Nihat Öztürk

Application of Genetic Algorithms to Core Loss Coefficient Extraction

Core loss data are usually provided in the form of tables or curves of total loss versus flux density or frequency for electrical machine designers. These tables or curves can be used to extract the loss coefficients of the core loss formulas because accurate calculations of the coefficients have an important issue in electrical machine design. In this study, using original loss data given for M19 steel material, the core loss coefficients are calculated by the genetic algorithm developed in Matlab environment and electromagnetic analysis software (Ansoft Maxwell) is also used to extract the core loss coefficients in order to verify the proposed method. It is found that the exponent of flux density (B) depends on the flux range or the frequency range and these changes in the exponent of B can be correlated to the physical phenomenon of domain wall movement in response to an external field. As a difference from existing studies in literature, this study suggests a new method for extracting the core loss coefficients without any requirement for mathematical operations due to the nature of genetic algorithms and over the range of frequencies between 50–400 Hz and flux densities from 0 to 1.5 T, the new method yields lower errors for the specific core losses than those obtained by the magnetic field analysis software.

A Novel Control Technique for Soft-switching Sinusoidal Pulse Width Modulation Inverter

Abstract This article presents a new zero-current switching technique for a single-phase full-bridge sinusoidal pulse width modulation inverter. Two auxiliary switches and a resonant branch are attached to a conventional single-phase full-bridge inverter. The resonant branch can be controlled independently from the main power switches. This technique decreases turn-on and turn-off switching losses and does not require any snubber capacitor. The technique can be applied to DC/DC converters and DC/AC inverters with suitable switching algorithms. Both theoretical analysis and application of the proposed technique have been realized. It was seen that the proposed technique has 45% less switching losses and better performance than the hard-switching technique for the same load and switching frequency. The experimental results also approve the effectiveness of the zero-switching technique.

An Educational Tool for the Genetic Algorithm-Based Fuzzy Logic Controller of a Permanent Magnet Synchronous Motor Drive

In this study, a novel educational tool is introduced for the genetic algorithm (GA)-based fuzzy logic controller (FLC) of a permanent magnet synchronous motor (PMSM) drive. This tool provides the operating principle of PMSM, essentials of GAs, and effects of FLC parameters on the performance of GA-based FLC. The proposed educational tool regarding GA-based FLC is a unique one in its field in the literature, as such a computer-based study aiming to teach the corresponding intelligent system has not been studied before, though both GA and FLC are well-known powerful techniques. The graphical interface, developed in Microsoft Visual C#. NET platform, has a flexible and functional structure. By changing motor operating conditions as well as GA and controller parameters, useful practices can be done on the whole system under various situations without wasting time. An evaluation of the tool is given based on student feedback.

Microprocessor based voice recognition system realization

Voice recognition systems, which today is one of gradually started to gain importance. In this study, using a PIC18F452 microcontroller, two registered words, compared with a voice command input. Registered with the sound of the word overlap as a result of the exit sign is active. Recognition of the audio signals zero crossing for the count and time was examined. In general, the voice recognition process, sound recording and determination of the expression; processing of sound, making comparison and integration of rest; finally, the expression was created with the realization of the corresponding functions. Developed in this system, without sounds recording of audio signal processing are performed simultaneously. In this system, not a waste of time for this situation may be many advantages to the system. Work is relatively simple and economically cheap.

Implementation of a call system with power line communication

In this study, a communication system to send an eight-bits data to the receiver via an energy transmission (power) line was designed and tested. On the transmitter three buttons were used to send three different data to the line. On the receiver side, a buzzer and an LCD screen were used for the voice warning and for indication of the button which a call is activated. There is no need of additional inter-line between the transmitters and receivers. By using this setup, one preserves much time, labor and cost. The prototype of the developed setup was successfully operated in a flat.

Investigation of switching losses for sinusoidal PWM zero current switching inverter and resonant link inverter

In this study, simulations of two methods used for minimizing the switching losses occur in DC/AC inverters with PWM that is used extensively because of its high power density, fast response and control facility were carried out. First method which can be applied easily is the resonant link inverter. The other one is the resonant transition zero current switching inverter, which employs two auxiliary switches and LC resonance tank to assist switching transitions. In the study, sinusoidal PWM was used for gate signal. Switching signals are generally produced in consequence of comparing the carrier and reference signals. These inverters do not require any modification on conventional sinusoidal PWM scheme. Both inverters were simulated based on ORCADs actual device models. They were operated under the same conditions and the switching losses were analyzed. The results obtained show that the efficiency of the inverter with zero current transition method is considerably higher.

Implementation of indirect vector control to induction motor with zero current transition inverter

In this study, the speed control of the vector controlled induction motor was implemented by using hard switching and soft switching inverters. A TMS320F243 digital signal processor was used to implement control algorithm during practical implementation. With the use of the vector control, complex structure of the controller is simplified, and dependence to variations of the motor parameters is reduced. In order to reduce switching losses arising mainly from hard switching method a soft switching method was designed and implemented. Switching signals of the auxiliary switches are independent from main switching signals in the proposed method. The method can be applied to the puls width modulation (PWM) inverter by setting up proper switching strategies.

A hybrid symbiotic organisms search and simulated annealing technique applied to efficient design of PID controller for automatic voltage regulator

This article is motivated by incorporating a hybrid symbiotic organisms search and simulated annealing (hSOS-SA) technique into efficient design of PID controller for automatic voltage regulator (AVR). Symbiotic organism search (SOS) algorithm is contemplated first to optimize parameters of PID controller using a new cost function which considers both time-domain and frequency-domain specifications. The excellence of SOS over some state-of-the-art techniques is confirmed through transient response analysis, root locus analysis and bode analysis for the identical AVR system. To fine-tune controller parameters for enhancing the system stability margin further, simulated annealing algorithm is invoked subsequently at the instant SOS has converged. Extensive numerical results computed from time and frequency response specifications affirm the superiority of proposed hSOS-SA algorithm such that after a minimal overshoot, hSOS-SA tuned AVR system settles to the step reference quickly and follows it with the least steady-state error. Such response is found to ensure a better stability margin than that using original SOS and earlier studies. Finally, robustness analysis is realized to verify that the designed controller is robust with regard to parameter uncertainties.

CuZn30 sac malzemenin kesme işlemlerinde kesme boşluğu etkilerinin sinir ağı ile modellenmesi - karşılaştırmalı bir çalışma

Clearance effects on the product quality and blanking force in sheet metal blanking process are initially investigated experimentally, and then modelled through neural network (NN) approach. Using eleven different clearances from 8% to 18% with a sampling rate of 1%, blanking processes are applied to sheet material CuZn30 with a thickness of 1mm using a modular template. During the experiments, blanking force, smooth sheared/fractured rate and burr height for the resulting products are measured for each of clearance value and a certain portion of them are taken as example patterns to train the developed feedforward NN. Several NN-based estimation results are presented which verify that a satisfactory neural network model is attained for the concerned parameter estimations. Moreover, comparisons with a recent study that benefits from fuzzy logic as an estimator tool are also presented for the same system. We realize that estimating performance is improved using the NN and a significant contribution of our proposal is that its design is much simpler than that of its counterpart which requires proper and sufficient expert knowledge for tuning of characteristic parameters such as numbers and shapes of membership functions, linguistic control rules.

A new fuzzy logic estimator for reduction of commutation current pulsation in brushless DC motor drives with three-phase excitation

Under the operation of brushless DC motor with three-phase excitation, commutation current pulsation is produced at each commutation at high-speed region. As it can be eliminated when the current slew rates are made equal, a simple and effective fuzzy logic estimator (FLE) is presented first time in the literature to reduce such current pulsation. Its function is to simply regulate the commutation angle accurately to maintain the same current slew rates of commutated phases during commutation, thereby keeping the other phase current unchanged. Unlike previous studies, the presented method does not require torque observer or detection circuits for sensing commutation interval, in addition to commutation time calculation. A genetic algorithm is employed for optimal definition of the FLE’s rule base. The presented method is tested by the accurate simulation, and it is proved that the proposed method is quite capable of reducing the commutation current pulsation and improving the motor output power.