Passive, Adaptive, Active Vibration Control, and Integrated Approaches

Passive vibration control solutions like tuned vibration absorbers are often limited to tackle a single structural resonance or a specific disturbance frequency. Active vibration control systems can overcome these limitations, yet requiring continuously electrical energy for a sufficient performance. Thus, in some cases, a passive vibration control system is still preferable. Yet, the integration of active elements enables adaptation of the system parameters, for instance, the resonance of a tuned vibration absorber. These adaptive or semi-active systems only require external energy for the adaptation, while the compensating forces are generated by the inertia of the absorber’s mass. In this contribution, the fundamentals of active, passive, and adaptive vibration control are briefly summarized and compared regarding their main advantages and design challenges. In the second part, a design of an inertial mass device with integrated piezoelectric actuators is presented. By applying a lever mechanism, the stiffness of the inertial mass device can be tuned even to very low frequencies. The device can be used to implement both adaptive tuned vibration absorbers and active control systems. In the last section of the chapter, the device is used in an experiment for vibration control of a large elastic structure. The setup is used to demonstrate different strategies for the realization of a vibration control system and the integration of different vibration control strategies

Semi-Passive Control Strategy using Piezoceramic Patches in Non Linear Commutation Architecture for Structural-Acoustic Smart Systems

The demands for novel smart damping materials can be summarized in: external power source not required for operation; device not needing to be tuned to a specific frequency; device operation not affected by changes in modal frequency; device suppressing vibration over a number of modes, weight and size minimized; self-contained unit device. This thesis focuses on these points and it shows that the dilemma between active and passive vibration control may be solved with a new approach, implementing a semipassive technique without penalties in terms of robustness and performance. Connecting a shunt circuit to a piezoelectric transducer leads to a simple and low cost vibration controller that is able to efficiently suppress unwanted structural vibrations: this is a way to fulfil the abovementioned demands. The objective of this work is to develop and validate by an experimental campaign a computational tool integrated with finite element Nastran software. An original 4-channel switched shunt control system has been realized using a tachometer device. The control system has been tested first of all on a simple cantilevered beam attaining a max vibrations reduction of 16.2 dB for the first bending mode. Further reference test article consisted of a 10 ply fibreglass laminate plate. A multimodal control has applied within a band range of 700Hz including the first seven modes. A maximum reduction of 16 dB has been found. Further numerical and experimental tests have been planned to extend the ability of the SSC to produce structural-borne sound reduction in acoustic rigid cavities for fluid-structure interaction problems. Numerical sound power radiation of an aluminium plate, controlled by synchronized switch system, compared with the experimental acoustic energy detected in acoustic room, has been planned in the ongoing activities

Evaluation of optimal analysis, design and testing of electromagnetic shunt damper for vibration control of a civil structure

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThe current study is to find out alternative damping to provide satisfactory vibration suppression performance in civil engineering. Accordingly, electromagnetic actuators and electromagnetic dampers (EMDs) are utilised to generate electromagnetic damping. For further discussion on control of vibration serviceability problem in civil structure, the use of a linear voice coil motor (LVCM) as an EMD is implemented to attenuate unwanted vibration. To induce appropriate electromagnetic damping the terminal ends of the LVCMneed to connect with shunt circuits. The basic resistor series circuit and resistor, inductor and capacitor (RLC) oscillating circuit are employed to connect to the LVCM in term of enhancing the EMD damping. However, a design of the electromagnetic shunt damper (EMSD) is required with the generic HØ and H2 robust optimisation techniques to determine shunt circuit components, in which the results of these optimisations were discussed on the previous author study. For extending the EMSD study, the resulting EMSD is experimentally exploited to a six-storey aluminium frame structure. The random and harmonic excitations are selected to input to the structure to examine the performance of the electromagnetic damping. The finding of the experimental test of the EMSD gives satisfactory vibration suppression performance.Engineering and Physical Sciences Research Council (EPSRC

BROADBAND VIBRATION CONTROL THROUGH PERIODIC ARRAYS OF LOCALLY RESONANT INCLUSIONS

openDottorato di ricerca in Ingegneria industriale e dell'informazioneopenZientek, Michal Wladysla

Tunable electromagnetic resonant shunt using pulse-width modulation

This article proposes a novel mean for tuning the natural frequency of an electromagnetic resonant shunt, using a pulse-width modulation (PWM) circuit. It is used to modulate the value of the capacitance of the shunt, and the electrical frequency is shown to be proportional to the command parameter of the PWM, the duty cycle. An easy and efficient strategy to tune the resonant shunt in real time is then proposed, thus obtaining a low powered and always stable vibration control device. The article proposes the theory of PWM, giving a robust method to predict the dynamics of the system. Then, an accurate multi-mode theoretical model of the tunable resonant shunt coupled to an elastic structure is proposed and experimentally validated on an elastic multi-mode structure, in the case of two different control strategies. The first one is a standard resonant shunt with both the electrical frequency and damping optimized to reduce a given resonance peak. The second one is based on a resonant shunt with the electrical damping as low as possible, which creates an antiresonance and a “notch” type mechanical response at the driving frequency. Both strategies are experimentally validated with real time variation and adaptation of the electrical frequency, obtaining an efficient vibration control device, able to reduce by a factor 40 the vibration level

SISO Piezo based circuit development for active structural vibration control

This paper deals with the issue of developing a smart vibration control platform following an innovative model‐based approach. As a matter of fact, obtaining accurate information on system response in pre‐design and design phases may reduce both computational and experimental efforts. From this perspective, a multi‐degree‐of‐freedom (MDOF) electro‐mechanical coupled system has been numerically schematized implementing a finite element formulation: a robust simulation tool integrating finite element model (FEM) features with Simulink® capabilities has been developed. Piezo strain actuation has been modelled with a 2D finite element description: the effects exerted on the structure (converse effect) have been applied as lumped loads at the piezo nodes interface. The sensing (direct effect) has instead been modelled with a 2D piezoelectric constitutive equation and experimentally validated as well. The theoretical study led to the practical development of an integrated circuit which allowed for assessing the vibration control performance. The analysis of critical parameters, description of integrated numerical models, and a discussion of experimental results are addressed step by step to get a global overview of the engineering process. The single mode control has been experimentally validated for a simple benchmark like an aluminum cantilevered beam. The piezo sensor‐actuator collocated couple has been placed according to an optimization process based on the maximum stored electrical energy. Finally, a good level of correlation has been observed between the forecasting model and the experimental application: the frequency analysis allowed for characterizing the piezo couple behavior even far from the resonance peak

New semi-active vibration control with Serial-Stiffness-Switch-System based on vibration energy harvesting

Diese Dissertation untersucht eine neuartige semi-aktive Schwingungsteuerung mit einem seriellen-Steifigkeit-Schalter-System (4S) basierend auf der Speicherung von Schwingungsenergie. Auf Basis der Schwingungsreduktionsanalyse für ein passives und ein semi-aktives Schaltsystem werden Probleme vorhandener Schwingungsteuerungssystemen aufgezeigt und durch das 4S Konzept gelöst. Um seine Leistungsfähigkeit zu untersuchen, wird zunächst 4S im offenen Regelkreis analysiert und die äquivalente Steifigkeit und Eigenfrequenz des Schaltsystems abgeleitet. Es folgt die Analyse für 4S im geschlossenen Regelkreis. Zur Schwingungsreduzierung wird ein Geschwindigkeits-Nulldurchgangs Schaltgesetz verwendet, das auf der Speicherung von Schwingungsenergie basiert. Dies wird unter einer harmonischen Störung numerisch validiert. Anschließend werden Grenzen der Energiespeicherung analysiert. Es folgt eine experimentelle Validierung dieser neuartigen Strategie zur Schwingungssteuerung vorgestellt und ein drehender Prüfstand entwickelt. Der Prüfstand verwendet zwei ringförmig angeordnete Elektromagnetplatten zusammen mit einer Ankerwelle als zwei mechanische Schalter, um die Verbindung oder Trennung von zwei Spiralfedern mit einem Lastträgheitsmoment zu erreichen. Die Speicherung von Schwingungsenergie und die Schwingungsreduktion werden auf diesem Versuchssystem getestet. Neben einer harmonischen Störung wird auch eine Anfangsgeschwindigkeit ungleich Null berücksichtigt. Um in diesem Fall die Schwingungsreduktion zu verbessern, wird ein neues Schaltgesetz vorgeschlagen. Mit Hilfe der Phasenebene wird das transiente und stationäre Ratterverhalten von 4S analysiert. Das Schaltgesetz ermöglicht eine schnelle Umwandlung der anfänglichen kinetischen Energie, die in beiden Federn zu gleichen Teilen gespeichert wird. Dies ist numerisch und experimentell validiert. Zusätzlich wird einer harmonischen Störung an dem neuen Schaltgesetz getestet, das ein besseres Positionierverhalten als das Geschwindigkeits-Nulldurchgangs Schaltgesetz aufweist. Schließlich wird 4S zur Schockisolierung eingesetzt. Die maximale Reduzierung des Überschwingens des Wegs beim Schock und die Reduktion der Restschwingungen nach dem Schock werden numerisch validiert. Darüber hinaus wird auch der Einfluss verschiedener Designparameter von 4S auf das Isolationsverhalten untersucht.This dissertation investigates a novel semi-active vibration control with Serial-Stiffness-Switch-System (4S) based on vibration energy harvesting. On the basis of the vibration reduction performance analysis for a passive and a semi-active switching system, the problem in the present vibration control systems is stated and 4S concept is consequently put forward. In order to examine its performance, 4S in open loop control is analyzed firstly and the equivalent stiffness and natural frequency of the switching system are derived. Following is the analysis for 4S in closed loop control. A velocity zero-crossing switching law based on vibration energy harvesting is used for vibration reduction. This is numerically validated under a harmonic disturbance. Afterwards, vibration energy harvesting limit is analyzed. An experimental validation on this novel vibration control strategy is then presented and a rotational test rig is developed. The test rig uses two ring-arranged electromagnet-plates together with an armature-shaft as two mechanical switches to achieve the connection or disconnection of two spiral springs to or from a primary plate. The vibration energy harvesting and vibration reduction performance of 4S are tested on this experimental system. Apart from a harmonic disturbance, a nonzero initial velocity vibration is also considered. To improve vibration reduction performance in this case, a new switching law is proposed. By means of phase plane, the transient and steady chattering response of 4S are analyzed. The switching law enables a fast transformation of initial vibration energy into potential energy equally stored in two springs. This is numerically and experimentally validated. Additionally, a harmonic disturbance is also exerted on the new switching law. The results show that 4S has a better positioning performance than that for the velocity zero-crossing switching law. Finally, 4S is further applied for shock isolation. The maximum displacement response reduction during shock and the residual vibration suppression after shock are numerically validated. Moreover, the effect of several design parameters of 4S on the shock isolation performance is investigated as well

Piezoelectric Digital Vibration Absorbers for Multimodal Vibration Mitigation of Complex Mechanical Structures

Engineering structures are becoming lighter and more complex to accommodate the ever-increasing demand for performance and to comply with stringent environmental regulations. This trend comes with several challenges, one of which is the increased susceptibility to high-amplitude vibrations. These vibrations can be detrimental to structural performance and lifetime, and may sometimes even threaten safety. Passive and active vibration reduction techniques can provide a solution to this issue. Among the possibilities, piezoelectric damping is an attractive option, due to its compact and lightweight character, its reduced cost and its tunability. This technique uses the ability of a piezoelectric transducer to transform part of its mechanical energy into electrical energy. The converted energy can then be dissipated by connecting a shunt circuit to the transducer. However, the difficulty of realizing such circuits limits the broad applicability of piezoelectric shunting. This doctoral thesis investigates the potential of replacing the electrical circuit comprising classical components such as resistors and inductors by a digital unit and a current source, thereby creating a digital vibration absorber (DVA). Virtually any circuit can be emulated with a digital controller, providing this approach with an extreme versatility for vibration mitigation of complex mechanical structures. In this regard, the DVA is first analyzed in terms of power consumption and stability of the controlled system. Then, effective and easy-to-use tuning approaches for the control of multiple structural modes either with passive electrical circuits or a DVA are proposed, namely a passivity-based tuning of shunt circuits, a modal-based synthesis of electrical networks interconnecting multiple piezoelectric transducers, and a numerical norm-homotopy optimization resulting in an all-equal-peak design. These techniques are eventually applied and adapted to real-life structures with potentially complex dynamics. Specifically, effective vibration mitigation is demonstrated on structures exhibiting nonlinear behaviors and high modal density