Bending Transducer Research Articles

A Broadband, High-Power Resonant Piezoelectric Active-Valve Pump Driven By Sandwich Bending Transducers

A resonant piezoelectric active-valve pump driven by the serial connected there-chambers is proposed based on three sandwich bending transducers (SBTs). The pump possesses the superiorities of high bandwidth and high output power. The configuration and driving principle of the pump are designed and studied. The wet modal and frequency response analyses are performed to determine the resonant frequency and output displacement, and their consistencies are also evaluated. The multi-physical field coupling model of the pump is established by bi-directional fluid structure interaction. The influences of frequency and outlet pressure of the pump on flowrate characteristics at different voltages are revealed. A physical prototype of the pump is manufactured and the tested setup is constructed to measure the output performances. This work shows that the maximum flowrate of the pump is 345 mL/min at 1.95 kHz; the maximum pressure can reach up to 242 kPa at 2.05 kHz. Besides, the self-filling pressure is 78 kPa; and the maximum driving power is 432 mW with an outlet pressure of 125 kPa. The results show that the developed pump is expected to be used in the hydraulic drive system of UAV variable swept wing.

Development of a novel high bandwidth piezo-hydraulic actuator for a miniature variable swept wing

Piezoelectric hydraulic actuators, instead of electromagnetic actuators, have a wide application prospect in the field of aerospace due to the merits of light weight, compact structure, non-magnetic interference, etc. Many researches have been devoted to boosting output powers of actuators with the help of large-scale piezoelectric stacks. However, the existing actuator operates at a relatively low frequency, limiting the output power improvement and the application. In this work, a high bandwidth piezo-hydraulic actuator (PHA) is proposed based on a resonant active valve piezoelectric pump with sandwich bending transducers (SBTs). The configuration and principle of the PHA are presented and analyzed. A tested setup of the PHA is established, and the maximum output velocity and thrust are measured to be 30.5 mm/s and 53.2 N under 1.6 kHz, and the output power reaches up to 294 mW under the load of 30 N. In addition, a variable swept wing (VSW) driven by the PHA is studied. The composition and deformation process of the PHA-Based VSW are discussed; the dynamic model of the PHA-Based VSW is derived; the tested results indicate that the maximum angular velocity and torque of the PHA-Based VSW are 1.135 rad/s and 1.701 N·m, and the swept angle range is 15.9° ∼ 64.1°

Development of a High-Pressure Self-Priming Valve-Based Piezoelectric Pump Using Bending Transducers

In this article, a valve-based piezoelectric pump operated by three bending transducers is proposed. The major features of the proposed pump are self-priming and high pressure. The structure and the operation principle of the proposed pump are presented and analyzed in detail. The output displacement of the transducer can be obtained by the Timoshenko beam theory; on this basis, the flowrate and pressure models of the pump are established based on gap flow theory and the extended Bernoulli equation. A prototype of the pump is fabricated, and the experimental system is established. The results indicate that the maximum output flowrate is 58.6 mL/min under the frequency of 160 Hz; the maximum output pressure is 28.7 kPa at the frequency of 180 Hz, and the maximum output power is 6 mW at the backpressure of 12.5 kPa. Besides, the self-priming of the pump is 10.7 kPa; thus, there is no need to fill the pump during the working process, which can bring a convenience to the operation of the pump.

Development of a High Differential Pressure Piezoelectric Active Proportional Regulation Valve Using a Bending Transducer

In this article, a piezoelectric active proportional regulation valve with high differential pressure is proposed based on a bending transducer. The output flowrate of the valve can be accurately controlled by a bending transducer. The configuration design and driving principle of the valve are presented and analyzed. The static analyses are performed to determine the structural parameters of the valve and deduce its transient overflow gap. On this basis, the overall flowrate model of the valve is established using the theory of circumferential flow and extended Bernoulli equation. The effects of differential pressure and driving voltage on output flowrate are clarified. A prototype of the valve is manufactured and the experimental setup is also established to evaluate the performances of the valve. The results indicate that the proportional regulation of the valve can be achieved by changing the driving voltage; the valve displacement and response time under no liquid-loading condition are 16.16 μm and 340 μs at the voltage of 300 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> ; the maximum output flowrate is 286.3 mL/min under the differential pressure of 344.75 kPa, and the leakage level is 0.11%; the maximum cut-off pressure of 275.8 kPa can be realized; the corresponding input power is 185 mW.

Design and Experimental Characterization of an Actuation System for Flow Control of an Internally Blown Coanda Flap

The focus of the work is on the evaluation, development and integration of a robust actuator system for three-dimensional flow control of a blown Coanda flap to improve the high lift system of commercial aircraft. As part of the research work presented, the system is integrated into a wind tunnel model in order to influence the flow across the entire width of the model. The system developed is based on individual bending transducers that can vary the height of the blowing slot dynamically. The system is divided into 33 segments and is therefore able to implement static and dynamic actuation along the wing-span (3D-actuation). All segments can be controlled independently and thus offer great optimization potential for an effective flow control. Different configurations were developed and evaluated against each other with respect to the demanding requirements (small installation space, frequency range from 5 Hz to 300 Hz, 1 bar pressure, 0.4 mm deflection, 1 m span). The design of the blown flap has been specified in an iterative design process. In the final configuration, all mechanical components are reduced to the bare minimum for weight reduction reasons, in order to meet the dynamic requirements of the wind tunnel model. To characterize the lip segments, a test device has been designed that can be pressurized to generate aerodynamic loads on the lip segments. Finally, 33 lip segments were integrated into a wind tunnel model and tested intensively as part of a measurement campaign. The first aerodynamic results show an increase in lift of up to ∆Ca = 0.57. These aerodynamic gains are achieved at amplitudes that do not require the lip segments to completely close or open the blowing slot, which shows the advantage of the current lip design that enables activation with independently controlled stationary and unsteady components.

Transient dynamic analysis of laminated shallow spherical shell under low-velocity impact

The impact of transient response laminated shallow shells due to transverse foreign object was investigated analytically and experimentally. The analytical analysis is presented by using the new higher order shear deformation shell theory. The contact force ishassumedhtohbe a known inputhtohthehanalysis. Contact force and transverse deflection of laminated shell have been measured with a piezoelectric force transducer (load cell) and a piezoelectric bending transducer respectively. Laminates made from E-glass polyester and E-glass/carbon/polyester having different thickness and stacking sequences have been used. The analysis can be used to calculate the difference between the transient stresses, displacements, velocities, accelerations and energy observation at the center of laminated shell are plotted as function of time during impact between E-glass/polyester and E-glass/carbon/polyester by MATLAB code at different impact heights to determine whether they have a good resistant ability to impact. Finally, it was compared with the results of an experimental test to verify the accuracy and reliability of the theoretical analysis.

Design of an underwater acoustic array for full ocean depth multi-beam echo sounder

In order to meet the technical requirements of full ocean depth multibeam echo sounder, the underwater acoustic array must have the ability of wide coverage, broadband response, high sensitivity and high reliability. This paper presents a design of underwater acoustic array based on Mills cross configuration with separate transmitting and receiving units. The arrays have modules design, hence the beamwidth of the array can be adjusted according to particular installation requirements. The working frequency band of the arrays is between 10.5kHz to 13.5kHz, and the coverage angle can cover -71.6°~71.6°. The Integrated design is used to achieve a wide-angle beam coverage of the planar array, which combines the transducer and the sound baffle together to realize a wide directivity of the array elements. The longitudinal bending transducers are designed to meet the broadband requirements for the transmitting array, which are Tonpilz transducers with flexural radiating head. On the other hand, each element of the receiving array is composed of several hydrophones, which are connected in series to achieve high sensitivity. The double-layer watertight technology is also applied in our design, ensuring stable performance and long service life.

A four-foot walking-type stepping piezoelectric actuator: driving principle, simulation and experimental evaluation

A four-foot walking-type piezoelectric actuator using non-resonant bending transducers, inspired by the movements of quadrupeds, was proposed and tested to achieve driving abilities of both long stroke and high resolution. Two transducers operated under bending hybrid modes were used together to simulate the stepping motion of a quadruped: the rectangular trajectory movements of the driving feet were generated by a combination of designed bending motions and the runners were pushed linearly step-by-step. The simulation analyses were carried out by using a finite element method to verify the driving trajectory. Finally, a prototype was manufactured to further verify the driving mechanism and to evaluate the output characteristics. The step displacement, maximum no-load velocity and maximum thrust of the prototype are 8.23 μm, 1.65 mm s−1 and 12 N respectively. This work provides a new driving mechanism for the design of non-resonant piezoelectric actuators with simple structure, long stroke, high resolution, high velocity and large output thrust by utilizing the bending motions of two sandwich transducers.

Graphene quantum dot–poly(vinylidene fluoride) composite for the preparation of asymmetric bilayer bending transducer

A newly developed asymmetric bilayer bending transducer composed of a graphene quantum dot (GQD)–poly(vinylidene fluoride) (PVDF) composite and a simple adhesive tape has been investigated. This bending transducer displays high actuation displacement (10.2 mm) and large electromechanical strain (0.3%) under relatively low electric field strength (20.8 MV m−1). The key to the high electromechanical performance lies in the unique GQD–PVDF interfacial structure and the high dielectric constant of GQD–PVDF (2350 at 1 Hz, 1% GQD weight percentage) caused by the interfacial polarization effect. The good electromechanical performance of our device shows bright prospect of GQD in smart materials field.

Design and Experimental Evaluation of a Stepper Piezoelectric Actuator Using Bending Transducers

A stepper piezoelectric actuator, in which two bending transducers were used to push a runner step-by-step alternatively, was proposed and tested in this paper. Each bending transducer can bend in horizontal ( $X$ ) direction and vertical ( $Y$ ) direction, independently. The bending motion of the transducer in the vertical direction was used to control the contact state between the driving tip and the runner; the linear stepper movement of the runner was accomplished by the horizontal bending motion of the transducer when the driving tips is contacting with the runner. The piezoelectric actuator can realize linear stepper motion by designing the sequences of the bending motions of the two transducers. The operating principle of the stepper driving was illustrated and discussed in detail. A finite-element method was used to simulate the motion trajectories of the driving tips. A prototype was fabricated to verify the operating principle, and the mechanical output characteristics were measured. The runner was pushed linearly step-by-step under four square wave signals with temporal shifts, a maximum no-load speed of $227.3~\mu \text{m}$ /s was achieved, and the maximum output thrust force was tested to be about 14 N. The proposed piezoelectric actuator achieves long stroke, large output force, and precision driving by using two non-resonant bending transducers.

A combination of silicone dielectric elastomer and graphene nanosheets for the preparation of bending flexible transducers

A newly developed dielectric elastomer (DE) bending transducer composed of a functionalized graphene-silicone DE composite sandwiched between two graphene flexible electrode layers had been investigated. This bending transducer displayed high actuation displacement (5.3mm) under 2500V direct-current electric field. Compared with pure silicone DE, the silicone DE filled with silane coupling agent functionalized graphene nanofillers showed enhanced dielectric constant, and low loss modulus. The silane coupling agent functionalization method is simple, green, and easy to control, and can be used asa general strategy for improving the dielectric and electric actuated strain of DE.

The co-casting process: A new manufacturing process for ceramic multilayer devices

In this work we present a simplified process chain of the conventional multilayer ceramic technology and offer a comfortable method for precise multilayer manufacturing without complex equipment. To circumvent the usual stacking and laminating of single ceramic green tapes to get multilayer devices, a Magnetically Assisted Stencil Printing (MASP) technique was developed. It enables a subsequent casting of ceramic layers and printing of electrode layers. How the co-casting process can be performed either by the use of a modified tape caster at the lab scale or by use of a precision squeegee is described in this paper. Both variants are suited for manufacturing multilayer ceramics with layer thicknesses less than 25μm. We successfully manufactured pentalayers without cracks or de-laminations from a soft- and also a hard-PZT powder. In a previous work, we investigated sintering additives for PZT. By the use of a PZT-based low-temperature sintering powder composition, cost-effective silver inner electrodes could be realized inside the multilayer ceramics. Piezoelectric low-cost multilayer bending transducers are of particular interest for the use as generators in vibration energy harvesting systems. The proposed triplelayer beam harvests 20μW (3.2V) at 71Hz and an input acceleration of 17.8m/s2.

Motion Planning of a Stepping-Wriggle Type Piezoelectric Actuator Operating in Bending Modes

A new non-resonant-type piezoelectric actuator with unlimited stroke was proposed, in which two transducers operated in hybrid bending modes were used to generate the desired displacements with micrometer scale. Compared with the PZT stack, both positive and negative dc voltages can be applied on the PZT elements to achieve large displacement. The vertical bending movement was used to control the contact state between the foot and the runner, whereas the runner was pushed by the horizontal bending movement. The operating principle of the stepping-wriggle driving was discussed. The motion planning of the bending transducers with eight steps was developed. The duty ratios and the phase difference of the two signals applied on the vertical PZT elements were 1/3 and 180°, respectively, which insured the reliable positioning of the runner. Excitation voltages with different rise times were applied on the PZT elements to discover its effects on the responses of the bending movements by a transient analysis. It was found that the transducer cost about 2 ms to reach the steady state, in spite of the difference of the rise times, but the rise time showed a significant effect on the oscillation amplitude of the bending motion. The motion trajectories of the driving tip were nearly rectangles with horizontal and vertical steady displacements of $\sim 6.10$ and 5.52 $\mu \text{m}$ , respectively. This paper can provide the guidance for the design of non-resonant-type piezoelectric actuator by bending modes.

A Novel Rotary Piezoelectric Motor Using First Bending Hybrid Transducers

We report a novel rotary piezoelectric motor using bending transducers in this work. Three transducers are used to drive a disk-shaped rotor together by the elliptical movements of their driving tips; these motions are produced by the hybrid of two first bending vibration modes. The proposed piezoelectric transducer has a simple structure as it only contains an aluminum alloy beam and four pieces of PZT plates. Symmetrical structure is the only necessary condition in the design process as it will ensure the resonance frequencies of the two orthogonal first bending modes are equal. Transducers with first bending resonance frequency of about 53 kHz were fabricated and assembled into a rotary motor. The proposed motor exhibits good performance on speed and torque control. Under a working frequency of 53.2 kHz, the maximum no-load speed and the maximum torque of the prototype are tested to be 53.3 rpm and of 27 mN·m.

Light- and Humidity-Induced Motion of an Acidochromic Film.

A smart acidochromic agarose-based film with 1,4-bis(para-hydroxystyryl)benzene as the pH-responsive fluorophore was prepared. This film can simultaneously harness the chemical potential of light and aerial humidity gradients to convert them into mechanical work. The strong reversible hygroscopicity of the agarose matrix induces swift locomotion by mechanical deformation owing to exchange of water with the surroundings. Driven by humidity, a 20 mg composite film coupled to a piezoelectric bending transducer sensor generates a peak output of approximately 80 mV, which corresponds to a power density of 25 μW kg(-1). Excitation with UV light triggers isomerization of the chromophore, which appears as reshaping by spiraling, bending, or twisting of the film. The material also responds to changes in the pH value by reversible protonation of the fluorophore with rapid changes in color and fluorescence. The threefold sensing capability of this smart material could be utilized for the fabrication of multiresponsive actuating dynamic elements in biomedicine and soft robotics.

Light‐ and Humidity‐Induced Motion of an Acidochromic Film

AbstractA smart acidochromic agarose‐based film with 1,4‐bis(para‐hydroxystyryl)benzene as the pH‐responsive fluorophore was prepared. This film can simultaneously harness the chemical potential of light and aerial humidity gradients to convert them into mechanical work. The strong reversible hygroscopicity of the agarose matrix induces swift locomotion by mechanical deformation owing to exchange of water with the surroundings. Driven by humidity, a 20 mg composite film coupled to a piezoelectric bending transducer sensor generates a peak output of approximately 80 mV, which corresponds to a power density of 25 μW kg−1. Excitation with UV light triggers isomerization of the chromophore, which appears as reshaping by spiraling, bending, or twisting of the film. The material also responds to changes in the pH value by reversible protonation of the fluorophore with rapid changes in color and fluorescence. The threefold sensing capability of this smart material could be utilized for the fabrication of multiresponsive actuating dynamic elements in biomedicine and soft robotics.

A Novel Co-casting Process for Piezoelectric Multilayer Ceramics with Silver Inner Electrodes

The presented process offers a simplified method for manufacturing multilayer ceramics (MC) in comparison to the conventional multilayer ceramics technology (MCT). It combines the tape casting of ceramic green tapes and the subsequent screen printing of electrodes into one single co-casting process. Since the co-casting process circumvents also the stacking and laminating of single ceramic green tapes, MC with layer thicknesses as thin as 20μm could be manufactured by this technique. To create an easy contacting of the inner electrode in the MC, the generation of an interdigital electrode structures has been aspired. By means of the specific innovation, to fix a shadow mask by magnetic forces on top of the ceramic green tape, this was realized. With the intention to manufacture piezo generators for vibration energy harvesting, triple-layered bending transducers have been manufactured successfully from a hard-doped PZT powder and inner electrodes made of pure silver via this new co-casting process. The material compatibility for the co-firing step of PZT and the cost-effective base metal silver was achieved by means of the liquid phase sintering technology, using a combination of Li2CO3·Bi2O3·CuO (LBCu) as sintering additives.

Development of a new ultrasonic actuator based on Langevin bending transducer

A new ultrasonic actuator based on a bending-type Langevin piezoelectric transducer has been developed. An actuator consists of a half-wavelength Langevin transducer and an aluminum plate that is mounted in the middle of the transducer. The driving tip is located at the bottom of the aluminum plate. Piezoceramic rings with opposite polarity within each half of the ring are divided into two groups. Two harmonic signals with shifted phases by π/2 are used to excite the first bending mode of the Langevin transducer and aluminum plate. Elliptical trajectory of the contact point motion is obtained by combining these two bending modes. Numerical modelling was carried out to analyze harmonic response of the actuator and to investigate the trajectories of the contact point motion. Optimization of the aluminum plate design was performed to maximize the parameters of elliptical motion of the driving tip. A prototype actuator was fabricated, and output characteristics were measured. The results of numerical and experimental study are discussed.

Flexible Optical Fiber Bending Transducer for Application in Glove-Based Sensors

The development of a low-cost and flexible optical fiber transducer for measurement of angular displacements is reported. The light intensity attenuation due to fiber microbending losses is correlated to the variations in flexing angle, yielding to a sensitivity of 1.80°. The device was also mounted in a fabric glove to the monitoring of flexion and abduction movements of index and thumb fingers. Once calibrated by a simple procedure, the glove-based system was capable to measure the angular positions with average errors <;5° and 7° for interphalangeal and metacarpophalangeal joints, respectively. Additionally, the repeatability analysis resulted in average range and standard deviations of 8.06° and 3.45°, respectively. The optical fiber sensor provides a low-cost alternative to the real-time monitoring of hand posture, and can be suitable for applications in human-robot and human-computer interactions.

Acoustic streaming in an ultrasonic air pump with three-dimensional finite-difference time-domain analysis and comparison to the measurement

The direct finite-difference fluid simulation of acoustic streaming on a fine-meshed three-dimensional model using a graphics processing unit (GPU)-based calculation array is discussed. Airflows are induced by an acoustic traveling wave when an intense sound field is generated in a gap between a bending transducer and a reflector. The calculation results showed good agreement with measurements in a pressure distribution. Several flow vortices were observed near the boundary layer of the reflector and the transducer, which have often been observed near the boundary of acoustic tubes, but have not been observed in previous calculations for this type of ultrasonic air pump.