Experimental determination of mechanical parameters in sensorless vector-controlled induction motor drive

High-performance industrial drives widely employ induction motors with position sensorless vector control (SLVC). The state-of-the-art SLVC is first reviewed in this paper. An improved design procedure for current and flux controllers is proposed for SLVC drives when the inverter delay is significant. The speed controller design in such a drive is highly sensitive to the mechanical parameters of the induction motor. These mechanical parameters change with the load coupled. This paper proposes a method to experimentally determine the moment of inertia and mechanical time constant of the induction motor drive along with the load driven. The proposed method is based on acceleration and deceleration of the motor under constant torque, which is achieved using a sensorless vector-controlled drive itself. Experimental results from a 5-hp induction motor drive are presented.     

Identification of large scale distributed parameter systems—some simplifications in the multidimensional Poisson moment functional (MDPMF) approach

This paper is concerned with two practically important aspects of identification of large scale distributed parameter systems by the multidimensional Poisson moment functional (MDPMF) method (Saha and Prasada Rao 1980). The existing methods of (i) development and diagrammatic representations of the relations among the MDPMFs of partial derivative terms and those of the original multivariable function, and (ii) elimination of the effects of boundary functions and their partial derivatives from the identification equations, become extremely unwieldy as the order and dimensions of the model increase. This paper suggests alternative techniques in these two situations, leading to a simplification of the algorithm and an enormous reduction of the related analytical and computational burden. In the former situation, the suggested alternative uses the concept of separated variables. In the latter, the boundary function effects are estimated and then inserted into the algorithm to simplify it.     

Improved cuckoo search with particle swarm optimization for classification of compressed images

The need for a general purpose Content Based Image Retrieval (CBIR) system for huge image databases has attracted information-technology researchers and institutions for CBIR techniques development. These techniques include image feature extraction, segmentation, feature mapping, representation, semantics, indexing and storage, image similarity-distance measurement and retrieval making CBIR system development a challenge. Since medical images are large in size running to megabits of data they are compressed to reduce their size for storage and transmission. This paper investigates medical image retrieval problem for compressed images. An improved image classification algorithm for CBIR is proposed. In the proposed method, RAW images are compressed using Haar wavelet. Features are extracted using Gabor filter and Sobel edge detector. The extracted features are classified using Partial Recurrent Neural Network (PRNN). Since training parameters in Neural Network are NP hard, a hybrid Particle Swarm Optimization (PSO) – Cuckoo Search algorithm (CS) is proposed to optimize the learning rate of the neural network.     

Preparation and bioactivity Of SiO2 functional films on titanium by PACVD

SiO2 functional films were deposited on the surface of titanium by plasma assisted chemical vapour deposition（PACVD） and the composition of films was studied by XPS. Samples deposited with SlOE films were immersed in different concentration simulated body fluid（SBF） for biomimetic deposition of hydroxyapatite（HA）. The results show that SiO2 functional films deposited on titanium surface with PACVD have good bioactivity. Hydroxyapatite is formed while titanium coated with SlOE is immersed in simulated body fluid for seven days.     

Machining characteristics of fine grained AZ91 Mg alloy processed by friction stir processing

AZ91 Mg alloy was considered and friction stir processing (FSP) was adopted to achieve grain refinement to investigate the effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds. Super saturated AZ91 Mg alloy was obtained after FSP and the grain refinement was achieved from (166.5±8.7) µm to (21.7±13.5) µm. Surprisingly, hardness reduced for FSP AZ91 Mg alloy (88.95±6.1) compared with AZ91 alloy (108.2±15.6), which was attributed to the reduced secondary phase. However, the mean cutting force for FSP-treated (FSPed) AZ91 Mg alloy was marginally increased. The edge damage of the drilled holes was lower for FSPed AZ91 Mg alloy compared with unprocessed AZ91 Mg alloy. Hence, it can be understood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achieved in machining of AZ91 Mg alloy.     

Effect of loading condition,specimen geometry,size-effect and softening function on double-<Emphasis Type="BoldItalic">K</Emphasis> fracture parameters of concrete

This paper presents numerical investigation of the influence of the specimen geometry, loading condition, size-effect and softening function of concrete on double-K fracture parameters. The input data needed for computation of the double-K fracture parameters are obtained from the well-known version of Fictitious Crack Model (FCM). FCM is developed for three standard specimens: three-point bend test, compact tension specimen and four-point bend test of size range 100–600 mm at relative size of initial crack length 0.3. The analysis of numerical results shows some interesting behaviour of double-K fracture parameters.     

Separately balanced realization of two-dimensional separable-denominator transfer functions†

In this paper a method is developed for the computation of a separately balanced state-space model for a given two-dimensional transfer function with separable denominator. The procedure relies on the eigenvalue/eigenvector decomposition (or singular-value decomposition) of two real symmetric matrices determined directly from the given transfer function.     

Complex permittivity of soil and water mixtures at 9 GHz

Measurements of the complex permittivity of many soil samples were conducted using the evanescent waveguide technique at 9 GHz. The complex permittivity was taken as a function of moisture content. The experimental results were interpreted using Wiener's theory for dielectric mixtures to evaluate the degree of binding of water in soils.