Piezoelectric Ultrasonic Actuator Research Articles

A High-Power-Density Piezoelectric Actuator Operating in Bicycling Movement Mechanism

Comprehensive high-precision actuations are in growing demand to meet diversified needs in scientific and industrial fields. However, it is a great challenge for piezoelectric actuators with compact structure to guarantee high load capacity and wide velocity range (including fast motion velocity and high resolution) simultaneously. Herein, inspired by bionic methodology, a high-power-density bar-type linear piezoelectric ultrasonic actuator (LPUA) operating in the single second bending (<i>B₂</i>) mode with elaborate working principle is developed by imitating bicycle movement mechanism. The proposed <i>B₂</i>-LPUA actuator is simple, and easy for miniaturization without multimodal decoupling problem. Under only one-phase voltage drive, the miniature bar-type actuator can produce continuously bidirectional motions with the maximum driving velocity, minimum driving velocity, load, and output power of 211.2 mm&#x002F;s, 3.3 &#x03BC;m&#x002F;s, 5.4 N, and 218.3 mW, respectively, and the tested minimum step displacement is only 33 nm in open-loop control. Especially, its output power density (243 mW&#x002F;cm³ or 4.112 mW&#x002F;cm³.kHz) is at least twice larger than most reported LPUAs. The experimental results indicate that the proposed piezoelectric actuator with excellent actuation performances has broad application scenarios, and its bionic motion design method would have inspirational significance for creating new piezoelectric devices with more attractive properties.

Research on the Influence of Friction Pairs on the Output Characteristics of the Piezoelectric Ultrasonic Actuator

The piezoelectric ultrasonic actuator is driven by the friction coupling between the stator and mover. Its friction pairs are very important, but there are few studies on the long-term output stability. Therefore, zirconia (ZrO2) is selected as a stator material to form friction pairs with four different wear-resistant materials: silicon nitride (Si3N4), ZrO2, bearing steel (GCr15) and polyether ether ketone (PEEK). Experiments show that the friction pair composed of ZrO2-Si3N4 is the best, and the attenuation percentage of the speed from the initial state to the end state in the speed rising stage of 50 m is 3.66%. A linear piezoelectric platform is developed based on the best friction pair; a maximum speed of 426.2 mm/s and a resolution of 85 nm are achieved.

Low-operating voltage-based piezoelectric ultrasonic actuator for tactile system applications

This article presents the design and analysis of a piezoelectric-based ultrasonic actuator to be used for tactile system applications. The device made of four pieces of piezoelectric material arranged in alternate way to complete the actuator structure. When the voltages are applied on the device, and at a resonant operating frequency, two vibration modes are simultaneously activated, the first longitudinal mode (L 1) and the second bending mode (B 2). The actuator size is tiny and able to drive the external load with stable and low-input voltage. The proposed actuator is suited for tactile feedback device, as well as feasible for low-input applications for prolonged usage. From the study, it is observed that the maximum output force at the voltage of 50 V is 1.6 N for the proposed structure while the optimum force is 1 N. Its small dimension, 20.1 × 2 × 0.75 mm and low-input voltage of 50 V makes it portable and easy to fabricate into small and precise devices.

Study on improving the resolution of an H-shaped piezoelectric ultrasonic actuator by stick-slip principle

Improving the performance of the motion stages driven by piezoelectric actuators is an enduring topic for expanding their applications. For the motion stage with a travel range of tens of millimeters, trade-offs are inevitable between getting high speed (hundreds of millimeters per second) and high resolution (tens of nanometers), due to the inherent limitations of the operating principles of the piezoelectric actuators. In order to improve the output resolution of an H-shaped piezoelectric ultrasonic actuator, sawtooth excitation voltages are used in this work rather than the conventional sinusoidal voltages in previous works. The configuration and operating principle of the actuator are discussed in detail. The actuator consists of two vertical and two horizontal longitudinal transducers. The ends of the vertical transducers act as the driving tips and drive the stage forward with the alternating slow extensions and rapid contraction, during which stick motions and slip motions of the stage are acquired. An analytic model is developed to estimate the horizontal and vertical output displacement of the driving tip. The maximum error between the predicted value of the analytical model and the experimental value is about 14%. A prototype of the motion stage is fabricated and experiments are carried out to evaluate its output characteristics. The experiment results confirm the operating principle and show that the resolution is upgraded to tens of nanometers. The prototype obtains a resolution of 19 nm, a maximum speed of 2.22 μm s−1, and a maximum carrying load of 16.94 kg.

Electromechanical Equivalent Circuit Model of a Piezoelectric Disk Considering Three Internal Losses

Heat generation by internal loss factors of piezoelectrics is one of the critical issues for high power density piezoelectric applications, such as ultrasonic motors, piezoelectric actuators and transducers. There are three types of internal losses in piezoelectric materials, namely dielectric, elastic and piezoelectric losses. In this paper, a decoupled equivalent circuit is proposed to emulate a piezoelectric disk in radial vibration mode considering all three types of internal losses. First, the decoupled equivalent circuit is derived according to the conventional electromechanical equivalent circuit model. Then, a piezoelectric disk configuration in radial vibration mode is explored and simulated. The resonance and antiresonance frequencies and their corresponding mechanical quality factors are achieved by the proposed circuit. In order to verify the accuracy of the simulation results, the piezoelectric disk is fabricated and tested. Simulation results with the new circuit exhibit a good agreement with experimental results. Finally, the equivalent circuit with only dielectric and elastic losses are simulated and compared which further validates the accuracy improvement of the new equivalent circuit considering all three losses.

Demonstration and Experimental Validation of Plastic-Encased Resonant Ultrasonic Piezoelectric Actuator for Magnetic Resonance Imaging-Guided Surgical Robots.

Intra-operative medical imaging based on magnetic resonance imaging (MRI) coupled with robotic manipulation of surgical instruments enables precise feedback-driven procedures. Electrically powered nonferromagnetic motors based on piezoelectric elements have shown to be well suited for MRI robots. However, even avoiding ferrous materials, the high metal content on commercially available motors still cause distortions to the magnetic fields. We construct semicustom piezoelectric actuators wherein the quantity of conductive material is minimized and demonstrate that the distortion issues can be partly addressed through substituting several of these components for plastic equivalents, while maintaining motor functionality. Distortion was measured by assessing the root-mean-squared (RMS) change in position of 49 centroid points in a 12.5 mm square grid of a gelatin-filled phantom. The metal motor caused a distortion of up to 4.91 mm versus 0.55 mm for the plastic motor. An additional signal-to-noise-ratio (SNR) drop between motor off and motor spinning of approximately 20% was not statistically different for metal versus plastic (p = 0.36).

Mechanical and energetic characteristics of an energy harvesting type piezoelectric ultrasonic actuator

Piezoelectric ultrasonic actuators (PUA) are fascinating and precision-controlled actuators in some mechatronics systems. This study proposed an energy harvesting type piezoelectric ultrasonic actuator (H-PUA) and investigated its mechanical and energetic characteristics. The proposed H-PUA has a sandwich-type stator composed of a metal body, an exciting piezoelectric (PZT) ring and a harvesting PZT ring. The exciting PZT ring bonded on the bottom surface of the stator was used to produce a traveling wave, and the harvesting PZT ring bonded on the top surface of the stator was used to harvest the vibration-induced energy of the stator and convert it into electric energy. Sensitivity analysis method was used to optimize the stator structure. Finite element analysis using ANSYS software was performed for both the mechanical and energetic characteristics of the new actuator. A prototype H-PUA was fabricated and subsequently used to test the mechanical and energetic characteristics. When the rotor torque is zero and the pre-pressure is 100 N, the prototype H-PUA has mechanical output characteristics of no-load speed 112 rpm and stalling torque 0.78 Nm when the exciting voltage amplitude is 152 V0−p with frequency 36.0 kHz. The maximum harvesting output power of a sector area of the harvesting PZT ring reaches 54 mW when it is connected to an optimized load resistance 11 kΩ. Experiments have shown that the harvesting output energy can fully meet with the power supply demands of some low-power (i.e., mW/μW level) mechatronics systems, such as LED.

Motion Control for Piezoelectric-Actuator-Based Surgical Device Using Neural Network and Extended State Observer

This paper presents a robust neural network with an extended state observer control methodology for a piezoelectric-actuator-based surgical device. This control methodology is proposed for tracking of desired motion trajectories in the presence of unknown or uncertain system parameters, nonlinearities including friction, hysteresis, and disturbances in the motion system. In particular, the radial basis function neural network, which serves as a function approximator, aims to create a model for an unknown function to find a relationship between input and output data. An extended state observer is utilized to assist in canceling disturbances and uncertainties of the system dynamically. The stability of the control approach is analyzed. The convergence of position and velocity tracking errors is proven theoretically. Experiments are conducted to demonstrate that the performance with an improved accuracy can be attained by the proposed control scheme. With the motion tracking capability, the control methodology helps the novel surgical device achieve higher success rate in operation, which is also suitable for similar piezoelectric ultrasonic actuator applications.

Vector Control of Piezoelectric Transducers and Ultrasonic Actuators

This paper presents the implementation of a novel vibration amplitude control and resonant frequency tracking for piezoelectric transducers (PTs) and ultrasonic motors (USMs). It is based on a generalization of the vector control method to the PT and the USM, which is explained in the first part. We show that two independent controllers with a similar structure are required: one tracks the resonant frequency and the second controls the amplitude. We then present the implementation into a low-cost digital signal processing controller with a sampling period of 200  $\mu$ s. Experimental results on a Langevin transducer achieved a time response of 20 ms approximately, and the generality of the method is further demonstrated on a 2-D tactile stimulator at the end of this paper.

Simulation and Optimal Design of Acoustic Field of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Linear Array Actuator

Simulation and Optimal Design of Acoustic Field of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Linear Array Actuator

Developments of piezoelectric ultrasonic actuators operating under bending hybrid vibration modes

ABSTRACTThe exciting methods for the sandwich type piezoelectric ultrasonic actuators used bending hybrid modes are investigated. Five exciting methods are discussed and compared in detail, in which the polarizations and the partitions of the ceramic rings are different. Harmonic analyses are developed to obtain the effects of the exciting methods on the electromechanical coupling factors and the vibration amplitudes. At last, five prototypes are manufactured to verify their differences. Both the simulation and experiment results prove that the exciting method using ceramic rings with four separated partitions achieves great improvements on the efficiency, velocity and force, synchronously.

Development of a bi-directional standing wave linear piezoelectric actuator with four driving feet

A bi-directional standing wave linear piezoelectric ultrasonic actuator with four driving feet is proposed in this work. Two sandwich type transducers operated in longitudinal-bending hybrid modes are set parallelly. The working mode of the transducer is not simple hybrid vibrations of a longitudinal one and a bending one, but a special coupling vibration mode contained both longitudinal and bending components. Two transducers with the same structure and unsymmetrical boundary conditions are set parallelly to accomplish the bi-directional driving: the first transducer can push the runner forward, while the other one produces the backward driving. In the experiments, two voltages with different amplitudes are applied on the two transducers, respectively: the one with higher voltage serves as the actuator, whereas the other one applied with lower voltage is used to reduce the frictional force. The prototype achieves maximum no-load speed and thrust force of 244 mm/s and 9.8 N. This work gives a new idea for the construction of standing wave piezoelectric ultrasonic actuator with bi-directional driving ability.

Novel design, analytical and experimental studies of a piezoelectric ultrasonic linear actuator based on binate feet driving

This article presents the piezoelectric ultrasonic linear actuator based on binate feet driving. The actuator is equipped with a rhombus binate feet mechanism to generate two synchronous rectangle driving trajectories. With the help of the two synchronous trajectories, the proposed actuator can deliver stable long-range motion (the designed maximum stroke is 19 mm) accompanying with large loading capacity and high driving resolution. The configuration and operational principle are described in detail and the driving trajectory of the binate feet is analyzed. Finite element analysis is conducted to investigate the static deformation and stress status of the driving mechanism at every step. The experimental system is established to test the performance of the actuator prototype and the results indicate that the prototype can be operated stably step by step and all steps have high reproducibility. The driving resolution (minimum step length) of the actuator prototype is 25.9 nm. The maximum loading capacity and the maximum thrust are 37.2 and 3.2 N, respectively. The experimental results also confirm that the designed actuator can achieve various motion velocities by changing the driving voltage and driving frequency.

Analysis and Experimental Research of a Multilayer Linear Piezoelectric Actuator

To lower the operating voltage and improve the output performance of piezoelectric actuators, a multilayer monolithic ultrasonic linear piezoelectric actuator was analyzed with the method of finite element analysis (FEA), and a prototype was fabricated and experimentally researched in this study. Experimental results show that the actuator with a multilayer piezoelectric lead zirconate titanate (PZT) structure (size: 30 × 7.5 × 3 mm3, mass: 5.49 g) can output a pulling force of 5.0 N maximum and a linear velocity up to 270 mm/s at the voltage of 100 Vpp (Vpp means the peak-to-peak value of the voltage volts), showing a relatively good velocity controllability at the same time. The temperature rise characteristic of the actuator at various voltages was studied. The results indicate that: the temperature of this actuator rises rapidly but tends to saturate at some value; applying an offsetting voltage or decreasing the amplitude of the voltage would reduce the heat production.

A Smart Ultrasonic Actuator with Multidegree of Freedom for Autonomous Vehicle Guidance Industrial Applications

A piezoelectric ultrasonic actuator with multidegree of freedom for autonomous vehicle guidance industrial applications is presented in this paper. The actuator is aiming to increase the visual spotlight angle of digital visual data capture transducer. It consists of three main parts, the stator, rotor and housing unit. The stator is a piezoelectric ring made from S42 piezoelectric ceramics material, bonded to three electrodes made from a material that has a close Characteristics to the S42. The rotor is a ball made from stainless steel materials. The actuator working principles is based on creating micro elliptical motions of surface points, generated by superposition of longitudinal and bending vibration modes, of oscillating structures. Transferring this motion from flexible ring transducer through the three electrodes, to the attached rotor, create 3D motions. The actuator Design, structures, working principles and finite element analysis are discussed in this paper. A prototype of the actuator was fabricated and its characteristics measured. Experimental tests showed the ability of the developed prototype to provide multidegree of freedom with typical speed of movement equal to 35 rpm, a resolution of less than 5μm and maximum load of 3.5 Newton. These characteristics illustrated the potential of the developed smart actuator, to gear the spotlight angle of digital visual data capture transducers and possible improvement that such micro-actuator technology could bring to the autonomous vehicle guidance and machine vision industrial applications. Furthermore research are still undertaken to develop a universal control prototype, integrate the actuator with an infrared sensor, visual data capture digital transducers and obtain the trajectory of motion control algorithm.

Optimization of matching layer structure for piezoelectric fiber composite ultrasonic actuator and performance testing

Orthotropic piezoelectric fiber composite is used as a functional material for new phased array transducer, which can be applied in a wide range of fields such as natural gas, power industry, aerospace and other nondestructive evaluation fields. The backing layer of the transducer affects the pulse width and axial resolution directly. In order to find transducers with good sensitivity and short pulses, the pulse shape and frequency response for orthotropic piezoelectric fiber composite elements have been studied both theoretically and experimentally. The acoustic impedance of velocity testing criterion has been provided, and the relative theory and experiment have also been researched. The results show that orthotropic piezoelectric fiber composite has lower acoustic impedance and higher mechanical coupling factor. Also, the sensitivity and bandwidth of orthotropic piezoelectric fiber composite ultrasonic actuator have been improved.

Optimal Design of the Single-Mode Piezoelectric Actuator

The general operation of a piezoelectric ultrasonic actuator is to convert the cyclic motion of the piezoelectric plate to a linear motion at the rotor or slider. The conventional piezoelectric ultrasonic actuator has two symmetric exciter electrodes on the front surface and each electrode covers one half of the front surface. The rear surface has only one electrode that severs as a common drain. In this paper, the design and simulation of the novel single-mode piezoelectric actuator with asymmetric electrodes were presented. The accomplishment of this study is to find the optimal dimensions of the piezoelectric plate and the asymmetric electrodes, and the stator tip on the piezoelectric ultrasonic actuator would have the larger vibrating amplitude. From the simulation experiment results, the optimal dimensions of the piezoelectric plate are 20×10×1 mm with 12 mm exciter electrode length, and the vibrating amplitude is from 0.73μm increasing to 0.91μm.

Design of the Piezoelectric Actuator with Double Driving Tips

The general operation of a piezoelectric ultrasonic resonant actuator is to convert the cyclic motion of the piezoelectric plate to a linear motion at the rotor or slider. The conventional piezoelectric ultrasonic actuator has only one stator tip to impart both the contact (normal) and driving (tangential) force on the rotor or slider. Since the rotor/slider is driven through friction, the only one stator tip design will result in lower output torques. In theory, a piezoelectric ultrasonic actuator with more stator tips will have larger output torques. However, it is difficult to design a piezoelectric actuator with multiple stator tips with synchronous cyclic motion. In this paper, the design and simulation of a novel piezoelectric actuator with multiple stator tips are presented. The accomplishment of this study is to reduce the motion difference between two different stator tips on the piezoelectric ultrasonic actuator. The Taguchi method was used to find out the optimal dimensions of the piezoelectric plate and the result shows the motion difference between two different stator tips was reduced from 19μm to 0.03μm in the X-direction and from 9μm to 0.18μm in the Y-direction.

Component based modelling of piezoelectric ultrasonic actuators for machining applications

Ultrasonically Assisted Machining (UAM) is an emerging technology that has been utilized to improve the surface finishing in machining processes such as turning, milling, and drilling. In this context, piezoelectric ultrasonic transducers are being used to vibrate the cutting tip while machining at predetermined amplitude and frequency. However, modelling and simulation of these transducers is a tedious and difficult task. This is due to the inherent nonlinearities associated with smart materials. Therefore, this paper presents a component-based model of ultrasonic transducers that mimics the nonlinear behaviour of such a system. The system is decomposed into components, a mathematical model of each component is created, and the whole system model is accomplished by aggregating the basic components' model. System parameters are identified using Finite Element technique which then has been used to simulate the system in Matlab/SIMULINK. Various operation conditions are tested and performed to demonstrate the system performance.

A new loudspeaker for low frequency radiation by linear motion type piezoelectric ultrasonic actuators

The authors had proposed new direct-radiator loudspeaker constructions with a conventional paper cone radiator driven by ultrasonic motors (USM), as a substitution for voice-coil motor. However, those models needed a revolution to linear motion conversion mechanism, and avoiding zero region non-linearity, like class A amplifier. These complications came from the conventional USM, since it is a rotational and having zero region non-linearity inherently. Here, the authors would propose a new mechanism by using new ultrasonic linear actuators, called longitudinal-bending multilayered transducers with independent electrodes (LBMTIE). The beauty of LBMTIE is linear and to control vertical motion and horizontal motion independently, hence zero region non-linearity avoided. Therefore, it is possible to substitute the voice-coil motor directly, which avoids the complicated mechanisms mentioned above. In this LBMTIE driven loudspeaker, vertical movement voltage be fixed and horizontal voltage is driven by audio signal, like voice-coil motor. In addition, there is a big contrast against conventional voice-coil motor, which is a typical transducer, as its electrical input and sound pressure output are direct proportion each other. This is because LBMTIE driven loudspeaker may behave a sort of modulator, which is not direct proportion in between input electric power and output sound pressure level.