Earticle

This paper introduces a novel method for the quality evaluation of resistance spot welds. The evaluation is based on computer vision methods, which allow nondestructive on-line real-time processing. The input of the system is the image of a weld imprint on a metal band which covers the electrodes against wear and soiling. In order to find the position of the resistance spot welds, we describe an image registration method based on geometric pattern matching for alignment system in metal parts. Further we extract features describing the shape of localized objects in segmented images .Using these shape descriptors (geometric feature) we classify the defects by Artificial Neural Network.

Presently, High Voltage AC transmission and High Voltage DC transmission systems are well established technologies for transmission of power. A new Low Frequency AC transmission system employs transmission at an intermediate frequency and thus, establishes itself in between these two alternatives. Low Frequency AC transmission system can transmit bulk power over long distance with low investment cost. This system is based on generation at low frequency and AC to AC conversion from nominal to low frequency using power electronic devices. This technology is more reliable and provides a cost effective solution for power transmission. This paper presents the feasibility of applying low frequency AC transmission technology to interface the wind farm to grid, which is a major issue. The wind power plant collection is DC based and connects transmission line with 12-pulse converter. This system is interfaced with main power grid with cycloconverter. Low Frequency AC transmission system is implemented with a suitable controller. The system design and control strategies are discussed. System performances are verified using MATLAB/SIMULINK.

DDFS (Direct Digital Frequency Synthesizer) is a new technique of frequency synthesizes which introduces the advanced digital processing theory into frequency synthesis. A direct digital frequency synthesizer is composed of a phase accumulator, an adder, an ROM for wave pattern saving, a D/A converter and a LPF (low pass filter). With the rapid development of VLSI, the speed of algorithm is required increasingly higher. This paper proposes a new frequency synthesizer by improving the structure of data storage which ensures the accuracy and speed. Rotation method was used to resolve the expected angle into many small rotation angles and sting wave symmetry principle was used to resolve the string wave. From point to area, the values in one quadrant were calculated and sampled and then the data was saved in ROM. Under the control of frequency, the data in ROM was read and then transferred to the D/A converter chip and the following low pass filter to achieve frequency synthesize. This algorithm could reduce the usage of ROM to increase the calculation efficiency.

The decomposition methods of surface electromyogram (SEMG) signals are mainly based on independent component analysis, blind source separation and the neural network. Because actual signals are the decomposition faced to single-guide signals, so the neural network decomposition method has more advantage. In this paper, we improve the composition of neural network based on the generation principle and decomposition significance of SEMG, and use this network to decompose the signal and to obtain a higher accuracy through the experimental data above. Beside, under medium-low shrinkage level the decomposition algorithm can successfully extract the dissemination information of motor unit action potentials in SEMG.