RL Shunt Research Articles

Piezoelectric Shunt Damping for a Planar Motor Application under Cryogenic Conditions

For several decades, Moore’s law has driven the semiconductor industry, with computational power and production costs as the main drivers. Such drivers have enabled several technological innovations in the mechatronics and dynamics architecture of photolithography machines, used for semiconductor circuits manufacturing. Among current investigations, the use of superconductive magnets would enable higher accelerating stages and, thus, higher throughput and lower manufacturing costs. However, this involves a complex magnet structure that needs to operate at cryogenic temperatures and mechanical resonances at relatively low frequencies as a result of the thermal architecture of the system. The damping options are also limited due to the very low temperature. This paper explores the use of shunted piezoelectric transducers for damping the internal modes of the magnet mass. A classical resistive and inductive RL shunt is considered. The study was conducted both numerically and experimentally on a demonstrator of a superconductive magnet plate concept, where piezoelectric transducers are incorporated to support the superconducting coils. The study demonstrates the effectiveness of piezoelectric shunts as a damping solution at very low temperatures, with limited impact of the temperature variation on the performance.

Calibration of multiple shunted piezoelectric transducers with correction for residual modes and shunt interactions

Piezoelectric shunt damping can be used for efficient vibration mitigation of a single or multiple vibration modes of a structure. Several analytical tuning expressions have been derived for numerous circuit topologies for a single shunt. However, when multiple shunted piezoelectric transducers are attached to a flexible structure, their individual interactions alongside the spill-over from residual modes affect the calibration accuracy. In this paper, explicit correction terms that represent these effects are presented for multiple shunted piezoelectric transducers targeting a single vibration mode. The correction terms are obtained from the evaluation of effective electromechanical coupling factors, while proper balancing between shunts follows from an assumed proportionality between shunt forces. The proposed correction method is applicable to general shunt architectures, for which tuning is available when targeting a single-degree-of-freedom structure. Its ability to regain nearby optimal damping properties is illustrated numerically for the classic series RL shunt.

Bandgap manipulation of single and multi-frequency smart metastructures with random impedance disorder

Metamaterials and metastructures usually exhibit some form of periodicity that is broken due to randomness in the media, affecting the vibration and elastic wave propagation performance. Disorder in the periodicity caused by the variability in properties or geometry may lead to interesting physical phenomena such as trapping and scattering waves, wave reflection, and energy localisation. While the randomness may be attributed to manufacturing irregularities and quantifying its effect is crucial for ensuring adequate performance of a range of smart systems, and these effects can also be exploited for manipulating the wave properties. Here we investigate a smart metastructure in the form of a beam integrated with piezoelectric transducers coupled to a resonant shunt circuit. The piezoelectric shunt in a periodical arrangement can induce locally resonant bandgaps that can be employed in wave (and vibration) manipulation and control. This paper quantifies the uncertainty associated with electrical circuit components that affect the circuit impedance influencing wave and vibration control features. The smart unimorph meta-beam is formulated by spectral element method based on the Hamiltonian principle, and dispersion curves are estimated using the spectral transfer matrix method that relies on the Bloch-Floquet theorem. The first and second statistical moments are obtained from the stochastic simulations ( realizations) that could be realized efficiently due to the current development of spectral element approach for analysing the disordered system. Further experimental validation and exploration of shunt circuit confirms the need to include the stochastic information on the numerical model used to design the metastructure. Numerical results of the unimorph meta-beam with single and multi-frequency shunt configuration show that the bandgap behaviour is sensitive to the random disorder associated with circuit impedance parameters. Such disorder can be exploited for enhanced functionalities of the meta-beam based on optimal RL shunt circuits for controlling structural vibration response along with wave propagation and attenuation.

A semi-active shunted piezoelectric tuned-mass-damper for multi-modal vibration control of large flexible structures

A semi-active electromechanical Tuned Mass Damper (SATMD), which consists of a combined spring-piezoelectric device connected to an external resistive-inductive electric circuit is presented, aiming to provide robust multi-modal vibration suppression capabilities in large flexible structures. The combined spring-piezoelectric device provides the stiffness for the resonant mass, and also electromechanical energy conversion and coupling. A reduced-ordered mode superposition structural dynamics model coupled with the SATMD device and the RL shunt electric circuit is formulated, to simulate the response of the integrated structural system. The broadband vibration reduction capabilities of the proposed SATMD are numerically and experimentally evaluated and quantified on a down-scaled simplified airframe model. Very good correlation between numerical and measured results is obtained. The results illustrate that a SATMD configuration with an auxiliary mass equal to 1% of the structural mass and combined resistive-inductive impedance, yields substantial simultaneous vibration suppression over the range of 3 low-frequency structural modes, and can be easily retuned to accommodate in-flight changes in structural and loading parameters.

The paradoxical embolism phenomenon in patients with embolic cryptogenic stroke

Patent foramen ovale (PFO) is an important cause of embolic cryptogenic stroke (ECS) in young patients. The main mechanism in this case is paradoxical embolism (PE), the basis for which is a right-to-left (R-L) shunt. Objective: to comparatively characterize patients who have undergone ECS, with and without an R-L shunt, as evidenced by transcranial Doppler with the bubble test (TCD-BT). Patients and methods . In 40 patients with acute ECS, an R-L shunt was sought using TCD-BT, followed by transesophageal echocardiography (TEE). The left atrial volume index (LAVI) was additionally calculated. Brain damage was analyzed by probabilistic mapping of foci according to magnetic resonance imaging. Results and discussion. The mean age of the examined patients was 51.5 (39.5–60.0) years; of them there were 22 women and 18 men. An RL shunt was detected in 24 (60.0%) of patients with cryptogenic embolism that was mainly grades 2 and 3 (41.0 and 35.0%). TEE could visualize PFO (1.0 to 5.5 mm in size) in 16 (40%) patients and atrial septal aneurysm in 3 (7.5%). PFO was not found in 5 patients with positive results of TCD-BT, which may suggest that there is either a pulmonary shunt or a false-negative TEE. The patients with an R-L shunt versus those without an R-L-shunt showed lower LAVIs (23.9 and 26.5 mL/m2) (p=0.016). This fact may additionally confirm the causative role of PFO in the development of stroke, whereas higher LAVIs in the non R-L shunt subgroup should alert to the presence of atrial cardiopathy and initiate an appropriate diagnostic search for latent atrial fibrillation. According to the presence or absence of an R-L shunt, the groups did not significantly differ in gender, age, and clinical characteristics of the stroke. In patients with PFO, a lesion focus was most commonly localized in the middle cerebral artery bed (35.3%), cerebellum (23.5%), and posterior cerebral artery (17.6%). Five (29.0%) patients were ascertained to have several foci of acute stroke. There was a trend towards the larger size of cerebral infarction foci and their specific localization in the vertebrobasilar bed in PE, which determined the high (35.3%) incidence of ataxia with the onset of the disease. Conclusion. PE causes ECS in 60.0% of cases. The distinctive feature of patients with an R-L shunt is lower LAVIs and a trend towards the larger size of cerebral infarction foci and their specific localization in the vertebrobasilar bed.

Passive Damping of Rotationally Periodic Structures with Tuned Piezoelectric Inductive Shunt

This paper considers the piezoelectric resistive and inductive RL shunt damping applied to rotationally periodic structures equipped with an array of regularly spaced piezoelectric patches. A method for simplifying the hardware, by reducing the size of the inductors and eliminating the use of synthetic inductors, is described. The paper compares two different ways of using the piezoelectric array: independent loops and parallel loops. It shows that, if a specific mode with n nodal diameters is targeted, mounting 4n piezoelectric patches in two parallel loops is as efficient as mounting them in 4n independent loops, while considerably reducing the demand on the inductors, L, (by 4n2). The method takes advantage of the mode shapes of rotationally periodic structures. The proposed method is validated numerically and experimentally on a rotationally periodic circular plate (nearly axisymmetric). The proposed technique is aimed at turbomachinery applications.

Sweeping shunted electro-magnetic tuneable vibration absorber: Design and implementation

This paper presents a study on the design and implementation of a time–varying shunted electro–magnetic Tuneable Vibration Absorber for broad–band vibration control of thin structures. A time–varying RL–shunt is used to harmonically vary the stiffness and damping properties of the Tuneable Vibration Absorber so that its mechanical fundamental natural frequency is continuously swept in a given broad frequency band whereas its mechanical damping is continuously adapted to maximize the vibration absorption from the hosting structure where it is mounted. The paper first recalls the tuning and positioning criteria for the case where a classical Tuneable Vibration Absorber is installed on a thin walled cylindrical structure to reduce the response of a resonating flexural mode. It then discusses the design of the time–varying shunt circuit to produce the desired stiffness and damping variations in the electro-magnetic Tuneable Vibration Absorber. Finally, it presents a numerical study on the flexural vibration and interior sound control effects produced when an array of these shunted electro–magnetic Tuneable Vibration Absorbers are mounted on a thin walled cylinder subject to a rain–on–the–roof stochastic excitation. The study shows that the array of proposed systems effectively controls the cylinder flexural response and interior noise over a broad frequency band without need of tuning and thus system identification of the structure. Therefore, the systems can be successfully used also on structures whose physical properties vary in time because of temperature changes or tensioning effects for example.

Smart panel with time-varying shunted piezoelectric patch absorbers for broadband vibration control

This paper presents a simulation study concerning the low and mid frequencies control of flexural vibration in a lightly damped thin plate equipped with five time-varying shunted piezoelectric patch absorbers. The panel is excited by a rain-on-the-roof broad frequency band stationary disturbance. The absorbers are composed by piezoelectric patches connected to time-varying RL shunt circuits. Discrete or continuous variations over time of the shunts are implemented in such a way as to either switch, between given values, or sweep, within certain ranges, the natural frequency and damping factor of the electro-mechanical absorbers to control either the resonant response of targeted flexural modes of the plate with natural frequency comprised between 30Hz and 1kHz or to control the resonant responses of all flexural modes with natural frequencies comprised between 30Hz and 1kHz. The proposed system is firstly presented; then, the vibration control effects produced by a single patch and by the array of five patches implementing the switching and sweeping shunts are investigated. Both time-varying operation modes produce significant vibration control effects, with reductions of the resonance peaks of the target resonances or target frequency band up to 12dB. The piezoelectric patch absorbers with sweeping shunts offer an interesting practical solution since they are operated blindly, thus they do not require a system identification during installation and effectively work without on line tuning also on systems whose response may vary substantially in time.

Dynamic characteristics of the blisk with synchronized switch damping based on negative capacitor

In this paper, we propose a method to suppress the vibration of the integral bladed disk (‘blisk’ for short) in aero-engines using synchronized switch damping based on negative capacitor (SSDNC). Different from the classical piezoelectric shunt damping, SSDNC is a type of nonlinear piezoelectric damping. A multi-harmonic balance method combined with the alternating frequency/time method (MHBM-AFT) is used to predict and further analyze the dynamic characteristics of the electromechanical system, and an arc-length continuation technique is used to improve the convergence of the method. In order to validate the algorithm as well as to recognize the characteristics of the system with SSDNC, a two degree-of-freedom (2-DOF) system with SSDNC is studied at first. The nonlinear complex modal information is calculated and compared with those of the corresponding system with a linear RL shunt circuit. The results indicate that the natural frequencies and modal damping ratio do not change with the modal amplitude, which means that SSDNC has the same modal damping corresponding to different system energy levels. In addition, SSDNC can improve the damping level of all the modes nearly without affecting the natural frequencies of the system. Then, the forced response of the blisk with SSDNC in the frequency domain is calculated and analyzed, including a tuned blisk, which is excited by the traveling wave excitation with a single harmonic and multi-harmonic, and a mistuned blisk, which is excited by traveling wave excitation with a single harmonic and multi-harmonic. We present two advantages of the SSDNC technique when compared with piezoelectric shunt damping. First, SSDNC can suppress the vibration of the blisk under a multi-harmonic wideband the traveling wave, and second, the vibration suppression performance of SSDNC is insensitive to the mistuning of mechanical parameters of the blisk. The results will be of great significance in overcoming the problem of the amplitude magnification induced by the inevitable mistuning of the blisk in aero-engines.

Calibration of piezoelectric RL shunts with explicit residual mode correction

Piezoelectric RL (resistive-inductive) shunts are passive resonant devices used for damping of dominant vibration modes of a flexible structure and their efficiency relies on the precise calibration of the shunt components. In the present paper improved calibration accuracy is attained by an extension of the local piezoelectric transducer displacement by two additional terms, representing the flexibility and inertia contributions from the residual vibration modes not directly addressed by the shunt damping. This results in an augmented dynamic model for the targeted resonant vibration mode, in which the residual contributions, represented by two correction factors, modify both the apparent transducer capacitance and the shunt circuit impedance. Explicit expressions for the correction of the shunt circuit inductance and resistance are presented in a form that is generally applicable to calibration formulae derived on the basis of an assumed single-mode structure, where modal interaction has been neglected. A design procedure is devised and subsequently verified by a numerical example, which demonstrates that effective mitigation can be obtained for an arbitrary vibration mode when the residual mode correction is included in the calibration of the RL shunt.

Parallel Piezoelectric Shunt Damping of Rotationally Periodic Structures

This paper considers the RL shunt damping of rotationally periodic structures with an array of regularly spaced piezoelectric patches. The technique is targeted to the damping of a specific mode withnnodal diameters. For this particular case, one can take advantage of the shape of the targeted mode to organize the piezoelectric patches as a modal filter (in parallel loops) which reduces the demand on the inductors of the tuned inductive shunt. In the case of a perfectly rotationally periodic structure, it is possible to organize 4npiezoelectric transducers (PZT patches) in two parallel loops of 2npatches each. In this way, the demand on the inductors is reduced by4n2as compared to independent loops, which may allow a fully passive integration of the RL shunt in a turbomachinery application. The method is first illustrated experimentally on a circular plate; it is then applied to a prototype of an industrial bladed drum. The influence of blade mistuning is investigated.

Balanced calibration of resonant piezoelectric RL shunts with quasi-static background flexibility correction

Resonant RL shunt circuits constitute a robust approach to piezoelectric damping, where the performance with respect to damping of flexible structures requires a precise calibration of the corresponding circuit components. The balanced calibration procedure of the present paper is based on equal damping of the two modes associated with the resonant vibration form of the structure, when including a quasi-static contribution from non-resonant vibration modes via a single background flexibility parameter. Explicit calibration formulae are presented, and it is demonstrated by a numerical example that the procedure leads to equal modal damping and effective response reduction, even for rather indirect placement of the transducer, provided that the correction for background flexibility is included in the calibration procedure.

Dynamic analysis and ℋ2 optimisation of a piezo-based tuned vibration absorber

In this article, a piezo-based tuned vibration absorber is proposed and theoretically analysed. The proposed device consists of a proof mass, a piezoelectric actuator and a resilient element (spring). An equivalent mechanical model where the piezoelectric element is connected to a general circuit composed of a resistor, an inductor and a capacitor in series ( RLC) is presented to illustrate the coupling of the electrical components with the mechanical systems. Based on the mechanical replacement model, a C or L circuit can be used to realise a piezo-based tuned vibration neutraliser, while with an RC or RL circuit the piezo-based tuned vibration absorber can be considered as a piezo-based tuned mass damper. For the C and L circuits, tuning strategies are derived to adjust the shunt capacitance and inductance to track the disturbance frequency. In the case of RC and RL shunt circuits, an ℋ2 optimisation criterion is used for tuning the piezo-based tuned mass damper. Closed-form expressions for the optimal tuning parameters are provided in this article.

148 Hypoxemia due to right-to-left interatrial shunt with no pulmonary artery hypertension. One centre experience with transcatheter closure including 63 consecutive patients

Hypoxemia related to interatrial right-to-left shunt may have a significant impact on exercise tolerance. We report here one centre experience in transcatheter closure of interatrial RL shunt. From August 1995 to 2009, 63 consecutive patients (37 females and 26 males, mean age 54 ± 24 years), underwent transcatheter closure of interatrial RL shunt because of cyanosis and shortness of breath at exercise. Associated malformations were modified Fontan (n = 4), Ebstein anomaly (n = 1), RV hypoplasia (n = 1), pectus excavatum (n = 2), aortic aneurysm (n = 1). Ten pts had a past history of stroke. A real platypnea-orthodeoxia syndrome was noticed in only 17 pts. The vast majority of patients had cardiac catheterization under local anaesthesia with a sole fluoroscopic control. None of them had pulmonary artery hypertension. Transcatheter closure was performed with a Sideris device (n = 10), a PFO Amplatzer occluder (n = 40), an ASD Amplatzer occluder (n = 8), a Cardioseal device (n = 3), a VSD Amplatzer occluder (n = 2). Device implantation succeeded in all but two (1 Sideris and 1 Cardioseal device). The fluoroscopic time was 12 ± 8 minutes. All patients had better clinical tolerance after closure with an oxygen saturation > 92%. All underwent serial echocardiographic follow-up with bubble study. One month after implantation, no shunt was noticed in all but 6 pts (tiny RL shunt). In 5 of these remaining pts, the 6-month control did not see any residual shunting. Transcatheter closure of interatrial RL shunt responsible of cyanosis is an effective and a safe method. Many devices using a double disk system can be employed and provide excellent results. The classic platypnea-orthodeoxia syndrome is observed in < 25% of this population.

Reduction of Structural Sound Radiation and Vibration Using Shunt Piezoelectric Materials

In this paper, structural sound and vibration control using passive and semi-active shunt piezoelectric damping circuits is presented. A piezoelectric patch with an electrical shunt circuit is bonded to a base structure. When the structure vibrates, the piezoelectric patch strains and transforms the mechanical energy of the structure into electrical energy, which can be effectively dissipated by the shunt circuit. Hence, the shunt circuit acts as a means of extracting mechanical energy from the base structure. First, different types of shunt circuits (such as RL series circuit, RL parallel circuit and RL-C circuit), employed in the passive damping arrangement, are analyzed and compared. By using the impedance method, the general modelling of different shunt piezoelectric damping techniques is presented. The piezoelectric shunt circuit can be seen as additional frequency-dependence damping of the system. One of the primary concerns in shunt damping is to choose the optimal parameters for shunt circuits. In past efforts most of the proposed tuning methods were based on modal properties of the structure. These methods are used to minimize the response of a particular structural mode whilst neglecting the contribution of the other modes. In this study, a design method based on minimization of the sound power of the structure is proposed. The optimal parameters for shunt circuits are obtained using linear quadratic optimal control theory. In general, the passive shunt circuit techniques are an effective method of modal damping. However, the main drawback of the passive shunt circuit is that the shunt piezoelectric is very sensitive to tuning errors and variations in the excitation frequency. To overcome this problem, the pulse-switching shunt circuit, a semi-active continuous switching technique in which a RL shunt circuit is periodically connected to a bonded piezoelectric patch, is introduced as structural damping. The switch law for pulse-switching circuit is discussed based on the energy dissipation technique. Compared with a standard passive piezoelectric shunt circuit, the advantages of the pulse-switching shunt circuit is a small required shunt inductance, a lower sensitivity to environmental changes and easier tuning. Very low external power for the switch controller is required so it may be possible to extract this energy directly from the vibration of the structure itself. Numerical simulations are performed for each of these shunts techniques focusing on minimizing radiated sound power from a clamped plate. It is found that the RL series, RL parallel and pulse-switching circuits have basically the same control performance. The RL–C parallel circuit allows us to reduce the value of the inductance L due to the insertion of an external capacity C. However, the control performance will be reduced simultaneously. The pulse-switching circuit is more stable than RL series circuit with regard to structural stiffness variations. Finally, experimental results are presented using an RL series/parallel shunt circuit, RL-C parallel shunt circuit and pulse-switching circuit. The experimental results have shown that the vibration and noise radiation of a structure can be reduced significantly by using these shunt circuits. The theoretical and experimental techniques presented in this study provide a valuable tool for effective shunt piezoelectric damping.

Robust and high precision control using piezoelectric actuator circuit and integral continuous sliding mode control design

While piezoelectric actuators have been widely used in vibration suppression and high precision controls, their intrinsic nonlinearity such as hysteresis, if not considered in control design, may deteriorate the system performance. In this research, a new methodology is proposed for the high-precision and robust control using piezoelectric actuator with hysteresis compensation. This methodology is featured by the introduction of a resistance/inductance circuit connected to the piezoelectric actuator to form an actuator network and a new integral continuous sliding mode control (ICSMC) algorithm. In addition to the well-known increased passive damping and active control authority, the main advantage of the actuator network in this particular study is that the charge and/or current in the piezoelectric actuator now become independent state variables that can be directly measured and fed back. Not only can this actuator network configuration improve the hysteresis characterization, the control design can also be greatly simplified. With the introduction of the RL shunt circuit, two dynamic subsystems (the mechanical structure and the electrical circuit) are formed. With these two coupled dynamic subsystems as basis, we then develop an ICSMC scheme which combines the advantages of conventional continuous sliding mode control and integral variable structure control. Different from the inverse cancellation of hysteresis behavior which might not be reliable due to the measurement noise, a direct piezoelectric hysteresis compensation is achieved using this control strategy. Detailed analysis and case studies demonstrate that this new methodology can lead to improved precision for both tracking control and vibration attenuation, enhanced control robustness, and smoother control action.