Analytical and Experimental Studies of Flexoelectric Beam Control

2016 ◽  
Author(s):  
Xufang Zhang ◽  
Huiyu Li ◽  
Hornsen Tzou
Keyword(s):  
Electric Field ◽  
Design Parameters ◽  
Analytical Prediction ◽  
Probe Radius ◽  
Flexoelectric Effect ◽  
Control Moment ◽  
Probe Location ◽  
Afm Probe ◽  
Fixed End ◽  
Tip Displacement

Flexoelectricity includes two effects: the direct flexoelectric effect and the converse flexoelectric effect, which can be respectively applied to flexoelectric sensors and actuators to monitor structural dynamic behaviors or to control structural vibrations. This study focuses on the converse flexoelectric effect and its application to dynamic control of cantilever beams analytically and experimentally. In the mathematical model, a conductive atomic force microscope (AFM) probe with an external voltage is used to generate an inhomogeneous electric field driving the flexoelectric beam. The electric field gradient leads to an actuation stress in the longitudinal direction due to the converse flexoelectric effect. The actuation stress results in a bending control moment to the flexoelectric beam since the stress in the thickness is inhomogeneous. In order to evaluate the actuation effect of the flexoelectric actuator, the flexoelectric induced tip displacement is evaluated when the mechanical force is assumed zero. With the induced control moment, vibration control of the cantilever beam is discussed and the control effect is evaluated. Flexoelectric control effects with different design parameters, such as AFM probe location, AFM probe radius and flexoelectric beam thickness, are evaluated. Analytical results show that the optimal AFM probe location for all beam modes is close to the fixed end. Besides, thinner AFM probe radius and thinner flexoelectric beam enhance the control effects. Laboratory experiments are also conducted with different probe locations to validate the analytical predictions. Experimental results show that the induced tip displacement decreases when the input location moves away from the fixed end, which is consistent with the analytical prediction. The studies provide design guidelines of flexoelectric actuations in engineering applications.

Comparison of Flexoelectric and Piezoelectric Actuating of Beams

2020 ◽  
Author(s):  
Mu Fan
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Vibration Control ◽  
Case Studies ◽  
Field Gradient ◽  
Patch Size ◽  
Flexoelectric Effect ◽  
Control Moment ◽  
Modal Force ◽  
Afm Probe

Abstract The flexoelectric and piezoelectric effect on the actuating of a cantilever beam are compared in this study to explore how the size-dependent effect could affect the application of the flexoelectric effect. An AFM (atomic force microscopy) probe is used to generate the electric field in the flexoelectric patch, significant electric field gradient is induced. The electric field, distribution of control moment, induced modal force and the vibration control efficiency in terms of transverse displacements are analyzed in case studies. Analytical results show that the control moment of flexoelectric effect highly concentrates at the location of the AFM probe due to the inhomogeneous electric field, which shrink the effect area of flexoelectric patch size. The distribution of the flexoelectric control moment is an impulse function and the distribution of the piezoelectric control moment is a step function, which results to the flexoelectric modal force strongly affected by the electric field gradient while the piezoelectric modal force highly depends on the patch size. For the flexoelectric actuating, decreasing the AFM probe radius can increase the electric field gradient and induce larger modal force. The thickness effect of flexoelectric patch depends on the electric field gradient and the control moment arm, and in the current study, increasing the patch size, the induced flexoelectric modal force increases slightly. Case studies on vibration control show that both the flexoelectric actuating and piezoelectric actuating could generate larger transverse tip displacement with increasing the patch size. This study proves that the flexoelectric actuating can provide effectively actuating and control effect to engineering structures when the size decreases.

Flexoelectric Actuation and Vibration Control of Ring Shells

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Hornsen Tzou ◽  
Bolei Deng ◽  
Huiyu Li
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Design Parameters ◽  
Internal Stresses ◽  
Control Force ◽  
Elastic Ring ◽  
Dirac Delta ◽  
Control Moment ◽  
Afm Probe

The converse flexoelectric effect, i.e., the polarization (or electric field) gradient-induced internal stress (or strain), can be utilized to actuate and control flexible structures. This study focuses on the microscopic actuation behavior and effectiveness of a flexoelectric actuator patch laminated on an elastic ring shell. An atomic force microscope (AFM) probe is placed on the upper surface of the flexoelectric patch to induce an inhomogeneous electric field resulting in internal stresses of the actuator patch. The flexoelectric stress-induced membrane control force and bending control moment regulate the ring vibration and their actuation mechanics, i.e., transverse and circumferential control actions, are, respectively, studied. For the transverse direction, the electric field gradient quickly decays along the ring thickness, resulting in a nonuniform transverse distribution of the induced stress, and this distribution profile is not influenced by the actuator thickness. The flexoelectric-induced circumferential membrane control force and bending control moment resemble the Dirac delta functions at the AFM contact point. The flexoelectric actuation can be regarded as a localized drastic bending to the ring. To evaluate the actuation effect, dynamic responses and controllable displacements of the elastic ring with flexoelectric actuations are analyzed with respect to design parameters, such as the flexoelectric patch thickness, AFM probe radius, ring thickness, and ring radius.

Dynamic Flexoelectric Actuation and Vibration Control of Beams

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Mu Fan ◽  
Bolei Deng ◽  
Hornsen Tzou
Keyword(s):  
Experimental Data ◽  
Dynamic Control ◽  
Longitudinal Direction ◽  
Bottom Surface ◽  
Internal Stresses ◽  
Control Effect ◽  
Flexoelectric Effect ◽  
Control Moment ◽  
Fixed End ◽  
And Control

A flexoelectric cantilever beam actuated by the converse flexoelectric effect is evaluated and its analytical and experimental data are compared in this study. A line-electrode on the top beam surface and a bottom surface electrode are used to generate an electric field gradient in the beam, so that internal stresses can be induced and applied to distributed actuations. The dynamic control effectiveness of the beam is investigated with a mathematical model and is validated by laboratory experiments. Analyses show that the actuation stress induced by the converse flexoelectric effect is in the longitudinal direction and results in a bending control moment to the flexoelectric beam since the stress in the thickness is inhomogeneous. It is found that thinner line-electrode radius and thinner flexoelectric beam lead to larger control effects on the beam. The position of the line-electrode on the top surface of the beam also influences the control effect. When the line-electrode is close to the fixed end, it induces a larger tip displacement than that is close to the free end. Analytical results agree well with laboratory experimental data. This study of flexoelectric actuation and control provides a fundamental understanding of flexoelectric actuation mechanisms.

Vibration control with the converse flexoelectric effect on the laminated beams

2019 ◽  
Vol 30 (17) ◽  
pp. 2556-2566 ◽  
Author(s):  
Mu Fan ◽  
Hornsen Tzou
Keyword(s):  
Electric Field ◽  
Dynamic Response ◽  
Mass Density ◽  
Open Loop ◽  
External Loading ◽  
Laminated Beam ◽  
Loop Control ◽  
Flexoelectric Effect ◽  
Control Moment ◽  
Displacement Based

Flexoelectric material under inhomogeneous electric field can be used as control and actuation systems in engineering applications based on the converse flexoelectric effect. The electric field gradient can be generated by using the atomic force microscope probe placed on the top of flexoelectric layer and coupled with a bottom electrode surface. The induced membrane force and the corresponding control moment in turn influence the dynamic response of the beam. The response of a laminated cantilever beam with initial vibration caused by an external loading is studied. The beam was modelled as a laminated beam to explore the influence of flexoelectric layer stiffness on the dynamic response of the structure. When the flexoelectric layer has higher Young’s modulus and mass density than the elastic layer, with increasing the thickness of the flexoelectric layer, the tip displacement of the laminated beam decreased rapidly. Through case studies, the optimal control positions for each mode of vibration were found to be dependent on the flexoelectric layer properties as well. A displacement-based feedback control was introduced to avoid overactuation caused by open-loop control.

Static Nano-Control of Cantilever Beams Using the Inverse Flexoelectric Effect

2011 ◽  
Author(s):  
S. D. Hu ◽  
H. Li ◽  
H. S. Tzou
Keyword(s):  
Electric Field ◽  
Cantilever Beam ◽  
Mechanical Strain ◽  
Effective Control ◽  
Bottom Surface ◽  
Control Force ◽  
Dirac Delta ◽  
Flexoelectric Effect ◽  
Afm Probe ◽  
Converse Piezoelectric Effect

Flexoelectricity, an electromechanical coupling effect, exhibits two opposite electromechanical properties. One is the direct flexoelectric effect that mechanical strain gradient induces an electric polarization (or electric field); the other is the inverse flexoelectric effect that polarization (or electric field) gradient induces internal stress (or strain). The later can serve as an actuation mechanism to control the static deformation of flexible structures. This study focuses on an application of the inverse flexoelectric effect to the static displacement control of a cantilever beam. The flexoelectric layer is covered with an electrode layer on the bottom surface and an AFM probe tip on the top surface in order to generate an inhomogeneous electric field when powered. The control force induced by the inverse flexoelectric effect is evaluated and its spatial distribution resembles a Dirac delta function. Therefore, a “buckling” characteristic happens at the contact point of the beam under the inverse flexoelectric control. The deflection results of the cantilever beam with respect to the AFM probe tip radius indicate that a smaller AFM probe tip achieves a more effective control effect. To evaluate the control effectiveness, the flexoelectric deflections are also compared with those resulting from the converse piezoelectric effect. It is evident that the inverse flexoelectric effect provides much better localized static deflection control of.flexible beams.

Flexoelectric Actuation and Vibration Control of Ring Shells

2015 ◽  
Author(s):  
Bolei Deng ◽  
Huiyu Li ◽  
Hornsen Tzou
Keyword(s):  
Electric Field ◽  
Vibration Control ◽  
Contact Point ◽  
Flexible Structures ◽  
Bending Moment ◽  
Delta Function ◽  
Elastic Ring ◽  
Dirac Delta ◽  
Probe Radius ◽  
Afm Probe

The converse flexoelectric effect that the gradient of polarization (or electric field) induces internal stress (or strain) can be utilized to control the vibration of flexible structures. This study focuses on the microscopic actuation behavior and effectiveness of a flexoelectric actuator patch on an elastic ring. An atomic force microscope (AFM) probe is placed on the upper surface of the patch to implement the inhomogeneous electric field inducing stresses inside the actuation patch. The flexoelectric membrane force and bending moment, in turn, actuate the ring vibration and its actuation effect is studied. Actuator’s influence in the transverse and circumferential directions is respectively evaluated. For the transverse direction, the gradient of the electric field decays quickly along the ring thickness, resulting in a nonuniform transverse distribution of the induced stress and such distribution is not influenced by the patch thickness. The flexoelectric induced circumferential membrane force and bending moment resembles the Dirac delta function at the AFM contact point. The influence of the actuator can be regarded as a drastic bending on the ring. To evaluate the actuation effect, dynamic response of controllable displacements of the elastic ring under flexoelectric actuation is analyzed by adjusting the geometric parameters, such as the thickness of flexoelectric patch, AFM probe radius, ring thickness and ring radius. This study represents a thorough understanding of the flexoelectric actuation behavior and serves as a foundation of the flexoelectricity based vibration control.

scholarly journals Magnetic Driven Two-Finger Micro-Hand with Soft Magnetic End-Effector for Force-Controlled Stable Manipulation in Microscale

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 410
Author(s):  
Dan Liu ◽  
Xiaoming Liu ◽  
Pengyun Li ◽  
Xiaoqing Tang ◽  
Masaru Kojima ◽  
...  
Keyword(s):  
Magnetic Force ◽  
Force Feedback ◽  
Soft Magnetic ◽  
End Effector ◽  
Force Microscopy ◽  
System A ◽  
Atomic Force ◽  
Afm Probe ◽  
End Effectors ◽  
Fixed End

In recent years, micromanipulators have provided the ability to interact with micro-objects in industrial and biomedical fields. However, traditional manipulators still encounter challenges in gaining the force feedback at the micro-scale. In this paper, we present a micronewton force-controlled two-finger microhand with a soft magnetic end-effector for stable grasping. In this system, a homemade electromagnet was used as the driving device to execute micro-objects manipulation. There were two soft end-effectors with diameters of 300 μm. One was a fixed end-effector that was only made of hydrogel, and the other one was a magnetic end-effector that contained a uniform mixture of polydimethylsiloxane (PDMS) and paramagnetic particles. The magnetic force on the soft magnetic end-effector was calibrated using an atomic force microscopy (AFM) probe. The performance tests demonstrated that the magnetically driven soft microhand had a grasping range of 0–260 μm, which allowed a clamping force with a resolution of 0.48 μN. The stable grasping capability of the magnetically driven soft microhand was validated by grasping different sized microbeads, transport under different velocities, and assembly of microbeads. The proposed system enables force-controlled manipulation, and we believe it has great potential in biological and industrial micromanipulation.

scholarly journals Dynamic Line Rating—An Effective Method to Increase the Safety of Power Lines

2021 ◽  
Vol 11 (2) ◽  
pp. 492
Author(s):  
Levente Rácz ◽  
Bálint Németh
Keyword(s):  
Expert System ◽  
Electric Field ◽  
High Voltage ◽  
Low Frequency ◽  
Power Line ◽  
Power Lines ◽  
Design Parameters ◽  
Monitoring Methods ◽  
Limit Value ◽  
Potential Applications

Exceeding the electric field’s limit value is not allowed in the vicinity of high-voltage power lines because of both legal and safety aspects. The design parameters of the line must be chosen so that such cases do not occur. However, analysis of several operating power lines in Europe found that the electric field strength in many cases exceeds the legally prescribed limit for the general public. To illustrate this issue and its importance, field measurement and finite element simulation results of the low-frequency electric field are presented for an active 400 kV power line. The purpose of this paper is to offer a new, economical expert system based on dynamic line rating (DLR) that utilizes the potential of real-time power line monitoring methods. The article describes the expert system’s strengths and benefits from both technical and financial points of view, highlighting DLR’s potential for application. With our proposed expert system, it is possible to increase a power line’s safety and security by ensuring that the electric field does not exceed its limit value. In this way, the authors demonstrate that DLR has other potential applications in addition to its capacity-increasing effect in the high voltage grid.

Fabrication of Ionic Polymer Metal Composite Actuator with Palladium Electrodes and Evaluation of its Bending Response

2009 ◽  
Vol 1190 ◽  
Author(s):  
Takuma Kobayashi ◽  
Takeshi Kuribayashi ◽  
Masaki Omiya
Keyword(s):  
Electric Field ◽  
Sample Length ◽  
Metal Composite ◽  
Ionic Polymer Metal Composite ◽  
Ionic Polymer ◽  
Palladium Electrode ◽  
Wide Range ◽  
Polymer Metal ◽  
Bending Response ◽  
Tip Displacement

AbstractWe built up the way of fabricating IPMC actuator with palladium electrodes and we found that it showed large bending response than Au-plated IPMC actuator. An ionic polymer-metal composite (IPMC) consisting of a thin perfuorinated ionomer membrane, electrodes plated on both faces, undergoes large bending motion when a small electric field is applied across its thickness in a hydrated state. The characteristics of IPMC are ease of miniaturization, low density, and mechanical flexibility. Therefore, it is considered to have a wide range of applications from MEMS sensor to artificial muscle. However, there are problems on IPMC. First, its mechanical and electric characteristics have not been clarified because of the complex mechanism of the deformation. Second, it is high-priced because most of IPMC actuators use gold or platinum as electrodes. In order for IPMC actuator to be widely put to practical use, we should solve these problems. Hence, this research focuses on fabrication of IPMC actuator with palladium electrode, which is cheaper than gold or platinum, and evaluation of its mechanical properties such as its tip displacement. We fabricated IPMC consisting of a thin Nafion® membrane, which is the film with fluorocarbon back-bones and mobile cations, sandwiched between two thin palladium plates. The surface resistivity was 2.88±0.18Ω/sq., so it could be said to be enough small. Then, we observed its cross section by using FE-SEM. As a result, palladium plates were evenly coated and its thickness was about 30μm. Also, we carried out an actuation test for two kinds of IPMCs: one was fabricated by using Nafion®117 (thickness 183μm), the other was by Nafion®115 (thickness 127μm). In this test, the relationship between voltage (0˜4V) across its thickness and tip displacement for the cantilevered strip of the IPMC was measured. Then we found that IPMCs showed large bending motion under a low electric field. When Nafion®117 sample was subjected to voltage of 1.5V, the ratio of the tip displacement to the sample length was 0.35, which was lager bending than Au-plated IPMC actuator, whose ratio of the tip displacement to the sample length was 0.12 [1]. When Nafion®115 sample was applied to 1.5V, the ratio of the tip displacement to the sample length was 0.22. Then, we found that Nafion®117 bended in a larger way than Nafion®115. Reference [1]Sia Nemat-Nesser and Yongxian Wu,”Comparative experimental study of ionic polymer-metal composites with different backbone ionomers and in various cation forms”, Journal of Applied Physics,93,5255 (2003)

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