Vibration Transducer Research Articles

Orthogonalization of the measuring basis of triaxial vibration transducers by the method of successive approximations

The transversal sensitivity of tri-axial vibration transducers, which have found vast application in various vibration measuring and material testing systems, decreases the accuracy of measurements. We present a solution to the problem of eliminating the error attributed to the presence of the transverse sensitivity. The measurement error depends on many factors including the ratio of vibration components along the sensitivity axes, the width of the vibration spectrum, and the presence of intrinsic resonances of the vibration transducers in the main and transverse directions. The developed method provides almost complete compensation of the error. Analysis of the components of sensitivity vectors along the measuring directions showed that the transversal sensitivity vectors are in fact the parasitic penetrations from other directions, and can be decomposed along the measuring axes. To orthogonalize the sensitivity vectors during calibration, the sensitivity vectors should be rotated until they coincide with the orthogonal directions. A measuring basis with zero transverse sensitivities is thus obtained, and the sensitivity matrix is reduced to a diagonal form. With this approach the fundamentals and practical algorithm using successive approximations of triaxial transducer calibration with orthogonalization are outlined. Each orthogonalization step is illustrated by the current sensitivity matrix, showing the progress of transversal sensitivity reduction. The results of the developed tri-axial transducer coupled to a special preamplifier-converter with transversal sensitivities reduced to nearly zero values using the developed method are presented. Since calibration is carried out without dismantling of a vibration transducer, it can be carried out not only during its manufacture, but also during verification upon operation, which increases the service life. The use of the described technique not only improves the metrological parameters of vibration transducers, but also provides a significant reduction of the requirements for the accuracy of manufacturing their measuring system, thus reducing the production costs. The presented method is promising for the developing new precise multi-axis vibration transducers and measuring systems on their base.

Research on vibration characteristics of the longitudinal-radial composite piezoelectric ultrasonic transducer

The transducer with high power capacity and extensive radiating area is required in some industrial processes like ultrasonic sonochemistry, ultrasonic cleaning and ultrasonic defoaming and so on. In order to achieve the desired effects, the longitudinal-radial composite piezoelectric ultrasonic transducer is proposed in this paper. The transducer is composed of a longitudinal sandwich piezoelectric transducer, a stepped ultrasonic horn and a metal sphere. The longitudinal vibrations of the sandwich piezoelectric transducer and the stepped ultrasonic horn excite the radial vibration of the metal sphere so that the longitudinal-radial coupled vibration of the transducer is achieved. The equivalent circuits for a sphere in radial vibration and for the entire system in longitudinal-radial coupled vibration have been developed. To validate the proposed equivalent circuits, the vibration characteristics of the transducer are investigated using the equivalent circuit method, numerical method, and experiment. The resonance frequencies obtained from the equivalent circuit method, numerical method and experiment are 29992 Hz, 29990 Hz and 30590 Hz, respectively, and the simulated and experimental results indicate that the frequencies correspond to the designed longitudinal-radial coupled resonance mode of the transducer. The measured frequency and displacement distribution showed good agreement with the analytical and numerical calculation results.

Investigation of the Vibration Transmission Characteristics of the Aero-Engine Casing System by Rotating Force Exciter

This work aims to study the dynamic characteristics of an entire aero-engine casing by experiments using a new type of rotating exciter. New vibration sensor layout rules are proposed according to experimental results and vibration transmission characteristics. The vibration response of the aero-engine casing is carried out, and the vibration response of different casing measuring points is also studied. The finite element model of the engine casing’s structure is established to obtain the natural frequency of the whole aero-engine casing, which agrees well with the experimental measurement. We find that the vibration acceleration transmission value of the radial measuring point of bearing No. 1, but not the fan sensor, is more suitable for detecting the running state of the fan rotor. In addition, the sensor in the intermediate casing can detect the vibration of the high-pressure rotor. Bolt loosening of the flange has little effect on the vibration transmission characteristics of the casing. This work aims to provide experimental data of whole aero-engine vibration characteristics with a new rotating exciter for the vibration test, which can help optimize the location of the vibration transducer for the engine and the assembly technology design for the whole engine structure.

High-Frequency Ultrasonic Radiator Power Increase by Means of Summation of Vibrations of Symmetrically Arranged Langevin Transducers

The article focuses on the research of processes of summation of ultrasonic vibrations of individual Langevin transducers symmetrically arranged on a common summator. This design could be used to solve the problem of increasing the power of a high-frequency ultrasonic radiator by means of the summation of the vibrations of individual Langevin transducers. The results of the presented theoretical and experimental investigations supported the possibility of summation of symmetrical diametrical vibrations when they are transformed into longitudinal vibrations. As a result, a new design scheme for high-frequency radiator construction was developed that provides symmetry and uniformity of vibration amplitude distribution of piezoceramic elements. This made it possible to eliminate the damage of piezoceramic elements. The article establishes that an acoustic power (continuous mode) of 1450 W at an efficiency of 78% is achieved when the vibrations from 9 to 11 of symmetrically arranged Langevin transducers at a resonant frequency of 30.05 kHz with an amplitude of 26 µm are summed. The use of this ultrasonic high-frequency radiator with increased power will provide intensification of processes in various areas of industry.

Effect of Driver Mass Loading on Bone Conduction Transfer in an Implantable Bone Conduction Transducer

This paper focuses on transducers, which are the most important components of bone conduction implants. To improve vibration magnitude, we develop a coil vibration transducer in which the driver mass loading is reduced by about 3.25-fold compared to magnet vibration transducers. We use finite element analysis to derive and implement the maximum Lorentz force and frequency characteristics. We compare the effect of driver mass loading on the vibration magnitude to that of an older transducer. The new transducer vibrates about 4.4-fold more strongly. To compare force magnitude between the two transducers, output force is measured using an artificial mastoid. The force imparted by the new transducer is higher than that of the older transducer only below 1.4 kHz, and tends to be lower at high frequencies. Nevertheless, the improved force in the low-frequency region will improve conductive hearing loss.

ЭЛЕКТРОМЕХАНИЧЕСКИЙ ВИБРАЦИОННЫЙ ПРЕОБРАЗОВАТЕЛЬ С ЗАМКНУТЫМ СПИРАЛЬНЫМ ВТОРИЧНЫМ ЭЛЕМЕНТОМ И УЛУЧШЕННЫМИ ХАРАКТЕРИСТИКАМИ

Relevance The development of new designs of electromechanical vibration transducers (EMVT) is an urgent task and is caused by the need to create devices that meet to one degree or another many, often contradictory requirements for accuracy and measurement limits, frequency range, sensitivity, overall dimensions, weight, cost, performance characteristics, etc. An important prerequisite for solving the set tasks is the study and development of new promising structural elements of electromechanical converters, materials, components, special production processes. The rapid development of science and technology causes a great variety and complexity of automatic control systems. Invariant, self-adjusting and other complex information-measuring and control systems are created, to which increased requirements are imposed. The modern development of automated monitoring and control systems for various technological and physical processes is characterized by the widespread use of primary means of collecting and processing information. At the same time, electromechanical vibration transducers EMVPsensors of vibration parameters are a link in any information-visual or control system and practically determine its metrological characteristics. Losses in the accuracy and reliability of the final result associated with unsuccessful use of the sensor cannot be restored by the most advanced information conversion system. The range of industrially produced vibration sensors is limited, and their effective operation and evaluation of experimental results is very difficult. The lack of clear recommendations for choosing one type of sensor or another, sound methods of engineering calculations and experimental studies, and analysis of limiting operational and technological capabilities has led to the fact that many types and designs of sensors turned out to be unviable. A large number of publications related to the design of new designs of vibration sensors for various purposes and the improvement of already known ones allows us to judge the continued interest of developers in this class of devices, especially with the development of technical robots and flexible modules. The lack of fundamental theory and engineering methods for calculating the static characteristics of electric motors in the mode of both a sensor and a motor with a spiral electrically conductive element limits the possibility of their rational design for information-measuring and control systems. Therefore, the tasks of researching and creating highly efficient EMVPs with a spiral secondary element that most fully satisfy the special requirements of control systems are relevant. Aim of research To investigate a vibration transducer (EMVT) with a closed spiral secondary element in the mode of generating low-frequency vibrations and improving mechanical data due to the execution of longitudinal slits with a bevel in a spiral electrically conductive spring. Research methods Literary review and patent study, methods of mathematical modeling and experimental studies of vibration oscillations. Results For the first time, a method and methodology have been developed for the design of electromechanical vibration converters with a spiral secondary element with theoretical and experimental confirmation of the main obtained positions. A full-scale sample with theoretical provisions was developed, a patent of the Russian Federation was obtained, the possibility of using a structural solution in household devices (tablets, laptops, electronic watches, nanorabototechnics, vascular medicine and cardiology, information transmission as GPS u GSM elements, etc.) was shown.

Physical model for experimental study of an electromechanical vibration transducer with a spiral closed secondary element

For the first time, a physical model in the form of an electromagnetic gun for the study of electromechanical vibration transducers with a spiral secondary element is proposed. The use of a physical model makes it possible to develop a research stand for determining the mechanical characteristics of an electromechanical vibration transducer (EMVT) with a spiral secondary element based on strain gauges and to obtain the necessary experimental data for further scientific work. Keywords electromagnetic gun, short-circuited coil, vibration transducer, strain gauges, mathematical model

Large-scale piezoelectric ultrasonic transducers with tubular near-period phononic crystal point defect structure

<sec>The coupling vibration of large-scale piezoelectric ultrasonic transducer will make the average value of the longitudinal displacement amplitude of its radiation surface small and the amplitude distribution uneven, which seriously affects the performance and reliability of the system. In order to improve the performance of large-scale ultrasonic vibration system, a two-dimensional hole/slot near-periodic phononic crystal structure is used to suppress the transverse vibration, but the structure will in turn affect the mechanical strength of the transducer while achieving the suppression of the transverse vibration. The working bandwidth and other performance parameters have adverse effects. Based on this, a new idea of optimizing the large-scale sandwich longitudinal vibration piezoelectric ceramic transducer by using the tubular near-periodic phononic crystal point defect structure is proposed. This method can not only use the point defect mode of the constructed solid/gas two-dimensional near-periodic phononic crystal structure to obtain extremely low energy loss, but also effectively improve the longitudinal displacement amplitude and amplitude distribution uniformity of the radiation surface of the system. The double annular holes in the pipe string structure can also be used to enhance the multiple scattering of sound waves, so that the transducer can also produce a band gap under the low conditions of the pipe string, effectively suppressing the transverse vibration, at the same time, significantly broadening the working bandwidth of the transducer system, enhancing the stability and mechanical strength of the system, and reducing the processing cost. Simulation results and experimental processing test results also prove the effectiveness of the optimization.</sec><sec>In order to find the best parameters for the performance of the large-scale longitudinal vibration piezoelectric ultrasonic transducer, in the paper the finite element analysis software is used to study the influence of the inner radius <i>r</i><sub>1</sub> of the pipe string, the width <i>r</i> of the pipe string ring, the radius <i>R</i> of the outermost air cylinder hole, and the height <i>h</i><sub>2</sub> of the pipe string at the longitudinal resonance frequency of the transducer performance, the longitudinal displacement amplitude distribution uniformity of the radiation surface, and the average longitudinal displacement amplitude. In the research is finally found the range of parameters that can make the performance of the transducer reach a relatively ideal state. The simulation results show that the tubular near-periodic phononic crystal point defect structure can improve the performance of large-scale longitudinal vibration piezoelectric ultrasonic transducer.</sec>

Arbitrary variable thickness annular piezoelectric ultrasonic transducer based on transfer matrix method

The variable thickness annular radial piezoelectric ultrasonic transducer can realize impedance transformation and energy concentration, has the advantages of large radiation area and full directivity, and is widely used in power ultrasound, underwater acoustic and other fields. Because solving complex variable thickness metal ring radial vibration wave equation is more difficult, in this paper, the radial vibration of metal rings with variable thickness is transformed into the superposition of the radial vibrations of N metal rings with equal thickness by using the transfer matrix method. The equivalent circuit diagram, the resonance frequency equation and the expression of the displacement amplification coefficient of the radial vibration of the metal thin ring with arbitrary thickness are obtained. The relationship between the displacement amplification coefficient and the geometric size of the cone, power function, exponential and catenary metal rings is analyzed. On this basis, the equivalent circuit and resonance frequency equation of radial vibration of piezoelectric ultrasonic transducer which is composed of a metal ring with variable thickness and a piezoelectric ring with equal thickness are derived. In order to verify the correctness of the theoretical results, the finite element software is used in simulation, and the numerical solutions of the first and second order resonance frequency and displacement amplification coefficients are in good agreement with the theoretical solutions. In this paper, the universal solution of radial vibration of metal ring with arbitrary variable thickness is given, which provides theoretical guidance for designing and optimizing the radial piezoelectric ultrasonic transducers.

MATHEMATICAL MODEL OF ELECTRO-MECHANICAL VIBRATION TRANSDUCERS BASED ON THE LEVITATION EFFECT

At present, one of the urgent problems in the energy and industry is to improve the reliability of the operation of various equipment. An effective method for increasing the reliability of equipment is diagnosing the state of machines and predicting their performance. Vibration control methods are widely used to diagnose rotary rotating machines. By the nature of the vibration process of the machine, it is possible to determine the degree of wear and, accordingly, the technical condition of the machines. In measuring technology for diagnostics of low-speed equipment with rotation frequencies of a unit of Hz, for example, hydroelectric generators of hydroelectric power plants, inertial electromechanical converters are used. The latest developments of such converters use an electromagnetic suspension with parametric feedback, which allows you to control the rigidity of the oscillatory system. However, for centering the moving part in electromechanical converters, flexible guides are used, which are sources of dry friction, which complicates the simulation of measurement processes and limits the sensitivity threshold to a minimum. In addition, flexible guides limit the frequency range of the converters. Currently, the most promising direction for solving this problem is the levitation effect, which allows you to completely exclude mechanical contact and, accordingly, reduce the sensitivity threshold of the transducer. From the analysis of literary sources, it follows that there are relatively few publications in this area. This article provides an analysis of existing vibration transducers and proposes a mathematical model of the magnetic levitation system, taking into account the influence of the electromagnetic force nonlinearity, as well as a method for selecting the feedback control unit parameters to stabilize the mass position of the vibration sensor.

"Can You Feel It": An Early Experience with Simulated Vibration to Recreate Glenoid Reaming.

We validated a novel custom simulator constructed using a vibration transducer transmitting simulated reaming vibrations to a powered nonwearing reamer tip through a 3D-printed glenoid. Validation and system fidelity were evaluated by 9 fellowship-trained shoulder surgeon experts performing a series of simulated reamings. We then completed the validation process through a questionnaire focused on experts' experience with the simulator. Experts correctly identified 52% ± 8% of surface profiles and 69% ± 21% of cartilage layers. Experts identified the vibration interface between simulated cartilage and subchondral bone (77% ± 23% of the time), indicating high fidelity for the system. An interclass correlation coefficient for experts' reaming to the subchondral plate was 0.682 (confidence interval 0.262-0.908). On a general questionnaire, the perceived utility of the simulator as a teaching tool was highly ranked (4/5), and experts scored "ease of instrument manipulation" (4.19/5) and "realism of the simulator" (4.11/5) the highest. The mean global evaluation score was 6.8/10 (range 5-10). We examined a simulated glenoid reamer and feasibility of haptic vibrational feedback for training. Experts validated simulated vibration feedback for glenoid simulation reaming, and the results suggested that this may be a useful additional training adjuvant. Level II, prospective study.

Optimization of a sandwich longitudinal vibration transducer with a large radiation surface based on hole structure of near-periodic phononic crystal

<p indent="0mm">The existence of radial vibration in a large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer will reduce the longitudinal radiated sound power and shorten the service life of the transducer, which seriously affects its performance and reliability. To reduce the strong coupling between longitudinal and radial vibration, ensure high longitudinal working efficiency and reliability, and overcome the disadvantages of narrow working bandwidth, poor uniformity of amplitude distribution, and small displacement amplitude, the large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer is optimized through machining several periodic holes on the front cover plate of the transducer to form a multi-point deformation defect structure. In this study, the simulation software is used to simulate and analyze the performance index of the optimized transducer, and the optimization effect is verified through experiments. The results show that the large-dimension piezoelectric ceramic transducer based on a multi-point deformation defect near-periodic phononic crystal structure has a single longitudinal vibration mode, which can effectively improve the displacement amplitude and amplitude distribution uniformity of the radiation surface of a large-dimension transducer and broaden the transducer’s working bandwidth.

Design of Longitudinal-Torsional Transducer and Directivity Analysis during Ultrasonic Vibration-Assisted Milling of Honeycomb Aramid Material.

This paper presents a longitudinal-torsional transducer for use during the ultrasonic vibration-assisted milling (UVAM) of honeycomb aramid material. The mechanism of longitudinal-torsional conversion was analyzed to guide the design of a vibration transducer. The transducer features five spiral grooves around the front cover plate, which function under the excitation of a group of longitudinal piezoelectric ceramics. A portion of the longitudinal vibration was successfully converted into torsional vibration. The resonant frequency, longitudinal vibration displacement and torsional amplitude at the top of the disk milling cutter were 24,609 Hz, 19 μm and 9 μm, respectively. In addition, the directivity of the longitudinal-torsional transducer was theoretically analyzed. Compared with conventional milling, UVAM with the longitudinal-torsional could significantly reduce the cutting force (40-50%) and improve the machining stability.

Research on Inherent Frequency and Vibration Characteristics of Sandwich Piezoelectric Ceramic Transducer

Great progress has been made in the field of ultrasonic processing in recent years, and piezoelectric ceramic transducers have been widely used as drive sources. In this paper, a sandwich piezoelectric ceramic transducer is designed, and the vibration of each part of the transducer is analyzed by elastic mechanics and piezoelectric theory. According to its mechanical and electrical boundary conditions, the vibration model of the piezoelectric transducer was established. Based on the equivalent elastic modulus method for simplifying the pre-stressed bolts into a one-dimensional transducer vibration model, the relationship between the one-dimensional axial response frequency of the transducer and the length of each component was obtained. Based on the half wavelength theory, a transducer with the vibration node in the crystal stack and an inherent frequency of 15 kHz was designed and fabricated. In order to verify the natural frequency and vibration characteristics of the piezoelectric transducer, a laser vibration measurement system was built in this study. The vibration characteristics of the transducer under different parameters such as voltage and frequency were analyzed, and the accuracy of the vibration model was verified. The vibration states of the end surface of the transducer and the radial surface were evaluated at the first-order inherent frequency and second-order inherent frequency. The results show that the equivalent simplified model established in this study can effectively design the inherent frequency of the transducer, and the operation at the first-order inherent frequency meets the one-dimensional assumptions of this study. The transducer operating conditions measured in this study also provide a more detailed reference for ultrasonic processing applications.

Non-Contact Vibro-Acoustic Object Recognition Using Laser Doppler Vibrometry and Convolutional Neural Networks

Laser Doppler vibrometers (LDVs) have been widely adopted due to their large number of benefits in comparison to traditional contacting vibration transducers. Their high sensitivity, among other unique characteristics, has also led to their use as optical microphones, where the measurement of object vibration in the vicinity of a sound source can act as a microphone. Recent work enabling full correction of LDV measurement in the presence of sensor head vibration unlocks new potential applications, including integration within autonomous vehicles (AVs). In this paper, the common AV challenge of object classification is addressed by presenting and evaluating a novel, non-contact vibro-acoustic object recognition technique. This technique utilises a custom set-up involving a synchronised loudspeaker and scanning LDV to simultaneously remotely solicit and record responses to a periodic chirp excitation in various objects. The 864 recorded signals per object were pre-processed into spectrograms of various forms, which were used to train a ResNet-18 neural network via transfer learning to accurately recognise the objects based only on their vibro-acoustic characteristics. A five-fold cross-validation optimisation approach is described, through which the effects of data set size and pre-processing type on classification accuracy are assessed. A further assessment of the ability of the CNN to classify never-before-seen objects belonging to groups of similar objects on which it has been trained is then described. In both scenarios, the CNN was able to obtain excellent classification accuracy of over 99.7%. The work described here demonstrates the significant promise of such an approach as a viable non-contact object recognition technique suitable for various machine automation tasks, for example, defect detection in production lines or even loose rock identification in underground mines.

Design, modelling and testing of a compact piezoelectric transducer for railway track vibration energy harvesting

To enable wireless sensor networks to monitor rail infrastructures in real-time, a cost-effective power source is in need. This work presents the design, modelling and testing of a piezo stack energy harvester with frequency up-conversion mechanism for scavenging energy from railway track vibration. The proposed harvester is designed to meet railway track applications’ size, frequency, and stress requirements. A compact design integrating the inertial mass and the piezo stack transducer systems is used to enable the mechanical collision for realising the frequency up-conversion mechanism and ensure the size of the energy harvester is suitable for the limited space on the railway track. The frequency bandwidth of the energy harvester is broadened by utilizing the longitudinal and torsional oscillation of the designed plate springs which enable the system to have two adjacent natural frequencies. The mechanical transformer of the piezo stack transducer system is designed to achieve the required stress level under both the impact force caused by the collision motion and the inertial force generated by the random vibration of the rails. A finite element model (FEM) analysing the free vibration of the piezo stack transducer caused by the frequency up-conversion mechanism is developed to analyse the dynamic characteristics of the coupled system. Lab tests are carried out to validate the proposed FEM and evaluate the impact of different factors such as load resistance, acceleration, initial interval, plate spring, and pulse excitation on power generation. Experimental results show that the energy harvester has two resonant frequencies of 17 Hz and 20 Hz. The frequency up-conversion mechanism can convert this low-frequency vibration into the piezo stack transducer’s high resonant frequency vibration of 94 Hz. A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration. • A piezo stack energy harvester for railway track vibration is designed, modelled and tested. • A compact design is proposed to enable the mechanical collision for realising the frequency up-conversion mechanism. • Two adjacent natural frequencies are achieved to broaden the frequency bandwidth. • The mechanical transformer is designed to achieve the required stress level under the impact force and inertial force. • A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration.

A generalized electromechanical coupled model of standing-wave linear ultrasonic motors and its nonlinear version

For the systematization of research on standing-wave linear ultrasonic motors (SWLUMs), this work develops a generalized electromechanical coupled model for characterizing SWLUMs. The proposed model focuses on dealing with modeling the generalized two-stage energy conversion in SWLUMs. The first-stage energy conversion is modeled by a four-terminal equivalent circuit model, which with a phase shifter and a couple of electromechanical transformers based on the electromechanical analogy method. The second-stage energy conversion is modeled by a physics-based, friction-driven system, involving contact nonlinearities between the stator and the mover. Furthermore, the effectiveness of this model and its further extension considering nonlinear vibrations of piezoelectric transducer (stator) are exemplified and discussed by a classical SWLUM with V-configuration stator, thereby indicating that the presented generalized model is valuable and pragmatic in simulating and characterizing SWLUMs both in electrical and mechanical domains.

Smart Active Vibration Control System of a Rotary Structure Using Piezoelectric Materials.

A smart active vibration control (AVC) system containing piezoelectric (PZT) actuators, jointly with a linear quadratic regulator (LQR) controller, is proposed in this article to control transverse deflections of a wind turbine (WT) blade. In order to apply controlling rules to the WT blade, a state-of-the-art semi-analytical solution is developed to obtain WT blade lateral displacement under external loadings. The proposed method maps the WT blade to a Euler–Bernoulli beam under the same conditions to find the blade’s vibration and dynamic responses by solving analytical vibration solutions of the Euler–Bernoulli beam. The governing equations of the beam with PZT patches are derived by integrating the PZT transducer vibration equations into the vibration equations of the Euler–Bernoulli beam structure. A finite element model of the WT blade with PZT patches is developed. Next, a unique transfer function matrix is derived by exciting the structures and achieving responses. The beam structure is projected to the blade using the transfer function matrix. The results obtained from the mapping method are compared with the counter of the blade’s finite element model. A satisfying agreement is observed between the results. The results showed that the method’s accuracy decreased as the sensors’ distance from the base of the wind turbine increased. In the designing process of the LQR controller, various weighting factors are used to tune control actions of the AVC system. LQR optimal control gain is obtained by using the state-feedback control law. The PZT actuators are located at the same distance from each other an this effort to prevent neutralizing their actuating effects. The LQR shows significant performance by diminishing the weights on the control input in the cost function. The obtained results indicate that the proposed smart control system efficiently suppresses the vibration peaks along the WT blade and the maximum flap-wise displacement belonging to the tip of the structure is successfully controlled.

A Wind Tunnel Study of the Flow-Induced Vibrations of a Cylindrical Piezoelectric Transducer.

Piezoelectric transducers are used as a sensing device to study the fluids’ motion. Moreover, they are used as a harvester of energy of Flow-Induced Vibration (FIV). The current FIV harvesters in the literature rely on piezoelectric cantilevers coupled with a bluff body that creates flow instabilities. This paper studies the use of piezoelectric cylinders as a novel transducer in the field of fluid mechanics, where the transducer makes use of its bluff geometry to create instability. The study was based on wind tunnel measurements performed on four piezoelectric cylinders of different sizes over a speed range of 1–7 m/s. The paper looks at the variation of the generated voltage across the Reynolds number. It also compares the spectra of the generated open-circuit voltage to the turbulence spectra features known from the literature.

A Linear Piezoelectric Actuator Using "A-Shaped" Structure.

A new design of linear piezoelectric actuator using "A-shaped" structure was proposed, designed, fabricated, and tested. By fusion design of the piezoelectric transducer and the mechanical structure, the proposed actuator only uses the first bending vibration of the center piezoelectric transducer to work. Frequency degeneration is no longer needed, which enables the actuator to adjust its structural parameters according to the application conditions. When applying an alternating voltage at resonance frequency, the center piezoelectric transducer will be stimulated in the first bending vibration. The vibration energy transmitted to the two driving arms generates alternating tilting movements with a phase difference of 180° between the two driving feet, which enables the actuator to push the linear guide when a vertical preload is applied. Under the preload of 120 N, the actuator gained a maximum thrust force of 9.8 N and a maximum output power of 0.62 W with a self-weight of 0.061 kg. The maximum output thrust density and the maximum output power density were 160.6 N/kg and 10.2 W/kg, respectively.