Current Displacement Research Articles

Математическая модель асинхронной машины в полярных координатах с учетом эффекта вытеснения тока ротора

The article is devoted to developing the mathematical model of an induction machine in polar coordinates, a task that has not been studied to a sufficient detail for being used in engineering applications. The above-mentioned task was solved using the methods of automated control theory, electromechanics, and electrical engineering. The software implementations of the proposed mathematical models and numerical investigations of the processes simulated by these models were carried out in the MATLAB computation environment (the SIMULINK application software package). Three versions of induction machine mathematical models written in polar coordinates and taking into account the rotor current displacement effect are presented. The specific features of implementing such models by means of software are determined. It is found that these models satisfactorily describe the processes in an induction machine both in the working part of its mechanical characteristics and at high rotor slip values. It is shown that the mathematical models written in polar coordinates replicate the processes in an induction machine with the same accuracy as the widely used similar models written in the Cartesian system of coordinates.

RETRACTED: A new perspective on remote Saddle Sine and Cosine coils technique for determination of tokamak plasma equilibrium status

In this contribution we have presented a new perspective for determination of tokamak plasma column shift based on remote multipole moments technique. First, we presented analytical details for using this technique. Then principle of different models based on this technique for design and fabrication of a six coils will be presented: four modified Rogowski coil (two Cosine coils and two Sine coils) and two Saddle coils (Saddle Sine coil (SSC) and Saddle Cosine coil (SCC)). Also, in order to comparison of results the flux loops technique is used. Because of continuous measurements of magnetic field distribution around the tokamak plasma using multipole coils, this technique give us more reliable information about the plasma current displacement.

Precise on-machine extraction of the surface normal vector using an eddy current sensor array

To satisfy the requirements of on-machine measurement of the surface normal during complex surface manufacturing, a highly robust normal vector extraction method using an Eddy current (EC) displacement sensor array is developed, the output of which is almost unaffected by surface brightness, machining coolant and environmental noise. A precise normal vector extraction model based on a triangular-distributed EC sensor array is first established. Calibration of the effects of object surface inclination and coupling interference on measurement results, and the relative position of EC sensors, is involved. A novel apparatus employing three EC sensors and a force transducer was designed, which can be easily integrated into the computer numerical control (CNC) machine tool spindle and/or robot terminal execution. Finally, to test the validity and practicability of the proposed method, typical experiments were conducted with specified testing pieces using the developed approach and system, such as an inclined plane and cylindrical and spherical surfaces.

Giant magnetostrictive actuator nonlinear dynamic Jiles–Atherton model

The hysteresis nonlinearity exists in the giant magnetostrictive actuator (GMA) between input current and output displacement. In order to research the nonlinear dynamic behavior characteristics and control strategies to improve controllability and stability, mathematics model must be accurately established especially in high frequency. Therefore, this paper proposes an electrical-magnetic-thermal-mechanical coupling Jiles–Atherton (J-A) dynamic model that takes exciting current as input and displacement as output through combining Ampere's circulation theorem and GMA structural dynamics equation. Differential evolution genetic algorithm is applied to identify the unknown parameters on the premise of preliminarily determining their own scope according to hysteresis loop characteristics. The better fitting results between simulation and experiment in different conditions prove the correctness and effectiveness of this proposed model.

Research on hysteresis loop considering the prestress effect and electrical input dynamics for a giant magnetostrictive actuator

In this paper, focusing on the application-oriented giant magnetostrictive material (GMM)-based electro-hydrostatic actuator, which features an applied magnetic field at high frequency and high amplitude, and concentrating on the static and dynamic characteristics of a giant magnetostrictive actuator (GMA) considering the prestress effect on the GMM rod and the electrical input dynamics involving the power amplifier and the inductive coil, a methodology for studying the static and dynamic characteristics of a GMA using the hysteresis loop as a tool is developed. A GMA that can display the preforce on the GMM rod in real-time is designed, and a magnetostrictive model dependent on the prestress on a GMM rod instead of the existing quadratic domain rotation model is proposed. Additionally, an electrical input dynamics model to excite GMA is developed according to the simplified circuit diagram, and the corresponding parameters are identified by the experimental data. A dynamic magnetization model with the eddy current effect is deduced according to the Jiles–Atherton model and the Maxwell equations. Next, all of the parameters, including the electrical input characteristics, the dynamic magnetization and the mechanical structure of GMA, are identified by the experimental data from the current response, magnetization response and displacement response, respectively. Finally, a comprehensive comparison between the model results and experimental data is performed, and the results show that the test data agree well with the presented model results. An analysis on the relation between the GMA displacement response and the parameters from the electrical input dynamics, magnetization dynamics and mechanical structural dynamics is performed.

Migrants at sea: Case studies of Syrians and Rohingyas

ABSTRACTAccording to the United Nations, the current worldwide displacement is at the highest level ever recorded. Further, the humanitarian crises unfolding in the Mediterranean and the Bay of Bengal have focused the spotlight on the maritime domain as a prominent escape route. They have also raised many questions pertaining to human security and the humanitarian obligations of the states at one end of the spectrum and national security considerations that come with such mass arrivals on the other. However, the two crises have elicited varying responses by the affected state and non-state actors, who have interpreted international law and state obligations differently. This paper seeks to understand and analyse maritime and policy responses to the Syrians in the Mediterranean and the Rohingyas in the Bay of Bengal and Andaman Sea to identify the best practices for states to comply with their international humanitarian obligations while taking state security imperatives into consideration.

Improving Operational Performance of Magnetically Suspended Flywheel With PM-Biased Magnetic Bearings Using Adaptive Resonant Controller and Nonlinear Compensation Method

Permanent magnet-biased magnetic bearings (PBMBs) are widely used in flywheel energy storage systems because of their comprehensive advantage in power loss and controllability. However, there is a nonlinear relationship between magnetic force, control current, and eccentric displacement of the PBMB. When the system is required to be high performance, the nonlinear dynamics of the PBMB must be considered in a control design. Therefore, this paper proposes a novel nonlinear compensator based on the nonlinear model of the PBMB and it is applied to a magnetically suspended flywheel (MSF) with PBMBs. To implement the perfect nonlinear compensation, an adaptive resonant controller is also presented to compensate the dynamics of the current-mode amplifier. Finally, the proposed method is verified by experiments on the test rig of the MSF and can be used to improve the performance of the system.

Control of Three-to-Five-Phase Matrix Converter Using Carrier-Based PWM Algorithm

Abstract - This paper proposes a simple Carrier-Based PWM (CBPWM) technique to control the three- to five-phase Direct Matrix Converter (3×5 DMC). The proposed technique uses the indirect modulation approach to control the 3×5 DMC such as a three-phase bidirectional rectifier followed by five-phase voltage source inverter (VSI). Based on this approach, it is possible to synthesize the desired five-phase output voltages with sinusoidal three-phase input currents and unity input power factor. A CBPWM method is suggested for each stage independently including both linear and overmodulation operating modes. By the proposed technique, in both operating modes, the maximum possible overall Voltage Transfer Ratio (VTR) are achieved. Moreover, this technique allows the input power factor to be controlled by controlling the input current displacement angle. The feasibility of the proposed technique has been verified by a series of simulation and experimental results based on Matlab/Simulink and dSPACE-DS1104 platform. The results show that, a sinusoidal output and input waveforms can be achieved with a maximum possible VTR in the linear region. However, in the overmodulation region, a maximum possible VTR is achieved at the cost of some distortion of output and input waveforms. Therefore, this technique can be used for the application where a higher VTR is essential.

Syn‐kinematic sedimentation at a releasing splay in the northern Minwun Ranges, Sagaing Fault zone, Myanmar: significance for fault timing and displacement

AbstractThe Sagaing Fault zone is the largest active fault in SE Asia, whose current displacement rate of around 1.8 cm year−1 is well‐established from GPS data. Yet determining the timing of initiation and total displacement on the fault zone has proven controversial. The timing problem can potentially be resolved through a newly identified syn‐kinematic sedimentary section directly related to displacement on the Sagaing Fault in the northern Minwun Ranges. The northern part of the western strand of the Sagaing Fault has a releasing splay geometry that sets up a syn‐kinematic oblique‐extensional basin in its hangingwall, here called the North Minwun Basin. A series of thick ridges probably composed of alluvial fan and fluvial sandstones dipping between 20 and 70° to the north, and younging northwards comprise the basin fill over a distance of 40 km. Total stratigraphic thickness (not vertical thickness) is estimated at 25 km. The basin in terms of depositional geometries, large displacements, and large stratigraphic thickness and appearance on satellite images has parallels with the extensional Hornelen basin, Norway and the strike‐slip Ridge Basin, California. Minimum likely displacement on the fault strand is 40 km, and may possibly be in excess of 100 km. The remote and inaccessible basin has yet to be properly dated, likely ages range between Eocene and Miocene. When dated the basin will provide an important constraint on the timing of deformation. The potential for this basin to constrain the timing and displacement along the northern part of the Sagaing Fault has not been previously recognised.

Epidemiology and treatment reality of proximal humeral fractures at a level-1 trauma center

The treatment of proximal humeral fractures (PHF) is challenging. Recently, more restrictive displacement criteria have been introduced and the lack of treatment algorithms in the literature has been emphasized. The primary purpose of this study was to evaluate the epidemiology and treatment reality of PHF at a specialized level-1 trauma center according to current displacement criteria. The secondary aim was to assess whether a standardized treatment algorithm can be adhered to during daily clinical routine. In all, 566 patients (71.4 % female; average age, 68.1 ± 15 years) with 569 PHF were included in this retrospective cohort study. All medical records and existing x‑rays as well as computed tomography scans were analyzed. Only fractures with ad latus displacement of max 0.5 cm and/or a humeral head angulation of less than 20o were classified as nondisplaced. Patients with displaced fractures were included for evaluation of a standardized treatment algorithm. The most common fracture type was a three-part fracture (39.9 %, n = 227); 70.9 % of fractures (389/569) were displaced and therefore treated operatively. The accordance between the final operative treatment that patients received and the recommended surgical treatment on the basis of the algorithm was 90.2 % (351/389). In contrast to the rate of 15 % dislocated fractures reported by Charles Neer in 1970, more than 70 % of fractures were found to be displaced when more restrictive displacement criteria were applied. More than 90 % of displaced fractures were treated as recommended by the treatment algorithm. Fractures that fitted the least into the treatment scheme were more complex fractures of patients aged 60 years and older.

Design and Construction of a Magnetic Levitation System Using Programmable Logic Controller

The motivation of this paper is to design and fabrication a cost effective magnetic levitation (shortly called Maglev) system using PLC. For this purpose a stand, a 12 volt electromagnet, eddy current displacement sensor which input voltage is 24 volt and output voltage range is 0 to 10 volt for 0 to 10 mm displacement, Siemens Logo PLC setup board including CPU, cable, analog expansion module, an amplifier circuit & Logo soft software are used. Sensor senses the displacement of a target and gives corresponding signal in terms of voltage. This sensor output voltage is used as input in PLC input terminal. CPU works according to ladder diagram which is installed in program memory. The electromagnet is connected to the analog expansion output terminal. The current is controlled by PLC according to sensor signal which passes through the electromagnet. When distance between the sensor and target is increased the output sensor voltage is increased. PLC receives this voltage and decrease the current supply at output terminal. Thus the magnetic force is decreased and target is levitated at a desired position. When the distance between the sensor and the object is decreased, then current is increased in electromagnet which increases the magnetic force and the target returns to its levitate position. Finally the target is levitated. This paper will be helpful to simplify this control system and implement in different types of maglev study and industrial issues as well.

Time Integration Method Based on Discrete Transfer Function

Complex structural dynamic problems are normally analyzed by finite element and numerical integration techniques. An explicit time integration algorithm with second-order accuracy and unconditional stability is presented for dynamic analysis. Utilizing weighted factors, the current displacement and velocity relations are defined in terms of the accelerations of two previous time steps. The concept of discrete transfer function and the pole mapping rule from the control theory are exploited to develop the new algorithm. Several linear and nonlinear dynamic analyses are performed to verify the efficiency of the method compared with the well-known Newmark method.

Relapsing fever in asylum seekers from Somalia arriving in Belgium in August 2015

Current population displacements favor the re-emerging of diseases, nowadays very rare in Europe. We report two cases of ‘imported’ relapsing fever in two Somali asylum seekers occurring shortly after their arrival in Belgium. A diagnosis of relapsing fever should be considered in all migrants coming from endemic regions or having traveled in low hygiene and crowded conditions, presenting with recurrent fever, especially if no malaria parasites are found.

Field Dynamic Balancing for Rigid Rotor-AMB System in a Magnetically Suspended Flywheel

To effectively reject the influence of rotor unbalance on system stability and precision for a magnetically suspended flywheel, this paper proposes a novel rigid rotor field dynamic balancing method based on autocentering control and the equivalence of magnetic control force and the rotor unbalance centrifugal force. By the autocentering control, the rotor is forced to rotate around its geometric axis. After demonstrating the equivalence of the external control force and the rotor unbalance centrifugal force, the rotor unbalance can be identified from the magnetic force. Since the position of the rotor geometric axis can be measured precisely by an eddy current displacement sensor, the high-precision autocentering control can be achieved easily. Furthermore, since the magnetic force is proportional to the control current when the rotor is at its equilibrium point, the magnetic force can be obtained by measuring the control current and multiplying it with the force–current stiffness. Without trial weights, the efficiency of the proposed field dynamic balancing method is high. Finally, the effectiveness and superiority of the proposed rotor balancing strategy have been demonstrated by the experimental results.

A one-step Newmark displacement model for probabilistic seismic slope displacement hazard analysis

Estimating the earthquake-induced sliding displacement is important in assessing the stability of slopes during earthquakes. Current Newmark displacement models generally use ground motion intensity measures (IMs) as predictors, and the uncertainties of predicting IM values need to be accounted for in probabilistic seismic slope displacement hazard analysis. This paper aims at developing a simple one-step predictive model for the Newmark displacement based on only four seismological parameters (moment magnitude, rupture distance, fault categories and shear wave velocity at top 30m Vs30) rather than any IMs. The predictive model is suitable for critical acceleration from 0.02g to 0.25g, covering most of the susceptible earthquake-induced landslide cases. First, the proposed one-step model is compared with some recently developed IM-based Newmark displacement models. It is found that both the median predictions and the variabilities of the proposed one-step model are in reasonable agreement with those obtained by the IM-based models. Second, several hypothetical slopes are used to compare the slope displacement hazard curves between the one-step model and the IM-based models. The new model can be used as an alternative method for a fully probabilistic analysis of the earthquake-induced slope displacements. In addition, spatial correlations of the Newmark displacement residuals are also investigated using strong-motion data from the Northridge and Chi-Chi earthquakes.

On the inward drift of runaway electrons during the plateau phase of runaway current

The well observed inward drift of current carrying runaway electrons during runaway plateau phase after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved. The balance between the change in canonical angular momentum and the input of mechanical angular momentum in such a system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by integrating the modified Euler-Lagrange equation over one bounce time. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in the ideal wall case and no wall case, and the runaway current center displacement as a function of parallel momentum variation is obtained. The time scale of such displacement is estimated by considering effective radiation drag, which shows reasonable agreement with the observed displacement time scale. This indicates that the phase space dynamic studied here plays a major role in the horizontal displacement of runaway electrons during plateau phase.

Analysis and design of permanent magnet biased magnetic bearing based on hybrid factor

In this article, hybrid factor is proposed for hybrid magnetic bearing. The hybrid factor is defined as the ratio of the force produced by the permanent magnet and the forces produced by the permanent magnet and current in hybrid magnetic bearing. It is deduced from a certain radial hybrid magnetic bearing using its important parameters such as the current stiffness and displacement stiffness at first and then the dynamic model of magnetically suspended rotor system is established. The relationship between structural parameters and control system parameters is analyzed based on the hybrid factor. Some influencing factors of hybrid factor in hybrid magnetic bearing, such as the size of the permanent magnet, length of air gap, and area of the stator poles, are analyzed in this article. It can be concluded that larger hybrid factor can be caused by the smaller power loss according to the definition of hybrid factor mentioned above. Meanwhile, the hybrid factor has a maximum value, which is related to control system parameters such as proportional factor expect for structural parameters. Finally, the design steps of parameters of hybrid magnetic bearing can be concluded.

Completely contactless structural health monitoring of real-life structures using cameras and computer vision

Summary A newly developed, completely contactless structural health monitoring system framework based on the use of regular cameras and computer vision techniques is introduced for obtaining displacements and vibrations of structures, which are critical responses for performance-based design and evaluation of structures. To provide contactless and practical monitoring, the current vision-based displacement measurement methods are improved by eliminating the physical target attachment. This is achieved by means of utilizing imaging key-points as virtual targets. As a result, pixel-based displacements of a monitored structural location are determined by using an improved detection and match key-points algorithm, in which false matches are identified and discarded almost completely. To transform pixel-based displacements to engineering units, a practical camera calibration method is developed because calibration standard on a physical target no longer exists. Moreover, a framework for evaluating the accuracy of vision-based displacement measurements is established for the first time, which, in return, provides users with the most crucial information of a measurement. The proposed framework along with a conventional sensor network and a data acquisition system are applied and verified on a real-life stadium during football games for structural assessment. The results obtained by the new method are successfully validated with the data acquired from sensors such as linear variable differential transformers and accelerometers. Because the proposed method does not require any type of sensor and target attachment, common field works such as sensor installation, wiring, maintaining conventional data acquisition systems are not required. This advantage enables an inexpensive and practical way for structural assessment, especially for real-life structures. Copyright © 2016 John Wiley & Sons, Ltd.

Feedforward compensation control of rotor imbalance for high-speed magnetically suspended centrifugal compressors using a novel adaptive notch filter

This paper introduces a feedforward control strategy combined with a novel adaptive notch filter to solve the problem of rotor imbalance in high-speed Magnetically Suspended Centrifugal Compressors (MSCCs). Unbalance vibration force of rotor in MSCC is mainly composed of current stiffness force and displacement stiffness force. In this paper, the mathematical model of the unbalance vibration with the proportional–integral–derivative (PID) control laws is presented. In order to reduce the unbalance vibration, a novel adaptive notch filter is proposed to identify the synchronous frequency displacement of the rotor as a compensation signal to eliminate the current stiffness force. In addition, a feedforward channel from position component to control output is introduced to compensate displacement stiffness force to achieve a better performance. A simplified inverse model of power amplifier is included in the feedforward channel to reject the degrade performance caused by its low-pass characteristic. Simulation and experimental results on a MSCC demonstrate a significant effect on the synchronous vibration suppression of the magnetically suspended rotor at a high speed.

电涡流式传感器液面测量控制系统

随着微电子技术的不断发展，智能化程度的日益加深，以及国家相关政策支持力度的不断加大，其在测量领域发挥的作用也日见显著。在工业生产与日常生活中，经常需要进行液面高度测量，采用微电子技术作为控制系统具有小型化、低功耗、可靠性高的优点。文中介绍了一种电涡流式位移传感器，是一以单片机为核心的液面高度测量电子控制系统。本控制系统以单片机为核心，控制液面高度数据的采集、管理以及远程通讯，具有体积小、维护容易、可靠性高、实时测量并显示液面高度值、记录历史数据、远程传输等优点。本文综合应用了传感器、微控制器等领域的知识，详细介绍了液面高度测量电子控制系统的整体结构及控制方法。本文的研究实现了液面测量电子控制系统的小型化，智能化，并基于接触式测量方法进一步确保了测量的精准度，从而降低了测量装置的复杂性，节约了材料，具有重要的现实意义和显著的社会效益。 With the development of microelectronics technology, increasingly intelligent and relevant national policies and support growing, its role in the measurement region has become more significant. In industrial production and daily life, it is often necessary for liquid level measurement, of which microelectronic technology is adopted as the control system, having advantages of miniaturization, low power consumption, and high reliability. Eddy current type displacement sensor is introduced in this paper, based on the single chip microcomputer electronic control system of liquid height measurement. This system uses single-chip microcomputer as the core control system, and controls liquid level data collection, management, and telecommunications. Small size, easy maintenance, high reliability, real time measurement and displaying the liquid height value, recording historical data remote transmission and so on are advantages of this system. This paper comprehensively applies knowledge in the areas of sensors, micro-controller, and introduces in detail the overall structure and control methods of electronic control system of liquid height measurement. This study implements the miniaturization and intelligentization of electronic control system of liquid level measurement, and based on contact measuring method ensures the measurement accuracy, which can reduce the complexity of measuring devices, save material, having important practical significance and significant social benefits.