Axis Frame Research Articles

Improved Model Predictive Current Control for SPMSM Drives Using Current Update Mechanism

Finite-set model predictive current control (FS-MPCC) has been employed for machine drives owing to the good dynamic performance. Sensitivity to parameter variation is one of the main barriers to its widespread application. To overcome this barrier, this article proposes an improved FS-MPCC for surfaced permanent magnet synchronous machines (SPMSMs). The contribution of this article is developing a novel current update mechanism, where the variation of resistance, rotor flux linkage, and inductance is considered, in which a modified coordinate system that contains a stationary and rotary axis frame is introduced. In this case, the predicted parameter can be obtained more accurately based on this mechanism, which can suppress the disturbances caused by model parameter mismatch. In addition, SPMSM parameter mismatch effect on FS-MPCC performance is analyzed in this article, which testifies that resistance mismatch influence on current prediction error can be neglected in practical system. The proposed FS-MPCC is validated and compared with different state-of-the-art methods. Improvement of the proposed control strategy is validated by means of experimental results on a 2-kW test rig.

Analytical Modelling of Dynamic Performance with Harmonic Current Injection for Doubly Salient SynRMs

A new analytical torque model based on dq0 -axis frame has been developed for 3-phase, 12-slot/8-pole single layer doubly salient synchronous reluctance machines. This newly developed torque model, compared to the one often based on abc -axis frame, is necessary to simplify the investigation of dynamic performance such as torque–speed curve and efficiency maps. It has been found that the third-order current harmonic injection not only improves the torque performance (increased average torque and reduced torque ripple) in constant torque region but also maintains a similar torque level as the fundamental current supply in the flux weakening region. Moreover, although the fifth- and seventh-order current harmonic injection can reduce the torque ripple of machine, their dynamic performances are compromised due to low average torque and significant voltage distortion. Finite element simulations and dynamic tests have been carried out to prove the accuracy of the developed torque model and also the efficiency of the proposed current harmonic injection method.

Improvement of Control Strategy for Pmsg Based Wecs under Strong Wind Conditions with Anfis Controller

Wind farms can only operate and generate power under certain limit of wind speeds if the wind speed is observed beyond the limit then the operation of the wind farm reaches the cutoff region , so in order to operate the wind farm even under strong wind conditions which exceed the limit a control strategy is involved, due to the inability of the PI controller to operate under varying parameters the generated power is affected so in order to adapt a controller that can operate under varying real time parameters a ANFIS controller is adapted in this paper where generated power and d-q axis frame currents are analyzed for linearly rising wind conditions and typhoon landed conditions .

Derivation of All Attitude Error Governing Equations for Attitude Filtering and Control.

This article presents the full analytical derivations of the attitude error kinematics equations. This is done for several attitude error representations, obtaining compact closed-forms expressions. Attitude error is defined as the rotation between true and estimated orientations. Two distinct approaches to attitude error kinematics are developed. In the first, the estimated angular velocity is defined in the true attitude axes frame, while in the second, it is defined in the estimated attitude axes frame. The first approach is of interest in simulations where the true attitude is known, while the second approach is for real estimation/control applications. Two nonlinear kinematic models are derived that are valid for arbitrarily large rotations and rotation rates. The results presented are expected to be broadly useful to nonlinear attitude estimation/control filtering formulations. A discussion of the benefits of the derived error kinematic models is included.

The initial spin probability distribution of primordial black holes

We study the spin of primordial black holes produced by the collapse of large inhomogeneities in the early universe. Since such primordial black holes originate from peaks, that is, from maxima of the local overdensity, we resort to peak theory to obtain the probability distribution of the spin at formation. We show that the spin is a first-order effect in perturbation theory: it results from the action of first-order tidal gravitational fields generating first-order torques upon horizon-crossing, and from the asphericity of the collapsing object. Assuming an ellipsoidal shape, the typical value of the dimensionless parameter as=S/GN M2, where S is the spin and M is the mass of the primordial black hole, is about (Ωdm/π) σδ√1−γ2. Here, σ2δ is the variance of the overdensity at horizon crossing, Ωdm measures the current abundance of the dark matter and the parameter γ is a measure of the width of the power spectrum giving rise to primordial black holes. One has γ=1 for monochromatic spectra. For these narrow spectra, the suppression arises because the velocity shear, which is strongly correlated with the inertia tensor, tends to align with the principal axis frame of the collapsing object. Typical values of as are at the percent level.

Design, Simulation and Hardware Implementation of Shunt Hybrid Compensator Using Synchronous Rotating Reference Frame (SRRF)-Based Control Technique

This paper deals with the design, simulation, and implementation of shunt hybrid compensator to maintain the power quality in three-phase distribution networks feeding different types balanced and unbalanced nonlinear loads. The configuration of the compensator consists of a selective harmonic elimination passive filter, a series-connected conventional six-pulse IGBT inverter, acting as the active filter terminated with a DC link capacitor. The theory and modelling of the compensator based on current harmonic components at the load end and their decomposition in d-q axis frame of reference are utilized in the reference current generation algorithm. Accordingly, the source current waveform is made to follow the reference current waveform using a high-frequency, carrier-based controller. Further, this inner current control loop is supported by a slower outer voltage control loop for sustaining desirable DC link voltage. Performance of the compensator is evaluated through MATLAB simulation covering different types of loads and reduction of harmonic currents and THD at the supply side along with excellent regulation of DC link voltage are confirmed. The performance of a hybrid compensator designed and fabricated using the above principles is evaluated and corroborated with the simulation results.

A Clamping Force Performance Evaluation of the Electro Mechanical Brake Using PMSM

This paper deals with clamping force simulation and experimental result of the Electro Mechanical Brake (EMB) for the High-Speed-Train (HST). Three phase Surface Permanent Magnet Synchronous Motor (SPMSM) is applied to the clamping force control of EMB. At the initial development stage, Proportional Integral (PI) current control under synchronous d-q axis frame was applied to the SPMSM torque control. In addition, an anti-windup controller, which is advantageous for fast current tracking, is proposed to improve the torque output. Matlab/Simulink simulation results were compared with the experimental results measured by the clamping force sensors of the EMB test rig. The experimental results were verified compared to the brake design specification of the High-Speed Electric Multiple Unit-430 Experimental (HEMU-430X) train.

Probing Axial Water Bound to Copper in Tutton Salt Using Single Crystal 17O-ESEEM Spectroscopy.

Electron spin-echo envelope modulation (ESEEM) signals attributed to axial water bound to Cu2+ have been detected and analyzed in Cu(II)-doped 17O-water-enriched potassium zinc sulfate hexahydrate (Tutton salt) crystals. The magnetic field orientation dependences of low frequency modulations were measured to fit hyperfine and quadrupole coupling tensors of a 17O ( I = 5/2) nucleus. The hyperfine tensor ( A xx, A yy, A zz: 0.13, 0.23, -3.81 MHz) exhibits almost axial symmetry with the largest value directed normal to the metal equatorial plane in the host structure. Comparisons with quantum chemical calculations position this nucleus about 2.3 Å from the copper. The isotropic coupling (-1.15 MHz) is small and reflects the weak axial water interaction with a dx2-y2 unshared orbital of copper. The 17O-water quadrupole interaction parameters ( e2 qQ/ h = 6.4 MHz and η = 0.93) are close to the average of those found in a variety of solid hydrates. In addition, the coupling tensor directions correlate very closely with the O8 water geometry, with the maximum quadrupole direction 3° from the water plane normal, and its minimum coupling about 2° from the H-H direction. In almost all previous magnetic resonance 17O-water studies, the quadrupole tensor orientation was based on theoretical considerations. This work represents one of the few experimental confirmations of its principal axis frame. When Cu2+ dopes into the Tutton salt, a Jahn-Teller distortion interchanges the relative long and intermediate metal O7 and O8 bond lengths of the zinc host. Therefore, only those unit cells containing the impurity conform to the pure copper Tutton structure. This study provides further support for this model. Moreover, coupling interactions from distant H217O such as in the present case have important implications in studies of copper enzymes and proteins where substrates have been proposed to displace weakly bound water in the active site.

An overview of sheep farming features and management practices in the region of south western Peloponnese and how they reflect on milk microbial load

In this study the demographic features, various farm characteristics and milk quality parameters were investigated in sheep farms (n =128) from the North West Peloponnese region, using a prescreen questionnaire. The interviewed sheep farmers were under the control of the regional milk control laboratory of the Hellenic Milk Organization ELGO «Dimitra», which provided us with the corresponding milk quality data for the first quarter of 2014. Our findings regarding the demographic data demonstrated that 23% of farmers were 31-40 years old, 64% of them were high school graduates and 28% had received relevant farming general training; namely 17% of them has designated as “young farmers” in the frame of Third Axis of the Operational Program «Rural Development-Regeneration of the Countryside 2000-2006» and 11% have attended briefings by veterinarians and agriculturists. Ιn terms of farm characteristics, it has been revealed that the mean flock size was 148 sheep and regarding the farming system, the majority of the farms (89.15%) applied a mixed extensive / indoors system. Additionally, regarding building infrastructures and the way of milking, there was limited technological penetration, since the buildings were old-style (77%) and the milking procedure was performed by hands (83%). Concerning the milk composition, the measurements showed mean values of (%) content of fat, protein, lactose and non-fat dry matter (NFDM) at 6.54±0.88, 5.56±0.36, 4.59±0.23 and 10.95±0.42, respectively. Furthermore, the mean value of the total bacterial count (TBC) was found 5.38±0.55 log cfu/ml and the pH value at 6.71±0.11. In general, sheep farmers had a good perception of the integrated management and their prospect for sheep farming was optimistic. The impact of this study is that farmers increase their trust to the educational institutions and are prompted to become more receptive to new adaptive trends.

Modeling and Implementation of MPPT based Wind Energy System Using Cuckoo Search

This paper presents adjustable speed generators for wind turbines. In order to improve the potential and performance of wind turbine system this paper proposes a concept DFIG. Generally wind nature is not fixed it varies linearly w.r.t time, hence, a MPPT controller is proposed in this paper. This paper presents the DFIG wind energy system. A Control strategy implemented and controlled by framing rotor reference frame axis in terms of direct and quadrature axis coordinates. A PI based RSC and GSC controllers are introduced to control the power through the wind system to grid. This proposed model is implemented and verified by using Matlab/Simulink.

On-the-go Image Processing System for Spatial Mapping of Lettuce Fresh Weight in Plant Factory

Real-time monitoring of crop growth parameters in plant factory can provide useful information about accurate assessment of their growth status for precision crop management. Plant weight is one of the most important biophysical properties used to determine the optimum time for harvesting. Conventional plant weight measurements are destructive and laborious. An on-the-go image processing system consisting of image acquisition and weight estimation was developed to generate a fresh weight map of plants grown in hydroponic solutions. Key technologies developed in this study are real-time image processing and spatial mapping methods that estimate the fresh weights of individual lettuces. Images were automatically captured with a low cost web camera and processed using a MYRIO-based embedded controller. The camera and embedded system moved along an XY axis frame above a plant growing bed (0.94 x 1.8 m) using two stepping motors and linear actuators. The image preprocessing algorithm consisted of two main subroutines, i.e., image segmentation and target plant recognition. For the image segmentation, the S channel of the HSV color space and Otsu’s threshold were used to separate the plants from the background. The target plant was identified based on location information of the growing bed holes in captured images. The plant weight was estimated using calibration equations previously developed that relate the pixel numbers of lettuce images to their actual fresh weights in conjunction with the use of a two-point normalization method. The accuracy of the fresh weight determined by the developed embedded system was confirmed by a highly linear relationship with a slope near 1.0 and a coefficient of determination (R2) of 0.95 with a processing time of within 4 s. In addition, it was possible to generate a spatial map of the fresh weights of lettuces grown in a cultivation bed, which could be used to estimate their yields prior to harvesting.

Frames of reference in multibody dynamics

In this paper, a discussion is undertaken concerning the use of so-called floating frames of reference in the calculation of the kinetic and elastic energies of parts in a multibody system. The use of floating frames may simplify the calculation of the elastic energy, although sometimes at the expense of more elaborate expressions for the kinetic energy. These expressions may involve terms that couple the motion of the floating frame and the relative motion of the part. The choice of a floating frame may be arbitrary but in order to obtain as simple expressions as possible some care must be taken. When a (flexible) part is connected to a rigid part one may use a frame in which the rigid part is at rest. If so then one has, in general, to deal with coupling terms in the kinetic energy for the flexible part. There is one unique frame in which these coupling terms disappear. This frame is called the principal frame of reference. Relative to this frame the kinetic energy of the part is minimal compared to the kinetic energy relative to other frames. Two independent proofs of this property are presented. The principal frame is defined by the associated change of frame mapping. This mapping is given a full characterization. It may however be cumbersome to calculate the kinetic energy relative to the principal frame. A method for doing this is designated. A frame that has been given some attention in the literature is the principal axis frame of reference. In this paper, a full characterization of this frame and its relation to the principal frame is given. Two examples of an Euler–Bernoulli beam in rotational motion are presented and compared in the light of the theoretical findings of this paper. In conventional presentations of mechanics the Euclidean spaces associated with different frames of reference are taken to be identical. In this paper this assumption is abandoned and different frames of reference will correspond to different Euclidean spaces. From a conceptual point of view this is a natural step to take in order to increase clarity and generality. It automatically includes the dependence of the reference placement on the frame of reference. This approach has been analyzed in a previous paper by the present author. References to this paper will appear whenever needed for. Consequences of this approach are investigated in terms of transformation formulas for kinematical and dynamical quantities.

Integrated Field and Armature Current Control for Dual Three-Phase Variable Flux Reluctance Machine Drives

An integrated field and armature current control strategy is proposed for dual three-phase variable flux reluctance machines (VFRMs). The proposed method utilizes a sinusoidal current biased by dc offset rather than separated field and armature currents in an external field current control. In order to generate the dc and ac components together, a dual three-phase inverter is adopted, in which one side of each stator winding is connected to a neutral point. The dq -axis currents are controlled by the dual three-phase inverter, whereas zero sequence current is generated as a field current by the zero vector redistribution between two inverters. Since the integrated current control allows an integrated winding, which reduces the winding resistance to half, the copper loss can be also reduced to half. To apply the vector control scheme, the voltage and torque equations are derived for dual three-phase VFRMs in a synchronous dq -axis frame. These equations are also utilized for the dynamic simulation with the aid of MATLAB/Simulink. The experimental results validate that the proposed strategy can effectively increase the efficiency and extend the operating speed range.

The Analysis and Development of a Power Flow-Based Controller for Microgrid Systems

This paper presents the analysis, development, and implementation of a new controller for microgrid systems. The developed controller is structured to produce command values for the active and reactive powers ( $P_{C}$ and $Q_{C}$ ), and $d$ – $q$ -axis voltage components ( $v_{\text{dC}}$ and $v_{\text{qC}}$ ) for each bus in the microgrid system at hand. Values for $P_{C},Q_{C},v_{\text{dC}}$ , and $v_{\text{qC}}$ are obtained using a power flow formulated in the $d$ – $q$ -axis frame. The $d$ – $q$ -axis power flow (DQPF) produces values for $P_{C},Q_{C},v_{\text{dC}}$ , and $v_{\text{qC}}$ that can meet load demands, respond to variations in power generation within the microgrid, and accommodate the mode of operating the microgrid (interconnected or standalone), while maintaining the voltage and frequency stability. The DQPF-based controller is implemented for performance evaluation using a five-bus microgrid system operated under various conditions, including changes in power generation, step changes in load demands, and changes in mode of operation. Test results demonstrate that the DQPF-based controller can offer simple implementation, accurate and fast responses, and negligible sensitivity to the mode of microgrid operation.

Formation of Slow Electron Pairs in an External Coulomb Field

The wave equation for two electrons in an external Coulomb field (helium-like atoms) has been shown to be a problem in a three-dimensional half-space. The wave-equation becomes quasi-separable in inertial coordinates. This allows to work out the electron motion in the frame of principal inertia axes. We find that non-adiabatic coupling terms constitute a fictitious force and lead to a deformation of the static potential surface. Incoming and outgoing modes of electron pairs are studied in detail, and applied to the threshold ionization of hydrogen-like atoms by electrons. Our analysis confirms the classical work by Wannier. However, we go beyond Wannier and present bending and stretch vibrations of electron pairs. The bending vibration has no influence onto the total ionization cross-section. The pair formation below threshold destroys the existence of high double Rydberg resonances. Finally, we describe the propagation of an electron pair through a linear chain of Rydberg atoms.

Unified Unbalanced Synchronous Reference Frame Current Control for Single-Phase Grid-Connected Voltage-Source Converters

This paper presents a unified structure of the unbalanced synchronous reference current control strategies for single-phase grid-tied voltage-source converters to obtain a zero steady-state error in the line current. An arbitrary waveform is used as the orthogonal current for the stationary to rotating frame axis transformation of the reference and measured grid currents. Various choices of such orthogonal signals lead to different control structures with the same performance characteristics. This causes a temporary unbalanced system, in which double-line frequency components appear in the control loops during the transient state. The proposed method with cross-axis decoupling, tuned at the control loop bandwidth by greater than eight times the grid frequency, has better performance than the existing virtual balanced synchronous reference frame scheme. Absence of the orthogonal signal generation guarantees the stability criterion of the control scheme. A zero steady-state error is still achieved under conditions of uncertainty in the converter parameters. Simulation and experimental results of a 1.5-kVA pulse width modulation rectifier validate the proposed methodology.

Relative Trajectory Estimation During Chang'e-2 Probe's Flyby of Asteroid Toutatis Using Dynamics, Optical, and Radio Constraints

The mystery of the asteroid (4179) Toutatis was revealed by Chang'e-2 spacecraft during a close flyby on December 13, 2012. Optical imaging and navigation of the probe during the flyby were performed entirely under ground-based radio tracking and default sequence built on ground. This paper establishes a set of estimation algorithms of the relative trajectory between Chang'e-2 and Toutatis based on dynamics, optical, and radio constraints that are determined by the unique flyby mode. This study is the first time to precisely reproduce the core process of Chang'e-2's encounter with Toutatis based on several optical images. In addition to constructing a strict photogrammetric model, the shadowing effects caused by the illumination and the deviation of the center-of-mass (COM) from the center-of-figure (COF) in optical images are also considered. The spacecraft trajectory with regard to the COF of the body is estimated using images taken from 120 km or less. The formal one sigma uncertainty is (67, 20, and 11 m) in the principal axes frame of the position error ellipse, and the closest approaching distance between Chang'e-2 and Toutatis's COF is calculated as 1557 ± 11 m, which is more precise than previous results with an uncertainty of hundreds of meters. The spacecraft trajectory with regard to the COM of the body is estimated with an uncertainty of (211, 34, and 17 m), and the corresponding closest distance is estimated as 1451 ± 18 m based on the previously developed shape model of Toutatis. The algorithms and results in this study are important for evaluating the performance of this flyby mission and are also valuable for any similar optical navigation during a close approach. In addition, our results can help in precisely determining the axis of Toutatis and sizes of impact craters, which are critical for understanding the formation and evolution of Toutatis.

Effect of 3-D Modeling on Design of Pre-Engineered Steel Buildings

Professional engineers in Pre-engineered buildings (PEB) generally adopt two dimensional (2-D) modeling of frame i.e. plane frame modeling in transverse direction and profess for optimal design using elastic method. In practice, 2-D modeling of main frame is done for transverse frame while in longitudinal direction truss analogy is adopted mainly for analysis of bracing. In 2-D analysis majority of cases only major axis moment is considered and the minor axis moment (having sometimes significant effect on design) is generally ignored. This minor axis moment can be of less magnitude if the bracings are of X type designed as compression as well as tensile members. However in practice these bracings are designed as tension only members, leading to significant effect of minor axis moments. It is also reported that if the ratio of deflections at knee joint in direction of ridge from second order analysis (Δ2) versus first order (Δ1), is 1.5 or more, second order analysis is must, however most of the cases in practice this factor is ignored. This study is aimed to check and quantify the effect due to minor axis moment, i.e. My, in braced frames at knee joint. In absence of second order analysis, as mandated by codes, an approximate practical approach is presented for assessment of the minor axis moment, My, in terms of major axis frame moment, Mz. It is observed that the ratio of building height to width is significant in determining ratio My/Mz. Keywords: 2-D analysis, 3-D analysis, Cross bracing, Minor axis Moments,, Pre-engineered buildings, PEB,.

Penerapan Teknik Citra Digital Sebagai Metode Pengukuran Morfometrik Ternak Pada Sapi Bali dan Peranakan Ongole

Morphometric measurements using digital image technique give a lot of benefits i.e., a safer method both for the researchers and the experimental animals, produce a more accurate morphometric data, reduce the stress in the experimental animals and produce a more detail and complete morphometric data. This experiment used 20 Ongole cross cattle and 20 Bali cattle with the average age of 3 years. Digital image data were collected by using DSLR camera with 18Mp resolution. The collected digital image data were analyzed by using Image J program. Parameters measured in this observation were body length, body height, hip height, pelvic height, loin height, the length of ossa vertebrae cervicales, the length of ossa vertebrae thoracicae, the length of ossa vertebrae lumbales, the length of os scapula, the length of os humerus, the length of ossa radius-ulna, the length of os metacarpale III, the length of os femoris, the length of ossa tibia-fibula, and the length of os metatarsale III. Digital image technique could replace the manual technique for morphometric measurement with a lower level of variance (<10%). Application of digital image technique for measurement of morphometric parameters in Ongole Cross and Bali cattle showed that Bali cattle has a potential for muscle deposition in body frame and body axis while Ongole Cross cattle has a potential for muscle deposition in fore and hind legs.

Instantaneous progression reference frame for calculating pelvis rotations: Reliable and anatomically-meaningful results independent of the direction of movement

In motion analysis, pelvis angles are conventionally calculated as the rotations between the pelvis and laboratory reference frame. This approach assumes that the participant's motion is along the anterior–posterior laboratory reference frame axis. When this assumption is violated interpretation of pelvis angels become problematic. In this paper a new approach for calculating pelvis angles based on the rotations between the pelvis and an instantaneous progression reference frame was introduced. At every time-point, the tangent to the trajectory of the midpoint of the pelvis projected into the horizontal plane of the laboratory reference frame was used to define the anterior–posterior axis of the instantaneous progression reference frame. This new approach combined with the rotation–obliquity–tilt rotation sequence was compared to the conventional approach using the rotation–obliquity–tilt and tilt–obliquity–rotation sequences. Four different movement tasks performed by eight healthy adults were analysed. The instantaneous progression reference frame approach was the only approach that showed reliable and anatomically meaningful results for all analysed movement tasks (mean root-mean-square-differences below 5°, differences in pelvis angles at pre-defined gait events below 10°). Both rotation sequences combined with the conventional approach led to unreliable results as soon as the participant's motion was not along the anterior–posterior laboratory axis (mean root-mean-square-differences up to 30°, differences in pelvis angles at pre-defined gait events up to 45°). The instantaneous progression reference frame approach enables the gait analysis community to analysis pelvis angles for movements that do not follow the anterior–posterior axis of the laboratory reference frame.