Linear Piezoelectric Actuator Research Articles

A Novel Type of Noncontact Linear Piezoelectric Actuator Modulated by Electromagnetic Field: Design and Experiment.

To explore a noncontact drive solution for linear piezoelectric actuators, a novel type of noncontact linear piezoelectric actuator modulated by the electromagnetic field is proposed. The proposed actuator employs electromagnetic force to modulate and transfer the locomotion between the stator and the runner. The drive scheme reduces the wear and friction between the stator and the runner and can control the coupling force by the electric system. Here, the design pattern and working principles are described. The amplification ratio equation of the flexible amplification mechanism is established, and the calculation method of the dynamic electromagnetic force is illustrated. For assessing the validity and measure the output characteristics of the proposed actuator, a prototype is fabricated to measure the output speeds, the stepping distances, and the output forces. The experimental results show the actuator with the driving frequency of 1 Hz, the electromagnetic modulation voltage of 4 V, and the piezoelectric driving voltage of 100 V can continuously output a stall load force of about 0.15 N and speed of 0.33 mm/s.

Frequency Agile Slot Antenna Using Contactless Capacitive Loading

With the development of modern wireless systems, the spectral environment has become increasingly crowded. This has spawned a strong interest in frequency, bandwidth, and pattern reconfigurable antennas, which can adaptively tune their response to reduce interference. Most recent development in frequency reconfigurable antennas has focused on tuning by use of microelectromechanical systems, pin diodes, or varactors. However, these tuning techniques are ill-suited for high power applications due to breakdown, non-linear effects, and other performance issues. These problems can be solved by the use of mechanical tuning. In this paper, a piezoelectric linear actuator tuned slot antenna is presented. The design is based upon changing the capacitive loading of a slot antenna, and thereby increasing the electrical length, through physical displacement of a metal plate. The antenna was simulated, fabricated, and measured to tune a full octave from 2-4 GHz while maintaining a maximum return loss of greater than 9.0 dB. Simulations also show a 65.74% to 95.75% radiation efficiency across S-band. A broadside realized gain of greater than 1.73 dB was measured over the entire tuning range. Moreover, the tuning mechanism was proven robust above other methods by withstanding up to 100 W of power incident on the feed at 3 GHz.

Achieving smooth motion and high-speed for piezoelectric stick-slip actuator based on the two-stage lever principle.

With the development of the precision manufacturing industry, actuators' performance requirements are increasingly demanding. However, stick-slip actuators still have the problems of backward motion and low motion speed at low frequencies. In this paper, to decrease the backward motion and achieve high speed at low frequencies, a linear piezoelectric stick-slip actuator is designed based on the two-stage lever principle. Theoretical and numerical investigations are used to optimize the flexible hinge of the stick-slip actuator. Experimental results indicate that the motion slider can achieve a smooth motion. The backward rate can even drop to 0. The maximum motion speed was 124.83 mm/s at 1600 Hz. The motion speed of the designed actuator was higher than that of previous stick-slip actuators at the same frequency. In addition, the load capacity of the prototype is tested. Based on different loads, the load matching is achieved by an auxiliary piezoelectric-stack, where the maximum horizontal load was 2.3 N. According to the comparison with previous actuators, the designed prototype can achieve high speed at low frequencies. Furthermore, the displacement curves show good smoothness. These characteristics will be helpful for the practical application of stick-slip piezoelectric actuators.

A stick-slip piezoelectric actuator with suppressed backward motion achieved using an active locking mechanism (ALM)

Backward motion commonly exists in the stick-slip linear piezoelectric actuator, resulting in deterioration of the output performance and limiting their applications. To solve the problem, a stick-slip linear piezoelectric actuator with suppressed backward motion, achieved using an active-locking mechanism (ALM) with two mechanisms, is proposed in this paper. One mechanism involves stick-slip driving, while the other actively suppresses backward motion by clamping the slider during the backward driving process through efficient control. A prototype actuator was designed and manufactured to verify the feasibility of this method, and an experimental system was established to obtain the detailed parameters. Also, to verify the feasibility and effectiveness of the suppression effect on backward motion of the proposed actuator, the output performance of the traditional stick-slip actuator and the actuator with the ALM were compared. Based on the results, we demonstrate that the maximum output speed and maximum output force of the prototype are 2.26 mm s−1 and 1.6 N under a voltage of 100 V, respectively.

A Digitized Representation of the Modified Prandtl-Ishlinskii Hysteresis Model for Modeling and Compensating Piezoelectric Actuator Hysteresis.

Piezoelectric actuators are widely used in micromanipulation and miniature robots due to their rapid response and high repeatability. The piezoelectric actuators often have undesired hysteresis. The Prandtl–Ishlinskii (PI) hysteresis model is one of the most popular models for modeling and compensating the hysteresis behaviour. This paper presents an alternative digitized representation of the modified Prandtl–Ishlinskii with the dead-zone operators (MPI) hysteresis model to describe the asymmetric hysteresis behavior of piezoelectric actuators. Using a binary number with n digits to represent the classical Prandtl–Ishlinskii hysteresis model with n elementary operators, the inverse model can be easily constructed. A similar representation of the dead-zone operators is also described. With the proposed digitized representation, the model is more intuitive and the inversion calculation is avoided. An experiment with a piezoelectric stacked linear actuator is conducted to validate the proposed digitized MPI hysteresis model and it is shown that it has almost the same performance as compared to the classical representation.

Development of a Novel 2-DOF Rotary-Linear Piezoelectric Actuator Operating under Hybrid Bending-Radial Vibration Mode.

The paper presents a numerical and experimental investigation of a novel two degrees of freedom (2-DOF) piezoelectric actuator that can generate rotary motion of the sphere-shaped rotor as well as induce planar motion of the flat stage. The actuator has a small size and simple design and can be integrated into a printed circuit board (PCB). The application field of the actuator is small-dimensional and high-precision positioning systems. The piezoelectric actuator comprises three rectangular bimorph plates joined with arcs and arranged by an angle of 120 degrees. A high-stiffness rod is glued on the top surface of each bimorph plate and is used to rotate the rotor or move flat stage employing contact friction force. Three U-shaped structures are used for the actuator clamping. 2-DOF rotational or planar movement is obtained by applying a harmonic or asymmetric electrical signal. The operation principle of the actuator is based on the superposition of the B20 out-of-plane bending mode of the bimorph plates and the B03 radial vibration mode of the ring. Design optimization has been performed to maximize amplitudes of contact point vibration. A prototype of the actuator was made, and a maximum rotation speed of 795.15 RPM was achieved while preload of 546.03 mN was applied. The linear velocity of 36.45 mm/s was obtained at the same preload force. Resolution measurement showed that the actuator can achieve an angular resolution of 17.48 µrad and a linear resolution of 2.75 µm.

Micro motion of a piezoelectric linear actuator driven by liquid interacting with Rayleigh surface acoustic wave

The research work presents a newly developed mechanism using liquid for surface acoustic wave (SAW) actuator making linear motion resulting in a no-load lightweight design. The proposed actuator consists of Interdigital Transducers (IDTs) fabricated on two ends of lithium niobate (LiNbO3) substrate and a cylindrical slider placed over the surface of the substrate in contact with liquid. The actuator uses Rayleigh wave traveling on the surface of the piezoelectric stators that transmit into a liquid medium which drives a cylindrical slider in translational motion. As the slider is not placed directly in contact with the stator, so the damage of piezo substrate or slider due to direct frictional contact is avoided. Due to this advantage, the longevity of the device will be enhanced and the driving load becomes easier. The movement of the slider on the liquid surface can be made to move in reverse direction by energizing the IDTs fabricated on other side of the substrate. The finite element simulation of the proposed SAW actuator and the experimental results demonstrates the slider reaches a steady-state velocity of 37.5 mm/s for application of wave excitation.

A theoretical model of the intermittent contact of piezoelectric actuator based on Greenwood-Williamson theory

A theoretical model of the intermittent contact mechanism of linear piezoelectric actuator was proposed, in which the microscopic characteristics of the contact surfaces were taken into account. Greenwood-Williamson (GM) theory was involved for the first time to describe the microscopic characteristics of the contact surfaces in which the contact surfaces were considered as random rough surfaces that were composed of large amounts of asperities and the heights of the asperities conformed to a Gauss distribution. The developed theoretical model gives an insight into the influence of the microscopic properties, as well as the macroscopic and material properties on the output performance of the actuator, which may provide guidance for the design of such type of piezoelectric actuator. During the modeling, normal kinetic contact force, kinetic friction coefficient, friction force and steady-state output force of were obtained in sequence. And some simulations were carried out to analyze how factors such as the type of material, the roughness of the contact surface, the initial distance between the stator and the rotor, and the preload, et.al, affect the contact performance. A set of experiments were carried out to reveal the influence of surface roughness, material type and preload on the steady-state output thrust. The simulated results were found in good agreement with the experiment ones at most of the tested points. Finally, surface roughness of the stator and rotor were tested before and after the operation, which indicated that the rotor and stator had similar roughness after operation.

Super Resolution for Improved Positioning of an MRI-Guided Spinal Cellular Injection Robot

This paper presents the development of a magnetic resonance imaging (MRI)-conditional needle positioning robot designed for spinal cellular injection. High-accuracy targeting performance is achieved by the combination of a high precision, parallel-plane, needle-orientation mechanism utilizing linear piezoelectric actuators with an iterative super-resolution (SR) visual navigation algorithm using multi-planar MR imaging. In previous work, the authors have developed an MRI conditional robot with positioning performance exceeding the standard resolution of MRI, rendering the MRI resolution the limit for navigation. This paper further explores the application of SR to images for robot guidance, evaluating positioning performance through simulations and experimentally in benchtop and MRI experiments.

Investigation on a Linear Piezoelectric Actuator Based on Stick-Slip/Scan Excitation

To perform a high resolution and long stroke application in optical precision instruments, a linear piezoelectric actuator operated in stick-slip/scan modes for driving a linear motion table is presented. The proposed piezoelectric actuator is a piezoelectric composite structure, which includes a metal elastomer, a piezoelectric stack, and a frictional ball. The purpose of this paper is to describe the operation principle, design, and the running test and resolution test of the linear motion table driven by the proposed piezoelectric actuator. The notable feature is the flexible hinges of the actuator, including composite hinge, pre-pressure adjustment flexible hinge, and transmission flexible hinge, which are designed for decoupling the motion in the action direction of the piezoelectric stack and the direction in which the pre-pressure is applied. A prototype has been fabricated and two operation modes of the piezoelectric actuator, stick-slip and scan mode, were utilized to test the driving characteristics of the linear motion table. Experimental results show that the finest step resolutions in stick-slip mode and scan mode achieved 12 nm and 4 nm, respectively.

A Piezoelectric Linear Actuator Controlled by the Reversed-Phase Connection of Two Bimorphs

A linear actuator controlled by the reversed-phase connection of two piezoelectric bimorphs is proposed in this study to solve the problem of drawback in the existing piezoelectric linear actuators. The actuator is driven by one excitation signal, the two piezoelectric bimorphs will always bend in opposite directions by the reversed-phase connection, so the directions of the force output by the two piezoelectric bimorphs are opposite. Because of the length difference of the clamping blocks, the two forces outputted by each bending is different in magnitude, and always have a resultant force in the same direction to make the actuator move forward two steps in one cycle without drawback. A series of experiments were conducted to evaluate the performance of the actuator provided. The starting voltage is 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\mathrm {p-p}}$ </tex-math></inline-formula> , resolution can reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.16~\mu \text{m}$ </tex-math></inline-formula> without load. The load capacity of the actuator is 450 g with a 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\mathrm {p-p}}$ </tex-math></inline-formula> voltage, a 2-Hz frequency, and the average step displacement in this case is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.725~\mu \text{m}$ </tex-math></inline-formula> . The prototype has high linearity and good repeatability. Experiments have proved that the actuator controlled by reversed-phase connection can eliminate drawback in principle, and can move forward two steps in one cycle. The resolution of the prototype by the reversed-phase connection is much higher than the in-phase connection, and it is a new method to improve the driving performance of piezoelectric actuators.

A novel stick-slip piezoelectric rotary actuator designed by employing a centrosymmetric flexure hinge mechanism

Although the stick-slip piezoelectric linear actuators have been widely investigated, the design of stick-slip piezoelectric rotary actuators is rarely reported and the corresponding output performances could be further improved. In this study, by employing a centrosymmetric flexure hinge mechanism, a novel stick-slip piezoelectric rotary actuator was designed. Its structure and working processes were addressed in detail, and the main structural parameters of the centrosymmetric flexure hinge mechanism were designed by the finite-element method. After that, a prototype was fabricated and a series of experiments were performed to test its output performances. The experimental results showed that under various driving voltages, the actuator could output stable angular displacement, and with increase in the driving voltage, the angular speed tended to linearly increase. Under the driving voltage of 100 V and driving frequency of 600 Hz, the actuator reached a maximum angular speed of about 55 000 μrad s−1. The driving resolution of the actuator was 0.34 μrad, and the maximum vertical loading capacity and torque were tested to be 6 kg and 30 N · mm, respectively. In addition, both clockwise and anticlockwise rotations were realized by simply changing the direction of the driving voltage waveform, and furthermore, under the same experimental conditions, very similar output performances were achieved in clockwise and anticlockwise rotations. Compared with some previously reported stick-slip piezoelectric rotary actuators, it was confirmed that the vertical loading capacity and driving resolution of the designed actuator here had been improved, which would be beneficial to its practical application.

A novel piezoelectric linear actuator designed by imitating skateboarding movement

By imitating skateboarding movement, a novel stick–slip piezoelectric linear actuator was proposed in this study. A specific flexure driving foot mechanism (FDFM) was designed to realize the bionic driving function, and theoretical analysis was conducted to calculate the displacement amplification ratio of the FDFM which was further confirmed by finite element simulation. Being different from most of previous design that the slider moved and the driving mechanism was fixed, here the FDFM was integrated with the slider and they moved together along the guide rail. Being similar to that the train moved along the tracks, this kind of layout would facilitate the realization of larger working stroke of the actuator. By experiments, output characteristics of the designed actuator under various driving frequencies and voltages were tested. The results showed that by changing the waveform of driving voltage, both forward and reverse motions with good linearity and stability could be easily achieved. The speed of reverse motion was higher than that of forward motion because of the relatively larger backward motion during forward motion, which was due to the promotion of deformation recovery of the FDFM. Furthermore, the resolution and loading capacity were characterized. The resolutions of forward and reverse motions were 47 nm and 45 nm, respectively, and the actuator could achieve a relatively stable speed when the vertical load was in the range of 0–2 N. This study is expected to provide a new idea for designing piezoelectric actuators with features of high speed, high stability and large working stroke.

A self-positioning linear actuator based on a piezoelectric slab with multiple pads

A component-less, long-driving-region and self-positioning piezoelectric actuator was developed to transmit several gram-weight components. The linear piezoelectric actuator was composed of a piezoelectric slab and comb-shaped capacitive position sensor. The length-to-width ratio of the driving pad was designed to ensure successive in-phase connection when the driving pad was subjected to an electric field. The proposed 44 × 8 × 1.5 mm3 piezoelectric slab had a driving region of 37.5 mm, that is, 85% of the length of the actuator larger than previous studies to save space. Two pairs of capacitive comb-shaped electrodes were screen-printed on a slider clip (mover) and piezoelectric slab (stator) to sense the position of the slider clip. Sensing electrodes abreast of guard electrodes are proposed to collimate the electric field lines and reduce noise. The kinetic model of the driven clip was based on a frictional driving equation revised using the Hammerstein–Wiener model to capture the nonlinearities and dynamic behavior variations with the duty ratios of driving signals. According to the kinetic model, the control strategies were decided and the velocity of the slider clip at any position could be estimated. Based on the velocity estimated using the Hammerstein–Wiener model, a velocity-adaptive Kalman filter was proposed. The prototype generated a maximum velocity of 18.9 mm/s, a mean steady-state error of 25 μm, and a settling time of 2.29 s for a 2.2 g weight driven vertically upwards to a distance of 25 mm.

A stick-slip linear piezoelectric actuator with mode conversion flexible hinge driven by symmetrical waveform

This paper presents a stick-slip linear piezoelectric actuator with mode conversion flexible hinge driven by symmetrical waveform. The mode conversion flexible hinge with a structure of chutes will make driving foot achieve lateral motion and make slider move steady. The chutes with different angles are analyzed by finite element method and the influence on the properties of the actuator is researched. The optimal angle can be found and a prototype is manufactured as well. In addition, an experimental system is established as well as a series of experiments. The output characteristic of the actuator is researched with different locking forces. The testing results indicate that the actuator can reach the maximum velocity of 18.84 mm s−1 and the maximum load can reach 360 g driven by the symmetrical waveform when the voltage is 100 Vp-p and frequency is 415 Hz. Moreover, the resolution of the actuator can achieve 50 nm under the locking force of 3 N when the voltage is 43 Vp-p and frequency is 415 Hz.

A linear piezoelectric actuator with high flexibility flexible mechanism designed by the bidirectional parasitic motion principle.

This paper proposes a piezoelectric actuator based on the parasitic motion principle which overcomes the disadvantage that piezoelectric actuators designed by the parasitic motion principle always sacrifice reverse directional performance for improving forward directional performance. The parasitic motion principle based piezoelectric actuator can use two flexible mechanisms to achieve bidirectional motion, but more assembly errors will be introduced. Therefore, the proposed actuator is designed to output bidirectional motion through one flexible mechanism. To this end, two mounting slots with high flexibility are specially designed for improving output displacement. The working principle and design process are elaborated, and experiments are conducted to prove the feasibility of the proposed actuator. The fabricated prototype can achieve a maximum velocity of 1.563 mm/s and 1.054 mm/s, a displacement resolution of 5.8 µm and 6 µm, an operating bandwidth of 1600 Hz and 1200 Hz, and a vertical load capacity larger than 500 g in forward and reverse directions.

A Linear Piezoelectric Stick-Slip Actuator via Triangular Displacement Amplification Mechanism

In the field of piezoelectric actuators, high speed piezoelectric stick-slip actuators have received considerable attention. A linear stick-slip piezoelectric actuator is proposed in this article, which combines asymmetric flexure hinge with triangular displacement amplification mechanism. The designed linear piezoelectric stick-slip actuator can achieve high speed at lower frequency. The configuration of the actuator and driving principle are illustrated and designed by theory and simulation. In order to study its performance, a prototype is fabricated, and an experimental system is established. The experimental results confirm that the maximum step efficiency of the prototype is 97.9 %. The maximum speed is 20.17 mm/s under the driving voltage of 100 V P-P , the driving frequency of 610 Hz and the locking force of 2.5 N. The maximum load capacity is 2.4 N under the locking force of 3.5 N. The proposed piezoelectric stick-slip actuator increases the step efficiency and improves the output speed at lower frequency.

Fuzzy control of the dual-stage feeding system consisting of a piezoelectric actuator and a linear motor for electrical discharge machining

Gap width is an important factor that affects material removal rate, surface finish, and machining stability in electrical discharge machining processes. This research is to develop a novel control method for a new hybrid positioning system which consists of a linear motor and a piezoelectric actuator for high-efficiency electrical discharge machining processes. In the new system, the linear motor provides the macro feeding while the piezoelectric actuator feeds the workpiece in micro scale at high frequency. To reduce the delay caused by separate movements of the linear motor and piezoelectric actuator, a new control algorithm was developed to synchronize the movements of the motor and piezoelectric actuator. A fuzzy control system was used to control the feeding process. Piezoelectric actuator position and its speed were selected as the fuzzy inputs, while the fuzzy output was the linear motor speed. Cutting experiments were conducted, and results show that the fuzzy system is more powerful than the conventional algorithm and the new algorithm with constant motor speed. An increase in material removal rate of 1.6 times was achieved using the proposed fuzzy control algorithm.

Application of piezoelectric actuator in series nano-positioning stage.

The existing nano-positioning stages are driven by the piezoelectric ceramics, which have features of high accuracy and resolution, but the traditional positioning stage could not meet the requirement of large working space because the displacement of the piezoelectric ceramics is only tens of microns. To solve the contradiction between high accuracy and large working space, a novel non-resonant piezoelectric linear actuator, which adopted the two parallel v-shaped stators as the double driving feet, was proposed, and both its working principle and structure were discussed in detail. The actuator was used to drive the positioning stage directly to obtain the performance of nano-positioning and large working stroke. The experiment results show that the resolution of the actuator is 0.015 μm, and its stable maximum motion speed is 17.4 mm/s, while the degree-of-freedom of step resolution of teach nano-positioning stage is 0.018 μm, 0.016 μm, and 0.3 μrad, respectively. Compared with the traditional positioning stage, the nano-positioning stage driven by the actuators directly also has excellent working stroke. The key performance of both high resolution and large working stroke of the nano-positioning stage was realized based on different motion modes of only one piezoelectric actuator.

A linear piezoelectric actuator with the parasitic motion of equilateral triangle flexure mechanism

A parasitic type piezoelectric actuator with an equilateral triangle flexure mechanism is proposed and investigated to achieve large-stroke linear motion. Right-circular flexure hinges with different thicknesses (t1 and t2) are utilized in the design of the equilateral triangle flexure mechanism which is able to generate parasitic motion. The working principle is analyzed and illustrated by the theoretical simulation and finite element method (FEM) simulation. A prototype is manufactured to study the performance of proposed parasitic type actuator, together with an experimental system. Experiments indicate that the maximum stepping displacement is ΔL = 9.00 μm in the case that input voltage Ue = 150 V; the minimum stepping displacement ΔL = 0.24 μm is achieved under Ue = 60 V; the maximum speed is Vs = 180 μm s−1; the largest output force is F = 106.3 g under that input frequency f = 1 Hz and Ue = 100 V. This study demonstrates the feasibility of symmetrical triangle flexure mechanisms in the design of parasitic type piezoelectric actuators with large working stroke.