Piezoelectric Actuators Research Articles

Research on rotational rollback suppression of diamond-shaped active locking flexure mechanism (ALFM) driven by piezoelectric wafers

Abstract Piezoelectric actuators have a wide range of applications in many areas due to their advantages of fast response speed, high resolution, compact and simple structure, diverse configurations, and resistance to electromagnetic interference. However, existing piezoelectric actuators generally have large fallback, and a few researchers have applied the ALFM to the fallback suppression of actuators. In this paper, an ALFM using a piezoelectric wafer as the driving source is innovatively designed, and the structure and dimensions are simulated and optimized using Finite Element Method, according to which the piezoelectric wafer-type ALFM is used to design a new inertial piezoelectric actuator that can suppress backward movement. The motion principle of the piezoelectric actuator is theoretically analyzed, followed by the establishment of the machine dynamics model of the piezoelectric actuator and simulation with MATLAB/simulink to verify the reasonableness of the dynamics model. Finally, a series of experiments are carried out on the processed drive model, and the results show that the maximum accuracy of the actuator is 8.5 μrad, and the maximum load capacity is 160 g. The comparison experiments at 30 Hz and 40 Hz with and without the ALFM prove that the locking mechanism does supress the actuator from backing off to a certain extent, which verifies the reasonableness of the scheme proposed in this paper.

Piezoelectric deicing system for aeronautics: Extensional mode actuator and power supply

AbstractRecent research shows a growing interest in low‐power avionic deicing systems, in particular, those based on piezoelectric actuators for their energy efficiency. The system generates micrometric vibrations in the structure to delaminate and break the ice with a low power requirement. However, designing the power supply and its control for driving piezoelectric actuators is challenging due to their distinctive capacitive behavior at most frequencies, especially in deicing applications requiring high operational frequency. This contribution addresses the two cross‐dependent parts of the deicing system, that is the piezoelectric actuator designed for breaking any kind of ice on a large area and its power supply made of a 1 kW/200 V/2 MHz auxiliary resonant commutated pole inverter (ARCPI). The choice of this converter is based on the specific constraints of the application, such as varying the operating frequency with the actuator working conditions, the long cables and necessary insulation between the actuator and its supply, the soft‐switching operation and reactive energy balancing for a good efficiency. Based on these criteria, the converter was developed and realized in the laboratory. Deicing tests confirmed effective operation with a power input density of 122 mW/cm2, using nine piezoelectric patches per dm2.

Active micro-vibration isolation system for adaptive vibration suppression tests using piezoelectric stack actuator

An active micro-vibration isolation system for adaptive vibration suppression using piezoelectric stack actuators is presented, along with the discrete time modelling method, real-time adaptive controller design, and hardware implementation. The system comprises piezoelectric stack actuators, capacitive displacement sensors, power amplifiers, signal conditioners, and a real-time computer. A discrete asymmetric Bouc-Wen model is developed to characterize the nonlinear behavior of the piezoelectric stack actuators. System identification is conducted using an improved particle swarm optimization method, specifically the Hybrid PSO-Jaya algorithm, which sequentially integrates the PSO algorithm with the Jaya algorithm. Additionally, an improved adaptive filtering algorithm employing affine projection, referred to as the FXAPA algorithm, is introduced to facilitate real-time control. The efficacy of the proposed active micro-vibration isolation technology is validated through micro-vibration suppression tests.

Estimation, tuning, and evaluation of propagation direction behavior in superimposed orthogonal two-dimensional structure-borne traveling waves

Abstract Structure-borne traveling waves (SBTW) are observed in nature as a means for propulsion and locomotion of creatures on land and in the ocean. Recently, various approaches have been investigated to replicate this phenomenon. Previous studies have successfully generated SBTWs suitable for propulsion applications and particle motion on active surfaces. Much recent literature has focused on generating traveling waves that propagate only along a single axis for 1D and 2D structures. This limits their potential and does not take advantage of the full potential of 2D structures.
This study examines the potential of employing superposition to control the propagation direction of 2D SBTW. This is investigated numerically using an experimentally validated Finite Element model of a 2D plate with piezoelectric actuators. The individual SBTWs are superimposed by simultaneously exciting two pairs of actuators that are aligned orthogonally on the surface of a plate. Traveling waves are excited in the plate using two-mode excitation. Structural intensity is utilized to develop quantifiable metrics to describe the overall propagation direction and uniformity, which are necessary for describing the complex propagation patterns encountered with 2D SBTW. The potential of the proposed approach along with developed tuning and evaluation methods are demonstrated through case studies of two plates, one square and one rectangular. For both cases, the overall direction of the SBTW is tuned to propagate for any direction between the individual SBTW. This was achieved while maintaining a high-quality overall SBTW. With this approach, 2D SBTW can be steered for wave-driven motion applications such as propulsion of the structure itself or conveying particles in any direction along the structure's surface without compromising the quality of the overall traveling wave.

Dynamic modelling and mechanical analysis of an inertial linear piezoelectric actuator with double stators

Abstract To achieve higher output performance in precision applications, and in order to gain deeper insight into operation principle, a dynamic model is established including the transmission relationship between the stators, the driving shaft, and the mover based on a slip-slip type inertial linear piezoelectric actuator with double stators. The influence of stator material and symmetry ratio of the excitation signal on the vibration characteristics of the stator and the output performance are investigated. This study reveals the relationship between these factors through a combination of simulations and experiments. Prototypes using several materials are machined and assembled, and the vibration characteristics and output performance are rigorously tested. The results obtained from the experimental measurements are consistent with the simulation results, confirming the validity and rationality of the dynamic model. The experimental results of the stator, as well as the actuator, are analyzed. It can be concluded that the actuator is able to output a larger effective displacement in one motion period with the increased symmetry ratio of the triangular wave signal, applied with a higher operating frequency, resulting in a higher output velocity of 42 mm/s and a larger load of 300 g with the steel stator, and a higher displacement resolution of 18 nm can be achieved using the AL alloy stator. This research not only provides an effective method for enhancing and selecting the desired output performance for the researched actuator but also can be extended to other slip-slip type inertial linear piezoelectric actuators.

Inverse feedforward control of piezoelectric actuators using optimized composite neural network-based Hammerstein model

This paper utilizes the optimized composite neural network (OCNN)-Hammerstein model to directly identify the dynamic inverse hysteresis effect, employing it as a feedforward controller to compensate for the rate-dependent and amplitude-dependent dynamic hysteresis of the piezoelectric actuator. The OCNN-Hammerstein model consists of an optimized composite neural network and an auto-regressive exogenous model in series. The OCNN comprises convolutional neural network layer and radial basis function neural network layer, with its hyperparameters optimized using a modified grey wolf optimizer algorithm. Compared to the existing dynamic Prandtl-Ishlinskii-Hammerstein and dynamic Bouc-Wen-Hammerstein models in the literature, the feedforward controller based on the proposed model in this paper demonstrates superior performance, with an RSME below 0.45 μm and a 74.5% reduction in relative hysteresis at the condition of 300 Hz and maximum amplitude. The feedforward controller exhibits universality across all amplitude ranges and within the 50–300 Hz frequency range, while also providing predictive compensation for dynamic hysteresis at 300–400 Hz. The feedforward controller based on the OCNN-Hammerstein model in this paper provides a crucial methodology for open-loop control of piezoelectric actuators.

Acoustic Waves Coupling with Polydimethylsiloxane in Reconfigurable Acoustofluidic Platform.

Acoustofluidics is a promising technology that leverages acoustic waves for precise manipulation of micro/nano-scale flows and suspended objects within microchannels. Despite many advantages, the practical applicability of conventional acoustofluidic platforms is limited by irreversible bonding between the piezoelectric actuator and the microfluidic chip. Recently, reconfigurable acoustofluidic platforms are enabled by reversible bonding between the reusable actuator and the replaceable polydimethylsiloxane (PDMS) microfluidic chip by incorporating a PDMS membrane for sealing the microchannel and coupling the acoustic waves with the fluid inside. However, a quantitative guideline for selecting a suitable PDMS membrane for various acoustofluidic applications is still missing. Here, a design rule for reconfigurable acoustofluidic platforms is explored based on a thorough investigation of the PDMS thickness effect on acoustofluidic phenomena: acousto-thermal heating (ATH), acoustic radiation force (ARF), and acoustic streaming flow (ASF). These findings suggest that the relative thickness of the PDMS membrane (t) for acoustic wavelength (λPDMS) determines the wave attenuation in the PDMS and the acoustofluidic phenomena. For t/λPDMS≈O(1), the transmission of acoustic waves through the membrane leads to the ARF and ASF phenomena, whereas, for t/λPDMS≈O(10), the acoustic waves are entirely absorbed within the membrane, resulting in the ATH phenomenon.

Nonlinear Control System for Flat Plate Structures Considering Interference Based on Operator Theory and Optimization Method

In recent years, vibration control utilizing smart materials has garnered considerable attention. In this paper, we aim to achieve vibration suppression of a plate structure with a tail-fin shape by employing piezoelectric actuators—one of the smart materials. The plate structure is rigorously modeled based on the Kirchhoff–Love plate theory, while the piezoelectric actuators are formulated in accordance with the Prandtl–Ishlinskii model. This research proposed a control system that addresses the interference effects arising during vibration control by dividing multiple piezoelectric elements into two groups and implementing MIMO control. The efficacy of the proposed control method was validated through simulations and experiments.

A novel approach to enhance the structural integrity of a bottom-edge cracked I-beam with piezoelectric actuators

Structural health monitoring and repair have become increasingly crucial in confirming the safety and longevity of damaged structures. This study presents a novel approach to enhancing the structural integrity and extending the fatigue life of a bottom-edge cracked I-beam by applying piezoelectric actuators strategically placed along the crack location by actively suppressing crack propagation. An innovative actuation system induces controlled deformations in the I-beam, effectively reducing the Stress Intensity Factor (SIF) and preventing crack propagation. The efficacy of the proposed approach is validated through a series of numerical results on the ABAQUS platform, including static loading, fatigue loading, and crack growth monitoring. Various parameters, like maximum loading capacity under static loading, interpretation of crack growth rate, and service life, are monitored and analyzed throughout the cyclic loading process. The results demonstrate that the application of 500 V to the piezoelectric actuators significantly reduces the SIF by 16.62% under a 2 kN total load, a 2.86% enhanced maximum load-carrying capacity is obtained, delayed crack propagation is found after repair, and a 72.67% extended service life is achieved under a load range of 0.2 kN to 2 kN. Overall, the outcomes of this research lead to the development of innovative and efficient techniques for delaying the propagation of cracks, thereby preventing the premature onset of catastrophic failure of cracked I-beams.

Boosting Low-E electro-strain via high-electronegativity B-site substitution in lead-free K0.5Na0.5NbO3-based ceramics

Lead-free piezoelectric actuators emerge as promising substitutes for their lead-containing counterparts to address environmental concerns. However, they often confront a trade-off between low driving electric fields and high electro-strain. Herein, a novel strategy to boost electro-strain under low electric fields is proposed by doping high-electronegativity B-site atoms into perovskite potassium sodium niobate-based ceramics. Our findings reveal that high-electronegativity B-site atoms elevate the covalency of B-O bonding, softening the short-range repulsion and introducing local multiphase coexistence. This leads to more nanoscale domain structures and lower coercive field, thereby enabling large strains to be produced at lower electric fields. Notably, a substantial 0.2 % bipolar electro-strain and 0.1 % unipolar electro-strain under 10 kV cm-1 is achieved in Sr, Sb co-doped potassium sodium niobate ceramics, with a broad working frequency and temperature range, as well as excellent fatigue resistance. This study unveils innovative insights into designing lead-free piezoelectric ceramics with remarkable electro-strain performance and low driving electric field, promising a significant advancement in lead-free piezoelectric materials science and piezoelectric actuators.

A hybrid summation and multiplication displacement amplification mechanism for piezoelectric actuators

Abstract This paper reports a novel amplified piezoelectric actuator featuring compliant displacement amplification mechanism of hybrid summation and multiplication. The hybrid amplification mechanism uses the concept of nesting a pair of Scott-Russell linkages into a toggle linkage to realize the hybrid amplification functions of summation and multiplication. Also, compliant amplification mechanisms with double output ports are designed, enhancing the flexibility of designs and applications. The hybrid displacement amplification principle is mathematically explained in detail. It is demonstrated based on finite element simulations that the displacement amplification ratio, output stiffness and resonance frequency of the proposed hybrid amplification mechanism of summation and multiplication outperform those of the classic rhombus-type and bridge-type compliant mechanisms. The experimental testing results of a prototype show that the amplified piezoelectric actuator is capable of providing 315 μm strokes with the displacement amplification ratio of 16.2. The fundamental resonance frequency with piezoelectric stacks mounted is 1218 Hz. Comparison to typical designs in literature shows well comprehensive performances of statics and dynamics, verifying the advantages of such a hybrid amplification mechanism of summation and multiplication.

Measuring inverse flexoelectric effect at the macro scale and flexoelectric actuator

Abstract The flexoelectric effect is a two-way mechanical-electrical coupling. The dielectric is polarized when subjected to bending moments, and inversely, the electric field can also induce strain gradients within the dielectric. Although equally important, research on the inverse flexoelectric effect has lagged far behind that on the direct effect, and investigations of the inverse effect on a macroscopic scale are noticeably lacking. This dilemma impedes the design of flexoelectric actuators. To go out of the dilemma, in this work, we design an experimental method to achieve inverse flexoelectricity and propose a method to measure the inverse flexoelectric effect with a lower voltage at the macroscopic scale. The result shows that the flexoelectric coefficient of SrTiO3 (STO) single crystal from the inverse flexoelectric experiment has the same order of magnitude as that of the direct flexoelectric experiments. Furthermore, this method can be utilized to design an STO flexoelectric actuator on a macroscopic scale. The displacement resolution of flexoelectric actuators is as low as 0.42 pm V−1, which is three orders of magnitude lower than that of piezoelectric actuators. This type of flexoelectric actuator is important for precise driving and positioning.

LSTM-Inversion-Based Feedforward–Feedback Nanopositioning Control

This work proposes a two-degree of freedom (2DOF) controller for motion tracking of nanopositioning devices, such as piezoelectric actuators (PEAs), with a broad bandwidth and high precision. The proposed 2DOF controller consists of an inversion feedforward controller and a real-time feedback controller. The feedforward controller, a sequence-to-sequence LSTM-based inversion model (invLSTMs2s), is used to compensate for the nonlinearity of the PEA, especially at high frequencies, and is collaboratively integrated with a linear MPC feedback controller, which ensures the PEA position tracking performance at low frequencies. Therefore, the proposed 2DOF controller, namely, invLSTMs2s+MPC, is able to achieve high precision over a broad bandwidth. To validate the proposed controller, the uncertainty of invLSTMs2s is checked such that the integration of an inversion model-based feedforward controller has a positive impact on the trajectory tracking performance compared to feedback control only. Experimental validation on a commercial PEA and comparison with existing approaches demonstrate that high tracking accuracies can be achieved by invLSTMs2s+MPC for various reference trajectories. Moreover, invLSTMs2s+MPC is further demonstrated on a multi-dimensional PEA platform for simultaneous multi-direction positioning control.

Tunable Imaging Distance Focusing Module Directly Driven by a Thin‐plate Piezoelectric Actuator

AbstractWith the advancement of imaging technology, the performance of optical focusing modules becomes crucial for determining imaging quality. Conventional focusing modules frequently face challenges of excessive bulk and weight, complicating the integrated design and limiting application fields. Herein, this study presents a piezo‐actuated optical focusing module (POFM) and the construction strategy to alleviate these issues. A novel radial‐bending resonant‐type piezoelectric actuator (RB‐RPA) is developed to directly drive the POFM. The RB‐RPA, which features a hollow structure (27 × 27 × 7 mm3), utilizes both radial and bending vibration modes of a thin metal plate. It achieves a speed of 122.93 mm s−1, a thrust force of 0.14 N, and a displacement resolution of 0.52 µm. Employing the proposed construction strategy, RB‐RPA is integrated with imaging components to fabricate a POFM prototype. Furthermore, the micrometer‐level displacement resolution of POFM facilitates optical focusing on imaging targets, allowing the acquisition of sharp images within 70 ms. It achieves an image resolution of 119.57 lp mm−1 within a 42 mm segment of the captured image. Finally, a QT‐based interface for the POFM, enables real‐time image capture and sharpness evaluation, thereby enhancing imaging efficiency and integration. This work provides a potential candidate for next‐generation imaging devices.

Hysteresis compensation and decoupling control of an XYΘ-type flexure-based mechanism via inverse hysteresis-coupling hybrid modeling

Planar positioning systems are widely utilized in micro and nano applications. The challenges in modeling and control of XYΘ flexure-based mechanisms include hysteresis of the piezoelectric actuators, couplings among the input axes, and coupled linear and angular motions of the end effector. This paper presents an inverse hysteresis-coupling hybrid model to account for such hysteresis and couplings. First, a specially designed kinematic chain is adopted to transfer the pose of the end effector into the linear motions at three prismatic joints. Second, an inverse hysteresis-coupling hybrid model is developed to linearize and decouple the system via a multilayer feedforward neural network. A fractional-order PID controller is also integrated to improve the motion accuracy of the overall system. Experimental results demonstrate that the proposed method can accurately control the motion of the end effector with improved accuracy and robustness.

Physics-informed neural networks with data-driven in modeling and characterizing piezoelectric micro-bender

Abstract Despite the rapid development and widespread adoption of physics-informed neural networks (PINNs) in various engineering fields, their applications in microelectromechanical coupling systems (MEMS) remain relatively unexplored. In this study, we demonstrate a novel implementation of PINNs for modeling and characterizing a piezoelectric microactuator. By leveraging the beam-like structure, the governing equations for a multi-layered piezoelectric actuator are first derived and subsequently incorporated into the PINNs model to accurately predict the deformation of the piezoelectric actuator in response to a given voltage input. Furthermore, by integrating experimental deflection data obtained from Laser Doppler Vibrometer measurements into the neural network, we further demonstrate the potential of PINNs in identifying the piezoelectric material coefficient through inverse analysis. Our contribution in applying PINNs to models and characterizing piezoelectric actuators in MEMS serves as a promising starting point for the broader utilization of machine learning techniques in this field.

A piezoelectric driven amphibious microrobot capable of fast and controllable movement

Abstract Due to its excellent adaptability to the environment and flexibility in narrow spaces, amphibious microrobots have become an important research direction recently. This study proposes an amphibious microrobot driven by piezoelectric actuators with a body length of 4.5 cm and a mass of 1.4 g. The microrobot consists of two active front legs, two passive rear legs, two caudal fins, and a support frame. Each front leg and each caudal fin are designed as structures integrated with their respective piezoelectric actuators. The microrobot has a tilted body, and the ground exerts an oblique upward impact force that makes it jump forward when its front legs swing backwards. The opposite swing of the two caudal fins generates propulsion for swimming. The components of the microrobot are manufactured based on the monolithic laminate process. The monolithic front actuator-leg and monolithic actuator-fin both emerge from a multi-layer material laminate. The support frame is designed and fabricated as a monolithic structure to improve assembly accuracy and reduce redundant assembly steps. The manufactured microrobot demonstrates its flexible and fast amphibious movements. Its maximum land walking speed reaches 15.3 cm/s and its turning speed reaches 48.2 degrees per second. The microrobot has a maximum payload capacity of 5 g moving on land. When the front legs and caudal fins work simultaneously, its underwater swimming speed reaches 9.1 cm/s, and the maximum turning speed is 20.5 degrees per second. The microrobot also confirms a maximum payload of 3 g during its underwater movement.

A new optimization framework for piezoelectric actuators location identification

The study addresses piezoelectric actuator placement for active vibration control using an open-access framework that couples ANSYS and Python. It outlines a three-stage procedure: creating a finite element model in ANSYS APDL, using Python to determine the objective function, and applying a genetic algorithm optimization to find optimal actuator locations. Numerical simulations on plates and thin-walled conical structures demonstrate the effectiveness of the approach, showing it efficiently finds optimal placements with minimal search time and energy requirements. The study provides open-access codes for the framework, enhancing its accessibility and reproducibility.

Experimental Validation of One-Dimensional Model of an Ideal Bimorph Actuator Provided on Bidomain Lithium Niobate

The study demonstrates that the dynamic characteristics of piezoelectric bimorph actuators based on bidomain lithium niobate (BLN) single crystals are accurately described by an analytical one-dimensional (1D) model of an ideal bimorph. Our observations show that displacements and an electric impedance of the BLN-based bimorphs can be predicted without use of any sophisticated lumped circuit models, equations with handpicked “effective” values of material’s constants or finite element method. The experimental data were measured by means of laser interferometry and impedance spectroscopy and then fitted with the equations predicted by the 1D model. Solving the inverse problem for the experimental points we calculated the transverse piezoelectric coefficient, longitudinal mechanical compliance, dielectric permittivity, and piezoelectric coupling coefficient of the material. The obtained values of the material constants of the lithium niobate y + 128°-cut crystal are d23 = 25 pC/N, s33E = 7.58 TPa−1, ε22T = 52.7 ε0, and k232 = 0.18, which are in excellent agreement with the literature data.

Development and Testing of a Dual-Driven Piezoelectric Microgripper with High Amplification Ratio for Cell Micromanipulation

Cell micromanipulation is an important technique in the field of biomedical engineering. Microgrippers play a crucial role in connecting macroscopic and microscopic objects in micromanipulation systems. However, since the operated biological cells are deformable, vulnerable, and typically distributed in sizes ranging from micrometers to millimeters, it poses a huge challenge to microgripper performance. To solve this problem, this paper develops a dual-driven piezoelectric microgripper with a high displacement amplification ratio, large stroke, and parallel gripping. By adopting modular configuration, three kinds of flexure-based mechanisms, including the lever mechanism, Scott–Russell mechanism, and parallelogram mechanism are connected in series to realize three-stage amplification, which effectively makes up for the shortage of small output displacement of the piezoelectric actuator. At the same time, the use of the parallelogram mechanism also isolates the parasitic rotation movement, and realizes the parallel movement of the gripping jaws. In addition, the kinematics, statics, and dynamics models of the microgripper are established by using the pseudo-rigid body and Lagrange methods, and the key geometric parameters are also optimized. Finite element simulation and experimental tests verify the effectiveness of the developed microgripper. The results show that the developed microgripper allows an amplification ratio of 46.4, a clamping stroke of 2180 μm, and a natural frequency of 203.1 Hz. Based on the developed microgripper, the nondestructive micromanipulation of zebrafish embryos is successfully realized.