http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/421 2026-04-07T01:55:32Z http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/4722 DEVELOPMENT AND STUDY OF THE CHARACTERISTICS AND STABILITY OF A MICROPROCESSOR BASED FEEDBACK CONTROL SYSTEM FOR A THREE PHASE INDUCTION MOTOR A microprocessor based three phase induction motor speed control system is designed and developed. The rated value of the motor is 1390 revolution per minute(rpm) 50 Hz. But by the use of present control system the motor speed can be varied from 500 rpm to 2000 rpm at the rated torque. A six step three phase inverter is designed to drive the motor. To avoid commutation failure in a wide frequency range n-channel MOS FET is used place of SCR. One way digital delay circuit is designed to avoid high voltage dc short circuit situation due to the FET's turn off delay. A computer interface card is designed to read the speed of the motor and to write (set) the required voltage level either in digitat to analogue(D/A) converter or in Demultiplexer to set the appropriate voltage which drive the VCO for generating required motor driving frequency. This frequency is then fed in logic circuit to generate device triggering pulses for three phase inverter. A number of programs in C++ is written to perform the activities between the computer and the interfacing card. In the screen of the computer we can see several aspects of the running motor such as speed, slip, torque and deviation of all these values from the rated values. 382875 A mechanical section is developed to apply some load to the motor. Several characteristics of the motor is observed in different loaded condition and presented in a graphical form. This experimental graphs are compared with the theoretical ones. And last the performance of the present work is evaluated and proposal is made for further development of the present motor control system. This thesis is submitted for the degree of Master of Philosophy. 2025-09-07T00:00:00Z http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/4710 Simulation, Design and Development of an Artificial Neural System (ANS) for Spatio-temporal Pattern Recognition An artificial neural system has been designed and developed for spatio-temporal pattern recognition. Bi-directional Associative Memory (BAM), Adaptive Resonance Theory (ART), Kohonen bit map and Fuzzy System have been utilized to develop the system. The system is gain controlled. Several approaches have been made to learn temporal and spatio- temporal patterns in the framework of Neural Network. ANS are advantageous in dealing with low-level high resolution of signal processing. Feed forward network for learning static patterns has been adapted. In designing the network and to process the information through it, both time-domain and frequency domain nature of spatio-temporal patterns has been considered and analyzed. Software has been developed to realize the system utilizing programming C++. Considering a variety of inputs, the system has been simulated, tested and finally outputs have been obtained. It has been found that the system exhibits the capacity to recognize & display more than one pattern at a time. Input vectors and weight matrix have been determined, which performed the convergence & similarity between the two patterns. A three-layer fully interconnected in feed forward neural network has been presented in this dissertation to recognize the patterns of Bangla alphabet, English alphabet, sound recognition, frequency measurement, any special pattern input, the territory map of Bangladesh, numerals, four geometric figures, pictures, any special symbol and spatio- temporal pattern for recognition. It has been realized that the neural network approach with BAM, ART utilizing Kohonen feature map and Fuzzy System have better in parallel patterns as compared to other methods. The system has been developed to recognize any pattern of any specific consideration This thesis is submitted for the degree of Master of Philosophy. 2025-09-01T00:00:00Z http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/3897 Design and performance studies of photovoltaic hybrid power systems for remote area in Bangladesh Rahman, Md. Mostafizur This thesis is submitted for the degree of Master of Philosophy. 2025-03-11T00:00:00Z http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/3895 Preparation of selective surfaces and study of their optical properties Alam Khan, Md. Anwar This thesis is submitted for the degree of Master of Philosophy. 2025-03-11T00:00:00Z