Robust SVM-direct torque control of induction motor based on sliding mode controller and sliding mode observer

This paper proposes a design of control and estimation strategy for induction motor based on the variable structure approach. It describes a coupling of sliding mode direct torque control (DTC) with sliding mode flux and speed observer. This algorithm uses direct torque control basics and the sliding mode approach. A robust electromagnetic torque and flux controllers are designed to overcome the conventional SVM-DTC drawbacks and to ensure fast response and full reference tracking with desired dynamic behavior and low ripple level. The sliding mode controller is used to generate reference voltages in stationary frame and give them to the controlled motor after modulation by a space vector modulation (SVM) inverter. The second aim of this paper is to design a sliding mode speed/flux observer which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The effectiveness of the whole composed control algorithm is investigated in different robustness tests with simulation using Matlab/Simulink and verified by real time experimental implementation based on dS pace 1104 board.     

Crystal Structure and Physicochemical Properties of Two Supramolecular Compounds: (C4H8NH2)4[Mo8O26] and (NH4)Na2[AsIIIMo6O21(O2CCH2NH3)3]·8H2O

Two inorganic–organic hybrid supramolecular compounds based on polyoxometalates formulated as (C₄H₈NH₂)₄[Mo₈O₂₆] (1) and (NH₄)Na₂[As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]·8H₂O (2) have been synthesized by conventional solution method and characterized by infrared, UV–Vis and single-crystal X-ray diffraction analyses. Thermal analysis was performed to study their thermal stability. The atomic arrangement in compound (1) can be described as inorganic layers built by [Mo₈O₂₆]^4?, pyrrolidinium cations are embedded into layers. The fascinating structural feature of compound (2) is that the glycine molecules are bounded to two edge-sharing Mo centers via their carboxylate functionality leading to functionalized heteropolymolybdate [As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]^3?, extensive net hydrogen bonds between cations and anions contribute to the crystal packing. The electrochemical behavior of compound (2) has been studied.     

Parallel prefix operations on GPU: tridiagonal system solvers and scan operators

The Journal of Supercomputing - Modern GPUs can achieve high computing power at low cost, but still requires much time and effort. Tridiagonal system and scan solvers are one example of widely used...     

Magnetic and specific heat studies of the frustrated Er2Mn2O7 compound

A new Er2Mn2O7 compound was synthesized by the ceramic method and its crystal structure was characterized using powder X-ray diffraction (XRD) and observed by scanning electron microscopy (SEM). The magnetic properties were investigated using a BS2 magnetometer and the heat capacity was studied using a quantum design (PPMS). The structural study revealed that this compound was monophasic and crystallized in the monoclinic system with the P2/M space group. Magnetization measurements were carried out in the temperature range of 1.8-200 K under an applied magnetic field of 0.05 T. A crossover from a room temperature paramagnetic phase to an antiferromagnetic one at low temperature was detected from the magnetic study. The magnetic susceptibility, in the paramagnetic region above 40 K, was found to present a simple Curie-Weiss type behavior. From the specific heat (CP) measurements in magnetic fields up to 5 T, we noted the presence of a wide peak characteristic of a second order mag-neto-structural transition.     

GVLiDAR: an interactive web-based visualization framework to support geospatial measures on lidar data

In recent years lidar technology has experienced a noticeable increase in its relevance and usage in a number of scientific fields. Therefore, software capable of handling lidar data becomes a key point in those fields. In this article, we present GPU-based viewer lidar (GVLiDAR), a novel web framework for visualization and geospatial measurement of lidar data point sets. The design of the framework is focused on achieving three key objectives: performance in terms of real-time interaction, functionality, and online availability for the lidar datasets. All lidar files are pre-processed and stored in a lossless data structure, which minimizes transfer requirements and offers an on-demand lidar data web framework.     

MHD mixed convection flow along a vertically heated sheet

Main objective of this frame work is to establish the modeling and simulation of mix convection flow along a vertically heated sheet filled with water. Two important mechanisms: magneto-hydrodynamics and porous medium are also considered within the restricted domain of the fluid flow. Temperature is controlled with the wall temperature and then mathematical model is constructed in the form of PDEs. To determine the similarity solution results are obtained via two different techniques. Numerically solutions are obtained with the help of shooting technique and then validate with the help of optimal homotopy analysis method (OHAM). Obtained analytical and numerical results are validated graphically. Effect of emerging parameters are plotted for velocity and temperature profiles. It is found that for mixed convection parameter $(\xi <0)\text{,}$ velocity profile depicts the increasing behavior for various values of power index m. However, for $\xi >0\text{,}$ velocity profile shows the decreasing behavior with respect the parameter m. Temperature distribution in the restricted domain depicts the decreasing behavior for both m and $\xi$.     

Closed loop torque SVM-DTC based on robust super twisting speed controller for induction motor drive with efficiency optimization

This paper presents a space vector modulation (SVM) based Direct Torque Control strategy (DTC) for induction motor (IM) in order to overcome the drawbacks of the classical DTC. SVM can reduce the high torque and flux ripples by preserving a fixed switching frequency. This technique is known by the closed loop torque SVM-DTC. Moreover, the control scheme performance is improved by inserting a second order sliding mode super twisting controller in the outer loop for speed regulation. This nonlinear technique ensures a good dynamic and high robustness against external disturbance. Furthermore, the IM energy optimization is treated in the second objective of this paper. A proposed model based loss minimization strategy is presented for efficiency optimization. This strategy chooses an optimal flux magnitude for each applied load torque. The proposed optimized SVM-DTC algorithm will be investigated by simulation and real time implementation using Matlab/Simulink with real time interface based on dSpace 1104 signal card.     

Modeling of reverse osmosis flux of aqueous solution containing glucose

The aim of the paper is to model the permeate flux during reverse osmosis (RO) of a highly concentrated glucose solution using the osmotic pressure model. Such a model accounts for the effect of the concentration polarization phenomenon on the permeate flux. To apply this model the viscosity, the osmotic pressure of solution and the diffusion coefficient of glucose were estimated. Using mathematical simulation software, the values of mass transfer coefficient for different concentrations of glucose (5, 10, 15 and 20 wt%) and at different feed flow rate were determined. The experimental permeate flux values conducted on flat RO membranes (Type HR-99) agreed well with the values calculated by the osmotic pressure model, as shown by statistical analysis.     

Can distributed generation offer substantial benefits in a Northeastern American context? A case study of small-scale renewable technologies using a life cycle methodology

Renewable distributed electricity generation can play a significant role in meeting today's energy policy goals, such as reducing greenhouse gas emissions, improving energy security, while adding supply to meet increasing energy demand. However, the exact potential benefits are still a matter of debate. The objective of this study is to evaluate the life cycle implications (environmental, economic and energy) of distributed generation (DG) technologies. A complementary objective is to compare the life cycle implications of DG technologies with the centralized electricity production representing the Northeastern American context. Environmental and energy implications are modeled according to the recommendations in the ISO 14040 standard and this, using different indicators: Human Health; Ecosystem Quality; Climate Change; Resources and Non-Renewable Energy Payback Ratio. Distinctly, economic implications are modeled using conventional life cycle costing. DG technologies include two types of grid-connected photovoltaic panels (3 kWp mono-crystalline and poly-crystalline) and three types of micro-wind turbines (1, 10 and 30 kW) modeled for average, below average and above average climatic conditions in the province of Quebec (Canada). A sensitivity analysis was also performed using different scenarios of centralized energy systems based on average and marginal (short- and long-term) technology approaches. Results show the following. First, climatic conditions (i.e., geographic location) have a significant effect on the results for the environmental, economic and energy indicators. More specifically, it was shown that the 30 kW micro-wind turbine is the best technology for above average conditions, while 3 kWp poly-crystalline photovoltaic panels are preferable for below average conditions. Second, the assessed DG technologies do not show benefits in comparison to the centralized Quebec grid mix (average technology approach). On the other hand, the 30 kW micro-wind turbine shows a potential benefit as long as the Northeastern American electricity market is considered (i.e., oil and coal centralized technologies are affected for the short- and long-term marginal scenarios, respectively). Photovoltaic panels could also become more competitive if the acquisition cost decreased. In conclusion, DG utilization will represent an improvement over centralized electricity production in a Northeastern American context, with respect to the environmental, energy and economic indicators assessed, and under the appropriate conditions discussed (i.e., geographical locations and affected centralized electricity production scenarios).