Piezo Actuator Research Articles

Magnetically Driven Bionic Millirobots with a Low-Delay Automated Actuation System for Bioparticles Manipulation.

This paper presents a semi-automatic actuation system which can achieve bio-particles tracking, transportation, and high-precision motion control of robots in a microfluidic chip. This system is mainly applied in magnetically driven robots. An innovative manta ray-like robot was designed to increase stability of robots in a non-contaminated manipulation environment. A multilayer piezo actuator was applied to generate high-frequency vibration to decrease the friction between robots and the glass substrate. We also set up a user-friendly GUI (Graphical User Interface) and realized robot tracking and predetermined trajectory motion through excellent algorithms using Python and C++. In biotechnology, precise transportation of cells is used for the enucleation, microinjection, and investigation of the characteristics of a single cell. Being optimized, the parameters of the robot can effectively reach 10 µm in actuation precision and a maximum actuation speed of 200 mm/s.

Development and Research of Mathematical Models of Deployment of Mobole Parts of Transformable Space Construction. Part II

The process of deployment elements of constructions and adjustment of the radio-reflecting network of large-sized transformable space-based reflector is considered. The reflector consists of a frontal network, which is stretched on the power frame, cables, with which the front network is pulled to the rear network to set the desired shape of the reflecting surface. The problem of setting and determining the shape of the radio-reflective network is solved both in one plane and in three planes. In general, the task of adjusting the form of a radio reflecting reticle is solved by affecting the design of the actuators — the element of the control system. For the correct functioning of the reflector in orbit, it is necessary to control the shape of the reflecting surface by stretching the frontal network. For the formation and maintenance of the shape of the reflector, the frontal and rear networks are connecte d by cable-stayed reinforcements (tie rods). The cable connect the opposite network nodes. The cable system is the basis for building a sub-system. Miniature mechatronic modules can be located on each of the adju stable guys. To adjust the shape in one plane, the technique of flexible threads is applied. The possibility of changing the surface by simultaneous action of one or more actuators is sho wn. To adjust the shape in space, the membrane method described by the Laplace equation is used. The piezo actuator, DC motor and servomotor are considered as actuators for setting t he shape. As a mathematical model of the piezoactuator, the model of A. A. Nikolsky is considered. The system is solved taking into account rigid fixation of the reflector response. A comparison of the use of PID-controller and optimal controller. The structure of optimal control is revealed from the maximum principle. The arising two-point boundary value problem is solved by the methods of the steepest descent and Newton. It is shown that the use of optimal control can reduce the time of the transition process. A similar problem was solved for DC motor and servo motor. The advantage of using optim al control methods is shown for all actuators. The solution of the problem with the help of algorithm with correction of parameters of control structure is offered.

Stability Analysis of a Proximate Time Optimal Controlled Electrostatic Suspension System Using Piezo Actuator via Lyapunov Functional Approach

An electrostatic suspension of silicon wafer using proximate time optimal control has been successfully developed. In this system, the movable electrodes which are supplied by constant voltage and actuated by the piezoelectric (PZT) actuator are used instead of stationary electrodes like previous systems. The changing of the gap length between movable electrodes and the suspended object will create varying capacitances that can control the electrostatic forces. To overcome the problem of actuator saturation of the piezo actuator, a proximate time optimal control is used to stabilize the system. The system stability is theoretically investigated using Lyapunov’s function. The constant voltage supplying to the electrode is an important parameter, and it is also determined. The paper presents series of the simulation and experimental results that prove completely suspension of 4-inch silicon wafer without any mechanical contact.

Structural-parametric model of an electroelastic actuator for nanomechanics

Structural-parametric models, structural schemes are constructed and the transfer functions of electro-elastic actuators for nanomechanics are determined. The transfer functions of the piezoelectric actuator with the generalized piezoelectric effect are obtained. The changes in the elastic compliance and rigidity of the piezoactuator are determined taking into account the type of control. Keywords electro-elastic actuator, piezo actuator, structural-parametric model, transfer function, parametric structural scheme

Research of the Materials and Reinforcement Schemes Effects on a Mechanical Behavior Smart Structure with Embedded Piezo Actuators

The present work is devoted to the research of a helicopter blade segment stress-strain state. The segment was made of polymer composite materials with embedded piezoelectric actuators. The computational model of the blade segment takes into account the technological order of laying and the anisotropy of the reinforcing layers properties. The reinforcement schemes under consideration were [0°/90°], [45°/-45°], [0°/45°/-45°/90°]. The static strength margin was estimated using the criterion of maximum stresses. A layered analysis of the structure stress-strain state was carried out. It was shown that the most dangerous, determining the structure margin of safety, are normal interlayer stresses. It was found that the GFRP material and the structural reinforcement scheme [0°/90°], selected during the design, provide the greatest torsion angles.

Experimental Study for μ-class Control of Relative Position and Attitude for Synthetic Aperture Telescope Using Formation Flying Micro-satellites

Earth remote sensing from geostationary orbit (GEO) realizes high time resolution that is essential for disaster monitoring; however, the spatial resolution is commonly worse than observation from low Earth orbit (LEO). In order to achieve high-resolution and high-frequency GEO remote sensing, we have proposed a “Formation Flying Synthetic Aperture Telescope (FFSAT)” with multiple micro-satellites. The FFSAT can improve the spatial resolution by using the technique of a synthetic aperture, and therefore the relative positions and attitudes between the optical units of each satellite must be controlled with an accuracy better than 1/10 of the observation wavelength. In order to verify feasibility of such highly accurate control, μ-class control experiments were conducted by using COTS components, and numerical models of the components were constructed. Results of the experiments were integrated into a software simulator, and the μ-class formation flying control of the entire FFSAT system was numerically evaluated. In this simulation, highly accurate control was achieved with dual-stage actuators, which consist of piezo actuators and thrusters. The simulation results show that the formation can be controlled in μ-class accuracy under some assumptions.

A New Compliant Microgripper and Study for Flexure Hinges Shapes

This paper presents a new model for planar compliant microgripper with piezoelectric actuator. The microgripper body has two jaws and was designed with ten flexure hinges and was analyzed with Finite Element Analyses for three different shapes for flexure hinges: right circular, elliptic and corner filleted. Also, for each model the Finite Elements Method analyses were realized using three materials: brass, plastic, stainless steel and aluminum. A prototype made by brass with higher displacement flexure hinge shape was realized and characterized after comparison between Finite Elements Method analysis results. The microgripper used a stack type piezo actuator with 18 µm maximum stroke which closed the jaws simultaneous.

Experimental Characterisation of a High Dynamic Piezo Module for Resource-efficient Electrothermal Precision Ablation

In commercial micro electrical discharge machining (micro-EDM) a high process-stability is required, which is mainly determined by the dynamic characteristics of the kinematic system and the process control. To reduce inefficient processing such as open circuits, arcing and short circuiting and thereby increase removal-efficiency, an additional feed-system is required when using industrial EDM machines, since detailed knowledge about the kinematic parameters and the parameters of the electrical control system is limited and usually only comprehensible by analysing voltage and current characteristics.In this study, the dynoMat module as an additional system is presented, which is based on statistical analyses to control the gap between the tool electrode and the work piece by help of a piezo module. A separate monitoring system was realized for process analyses, which is used for fast and direct control of the piezo actuator. The maximal feed of the piezo actuator is less than the minimal step size of the basic feed system, which ensures the applicability in the EDM machine.The fundamental functionality of the dynoMat module is described in this study. Based on an experiment for machining micro-channels, it will be shown that the piezo module ensures a high process-dynamic and thus reduces the number of removal-inefficient pulses, which is verified by analyses of the voltage and current characteristics. From the experimental results it can be determined that the process-efficiency, characterised by the material removal rate and the tool wear rate, as well as the machining precision, characterised by the sparking-gap, are significantly improved.

Investigations of applications of smart materials and methods in fluid valves and drives

In the paper the investigations performed at the Division of Mechtronic Devices at Poznan University of Technology in the area of application of both: smart materials in electro-hydraulic and electro-pneumatic valves, and new methods to control of hydraulic servo drives, are presented. In a first part the piezo bender actuator is shortly described and its application in servo valve is proposed. This actuator replaced the torque motor in the available on the market servo valve. The new valve simulation model is proposed. The simulation and investigations results of the servo valve with the piezo bending actuator are included. In the next part of the paper the application of piezo tube actuator in flapper-nozzle pneumatic valve is described. The test stand and investigations results are presented. Later, in the article, the Model Following Control (MFC) and Fractional order Control (FoC) methods are described. Their application in control of electrohydraulic servo drive is proposed. Some investigations results are included in the paper, showing the advantages of those control methods.

Chatter stability of synchronized elliptical vibration assisted milling

This paper presents the dynamics to analyze the stability of ultrasonic elliptical vibration-assisted milling operations. The elliptical vibrations are delivered to the tool-tip with a piezo actuator integrated to tool holder at about 16.5 kHz with amplitudes of 10 μm and 5 μm in radial and tangential directions, respectively, with 90° phase difference. The chip thickness is modeled by considering the rigid body motion of the tool, regenerative and ultrasonic vibration amplitudes. The loss of tool contact with the workpiece at the ultrasonic vibration excitation frequency is considered in evaluating the directional factors in the regeneration of chip and process damping. The stability of the system is solved using the semi-discrete time-domain method and experimentally validated in milling Aluminum Al-7050 and AISI-1045 steel. It is shown that the ultrasonic vibrations can increase the stable depth of cuts if the periodic loss of contact between the tool and workpiece is maintained by selecting cutting speed, which is less than the tangential vibration velocity delivered by the actuator.

Recurrent-Neural-Network-Based Predictive Control of Piezo Actuators for Trajectory Tracking

Precise trajectory tracking of piezo actuators (PEAs) in real time is essential to high-precision systems and applications. However, the real-time tracking accuracy is rather limited as the PEA cannot be accurately modeled over large bandwidth and displacement range due to its nonlinearities. In this article, we propose to use recurrent-neural-network (RNN) to model the PEA system and develop a nonlinear predictive controller for PEA trajectory tracking. Considering the computation efficiency, first, an RNN is trained to model the nonlinear dynamics of the PEA system at high-frequency range. Then, a second-order linear model is proposed to account for the PEA low-frequency dynamics. Therefore, the PEA dynamics is modeled by the nonlinear model consisting of the RNN and the linear model, which is further used for nonlinear predictive control of the displacement. To increase the prediction accuracy, an unscented Kalman filter is designed to estimate the states of the nonlinear model. The nonlinear predictive control problem is solved based on a gradient descent algorithm, in which a method for analytically calculating the gradient of the cost function is developed. The proposed technique was experimentally implemented on a nano piezo stage for demonstration and its performance was compared with that of a PID controller. The accuracy of an iterative learning control approach was used as a benchmark for comparison as well. The results showed that high precision trajectory tracking of PEAs in real time can be achieved using the proposed technique.

Performance and flow analysis of small piezo pump

This study analyzed the characteristics of a small reciprocating pump with a reed valve driven by a piezo actuator. Two types of valves were fabricated and the effect of valve shape on the pump performance was investigated. The flow rate variation with the frequency was measured. The flow rate increased with the driving frequency until a certain frequency then started decreasing. There was a change in the flow rate increase at the resonance frequency of the piston membrane. Pressure fluctuations generated by pump operation play a significant role in determining the flow pattern. In particular, the valve stiffness and fluid inertia were found to be the major parameters for pressure waveform. The flow pattern of the outlet valve port was analyzed using the visualization technique. The flow pattern changed depending on the shape of the valve and driving waveform. The arm valve produced higher flow velocity than that of the cantilever valve. The flow behavior inside the valve port provided the comprehensive relationship to the effect of the valve shape on the pump performance.

A proposal of a piezo rotary positioning device: design, modeling and experiments

This article proposes a novel piezo rotary positioning device in which the rotation of the end-effector is generated by the friction driving mechanism principle. Two piezoelectric elements are utilized as motion sources. In this article, a complete study for design, finite element analysis, manufacturing, dynamic model, simulations and experiments is presented. The finite element analysis is applied to evaluate the designed device. Based on results of analysis on the finite element model, a prototype of device is manufactured. The driving resolutions of the end-effector of prototype can be achieved approximately 0.45 × 10–3 rad when the driving voltage of 80 V with frequency of 1 Hz is applied. By taking in account of the nonlinear hysteresis of piezo actuators as well as the complexity of friction mechanism between the end-effector and the movable platform, the predicted dynamic model of the end-effector angular displacement is achieved. Simulations and experiments results show that the prediction model is in good agreement with the actual model. This provides a useful solution for designing and controlling of such rotary devices. So, this rotary device can be controlled automatically by a computer and it has a great potential application in practice.

Data-driven vibrotactile rendering of digital buttons on touchscreens

Although mobile phones incorporate low-cost vibration motors to enhance touch-based interactions, it is not possible to generate complex tactile effects on their touchscreens. It is also difficult to relate the limited vibrotactile feedback generated by these motors to different types of physical buttons. In this study, we focus on creating vibrotactile feedback on a touchscreen that simulates the feeling of physical buttons using piezo actuators attached to it. We first recorded and analyzed the force, acceleration, and voltage data from twelve participants interacting with three different physical buttons: latch, toggle, and push buttons. Then, a button-specific vibrotactile stimulus was generated for each button based on the recorded data. Finally, we conducted a threealternative forced choice (3AFC) experiment with twenty participants to explore whether the resultant stimulus is distinct and realistic. In our experiment, participants were able to match the three digital buttons with their physical counterparts with a success rate of 83%. In addition, we harvested seven adjective pairs from the participants expressing their perceptual feeling of pressing the physical buttons. All twenty participants rated the degree of their subjective feelings associated with each adjective for all the physical and digital buttons investigated in this study. Our statistical analysis showed that there exist at least three adjective pairs for which participants have rated two out of three digital buttons similar to their physical counterparts.

A novel single butterfly stator piezo driver

In this paper, a new type of single butterfly piezo stick-slip linear actuator is proposed. The butterfly stator is driven by two symmetrical rectangular piezoelectric vibrators that are fixed at both ends to achieve a linear drive based on stick-slip motion. Based on the finite element method, the appropriate parameters of the rectangular piezoelectric vibrator with both ends fixed are obtained. Simulation analysis shows that the butterfly stator can increase the static friction force during the slow extension stage by driving the lateral movement of the foot, and reduce the dynamic friction force during the rapid contraction stage. A prototype was made and a series of experiments was conducted. Experimental results show that the maximum no-load motion velocity is about 3042 μm/s at a voltage of 100 V and a frequency of 1000 Hz; the maximum output force is 0.7 N at a voltage of 100 V and a locking force of 3.5 N; at a voltage of 60 V, At a frequency of 10 Hz and a locking force of 3.5 N, the minimum step displacement is about 0.77 μm.

Lights Out! Nano-Scale Topography Imaging of Sample Surface in Opaque Liquid Environments with Coated Active Cantilever Probes.

Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source, lenses and a four quadrant photodetector to amplify and measure the deflection of the cantilever probe. This optical method for deflection sensing limits the capability of AFM to obtaining images in transparent environments only. In addition, tapping mode imaging in liquid environments with transparent sample chamber can be difficult for laser-probe alignment due to multiple different refraction indices of materials. Spurious structure resonance can be excited from piezo actuator excitation. Photothermal actuation resolves the resonance confusion but makes optical setup more complicated. In this paper, we present the design and fabrication method of coated active scanning probes with piezoresistive deflection sensing, thermomechanical actuation and thin photoresist polymer surface coating. The newly developed probes are capable of conducting topography imaging in opaque liquids without the need of an optical system. The selected coating can withstand harsh chemical environments with high acidity (e.g., 35% sulfuric acid). The probes are operated in various opaque liquid environments with a custom designed AFM system to demonstrate the imaging performance. The development of coated active probes opens up possibilities for observing samples in their native environments.

The Actuation Mechanism of 3D Printed Flexure-Based Robotic Microtweezers.

We report on the design and the modeling of a three-dimensional (3D) printed flexure-based actuation mechanism for robotic microtweezers, the main body of which is a single piece of nylon. Our design aims to fill a void in sample manipulation between two classes of widely used instruments: nano-scale and macro-scale robotic manipulators. The key component is a uniquely designed cam flexure system, which linearly translates the bending of a piezoelectric bimorph actuator into angular displacement. The 3D printing made it possible to realize the fabrication of the cam with a specifically calculated curve, which would otherwise be costly using conventional milling techniques. We first characterized 3D printed nylon by studying sets of simple cantilevers, which provided fundamental characteristics that could be used for further designs. The finite element method analysis based on the obtained material data matched well with the experimental data. The tweezers showed angular displacement from 0° to 10° linearly to the deflection of the piezo actuator (0–1.74 mm) with the linearity error of 0.1°. Resonant frequency of the system with/without working tweezer tips was discovered as 101 Hz and 127 Hz, respectively. Our design provides simple and low-cost construction of a versatile manipulator system for samples in the micro/meso-scale (0.1–1 mm).

Strain Effects in YSZ Thin Films by Elastic Waves

The increase in direct current of yttria-stabilized zirconia (YSZ), which is an oxygen ionic conductor, by time-varying the strain produced by elastic waves was experimentally demonstrated. A piezo actuator was located outside of a furnace, and was used to introduce elastic waves into YSZ thin films deposited on a SiO2 bar in the furnace. Moreover, the effect of the elastic waves on the behavior of the direct current when constant voltage was applied to the YSZ films was observed. As strain increased, the direct current linearly increased at the rate of 1% for the stress application of 1 MPa at approximately 630 °C. This result considered to be due to the asymmetric strain effects in YSZ. Observed strain effects suggested the possibility of a new technology that could use elastic waves to improve the performance of high-temperature electrochemical devices, such as solid oxide fuel cells and solid oxide electrolysers.

High-Power Piezoelectric Tuner Driver for Lorentz Force Compensation

Superconducting Radio Frequency (SRF) cavities are used in modern accelerators to efficiently accelerate particles. When cavity is supplied with pulsed RF field it undergoes a mechanical strain due to the Lorentz force. The resulting deformation causes dynamic detuning whose amplitude depends on mechanical properties of the cavity, RF pulse rate and their profile. This effect causes considerable loss of acceleration performance. Therefore, it is usually actively compensated, most commonly with fast piezoelectric actuators. MicroTCA.4 standard was developed to accommodate control and data acquisition electronic systems of large-scale physics applications. The paper presents a design of high-power amplifier implemented using the MicroTCA.4 technology. The design of the driver was optimized for driving large-capacitance piezo actuators. Several possible architectures of the driver are presented and compared, taking into consideration the power and cooling limitations of MicroTCA.4. The design of a two-channel piezo driver and its initial laboratory test results are also discussed.

Cavity Simulator for European Spallation Source

European Spallation Source (ESS) will be the brightest neutron source in the world. It is being built in Lund, Sweden. Over 120 superconducting cavities will be installed in the facility, each regulated by an individual low-level radio frequency (LLRF) control system. To reduce the risk of testing the systems on real cavities, a cavity simulator was designed. It reproduces the behavior of superconducting cavities used in the medium and high beta sections of ESS's Linac. The high power RF amplifier and piezo actuators parameters are also simulated. Based on the RF drive and piezo control signals, the cavity simulator generates the RF signals acquired by the inputs of the LLRF control system. This is used to close the LLRF feedback loop in real time. The RF front end of the cavity simulator consists of vector modulators, down-converting circuits, and a set of fast data converters. The cavity response simulation is performed in a high-speed field programmable gate array logic by a dedicated firmware that was optimized to minimize the processing time. The device also generates clock, local oscillator, and the 704.42-MHz reference signals to allow for system tests outside of the accelerator environment. In this paper, the design of the cavity simulator, description of the algorithms used in the firmware, and measurement results of the device are presented.