Design of Unskewed Interior Permanent Magnet Traction Motor with Asymmetric Flux Barriers and Shifted Magnets for Electric Vehicles

Abstract

Interior permanent magnet synchronous motors (IPMSMs) are commonly used in electric and hybrid electric vehicles. Nissan Leaf electric vehicle (EV) uses skewed-rotor IPMSM as a traction motor. This motor is considered as a benchmark in this work. Although, skewing improves the torque quality of the motor by reducing the torque ripple, it reduces the average torque and increases the motor manufacturing complexity and cost. This article proposes improvements to the benchmark motor torque quality without skewing. The proposed motor uses the same stator winding and rotor magnet topologies of the benchmark motor with the same geometric constraints and magnet volume. Modifications are applied to the placement of the magnets in the rotor and the shape of the flux barriers to achieve the performance requirements. The design procedure of the proposed unskewed design is illustrated. Moreover, the electromagnetic performance of the proposed design is investigated. The design shows competitive performance in terms of the average torque, torque ripple, cogging torque, and efficiency compared to the benchmark motor. The mechanical integrity of the design is also verified. The proposed design is found to be a suitable alternative to the benchmark traction motor with a reduced rotor weight and without skewing.     

Effects of Plasticizers,Antioxidants and Burning Rate Modifiers on Aging Performance of the HTPB/HMDI Composite Solid Propellant

The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.     

Experimental investigation of concrete-filled cold-formed high strength stainless steel tube columns

This paper presents an experimental investigation of concrete-filled cold-formed high strength stainless steel tube columns. The high strength stainless steel tubes had a yield stress and tensile strength up to 536 and 961 MPa, respectively. The behaviour of the columns was investigated using different concrete cylinder strengths varied from 40 to 80 MPa. A series of tests was performed to investigate the effects of the shape of the stainless steel tube, plate thickness and concrete strength on the behaviour and strength of concrete-filled high strength stainless steel tube columns. The high strength stainless steel tubes were cold-rolled into square and rectangular hollow sections. The depth-to-plate thickness ratio of the tube sections varied from 25.7 for compact sections to 55.8 for relatively slender sections. The columns had different lengths so the length-to-depth ratio generally remained at a constant value of 3. The concrete-filled high strength stainless steel tube specimens were subjected to uniform axial compression. The column strengths, load-axial strain relationships and failure modes of the columns were presented. The test strengths were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards that consider the effect of local buckling using an effective width concept in the calculation of the stainless steel tube column strengths. Based on the test results, design recommendations were proposed for concrete-filled high strength stainless steel tube columns.     

The use of spray-drying to enhance celecoxib solubility

The present research investigates the enhancement of the dissolution rate of celecoxib by using spray-drying to prepare a solid dispersion with various polymers, namely Kollicoat IR? (Kollicoat), polyvinyl alcohol (PVA) 22000, or polyethylene glycol 6000 (PEG). The investigated drug-to-polymer mass ratios were 1:1, 1:2, and 1:4 by weight. Hydroalcoholic or methylene chloride solvent systems were used. The obtained yields ranged from 65% to 78%, whereas the entrapment efficiencies were between 68% and 82%. The results revealed an increase in the dissolution rate of the prepared particles up to 200% within 20 min. The prepared particles were investigated using differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The increased dissolution rate was attributed to hydrogen bond formation between celecoxib and each polymer together with the reduced size of the formed particles offering a greater overall surface area. It was concluded that spray-drying may be considered a successful one-step technique to improve the dissolution rate of celecoxib when using Kollicoat, PVA, or PEG as the carrier polymer.     

Performance of composite girders strengthened using carbon fibre reinforced polymer laminates

This paper highlights the structural performance of steel–concrete composite girders strengthened using advanced composite laminates. Nonlinear 3-D finite element models have been developed to investigate the flexural behaviour and load carrying capacity of the girders. The composite laminates comprised carbon fibre reinforced polymer (CFRP) plates and sheets as well as steel reinforced polymer (SRP) sheets. The elastic modulus and ultimate tensile strength of the laminates varied from low to high 60–300 GPa and 700–3100 MPa, respectively. The nonlinear material properties of the strengthened composite girder components comprising concrete, structural steel beam, reinforcement bars, adhesive and composite laminates were incorporated in the finite element model. The interfaces between the composite girder components were also considered allowing the contact and bond behaviour to be modelled and the different components to retain its profile during the deformation of the strengthened composite girder. Furthermore, the load-slip characteristic of headed stud shear connectors was incorporated in the finite element models based on previous experimental and numerical investigations conducted by the author. The finite element models have been validated against published tests on composite girders strengthened using different advanced composite laminates and having different cross-section geometries, lengths, layers of laminates with different elastic moduli and ultimate tensile strengths, concrete strengths and structural steel strengths. The load carrying capacity of strengthened composite girders, load–vertical displacement behaviour and failure modes were predicted from the finite element analyses and compared against test results. Parametric studies were conducted to study the effects on the load carrying capacity and structural behaviour of strengthened composite girders owing to the change in the composite laminate elastic modulus, number of laminate layers, concrete strengths and structural steel strengths. The study has shown that the increase in the load carrying capacity and ductility of strengthened composite girders due to the increase in steel beam strength is significant with high strength concrete slab. Also, it has been shown that the increase in concrete strength offers a considerable increase in the initial stiffness of strengthened composite girders, while the increase in structural steel strength offers a considerable increase in the stiffness of strengthened composite girder in the post-yielding stage.     

Numerical simulation of concrete encased steel composite columns

This paper investigates the behaviour of pin-ended axially loaded concrete encased steel composite columns. A nonlinear 3-D finite element model was developed to analyse the inelastic behaviour of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement of the concrete encased steel composite columns. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered that allowed the bond behaviour to be modeled and the different components to retain their profile during the deformation of the column. Furthermore, the initial overall (out-of-straightness) geometric imperfection was carefully incorporated in the model. The finite element model has been validated against published experimental results. The main objective of the study was to understand the structural response and modes of failure of the columns and to assess the composite column strengths against current design codes. The study covered slender, non-slender, stub and long concrete encased steel composite columns. The concrete strengths varied from normal to high strength (20-110 MPa). The steel section yield stresses also varied from normal to high strength (275-690 MPa). Furthermore, the variables that influence the composite column behaviour and strength comprising different slenderness ratios, concrete strength and steel yield stress were investigated in a parametric study. It is shown that the increase in structural steel strength has a small effect on the composite column strength for the columns having higher relative slenderness ratios due to the flexural buckling failure mode. The composite column strengths obtained from the finite element analysis were compared with the design strengths calculated using the American Institute for Steel Construction AISC and Eurocode 4 for composite columns. Generally, it is shown that the EC 4 accurately predicted the design strength for the concrete encased steel composite columns having a concrete cylinder strength of 30 MPa and structural steel yield stresses of 275 and 460 MPa, which are in the limits of the code, which otherwise, was generally conservative. The AISC predictions were quite conservative for all the concrete encased steel composite columns.     

Real-time packet loss prediction based on end-to-end delay variation

The effect of packet loss on the quality of real-time audio is significant. Nevertheless, Internet measurement experiments continue to show a considerable variation of packet loss, which makes audio error recovery and concealment challenging. We propose a novel framework to predict packet loss and congestion, based on measurements of end-to-end delay variation and trend, enabling proactive error recovery and congestion avoidance. Our preliminary simulation and experimentation results with various sites on the Internet show the effectiveness and the accuracy of the Loss Predictor technique.     

DWT-based joint antenna selection for correlated MIMO channels

This paper proposes a new discrete wavelet transform (DWT)-based joint antenna selection scheme for spatially correlated multiple-input multiple output (MIMO) channels. To reduce the severe performance degradation of the traditional antenna selection schemes in correlated channels, a new scheme which employ joint antenna selection (JAS) at both link ends algorithm and embed DWT operations in the receiver-end RF chains is proposed. Through extensive simulations it is demonstrated that the proposed DWT-based joint antenna selection has significant improvement of the capacity for both i.i.d and correlated MIMO channels, while requiring only a minor hardware overhead and low computational complexity for the DWT operations. Moreover, it is shown that the capacity associated with DWT-based JAS is higher than the system employing DWT-based receive antenna selection (RAS) only. This is achieved in i.i.d. and correlated MIMO channels.