Iranian Journal of Electrical and Electronic Engineering
Volume:14 Issue: 3, Sep 2018

In this paper, a new guidance law is designed to improve the performance of a homing missiles guidance system in terminal phase. For this purpose first of all, the two dimensions equations of motion are formulated, then the approximation dynamic of missile control loop is added to these equations which are nonlinear whit unmatched uncertainty. Then, a new adaptive back-stepping method is developed in order to control this system. An adaptive term is used in the control law that is converged to the uncertainty. This convergence is proved based on Lyapunov stability theorem. Therefore using this adaptive term in the control law can be eliminated the uncertainty. Based on this algorithm, a new guidance law is designed. Then its performance is compared with common guidance laws in a guidance loop simulation in the presence of control loop dynamics.

In this paper, after a brief overview on laser warning system (LWS), a new structure for an optical array that is used in its optical subsystem is introduced. According to the laser threats’ wavelengths (0.5 – 1.6 µm) and our desirable field of view (FOV), we used 6 lenses for gathering the incident radiation and then optimized the optical array. Lenses’ radius, their semi diameter, their distance from each other, their thickness and the kind of glass used in them was chosen in which we access a very high transmission coefficient. Also the optical reflection and absorption of the array decreases at the same time. After optimization, the obtained optical transmission in our desirable FOV is up to 82% and the obtained optical reflection and absorption is less than 15%. Total aberration of the incident ray decreased notably and the results showed that this parameter is less than 2µm. The laser spot diameter which is focused on the detector is smaller than 400 µm in the worst case which is the laser radiation with 1.54 µm wavelength and field of 10 degrees. Total track of the array is 66.819 mm and effective focal length and F/# parameter are as small as possible which leads to high quality of the light’s focus on the detector and smaller dimension and lighter weight for the receiver. Using optical devices with such appropriate arrangement and very good optical transmission coefficient, the offered structure has a remarkable signal to noise ratio (SNR) which is up to 160 dB. The receiver’s operation in far distances from laser sources (beyond 15 km) and in hazy conditions and low temperatures is quite suitable as well.

Due to widespread use of Global Positioning System (GPS) in different applications, the issue of GPS signal interference cancelation is becoming an increasing concern. One of the most important intentional interferences is spoofing signals. An effective interference (delay spoof) reduction method based on adaptive filtering is developed in this paper. The principle of method is using adaptive filters to eliminate interference, obtain an estimate of interfering signal and subtract that from the corrupted signal. So, what remains in the output is the desired signal. Here, for updating the filter coefficients adaptive algorithms in both time (statistical and deterministic) and transform domain will be studied. The proposed adaptive filter is applied to a batch of spoofing GPS data in pseudo-range level. The results indicate that all investigated algorithms are able to reduce positioning steady-state miss-adjustment up to 70 percent. In this context, the variable step-size least mean square algorithm performs better than others do.

This paper presents a high-speed, low-power and low area encoder for implementation of flash ADCs. Key technique for design of this encoder is performed by convert the conventional 1-of-N thermometer code to 2-of-M codes (M = ¾ N). The proposed encoder is composed from two-stage; in the first stage, thermometer code are converted to 2-of-M codes by used 2-input AND and 4-input compound AND-OR gates. In the second stage by two ROM encoders, 2-of-M codes determine n-1 MSB bits and one LSB bit. The advantages of the proposed encoder rather than other similar works are high speed, low power consumption, low active area, and low latency with same bubble error removing capability. To demonstrate the mention specifications, 5-bit flash ADCs with conventional and proposed encoders in their encoder blocks, are simulated at 2-GS/s and 3.5-GS/s sampling rates in 0.18-μm CMOS process. Simulation results show that the ENOB of flash ADCs with conventional and proposed encoders are equal. In this case, the proposed encoder outputs are determined almost 30-ps faster rather than the conventional encoder at 2-GS/s. Also, the power consumptions of the conventional and proposed encoders were 17.94-mW and 11.74-mW at 3.5-GS/s sampling rate from a 1.8-V supply, respectively. Corresponding, latencies of the conventional and proposed encoders were 3 and 2 clock cycles. In this case, number of TSPC D-FFs and logic gates of the proposed encoder is decreased almost 39% compared to the conventional encoder.

In this paper we propose a new configuration of the wind farm connecting with an electrical grid. The proposed Wind Energy Conversion System (WECS) is based on a two stages six-leg matrix converter using to drive a two Doubly Fed Induction Machines operating at different wind speeds. Each Doubly Fed Induction Generator (DFIG) is controlled through the rotor currents using the Finite Set Model Predictive Model (FS-MBC). The proposed control method selects the optimal switching state of the converter that minimizes the cost function where it represents the desired behavior of the system. The optimal voltage vector is then applied to the output of the power converter. The most advantage of the proposed control is its simplicity in implementation, since the method avoids the use of any linear or nonlinear controllers except for the external speed loop and there is no need for any type of modulator such as in PWM or SVM modulation. A cost function is formulated according to desired performance such as regulation of the stator active and reactive powers of the DFIGs and reactive power in the filter side. The control algorithm selects and applies the optimal voltage vector to the DFIG rotor terminals. The supervision algorithm distributes the active and reactive power references in proportional way for each wind turbines. From a safety point, this algorithm provides each wind turbines still operate far from its limits. The performance of a six leg IMC in WECS chain is evaluated in term of a good tracking performance.

Brushless permanent magnet surface inset machines are interested in industrial applications due to their high efficiency and power density. Magnet segmentation is a common technique in order to mitigate cogging torque and electromagnetic torque components in these machines. An accurate computation of magnetic vector potential is necessary in order to compute cogging torque, electromagnetic torque, back electromotive force and self/mutual inductance. A 2D analytical method for magnetic vector potential calculation in inner rotor brushless segmented surface inset permanent magnet machines is proposed in this paper. The analytical method is based on the resolution of Laplace and Poisson equations as well as Maxwell equation in a quasi- Cartesian polar coordinate by using sub-domain method. One of the main contributions of the paper is to derive an expression for the magnetic vector potential in the segmented PM region by using hyperbolic functions. The developed method is applied on the performance computation of two prototype surface inset magnet segmented motors with open circuit and on load conditions. The results of these models are validated through FEM method.

Cable termination faults are problematic in electrical networks almost always. Technology has solved problems somewhat, but there are many annual reports about damaged cable terminations. For analyzing the problems, faults in two regional electricity companies are studied. At first step, damaged cable terminations are analyzed statistically and grouped according to their problems. Then, some of the damaged cable terminations are checked to classify vulnerable areas. The investigation is completed by simulation, analysis and study of equivalent circuit. Conclusions underline important points which can be helpful for reducing the damages.

Model-based predictive control (MPC) is one of the most efficient techniques that is widely used in industrial applications. In such controllers, increasing the prediction horizon results in better selection of the optimal control signal sequence. On the other hand, increasing the prediction horizon increase the computational time of the optimization process which make it impossible to be implemented in real time. In order to solve this problem, this paper presents an improved strategy in the field of nonlinear MPC (NMPC) of the permanent magnet synchronous motor (PMSM). The proposed method applies a sequence of reduction weighting coefficients in the cost function, over the prediction horizon. By using the proposed strategy, NMPC give a more accurate response with less number of prediction horizon. This means the computational time is reduced. It also suggests using an incremental algorithm to reduce the computational time. Performance of the proposed Nonlinear MPC (NMPC) scheme is compared with the previous NMPC methods via simulations performed by MATLAB/Simulink software, in permanent magnet synchronous motor drive system. The results show that the use of proposed structure not only lowers prediction horizon and hence computational time, but also it improves speed tracking performance and reduces electromagnetic torque ripple. In addition, using the incremental algorithm also reduces the computational time which makes it suitable for real-time applications.

Recently, smart grids have been considered as one of the vital elements in upgrading current power systems to a system with more reliability and efficiency. Distributed generation is necessary for most of these new networks. Indeed, in all cases that DGs are used in distribution systems, protection coordination failures may occur in multiple configurations of smart grids using DGs. In different configurations, there are various fault currents that can lead to protection failure. In this study, an optimal DG locating and Thyristor-Controlled Impedance (TCI) sizing of resistive, inductive, and capacitive type is proposed for distribution systems to prevent considerable changes in fault currents due to different modes of the smart grid. This problem is nonlinear constrained programming (NLP) and the genetic algorithm is utilized for the optimization. This optimization is applied to the IEEE 33-bus and IEEE 69-bus standard distribution systems. Optimum DG location and TCI sizing has carried out in steady fault currents in the grid-connected mode of these practical networks. Simulation results verify that the proposed method is effective for minimizing the protection coordination failure in such distribution networks.

Disk Type Variable Reluctance (DTVR) resolvers have distinguished performance under run out fault comparing to conventional sinusoidal rotor resolvers. However, their accuracy under inclined rotor fault along with different types of eccentricities includes static and dynamic eccentricities are questioned. Furthermore, due to thin copper wires that are used for signal and excitation coils of resolver there is high risk of short circuit fault in the coils. So, in this study the performance of the sinusoidal rotor DTVR resolver under the mentioned faults are studied. The quality of output voltages along with position error of the sensor is discussed. 3-D time stepping finite element method is used to show the effect of different faults. Finally, the prototype of the studied resolver is constructed and tested. The employed test bed is built in such a way that is able to apply controllable level of different mechanical faults. Good agreement is obtained between the finite element and the experimental results, validating the success of the presented analysis.