Recent Advances in Electrical & Electronic Engineering - Volume 11, Issue 3, 2018

Background: Given that the device possibly suffers the abnormal condition before it finally reaches the critical failure threshold in the degradation process. Methods: In this paper, an abnormal failure judgment method of the device is proposed based on the performance degradation data itself. In this method, the device degradation process is considered to be an independent incremental process by probabilistic approximation, and then according to Grubbs criterion, all of degradation quantity is divided as two population, and an abnormal failure occurs only if a new observed sample belongs to abnormal class, and conversely, and no abnormal failure occurs. Results: The standard deviation values of all the degradation quantity can be then obtained by dealing with the performance degradation dates between adjacent moments, statistically. In addition, we still estimate the cumulative failure probability of the device, and consider the accumulated cost losses arising from the continuous degradation, and then the expected maintenance cost model is established. Conclusion: Finally, a practical case on a certain type of Electric Motor Unit (EMU) brake pad thickness analysis shows that the method presented is quite effective and feasible.

Background: This work addresses the maximum edge weight clique problem (MEWC), an important generalization of the well-known maximum clique problem. Methods: The MEWC problem can be used to model applications in many fields including broadband network design, computer vision, pattern recognition, and robotics. We propose a random key genetic algorithm to find good quality solutions for this problem. Computational experiments are reported for a set of benchmark problem instances derived from the DIMACS maximum clique instances. Results: The results obtained show that our algorithm is both effective and efficient, as for most of the problem instances tested, we were able to match the best-known solutions with very small computational time requirements.

Background: Chirp signals are widely applied in radar systems, biomedicine, seismic prospecting and many other fields. It is difficult to estimate fast and accurately original frequency and chirp rate of chirp signals because of the existence of stable noise in the echo signals. Methods: In this paper, a parameter estimation method for chirp signals is proposed. Firstly, the impulse characteristics of stable noise in the echo signals is suppressed. Secondly, chirp rate of chirp signals is easily calculated by Quadratic Phase Function (QPF) method and the order of Fractional Fourier Transform (FRFT) can be determined. Results: Finally, the original frequency of chirp signals can be estimated by FRFT method. Simulation results demonstrate that the proposed method can achieve higher accuracy than the single FRFT method and the running speed of the proposed method is nearly three times faster than the single FRFT method.

Background: The stationary monocular visual control is a major mode of robot assembly. In this mode, the viewing field is stationary and the target is not detached. Methods: Self-calibration based on the fundamental matrix is first performed on the camera to obtain its linear interior parameters in this paper. Next, a novel stage-wise visual control method is proposed, which adopts different control strategies at different stages. Results: The location-based visual control strategy is used for the vertical plane, and the image-based visual control strategy is used for the horizontal plane. Guidance experiment is then conducted to verify the accuracy and effectiveness of the proposed control method.

Background: During the microwave heating process, the dielectric property of the heated media changes with temperature and time, and the change of temperature at its Low-Temperature (LT) stage and High-Temperature (HT) stage shows different characteristics obviously. Sometimes, hotspots and thermal runaway occur. Methods: Regular control methods are difficult to effectively control the temperature during the whole microwave heating and drying process. To solve this problem, a microwave source power control method based on piecewise fussy PID is proposed. This method uses the k-means clustering to divide temperature change of the heated material into LT stage and HT stage, and adopts fuzzy PID control strategies of different levels and rules based on different temperature change characteristics. Results: This paper studied the fuzzy controller design for the LT and HT stages, respectively and illustrates the engineering way to realize this control method. The simulation result shows that the piecewise fuzzy PID controller reduces the temperature overshoot of the microwave heating process to 1/4 of a regular PID controller and shortens the time for the temperature to reach the target value to 1/3 of the original time. This method also shows good robustness. Conclusion: Therefore, this method, when applied to active control of microwave power, can effectively avoid thermal runaway prone in the heating process and improve the safety and reliability of the microwave heating system.

Background: Crystal oscillator plays a major role in the RF system as the frequency source while often encountered in vibration condition. In order to maintain the normal operation of the system, implementing estimation and prediction is necessary as a strategy based on performance degradation. However, there is little research addressing the issues associated with health status evaluation and Residual Useful Life (RUL) prediction of the RF crystal oscillator. Methods: This paper proposes a method to assess the health status and the RUL tested in a case study under vibration condition. Conclusion: Our approach utilizes acceleration sensitivity(AS) as indicator and the M-estimation based optimally-pruned extreme learning machine (M-OPELM) as technology, obtaining ideal predicting results according to the actual RUL.

Background: We studied how to control a dual-ring Er-doped fiber laser by shifting the laser loss, pressuring the chaotic behavior of the laser to a periodic state or multi-periodic states. Methods: We present a model of single-parameter control of the laser. When a periodic signal adjusts the loss of one ring, the dynamic behavior of the laser can stabilize into period-one states and the dualring output variation locks at the adjusting signal frequency where two rings can emit cyclic pulses. We find such a control-locking-frequency region, indicating that the chaotic dual-ring Er-doped fiber laser can be effectively controlled. We also find a locking-half-frequency region, in which the dual-ring output locks at a half-frequency of the adjusting signal. When the loss shifts between two values, the laser can be deduced to multi-periodic states or be pressured into two single-period states where two rings cam emit cyclic pulses. We also find that the controlled laser can exhibit dual dynamics, in which the dual-ring shows two dynamic behaviors, such as, one ring showing a period-two state, while the other ring shows a period-three state or stabilizes to a period-one state. Results: Our results indicate that the chaos- of a dual-ring erbium-doped fiber laser can be controlled.

Background: A new methodology is developed for bipartite matching decision, in which preferences of the agents from two sides are incomplete ordinal relations and matching aspirations. The bipartite matching problem with incomplete ordinal relations and matching aspirations is firstly provided. Methods: In the presented methodology, the incomplete ordinal relations are translated to the incomplete Borda counting matrixes, and matching aspirations are determined based on theory analysis. According to the incomplete Borda counting matrixes, the matching aspiration matrix, a bipartite matching model under the condition of one-to-one matching is developed. Results: The bipartite matching scheme can be obtained by solving the matching model. Conclusion: In the end, an example is used to illustrate the application of the presented methodology.

Background: Power quality problems are identified in voltages and currents and are, mainly, classified in harmonics, transients, and voltage sags. Besides current harmonics, voltage sags is the most common type of issue especially with manufacturing consumers. To define voltage sags, they are shortduration reduction in the rms voltage and they are mostly induced by remote short circuit. Determining the critical distance of a fault that will cause certain pre-defined voltage sag at a specific bus is uncomplicated and simple in radial systems. However, in a meshed power system, determining the critical distance of a fault at specific line that will cause predefined voltage sag magnitude is not as simple and has not been resolved by any of the existent studies. The aim of this paper is to provide proper solution to find the critical distance in meshed power system. Methods: The method has been applied and tested using a 6-bus system. Result: A proper solution is achieved in this paper regarding the critical distance in a Meshed Power System and the results shows the efficiency of the method used.

Background: Demagnetization limitation of permanent magnets is the maximum demagnetization rate, and it is not only influenced by motor overload capacity, but also influenced by winding limit temperature and permanent magnet limit temperature. It has important significance to study the influence of demagnetization limitation on motor whole life cycle management. Methods: In this paper, the finite element method, the analytical algorithm and the equivalent thermal network method were adopted. Aiming at the mechanism research on the demagnetization limitation of permanent magnet servo motors (PMSM), the demagnetization factor is proposed, which can reflect the relationship between the demagnetization and electromagnetic performance of PMSMs, and it can also indicate the influence of overload capacity on demagnetization limitation. Based on the calculation of motor losses, the temperature variation of the motor was studied in depth. Considering the temperature rise caused by heat accumulation effect, the demagnetization limitation of permanent magnets was obtained. Combined with the constraint of the winding insulation grade and limit temperature of permanent magnets on demagnetization limitation, the optimal combination of armature windings and permanent magnets was determined. Results: The accuracy of calculation results was verified by experiment to prove the correctness of the research on demagnetization limitation. Conclusion: The research on motor demagnetization can provide some useful reference for motor design and maintenance.

Background: To achieve the goal of automatic generation control of better system frequency regulation and to control the tie-line active power deviations, this paper presents a genetic algorithm optimized model predictive control (GA-MPC) scheme for load frequency regulation of two area interconnected power systems. Methods: Three different power systems: thermal-thermal system, thermal-nuclear system and thermalgas system, interconnected by tie-lines, have been considered to assess the performance of the proposed control scheme (GA-MPC). Inorder to evaluate the effectiveness of the proposed controller, a comparitive analysis is performed between the controller scheme, auto-tuned PID controller and autotuned MPC, in terms of performance indices namely: overshoot/undershoot and settling time of the transient response of the test systems. Sensitivity analysis has also been performed to test the efficacy and robustness of GA-MPC, MPC and PID controllers, when subjected to variations in loading conditions, tie-line synchronizing coefficient and turbine time constant. Also, dynamic response of the thermal-thermal system with GA based MPC controller is studied and analysed in the presence of nonlinear constraints namely: generation rate constraint (GRC) and governor deadband. Results: The simulation results establish the superiority of GA based MPC over auto-tuned MPC and auto-tuned PID controllers, in maintaining the output power generation and minimization of the area control error. The sensitivity analysis shows that the proposed scheme is robust and insensitive to the variations in load disturbances and system parameters. Also, the considered control scheme is able to effectively handle the system non-linearities. Conclusion: The presented method is quite effective in controlling the system frequency and tie-line power flow in the presence of system non-linearities and sudden disturbances.

Background: Recently, the incorporation of Distributed Static-Compensator and Distributed Generation in distribution system has become essential for the distribution companies to be adopted for the overall system benefit. In this study, the optimal sizing and siting of these devices are conducted in distribution system using Modified Shuffled Frog Leaping Algorithm to maximize the technical, economic, and environmental benefits. Methods: New frog leaping rules are proposed in the Modified Shuffled Frog Leaping Algorithm to enhance the overall performance of the algorithm. Innovative formulas such as Revamp Voltage Stability Index, Benefit Cost Ratio, and Environmental Benefit Index are formulated to assess the technical, economic, and environmental aspects of the device. To judge the feasibility and accuracy of the proposed technique, it is applied on 33-bus and 69-bus distribution system considering different load models and after that, the performances of the devices are analyzed on the basis of the techno-economic and environmental impacts. Results: Furthermore, the overall system benefit is also investigated after placing both the devices simultaneously. The proposed method is compared with other evolutionary algorithms to prove its superiority. Conclusion: This entire analysis will facilitate the power industry to choose an optimal strategy for the overall benefit of the system.

Background: It presents a kind of multi-class image classification algorithm which is combined with Best Versus Second Best (BVSB) active learning technology and improved self-training semi-supervised learning technology. Methods: The algorithm integrates the advantages of active learning; semi-supervised learning and extreme learning machine simultaneously. It has better performance than that of single algorithm when it is used in different sets of image target recognition. Results: In addition, it also discussed the influence of various parameters on the algorithm performance in the experimental parts, and made related analysis of semi-supervised learning algorithm based on SVM (Support Vector Machine); the experimental results verified the superiority of proposed algorithm.

Background: In the traditional design, parameters of the gear pump cover are based on the minimum thickness and gear shaft parameters, with shortcoming of wasting material and designing roughly. It is necessary to verify the advanced nature of improvement by the contrast in the changes of dynamic characteristics and the fatigue life of before and after changes gear pump cover optimization. Methods: the dynamic characteristics is analyzed by ANSYS. Different kinds of hydraulic loads, which influence the life of gear pump cover, are set to change with instantaneous flow or the form of ANSYS provided various variations. The time-amplitude curves are obtained in MATLAB. Frequencyamplitude curve of different hydraulic loads are obtained by FFT algorithm in MATLAB. The fatigue life of gear pump cover are analyzed by ANSYS. Results: By the simulation of ANSYS, the maximum equivalent stress of gear pump cover is reduced by 67%, and the first order of total displacement response is decreased by 42%. Under the hydraulic shock, which changes with the instantaneous flow, the fatigue life of pump cover is improved by 1491 times after the optimization. When the impact of oil is superimposed by the multi-frequency impact, it will result in the fatigue damage of gear pump cover which is more serious. Conclusion: The dynamic characteristics and the fatigue life of gear pump cover are improved significantly after being optimized. The effects on the life of the pump cover after optimization of different kinds of oil pressures changed with the forms of different loads, are improved significantly in different degrees. The study of oil pressure impact on the life of the pump cover indicates that the pump cover fatigue life is significantly reduced when the oil pressure changes drastically. In the design of the gear pump, the hydraulic shock on gear pump cover, which is changed by the instantaneous flow, should be taken into account.

Background: The hardware implementation of neural networks has been the focus of the researchers during the last few years. The main aim is to obtain all the features possessed by the biological neural networks not possible through software approach. In the past few years, several attempts have been made for the hardware implementation of neural networks but most of them have been designed using off-the-shelf components working at high voltages. Besides, the reported topologies are not integrable on the IC along with the other systems. Methods: The paper presents a low-voltage sinh-domain implementation of neural networks using nonmonotonic Liao's activation function. The employment of the activation function has an added advantage that the non-linearly separable logic function such as XOR and XNOR can also be implemented using single layer perceptron which otherwise is not possible with hard limit, Sigmoidal and tanh activation functions. Besides, unlike the conventional digital VLSI design, the same neural network can be trained for different logic function by employing different weights and biases, which has been demonstrated in the paper. Results: To verify the functionality of the designed neural networks, back propagation algorithm in MATLAB environment was used to train them for various digital logic functions. Before applying the calculated weights, these were normalized by DC bias current of the circuits. The performance of the circuits has been verified through HSPICE simulation software using 0.35μm CMOS process file. Conclusion: A low-voltage, integrable implementation of the neural network using sinh-domain technique has been presented. The non-monotonic activation function was employed which made it possible to design XOR and XNOR functions using only single layer perceptron. The demonstration of obtaining different logic functions from the same neural network was also presented in the paper. The results obtained clearly verify the proper functioning of the proposed implementations.