Electromechanical Interaction Research Articles

Reliability in the era of electrification in aviation: A systems approach

With an increasing amount of electrification projects in aviation, reliability becomes a key question. Integrating electric and electronic equipment in areas that have been dominated by thermal machines poses big challenges and opportunities. This presentation provides insights into the methods used to determine the required reliability by assessing the whole system and exploring the electromechanical and environmental interactions that define the new requirements to be met. Finally, it will discuss the interlinked nature between safety and reliability in aviation.

A robust and computationally efficient finite element framework for coupled electromechanics

Electro-active polymers (EAPs) are increasingly becoming popular materials for actuators, sensors, and energy harvesters. To simulate the complex behaviour of actuators under coupled loads, particularly in the realm of soft robotics, biomedical engineering and energy harvesting, finite element simulations are proving to be an indispensable tool. In this work, we present a novel finite element framework for the simulation of coupled static and dynamic electromechanical interactions in electro-active polymeric materials. To model the incompressible nature of EAPs, a two-field mixed displacement–pressure formulation which, unlike the commonly-used mixed three-field and F-bar formulations, is applicable for both nearly and fully incompressible materials, is employed. For the spatial discretisation, innovative quadratic Bézier triangular and tetrahedral elements are used. The governing equations for the coupled electromechanical problem are solved using a monolithic scheme; for elastodynamics simulations, a state-of-the-art implicit time integration is adapted. The accuracy and the computational efficiency of the proposed framework are demonstrated by studying several benchmark examples in computational electromechanics which include simulations of a spherical gripper in elastostatics and a dielectric pump in elastodynamics. Such complex simulations clearly depict the advantages of the proposed finite element framework over the Q1/P0 and Q1-F-bar elements. Furthermore, the superiority of the proposed framework in accurately capturing complex coupled electromechanical interactions in thin electro-active polymeric shells is demonstrated by studying a thin helical actuator under different excitation frequencies and by reproducing buckling instabilities in thin semi-cylindrical and semi-spherical shells. With the ability to simulate various elastostatics and elastodynamics phenomena using a single finite element framework for bulk as well as thin dielectric elastomers while using coarse structured or unstructured meshes that can be readily generated using existing mesh generators, this novel framework offers a robust, accurate, and computationally efficient numerical framework for computational electromechanics.

Differentiating the effects of β-adrenergic stimulation and stretch on calcium and force dynamics using a novel electromechanical cardiomyocyte model.

Cardiac electrophysiology and mechanics are strongly interconnected. Calcium is crucial in this complex interplay through its role in cellular electrophysiology and sarcomere contraction. We aim to differentiate the effects of acute β-adrenergic stimulation (β-ARS) and cardiomyocyte stretch (increased sarcomere length) on calcium-transient dynamics and force generation, using a novel computational model of cardiac electromechanics. We implemented a bidirectional coupling between the O'Hara-Rudy model of human ventricular electrophysiology and the MechChem model of sarcomere mechanics through the buffering of calcium by troponin. The coupled model was validated using experimental data from large mammals or human samples. Calcium transient and force were simulated for various degrees of β-ARS and initial sarcomere lengths. The model reproduced force-frequency, quick-release, and isotonic contraction experiments, validating the bidirectional electromechanical interactions. An increase in β-ARS increased the amplitudes of force (augmented inotropy) and calcium transient, and shortened both force and calcium-transient duration (lusitropy). An increase in sarcomere length increased force amplitude even more, but decreased calcium-transient amplitude and increased both force and calcium-transient duration. Finally, a gradient in relaxation along the thin filament may explain the nonmonotonic decay in cytosolic calcium observed with high tension. Using a novel coupled human electromechanical model, we identified differential effects of β-ARS and stretch on calcium and force. Stretch mostly contributed to increased force amplitude and β-ARS to the reduction of calcium and force duration. We showed that their combination, rather than individual contributions, is key to ensure force generation, rapid relaxation, and low diastolic calcium levels.NEW & NOTEWORTHY This work identifies the contribution of electrical and mechanical alterations to regulation of calcium and force under exercise-like conditions using a novel human electromechanical model integrating ventricular electrophysiology and sarcomere mechanics. By better understanding their individual and combined effects, this can uncover arrhythmogenic mechanisms in exercise-like situations. This publicly available model is a crucial step toward understanding the complex interplay between cardiac electrophysiology and mechanics to improve arrhythmia risk prediction and treatment.

Features of mathematical modeling of electromagnetic processing of bulk materials

The article notes the features of applying the general equations of mathematical physics of an elliptic type in problems of modeling specific phenomena of the interaction of electromagnetic fields with elements and particles of an inhomogeneous dispersed medium. Such phenomena take place in installations for the separation of organic and mineral raw materials or the electromagnetic treatment of grain, seeds, etc. This is relevant, because the usual approach to the formulation of mathematical models in these problems, which is mainly based on differential equations of field theory in a simplified form, does not always adequately reflect the physical essence of the mentioned phenomena. Therefore, it limits the possibilities of an in-depth study of the influence of many factors determining the final results of separation and electromagnetic processing (EMP) processes. In the present work, an alternative approach is proposed based on the use of integral equations of field theory, which is based on the concept of primary and secondary field sources and can significantly reduce the order of the system of equations for the numerical implementation of algorithms for solving EMP problems, and the total amount of necessary computing resources. With this approach, local parameters of the field in interaction with individual particles and their influence on one another become available for calculation. This aspect is essential for determining the technological characteristics of EMP production installations. The presented mathematical model, in contrast to the common simplified approaches to determining the field parameters and ponderomotive forces acting on the particles of matter in the field, adequately reflects the physical laws of the distribution of potentials and electric field strength of real charges and induced sources. Due to this, it clearly reproduces the mechanism of the formation of the main components of mechanical forces acting on the polarized body from the side of the electric field as a whole, through the densities of elementary forces with which the field acts on surface charges induced in dielectric bodies in the field of action of the fields. Such a mathematical model is a universal and compact tool for analysis, design, and optimization of various installations and devices that use an electric field and its electromechanical interaction with the medium and individual bodies

Domain-wall pinning and defect ordering in BiFeO3 probed on the atomic and nanoscale

Electro-mechanical interactions between charged point defects and domain walls play a key role in the functional properties of bulk and thin-film ferroelectrics. While for perovskites the macroscopic implications of the ordering degree of defects on domain-wall pinning have been reported, atomistic details of these mechanisms remain unclear. Here, based on atomic and nanoscale analyses, we propose a pinning mechanism associated with conductive domain walls in BiFeO3, whose origin lies in the dynamic coupling of the p-type defects gathered in the domain-wall regions with domain-wall displacements under applied electric field. Moreover, we confirm that the degree of defect ordering at the walls, which affect the domain-wall conductivity, can be tuned by the cooling rate used during the annealing, allowing us to determine how this ordering affects the atomic structure of the walls. The results are useful in the design of the domain-wall architecture and dynamics for emerging nanoelectronic and bulk applications.

Analysis of cracked functionally graded piezoelectric material using XIGA

In this paper, an extended isogeometric analysis (XIGA) is presented to model the crack in functionally graded piezoelectric materials (FGPMs). The material properties of functionally graded piezoelectric material (FGPM) vary in an exponential manner along the length of the domain. To model a crack in the FGPM, the isogeometric analysis (IGA) approximation is enriched with the Heaviside and crack tip enrichment functions. Conventional four-fold enrichment functions of isotropic materials are employed to capture the crack tip singularity. To determine the fracture parameters, the domain form of electromechanical interaction integral is used. The accuracy of the proposed XIGA approach is highlighted by validating the several cracked homogeneous and functionally graded piezoelectric material against the analytical/reference solution available in the literature. Several example problems of cracked FGPM domain are solved by XIGA. The influence of material non-homogeneity parameter, loading combination parameter and crack length are examined on the stress intensity factors (SIFs) and electrical displacement intensity factor (EDIF).

A phase-field model for crack growth in electro-mechanically coupled functionally graded piezo ceramics

The analysis and design of piezoelectric actuators and sensors require the understanding of their failure due to the coupled electromechanical interactions. We present a phase-field model for damage to capture the brittle fracture associated with piezoelectric ceramics. A homogeneous PZT-4 specimen is used to demonstrate the interaction of various geometric parameters and polarization direction on the growth and arrest of a crack. In addition, the effect of holes and their arrangement on the fracture load is also discussed to assist in topology optimization. It was found that an ordered arrangement of holes could enhance the reliability of these ceramics more than a single hole with a similar amount of material removed. Finally, the functional gradation of material properties is modelled to understand the fracture in a piezoelectric composite containing PZT-4 and BaTiO3. The effect of the relative orientation of the material with respect to the polarization direction, on the fracture load is studied to improve the life of such piezoelectric composites. The resistance of fracture is found to be the maximum when the crack propagates into the tougher region of the domain. Whereas, the field enhances the fracture load irrespective of its magnitude when the gradation of material properties for the PZT-4/BaTiO3 ceramic is along the polarization direction. The aim of the study is to identify the factors that arrest crack propagation by analyzing the coupled system for the better design of piezoelectric sensors and actuators.

Electro-mechanical Modeling of Wind Turbine and Energy Storage Systems with Enhanced Inertial Response

In this paper, a coordinated control scheme for wind turbine generator (WTG) and supercapacitor energy storage system (ESS) is proposed for temporary frequency supports. Inertial control is designed by using generator torque limit considering the security of WTG system, while ESS releases its energy to compensate the sudden active power deficit during the recovery process of turbine rotor. WTG is modeled using the fatigue, aerodynamic, structure, turbulence (FAST) code, which identifies the mechanical loadings of the turbine and addresses electro-mechanical interactions in the wind energy system. A damping controller is augmented to the inertial control to suppress severe mechanical oscillations in the shaft and tower of the turbine during frequency supports. Furthermore, the result of small-signal stability analysis shows that the WTG-ESS tends to improve the stability of the whole multi-energy power grid. The major contributions of this paper will be validated by utilizing the proposed control method that combines the grid support capability and maintaining the integrity of structural design of the turbine for normal operations.

An electromechanical emulation-based study on the behaviour of wind energy conversion systems during short circuit faults

Short circuit faults are important phenomena and they may have severe effects on the power system components such as wind turbines (WTs). Although variable-speed WTs are taking the major share of new wind power installation, fixed-speed WTs are still a significant part of the existing wind power plants. Therefore, performance evaluation of these WTs during faults is a vital issue from the viewpoint of system stability, protection, and lifetime. In this paper, the effects of short circuit faults on the electrical and mechanical parts of fixed-speed WTs are investigated in simulation and in emulation using a new emulator. A comprehensive model of the WT that considers the aerodynamic, mechanical, and electromechanical interactions between the power system and the WT is used in the simulation and emulation studies. Results showed that short circuit faults not only have severe effects on the electrical parts of the WTs, but also they can generate vibrations on the mechanical parts such as blades and tower that can reduce their lifetime. Results show that how the fault type, its duration, voltage drop level, and grid strength can affect the system performance. Since the developed emulator considers all main aspects of a WT and their interactions, it can be used as a tool to develop more economical and better performing WT.

3D structured self-powered PVDF/PCL scaffolds for peripheral nerve regeneration

Piezoelectric materials providing in situ electrical stimulation (ES) without applying an external chemical or physical supporting open new frontiers for future bioelectric therapies. As a “smart” material which can promote cell differentiation and proliferation due to instantaneous ES, polyvinylidene fluoride (PVDF) holds great promise in tissue engineering. In this study, a porous PVDF/polycaprolactone (PCL) composite nerve tissue engineering scaffold was manufactured by a simple cast/annealing-solvent displacement method. It was found that the blend of PCL with PVDF could simultaneously improve mechanical properties, biocompatibility, as well as biodegradation. When Rat Schwann cells (RSCs) are cultured on top of the scaffolds, the electromechanical interactions stimulate cell proliferation and differentiation. After being implanted into the 15-mm defect rat sciatic nerve model for 4 months, the PVDF/PCL group exhibits significant electrophysiological, morphological and functional nerve restoration. Overall, our findings highlight the potential of an effective and user-friendly piezoelectric scaffold for peripheral nerve regeneration due to its inherent electroactivity and favorable biocompatibility.

Optical mapping of electromechanics in intact organs.

Optical mapping has become a widely used and important method in cardiac electrophysiology. The method typically uses voltage-sensitive fluorescent dyes and high-speed cameras to image propagation of electrical waves. However, signals are highly susceptible to artifact caused by motion of the target organ. Consequently, cardiac optical mapping is traditionally performed in isolated, perfused organs whose contraction has been pharmacologically arrested. This has prevented optical mapping from being used to study interactions between electrical and mechanical motion. However, recently, a number of groups have developed methods to implement cardiac optical mapping in the presence of motion. These methods employ two basic strategies: (1) compensate for motion by measuring it or (2) ratiometry. In ratiometry, two signals are recorded from each site. The signals have differing sensitivity to membrane potential, but common motion artifact, which can be cancelled by taking the ratio of the two signals. Some methods use both of these strategies. Methods that measure motion have the additional advantage that this information can be used to quantify the organ’s mechanical function. Doing so enables combined “electromechanical mapping,” which allows optical study of electromechanical interactions. By allowing recording in the presence of motion, the new methods open the door to optical recording in in-vivo preparations. In addition, it is possible to implement electromechanical optical mapping techniques in organ systems other than the heart. For example, it was recently shown that optical mapping of slow wave propagation in the swine stomach is feasible. Such studies have the potential to uncover new information on the role of dysrhythmic slow wave propagation in gastric motility disorders. Impact statement Electrical and mechanical functions in the heart are bidirectionally coupled, yet are usually studied separately because of the different instrumentation technologies that are used in the two areas. Optical mapping is a powerful and widespread tool for imaging electrical propagation, but has traditionally required mechanical function to be arrested. Recently new methods have been devised that enable optical mapping to be performed in beating hearts and also to simultaneously quantify mechanical function. These new technologies promise to yield new information about electromechanical interactions in normal and pathological settings. They are also beginning to find application in other organ systems such as the gastrointestinal tract where they may provide new insight into motility disorders.

A Novel Control Technique to Reduce the Effects of Torsional Interaction in Wind Turbine System

Though power electronic interface is prone to higher failure in wind turbine system (WTS), the failure downtime due to mechanical and generator malfunctioning is highest. Unforeseen electromechanical interactions caused due to dynamic load variation and transient torsional stress is a major cause for failures in the drive-train and generator in WTS. In the literature, several techniques, such as generator speed feedback, stress damping controller, and virtual inertia damping controller, have been proposed in regards to the problem stated. Though the techniques are promising, the factor of independent control of natural frequency and damping ratio has not been considered. This paper proposes speed difference damping controller (SDDC), which is a novel and improved control technique that decouples the two above-mentioned parameters and improves the electromechanical performance significantly, reducing the torsional vibration of the driveline. The controller gains are designed based on the derived two-inertia system model that is used to represent the first natural frequency torsional vibration. In this paper, theoretical analysis and control design of SDDC are articulately addressed. A detailed comparative study of SDDC is carried out with respect to the other proposed controllers. The modeled WTS is examined for the first torsional natural frequency under two extreme wind-input conditions, i.e., sinusoidal wind condition, wind impulse, and grid dynamic, and one real-wind test case scenario. For the experimental verification, a multimass test rig operating at the critical speed and dynamic impulse load variation is analyzed in parts.

Design, electromechanical simulation, and control of a variable speed stall-regulated PMSG-based wind turbine

ABSTRACTWind turbines are complicated systems including different aerodynamic, mechanical, electrical, and control aspects. A few research works have considered the detailed models which include all aspects of the wind energy systems. These models can be used to cope with the disadvantages of the simple models that neglect some important features and electromechanical interactions. However, in these studies, the existing aerodynamic designs were used which limits the studies to available designs. In the present study, the site-specific blades of a variable-speed stall-regulated wind turbine are firstly designed then employed in simulation with detailed models. Since the stall-regulated turbines do not require active aerodynamic devices to control the captured power in high wind speeds, they are appropriate alternatives to be used in small-scale turbines. Hence, this type of turbine is studied in the present paper and the details of blade design and electromechanical simulation are discussed. The controllers are designed for maximum power point tracking in low and moderate wind speeds and limiting the captured power using the stall phenomenon in high wind speeds. The performance of the turbine with the designed blades is investigated in different wind conditions including simple hub-height and turbulent wind profiles, generated by TurbSim software.

Modelling of reduced electromechanical interaction system for aircraft applications

Rotational systems such as aircraft engine drivetrains are subject to vibrations that can damage shafts. Torsional vibrations in drivetrains can be excited by the connection of loads to the generator due to electromechanical interaction. This problem is particularly relevant in new aircraft because the drivetrain is flexible and the electrical power system (EPS) load is high. To extend the lifespan of the aircraft engine, the electromechanical interaction must be considered. Since real-time constants of the electrical and mechanical systems have very different magnitudes, the simulation time can be high. Furthermore, highly detailed models of the electrical system have unnecessary complexity for the study of electromechanical interactions. For these reasons, modelling using reduced order systems is fundamental. Past studies of electromechanical interaction in aircraft engines developed models that allow the analysis of the torsional vibration, but these are difficult to implement. In this study, a reduced order electromechanical interaction system for aircraft applications is proposed and validated using experimental results. The proposed system uses a reduced drivetrain, simplified EPS, and sensorless measurement of the vibrations. The excitation of torsional vibrations obtained is compared with past studies to prove that the reduced order system is valid for studying the electromechanical interactions.

Relations between the piezoelectric performance and quality factors in a corundum-containing composite

A composite containing Lead Zirconate Titanate (PZT)-type ferroelectric and corundum ceramics is studied as a material with a combination of a relatively high piezoelectric activity, significant piezoelectric anisotropy and a large mechanical quality factor. Experimental data on four piezoelectric coefficients d33∗, e33∗, g33∗, and h33∗ are first analysed for a composite with almost equal volume fractions of corundum inclusions mc and air pores mp. The presence of both corundum inclusions and air pores of similar volume fractions in the composite strongly influences relationships between its piezoelectric coefficients and quality factors. Maxima of g33∗ and h33∗, electromechanical coupling factor kt∗ and resonator figure of merit M∗ are observed in a narrow mc range (0.09<mc < 0.14), and this has no analogs among other piezo-active composites with two ceramic components. New experimental results on the piezoelectric performance are interpreted in terms of a microstructural model whereby the electromechanical interaction between the ferroelectric ceramic/corundum regions in the porous ferroelectric ceramic medium (either poled or non-poled) plays an important role. The studied composite is of interest as an active element of piezoelectric sensors and other piezotechnical transducer devices.

Equations of the Local Gradient Electromagnetothermomechanics of Polarizable Nonferromagnetic Bodies with Regard for Electric Quadrupole Moments

We formulate a complete system of relations of the local gradient electromagnetothermomechanics of electrically conductive nonferromagnetic polarizable solid media. The nonlocal character of the constitutive relations of the proposed mathematical model is explained by the presence of electric quadrupole moments in the polarization current. As a result of taking into account these moments, the space of parameters of the thermodynamic state of the body is expanded by including a pair of additional conjugate parameters, namely, the quadrupole moment and the gradient of the vector of electric-field intensity. It is shown that the developed model takes into account the electromechanical interaction for materials with high level of symmetry (isotropic materials) and describes the flexoelectric and thermopolarization effects. We also present the key system of equations for a physically and geometrically linear medium.

Shot-Noise-Limited Nanomechanical Detection and Radiation Pressure Backaction from an Electron Beam.

Detecting nanomechanical motion has become an important challenge in science and technology. Recently, electromechanical coupling to focused electron beams has emerged as a promising method adapted to ultralow scale systems. However the fundamental measurement processes associated with such complex interaction remain to be explored. Here we report a highly sensitive detection of the Brownian motion of μm-long semiconductor nanowires (InAs). The measurement imprecision is found to be set by the shot noise of the secondary electrons generated along the electromechanical interaction. By carefully analyzing the nanoelectromechanical dynamics, we demonstrate the existence of a radial backaction process that we identify as originating from the momentum exchange between the electron beam and the nanomechanical device, which is also known as radiation pressure.

Normal‐Mode Splitting in a Weakly Coupled Electromechanical System with a Mechanical Modulation

AbstractNormal‐mode splitting (NMS) is one of the most significant manifestations of strongly coupled systems. Here, NMS is shown to occur in a weakly coupled electromechanical system. In this system, an exponentially enhanced electromechanical coupling is obtained by periodically modulating the electromechanical interaction and the mechanical spring constant. Under the mechanical modulation, an obvious NMS can occur in the fluctuation spectra of the mechanical oscillator's displacement and the output field. Besides, the Stokes and anti‐Stokes fields can also display an obvious NMS. Interestingly, the Stokes field can be changed from full absorption to significant amplification, and the anti‐Stokes field can also be enhanced significantly. Another novel feature of the results is that the intensity between the two peaks in NMS is almost zero, which means that the two peaks can be well resolved in experiments. This work presents an effective method for the generation of a well‐resolved NMS in a weakly coupled system.

Особенности электромеханических взаимодействий в МЭМС с латеральным смещением непараллельных электродов в режиме с контролируемым напряжением

Особенности электромеханических взаимодействий в МЭМС с латеральным смещением непараллельных электродов в режиме с контролируемым напряжением

Coaxial Nickel–Poly(vinylidene fluoride trifluoroethylene) Nanowires for Magnetoelectric Applications

Magnetoelectric (ME) composite materials, in which a coupling between magnetostrictive and piezoelectric effects is achieved, are potential candidates for multifunctional devices where the interplay between the electrical, magnetic, and mechanical properties of these structures can be fully exploited. Nanostructured composites are particularly interesting because of the enhancement of ME coupling expected at the nanoscale. However, direct studies of ME coupling in nanocomposites by scanning probe microscopy (SPM) techniques are rare because of the complex interplay of forces at play, including those arising from electrostatic, magnetic, and electromechanical interactions. In this work, the ME coupling of coaxial nickel–poly(vinylidene fluoride trifluoroethylene) [Ni–P(VDF-TrFE)] composite nanowires (NWs), fabricated by a scalable template-wetting-based technique, is studied using a systematic sequence of SPM techniques. Individual ME NWs were subjected to an electric field sufficient for ferroelectric poling in piezoresponse force microscopy (PFM) mode, while magnetic force microscopy (MFM) was used to measure localized changes in magnetization as a result of electrical poling. Kelvin probe force microscopy measurements of the surface potential were conducted to eliminate for the effect of contact potential differences during these measurements. An inverse, static, ME coupling coefficient of ∼1 × 10–11 s m–1 was found in our coaxial nanocomposite NWs, comparable to other types of planar composites studied in this work, despite having an inferior piezoelectric-to-magnetostrictive volume ratio. The efficient ME coupling in our coaxial NWs is attributed to the larger surface-to-volume interfacial contact between Ni and P(VDF-TrFE) and is promising for future integration into ME composite devices such as magnetic field sensors or energy harvesters.