Electromechanical Energy Conversion Research Articles

ОПТИМИЗАЦИЯ ГЕОМЕТРИИ ЗУБЦОВОЙ ЗОНЫ ГИСТЕРЕЗИСНОЙ МУФТЫ ЗАПОРНОЙ АРМАТУРЫ НЕФТЕПРОВОДА

Актуальность работы связана с поиском новых эффективных технических решений в области электроприводов запорной арматуры трубопроводного транспорта нефтепродуктов на основе использования гистерезисного принципа электромеханического преобразования энергии и новых магнитотвердых материалов. Цель: выявить оптимальную геометрию зубцовой зоны электромагнитной гистерезисной муфты на базе сплава Fe-Cr-Co для получения максимального вращающего момента на основе анализа процессов перемагничивания гистерезисного слоя. Методы: экспериментальные методы исследования магнитных характеристик магнитотвердых материалов с использованием оригинальных лабораторных установок; имитационное моделирование в программе ANSYS MAXWELL; теоретические методы анализа электромагнитного поля. Результаты. Для гистерезисных муфт на базе сплава Fe-Cr-Co 22Х15КА получены и проанализированы зависимости вращающего момента от геометрических параметров зубцовой зоны муфты. Для оценки эффективности использования гистерезисного материала авторами введен коэффициент использования гистерезисного слоя по тангенциальной составляющей магнитного поля. В программе ANSYS MAXWELL разработана имитационная модель электромагнитной гистерезисной муфты с неподвижной обмоткой управления, учитывающая параметры сплава Fe-Cr-Co 22Х15КА. С помощью разработанной модели получены оптимальные значения геометрических размеров зубцовой зоны с целью достижения максимального вращающего момента при фиксированных габаритах и весе. Сделан вывод о том, что вариант электропривода трубопроводной запорной арматуры с гистерезисной муфтой и асинхронным электродвигателем благодаря простоте его реализации, возможности регулирования и ограничения момента в широком диапазоне температур и окружных скоростей можно рассматривать как перспективную альтернативу электроприводам с частотным управлением и тиристорными регуляторами.

Scientific and Technical Basis of Application of Nanostructured Materials Science and Nanoelectronics in Systems of Electromechanical Energy Converters for Special Purposes

We consider the current state of a completely new area of science; microsystem electromechanics. Тhe wide spectra of its practical applications and prospects for further development are analyzed. We discuss in detail two main directions of creating micro- and nanoelectromechanical converters as basic elements of microsystem electromechanics: “top down” and “down top.” We also describe the main technological methods in constructing basic functional elements of microsystem electromechanics, areas of their application in traditional and new technologies (information and computer technologies, medicine, aerospace, rocket and artillery systems, etc.). At the same time, we discuss some key issues of generalized physical and mathematical modeling of microelectromechanical and nanoelectromechanical systems (MEMS and NEMS). A new generalized approach is proposed to study dynamic and energy characteristics of MEMS and NEMS as complex dynamic systems with binary conjugate subsystems. Based on proposed theoretical principles and models, the possibilities of studying electrophysical characteristics of biological nanostructures have been considered.

The collusion of flexoelectricity and Hopf bifurcation in the hearing mechanism

How do the weak sound waves get amplified in a cochlea? This deceptively simple question has attracted a fair amount of attention and several creative mechanisms have been proposed that purport to understand how the inner ear’s hair cells actively collude to achieve the requisite sensitivity, frequency selectivity, range and nonlinear amplification. Some of the proposed mechanisms target the nature of the mechanoelectric transduction mechanism while others adopt a more dynamical systems approach and focus on the fact that stereocilia of the hair cells operate on the verge of an instability phenomenon—the so-called Hopf bifurcation. In this work, we propose a physics-based model to understand how flexoelectricity, a universal electromechanical coupling that exists in all dielectric substances, facilitates the mechanics of the active motion of hair bundles. A key feature of our model is that we eschew a “black-box” approach, and all parameters are well-defined physical quantities such as membrane bending modulus, geometrical characteristics and others. Furthermore, the model is derived from the well-accepted principles of mechanics and soft matter physics. While the role of flexoelectricity in the hearing mechanism has been noted before, we show for the first time that flexoelectricity is an essential ingredient in inducing the Hopf bifurcation state considered responsible for several highly nonlinear and peculiar features of the hearing mechanism. We find that the biomembranes’ bending modulus and the intracellular charge concentration (which for instance could represent K+ or Ca2+) are the two key control parameters that significantly impact the stability of the system and hence the hearing mechanism. Our work highlights the importance of flexoelectricity, confirms earlier assertions that the cochlea amplifies the acoustic stimuli through its exceptional electromechanical energy conversion property, and provides insights into how physical properties such as biomembranes’ bending modulus impact the performance of the hearing system.

Large-Scale Synthesis of MoS2 Monolayer Using Na-Containing Facilitators for Electromechanical Energy Harvesting

The reliable synthesis method of large-area, continuous 2D MoS2 layer has been demanded for applications of next generation electronic and optoelectronic devices. Here, Na2S is introduced as a novel growth promoter to control over the grain size of full area coverage MoS2 monolayer. With Na2S solution-coated film, the nucleation density increases by the formation of reduced phase like NaMoO3-x. At the same time, additional sulfur from Na2S film affects the nucleation and growth mechanism resulting in changes of the domain geometry from triangular nanosheets to centimeter scale films. Moreover, by modulating the concentration of Na2S solution, the grain size of MoS2 monolayer has been changed. Thus, we propose a new approach of modulating nucleation density and grain morphology in polycrystalline full-coverage MoS2 films by using growth promoter, Na2S. The successful large-scale monolayer has been characterized for electromechanical energy conversion. As a result, a peak output of 253mV and 22nA was obtained when a strain of 0.26% was applied. Our results suggest the potential of large-scale 2D layer as an electromechanical energy converter.

Research on Driving Circuit Improvement of Coilgun

Theoretically, the energy conversion efficiency of the synchronous induction coil launcher (SICL) can reach 100%, but at present, the test data show that the highest current is only a little higher than 20%, which shows that the efficiency of the coil launcher has a lot of room for improvement. In this paper, three improved schemes are proposed for the topology of the traditional crowbar circuit based on the pulse capacitor to improve the electromechanical energy conversion efficiency of the electromagnetic coil launcher. They are main circuit breaking, crowbar break-off circuit, and crowbar circuit with inductor, respectively. In order to verify the feasibility of the above three methods, a five-stage coil launcher was simulated and analyzed. Then, based on the model, three improved circuits were calculated and analyzed by the finite-element simulation software. The results show that all of the three methods can improve the efficiency of energy conversion to a certain extent. Both the first and second methods have limited effect on increasing efficiency. In addition, they need to add some expensive equipment such as circuit breaker. So, they are not recommended. The third way of increasing an inductor in the crowbar circuit could increase the muzzle velocity and efficiency obviously. The muzzle velocity increased from 30.6 to 35 m/s. The effect of armature capture is reduced which is worthy of recommendation.

Improved Active and Reactive Control of a Small Wind Turbine System Connected to the Grid

This paper deals with the interconnection of a small wind turbine with the low voltage distribution grid and the implementation of an improved control scheme, which also serves educational purposes. Initially the subsystems—wind turbine, rectifying bridge, interleaved boost converter, three-phase inverter, interconnection inductors, lifting transformer, filtering capacitors—are investigated, in order to explain their selection, based on the LEMEC (Laboratory of Electromechanical Energy Conversion, Department of Electrical Engineering, UoP) educational policy. Afterwards, the three-phase inverter control scheme, which is responsible for controlling its input voltage (voltage of the DC Bus) and consequently the active power, as well as the reactive power injected into the grid (VQ control) is analyzed. This is accomplished through DQ transformation and PI controllers which are responsible for generating the appropriate reference signals, to generate the required Space Vector Pulse Width Modulation (SVPWM) pulses to drive the semiconductor switches of the inverter. In addition, it is explained how this particular control method can compensate reactive power in the grid, even in apnea, by automatically charging the DC Bus. Finally, simulation and experimental results are given to prove the proposed control method effectiveness.

Review of Soft Computing Models in Design and Control of Rotating Electrical Machines

Rotating electrical machines are electromechanical energy converters with a fundamental impact on the production and conversion of energy. Novelty and advancement in the control and high-performance design of these machines are of interest in energy management. Soft computing methods are known as the essential tools that significantly improve the performance of rotating electrical machines in both aspects of control and design. From this perspective, a wide range of energy conversion systems such as generators, high-performance electric engines, and electric vehicles, are highly reliant on the advancement of soft computing techniques used in rotating electrical machines. This article presents the-state-of-the-art of soft computing techniques and their applications, which have greatly influenced the progression of this significant realm of energy. Through a novel taxonomy of systems and applications, the most critical advancements in the field are reviewed for providing an insight into the future of control and design of rotating electrical machines.

A New Perspective on the PM Vernier Machine Mechanism

Permanent magnet vernier (PMV) machines have attracted more and more attention for their merits of high torque density and simple structure. Also, the principle of electromechanical energy conversion is the most common way to investigate the PMV machine by calculating back electromotive force and electromagnetic torque. In this paper, a new perspective on the mechanism of PMV machines based on the Maxwell stress tensor method is presented to deepen the insight into the reason why the force on the rotor of a PMV machine is larger than that of an surface permanent magnet (SPM) machine. Based on the finite element analysis (FEA) method, three machines with exactly the same rotor are analyzed and compared, namely 24-slot/20-pole SPM, 12-slot/20-pole surface PMV, and 6-slot/20-pole split-tooth PMV machines. The radial and tangential flux densities and force distributions along the airgap are illustrated. The influence of pole ratio on the performance of PMV machines is also investigated. It is shown that the improvement of tangential flux density in the PMV machine plays a primary role in the higher torque density, which shows a promising way to improve the torque density of machines.

Estimation of energy density of PMN-PT ceramics utilizing mechanical stress

Present study introduces an indirect measurement of energy density of (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMN-PT) ceramics under compressive stress and electric field. The method works analogous to Olsen cycle which is a demonstration of a novel cycle converting mechanical energy into electrical energy. A large amount of electro-mechanical energy conversion can be achieved via this method. The ceramics were investigated under 0–75 MPa and 1–15 kV/cm of applied mechanical stress and electric field, respectively. A maximum energy density of 68 kJ/m3/cycle was achieved in 0.7PMN-0.3PT ceramic. The obtained result is significantly greater than that of linear piezoelectric phenomena.

Research on the Efficiency Optimization Control of the Regenerative Braking System of Hybrid Electrical Vehicle Based on Electrical Variable Transmission

Electrical variable transmission (EVT) is a novel electromechanical energy converter that can be applied in hybrid electrical vehicle (HEV). In this paper, the hybrid electrical vehicle based on EVT (EVT-HEV) and the efficiency optimization strategy of regenerative braking system (RBS) is studied. Firstly, this paper analyzes the dynamic coupling mode of EVT-HEV and establishes the expression of the dynamic coupling relationship between EVT and the engine. Then, four different braking modes including two novel ones are divided. Next, a hierarchical controller is proposed in which the rule-based control strategy is used for braking mode switching and neural network algorithm is used for the optimal efficiency control for the system. The simulation of the control strategy is carried out under New European Driving Cycle (NEDC) based on the joint platform of CRUISE and MATLAB software. And the results indicate that the proposed strategy can improve the performance of RBS in EVT-HEV. Thus the research in this paper can bring a new theoretical foundation for the application of EVT in HEV and is of great significance to enrich the energy management strategies of EVT-HEV.

The development of the mathematical model of a nonlinear electrical circuit with an independent controllable electromechanical energy converter

The nonlinear electric circuit with an independent controllable electromechanical energy converter is the object of this research. Such circuit nowadays has large practical use in many vehicles. The developers of these vehicles conduct frequent research and calculations of these circuits during the design stage. The one of the problems of such circuits is the complexity of its calculations. The circuit has a few nonlinear elements: an electric motor, a battery, and a supercapacitor. Numerical calculations of such circuit would be extremely complex and require huge computational power. As a result, a lot of existing models created for conducting research of such circuits are oversimplified, which leads to inaccuracy of energy calculations. During this research the mathematical model of the circuit under consideration was created to be as simple as possible with the accuracy being acceptable for energy calculations. In order to achieve this, the existed models were examined: parameters, which have weak impact on electromagnetic processes, were neglected while momentary effect, such as the impulse form of energy transformation, and additional energy losses were taken under consideration. Thereafter the computer model of the nonlinear electric circuit with an independent controllable electromechanical energy converter was created to meet the accuracy requirements for energy calculations and to be reasonably complex at the same time. The obtained model is more accurate for energy calculations than most of existing models due to the accounting of the impulse working modes of the electrical converter and electromagnetic losses of the electromechanical converter. Also due to the neglecting of some poser supply parameters that have slight effect on the energy losses this model is less complex then other accurate models of the circuit under consideration. Thus, the obtained model is optimal for the energy calculations of the nonlinear electric circuit with an independent controllable electromechanical converter.

Differential evolution applied to line-connected induction motors stator fault identification

The three-phase induction motor is the main machine used for electromechanical energy conversion, due to its consolidated construction characteristics. As a consequence of its great importance and industrial application, researches in the fault identification area are constantly conducted to reduce the maintenance rate and the losses, during the productive process, caused by undesirable downtime. In this sense, this work proposes an alternative methodology, based on the differential evolution algorithm, to identify stator short-circuit fault in induction motors connected directly to the electrical grid, using voltage and current signals in time domain. The differential evolution algorithm is used to estimate the electrical parameters of the induction motor, based on the model of the equivalent electrical circuit. Stator fault is identified by calculating the variation of the estimated magnetizing inductance of the motor under no fault condition. The proposed method is validated through experimental tests on 1 HP and 2 HP motors under conditions of load torque variation and unbalanced voltages.

Guest Editorial Emerging Electric Machines and Drives for Smart Energy Conversion

Energy conversion is one of the key steps for human utilizing the energy. In particular, as the key component for electromechanical energy conversion, electric machines play a significant role and greatly promote the development of modern civilization. Actually, the conventional types of electric machines, namely DC machines, induction machines, and synchronous machines, as well as surface permanent-magnet (SPM) machines and inserted-PM (IPM) machines, have been widely applied for various aspects in human lives. In recent years, emerging electric machines, including the double-salient type, hybrid-excitation type, PM memory type, magnetic-gearing type, PM vernier type, advanced magnetless type, multiport type, and some newly developing types, are proposed for new application occasions such as electric vehicles (EVs), electric ships, electric aircraft, electric robotics, wind power generation, unmanned propulsion systems, and so on. In addition, the corresponding advanced control strategies have presented for electric drives, which include the direct torque control (DTC), field oriented control (FOC), finite control set model predictive control (FCS-MPC), fault-tolerant control, and sensorless control. Thus, emerging electric machines and drives take active roles for applications with more electric or full electric. This special section brings new findings of electric machines and drives on their topologies, structures, analysis approaches, advanced control strategies, and new applications.

Research and analysis of force and moment of the cascade asynchronous electric drives.

In the article, the research of force and the moment in the cascade asynchronous electric drives is provided and the analysis of the received decision is carried out. As an object of a research, the special types of electric drives with asynchronous motors possessing glad advantages in comparison with single-engine electric drives were selected. These are optimum mass-dimensional and energetic indices, the improved technological parameters allowing reaching big limits of regulation of rotational speed and the electromechanical moment, and the value of the moment can remain within rated value even in case of small rotational speeds or changes of the direction of movement. For optimum design of such types of electric drives and more exact and correct regulation and the researched parameters of force and the moment on a shaft of an electric drive, it is necessary to realize new approaches to a research and calculation. The carried-out analysis showed that the most optimum method of determination of force and the moment is the method based on electromechanical conversion of energy. The parameters received as a result of a research have necessary accuracy in comparison with the experimental data. The analysis of the conducted research shows that the received decision will allow improving quality, technical and economic indices of difficult technological processes of such industries as oil and gas branch, the heavy industry and mechanical engineering, a pulp-and-paper industry and others.

The calculation of the magnetic circuit of salient-pole electric machines

This article deals with the development of theories of electromechanical energy converters with a lower level of external magnetic fields, a new method for calculating magnetic circuits and electromagnetic processes in the ferromagnetic space of electromechanical converters of electro technical complexes, oriented to the use of modern computer facilities, are new methods of differential investigation of the influence of various parameters of electric machines on the level of external magnetic fields. Beyond the engineering methods for calculating the magnetic circuit, it remains to determine the magnetic field in the grooves of the rotor, the relationship of this field with the field of the ferromagnetic part of the core. The article presents the results of research methods and calculations of magnetic circuits and modes of operation of explicitly salient pole machine. Developed a fairly simple method of calculating harmonic of the magnetic field in the groove of the rotor and the interpolar space, which provides the definition of the parameters of the magnetic field at the given points without calculation of this field in the whole region.

Large electro-mechanical energy conversion in PZT-PNN ceramics

In this study, an indirect measurement of energy density of lead zerconate titanate- lead nickel niobate or PZT-PNN ceramics utilizing mechanical stress was performed. The method works similarly to Olsen cycle, which is a large amount of electro-mechanical energy conversion can be achieved. A maximum energy density of 170 kJ/m3/cycle was found in 0.6PZT-0.4PNN ceramic under 0–100 MPa and 1–15 kV/cm of applied mechanical stress and electric field, respectively. The obtained result is much higher than the results reported in existing studies of piezoelectric materials utilizing direct piezoelectric effect.

Piezoelectric stacked transducer evaluation and comparison for optimized energy harvesting

The primary focus of this research is on the application and optimization of direct piezoelectric effect in energy harvesting from low frequency mechanical vibrations such as from roadway traffic. The specific research aim is to evaluate the various stacked PZT transducers in their mechanisms and performance on effective electromechanical energy conversion. Piezoelectric power output has been determined based on understanding of the fundamental concepts in composites (1:3 bi-phasic) and stacked transducers. Several property structure relations are evaluated by various experimental methods including the utilization of electrodynamic test systems. Power evaluation is compared among several samples in order to understand the most efficient configuration utilizing PZT ceramics. Power density as function of applied mechanical force and pressure, are calculated and compared with the experimental results which yield good agreement. Three types of stacked PZT transducers were compared and systemically tested for their electromechanical power conversion performance. The 1:3 composite stacked PZT transducer was found to be the best performer in term of power density per unit active volume, the specially designed and fabricated stacked PZT transducers (UTSA stacked sample) were found to have the highest power density per transducer volume, 0.615 mW/mm3, measured at 965 kN/m2 (140 PSI), among the three types studied (1:3 composite stacked sample, assembled stacked sample and the commercially sourced stacked sample). The pressures and forces used were based on the traffic flow monitoring and federal and state regulations.

Comparative Analysis of Two and Four Current Loops for Vector Controlled Dual-Three Phase Permanent Magnet Synchronous Motor

Dual three-phase (DTP) permanent magnet synchronous motors (PMSMs) are specialized machines which are commonly used for high power density applications. These machines offer the merits of high efficiency, high torque density, and superior supervisor fault tolerant capability compared to conventional three-phase AC-machines. However, the electrical structure of such machines is very complicated, and as such, control becomes challenging. In conventional vector controlled DTP-PMSMs drives, the components of the dq-subspace are associated with electromechanical energy conversion, and two currents, i.e., Id and Iq belonging to this subspace, are used in feedback-loops for control. Such orthodox control methods can cause some anomalies e.g., the voltage source inverter’s (VSI) dead time effect and other nonlinear factors, and can induce large harmonics. These glitches can be greatly alleviated by the introduction of the two-extra current loops to directly control the currents in Z1Z2-subspace in order to suppress the insertion of harmonics. In this paper, two approaches—one with two-current loops and other with four-current loops—for vector controlled DTP-PMSMs are investigated with the aid of different MATLAB-based simulations. Furthermore, in the paper, the influence of additional current loops is quantified using simulation-based results.

In‐Plane Ferroelectricity in Thin Flakes of Van der Waals Hybrid Perovskite

Collective ferroic orders in van der Waals (vdW) crystals are receiving increasing attention in 2D materials research. The interplay between spatial quantum confinement and long-range cooperative phenomena not only broadens the horizon of fundamental physics, but also enables new device paradigms and functionalities built upon vdW heterostructures. Here, the in-plane ferroelectric properties in thin flakes of vdW hybrid perovskite bis(benzylammonium) lead tetrachloride are studied. The ordering of electric dipoles along the layer plane circumvents the depolarization field and preserves the ferroelectricity down to one unit-cell thickness or two vdW layers at room temperature. The superior performance of the electromechanical energy conversion is demonstrated by exploiting its in-plane piezoelectricity. The successful isolation of ferroelectric order in atomically thin vdW hybrid perovskite paves the way for nonvolatile flexible electronic devices with the cross-coupling between strain, charge polarization, and valley degrees of freedom.

Direct Torque Control of Six-Phase Induction Motor With a Novel MRAS-Based Stator Resistance Estimator

Any mismatch between the real and tuned values of the stator resistance ( $R_s$ ) leads to a degraded performance of the direct torque control (DTC) strategy. The underestimation of $R_s$ causes an error in the stator flux and torque estimations, thereby weakening the DTC performance; however, an overestimation of $R_s$ can make the DTC unstable. The main objective of this paper is to present a novel estimator based on the model reference adaptive system (MRAS) for online estimation and tracking of $R_s$ in the DTC of six-phase induction motors (6PIMs). Voltage and current vectors of 6PIM are mapped into $\alpha -\beta$ , $z_1-z_2$ , and $o_1-o_2$ subspaces, where only the $\alpha -\beta$ components are related to electromechanical energy conversion. The proposed technique uses additional degrees of freedom, i.e., the $z_1-z_2$ subspace to estimate $R_s$ . The attained merits include simplicity, low computation burden, and low sensitivity to other parameters of the 6PIM. The adaptation law is derived from the Lyapunov stability theory and Popov hyperstability theory. The proposed technique is applied under a duty cycle control based DTC, where $z_1-z_2$ currents possess reduced amplitudes in comparison with the conventional DTC. The validity of the proposed system is verified by simulation and experimental results.