Piezoelectric Stack Research Articles

Feedback switching control of a walking piezoelectric actuator for trajectory tracking

Abstract This paper proposes a feedback switching control (FSC) scheme for a Walking Piezoelectric Actuator (WPA) to track a time-varying trajectory. A WPA has two feet with each foot integrated with a clamp and shear Piezoelectric Stack Actuators (PSAs). The first foot pushes the stage translator a step forward when clamped while the second foot is reset and retracted; subsequently, ‘foot switching’ occurs; as a result, the second foot is clamped to push the translator to make a next step forward and the first foot is reset and retracted. To make sure that the translator is always controlled in closed-loop no matter which foot is clamped, the FSC scheme is proposed. It consists of a clamping waveform generator which converts the trajectory into control signals for the clamp PSAs of the two feet and a feedback controller which provides control signals for the two shear PSAs of the feet. Experimental results show that the proposed control scheme achieves a tracking error of 0.028 µm for a constant velocity trajectory, which is a 75% reduction compared to the 0.113 µm of waveform-based control with ILC compensation in literature.

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.

A compact structure and high-speed actuator designed by imitating the movement of wave

By imitating the natural phenomenon of waves pushing leaves, a compact novel wave-type piezoelectric actuator is proposed in this paper. Compared to traditional inchworm piezoelectric actuators, it combines the clamping unit and driving unit into an arc-shaped flexible driving foot (AFDF). Clamping and driving functions are realized by alternately controlling two ends of the AFDF using two piezoelectric stacks (PESs). One motion unit instead of two makes control simpler, the structure more compact and a faster movement speed. The static model of the AFDF is developed to characterize the mapping laws between structural dimensions and actuator amplification ratios, and the dynamic model represents the relationship between the control signals and move displacements, thus demonstrating the feasibility of the actuator. Finally, a prototype was fabricated, and a testing system was set up to conduct performance evaluations of its motion capabilities. At the driving frequencies of 370 Hz and 380 Hz, the maximum forward and reverse motion speeds can reach 4.345mm/s and 4.537mm/s, respectively. In the range of 0.1-10N, there is no significant change in motion speed, and it has good stability. Its resolution for forward and reverse motion can reach 106nm and 109nm, respectively.

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.

Enhanced velocity and weight-bearing capability of piezoelectric viscous-slip actuators utilising a pentagonal flexible hinge configuration

Abstract This research presents a novel piezoelectric stick–slip actuator design that capable of achieving higher speeds and handling heavier loads. This addresses the requirement for improved performance in the precision engineering industry. The symmetrical configuration of the pentagonal displacement amplification flexible hinge structure produces the transverse motion. The pentagon’s deformable range is sufficiently broad to amplify the piezoelectric stack’s output displacement and convert it into the desired transverse output displacement. To enhance the load capacity of the piezoelectric stick–slip actuator, one can raise the coupling displacement of the driving foot output. The flexible hinge construction undergoes finite element analysis, and the simulation results meet the design assumptions. The structure has been enhanced to mitigate the potential occurrence of jamming. A prototype was constructed and subjected to rigorous testing to examine its performance. The testing results indicate that the highest attainable velocity is 15.8 mm s−1, with an impressive precision of 35.9 nm. Despite being subjected to a load of 308 g, the output displacement remains steady at 0.376 mm s−1. A comparative study of experimental and finite element simulation findings demonstrates the feasibility of the structural design.

Backward motion suppression in space-constrained piezoelectric pipeline robots

In response to the current challenges of detecting micro pipelines, a micro pipeline robot based on the principle of piezoelectric inertia stick-slip drive was proposed in this paper, which can be effectively applied to the detection and maintenance of micro pipelines. However, during the analysis of the robot's displacement trajectory, it was observed that using inertial drive could cause the backward motion of the robot. This may adversely affect the accuracy and stability of the robot's operation within the micro pipelines. Therefore, a novel control method is derived from the original pipeline robot structure. By affixing piezoelectric sheets to the driving feet of the robot to adjust their deformation and subsequently employing collaborative control of piezoelectric sheets and piezoelectric stacks to regulate friction between the driving feet and the pipe wall, the backward motion of the robot was effectively mitigated. Compared to existing backward motion suppression methods, the approach proposed in this paper has a minimal impact on the actuator's size, allowing for flexible adaptation to various space-constrained applications, while also offering the advantage of a simple control strategy. After determining the structure and working principle, deformation analysis of the driving foot and dynamic simulation analysis of the driving system were conducted. These analyses provide insights into the relationship between mechanical and electrical parameters and output performance within the driving system, thereby validating the feasibility of the control method. Subsequently, a prototype was fabricated, and its output performance was tested. Results demonstrate that this control method can effectively suppress inertial backward motion, achieving a suppression rate close to 100 %. This research presents a novel idea and methodology for mitigating the backward motion of piezoelectric inertial stick-slip actuators with driving foot structures.

A novel double-arch piezoelectric energy harvester for capturing railway track vibration energy

This study introduces a novel piezoelectric stack energy harvester with a double-arched frame structure. This design effectively cushions impacts from track vibrations, thereby protecting the fragile piezoelectric stack made of brittle materials. The energy harvesting characteristics of the device are studied in detail through experiments and theoretical simulations. The harvester's output voltage depends on the external resistance and increases with higher resistance. The optimal resistance for the single X-direction piezoelectric stack is 340kΩ, which can output 0.519mW of power under a 3Hz frequency and an 8kN sinusoidal load. The Y-direction piezoelectric stack outputs 0.012mW, resulting in a total output of 1.050mW for the entire harvester. The output power of the harvester is positively correlated with the load vibration frequency, increasing rapidly for frequencies below 9Hz. The impact of load magnitude on the harvester's output shows a generally linear increase. In impact experiments, the single X-direction piezoelectric stack successfully lit 54 LEDs under a 5J energy impact, demonstrating the harvester's high power density and potential for practical applications.

Design and analysis of a piezo-actuated hydraulic micro-displacement amplifier with high bandwidth and large amplification ratio

Micro-displacement amplifiers show great potential for enhancing the performance of piezoelectric ceramic stacks. However, designing a compact micro-displacement amplifier with a high amplification ratio and broad bandwidth remains challenging. This article introduces a hydraulic micro-displacement amplifier driven by a piezoelectric ceramic stack with a large amplification ratio, high bandwidth, and eliminating parasitic displacement. Theoretical and simulation analyses are performed for the hydraulic micro-displacement amplifier, optimizing parameters such as edge thin ring thickness and spring stiffness. A prototype was fabricated and tested in a series of experiments. The experimental results demonstrate that, under steady-state conditions, the hydraulic micro-displacement amplifier achieves an amplification ratio of 26.12 with a standard deviation of 2.28. The maximum output displacement is 172.4 μm at 150 V, and the resonant frequency is 445 Hz under a 20 N load. This study provides a novel approach to designing micro-displacement amplifiers.

Equivalent Circuit of a Stacked Piezoelectric Cymbal Vibrator.

In order to provide a convenient and fast calculation method, the equivalent circuit of a novel stacked piezoelectric cymbal vibrator is studied. The equivalent circuit model of the piezoelectric stack is derived by combining the equivalent circuit models of the thin piezoelectric disk and electrode. The equivalent circuit of the cymbal structure is then derived. The equivalent circuit model of the stacked piezoelectric cymbal vibrator is further proposed. The output axial displacements and output forces of the cymbal vibrator under different excitation voltages are investigated using the equivalent circuit model. The effectiveness of the equivalent circuit has been verified by comparing it with the finite element method. Furthermore, the equivalent circuit method has a much faster calculation speed than the finite element method.

Investigation of Innovative High-Response Piezoelectric Actuator Used as Smart Actuator–Sensor System

This paper presents an experimental analysis of a high-response piezoelectric actuator system for the modular design of hydraulic digital fluid control units. It focuses on determining static and dynamic characteristics, forming the basis for developing a smart Industry 4.0 component that incorporates both actuator and sensor function. The design process examines the main challenges, advantages, disadvantages, and working principles to define parameters that impact the actuator’s behaviour and performance. The new piezoelectric actuator system features three piezoelectric stack actuators in series, enabling simultaneous actuation and sensing by applying and measuring the electrical voltage at each piezo element. The experimental setup and test methodology are explained in detail, revealing that the new design, combined with an appropriate open-loop or closed-loop control method, offers superior actuator stroke control, high stroke resolution, and a high-dynamic step response. This paper proposes a concept of a smart piezo actuator system focused on I4.0 and an actuator administration shell, integrated with 5G and RFID technology, which will allow automatic plug-and-play functionality and efficient interconnection, communication, and data transfer between the hydraulic valve and the piezoelectric actuator system.

Active friction-regulated inertia impact piezoelectric actuator

In inertia impact piezoelectric actuators, the phenomenon of high-frequency drive-induced back-stepping poses a significant limitation to their overall performance. The ultra-fast response time of the piezoelectric stack enables the resolution of this issue. This paper introduces an inertia impact piezoelectric actuator operating under a novel Dual-Stack Motion Mode (DCMM), diverging from the traditional operation in the Single-Stack Motion Mode (STMM) that involves a solitary piezoelectric stack (PES) for active friction control. A comprehensive description of the actuator's structure and its operational principles under DCMM is provided. By constructing and experimentally evaluating the actuator using a controlled variable approach, a comparative analysis of performance between DCMM and STMM across various scenarios including different inertial mass blocks, driving voltages, frequencies, and load conditions was conducted. The experimental results indicate that DCMM significantly enhances the actuator's output performance, achieving a maximum speed of 1142.79 μm/s and a stable single-step displacement of 0.5 μm. The actuator features a simple yet effective structure and driving mechanism, allowing for multiple driving modes through the assembly of different inertial masses, thereby providing a substantial competitive advantage in output performance. The feasibility of using DCMM to improve actuator performance is corroborated by both theoretical and experimental studies. The ultra-fast response of the piezoelectric stacks expands the operational bandwidth of the actuator, achieving a seamless integration of speed and precision.

Investigation of a cascaded piezoelectric transducer with cone horn for multi-mode power ultrasound application

To meet the ultrasonic application requirement of high power intensity and large mechanical displacement, a new theoretical method is used to study the multi-mode characteristic of the cascaded piezoelectric transducer with cone horn in this paper. Based on equivalent circuit and Kirchhoff’s law to obtain the frequency equation and vibration velocity expression of the transducer, then the resonance frequency and effective electromechanical coupling coefficient can be calculated, the velocity amplification ratio can be obtained in the meantime. This method is distinguish from traditional theoretical analysis, which avoids complex transformation of the multi-excitation sources in cascaded structure, and can calculate more performance parameters. The relationships between these performance parameters and the excitation position of the piezoelectric stack, the length and output end radius of the cone horn are analyzed and compared with the numerical simulation, and the optimized parameters of the transducer size are given. A transducer is manufactured for experimental test, the results show that the experimental value is in good agreement with theoretical calculation and finite element simulation. This work is expected to be used in the optimal analysis of the multi-mode transducer in high power ultrasonic field.

Design and performance analysis of an embedded amplified piezoelectric jetting dispensing valve

Abstract In order to satisfy the market's demand for high-consistency, micro-dispensing of colloids, an embedded lever-amplified piezoelectric dispensing valve based on flexure hinge is designed. This structure has stable jetting performance, strong reliability, and can achieve micro-dispensing of medium and low viscosity glue. Theoretical analysis shows that the output displacement of the piezoelectric stack can meet the displacement requirement of dispensing after being amplified by this amplification mechanism. And the output displacement and mode of the amplification mechanism are calculated and analyzed by simulation. The rationality of the simulation model is verified by experiments, and the effect law of driving voltage, signal duty cycle and working frequency on the mass of glue droplets is obtained. The results show that under the conditions of driving voltage 100 V, duty cycle 50%, glue supply pressure 0.6 MPa, working frequency 100 Hz, the consistency deviation of single dispensing amount is ± 2.01%, as a whole, 0.34-0.38 mg of uniform tiny glue dots can be obtained. The experimental results have verified the stability and micro-dispensing performance of the embedded lever amplification piezoelectric dispensing valve, providing reference for the subsequent application and research of jet dispensing.

Sub-micro-g resolution test of accelerometers based on tilt dynamic modulation in gravity field

Abstract Strategic-grade accelerometers play a pivotal role in various application fields and fundamental research. As the performance of accelerometers are improving rapidly, the requirements for test method have been raised. However, due to the influence of environmental noise, the test facility for accelerometers, especially when the resolution reaches sub-μg level, remains a challenge.
To address this limitation, this study introduces a resolution test facility based on tilt modulation in gravity field, driven by piezoelectric ceramic stacks. The input acceleration ranges from 30ng to 10μg, and the frequency is adjustable from 0.01Hz to 20Hz. Since the input acceleration oscillates at certain frequency, modulation & demodulation technology enables us to extract ultra weak signal out of relatively noisy background. With this facility, we test the resolution of commercial strong motion accelerograph, quartz flexure accelerometers, and homemade accelerometer based on levitated optomechanics, proving the reliability of this method. Our advancement in test method lay solid foundation for strategic-grade accelerometers, not only provides a minimal resolution test solution in the ng~μg range, but also provides a possible scheme of evaluating dynamic response characteristic with an ultra-low acceleration input in a considerable frequency range.

Development of a large stroke 3-DOF piezoelectric steering mirror for optical system

The steering mirrors and the focusing mechanisms are the key components of the optical system. Traditional steering mirrors driven by voice coil actuator or piezoelectric stack actuator have the disadvantages of short stroke, self-locking difficulty and poor structural reliability. These defects limit the performance of the steering mirrors and make it difficult to be compatible with the focusing mechanism. As a result, additional focusing devices are required in the optical system, which significantly increases the complexity of the system. To simplify the optical system, a large stroke three-degree-of-freedom (3-DOF) piezoelectric steering mirror (PSM) which can realize both light path adjustment and focus adjustment is proposed in this study. Two rotational degrees of freedom of the PSM are used to adjust the light path, and a translational degree of freedom is used to adjust the focus. The screwed-typed piezoelectric actuators (STPAs) are designed to drive the PSM by exciting the travelling wave. The feasibility of the operating principle and reliability of the proposed PSM have been verified by finite element simulation. A prototype of the PSM is fabricated and tested. The experimental results show that the PSM achieves rotational degrees of freedom around the x-axis, y-axis and translational degree of freedom along the z-axis with maximum ranges of ±0.17 rad, ±0.17 rad, and ±10 mm, respectively, meeting the application requirements of the optical systems. The resolutions of the two rotary motions of the PSM are 28 μrad, and 21 μrad, respectively, and that of the translational motion is 0.5 μm. Finally, the position adjustment and focusing operations of the image are demonstrated to validate the potential application of PSM in optical systems.

Geometrically nonlinear design of a rhombus-nested compliant amplification mechanism for use in precision actuators and sensors

A rhombus-nested compliant amplification mechanism is proposed for versatile usages of precision actuators and force sensors with an easy tuning of stiffness. Such a monolithically planar rhombus-nested compliant mechanism has the dual functions of two-stage displacement or force amplification by changing the input and output ports. It features a large ratio of inter-stage stiffness, thus resulting in an enhanced amplification ratio, load capacity and dynamic bandwidth. The geometrically nonlinear analytical equations of displacement amplification ratio and input stiffness are derived in the presence of pronounced axially-loaded stiffening and kinematic-arching effects based on the beam constraint model. It allows an insightful evaluation of geometrically nonlinear deformation behaviors sensitive to structural dimensions in a parametric way. Insights into geometrically nonlinear behaviors in the case of large-stroke and axially-loaded motions are discussed as well. A proof-of-concept prototype with embedded piezoelectric stacks is fabricated with the dimensions of 74mm × 60mm × 10 mm. The dual functions of precision actuator with amplified motion strokes and force sensor with enhanced sensitivity are experimentally demonstrated.

Comprehensive analysis of a butterfly-shaped piezoelectric shunting vibration absorber for robust vibration reduction and isolation: Theoretical and experimental validation

The Piezoelectric Shunting Vibration Absorber (PSVA) has garnered attention for its effectiveness in vibration control. This paper aims to propose a novel PSVA capable of simultaneously amplitude reduction and vibration isolation under various conditions. The PSVA consists of a butterfly-shaped link component and a piezoelectric stack, connected to the structure to be damped via bolts. Subsequently, an equivalent schematic diagram of the PSVA is established, and its equivalent stiffness is determined. Taking a single-degree-of-freedom structure as an example, considering the dynamic stiffness of the shunting circuit, a dynamic model of the electromechanical coupled system is developed, obtaining the system’s acceleration response and force transmissibility frequency response functions. Following this, experimental equipment is designed and fabricated, and the performance of the PSVA is tested under various excitation conditions. Finally, inspired by the experimental results, a segmented inductance circuit is designed and tested for its capability to broaden the vibration control bandwidth.

A 3-DOF Multi-Mode spherical actuator driven by cooperative piezoelectric units

Stick-slip piezoelectric actuators are widely used in precision engineering due to their high accuracy and small size. However, most of these actuators achieve multi-DOF motion by serially connecting multiple units, resulting in a non-compact structure and large assembly errors.To resolve this issue, this paper proposes a spherical actuator consists of a rotor and four drive units distributed around the rotor. Each drive unit comprises a piezoelectric shear stack and a piezoelectric plate. By utilizing the cooperation of piezoelectric elements, various driving modes with different performance and control complexity can be switched. To understand the influence of position and orientation of the drive units on the actuator’s performance, a dynamic model describing the behavior of the proposed actuator is established. This model takes into account the behavior of the drive units, friction and motion transmission between the drive units and the rotor, as well as transformation of coordinates. Finally, a prototype is developed based on the design, and the three-DOF motion performance of the prototype is tested under different drive modes. This work contributes to the mechanical design of multi-DOF precision positioning devices and the study of motion modes.

Research on Output Characteristics of a Non-Contact Piezoelectric Actuator’s Micro-Displacement Amplifying Mechanism

A non-contact piezoelectric actuator is proposed. The non-contact power transfer between stator and rotor is realized by pneumatic transmission, characterized by fast response, long life, compact structure, and easy miniaturization and control. The structure of the non-contact piezoelectric actuator is designed and its working principle is elucidated. The equation of the relationship between the output displacements of the non-contact piezoelectric actuator’s micro-displacement amplifying mechanism and the input displacements of piezoelectric stack is deduced, and the simulation analysis method of output displacement of the micro-displacement amplifying mechanism is established. Using the equation and the simulation analysis, the output characteristics of micro-displacement amplifying mechanism for the non-contact piezoelectric actuator and their changes along with the system parameters are investigated. The detailed process of optimal design of the micro-displacement amplifying mechanism is given by means of mathematical statistics. The prototype is made and the performance test is carried out. The correctness of the theoretical calculation and simulation analysis is verified by comparing the experimental values with the theoretical and simulated values of the output displacement of the micro-displacement amplifying mechanism. The results show that the initial angle of bridge structure I has an obvious effect on the output characteristics of the micro-displacement amplifying mechanism in the range of 5°–15°. When the lever’s rod length is 13 mm–15 mm, the bridge structure II’s rod length is 6 mm–7 mm, and the power arm length of bridge structure I’s driving lever is 5 mm–7 mm, the bridge structure II’s rod horizontal projection length is 5 mm–6 mm and the output displacement of the micro-displacement amplifying mechanism is larger. Through the optimal design, it is obtained that the bridge structure I’s initial angle is 8°, the lever’s rod length is 15 mm, the bridge structure II’s rod length is 7 mm, and the power arm length of bridge structure I driving lever is 5 mm, the bridge structure II’s rod horizontal projection length is 6 mm, and the simulated output displacement of the micro-displacement amplifying mechanism is 0.1415 mm. The prototype test reveals that as the input excitation displacement decreases, the error increases, while as the input excitation displacement increases, the error decreases. Specifically, when the input excitation displacement is 0.005 mm, the measured output displacement of the micro-displacement amplifying mechanism is 0.1239 mm, resulting in a 19.8% deviation from the theoretical value and a 12.44% deviation from the simulated value. The research work in this paper enriches the research achievements of non-contact piezoelectric actuators, and also provides a reference for designing small structure and large travel micro-displacement amplifying mechanisms of this type of actuator.

Dynamic responses of normal and partially failed piezoelectric stack actuators under sinusoidal voltages with DC biasing

Piezoelectric (PZT) stack actuators are widely used in many fields due to the advantages such as small stroke and high force output. However, failures of one or more PZT layers may exist in PZT stacks and then have influences on their performances. This paper investigates dynamic responses of normal and partially failed PZT stack actuators, in order to evaluate the influences of a failed layer at different positions and furthermore explore the rules, which is of great significance for understanding and improving the performances of partially failed PZT stack actuators. Firstly, a group of experiments were performed and responses of PZT stacks were obtained under sinusoidal voltages with DC biasing. Then a multiple degree-of-freedom (DOF) spring-mass system was built as a theoretical model which was verified by the experimental results to simulate output responses of PZT stack actuators. Based on that, the influences of a failed PZT layer at different positions in the stack were obtained by solving the model under various conditions. The results reveal that the farther the failed PZT layer is from the fixed end, the more significant the influences on the displacement or force output of the PZT stack are. Moreover, the rules of influences of a failed PZT layer at different positions were expressed as a general formula which can be used to better understand, evaluate or identify health conditions of PZT stack actuators.