Amirkabir International Journal of Electrical & Electronics Engineering
Volume:51 Issue: 2, Summer-Autumn 2019

In this paper, we design an attractive algorithm aiming to classify moving targets including human, animal, vehicle and drone, at ground surveillance radar systems. The non-stationary reflected signal of the targets is represented with a novel mathematical framework based on behavior of the signal components in reality. We further propose using the generalized linear chirp transform for the analysis stage. To enhance the classification performance, the rotation invariant pseudo Zernike-Moments are extracted from the time-frequency map. Consequently, the obtained features are trained to the k-NN classifier. In the numerical experiments we show the superiority of the proposed method in comparison with the existing recent counterparts, for both performance as well as the computational complexity. The results indicate that the proposed method obtains the rate of 95% accuracy in classification performance, when the signal to noise ratio is higher than 25dB. In fact, a rotating propeller on a fixed-wing aircraft, the multiple spinning rotor blades of a helicopter, or an Unmanned Aerial Vehicle (UAV); the vibrations of an engine shaking a vehicle; an antenna rotating on a ship; the flapping wings of birds; the swinging arms and legs of a walking person; and many other sources are the source of micromotion, are known as the micro-Doppler, and can be used for target classification and reduction of the sensor false alarm rate.

L-band electromagnetic scattering from two-dimensional random rough sea surfaces are calculated by first- and second-order Small-Slope Approximation (SSA1, 2) methods. Both analytical and numerical computations are utilized to calculate incoherent normalized radar cross-section (NRCS) in mono- and bi-static cases. For evaluating inverse Fourier transform, inverse fast Fourier transform (IFFT) is performed to reduce computational burdens. For the SSA simulations, surface dimensions are large as all sea spectrum components are included. Considering the integration domain of the Analytical SSA (A-SSA), it requires huge computer memories especially at high frequencies and high wind speeds. In this regard, the numerical SSA (N-SSA) employs less memory, however, it requires more running time because of Monte-Carlo simulations. By applying tapered incident plane wave (TPW) to the N-SSA, dimensions are reduced to enhance computational efficiency in comparison with the A-SSA. As a result, the N-SSA with the TPW is applicable to high wind speeds, where the A-SSA may be limited. To validate the SSA, Results are compared with those from the method of moments (MoMs) in VV polarization. The results of different methods show good agreements at low wind speeds and incident angles less than 60 degrees. At high wind speeds, there are some differences between the SSA1 and the SSA2 recommending on the SSA2 to use, due to the higher order of accuracy

This paper presents a low loss and high selective lowpass filter which is implemented using suspended stripline (SSL) technology. The proposed structure is comprised of a 13th order generalized Chebyshev lowpass filter which enjoys integrated waveguide-to-SSL transitions. This filter is designed and fabricated to be used as lowpass channel of a U-band diplexer employed in frontend of a U-band down converter. Designed filter has cut-off frequency of 50 GHz with high performance out-of-band rejection and wide stopband associated with stepped-impedance resonators realized using generalized Chebyshev prototype. Final design of filter is analyzed and optimized using 3D full-wave simulator. Filter circuit is realized on one side of a 0.127 mm-thick TLY5 substrate with dielectric constant of 2.2, which is suspended symmetrically in a waveguide channel with height of 0.961 mm and maximum width of 2 mm. Higher order modes propagation effects on filter performance are investigated to have proper single mode operation. In addition, parametric study of SSL is done to predict probable malfunctioning due to misalignment or other fabrication and packaging errors. Measurement results also are presented to verify performance of filter. The filter displays a maximum passband insertion loss of 2 dB and a return loss of better than 10 dB over the passband. Band-edge steepness reaches over 50 dB at 5 GHz away from cut-off and out-of-band rejection is higher than 45 dB at entire stopband, which are in good agreement with simulation.

The future distribution network comprising different energy carriers will include small-scale energy resources (SSERs) and loads, known as a Networked multi-carrier microgrid (NMCMG). This concept not only leads to an efficient reduction in operation costs, but also encompasses the energy transformation between gas and electric networks at combined nodes, as well as district heating networks. In this paper, the combined natural gas and electricity optimal power flow (GEOPF) is employed to represent the inter-area transmission networks. The optimal GEOPF of NMCMG, which is represented as an energy hub system, is formulated as an optimization problem that is solved by applying a mixed-integer nonlinear programming (MINLP) technique. The proposed model is capable of minimizing the system costs by utilizing various sources and integrating the multiple-energy infrastructures as well as handling the energy management of the network. Simulations are performed on a system with three microgrids including combined heat and power (CHP), photovoltaic arrays, wind turbines, and energy storages in order to fulfill the required multiple demands. In the proposed model, microgrids are in grid-connected mode in order to exchange power when required. The results of the simulation demonstrate that GEOPF guarantees the regulation of power demand and power transaction in the multi-carrier microgrid (MCMG) and the main grid.

Axial field flux switching motor with sandwiched permanent magnet (AFFSSPM) is a novel of flux switching motor. Based on the vector control method, the mathematical model of the AFFSSPM is derived and the operating performance of the AFFSSPM in the overall operating region is investigated.A novel control method for the AFFSSPM drive system, including the id =0, maximum torque per ampere, constant flux linkage, unity power factor control and flux-weakening strategy, is proposed. A prototype of the 12/19 poles AFFSSPM motor is manufactured and tested. moreover, validity and feasibility of the proposed method were verified by experiments.The AFFSSPM motor is one of the most efficient motors but control scheme of the 12S/19P AFFSSPM motor has not been specially reported to date. Thus, in this paper, we report on the operating performance of the AFFSSPM in the overall operating region is investigated.Recently, suitable configuration and control strategy of the electric machines have been of the important research areas. Characteristics such as high-reliability, high-efficiency and better fault-tolerance capability are required for the EVs. Flux-switching permanent magnet (FSPM) motor attracts an increasingly attention because of its features over conventional rotor-PM motors.]. Although AFFSPM motors offer higher torque density, the torque density is restricted owing to decreased available winding space because in addition to the armature windings, the PMs are placed in the stator. Hence flux switching machines with sandwiched permanent magnet were suggested .

Propagation of radio occultation (RO) signals through the lower troposphere results in high phase acceleration and low signal to noise ratio signal. The excess Doppler estimation accuracy in lower troposphere is very important in receiving RO signals which can be estimated by sliding window spectral analysis. To do this, various frequency estimation methods such as MUSIC and ESPRIT can be adopted. Due to the cost and bandwidth constraints, reducing the sampling rate at GNSS receivers of LEO satellite is necessary which causes aliasing. A method of resolving frequency ambiguities is the simultaneous sampling of signal by multiple sample frequencies (MSF). Accordingly, we study the capacity of MSF method to improve the spectral efficiency and use accurate frequency estimation schemes to enhance the excess Doppler estimation accuracy of RO signal in post-processing. Via simulation results, the accuracy of excess Doppler estimation in post-processing based on both single sample frequency (SSF) and MSF methods for different frequency estimation methods are compared. Simulation results reveal that the MSF method has better performance than that of the SSF method. Besides, it is shown that Jacobsen and Jacobsen with Bias methods almost have the same performance and their estimation error is less than that of other methods. By exploiting the proposed scheme, the frequency estimation error is significantly decreased and it is negligible compared to the traditional methods. Moreover, by using this scheme, we have 41.6%

In this paper, the speed tracking for permanent magnet synchronous motor (PMSM) in field oriented control (FOC) method is investigated using linear proportional-integral (PI) controller, sliding mode controller (SMC) and its advanced counterparts. The advanced SMCs considered in this paper are fuzzy SMC (FSMC) and sliding mode controller with time-varying switching gain (SMC+TG) which can effectively cope with chattering, an inherent harmful phenomenon in SMC. Regardless of all the works done to replace PI controller with SMC and its advanced counterparts, a thorough comparison of the PMSM drive behavior under mentioned controllers is still missing. This paper attempts to fill in this gap, by providing a fair and in-depth comparison of the PMSM drive operation by using PI and sliding mode speed controllers. In this paper, in order to design and provide a fair framework for comparison the performance and robustness of these four controllers a suitable cost function is defined to manage the performance effectively. Thus, based on this cost function a nonlinear optimization problem is defined. To solve the optimization problem and consequently derive the optimal values for the parameters of the controllers, particle swarm optimization (PSO) and grey wolf optimization (GWO) algorithms are employed. The performance and robustness of the PMSM drive using four optimal controllers are studied in the presence of different conditions and uncertainties. Numerical results demonstrate that SMC and its advanced counterparts cannot offer the superior behavior for all conditions and their superiority is less than it is often stated in the literature.

Probabilistic data structures are so popular in membership queries, network applications, and so on. Bloom Filter and Cuckoo Filter are two popular space efficient models that incorporate in set membership checking part of many important protocols. They are compact representation of data that use hash functions to randomize a set of items. Being able to store more elements while keeping a reasonable false positive probability is a key factor of design. A new algorithm is proposed to improve some of the performance properties of Cuckoo Filter such as false positive rate and insertion performance and solve some drawbacks of the Cuckoo algorithm such as endless loop. Main characteristic of the Bloom Filter is used to improve Cuckoo Filter, so we have a smart Cuckoo Filter which is modified by Bloom Filter (SCFMBF). SCFMBF uses the same table of buckets as Cuckoo Filter but instead of storing constant Fingerprints, It stores Bloom Filters. Bloom Filters can be accumulated in the table’s buckets which leads to higher insertion feasibility. We also address the endless loop problem of Cuckoo Filter that means an inserted item is stuck in an iterative process of finding an empty bucket, so a smart algorithm is designed which not only solves endless loop problems but also prevents insertion failure. our algorithm prevents double checking of a bucket and avoids making loops. Consequently the capacity of SCFMBF is improved significantly. Results of comparison with Cuckoo Filter shows that false positive probability of SCFMBF method is four times enhanced.

Transmit waveform design is one of the most important problems in active sensing and communication systems. This problem, due to the complexity and non-convexity, has been always the main topic of many papers for the decades. However, still an optimal solution which guarantees a global minimum for this multi-variable optimization problem is not found. In this paper, we propose an attracting methodology to design transmit waveform of active sensing and communication systems with good auto-correlation properties. To this end, we tackle the non-convexoptimization problem of Integrated Sidelobe Level (ISL) minimization with the unimodular constraint. Using the epigraph and Second Order Cone Programming (SOCP) approach, thein-hand non-convex optimization will resort to a Semi-Definite Programming (SDP). Then, we use Majorization-Minimization to deal with constraints and convert the obtained problem to aconvex optimization problem. Finally, the obtained optimization problem is tackled using CVX toolbox. To obtain the code vectors from the extracted optimal code matrix, we use rank-onedecomposition. The simulation and results indicate the powerfulness of the proposed algorithm in designing radar transmit sequences with unimodular constraint. We show the proposed algorithm can design long length sequences with a very small ISL values. The proposed framework further can be investigated for the future optimization problems, like Peak Sidelobe Level (PSL) minimization.

Improper designs of the demand response programs can lead to numerous problems such as customer dissatisfaction and lower participation in these programs. In this paper, a home energy management system is designed which schedules appliances of smart homes based on the user’s specific behavior to address these issues. Two types of demand response programs are proposed for each house which are shifting-based and learning-based programs for shiftable and heating, ventilation and cooling appliances, respectively. The current structure uses machine learning techniques to design the best demand response programs for heating, ventilation and cooling devices of each user based on his/her behavior and desired comfort level. Doing so, the home energy management system is able to achieve energy cost and consumption reduction without causing dissatisfaction and discomfort to the users. Results demonstrate that by using this structure, energy cost and consumption are reduced by 20.32% and 27%, respectively for a single house located in the Austin, Texas area, in one day. The proposed home energy management structure is tested on three additional houses to show the effectiveness of it. Moreover, comparisons with other methods are performed to clarify the benefits of this structure over other methods. The proposed structure is formulated as a mixed-integer linear model with its optimization performed in the General Algebraic Modeling System environment. CPLEX solver is used to solve the optimization problem.

Differential global surface impedance (DGSI) model, a rigorous approach, has been applied to the analysis of three dimensional plasmonic circuits. This model gives a global relation between the tangential electric field and the equivalent surface electric current on the boundary of an object. This approach helps one bring the unknowns to the boundary surface of an object and so avoid volumetric discretization. It also eliminates the need for equivalent surface magnetic current consideration. Therefore, there is no need to evaluate the rather complex integral operator related to this current. This will result in a great reduction in computation time and memory resources. On the other hand, due to small field variations along the longitudinal direction of each boundary segment, it is suggested to use the two dimensional DGSI matrix in the analysis of a three dimensional plasmonic circuit. This leads to a much simpler formulation of the DGSI model. Besides, our numerical results verify that this simplifying assumption will not greatly affect the accuracy of the analysis. Plasmonic waveguides with different thicknesses along with a line coupler have been analyzed. The results are verified with the results of a commercial software as well as global surface impedance (GSI) model previously presented in the literature.

The work presented in this paper discusses time delay compensation of a rigid spacecraft with faulty actuators. The proposed method consists of a nominal controller and an extended state observer. Based on the backstepping method, the nominal control is designed to stabilize the spacecraft in the presence of delayed inputs. Then, the discrepancy between the nominal plant and real system which is influenced by faulty actuators, model uncertainties, and external disturbances is estimated by the extended state observer and actively compensated. The proposed controller does not require exact knowledge of delay, actuator faults and disturbances. By adjusting controller parameters, using the Lyapunov-Krasovski method and properties of modified Rodrigues parameters, it is proved that the investigated control scheme can stabilize the system with respect to a small neighborhood of the origin. Numerical simulation results demonstrate that the acceptable performance of the controlled system is guaranteed in the presence of retreated inputs, the considered faults are tolerated and disturbances are rejected.