Recent Advances in Electrical & Electronic Engineering - Volume 13, Issue 5, 2020

For autonomous navigation, tracking and obstacle avoidance, a mobile robot must have the knowledge of its position and localization over time. Among the available techniques for odometry, vision-based odometry is robust and economical technique. In addition, a combination of position estimation from odometry with interpretations of the surroundings using a mobile camera is effective. This paper presents an overview of current visual odometry approaches, applications, and challenges in mobile robots. The study offers a comparative analysis of different available techniques and algorithms associated with it, emphasizing on its efficiency and other feature extraction capability, applications and optimality of various techniques.

Model Predictive Control (MPC) in the field of power electronics has recently gained a lot of interest in the research community. Even though the computations are very complex in MPC algorithm, the availability of powerful processors has helped this approach to acquire a notable place in the area of control. They can take into account the nonlinearities and constraints very precisely. Having these advantages, they are found to be very attractive for controlling power converters and drives. This paper presents the review of growth and applications of MPC applied to power converters and drives. Some of the key elements like prediction model and its discretization, cost function, weighing factor and optimization algorithm are highlighted in this paper.

Background: Advanced Metering Infrastructure (AMI) for the smart grid is growing rapidly which results in the exponential growth of data collected and transmitted in the device. By clustering this data, it can give the electricity company a better understanding of the personalized and differentiated needs of the user. Objective: The existing clustering algorithms for processing data generally have some problems, such as insufficient data utilization, high computational complexity and low accuracy of behavior recognition. Methods: In order to improve the clustering accuracy, this paper proposes a new clustering method based on the electrical behavior of the user. Starting with the analysis of user load characteristics, the user electricity data samples were constructed. The daily load characteristic curve was extracted through improved extreme learning machine clustering algorithm and effective index criteria. Moreover, clustering analysis was carried out for different users from industrial areas, commercial areas and residential areas. The improved extreme learning machine algorithm, also called Unsupervised Extreme Learning Machine (US-ELM), is an extension and improvement of the original Extreme Learning Machine (ELM), which realizes the unsupervised clustering task on the basis of the original ELM. Results: Four different data sets have been experimented and compared with other commonly used clustering algorithms by MATLAB programming. The experimental results show that the US-ELM algorithm has higher accuracy in processing power data. Conclusion: The unsupervised ELM algorithm can greatly reduce the time consumption and improve the effectiveness of clustering.

Background: Operational Transconductance Amplifier (OTA) plays an essential role in many analog and mixed-signal applications that encourages the researchers to contribute their work to design suitable structures of OTA for their applications with acceptable performance parameters. Methods: The linearity of an OTA is one of its key performance parameters, which affects the performance of the overall system whereas the transconductance value of OTA (Gm) contributes to decide its application area. Low transconductance OTA finds its application in biomedical and neural networks while OTA with higher transconductance is suitable for wireless communication. In any system, it is desirable to obtain a linear voltage-to-current conversion, i.e., OTA, hence various linearization techniques have been reported to linearize the OTA. Results: In the last two decades, various OTA structures have been reported with linear voltage-tocurrent conversion. Some researchers used attenuation by means of different circuit approaches to linearize the OTA or some used cancellation of nonlinearity terms by using different circuit implementation techniques. Researchers used some other methods also to linearize the OTA viz source degeneration, square root technique and mobility compensation. Conclusion: The purpose of this paper is to provide a brief survey of various popular linearization techniques reported in the past.

Background: Semi-supervised learning in the machine learning community has received widespread attention. Semi-supervised learning can use a small number of tagged samples and a large number of untagged samples for efficient learning. Methods: In 2014, Kim proposed a new semi-supervised learning method: the minimax label propagation (MMLP) method. This method reduces time complexity to O (n), with a smaller computation cost and stronger classification ability than traditional methods. However, classification results are not accurate in large-scale image classifications. Thus, in this paper, we propose a semisupervised image classification method, which is an MMLP-based algorithm. The main idea is threefold: (1) Improving connectivity of image pixels by pixel sampling to reduce the image size, at the same time, reduce the diversity of image characteristics; (2) Using a recall feature to improve the MMLP algorithm; (3) through classification mapping, gaining the classification of the original data from the classification of the data reduction. Results: In the end, our algorithm also gains a minimax path from untagged samples to tagged samples. The experimental results proved that this algorithm is applicable to semi-supervised learning on small-size and that it can also gain better classification results for large-size image at the same time. Conclusion: In our paper, considering the connectivity of the neighboring matrix and the diversity of the characteristics, we used meanshift clustering algorithm, next we will use fuzzy energy clustering on our algorithm. We will study the function of these paths.

Background: The original filter including grounded or virtual ground capacitors can be synthesized by using the NAM expansion. However, so far the filters including floating capacitor, such as Sallen-Key filter, have not been synthesized by means of the NAM expansion. This is a problem to be researched further. Methods: By using the adjoint network theory, the Sallen-Key filter including floating capacitor first is turned into a current-mode one, which includes a grounded capacitor and a virtual ground capacitor. Then the node admittance matrix, after derived, is extended by using NAM expansion. Results: At last, one VDTA Sallen-Key filter is received. It employs single compact VDTA and two grounded capacitors. Conclusion: A Butterworth VDTA second-order frequency filter based on Sallen-Key topology with fo = 100kHz, HLP = -HBP=1, is designed.

Background: In this paper, an ultra-wide-band bandpass filter with large stopband using interdigital coupled lines and pair of Square Complimentary Split Ring Resonator (SCSRR) is proposed. Methods: Interdigital coupled lines give bandpass characteristics and pair of SCSRR provides tuning of cut off frequencies and transmission zeroes on both side of the passband. In the passband, two transmission poles are achieved. The tightly coupled structure provides a wide stopband and sharp skirt response. Results: Dielectric constant 2.6 and its thickness of 0.787 mm is used to implement the design. Centre frequency of the proposed design is 5.1 GHz. Bandwidth at -3 dB is 3.5 GHz to 6.5 GHz. Conclusion: The proposed structure is simulated in Ansoft HFSS.

Background: As wireless energy transmission technology advances, the demand for energy directional transmission increases. Objective: Transfer of energy in the specified direction and increase in transmission power. Methods: A novel three-coil transmitting structure was proposed, which can transmit energy to a specified single or multiple space regions, and enhance the magnetic field strength in a single direction by magnetic field vector synthesis to improve the transmission power. Results: Combined with Mathcad numerical calculation and Maxwell simulation analysis, the experimental platform was built and the magnetic focusi of the proposed novel structure was experimentally verified. Conclusion: The novel emission structure can effectively perform directional energy transmission and increase the transmission power by 2~3 times in a single direction at the cost of 10%~15% efficiency loss.

Background: A novel fault location method of HVDC transmission line based on a concentric relaxation principle is proposed in this paper. Methods: Due to the different position of fault, the instantaneous energy measured from rectifier and inverter are different, and the ratio k between them is the relationship to the fault location d. Through the analysis of amplitude-frequency characteristics, we found that the wave attenuation characteristic of low frequency in the traveling wave is stable, and the amplitude of energy is larger, so we get the instantaneous energy ratio by using the low-frequency data. By using the method of wavelet packet decomposition, the voltage traveling wave signal was decomposed. Results: Finally, calculate the value k. By using the data fitting, the relative function of k and d can be got, that is the fault location function. Conclusion: After an exhaustive evaluation process considering different fault locations, fault resistances, and noise on the unipolar DC transmission system, four-machine two-area AC/DC parallel system, and an actual complex grid, the method presented here showed a very accurate and robust behavior.

Background: Few results about the controller of linear discrete-time system with control delay are reported. Methods: By means of the multi-step transformation with memory, the linear discrete-time systems with additional control delay can be transformed to the equivalent linear discrete-time systems without control delay, and the dimension of the transformed system is not increased. By designing the optimal controller of the finite horizon optimal controller of linear discrete time systems without time delay, the controller of linear discrete time systems with additional control delay can be obtained. At the same time, by designing the optimal controller of the infinite horizon optimal controller of linear discrete time systems without time delay, the controller of linear discrete time systems with additional control delay can be obtained as well. Results: The corresponding finite horizon optimal controller has proved to render the closed-loop system exponentially stable. And the corresponding infinite horizon optimal controller has proved to render the closed-loop system exponentially stable when the open-loop system is either controllable or stabilizable. Finally, two examples are used to verify the theoretical results of this paper. Conclusion: The controller design and the exponentially stability of discrete-time linear system with additional state delay will be investigated in the future.

Background: Doubly-Fed Induction Generator (DFIG) is a dual input conventional asynchronous device connected across both stator and rotor, which also functions as an electrical transducer consuming up-to 30 % of the generated power during the rotor injection. This is the major concern with respect to the DFIG in terms of effective power generation. Methods: The proposed work provides the solution for this undesirable power loss by connecting the DFIG with an array of solar Photovoltaic (PV) panel through a conventional direct current bus using a boost converter. This research setup can work on the basis of indirect vector control algorithms applied at the rotor and grid converter level in order to maintain the constant DC voltage under arbitrary conditions. Results: Even the variations in voltage and frequency will be controlled with this novel approach. A simulation model of the 300KW solar PV array and a 2MW DFIG system is developed using MATLAB/Simulink environment. Conclusion: Solar and wind energy sources incorporate Maximum Power Point Tracking (MPPT) through their control algorithms resulting in the add on 30-80 KW of solar power for rotor injection compared to the existing system in order to reduce the power rating of the converters and power consumption from the grid.

Background: Oceanographic buoys generally employ satellites for positioning and data transmission. However, sea surface conditions can affect these signals. The Signal to Noise Ratio (SNR) of small observation buoys can be improved by exploiting polarization diversity. Methods: This paper discusses the effect of sea surface conditions on the polarization and reflection loss of Beidou B1 reflected signals for the purposes of exploiting polarization diversity. The Rayleigh roughness criterion is used to assess the roughness of the sea surface. The Fresnel reflection coefficients are derived to analyze the polarization and reflection loss of the Beidou B1 reflected signals with different sea surface states. Results: The results obtained show that for the Beidou B1 signals, the sea surface is considered rough for most sea surface states and incident angles. For smooth sea surfaces, the Beidou B1 reflected signals are mainly Left Hand Circularly Polarized (LHCP) waves, but Right Hand Circularly Polarized (RHCP) waves dominate when the incident angles are larger than the Brewster angle. The reflected loss is between -2 dB to -3.4 dB. In rough sea surfaces and the signals propagation is dominated by diffuse reflection. The reflection loss decreases with the incident angle and there is a fluctuation when the incident angle is around 49 degrees. The specular reflection signal has a significant amplitude when the angle of incidence is large. RHCP waves are the main component of the reflected signals, and the reflection loss is relatively small which can be employed for polarization diversity or marine remote sensing. Conclusion: polarization diversity is only useful with good sea conditions, and the corresponding gain decreases with the deterioration of the sea surface conditions.

Background: The permanent magnet synchronous linear motor is a strongly coupled, nonlinear system. It has been applied in many fields, especially in the field of machining lathes and rail transportation. In order to ensure the permanent magnet synchronous linear motor has good dynamic performance and robustness, sliding mode control is gradually applied to the control system of permanent magnet synchronous linear motor. However, in the traditional sliding mode control, the convergence speed is slow, and the robust performance is poor when the sliding surface is not reached. Objective: The main purpose of this paper is to improve the dynamic performance and robustness of the permanent magnet synchronous linear motor during the process of approaching the sliding surface. Methods: Firstly, the type of nonlinear curve with "small error reduction, large error saturation" is introduced to design a nonlinear integral speed controller with global robustness. Secondly, the gain rate time-varying reaching law is introduced to reduce "chattering". Finally, using a symbolic tangent function instead of a sign function in designing a sliding mode observer reduces fluctuations in load observations. Results: Finally, the correctness and effectiveness of the control method are proved by simulation. Conclusion: The results of the simulation show that the nonlinear integral sliding mode controller based on gain time-varying reaching law is shown to have good global robustness and dynamic performance.

Background: A centrifugal vane pump driven by a three-phase AC motor is a key component for modern equipment. Therefore, its condition directly affects the operating and safety performance of the system. Modeling and simulation are effective methods for the system analysis. Methods: A mathematical model of a Tank-to-Engine Fuel Feed System (T-EFFS) is designed based on its phased-mission behavior and structure redundancy. Both of the damage modes that arise frequently in a given type of system are tracked: the fuel feed pump seal damage due to fatigue and the vane damage due to corrosion. Then, a multiple degradation T-EFFS model is established to simulate the fuel pressure at the system outlet under different damage modes. The morphological spectrum decrement index is used to describe the damage of the system. Results: The results show that the T-EFFS model can describe the phased-mission behavior of the system and meet the requirement of the fuel flow rate for the entire mission profile. Then, the decrease in the fuel pressure of the T-EFFS with the cumulative effects of vane damage and crack growth under different behavior modes is simulated along its life span. Conclusion: This work aims to provide a model and data support for a subsequent investigation. The results can be used to fit the health background curve of the system, predict the performance degradation trend of the system at given life points, and further evaluate its remaining service life.

Background: Power converters used in nanosatellite application required to be more tolerant to radiations including proton, electron and heavy-ion radiation. Methods: A Single-Ended Primary Inductance Converter (SEPIC) is selected for the nanosatellite application because of the availability to step up and down the input voltage as well as having a non-inverting polarity between the input and output voltage. In this paper, remodeled SEPIC converter proposed with an improved performance at radiation environment to work for nanosatellite application. In addition, the analysis is carried out for the irradiated power MOSFET in SEPIC converter to check its impact on converter behavior. Results: Experiments conducted with the help of power MOSFET switch used in converter, irradiated with Cobalt60 gamma ray dose level from 50krad to 300krad and output characteristics analyzed by chancing the duty cycle of converter. Investigations shown that conventional converter output characteristics were virtually constant from 10% to 60% duty cycle when different radiated MOSFETs used in the converter. Conclusion: The electrical characteristics started to fluctuate at 60% duty cycle and onwards, while the remodeled converter circuit was less distorted when increasing the radiation dose.