LEE- Sistem Dinamiği ve Kontrol-Yüksek Lisans
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ÖgeAerial package delivery via smart parachute-payload system(Graduate School, 2024-07-12)Aerial robots are being used in many areas, they are employed by civilian and military industries. One of the growing sectors is aerial package delivery. Commonly cargos are brought to customers with trucks or cars. Compared to aerial delivery this method is inefficient. The time customers get their cargos can be shortened by making use of drones and this process also requires less manpower due to automatization of these devices. This is also better for nature because unlike most land vehicles, drones do not use fossil fuel as an energy source. Currently, some large companies in the e-commerce business are producing their own unmanned aerial vehicles and developing methods for this type of delivery. A company is already delivering healthcare supply via drone delivery. However, most of them carry one parcel with a single drone at a time. In addition, drones, especially quadcopters, consume vast amounts of energy when travelling through the air. This process can further be improved by delivering multiple cargos at a time, and energy consumption can be reduced. In this thesis, a package delivery system which can distribute multiple parcels at a time is discussed. The system was designed on computer aided design software, and mechanical parts were manufactured via 3D printer. After manufacturing physical system constants were determined and system was mathematically modelled. Because of nonlinearities in the model, it was linearized using Taylor Series expansion. After the modeling process three different controller structures were developed for the system. Firstly, a PID controller was designed and by running simulations, its performance analyzed. Secondly, another controller structure which is widely used in unmanned aerial vehicles, cascade PID controller was designed. Moreover, a cascade LQR controller was designed to see whether performance of the system can be enhanced. Finally, the performance of these controllers is compared based on their time response characteristics. A real-life scenario is discussed how these structures would perform based on Türkiye's wind data.
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ÖgePerformance of fractional order controllers for two axis gimbal system(Graduate School, 2023-09-21)The importance of enhanced performance provided by air attack systems has been steadily increasing over time. Typically, these systems encompass navigation and surveillance functions. Gimbal systems comprise mechanical or electronic devices designed to meet specific requirements related to surveillance, navigation, and target tracking. In order to provide high target tracking capability for the gimbal system used, a fractional-order proportional-integral (FOPI) controller has been designed in the speed loop. To compare the designed fractional-order controller with the traditional integer-order controller structure, a system description was initially made, and the system model was obtained. In this study for the yaw axis of the gimbal system, the FOPI controller is developed using Tustin, Simpson, and Al-Alaoui discretization methods. Simulation and real system outputs of these discretization methods employed in the FOPI controller are obtained. The performance of integer-order and fractional-order controllers is compared by presenting numerical data. Various optimization methods are employed for the fractional-order controller. These methods are tested on the real system, and the improvements in the controller are presented.
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ÖgeDesign, modelling and control of a nano quadrotor withmicrocontroller based vision system for object tracking(Graduate School, 2023)The quadrotor industry is developing rapidly thanks to the advancements in many technological fields like control systems, navigation systems, communication systems and so on. The improvements in different technological fields allow the quadrotors to be used in different areas like security, delivery, military, entertainment et cetera. Another very rapidly growing sector is machine vision and artificial intelligence technology. With the latest developments in vision systems, machines can see their environment and detect and recognize objects around them and with the help of artificial intelligence they can take actions accordingly just like humans. So, the combination of quadrotor and machine vision technologies has enormously big area of application. In this thesis study, a nano-quadrotor with a microcontroller-based vision system was developed for the researchers and the students who work on control and image processing fields as a compact, inexpensive and practical solution. The developed nano-quadrotor has two microcontrollers on it where one of them is dedicated for the image processing and the other one is dedicated for the control and other tasks. These microcontrollers are on a single PCB board which is used as the body of the nano-quadrotor. The arms of the quadrotor were produced by 3D printer and coreless motors were preferred in order to make the quadrotor light weight. In the first chapter of this thesis, a brief introduction about the quadrotors and the image processing was given. In the second chapter, some of the previous researches and studies that are related to this thesis were briefly mentioned. In the third chapter, the hardware design of the nano-quadrotor was presented. The electronical design and components of the main board, the design of the arms and other selected parts were explained. In the fourth chapter, the mathematical model of the quadrotor was derived. The nonlinear model was derived and shown in state-space representation. Lastly the model was linearized to use linear controller. In chapter five, the control system design of the quadrotor was presented. The designed PID controllers, sensor fusion and state estimation systems and parameter identification processes were given. In chapter six, the general idea of image processing and its usage in microcontrollers were explained. The suitable image processing methods were discussed. Finally, the proposed image processing method for object tracking and its usage in the control system were presented. In chapter seven, the conducted tests and their results for evaluating the system performance were given. The flight scenarios were explained and the recorded flight data was shown in graphs. Lastly in chapter eight, the system performance was evaluated based on the conducted test results and some improvement suggestions for future work were given.
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ÖgeBody roll control of a lightweight military ground vehicle under recoil impulse using gyrostabilizers(Graduate School, 2023-06-21)Future ground combat vehicles are anticipated to be unmanned, in contrast to the heavily armoured vehicles of today. By eliminating the crew, the need for thick protective armour is also eliminated. This reduction in armour results in lighter vehicles, enhancing mobility and logistics capabilities. Despite being lighter and smaller, an effective armament is still a requirement. One suitable choice is a 40 mm chain gun with a stabilized turret, offering armour penetration capability and versatility with various types of ammunition. However, firing a large-calibre gun from a lightweight platform poses challenges to vehicle stability and gun aiming. This study proposes a body roll control technique for a lightweight ground combat vehicle, specifically addressing the stability concerns caused by the firing impulse of a large calibre gun. Traditionally, recoil problems are handled on the gun side, but this technique focuses on solving the issue on the platform side. The novel approach involves measuring the vehicle's body roll and applying a counter moment using gyrostabilizers, a first-time application for this purpose. The worst-case scenario of broadside firing is considered. The platform is modelled as a half-car engaged with a damped harmonic oscillator representing the recoiling gun. Three degrees of freedom are considered in the model, and disturbance forces from the gun and road are incorporated. To generate a counter moment, twin constant spin, single gimbal gyrostabilizers are employed. The moment produced by the gyrostabilizers are adjusted by precisely controlling their precession rates. Overall system exhibits nonlinear characteristics, with mismatched disturbance. Initially, PID control approach is applied. Results came out to be mediocre due to the impulsive characteristics of disturbance force and nonlinear characteristic of the system. Later, to enhance the performance of PID, Fuzzy Logic Controller (FLC) are implemented to adaptively change the gains of the PID controller. The Fuzzy Tuned PID controller showed overall better performance. Subsequently, a sliding mode control (SMC) scheme is utilized, but to address the chattering issue, different switching functions proposed in literature are adopted. The Super Twisting switching function (STSMC) with the boundary layer approach are resulted best among all. All control schemes are compared in terms of error, power consumption and other feasibility constraints. Not only the gun disturbance but also the road disturbance ability of the proposed technique is demonstrated is simulation environment. Finally, a test setup is established to further test the concept and compare control schemes. The actual size simulation model is scaled down for practical reasons, and PID and SMC controllers are embedded into the hardware. Test results confirm the compensation of body roll due to firing impulse, with the STSMC performing better, consistent with the simulation results. In conclusion, the study demonstrates successful control of body roll in a vehicle with small rotational inertia, compensating for disturbances caused by gun firing and rough terrain. The outcomes contribute to the safety, stability, and aiming performance of future ground combat vehicles.
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ÖgeLearning to walk on a human musculoskeletal system with powered prostheses(Lisansüstü Eğitim Enstitüsü, 2022-10-25)Generally, due to traumatic or vascular disorders, in some people, the lower leg is cut from below the knee and separated from the body. This procedure is called transtibial amputation. These people have difficulty in activities that require active use of leg muscles such as walking, running, climbing and getting support from the ground, and are generally unable to perform them, due to the loss of the integrity of one of their legs. Various prostheses have been designed so that transtibial amputees can perform walking, which is of great importance in daily activities. Among these prostheses, passive prostheses that do not produce active power and do not have a control loop, but are relatively more accessible for these reasons, are frequently used. Thus, individuals can use their shortened limbs to transfer loads to the floor with the help of passive prostheses and perform the walking action. However, in addition to the cost advantage and good accessibility, these passive prostheses cannot fully provide the functions of a healthy leg that benefits from the lost ankle joint and surrounding muscles. Among these functions, active force generation and variable shock damping are the most prominent ones. Active force generation is involved in the propulsion of the human body by pushing the body forward. Variable impact damping, on the other hand, serves to absorb the impact created by the instantaneous force on the ground at different paces and at different ground height changes. The loss of these important functions leads the person to complete these deficiencies in different ways. For example, passive prosthesis does not contribute actively to progress, and it must be lifted and carried forward with the help of other muscles in the body. Or, the amount of impact damping depends on the structural design and material properties of the passive prosthesis with constant rigidity and cannot be changed instantly. For this reason, people have to provide the impacts that occur against environmental variables and changing the walking tempo by changing their walking styles. It is seen that the hip workload increases in this type of walking. As a result of all these effects, the gait of the amputated people changes compared to before the amputation. Various muscles have to work harder, while various joints tend to angle differently from normal walking. As a result, the muscles and joints in the body work more and the comfort level decreases. In order to prevent these problems, it is aimed to add healthy ankle functions to newly designed prostheses. This type of prosthesis is called active prosthesis. Active prostheses aim to provide a gait closer to normal gait with various control strategies. Control strategies are made with predictive models created with previously collected data, and studies are also carried out on controllers with myoneural interfaces that act directly with the will of the person using it. In order for the designs that emerged through research to become the final product, they need to go through a number of design processes. Clinical testing and prototype productions are included in these design processes. Experiments in various human groups are required for clinical testing. Prototype productions are repeated with changes in design. These processes come back in time and cost, and from time to time they appear as an obstacle or limiting factor in the work. Reducing these processes is important in terms of increasing the target audience and scope of the studies to be carried out. Computer-aided design and simulation tools have long been used in various industries to accelerate design processes. Generally, these tools create three-dimensional or two-dimensional designs of artificial systems and enable them to be developed by evaluating them with simulations in terms of various design constraints. These simulation environments also include static and dynamic evaluations. However, these systems mostly consist of mechanical systems. It is difficult to model and simulate biological systems such as the human musculoskeletal system. Models created with these difficulties had to be created with a lower number of degrees of freedom, actuators and rigid parts than the real system for a long time, due to the high need for processing capacity to be used in the control phase. This situation has recently changed with the relative increase in accessible processing power, resulting in computer modelling of structures much more similar to the human musculoskeletal system. Models of the musculoskeletal system more similar to the degrees of freedom in humans can be manipulated with deep reinforcement learning controllers. These controllers can imitate the walking animations given to them to learn by using the muscles in the musculoskeletal system. Although it is still early to test behavioural movements such as long-term movement planning in a simulation environment, there is a great opportunity to test various artificial systems that will interact with the musculoskeletal system. Researchers working at Seoul National University and Seoul National University Hospital have shared the source code of musculoskeletal system and deep reinforcement learning controllers for use in further studies. In the thesis study, various characters with a deep reinforcement learning controller with the shared musculoskeletal system were created. The purpose of using these characters is to test active prosthetic controllers in interaction with a walking musculoskeletal system. The first of the characters represents a healthy person with the original musculoskeletal system, while the other three characters are transtibial amputees. One of the amputee characters uses a simple passive prosthesis, while the other two characters use two different active prostheses with their own controllers. Controllers of active prostheses make use of a prediction model. The prediction model was created with the data collected during the walking of the previously trained characters. In the first active prosthesis, the prediction model created by walking a healthy virtual character, while the prediction model created by walking a character with a passive prosthesis was used in the second active prosthesis. Walking performances were evaluated by running four different character simulations. The reward function, which is also used in deep reinforcement learning, was used as an evaluation criterion. Common limbs were evaluated for all four characters. Thus, it is ensured that the error used in the reward function is not low for characters with less limb number and no advantage is given due to calculation. When the reward values obtained in walking were examined, it was seen that the character with a healthy musculoskeletal structure exhibited the highest performance. Passive prosthetic character remained at the lowest performance value. Among the characters with active prosthetics, it was observed that the character using the passive prosthetic gait data in the prediction model provided better performance. An exemplary study was obtained for the use of virtual characters in design processes. At the same time, the muscle activations used by the characters during walking were recorded for further studies.