Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 40418

Electrical and Computer Engineering

Speech Recognition System for a Voice Controlled Robot with Real Time Obstacle Detection and Avoidance
Speech Recognition is a technology which allows the processing of a speech input to text and is speaker independent. This allows it to be used in numerous applications ranging from digital assistants to controlling machinery. This paper proposes a strategy which can be used in controlling a robotic vehicle through connected speech input. The speech recognizer platform will be an Android smartphone which communicates with the robot using Bluetooth Connectivity. This method allows for efficient recognition and smooth data transfer. Additionally the robot will also have the capability to detect obstacles and inform the user to use a different command. Our proposed technique will be useful for applications such as assistive robots for people with disabilities or in industrial applications such as work robots.
Net Zero Energy Home including Photovoltaic Solar Cells, Wind Turbines, Battery Energy Storage Systems and Hydrogen Internal Combustion Engine Vehicles
This paper addresses a net zero energy home that utilizes renewable energy resources (i.e., photovoltaic solar cells and small-scale wind turbines) as well as battery energy storage systems (BESS). In the introduced system, the generated power by renewable energy resources is used to supply the energy of home, and BESS is applied for energy time-of-use arbitrage. As well, the extra amount of energy is utilized for electrolysis of water into breathable oxygen and hydrogen gas as fuel of hydrogen vehicles. The proposed problem is mathematically expressed as mixed integer nonlinear programming (MINLP) and solved using particle swarm optimization (PSO) technique. Objective function of the problem is to minimize number of charging-discharging cycles resulting in increasing life-cycle of BESS. The proposed optimization problem also finds the optimal capacity and power for BESS. Simulation results demonstrate that the proposed technique can successfully manage net zero energy home and optimally utilizes renewable energy resources, BESS, and hydrogen vehicles at the same time.
Optimal Continuous Scheduled Time for a Cumulative Damage System with Age-Dependent Imperfect Maintenance
Many manufacturing systems suffer failures due to complex degradation processes and various environment conditions such as random shocks. Consider an operating system is subject to random shocks and works at random times for successive jobs. When successive jobs often result in production losses and performance deterioration, it would be better to do maintenance or replacement at a planned time. A preventive replacement (PR) policy is presented to replace the system before a failure occurs at a continuous time T. In such a policy, the failure characteristics of the system are designed as follows. Each job would cause a random amount of additive damage to the system, and the system fails when the cumulative damage has exceeded a failure threshold. Suppose that the deteriorating system suffers one of the two types of shocks with age-dependent probabilities: type-I (minor) shock is rectified by a minimal repair, or type-II (catastrophic) shock causes the system to fail. A corrective replacement (CR) is performed immediately when the system fails. In summary, a generalized maintenance model to scheduling replacement plan for an operating system is presented below. PR is carried out at time T, whereas CR is carried out when any type-II shock occurs and the total damage exceeded a failure level. The main objective is to determine the optimal continuous schedule time of preventive replacement through minimizing the mean cost rate function. The existence and uniqueness of optimal replacement policy are derived analytically. It can be seen that the present model is a generalization of the previous models, and the policy with preventive replacement outperforms the one without preventive replacement.
Electric Vehicle Market Penetration Impact on Greenhouse Gas Emissions for Policy-making: A United Arab Emirates Case Study
The United Arab Emirates is clearly facing a multitude of challenges in curbing its greenhouse gas emissions to meet its pre-allotted framework of Kyoto protocol and COP21 targets due to its hunger for modernization, industrialization, infrastructure growth, soaring population and oil and gas activity. In this work, we focus on the bonafide zero emission electric vehicles market penetration in the country’s transport industry for emission reduction. We study the global electric vehicle market trends, the complementary battery technologies and the trends by manufacturers, emission standards across borders and prioritized advancements which will ultimately dictate the terms of future conditions for the United Arab Emirate transport industry. Based on our findings and analysis at every stage of current viability and state-of-transport-affairs, we postulate policy recommendations to local governmental entities from a supply and demand perspective covering aspects of technology, infrastructure requirements, change in power dynamics, end user incentives program, market regulators behavior and communications amongst key stakeholders.
Optimal Sequential Scheduling of Imperfect Maintenance Last Policy for a System Subject to Shocks
Maintenance has a great impact on the capacity of production and on the quality of the products, and therefore, it deserves continuous improvement. Maintenance procedure done before a failure is called preventive maintenance (PM). Sequential PM, which specifies that a system should be maintained at a sequence of intervals with unequal lengths, is one of the commonly used PM policies. This article proposes a generalized sequential PM policy for a system subject to shocks with imperfect maintenance and random working time. The shocks arrive according to a non-homogeneous Poisson process (NHPP) with varied intensity function in each maintenance interval. As a shock occurs, the system suffers two types of failures with number-dependent probabilities: type-I (minor) failure, which is rectified by a minimal repair, and type-II (catastrophic) failure, which is removed by a corrective maintenance (CM). The imperfect maintenance is carried out to improve the system failure characteristic due to the altered shock process. The sequential preventive maintenance-last (PML) policy is defined as that the system is maintained before any CM occurs at a planned time Ti or at the completion of a working time in the i-th maintenance interval, whichever occurs last. At the N-th maintenance, the system is replaced rather than maintained. This article first takes up the sequential PML policy with random working time and imperfect maintenance in reliability engineering. The optimal preventive maintenance schedule that minimizes the mean cost rate of a replacement cycle is derived analytically and determined in terms of its existence and uniqueness. The proposed models provide a general framework for analyzing the maintenance policies in reliability theory.
Effect of Wavelengths Impedance Spectroscopy of a Vertical Parallel Junction Silicon Solar Cell under Monochromatic Illumination
In this paper, we present a theoretical study effect of a wavelengths impedance spectroscopy of a vertical parallel junction silicon solar cell under monochromatic illumination. By solving the excess minority carrier density expression, the photocurrent and the photovoltage were established. We plotted Bode and Nyquist diagram of the silicon solar cell impedance and gave corresponding electrical circuits. Then we introduced impedance spectroscopy method to some electrical parameters of vertical parallel junction silicon solar cell such as the series resistance Rₛ and parallel resistance Rₚ.
Review of Mathematical Modelling for Frequency and Damping Ratio of Phugoid Mode of an Aircraft
In aircraft dynamics, when an aircraft is disturbed from its equilibrium flight conditions, it goes into different modes of vibration. An aircraft needs to counter these modes in order to come back to its equilibrium flight conditions. Phugoid mode is one of the modes of vibration of aircraft along longitudinal axis. For the phugoid mode, the motion of aircraft is variation in air speed and altitude, with no variation in angle-of-attack. To counter vibration modes, an aircraft must be damped. The expressions for frequency and damping ratio for the phugoid mode had to be derived in order to find the parameters on which frequency and damping ratio depend so that these parameters are adjusted during flight or in aircraft design to counter these modes. By use of linearized system of equations of motion, after applying small disturbance theory, with certain assumptions and applying eigen values analysis, relevant differential equations were solved, and the expressions for both frequency and damping ratio of phugoid mode were obtained. The resulting expressions showed the dependence of frequency and damping ratio of phugoid motion on certain parameters which came out to be velocity and lift to drag ratio of an aircraft. The results obtained showed the dependence of frequency on velocity of aircraft, so, velocity can be adjusted during flight to minimize frequency. Damping ratio was found dependent on lift to drag ratio of an aircraft which needs to be adjusted accordingly during aircraft design.
Online Battery Equivalent Circuit Model Estimation on Continuous-Time Domain Using Linear Integral Filter Method
Equivalent circuit models (ECMs) are widely used in battery management systems in electric vehicles and other battery energy storage systems. The battery dynamics and the model parameters vary under different working conditions, such as different temperature and state of charge (SOC) levels, and therefore online parameter identification can improve the modelling accuracy. This paper presents a novel way of online ECM parameter identification using a continuous time (CT) estimation method. The CT estimation method has several advantages over discrete time (DT) estimation methods for ECM parameter identification due to the widely separated battery dynamic modes and fast sampling. The proposed method can be used for online SOC estimation. Test data are collected using a lithium ion cell, and the experimental results show that the proposed CT method achieves better modelling accuracy compared with the conventional DT recursive least square method. The effectiveness of the proposed method for online SOC estimation is also verified on test data.
Black-Box-Optimization Approach for High Precision Multi-Axes Forward-Feed Design
A method for optimal selection of components for multi-axes forward-feed drive systems is proposed in which the choice of motors, gear boxes and ball screw drives is optimized. Essential is here the synchronization of electrical and mechanical frequency behavior of all axes because even advanced controls (like H∞-controls) can only control a small part of the mechanical modes – namely only those of observable and controllable states whose value can be derived from the positions of extern linear length measurement systems and/or rotary encoders on the motor or gear box shafts. Further problems are the unknown processing forces like cutting forces in machine tools during normal operation which make the estimation and control via an observer even more difficult. To start with, the open source Modelica Feed Drive Library which was developed at the Laboratory for Machine Tools, and Production Engineering (WZL) is extended from one axis design to the multi axes design. It is capable of simulating the mechanical, electrical and thermal behavior of permanent magnet synchronous machines with inverters, different gear boxes and ball screw drives in a mechanical system. To keep the calculation time down analytical equations are used for field and torque producing equivalent circuit, heat dissipation and mechanical torque at the shaft. As a first step, a small machine tool with a working area of 635 x 315 x 420 mm is taken apart, and the mechanical transfer behavior is measured with an impulse hammer and acceleration sensors. With the frequency transfer functions, a mechanical finite element model is built up which is reduced with substructure coupling to a mass-damper system which models the most important modes of the axes. The model is modelled with Modelica Feed Drive Library and validated by further relative measurements between machine table and spindle holder with a piezo actor and acceleration sensors. In a next step, the choice of possible components in motor catalogs is limited by derived analytical formulas which are based on well-known metrics to gain effective power and torque of the components. The simulation in Modelica is run with different permanent magnet synchronous motors, gear boxes and ball screw drives from different suppliers. To speed up the optimization different black-box optimization methods (Surrogate-based, gradient-based and evolutionary) are tested on the case. The objective that was chosen is to minimize the integral of the deviations if a step is given on the position controls of the different axes. Small values are good measures for a high dynamic axes. In each iteration (evaluation of one set of components) the control variables are adjusted automatically to have an overshoot less than 1%. It is obtained that the order of the components in optimization problem has a deep impact on the speed of the black-box optimization. An approach to do efficient black-box optimization for multi-axes design is presented in the last part.
Behavior of Epoxy Insulator with Surface Defect under HVDC Stress
HVDC technology is becoming increasingly popular due to its simplicity in topology and less power loss over long distance of power transmission, in comparison with HVAC technology. However, the dielectric behavior of insulators in the long term under HVDC stress is completely different from that under HVAC stress as a result of charge accumulation in a constant electric field. Insulators used in practical systems are never perfect in their structural conditions. Over time shallow cracks may develop on their surface. The presence of defects can lead to drastic change in their dielectric behaviour and thus increase the probability of surface flashover. In this contribution, experimental investigations have been carried out on the charge accumulation phenomenon on the surface of a rod insulator made of epoxy that is placed between two disk shaped electrodes at different voltage levels and in different gases (SF6, CO2 and N2). Many results obtained, such as, the two-dimensional electrostatic potential distribution along the insulator surface after the removal of the power source following a pre-defined period of application. The probe has been carefully calibrated before each test. Results show that surface charge distribution near the two disk shaped electrodes is not uniform in the circumferential direction, possibly due to the imperfect electrical connections between the embeded conductor in the insulator and the disk shaped electrodes. The axial length of this non-uniform region is experimentally determined, which provides useful information for shielding design. A charge transport model is also used to explain the formation of the long term electrostatic potential distribution under a constant applied voltage.
Buck Boost Inverter to Improve the Efficiency and Performance of E-Motor by Reducing the Influence of Voltage Sag of Battery on the Performance of E-Motor
This paper researches the impact of battery voltage sag on the performance and efficiency of E-motor in electric cars. Terminal voltage of battery reduces with the S.o.C. This results in the downward shift of torque-speed curve of E-motor and increased copper losses in E-motor. By introducing a buck-boost inverter between the battery and E-motor, an additional degree of freedom was achieved. By boosting the AC voltage, the dependency of voltage sag on the performance of E-motor was eliminated. A strategy was also proposed for the operation of the buck-boost inverter to minimize copper and iron losses in E-motor to maximize efficiency. MATLAB-SIMULINK model of E-drive was used to obtain simulation results. The temperature rise in the E-motor was reduced by 14% for a 10% increase in AC voltage. From the results, it was observed that a 20% increase in AC voltage can result in improvement of running torque and maximum torque of E-motor by 44%. Hence it was concluded that using a buck-boost inverter for E-drive significantly improves both performance and efficiency of E-motor.
Impact of Series Reactive Compensation on Increasing a Distribution Network Distributed Generation Hosting Capacity
The distributed generation hosting capacity of a distribution network is typically limited at a given connection point by the upper voltage limit that can be violated due to the injection of active power into the distribution network. The upper voltage limit violation concern becomes more important as the network equivalent resistance increases with respect to its equivalent reactance. This paper investigates the impact of modifying the distribution network equivalent reactance at the point of connection such that the upper voltage limit is violated at a higher distributed generation penetration, than it would without the addition of series reactive compensation. The results show that series reactive compensation proves efficient in certain situations (based on the ratio of equivalent network reactance to equivalent network resistance at the point of connection). As opposed to the conventional case of capacitive compensation of a distribution network to reduce voltage drop, inductive compensation is seen to be more appropriate for alleviation of distributed-generation-induced voltage rise.
Optimal Planning and Design of Hybrid Energy System for Taxila University
Renewable energy resources are being realized as suitable options in hybrid energy planning for on-grid and micro grid. In this paper, operation, planning and optimal design of on-grid distributed energy resources based hybrid system are investigated. The aim is to minimize the cost of the overall energy system keeping in view the environmental emission and minimum penetration of conventional energy resources. Seven grid connected different case studies including diesel only, diesel-renewable based, and renewable based only are designed to perform economic analysis, operational planning and emission. Sensitivity analysis is implemented to investigate the impact of different parameters on the performance of energy resources.
Estimation of the Temperatures in Asynchronous Machines Using Extended Kalman Filter
In order to monitor the thermal behavior of an asynchronous machine with squirrel cage rotor, a 9th-order extended Kalman filter (EKF) algorithm is implemented to estimate the temperatures of the stator windings, the rotor cage, and the stator core. The state-space equations of EKF are established based on the electrical, mechanical and the simplified thermal models of the asynchronous machine. The asynchronous machine with simplified thermal model in Dymola are compiled as the physical model (a S-Function) in MATLAB/SIMULINK. The coolant air temperature, three-phase voltages and currents are exported from the physical model and processed by EKF estimator as the inputs. Compared to the temperatures exported from the physical model of the machine, three parts of temperatures can be estimated quite accurately by the EKF estimator. The accuracy of each temperature is up to 98%. The online EKF estimator is independent from the machine control algorithm and can work under any speed and load condition if the stator current is nonzero current system.
Volume Density of Power of Multivector Electric Motor
Since the invention, the electrical machine (EM) can be defined as oEM – one-vector electrical machine, as it works due to one-vector inductive coupling with use of one-vector electromagnet. The disadvantages of oEM are large size and limited efficiency at low and medium power applications. This paper describes multi-vector electrical machine (mEM) based on multi-vector inductive coupling, which is characterized by the increased surface area of the inductive coupling per EM volume, with a reduced share of inefficient and energy-consuming part of the winding, in comparison with oEM’s. Particularly, it is considered, calculated and compared the performance of three different electrical motors and their power at the same motor volumes and rotor frequencies. It is also presented the result of calculation of correlation between power density and volume for oEM and mEM motors. The method of multi-vector inductive coupling enables mEM motors to possess 1.5–4.0 greater density of power per volume and significantly higher efficiency, in comparison with today’s oEM motors, especially in low and medium power applications. mEM motors have distinct advantages, when used in transport vehicles such as electric cars and aircrafts.
Protection of Floating Roof Petroleum Storage Tanks against Lightning Strokes
The subject of petroleum storage tank fires has gained a great deal of attention due to the high cost of petroleum, and the consequent disruption of petroleum production; therefore, much of the current research has focused on petroleum storage tank fires. Also, the number of petroleum tank fires is oscillating between 15 and 20 fires per year. About 33% of all tank fires are attributed to lightning. Floating roof tanks (FRT’s) are especially vulnerable to lightning. To minimize the likelihood of a fire, the API RP 545 recommends three major modifications to floating roof tanks. This paper was inspired by a stroke of lightning that ignited a fire in a crude oil storage tank belonging to an Egyptian oil company, and is aimed at providing an efficient lightning protection system to the tank under study, in order to avoid the occurrence of such phenomena in the future and also, to give valuable recommendations to be applied to floating roof tank projects.
Estimation of Respiratory Parameters in Pressure Controlled Ventilation System with Double Lungs on Secretion Clearance
A new mechanical ventilator with automatic secretion clearance function can improve the secretion clearance safely and efficiently. However, in recent modeling studies on various mechanical ventilators, it was considered that human had one lung, and the coupling effect of double lungs was never illustrated. In this paper, to expound the coupling effect of double lungs, a mathematical model of a ventilation system of a bi-level positive airway pressure (BiPAP) controlled ventilator with secretion clearance was set up. Moreover, an experimental study about the mechanical ventilation system of double lungs on BiPAP ventilator was conducted to verify the mathematical model. Finally, the coupling effect of double lungs of the mathematical ventilation was studied by simulation and orthogonal experimental design. This paper adds to previous studies and can be referred to optimization methods in medical researches.
Detection of Defects in Carbon Fiber Reinforced Polymer by Ultrasonic Infrared Thermographic Method
In the paper introduced the diagnostic technique making possible the research of internal structures in composite materials reinforced fibres using more in different applications. The main reason of damages in structures of these materials is the changing distribution of load in constructions in the lifetime. Appearing defect is largely complicated because of the appearance of disturbing of continuity of reinforced fibres, binder cracks and loss of fibres adhesiveness from binders. A defect in composite materials is usually more complicated than in metals. At the present moment, non-destructive diagnostics with method of IR thermography is applied more. One of IR thermography methods used in non-destructive evaluation is vibrothermography. The vibrothermography is not a new non-destructive method, but the new solution is to use ultrasonic waves to thermal stimulation of materials. In this paper, both modelling and experimental results which illustrate the advantages and limitations of ultrasonic IR thermography in inspecting composite materials will be presented. The ThermoSon computer program developed at Tomsk Polytechnic University, Russia, was used to optimise heating parameters in the detection of subsurface defects in composite materials. The program allows for the analysis of transient heat conduction and ultrasonic wave propagation phenomena in solids. The experiments at MIAT were fulfilled by means of FLIR SC 7600 IR camera. A continuous ultrasonic stimulation was performed with a piezoelectric unit at the frequency from 15 kHz to 30 kHz with maximum power up to 2 kW.
Development of an Evaluation Metric on the Basis of a Comprehensive Proband Study in Order to Benchmark Conventional an Electrified Vehicle Concepts in Terms of Customer-Oriented Driving Dynamics
Automobile manufacturers progressively focus on a downsizing strategy to meet the EU's CO2 requirements concerning type-approval consumption cycles. The reduction in naturally aspirated engine power is compensated by increased levels of turbocharging. By downsizing conventional engines, CO2 emissions are reduced. However, it also implicates major challenges regarding longitudinal dynamic characteristics. An example of this circumstance is the delayed turbocharger-induced torque reaction which leads to a partially poor response behavior of the vehicle during acceleration operations. That is why it is important to focus conventional drive train design on real customer driving again. The currently considered dynamic maneuvers like the acceleration time 0-100 km/h discussed by journals and car manufacturers describe longitudinal dynamics experienced by a driver inadequately. For that reason we present the realization and evaluation of a comprehensive proband study. Subjects are provided with different vehicle concepts (electrified vehicles, vehicles with naturally aspired engines and vehicles with different concepts of turbochargers etc.) in order to find out which dynamic criteria are decisive for a subjectively strong acceleration and response behavior of a vehicle. Subsequently, realistic acceleration criteria are derived. By weighing the criteria an evaluation metric is developed to objectify customer-oriented transient dynamics. Fully-electrified vehicles are the benchmark in terms of customer-oriented longitudinal dynamics. The electric machine provides the desired torque almost without delay. This advantage compared to combustion engines is especially noticeable at low engine speeds. In conclusion, we will show the degree to which extent customer-relevant longitudinal dynamics of conventional vehicles can be approximated to electrified vehicle concepts. Therefore, various technical measures (turbocharger concepts, 48V electrical chargers etc.) and drive train designs (e.g. varying the final drive) are presented and evaluated in order to strengthen the vehicle’s customer-relevant transient dynamics. As a rating size the newly developed evaluation metric will be used.
Advanced Stability Criterion for Time-Delayed Systems of Neutral Type and Its Application
This paper investigates stability problem for linear systems of neutral type with time-varying delay. By constructing various Lyapunov-Krasovskii functional, and utilizing some mathematical techniques, the sufficient stability conditions for the systems are established in terms of linear matrix inequalities (LMIs), which can be easily solved by various effective optimization algorithms. Finally, some illustrative examples are given to show the effectiveness of the proposed criterion.
Accurate Position Electromagnetic Sensor Using Data Acquisition System
In this paper, we present a new high position electromagnetic sensor system (HPESS) that is applicable as moving object detection. We have developed a high-performance position sensor prototype dedicated to students’ laboratory. The challenge was to obtain a highly accurate and real-time sensor that is able to calculate the position, length or displacement. An electromagnetic solution based on a two coil induction principal was adopted. HPESS convert mechanical motion to electric energy with direct contact. The output signal can be fed electronic circuit. The voltage output change from sensor is captured by data acquisition system using Labview software. The displacement of the moving object is determined. The measured data are transmitted to a Pc in real time via a DAQ (NI USB -6281). This paper describes also the data acquisition analysis developed specially for sensor signal monitoring and used with car electronic of conditioning. The Data is then recorded and viewed using a user interface written using National Instrument LabVIEW software. On-line displays of time and voltage of the sensor signal provide a user-friendly data acquisition interface .The sensor provides an uncomplicated, accurate, reliable, inexpensive transducer for highly sophisticated control systems.
Study of Transformer and Motor Winding under Pulsed Power Application
Pulsed Power in the form of Recurrent Surge Generator (RSG) can be used for testing various parameters of Motor or Transformer windings including inter-turn, interlayer insulation. Windings with solid insulation in motor and transformer have many interfaces and undesirable defects, and these defects can be exposed under this nondestructive testing methodology. Due to rapid development in power electronics variable frequency drives (VFD), Dry Type or cast resin Transformer used with PWM Sine wave inverters for solar power, solid insulation system used nowadays are shifting more and more to a high-frequency application. Authors have used the recurrent surge generator for testing winding integrity as well as Partial Discharge(PD) at fast rising voltage enabling PD measurement at closer situation under which the insulation system is supposed to work. Authors have discussed test results on a different system with recurrent surge voltages of different rise time.
PSS®E Based Modelling, Simulation and Synchronous Interconnection of Eastern Grid and North-Eastern Regional Grid of India
Eastern Regional(ER) Grid and North Eastern Regional (NER) Grid are two major grids of Eastern Part of India. Both of the grid consists of voltage level 765kV, 400 kV, 220 kV and numerous buses at lower voltage range. Eastern Regional Grid and North Eastern Regional Grid are not only connected among themselves but are also connected to various other grids of India. ER and NER Grid having various HVDC lines or back to back systems which form the total network. The studied system comprises of 340 buses of different voltage levels and transmission lines running over a length of 32089 km. The validation of load flow has been done using IEEE STANDARD 30 bus system. The power flow simulation analysis has been performed after synchronizing both the Eastern Grid and North-Eastern Regional Grid of India using Power System Simulators for Engineering (PSS®E) Important inferences has been drawn from the study.
Cable Diameter Effect on the Contact Temperature of Power Automotive Connector
In the electric vehicle, high power leads to high current; automotive power connector should resist to this high current in order to avoid a serious damage caused by the increase of contact temperature. The purpose of this paper is to analyze experimentally and numerically the effect of the cable diameter variation on the decrease of contact temperature. For this reason, a finite element model was developed to calculate the numerical contact temperature for several cable diameters and several electrical high currents. Also, experimental tests were established in order to validate this numerical model. Results show that the influence of cable diameter on the contact temperature is never neglected.
Modeling and Simulation of the Tripod Gait of a Hexapod Robot
Hexapod legged robot’s missions, particularly in irregular and dangerous areas, require high stability and high precision. In this paper, we consider the rectangular architecture body of legged robots with six legs distributed symmetrically along two sides; each leg contains three degrees of freedom for greater mobility. The aim of this work is planning tripod gait trajectory, based on the computing of the kinematic model to determine the joint variables in the lifting and the propelling phases. For this, an appropriate coordinate frames are attached to the body and legs in order to obtain clear representation and efficient generation of the system equations. A simulation in Matlab software platform is developed to confirm the kinematic model and various trajectories to the tripod gait adopted by the hexapod robot in its locomotion.
Effects of Magnetization Patterns on Characteristics of Permanent Magnet Linear Synchronous Generator for Wave Energy Converter Applications
The rare earth magnets used in synchronous generators offer many advantages, including high efficiency, greatly reduced the size, and weight. The permanent magnet linear synchronous generator (PMLSG) allows for direct drive without the need for a mechanical device. Therefore, the PMLSG is well suited to translational applications, such as wave energy converters and free piston energy converters. This manuscript compares the effects of different magnetization patterns on the characteristics of double-sided PMLSGs in slotless stator structures. The Halbach array has a higher flux density in air-gap than the Vertical array, and the advantages of its performance and efficiency are widely known. To verify the advantage of Halbach array, we apply a finite element method (FEM) and analytical method. In general, a FEM and an analytical method are used in the electromagnetic analysis for determining model characteristics, and the FEM is preferable to magnetic field analysis. However, the FEM is often slow and inflexible. On the other hand, the analytical method requires little time and produces accurate analysis of the magnetic field. Therefore, the flux density in air-gap and the Back-EMF can be obtained by FEM. In addition, the results from the analytical method correspond well with the FEM results. The model of the Halbach array reveals less copper loss than the model of the Vertical array, because of the Halbach array’s high output power density. The model of the Vertical array is lower core loss than the model of Halbach array, because of the lower flux density in air-gap. Therefore, the current density in the Vertical model is higher for identical power output. The completed manuscript will include the magnetic field characteristics and structural features of both models, comparing various results, and specific comparative analysis will be presented for the determination of the best model for application in a wave energy converting system.
Thermal Image Segmentation Method for Stratification of Freezing Temperatures
The study uses an image analysis technique employing thermal imaging to measure the percentage of areas with various temperatures on a freezing surface. An image segmentation method using threshold values is applied to a sequence of image recording the freezing process. The phenomenon is transient and temperatures vary fast to reach the freezing point and complete the freezing process. Freezing salt water is subjected to the salt rejection that makes the freezing point dynamic and dependent on the salinity at the phase interface. For a specific area of freezing, nucleation starts from one side and end to another side, which causes a dynamic and transient temperature in that area. Thermal cameras are able to reveal a difference in temperature due to their sensitivity to infrared radiance. Using Experimental setup, a video is recorded by a thermal camera to monitor radiance and temperatures during the freezing process. Image processing techniques are applied to all frames to detect and classify temperatures on the surface. Image processing segmentation method is used to find contours with same temperatures on the icing surface. Each segment is obtained using the temperature range appeared in the image and correspond pixel values in the image. Using the contours extracted from image and camera parameters, stratified areas with different temperatures are calculated. To observe temperature contours on the icing surface using the thermal camera, the salt water sample is dropped on a cold surface with the temperature of -20°C. A thermal video is recorded for 2 minutes to observe the temperature field. Examining the results obtained by the method and the experimental observations verifies the accuracy and applicability of the method.
Analysis of Silicon Controlled Rectifier-Based Electrostatic Discharge Protection Circuits with Electrical Characteristics for the 5V Power Clamp
This paper analyzed the SCR (Silicon Controlled Rectifier)-based ESD (Electrostatic Discharge) protection circuits with the turn-on time characteristics. The structures are the LVTSCR (Low Voltage Triggered SCR), the ZTSCR (Zener Triggered SCR) and the PTSCR (P-Substrate Triggered SCR). The three structures are for the 5V power clamp. In general, the structures with the low trigger voltage structure can have the fast turn-on characteristics than other structures. All the ESD protection circuits have the low trigger voltage by using the N+ bridge region of LVTSCR, by using the zener diode structure of ZTSCR, by increasing the trigger current of PTSCR. The simulation for the comparison with the turn-on time was conducted by the Synopsys TCAD simulator. As the simulation results, the LVTSCR has the turn-on time of 2.8 ns, ZTSCR of 2.1 ns and the PTSCR of 2.4 ns. The HBM simulation results, however, show that the PTSCR is the more robust structure of 430K in HBM 8kV standard than 450K of LVTSCR and 495K of ZTSCR. Therefore the PTSCR is the most effective ESD protection circuit for the 5V power clamp.
Indoor Temperature Estimation with FIR Filter Using R-C Network Model
In this paper, we proposed a new strategy for estimating indoor temperature based on the modified resistance capacitance (R–C) network thermal dynamic model. Using minimum variance finite impulse response (FIR) filter, accurate indoor temperature estimation can be achieved. Our study is clarified by the experimental validation of the proposed indoor temperature estimation method. This experiment scenario environment is composed of a demand response (DR) server and home energy management system (HEMS) in a test bed.
Designing an Intelligent Voltage Instability System in Power Distribution Systems in the Philippines Using IEEE 14 Bus Test System
The state of an electric power system may be classified as either stable or unstable. The borderline of stability is at any condition for which a slight change in an unfavourable direction of any pertinent quantity will cause instability. Voltage instability in power distribution systems could lead to voltage collapse and thus power blackouts. The researchers will present an intelligent system using back propagation algorithm that can detect voltage instability and output voltage of a power distribution and classify it as stable or unstable. The researchers’ work is the use of parameters involved in voltage instability as input parameters to the neural network for training and testing purposes that can provide faster detection and monitoring of the power distribution system.