Theses supervised by Prof. Dr. Şerafettin Erel
14 theses · Ankara Yıldırım Beyazıt University
Computer simulation and experimental implementation of single phase power inverters regarding output waveforms
Recent rises in electrical energy costs have done alternative energy options more attractive. A device such as solar panel is able to convert photons from the sun into the DC (Direct Current) electric which can be used by the end users. However, there is a problem by using this kind of energy. Our electric grid and most of the house appliances are based on the AC (Alternating Current) electric so the energy achieved by the sun or wind power needs to be converted from DC to AC to be useful. This converting process is done by an electronic device called inverter. Inverters can be found in a wide area of power electronics in the industry. The produced output voltage and frequency at the AC side of an inverter depend on the circuit structure, transformers and applied components. In this thesis, comparative analysis of single phase power inverters regarding their output waveforms was performed. Square wave, modified square wave and true sine wave inverter circuits were designed and analyzed using Proteus Professional package program. This comparison was fulfilled with respect to the circuit configuration, THD (Total Harmonic Distortion) and output efficiency. After simulation results these inverter circuits were realized on PCB (Printed Circuit Board) circuits. Efficiency of the inverters was calculated using Extech true RMS digital multimeter and THD values were measured by means of the Fluke 435 Power Analyzer device. According to the simulation and experimental results, the analyzed square wave inverter circuit has about 55% THD and 45% efficiency due to the circuit structure. The analyzed modified square wave inverter circuit has about 38% THD and 60% efficiency better than square wave inverter. The analyzed true sine wave inverter circuit having with about 10% THD and an efficiency of 75% has the most ideal output signal among the inverter types. Tests on resistive and inductive loads were carried out under laboratory conditions and output signals were observed with the help of Tektronix digital storage oscilloscope. Test results and simulation outcomes were confirmed to each other. It was found out that true sine wave inverter circuit is better and more efficient in many aspects compared to the modified and square wave inverter circuits in spite of their complicated structures and higher costs.
Investigation and optimization of some tactical data link technologies
Tactical Data Link Systems (TDLSs) provide a tactical information exchange between air, ground and naval units near real time in the battlefield area. Combat platforms have many different TDL capabilities such as Link-11, Link-16, Link-22, VMF and JREAP. Every TDL has different characteristics. The main problem is to decide which TDL is more effective in terms of transmission of data to another platform. In this thesis, a detailed literature survey about TDL systems has been carried out. This knowledge is presented in Chapter 1. The optimization theory is briefly mentioned in Chapter 2. In Chapter 3, an optimization is made with regard to the transmission of data in the operational area. And finally, the conclusion is presented in Chapter 4. Key Words: Tactical Data Links (TDLs), Link-11, Link-16, Link-22, Variable Message Format (VMF), Joint Range Extension Application Protocol (JREAP), Optimization of TDL.
Design and development of a novel photovoltaic system with reflectors and a sun tracker
In this thesis study, as a new method, design and development of a double surface photovoltaic system with reflection property was aimed. In the direction of this purpose, the thesis study was completed within three stages as design, development, and performance measurements. The double surface panel system was designed completely as the first stage of the thesis study. A single axis sun tracking system, a reflector system for the back panel, two solar panels placed back to back, and suitable platforms were planned. In the development stage, two opto-electronically controlled reflectors with the ability to rotate around their own axes were used to illuminate the back solar panel. Thus, the system was optimized in the way that equal amount of light fluxes irradiates the front and back panels. The system was supported by the optoelectronic based single axis sun tracker to increase working performance. Measurements of the developed system were done in laboratory settings and on open field as real time. The results showed that the back solar panel produces sufficient amount of electricity and the system works under proper angular conditions. It is concluded that the system developed as a prototype might be used in industrial applications.
Development of an electrodynamic cooling system and simulator to improve the performance of a double faced photovoltaic system
Photovoltaic cooling is a way to improve electrical performance of photovoltaics against thermal effects. Based on this purpose, the thesis study is developed with three subsystems: Solar simulator system, dynamic control system and double faced photovoltaic system. Solar simulator system has two identical light sources, two identical photovoltaic panels back to back, cooler and heater. By activating heater, thermal effect on electrical performance of double faced system is observed. By activating cooler, cooling effect on electrical performance of double faced photovoltaic system is observed. Dynamic control system has two temperature sensors those are inside the solar simulator and outside the solar simulator. Based on temperature difference between temperature sensors, cooling mechanism is activated electrodynamically. Temperature measurement is done in a real-time manner. Double faced photovoltaic system is designed to improve electrical performance of photovoltaic systems. It is placed inside the solar simulator system to improve the output power. It is concluded that designed solar simulator system eases the observation of thermal and cooling effect on electrical performance of photovoltaic systems. Thanks to its time-independent and weather-independent operation, it is possible to conduct experiments in every day time, every month and every weather.
Comparison of landing control algorithms for vertical landing rockets in simulation environment
This study aims to comprehensively compare the performance of different landing algorithms developed for vertical landing rockets in a simulation environment. Vertical landing rockets are of great importance in space missions and other aerospace applications. The successful landing of these rockets depends on the efficiency and accuracy of the control algorithms used. The performance of the landing algorithms plays a critical role, especially in the transition from high speeds to low speeds and in the final stages of the landing. The study addresses four main control methods that affect this performance: PID control, DDPG control, and MPC control approaches. Each algorithm was subjected to various test conditions in different landing scenarios and evaluated in terms of key parameters such as accuracy, fuel efficiency, landing speed, and stability. The simulation results have identified the strengths and limitations of each algorithm, providing in-depth analyses of which algorithm performs better under specific conditions. These analyses provide significant insights for the future development of rocket landing algorithms. In particular, it has been determined which algorithm is more efficient under certain environmental conditions and which types of missions it offers ideal performance for. The findings of the study aim to contribute to making rocket technology safer, more efficient, and more cost-effective, serving as a resource for the development of landing systems for future vertical landing rockets.
Real-time multi-object recognition using the fusion of lidar and camera data
Object recognition is currently one of the most significant research topics. Its significance is expected to steadily increase due to its extensive applications across various fields, from agriculture to defense and the space industry. In this study, real-time object recognition processes were conducted within a user-defined area using data simultaneously captured from the built-in camera of the iPhone 13 Pro Max and its integrated LIDAR sensor. The Swift programming language was employed, and SwiftUI was chosen as the framework. The study utilized elements from the MS COCO dataset, employing the YOLO V5 algorithm for object recognition. Real-time video processing was accomplished using Swift Metal. The YOLO V5 algorithm was utilized for object recognition, and video processing was carried out in real-time, narrowing down the area based on the minimum-maximum distance determined in the interface using the real-time fused data from the camera and LIDAR. Areas outside the contours of objects, defined by user-specified value ranges in each frame of the captured real-time video data, were darkened. Thus, the object recognition process was performed on objects within each darkened frame. As a result, object recognition was successfully conducted within a user-defined range of 0-15 meters, as configured in the interface.
Fabrication and characterization of dye-sensitized solar cells based on hybrid photoanodes consisting of Zr-doped ZnO nanorods and TiO2 nanoparticles
Owing to its bandgap, surface structure, particle size, porosity, and film thickness, TiO2 is a popular photoelectrode in DSSCs. However, the electron mobility of TiO2 is too low to improve the photovoltaic performance of DSSCs further. As a result, much research on DSSCs has concentrated on improving electron transport with various semiconductor materials. Among all these semiconductor materials, ZnO has gotten the most interest because of its similar band gap to TiO2, greater electron mobility, easier tailoring, and easier surface modification than TiO2. As a result, it can be used as a working electrode in DSSCs with or without TiO2. One dimensional nanostructures have a lesser surface area for dye adsorption, and a hybrid film composed of ZnO nanorods (NRs) and TiO2 nanoparticles (NPs) is particularly effective in terms of surface area, light absorption, and charge transport. To further improve electron transport characteristics of ZnO NRs, in this study, they were doped with Zr (0.5, 1, 1.5, 2 and 2.5 wt.%). The current study used a hydrothermal technique to create DSSCs based on undoped and Zr-doped ZnO NRs/TiO2 NPs. XRD, SEM, EDS, and UV-Vis methods were used to characterize the samples. Furthermore, the photovoltaic performance of the devices used as the photoanode in DSSCs was measured. A power conversion efficiency of 3.31%, 4.91% and 8.33% was obtained for the devices assembled with conventional photoanodes of only TiO2 NPs, undoped ZnO NRs/TiO2 NPs and Zr-doped ZnO NRs/TiO2 NPs (at 2 wt.% of Zr), respectively. The results strongly suggest that Zr-doped ZnO NRs/TiO2 NPs-based photoanodes achieve a complementary effect in DSSC devices and consequently can be extended to similar applications.
Computer simulation and experimental implementation of single phase power inverters regarding output waveforms
Recent rises in electrical energy costs have done alternative energy options more attractive. A device such as solar panel is able to convert photons from the sun into the DC (Direct Current) electric which can be used by the end users. However, there is a problem by using this kind of energy. Our electric grid and most of the house appliances are based on the AC (Alternating Current) electric so the energy achieved by the sun or wind power needs to be converted from DC to AC to be useful. This converting process is done by an electronic device called inverter. Inverters can be found in a wide area of power electronics in the industry. The produced output voltage and frequency at the AC side of an inverter depend on the circuit structure, transformers and applied components. In this thesis, comparative analysis of single phase power inverters regarding their output waveforms was performed. Square wave, modified square wave and true sine wave inverter circuits were designed and analyzed using Proteus Professional package program. This comparison was fulfilled with respect to the circuit configuration, THD (Total Harmonic Distortion) and output efficiency. After simulation results these inverter circuits were realized on PCB (Printed Circuit Board) circuits. Efficiency of the inverters was calculated using Extech true RMS digital multimeter and THD values were measured by means of the Fluke 435 Power Analyzer device. According to the simulation and experimental results, the analyzed square wave inverter circuit has about 55% THD and 45% efficiency due to the circuit structure. The analyzed modified square wave inverter circuit has about 38% THD and 60% efficiency better than square wave inverter. The analyzed true sine wave inverter circuit having with about 10% THD and an efficiency of 75% has the most ideal output signal among the inverter types. Tests on resistive and inductive loads were carried out under laboratory conditions and output signals were observed with the help of Tektronix digital storage oscilloscope. Test results and simulation outcomes were confirmed to each other. It was found out that true sine wave inverter circuit is better and more efficient in many aspects compared to the modified and square wave inverter circuits in spite of their complicated structures and higher costs.
The modeling and simulation of intersatellite laser communication systems
Free Space Optical (FSO) Communication Systems are alternatives to Radio Frequency (RF) communication systems due to the high data rate, high bandwidth capacity, smaller size, and weight, less power consumption, high security, resistance to interference etc. There are many manufactured satellites orbiting around the earth and RF technique, which is a conventional communication method for satellite systems, is used in order for them to communicate with each other. It is possible to send several Gbps data to thousands kilometers distances with laser communication. This is done by means of adopting optical wireless communication technology into space technology; hence, intersatellite optical wireless communication is developed. In this thesis, detailed literature survey about free space optical communication system has been done. The importance of laser systems for free-space communication has been discussed and the status of laser techniques for intersatellite communication has been examined. The functions of the each basic component such as laser source, photodetector, modulation type, telescope used in a typical system have been examined. The intersatellite link has been modeled and simulated by means of Optiwave Software for the various link configurations and the system performance (BER/Q-Factor) has also been analyzed in terms of each basic parameter such as transmitted power, wavelength, data rate, range and telescope diameter in order to achieve minimum BER. APD type and PIN type photodetector comparison has been performed. Moreover, Erbium Doped Fiber Amplifier (EDFA) has been used for the intersatellite link to recognize its effect on the link quality. It has been shown that communication performance of the system can be improved by choosing the most appropriate component in terms of communication requirements. Key Words: Intersatellite Laser Communication, Free Space Optical Communication, Optical Wireless Channel, Bit Error Rate, Q Factor.
The modeling and simulation of intersatellite laser communication systems
Free Space Optical (FSO) Communication Systems are alternatives to Radio Frequency (RF) communication systems due to the high data rate, high bandwidth capacity, smaller size, and weight, less power consumption, high security, resistance to interference etc. There are many manufactured satellites orbiting around the earth and RF technique, which is a conventional communication method for satellite systems, is used in order for them to communicate with each other. It is possible to send several Gbps data to thousands kilometers distances with laser communication. This is done by means of adopting optical wireless communication technology into space technology; hence, intersatellite optical wireless communication is developed. In this thesis, detailed literature survey about free space optical communication system has been done. The importance of laser systems for free-space communication has been discussed and the status of laser techniques for intersatellite communication has been examined. The functions of the each basic component such as laser source, photodetector, modulation type, telescope used in a typical system have been examined. The intersatellite link has been modeled and simulated by means of Optiwave Software for the various link configurations and the system performance (BER/Q-Factor) has also been analyzed in terms of each basic parameter such as transmitted power, wavelength, data rate, range and telescope diameter in order to achieve minimum BER. APD type and PIN type photodetector comparison has been performed. Moreover, Erbium Doped Fiber Amplifier (EDFA) has been used for the intersatellite link to recognize its effect on the link quality. It has been shown that communication performance of the system can be improved by choosing the most appropriate component in terms of communication requirements. Key Words: Intersatellite Laser Communication, Free Space Optical Communication, Optical Wireless Channel, Bit Error Rate, Q Factor.
The modeling and simulation of intersatellite laser communication systems
Free Space Optical (FSO) Communication Systems are alternatives to Radio Frequency (RF) communication systems due to the high data rate, high bandwidth capacity, smaller size, and weight, less power consumption, high security, resistance to interference etc. There are many manufactured satellites orbiting around the earth and RF technique, which is a conventional communication method for satellite systems, is used in order for them to communicate with each other. It is possible to send several Gbps data to thousands kilometers distances with laser communication. This is done by means of adopting optical wireless communication technology into space technology; hence, intersatellite optical wireless communication is developed. In this thesis, detailed literature survey about free space optical communication system has been done. The importance of laser systems for free-space communication has been discussed and the status of laser techniques for intersatellite communication has been examined. The functions of the each basic component such as laser source, photodetector, modulation type, telescope used in a typical system have been examined. The intersatellite link has been modeled and simulated by means of Optiwave Software for the various link configurations and the system performance (BER/Q-Factor) has also been analyzed in terms of each basic parameter such as transmitted power, wavelength, data rate, range and telescope diameter in order to achieve minimum BER. APD type and PIN type photodetector comparison has been performed. Moreover, Erbium Doped Fiber Amplifier (EDFA) has been used for the intersatellite link to recognize its effect on the link quality. It has been shown that communication performance of the system can be improved by choosing the most appropriate component in terms of communication requirements. Key Words: Intersatellite Laser Communication, Free Space Optical Communication, Optical Wireless Channel, Bit Error Rate, Q Factor.
The integrated and operational impact of loyal wingman aircraft in modern air forces
The concept of Manned and Unmanned Teaming is paramount in the evolution of contemporary warfare, with the integration of legacy manned air forces and Loyal Wingman systems representing a noteworthy transformation. This operational structure enhances the efficacy of piloted aircraft while concomitantly mitigating operational risks and bolstering mission success rates. Loyal Wingman systems, characterized as unmanned aerial vehicles, serve a supportive role alongside piloted aircraft, functioning collaboratively. These systems are designed to possess lower radar cross-sections, thereby enhancing the stealth of aerial operations and increasing the safety of manned platforms during reconnaissance and strike missions. For instance, a Loyal Wingman can be tasked with the detection and neutralization of enemy air defense systems, enabling piloted aircraft to execute bombing or strike missions with reduced exposure to enemy fire. A thorough analysis of operational scenarios underscores the efficacy of Manned and Unmanned Teaming applications in minimizing aircraft attrition. Such scenarios elucidate the critical functions performed by the sensor and weapon systems integrated into Loyal Wingman vehicles, which effectively contribute to safeguarding piloted aircraft. Specifically, these systems are capable of conducting precursor missions, facilitating target identification, and determining enemy positions, allowing pilots to engage targets from safer distances. In conclusion, an air force augmented by Loyal Wingman vehicles diminishes the risk to pilots and enhances mission success rates in increasingly complex air combat environments. This synergistic relationship improves overall operational efficiency and effectiveness on the battlefield. The Manned and Unmanned Teaming concept is poised to play a crucial role in the future strategic capabilities of air forces, with the integration of such systems serving as a pivotal factor in achieving both strategic and tactical advantages.
The integrated and operational impact of loyal wingman aircraft in modern air forces
The concept of Manned and Unmanned Teaming is paramount in the evolution of contemporary warfare, with the integration of legacy manned air forces and Loyal Wingman systems representing a noteworthy transformation. This operational structure enhances the efficacy of piloted aircraft while concomitantly mitigating operational risks and bolstering mission success rates. Loyal Wingman systems, characterized as unmanned aerial vehicles, serve a supportive role alongside piloted aircraft, functioning collaboratively. These systems are designed to possess lower radar cross-sections, thereby enhancing the stealth of aerial operations and increasing the safety of manned platforms during reconnaissance and strike missions. For instance, a Loyal Wingman can be tasked with the detection and neutralization of enemy air defense systems, enabling piloted aircraft to execute bombing or strike missions with reduced exposure to enemy fire. A thorough analysis of operational scenarios underscores the efficacy of Manned and Unmanned Teaming applications in minimizing aircraft attrition. Such scenarios elucidate the critical functions performed by the sensor and weapon systems integrated into Loyal Wingman vehicles, which effectively contribute to safeguarding piloted aircraft. Specifically, these systems are capable of conducting precursor missions, facilitating target identification, and determining enemy positions, allowing pilots to engage targets from safer distances. In conclusion, an air force augmented by Loyal Wingman vehicles diminishes the risk to pilots and enhances mission success rates in increasingly complex air combat environments. This synergistic relationship improves overall operational efficiency and effectiveness on the battlefield. The Manned and Unmanned Teaming concept is poised to play a crucial role in the future strategic capabilities of air forces, with the integration of such systems serving as a pivotal factor in achieving both strategic and tactical advantages.
The integrated and operational impact of loyal wingman aircraft in modern air forces
The concept of Manned and Unmanned Teaming is paramount in the evolution of contemporary warfare, with the integration of legacy manned air forces and Loyal Wingman systems representing a noteworthy transformation. This operational structure enhances the efficacy of piloted aircraft while concomitantly mitigating operational risks and bolstering mission success rates. Loyal Wingman systems, characterized as unmanned aerial vehicles, serve a supportive role alongside piloted aircraft, functioning collaboratively. These systems are designed to possess lower radar cross-sections, thereby enhancing the stealth of aerial operations and increasing the safety of manned platforms during reconnaissance and strike missions. For instance, a Loyal Wingman can be tasked with the detection and neutralization of enemy air defense systems, enabling piloted aircraft to execute bombing or strike missions with reduced exposure to enemy fire. A thorough analysis of operational scenarios underscores the efficacy of Manned and Unmanned Teaming applications in minimizing aircraft attrition. Such scenarios elucidate the critical functions performed by the sensor and weapon systems integrated into Loyal Wingman vehicles, which effectively contribute to safeguarding piloted aircraft. Specifically, these systems are capable of conducting precursor missions, facilitating target identification, and determining enemy positions, allowing pilots to engage targets from safer distances. In conclusion, an air force augmented by Loyal Wingman vehicles diminishes the risk to pilots and enhances mission success rates in increasingly complex air combat environments. This synergistic relationship improves overall operational efficiency and effectiveness on the battlefield. The Manned and Unmanned Teaming concept is poised to play a crucial role in the future strategic capabilities of air forces, with the integration of such systems serving as a pivotal factor in achieving both strategic and tactical advantages.