Piezo Actuator Research Articles

Asymptotic Stabilization of a Flexible Beam with Attached Mass

A mathematical model of a simply supported Euler-Bernoulli beam with attached spring-mass system is considered. The model is controlled by distributed piezo actuators and lumped force. We address the issue of asymptotic behavior of solutions of this system driven by a linear feedback law. The precompactness of trajectories is established for the operator formulation of the closed-loop dynamics. Sufficient conditions for strong asymptotic stability of the trivial equilibrium are obtained.

Ultrasonically stimulated thermography for crack detection of turbine blades

The hot gas components in a gas turbine have to withstand extreme loads. As failure of turbine blades could have catastrophic consequences, the integrity of the entire engine must always be guaranteed, hence quick and reliable structural health monitoring (SHM) or nondestructive testing techniques (NDT) are essential.In this work, an ultrasonic stimulated thermographic test system was developed to efficiently detect cracks in turbine blades. The used technique is based on the ultrasound excitation with a piezo actuator, where the contact surfaces of the crack are excited and generate frictional heat, which is captured by a thermal imaging camera. A method was developed, where the temperature increase is measured as a function of the electrical energy supply to the actuator. This allows understanding crack topology and the prediction of preloads in the crack. Numerical analysis were conducted for optimising the frequency to be excited for the type of damage experienced by the blade and for understanding the basic physics of the coupling between cracks configuration, local crack velocity and temperature increase. The procedure presented helps to efficiently detect cracks and to optimize the inspection cycles of these components.

Mechanical memory operations in piezotransistive GaN microcantilevers using Au nanoparticle-enhanced photoacoustic excitation

Nonlinear oscillations in micro- and nanoelectromechanical systems have emerged as an exciting research area in recent years due to their promise in realizing low-power, scalable, and reconfigurable mechanical memory and logic devices. Here, we report ultralow-power mechanical memory operations utilizing the nonlinear oscillation regime of GaN microcantilevers with embedded piezotransistive AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers. Switching between the high and low oscillatory states of the nonlinear oscillation regime was demonstrated using a novel phase-controlled opto-mechanical excitation setup, utilizing a piezo actuator and a pulsed laser as the primary and secondary excitation sources, respectively. Laser-based photoacoustic excitation was amplified through plasmonic absorption in Au nanoparticles deposited on a transistor. Thus, the minimum switching energy required for reliable memory operations was reduced to less than a picojoule (pJ), which translates to one of the lowest ever reported, when normalized for mass.

Effect of Bulk Acoustic Wave in Piezo Driven Nanomechanical Motion

Piezo actuation of mechanical resonators is widely adapted because of its simplicity and versatility. Piezo-driven atomic force microscopy cantilevers in air or liquid have a substantial drawback in that they produce spurious resonances that conceal the cantilever resonance peak. Bulk acoustic wave propagation via the piezo-shaker and device substrate causes these undesired peaks. Such restrictions of piezo actuation are rarely reported in nanomechanical resonant sensing. Because most NEMS (nanoelectromechanical systems) experiments are carried out at low pressure to achieve a higher quality factor ) and hence increased sensitivity, spurious resonances are frequently overlooked due to their insignificance. However, this piezo-driven issue may affect NEMS responses at higher pressures (lower Q) and must be addressed carefully. This study reveals spurious resonances from high vacuum to the atmosphere while investigating piezo-driven nanoscale doubly clamped beam responses. At all pressures, spurious peaks with a characteristic frequency span independent of air damping exist, and at higher pressures, they squeeze the mechanical peak. Such squeezing provides a larger derived from the driven phase responses by order of magnitude than the mechanical computed from the measured thermal noise spectra. Interestingly, the characteristic frequency span, not air damping, is revealed to dominate driven .

Research on Gentle Loosening of Solidified Bolted Joints for Complex Capital Goods

The consideration of sustainability is increasingly becoming a focus in research and production. For example, the recycling process for products that are no longer usable should be optimally prepared by separating materials by type as far as possible. In addition, products should be made usable again by repair or replacement if only sub-components fail. In the case of complex capital goods, like aircraft engines, it is mandatory to preserve the product since damage to the joining partners can lead to immense costs. A decisive factor in this context are assembly connections, which have a major influence on the complexity of disassembly. Concerning this matter, detachable connections, like screwed joints, have many advantages for service, repair and recycling compared with permanent fixing solutions. They can reduce assembly time, simplify maintenance processes, and greatly reduce maintenance time and costs. However, during a product’s life cycle, threaded connections can corrode, leading to damage or even failure of the bolted joints. Beyond that, they can solidify and often only be disassembled destructively. In this article, we present an approach to improve the loosening of operational solidified screwed connections. It is well known that vibrations during operation can reduce the preload force of the connections. We exploit this aspect by inducing vibrations through micro impacts to alleviate the loosening torque of the solidified bolted connection. Depending on the direction of the vibration (torsional or axial), that can ensure a gentle and component-friendly disassembly to a greater or lesser extent in contrast to destroying the screw by drilling or shearing and splitting with the risk of damaging the product being maintained. The designed experimental setup with a piezo actuator allows us to investigate the amplitude and frequency of the induced vibrations for the required disassembly force. The results show that our approach enables component-conserving disassembly, as the forces can be significantly reduced.

Design and Control of a Rotary Piezo Actuator

Design and Control of a Rotary Piezo Actuator

Development of highspeed and super-resolution microscopy

Live cell imaging is a powerful tool to understand the molecular mechanisms of a wide range of cellular processes. However, it is difficult to detect very small objects such as transport vesicles (< 100 nm in diameter) by light microscopy because of the diffraction limit of light. To overcome this problem, several superresolution technologies such as STED, SIM, and STORM/PALM has been developed so far, but the time resolution of these methods is not sufficient to track the small vesicles undergoing fast movement inside the cell. In the present study, we developed a highspeed, superresolution, and multicolor optical microscope, which we call SCLIM2 (the second generation superresolution confocal live cell imaging microscopy). SCLIM2 consists of an inverted microscope equipped with piezo actuator for objective lens, a spinningdisk confocal scanner, an emission splitter unit, cooled image intensifiers, and ultrafast CMOS cameras (1000 frames/s). Using this system, we acquired fluorescence images of specimens at a single photon precision. We also developed a mathematical method for 4D (xyz and time) image reconstruction and novel deconvolution algorism based on the probability calculation. The resulting lateral resolution was less than 71 nm. We then applied SCLIM2 to observe a variety of membrane traffic events in live cells. We succeeded in visualizing a large number of small vesicles (< 100 nm in diameter) were moving around the Golgi apparatus.

Characterisation of lateral offsets in clinch points with computed tomography and transient dynamic analysis

Clinching is a very cost-efficient method for joining two or more sheets made of identical or different materials. However, the current evaluation methods cannot confirm the critical geometrical features of joints such as neck thickness, undercut, and bottom thickness. Furthermore, the effects caused by joining process such as elastic deformation and crack-closure are significant for the joining quality, but often earn insufficient attention. Therefore, computed tomography (CT) and Transient Dynamic Analysis (TDA) as an ultrasonic testing and evaluation procedure are combined to overcome the obstacles mentioned above. In order to have a well-defined and reproducible typical geometrical error in clinching, specimens with a pre-specified lateral offset of the punch with 0.1 mm, 0.2 mm are as well as with no lateral offset are investigated using CT. The specimens are treated with conductive copper varnish in varying intensities to support the two sheets' distinguishability in the CT measurement. The subsequently extracted surfaces from CT-scan data are used to create three-dimensional models for a numerical Transient Dynamic Analysis. Hereby, a harmonic force is applied to one sheet and the transferred energy is determined at the opposite side of the clinch point on the other sheet. The transmitted energy can be used as a quantitative measure for the joining quality. This setup is simulated by means of Finite-Element-Method and the specimens are investigated experimentally using a piezo actuator and a piezo sensor. The novelty of the results presented here is the completely non-destructive investigation of joint specimen by CT of similar materials with a contrast given foil in between the sheets and the subsequent TDA, which can easily detect difference between the specimens by evaluation of the energy dissipation of the joints.

The electromechanical damping of piezo actuator resonances: Theory and practice

Piezo actuators have very desirable properties, such as a high stiffness and extreme position resolution, but suffer from electromechanical resonances that complicate their use in high-speed applications. These resonances can be minimized by using resistive or resistive-inductive damping.In this paper a comprehensive theory is presented which describes these piezo resonances, and the mechanism by which these resonances are minimized by adding electrical damping components. The theory is based on a purely electronic model, and uses an electrical-mechanical transformation to describe actual piezo displacements. Using this theory, an ‘optimal’ value of damping resistance is readily identified. This optimal resistance causes maximal damping of the primary resonance of the piezo. It is shown that damping with a combination of a resistor and an inductor can theoretically be even better.An optical displacement setup was developed, and frequency- and time-domain measurements were performed that validate the theory. The mechanical damping of the piezo actuator needs to be included in the theory to obtain a good fit with the electrical and mechanical behavior of an actual piezo actuator.

Deformations of a piezo‐actuated bearing ring in journal bearings

AbstractAn elastically deformable bearing ring is investigated. The piezo‐actuated shaping of the elastic bearing ring as well as the journal motion are coupled and determine the height of the lubrication gap which takes a crucial part in the theory of hydrodynamic lubrication. The influence of the active‐dynamic shaping of the bearing ring on the rotor dynamic behaviour has been investigated in [1], especially for a two‐lobe journal bearing. The present investigations are aiming at the active‐static shaping of a bearing ring, i.e. a finite number of piezo actuators is used to cause deformations of the bearing ring. Moreover, the realisation of different shapes by the introduced piezo actuators is examined, whereas the desired shapes are not necessarily limited to two‐lobe geometries.

Asymptotic stabilization of a flexible beam with an attached mass

UDC 517.977 A mathematical model of a simply supported Euler – Bernoulli beam with attached spring-mass system is considered. The model is controlled by distributed piezo actuators and a lumped force. We address the issue of asymptotic behavior of solutions of this system driven by a linear feedback law. The precompactness of trajectories is established for the operator formulation of the closed-loop dynamics. Sufficient conditions for strong asymptotic stability of the trivial equilibrium are obtained.

A new method for spatial mode shifting of stabilized optical cavities for the generation of dual-color X-rays

We propose an innovative method to shift the transversal position of the focal point of an optical cavity keeping it actively frequency stabilized. Our cavity is a 4 mirrors bow-tie cavity and the spatial shift of the resonant mode is obtained by properly rotating the two curved mirrors by piezo actuators. This method allows us to move the transversal position of the cavity focal point of 135µm in a time of 50ms, keeping the resonance condition of the cavity by means of the Pound–Drever–Hall technique. We propose to use this technique for the generation of 2-color X-rays via Inverse Compton Scattering (ICS). This technique exploits the large average power stored in the high finesse cavity by shifting the laser beam with respect to the electron beam trajectory, hence controlling the spatial superposition of the electron and photon beams in the interaction region. Arranging two cavities assembled one on top of the other, with different collision angle with the electron beam, allows the generation of X-ray bursts of different energies just by swiftly moving the two cavities, switching the two focal points onto the electron beam trajectory, thus activating in sequence two different ICS spectral lines.

Design and analysis of new ultra compact decoupled XYZ[formula omitted] stage to achieve large-scale high precision motion

A new high precision ultra-compact decoupled XYZθ motion stage based on flexure hinges is designed and analyzed. The stage mainly consists of three components including serial–parallel dual-stage amplifier, Z-shape motion steering mechanism and motion decoupled mechanism. Compared with the existing stages, the proposed high precision motion stage has many advantages such as extremely compact structure, large output decoupling motion and XYZθ four axes output displacement. The function of serial–parallel dual-stage amplifier is to amplify the travel range of nano positioning piezo actuator (PZT) by connecting two parallel bridge type mechanism. The Z-shape mechanism can change the direction of motion transmission to make the stage more compact and form movement in XYZθ four directions. The decouple mechanism can reduce the implicative movement of different piezo actuators. Then, kinetostatic analysis of this new XYZθ stage is conducted to analyze the stage. Finally, the finite-element analysis (FEA) and prototype experiments are implemented to verify the design objectives.

Designing control algorithm and experimental validation for piezo stepping actuator

Piezo-stepping actuator is one device that produces large displacement while some voltage is applied to it or vice-versa by micro-meter accuracy and nanometer resolution. The displacement in stepper actuators happens with steps. A linear stepping movement of the base of the actuator is proposed in this paper. A linear stepping motion of the piezo actuators is achieved with four sets of push–pull actuators and four sets of lock release actuators. The designed stepper actuator produces linear displacements. The design and control of the stepper actuators are explained in the paper. A trapezoidal signal is being generated from the triangular wave moreover this is implemented as the input for the smooth functioning of a stepping actuator. Control operation of push–pull and lock-release actuators was performed and for various input displacements the experimental displacements of actuators were achieved and the results were plotted. Control operation of Push-pull and lock release assembly was conducted for varying input displacement and corresponding experimental displacement is measured and also the results were plotted. The actuator assembly was proficient in driving the linear guideways.

Observation of Stage Position in a 2-Axis Nano-positioner Using Hybrid Kalman Filter

This paper presents a novel method for observation of the stage position in a 2D Nano-positioning system based on a hybrid Kalman filter. In the proposed method, there is no need to measure the stage position directly using complex and costly capacity sensors. Instead, by using traditional piezo actuators equipped with strain gauge sensors, the deflection of the magnification system at the position of actuators is measured. Then, by employing a powerful estimation algorithm named as Kalman filter, the displacements of the stage are observed. The designed hybrid Kalman filter uses dynamical equations of motion in the prediction step. The piezo actuators deflections are measured and exploited to correct the predicted values for the system state variables. In order to simulate realistic conditions, a relatively exact COMSOL model has been developed for the nano-positioner where noise has been added to the piezo displacements obtained by simulating this model and these noisy data are used as measurements in the Kalman filter algorithm. The designed hybrid Kalman filter is examined for three different updating time steps. The results show that the designed Kalman filter appropriately estimates the stage displacements, and its accuracy is improved when the filter time step reduces.

Structural scheme of electromagnetoelastic actuator for nano biomechanics

The structural scheme of an electromagnetoelastic actuator for nano biomechanics is found. The structural scheme of an electromagnetoelastic actuator has difference in the visibility of energy conversion from Cady and Mason electrical equivalent circuits of a piezo vibrator. The electromagnetoelasticity equation and the differential equation of the actuator are solved to construct the structural scheme of the actuator. The structural scheme of the piezo actuator is obtained by using the reverse and direct piezoelectric effects. The transfer functions of an electromagnetoelastic actuator are written

PMMA Application in Piezo Actuation Jet for Dissipating Heat of Electronic Devices

The present study utilizes an acrylic (PMMA) plate with circular piezoelectric ceramics (PC) as an actuator to design and investigate five different types of piezo actuation jets (PAJs) with operating conditions. The results show that the heat transfer coefficient of a device of PAJ is 200% greater than that of a traditional rotary fan when PAJ is placed at the proper distance of 10 to 20 mm from the heat source, avoiding the suck back of surrounding fluids. The cooling effect of these five PAJs was calculated by employing the thermal analysis method and the convection thermal resistance of the optimal PAJ can be reduced by about 36%, while the voltage frequency, wind speed, and noise were all positively correlated. When the supplied piezoelectric frequency is 300 Hz, the decibel level of the noise is similar to that of a commercial rotary fan. The piezoelectric sheets had one of two diameters of 31 mm or 41 mm depending on the size of the tested PAJs. The power consumption of a single PAJ was less than 10% of that of a rotary fan. Among the five types of PAJ, the optimal one has the characteristics that the diameter of the piezoelectric sheet is 41 mm, the piezoelectric spacing is 2 mm, and the length of the opening is 4 mm. Furthermore, the optimal operating conditions are a voltage frequency of 300 Hz and a placement distance of 20 mm in the present study.

Numerical feasibility study for transverse vibration control of rotating shaft with a neural network-based tracking algorithm

Rotary elements have been applied to a variety of mechanical systems such as pumped-storage hydroelectricity and nuclear power plant. Due to their vibration problems occurred by misalignment, bent, and unbalance, a sharp decline efficiency of system and malfunction can be caused and furthermore, the rotor may be damaged. In order to control the rotor vibration actively, active vibration control using the magnetic bearing and piezo actuator is being vigorously studied to improve operating conditions of rotary devices. This research accomplished numerical simulations of active vibration control for an unbalanced rotor system using the active bearing system applying piezo actuators. Overall rotor system is modeled using energy method and an active bearing model with two actuators placed in both x- and y-direction is developed using lumped parameter method. For implementing active control scheme through the active bearing system, a signal tracking algorithm based on neural network is developed and utilized to the rotor system. The active bearing system shows good performance on transverse vibration reduction for rotating systems.

Computational-Experimental Design Framework for Laser Path Length Controller.

The application areas of piezoelectric materials are expanding rapidly in the form of piezo harvesters, sensors and actuators. A path length controller is a high-precision piezoelectric actuator used in laser oscillators, especially in ring laser gyroscopes. A path length controller alters the position of a mirror nanometrically by means of a control voltage to stabilize the route that a laser beam travels in an integral multiple of laser wavelength. The design and verification of a path length controller performance requires long (up to 3 months), expensive and precise production steps to be successfully terminated. In this study, a combined computational–experimental design framework was developed to control, optimize and verify the performance of the path length controller, without the need for ring laser gyroscope assembly. A novel framework was structured such that the piezoelectric performance characteristics were calculated using finite element analysis. Then, a stand-alone measurement system was developed to verify the finite element analysis results before system integration. The final performance of the novel framework was verified by a direct measurement method called mode-scanning, which is founded on laser interferometry. The study is concluded with the explanation of measurement errors and finite element correlations.

Determination of the Natural Frequency of the Model Spindle System with Active Regulation of the Initial Tension of the Bearings

This article presents a test stand with a model high-speed spindle equipped with a system of active control of the preload of the bearings. This preload was changed by means of three piezo actuators. The work presents the results of tests during which the commercial Abacus measuring equipment from Data Physics was used. Its application has shown that the spindle system with angular contact ball bearings is responsive to changes in the preload value of these bearings. The change preload resulted in a change in the value of the resonant frequency of the system and its amplitude. This article presents the dependence between the variable value of the preload of the bearings and the corresponding values of the resonance frequency and amplitude of the spindle system. The use of the Abacus measuring equipment for testing allowed for the preparation of a model showing the dynamic behavior of the spindle. The system was forced by a signal with known parameters, and the response to this excitation was recorded at eleven points located on the surface of the entire spindle.