a higher damage reduction potential, but it is expected that further training runs and another learning algorithm could make the reinforcement learning approach even more effective. Coupling the linear control method with the selflearning approach shows the highest potential for the axle damage reduction.
23
Kartha, Satish Chandrashekhar. "Active, Passive and Active/Passive Control Techniques For Reduction of Vibrational Power Flow in Fluid Filled Pipes". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31156.
Abstract (sommario):
The coupled nature of vibrational energy flow in fluid filled piping systems makes its control and subsequent reduction a difficult problem. This work experimentally explores the potential of different active, passive and active/passive control methodologies for control of vibrational power flow in fluid filled pipes. Circumferential modal decomposition and measurements of vibrational power carried by individual wave types were carried out experimentally. The importance of dominant structural bending waves and the need to eliminate them in order to obtain meaningful experimental results has been demonstrated. The effectiveness of the rubber isolator in reducing structural waves has been demonstrated. Improved performance of the quarter wavelength tube and Helmholtz resonator was obtained on implementation of the rubber isolator on the experimental rig. Active control experiments using the side-branch actuator and 1/3 piezoelectric composite yielded significant dB reductions revealing their potential for practical applications. A combined active/passive approach was also implemented as part of this work. This approach yielded promising results, which proved that combining advantages of both active and passive approaches was a feasible alternative.Master of Science
24
Opfer, Holger. "Active cancellation of 3D Tollmien-Schlichting waves in the presence of sound and vibrations". Doctoral thesis, Köln : Dt. Zentrum für Luft- und Raumfahrt e.V., Bibliotheks- und Informationswesen, 2002. http://www.gbv.de/dms/goettingen/370770838.pdf.
25
Boultifat, Chaouki Nacer. "Contrôle acoustique actif du bruit dans une cavité fermée". Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2019. http://www.theses.fr/2019IMTA0134/document.
Abstract (sommario):
Cette thèse porte sur le contrôle acoustique actif (ANC) dans une cavité. L’objectif est d’atténuer l’effet d’une onde sonore perturbatrice en des points ou dans un volume. Ceci est réalisé à l’aide d’un contre-bruit généré, par exemple, par un haut-parleur. Cette étude requiert l’utilisation de modèles dynamiques rendant compte de l’évolution des pressions aux points d’intérêt en fonction des bruits exogènes. Ce modèle peut être obtenu par une identification fréquentielle des réponses point-à-point ou en utilisant le modèle physique sous jacent (équation des ondes). Dans ce dernier cas, la recherche d'un modèle de dimension finie est souvent un préalable à l’étude conceptuelle d'un système d’ANC. Les contributions de cette thèse portent donc sur l’élaboration de différents modèles simplifiés paramétrés par la position pour les systèmes acoustiques et sur la conception de lois de commande pour l’ANC. Le premier volet de la thèse est dédié à l’élaboration de différents modèles simplifiés de système de propagation acoustique au sein d’une cavité. Pour cela, les simplifications envisagées peuvent être de nature spatiale autant que fréquentielle. Nous montrons notamment qu'il est possible, sous certaines conditions, d’approximer le système 3D par un système 1D. Ceci a été mis en évidence expérimentalement sur le banc d’essai LS2NBox. Le second volet porte sur la conception de lois de commande. En premier lieu, les stratégies de commandes couramment utilisées pour l’ANC sont comparées. L'effet dela commande multi-objectif H en différents points voisins des points d'atténuation est analysé. La possibilité d’une annulation parfaitedu bruit en un point est aussi discutéeThis thesis deals with active noise control (ANC) in a cavity. The aim is to mitigate the effect of a disturbing sound wave at some points or in a volume. This is achieved using ananti-noise generated, for example, by a loudspeaker. This study requires the use of dynamic models that report changes in pressure at points of interest in response to exogenous noises. Such models can be obtained by frequency identification of point-to-point responses or by using the underlying physical model (wave equation). In the latter case, the search for a low-complexity model (finite dimensional model) is often a prerequisite for the conceptual study of an active control system. The contributions of this thesis concern the development of different simplified models parameterized by the spatial position for acoustic systems, and the design of control laws for noise attenuation. The first part of the thesis is dedicated to the development of various simplified models of acoustic propagation system within a cavity. For that, the simplifications envisaged can be of spatial nature as much as frequential. We show in particular that it is possible, under certain conditions, to approximate the 3D system by a 1D system. This has been demonstrated experimentally on the prototype system, LS2NBox. The second part of the thesis deals with the design of control laws. First, the control strategies commonly used for ANC are compared. The effect of multi-objective H control at different spatial positions close to the attenuation points is analyzed. The possibility of perfect noise cancellation at one point is also discussed
26
Wei, Jyh-Yang, e 魏志揚. "Vibration reduction and stability analysis of H_infinite active control systems". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/54949820670691377701.
Abstract (sommario):
碩士國立中興大學
土木工程學系
87
In this study,H-infinite control algorithm is applied to reduce the structural responses under seismic loads. Two kinds of controlled outputs, named “displacement controlled output” and “energy controlled output” are presented to design the optimal controller for structures equipped with active tendon systems. The value of parameters alpha and gamma are selected based on the desired control efficiency. The decrease of alpha or increase of gamma will result in larger control forces and better effectiveness in reducing structural responses. Larger has to be selected for stiff structures to achieve the same control effectiveness than flexible structures. The influence of structural modeling error on the accuracy of estimating controlled frequencies and damping ratios was also investigated. It is found that control system with displacement controlled output are primarily affected by the errors of structural fundamental period, whereas the “energy controlled output” systems are more sensitive to the errors of structural original damping ratio. In active control systems, control force execution time delay cannot be avoided. Small delay time not only can render the control ineffective, but also may cause the system instability. The maximum delay time for system instability increased with increasing structural original damping ratios or selecting smaller alpha in which the stability of control system are dominated by lower modes. In the final part of this thesis, an optimal time-delayed H-infinite control algorithm is developed for discrete-time systems. According to the proposed control algorithm, the structural system is assured to remain stable and the control effectiveness is not degraded even with the presence of time delay.
27
Fu, Yu-Ting, e 傅俞婷. "Vibration Reduction of H-infinity Discrete-Time Active Control Systems with Time Delay". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/12101587003517304630.
Abstract (sommario):
碩士國立中興大學
土木工程學系所
98
In recent years, with numerous theoretical development and experimental verifications, both active and semi-active structural control systems have been accepted and implemented to control wind- or earthquake-induced vibration of buildings around the world. In addition, due to flexibility, reliability, and high speed, digital computers have been used for on-line signal processing and calculation of control forces in real-time control. Therefore, it is more logical and more realistic to formulate the control systems in discrete-time fashion prior to their implementation. In this study, an optimal discrete-time control algorithm is developed to reduce the structural seismic responses. Both sampling period and control force execution time delay are considered to derive the optimal state feedback gains. Discrete-time control forces are then calculated from the multiplication of output measurements by the pre-calculated time-invariant delayed gain matrix. Parametric studies of a single-degree-of-freedom (SDOF) system demonstrate the relationships of the delayed gains and the modal properties corresponding to the sampling period used and the intentionally added delay time. To achieve optimal control performance, the strategy to select both control parameters and was investigated extensively. Numerical verification results show that decrease in or increase in yields better control performance with an acceptable magnitude of control force. The selective ranges of and making a controlled system become overdamped or unstable were found. To assure system stability and better performance than LQR control, the upper and lower bounds of and are derived and illustrated graphically. An optimal design flowchart is also proposed.
28
XUE, WEN-ZHENG, e 薛文証. "Study on the reduction of mast vibration and radar interference by active control system". Thesis, 1992. http://ndltd.ncl.edu.tw/handle/66085440420911201966.
29
Thakkar, Dipali. "Helicopter Vibration Reduction Using Single Crystal And Soft Piezoceramic Shear Induced Active Blade Twist". Thesis, 2005. https://etd.iisc.ac.in/handle/2005/1477.
30
Thakkar, Dipali. "Helicopter Vibration Reduction Using Single Crystal And Soft Piezoceramic Shear Induced Active Blade Twist". Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1477.
31
Chen, Lin-Hung, e 陳林宏. "Studies on Active and Passive Constrained Layer Damping for the Vibration Reduction of Cylindrical Shells". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/01040505749418225219.
Abstract (sommario):
博士國立臺灣科技大學
機械工程系
87
This investigation presents vibration response of cylindrical shells with passive and active constrained layer damping (CLD) treatments. The research topics include cylindrical shell with passive constrained layer damping (PCLD), active constrained layer damping (ACLD) and active control (AC). A thin shell theory in conjunction with the Donnell-Mushtari-Vlasov assumptions is employed to yield models for all cases. The assumed-mode method follows to discretize the energy expressions and subsequently yields the equations of motion. As to ACLD, it is formed from PCLD by replacing with the constraining layer, a piezoceramic-based (PZT) self-sensing actuator. The proportional plus the derivative (PD) and the positive position feedback (PPF) control laws are discussed in ACLD and AC cases. To yield the equations of motion of AC case, one simply lets the viscoelastic material (VEM) vanish from the ACLD case. The numerical results emphasize not only the effects of treatment length, of constraining layer (CL) thickness and stiffness, and of VEM thickness for PCLD, but also the comparison of PD and PPF controls, for ACLD and AC. The effect of VEM layer to control force reduction is discussed as well. The results of this research, to the knowledge of the author, are original and provide the engineers useful information about damping effects due to various parameters for PCLD, ACLD and AC treatments and the comparison in between.
32
Sangili, Vadamalu Raja. "Estimation and Control Methods for Active Reduction of Engine-Induced Torsional Vibration in Hybrid Powertrains". Phd thesis, 2018. https://tuprints.ulb.tu-darmstadt.de/9007/7/Vorlage_Dissertation_a5.pdf.
Abstract (sommario):
Automotive powertrain development faces the formidable challenge of reducing fuel consumption, improving driving performance, meeting regulatory demands and satisfying customer demands. Besides powertrain hybridization, continuous optimization of the internal combustion engine (ICE) is actively pursued. Engine refinement using technologies like Miller/Atkinson cycle and Variable Compression Ratio leads to higher peak pressure values in the cylinder from the improved thermodynamic processes. This trend along with rightsizing and downspeeding of the ICE give rise to torque pulsations with higher amplitude and low frequencies. These resulting oscillations cause passenger discomfort and affect component durability.
Measures for passive torsional vibration isolation essentially modify the mechanical characteristics of the powertrain. Approaches employing isolation with the use of tuned mass dampers to reduce such torsional oscillations have also been applied. The increasing complexity and the tuning effort required for the passive mechanisms have increased the interest in adopting active vibration reduction measures. Active torsional vibration reduction uses the onboard electric machine for realizing compensation torque to reduce engine-induced powertrain oscillations.
The objective of this thesis is to develop methods for estimation and control to realize the active reduction of engine-induced torsional oscillations in automotive powertrains. The oscillatory dynamics of the powertrain is governed by the torsional dynamics of the powertrain system and external excitations, in the form of torque pulsations from the ICE. The developed estimation methods study both the torsional powertrain system and the excitations. The dynamic engine torque is estimated using Unknown Input Observer (UIO) techniques. The filtering of the mean value and harmonic components of the dynamic torque is performed using a Linear Parameter Variant (LPV) estimator. The characteristics of the torsional system are identified using Errors-In-Variables (EIV) setup in closed loop operation.
In this work, before initiating the development of control methods, a methodology has been defined to analyze the potential available for active vibration reduction. Besides, the developed vibration reduction controller shall be integrated with the hybrid vehicle energy management controller. A modular architecture has been presented to enable the integration of the controller irrespective of their realization. To characterize the losses associated with the active vibration reduction control, a harmonic characterization of the actuation unit efficiency has been formulated. Beyond the analysis of the losses involved, the harmonic efficiency characterization can be used to develop electric machines specific to vibration reduction of various harmonics. A generic approach has been employed for the development of vibration reduction controllers using measurements for feedback. This approach involves an abstract definition of the active vibration reduction problem. Such an abstract viewpoint offers an opportunity to apply different control methodologies such as adaptive, robust and time-delayed control. The developed controllers have been analyzed with simulations and validated using the experimental setup, demonstrating the desired torsional vibration reduction.
33
Yang, Tzu-Hung, e 楊子弘. "The Study of Using Hybrid Shape Memory Helical Spring in the Vibration Reduction of Semi－Active Suspension Platform". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/98650449250197470740.
Abstract (sommario):
碩士大葉大學
機械與自動化工程學系
97
In this study, the natural frequency and the associated damping capacity of a platform suspended by four helical springs were investigated at different controlled temperatures. The helical spring was fabricated with multiple layers of pyro condensation polymeric sleeve wrapped outside a superelastic NiTi core which has been heat-treated into helical configuration beforehand. The dynamic characteristics of the hybrid shape-memory helical spring was first investigated experimentally. It was found that the first natural frequency of the spring can be decreased to 50% of the frequency at room temperature when the temperature was raised to 90oC. On the other hand, a decrease in the damping capacity of the spring was found accompanying the increase in temperature. Then, the change in the natural frequency of a platform supported by four helical springs was studied. The prediction of the natural frequency of the first few lower modes of the sprung-mass correlated well with the result from measurement. Moreover, we demonstrated the displacement amplitude of vibration for the platform under eccentric loading of imbalance mass was reduced significantly with the control temperature raised to 90℃.
34
Ke, Jian-Cheng, e 柯建呈. "Development of semi-active control for vibration reduction of structural systems using Duffing-like model and magnetorheological damper". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/896d6s.
35
Wrona, Stanisław. "Modelling and control of device casing vibrations for active reduction of acoustic noise". Rozprawa doktorska, 2016. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=37786.
36
Wrona, Stanisław. "Modelling and control of device casing vibrations for active reduction of acoustic noise". Rozprawa doktorska, 2016. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=37786.
37
Hsin-ChangLi e 李信昌. "A Study on the Characteristics and Reduction of Ground Vibrations Generated by Surface and Seismic Loads Acting on Layered Soils". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/02573003768243487832.
Abstract (sommario):
博士國立成功大學
土木工程學系碩博士班
101
This thesis investigates the dynamic characteristics of wave propagation in elastic layered soils. Both the theoretical matrix and finite element methods are employed to simulate the three-dimensional (3D) wave propagation in elastic layered soils with a harmonic point load acting on the surface. Using various multi-layer soils in which harmonic point loads act on the ground surface in the horizontal or vertical directions, these two methods are adopted to solve the steady state solutions of both horizontal and vertical displacement distributions along the direction of wave propagation. In order to confirm the accuracy and reliability of the two assessment methods, it is necessary to compare their results, although few studies have undertaken this task. Moreover, in order to increase efficiency and reduce demands on the computer’s HD capacity, we utilize the theoretical matrix method to further investigate the vibration features of surface wave propagation, especially the irregular hump activity due to Love wave motion. With regard to validating the simulation results, an experimental approach is carried out by measuring the ground vibration from a high speed train. Two typical locations represented the layered and homogeneous soils respectively are selected to perform the tests. A series of test devices were installed to undertake the in situ measurements and analyses of the vibrations induced by a high speed train. The results reveal that low frequency waves might propagate farther than high frequency ones. Besides, SH propagations in layered soils could possibly generate irregular ground vibrations, which may threaten the safety of buildings. However, such irregular vibration phenomena would not occur in homogeneous soils. This study thus also considers how to reduce the ground vibration caused by various external loadings. In addition to a parametric study, a 3D time-domain finite element method is used to analyze the isolation efficiency of open trenches filled with different levels of water. The results indicate that the Y direction wave is difficult to reduce in the water trench, especially for low frequency waves. Meanwhile, field experiments with a full water trench are used to validate this finite element model, and the results show an acceptable level of agreement. Finally, this thesis also considers the safety of high speed trains affected by the ground vibration due to seismic wave propagating in layered soils. Since Taiwan in located in a high risk earthquake zone, we developed a finite element model to simulate the derailment of trains moving on embankments under seismic loading. The results show that the rail irregularities and the resonance between the train and earthquake play an important role in train derailment.