Piezoelectric Control Research Articles

Piezo-electric control of stiffened panels subject to interactive buckling

The paper examines the feasibility of piezo-electric control of stiffened plates carrying axial compression and subject to interaction of local and overall buckling. A simple control strategy involving piezo-electric patches along the tips of the stiffeners carrying equal and opposite electric fields to resist bending of the stiffeners was found to effectively counteract the adverse effects of mode interaction and imperfection-sensitivity. For the dynamic problem, this strategy needed to be supplemented with patches attached to the surfaces of the plate in the middle of the panel to damp out local buckling oscillations. Two panels were considered, these being scaled replicas of each other. This enabled an examination of the scaling laws of response with practical applications in view. The results demonstrate that the structural performance of optimally designed stiffened structures can be enhanced with minimal energy consumption by appropriately designed piezo-electric patch configuration.

Future possibilities for doppler and magnetic field measurements in the extended solar atmosphere: Dissecting the transition region

For the first time, a vacuum ultraviolet (VUV) telescope can be built to rapidly observe the magnetic fields, plasma flows, and heating events in the Sun’s atmosphere. These observations can provide key data for space weather models. The vacuum ultraviolet region allows remote sensing of the upper levels of the solar atmosphere where the magnetic field dominates the physics. A VUV Fabry-Pérot interferometer (FPI) will allow us to observe the magnetic field, flows, and heating events in the mid-transition region (between the chromosphere and corona). Observations of this region are needed to directly probe the magnetic structure and activity at the base of the corona where the magnetic field is approximately force-free, i.e., where gas pressures are very small. This is a key element in developing accurate models of the Sun’s dynamics for space weather. The specific region of interest is the 100 km thick transition region, between the chromosphere and the much hotter corona, which strongly emits at 155 nm from triply ionized carbon (C 3+) at 100,000 K. This is best observed by an imaging interferometer that combines the best attributes of a spectrograph and an imager. We present the latest results from the NASA Marshall Space Flight Center (MSFC) FPI. The major elements of the tunable C iv VUV FPI are the 35 mm MgF 2 etalon plates with a plate finesse of F > 25 at 155 nm, the π -dielectric coatings, a Hansen mechanical mount in a pressurize canister, and the piezoelectric control system. The control system for the etalon is a capacitance-stabilized Hovemere Ltd. standard system. The special Cascade Optical Corporation reflectance coatings are 25 pi-multilayers of high–low refractive layers paired in phase. This C iv interferometer, when flown above Earth’s atmosphere, will obtain narrow-passband images, magnetograms, and Dopplergrams of the transition region in the C iv 155 nm line at a rapid cadence. We recently measured the MSFC VUV FPI using the University of Toronto’s fluoride excimer laser as a proxy for C iv 155 nm. The test demonstrated the first tunable interferometer with the passband required for a VUV filter magnetograph. The measured values have a full-width half-maximum (FWHM) passband of 10 pm, a free-spectral range (FSR) of 61 pm, and a transmittance of 58% at 157 nm. The resulting VUV interferometer finesse is 5.9. With this success, we are developing an instrument suitable for a flight on an orbiting solar observatory. A description of the interferometer for this mission is described.

A frequency stabilization technique for diode lasers based on frequency-shifted beams from an acousto-optic modulator

We present a simple method for diode laser frequency stabilization that makes use of a Doppler-broadened vapor cell absorption signals of two frequency-shifted laser beams. Using second-order-diffracted, double-passed beams from an acousto-optic modulator, we achieve a frequency separation roughly equal to the Doppler half width. The differential transmission signals of the two beams provide an error signal with a very large linear feature, allowing frequency stabilization over a range of greater than 1 GHz by means of standard proportional-integral-derivative servo feedback to the piezoelectric control of the grating in our external cavity diode laser. We have applied this technique to two different diode laser systems, one used to lock to the 410 nm E1 transition in indium and another for locking to the M1/E2 transition in thallium at 1283 nm. In both cases the technique reduces frequency fluctuation to roughly 1 MHz over time scales from 10(-3) to 10(2) s.

Distributed Measurement of Birefringence by P-OTDR Assisted with Piezoelectric Polarization Controller

We propose a new polarization sensitive optical time domain reflectometry (P-OTDR) setup assisted with a piezoelectric polarization controller (PPC). The input state of polarization can be changed by varying the voltage of PPC without any rotatable instrument, and only one optical receiver is used to detect the backward beam. We measure a single mode fibre and get the distribution of birefringence along the SMF.

Generalized Principal-State-of-Polarization Analysis and Matrix Model for Piezoelectric Polarization Controllers

We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the PSP. Our PPC has three components, each made of a jaw and a piezoelectric actuator with the squeezing direction tilted 0°, 45° and 0°, which are driven by a tunable power supply. We demonstrate that all the polarization rotation angles are linear to driving voltages and the PSP of unit 2 is nearly orthogonal to others which are almost equal. Taking some approximate treatments we obtain the matrix model of our PPC with respect to three driving voltages. The average error of our theoretical model is 1.51°, and the polarization response time is < 50 μs, which is promising to realize an open-loop control of polarization.

Piezoelectric control of columns prone to instabilities and nonlinear modal interaction

This paper attempts to unravel the issues of piezoelectric control of structures prone tononlinear static and dynamic instabilities. A simple yet typical example is considered,namely the problem of a simply supported axially compressed imperfect column on anelastic softening foundation. Here the significant nonlinearity arises from the softeningfoundation. The column is so designed as to have coincident critical loads for thefirst two modes of buckling. Piezoelectric actuators/sensors are deemed to beattached to a column in regions of maximum strain at several locations along thelength of the column. The issues involved in (i) enhancing the static bucklingload, (ii) suppression of vibrations as the column is compressed to a load close toits dynamic instability load and (iii) enhancing the dynamic instability load areinvestigated and discussed. It is shown that there is a premium price to pay forenhancing the buckling capacity of the column, be it static or dynamic. The paperconcludes by alluding to the possibility of a failure of patch control if a higher-ordershortwave mode happens to be the governing principal mode of the structure.

Mind Bomb-2 Is an E3 Ligase That Ubiquitinates the N-Methyl-d-aspartate Receptor NR2B Subunit in a Phosphorylation-dependent Manner

The N-methyl-D-aspartate receptor (NMDAR) plays a critical role in synaptic plasticity. Post-translational modifications of NMDARs, such as phosphorylation, alter both the activity and trafficking properties of NMDARs. Ubiquitination is increasingly being recognized as another post-translational modification that can alter synaptic protein composition and function. We identified Mind bomb-2 as an E3 ubiquitin ligase that interacts with and ubiquitinates the NR2B subunit of the NMDAR in mammalian cells. The protein-protein interaction and the ubiquitination of the NR2B subunit were found to be enhanced in a Fyn phosphorylation-dependent manner. Immunocytochemical studies reveal that Mind bomb-2 is localized to postsynaptic sites and colocalizes with the NMDAR in apical dendrites of hippocampal neurons. Furthermore, we show that NMDAR activity is down-regulated by Mind bomb-2. These results identify a specific E3 ubiquitin ligase as a novel interactant with the NR2B subunit and suggest a possible mechanism for the regulation of NMDAR function involving both phosphorylation and ubiquitination.

Self-powered circuit for broadband, multimodal piezoelectric vibration control

Vibration control using piezoelectric actuators has experienced a strong development these last years. Particularly, non-linear techniques have been proven to be low-cost and efficient ways of damping, with self-powering capabilities. This paper deals with one of these methods, the so-called self-powered synchronized switch damping on inductor (SSDI). Its principles rely on switching intermittently the piezoelement on a resonant circuit. Particularly, it is proposed here a new self-powered device that enhances the broadband nature of the self-powered SSDI. The principles of the circuit are to disable the switching event unless a particular condition is fulfilled. Experimental results show that such a circuit significantly improves the multimodal control abilities of the self-powered SSDI techniques without any external power supply requirements.

Thermal protection for a self-sensing piezoelectric control system

Piezoelectric materials exhibit high electromechanical coupling that allows them to bothgenerate an electrical signal when strained and, conversely, to produce a strain under anapplied electric field. This coupling has led to the use of these materials for a variety ofsensing and actuation purposes. One unique application of these materials is their use asself-sensing actuators where both the sensing and actuation functions are performed by asingle patch of material. Since the actuation and sensing voltages both exist simultaneouslyin the piezoelectric material, a specially designed electric circuit, referred to as abridge circuit, is required to realize the concept. Configuration of the material inthis manner is advantageous for control systems due to the enhanced stabilityassociated when collocated control is applied. While certain advantages resultfrom this type of system, precise equilibrium of the bridge circuit is required toachieve stability. This equilibrium is easy to achieve in theory, but difficult inpractice due to the thermal dependence of the piezoelectric material’s dielectricconstant. This study will investigate a novel method of accounting for these changesthrough the use of thermal switches to passively adjust the bridge circuit andmaintain a balanced state. The proposed concept will be theoretically modeled andsimulated in a vibration control application to identify the thermal range forstability with and without the array of switches. It will be shown that, throughthe use of nine thermal switches, the stable operating range can be increased by95 °C while maintaining vibration control performance.

Cascaded dynamic eigenstates of polarization analysis for piezoelectric polarization control

We propose the cascaded dynamic eigenstates (DESs) of polarization to analyze multicomponent polarization control (PC) devices, and achieve the analytical expression of output state of polarization (SOP) as a function of voltage for piezoelectric polarization control (PPC). By measuring the DES at the output port of the device, the prestage DESs will rotate around subsequent ones. Experimental results in PPC confirm the validity of our analysis. The average error of our theoretical output SOP is 1.23 degrees, and the SOP response time is ~10 micros, which is promising to realize a quasi-open-loop high-speed PC.

Piezoelectric control of needle-free transdermal drug delivery

Transdermal drug delivery occurs primarily through hypodermic needle injections, which cause pain, require a trained administrator, and may contribute to the spread of disease. With the growing number of pharmaceutical therapies requiring transdermal delivery, an effective, safe, and simple needle-free alternative is needed. We present and characterize a needle-free jet injector that employs a piezoelectric actuator to accelerate a micron-scale stream of fluid (40–130 μm diameter) to velocities sufficient for skin penetration and drug delivery (50–160 m/s). Existing jet injectors, powered by compressed springs and gases, are not widely used due to painful injections and poor reliability in skin penetration depth and dose. In contrast, our device offers electronic control of the actuator expansion rate, resulting in direct control of jet velocity and thus the potential for more precise injections. We apply a simple fluid-dynamic model to predict the device response to actuator expansion. Further, we demonstrate that injection parameters including expelled volume, jet pressure, and penetration depth in soft materials vary with actuator expansion rate, but are highly coupled. Finally, we discuss how electronically-controlled jet injectors may enable the decoupling of injection parameters such as penetration depth and dose, improving the reliability of needle-free transdermal drug delivery.

Piezoelectric control of composite plate vibration: Effect of electric potential distribution

The paper deals with the vibration analysis of active rectangular plates. The plates considered are composites containing piezoelectric sensor/actuator layers, which operate in a velocity feedback control to achieve transverse vibration suppression. The piezoelectric layers are poled through the thickness and equipped with traditional surface electrodes. In order to satisfy the Maxwell electrostatics equation the widely used simplification of the electric potential distribution in the actuator layer (linear across the thickness) is replaced by a combination of a half-cosine and linear distribution in the transverse direction. The in-plane spatial variation of the potential instead of applying uniform distribution is determined by the solution of the coupled electromechanical governing equations with the natural boundary conditions corresponding to both the flexural and electric potential fields. The analysis is performed for simply supported plates. Two models of the plate are considered. In the first case the displacement field is based on the Kirchhoff hypothesis. For the second the Mindlin plate model is applied. The governing coupled equations describing the active plate behaviour are derived. The influence of the electric potential distribution and also the thickness of piezoelectric layers on the plate dynamics including the natural frequencies modification is numerically investigated and discussed.

Morphing Wing Flight Control Via Postbuckled Precompressed Piezoelectric Actuators

The design, modeling, and testing of a morphing wing for flight control of an uninhabited aerial vehicle is detailed. The design employed a new type of piezoelectric flight control mechanism which relied on axial precompression to magnify control deflections and forces simultaneously. This postbuckled precompressed bending actuator was oriented in the plane of the 12% thick wing and mounted between the end of a tapered D-spar at the 40% chord and a trailing-edge stiffener at the 98% chord. Axial precompression was generated in the piezoelectric elements by an elastic skin which covered the outside of the wing and served as the aerodynamic surface over the aft 70 % of the wing chord. A two-dimensional semi-analytical model based on the Rayleigh-Ritz method of assumed modes was used to predict the static and dynamic trailing-edge deflections as a function of the applied voltage and aerodynamic loading. It was shown that static trailing-edge deflections of ±3.1 deg could be attained statically and dynamically through 34 Hz, with excellent correlation between theory and experiment. Wind tunnel and flight tests showed that the postbuckled precompressed morphing wing increased roll control authority on a 1.4 meter span uninhabited aerial vehicle while reducing weight, slop, part-count, and power consumption.

Finite Element and Simple Lumped Modeling for Flexural Nonlinear Semi-passive Damping

This article deals with the synchronized switch damping on inductor (SSDI) technique, a semi-passive approach that was developed to address the problem of structural vibration damping. This technique takes advantage of original nonlinear processing of the voltage generated by piezoelements. This processing is based on simple commutations. It has the advantage of a very low power requirement as well as simple electronic design. It has the advantages of a large bandwidth as well as being a stand-alone system using vibration as a source of energy. This article proposes a new approach to analyzing the energy flow in a structure damped with this particular technique. A predictive simple lumped model is developed starting from a global energetic analysis of the electromechanical structure. This model is determined using physical and geometrical properties of the electromechanical structure and does not require any experimental measurements. It exhibits very good agreement with finite element model (FEM) simulations and is more than 100 times faster. As this model is fully predictive and requires very low computing time, it is a great tool to design piezoelectric vibration control devices.

Energy transduction analyses of piezoelectric based vibration control of smart structures

Passive vibration shunt control using piezoelectric materials and an electrical network can remove vibration energy from structures. However, the vibration shunt control efficiency relies on the optimization of the vibration energy transfer between a structure and a Lead-Zirconate-Titanate piezoelectric ceramic material. We present an analytical study of a parallel resistor-inductor piezoelectric vibration shunt control on a beam structure using Hamilton's principle and Galerkin's method. The influence of the material's mechanical property on vibration energy transfer between the structure and the Lead-Zirconate-Titanate is discussed. The results of the vibration shunt control with various materials obtained from numerical modeling and experiments are discussed and corroborated.

Enhanced sliding mode motion tracking control of piezoelectric actuators

This paper proposes an enhanced sliding mode motion tracking control methodology for piezoelectric actuators to track desired motion trajectories. The proposed control methodology is established to accommodate parametric uncertainties, nonlinearities including the hysteresis effect, and other un-modelled disturbances, without any form of feed-forward compensation. The fundamental concept in this control strategy relies on the specification of a target performance and the formulation of an enhanced sliding mode control law based on the variable structure control approach. The control methodology ensures the convergence of the position tracking error to zero in the presence of the aforementioned conditions. The stability of the control methodology is proven theoretically and a precise tracking ability is demonstrated in the experimental study. One of the most important advantages of this control methodology is that the approach requires only a knowledge of the estimated system parameters together with their corresponding bounds and the bound of the non-linearities and disturbances in the physical realisation. Being capable of motion tracking, the proposed enhanced sliding mode control methodology is very attractive in the field of micro/nano manipulation through which high-precision piezoelectric actuation control applications can be realised.

Polarity-sensitive position controller for MEMS-based radiation sensing

To successfully deploy many advanced radiation detection schemes, strict control of the system's response to environmental influences is required. For micromechanical radiation detectors in particular, highly sensitive lever-motion sensors––with resolutions in the picometer range––require not only mechanical control, but overall thermal and electrical control in order to maintain a constant system response. In this work, we report on the successful development of a piezo-electric actuator controller that maintains sub-nanometer precision in a noisy environment. The inadequacy of proportional-integral-differential (PID) controllers is demonstrated and explained, and the implementation of a polarity-sensitive controller is detailed. The resulting temporal control scheme can be profitably deployed for other nonlinear systems requiring drift-free control.

Structural Morphing using Piezoelectric Modulation of Joint Friction

An innovative approach to morphing/reconfiguration in flexible structures through friction control in joints is proposed and theoretically explored in this study. The customary method of morphing structures through embedded actuators suffers from the fact that actuators have limited authority and high density, and that the presence of integrated/ embedded actuation devices results in stress concentrations in the substrate. As opposed to using induced elastic strain to cause morphing in elastic structures, the concept presented utilizes piezoelectric control of friction for locking/unlocking in structural joints, and sensors for sensing the structural vibration state in conjunction with naturally occurring or excitation vibration energy, to morph the structure under control. The applications of this concept are not limited to morphing alone but in a broader sense, encompass fields of reconfigurable and fault/damage tolerant structures, having characteristics typically desirable in space structures such as deployable antenna reflectors and space cranes. The proof of this concept is theoretically demonstrated using a single flexible beam (n=1) free at one end and connected to a semi-active revolute joint at the other. Based upon the commanded state of the joint, the beam can switch between a cantilevered and a pinned-free configuration, respectively. The beam is to be reconfigured to a desired azimuth angle in the least time by providing an initial excitation and controlling joint locking and unlocking timing in an optimal manner. The control actions for the timely locking and unlocking of the semi-active joint are determined analytically and verified numerically by using a finite element model simulation using DYMORE. A design of a semi-active joint model capable of providing the desired locking/unlocking action is proposed.

Piezoelectric Control of Edge Debonding in Beams Strengthened with Composite Materials: Part II - Failure Criteria and Optimization

The prevention of the edge debonding failure in RC beams strengthened with externally bonded composite materials by means of optimized piezoelectric control is investigated. The study uses the mathematical model derived and verified in Part I of this paper to assess the structural response of the strengthened beam to the electrical and mechanical loads. The electrical actuation is optimized using two objective functions corresponding to two approaches for the prediction of the debonding failure. The first approach is based on evaluation of the stresses at the critical region near the edge of the bonded strip. The second approach adopts the fracture mechanics concept of the energy release rate, which is evaluated through the generalized J-integral. The formulation of the objective functions and the constraints associated with the restricted operational range of the piezoelectric actuators is presented. A procedure for the construction of the linear or quadratic response and objective functions through a relatively small number of evaluations of the structural model is presented and discussed. A numerical optimization study that focuses on the ability of different combinations of piezoelectric actuators to control, prevent, or delay the edge debonding failure is presented. The main contribution of this study is in providing a systematic approach to optimize the piezoelectric control under different debonding failure criteria and in demonstrating the feasibility of using the piezoelectric system in the full-scale civil engineering structure.

Piezoelectric Control of Edge Debonding in Beams Strengthened with Composite Materials: Part I – Analytical Modeling

The use of piezoelectric materials for the control of the edge stresses and the edge debonding failure in reinforced concrete beams strengthened with externally bonded composite materials is analytically investigated. A mathematical model that incorporates layers of piezoelectric active materials embedded or surfacemounted on the composite strengthening strip is developed. The model is derived using the electromechanical analog for the variational principle of virtual work along with the compatibility conditions, the piezoelectric constitutive laws, and the closed form solutions for the stresses and displacements in the adhesive. The response of a full-scale strengthened beam to mechanical loads and to different schemes of piezoelectric actuation is investigated in terms of the localized stresses near the edge of the bonded composite strip. The results show that in spite of their limited size and actuation capabilities, the piezoelectric actuators can induce shear and vertical normal stresses that are of similar magnitude but opposite sign to the stresses induced by the mechanical load. Thus, it contributes to the prevention of the debonding failure that characterizes the response of the strengthened beam. The original contribution of the study is in addressing the challenge of using piezoelectric smart and active materials in full-scale civil engineering structures, in developing the methodologies and the tools for the quantitative evaluation of the response of such advanced structural member, and in presenting a potential solution to the edge-debonding problem.