A Novel Obstacle Avoidance Approach For Nonholonomic Ground Vehicle Autonomy

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2012Bu çalışmada, holonom olmayan bir kara taşıtı için, “Boşluğu Takip Et” (BTE) isimli yeni bir engelden kaçma ve çarpışma önleme metodu geliştirilmiştir. Bu metod, probleme yeni bir çözüm getirmektedir ve diğer metodlara göre çeşitli avantajlara sahiptir. Geliştirilen metodun, benzer metodlarla yapılan karşılaştırılmalar sonucunda, daha güvenli güzergahlarla sonuçlandığı gösterilmiştir. Ayrıca BTE, yapay potansiyel alanlar (YPA) metodu ve bu tabanda çalışan diğer tüm metodların ortak problemi olan lokal minimum probleminden bağımsızdır. BTE’nin bir diğer özelliği, aracın holonom olmayan kısıtlarını ve sensörlerin görüş açısı kısıtlarını da göz önünde bulundurabilmesidir. BTE’nin tamamen reaktif yapısı sayesinde, yalnızca durağan engellerden değil, hareketli engellerden de rahatlıkla sıyrıldığı da tez içerisinde gösterilmiştir. Son olarak, sadece bir ayar parametresine sahip olduğu için, kullanımı da oldukça kolaydır. Engelden kaçınmak için, yalnızca aracın yönelim açısının belirlenmesinin yetmeyeceği düşüncesinden hareketle, aracın engelli bir ortamda hız planlaması için de yeni bir metod geliştirilmiştir. İki adet bulanık çıkarım sisteminin (BÇS) tasarlanmasıyla oluşturulan bu yeni yapı, engellerin oluşturduğu risk durumuna ve aracın yönelim açısına bağlı olarak çalışır. Planlanan hızın takip edilmesi için de yine bulanık mantık kullanılarak yeni bir alt seviye hız kontrolörü tasarlanmıştır. Tasarlanan tüm metodlar, literatürdeki bezerleriyle simülasyon ortamında karşılaştırılmış ve sonuçları gösterilmiştir. Geliştirilen her üç yeni metod, tam otonom kara taşıtı (OKT) üzerinde deneysel olarak da test edilerek sonuçların başarılı olduğu gösterilmiştir. Simülasyonlarda kullanılan araç modelleri ve deneysel düzeneğin tasarımı da tez içerisinde ayrı bölümler halinde anlatılmıştır.In this study, a new obstacle avoidance algorithm “Follow the Gap Method” (FGM) is designed for nonholonomic ground vehicle autonomy. The proposed method brings a new solution to the problem and has several advantages compared to previous methods. Fisrstly, the FGM results in safer trajectories than other compared approaches. This new method is free from local minima which is a big problem for Artificial Potential Fields (APF) and similar methods. Taking into consideration the field of view and the nonholonomic constraints of the vehicle is another advantage of the FGM. Through the purely reactive nature of the FGM, it is shown that not only the static but also the dynamic obstacles are avoided. Besides these, it is easy to tune the algorithm with only one tuning parameter. Vehicle speed is as important as the appropriate steering angle for obstacle avoidance. From this view point, a new speed planning method is designed for the vehicle. Two fuzzy inference systems operate depending on the danger level of the obstacles and the steering angle. In order to track the speed commands from the speed planner, a new low level speed controller is designed based on fuzzy rules. All designed methods are simulated and compared with other methods in literature. The designed methods are also tested experimentally using the real unmanned ground vehicle (UGV) platform and it is shown that experimental results are successful too. The used models for the simulations and designed experimental platform are illustrated in separated sections throughout the thesis.DoktoraPh

Modeling And Optimal Power Management Of A Parallel Hybrid Electric Vehicle

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2008Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2008Bu çalışmada, bir paralel hibrit elektrikli araç matematiksel olarak modellenmiş, yakıt tüketimini azaltma amacıyla bir optimum güç yönetim algoritması(MOES) geliştirilmiş ve bu algoritma araç modellerine uygulanarak kontolcülü aracın klasik araçla yakıt tüketimi açısından karşılaştırılması simülasyon sonuçlarıyla gösterilmiştir. Kontrol algoritması eşdeğer yakıt tüketimi tabanlı olmakla birlikte, algoritmada rejeneratif frenlemenin paralel şarja oranı olarak tanımlanan yeni bir değişken kullanmış ve formülasyon da toplam verimi maksimize etmeye yönelik ifade edilmiştir. Bu yaklaşımda araç bir sistem olarak ele alınarak tüm sistem verimi maksimize edilmeye çalışılmaktadır. Simulasyonlar, klasik mod, sadece rejeneratif frenleme modu ve optimizasyon algoritmasını içeren 3 farklı modda ECE şehir içi sürüş çevrimi kullanarak CarMaker yazılımı kullanılarak yapılmıştır. Buradaki amaç, optimizasyonun ve rejeneratif frenlemenin yakıt tüketimi minimizasyonununa etkilerini ayrı ayrı inceleyebilmektir. Sonuçlar incelendiğinde kontrol algoritmasıyla, yakıt tüketimi minimizasyonu açısından başarılı sonuçlar elde edildiği görülmüştür.In this study, a parallel hybrid electric vehicle was modeled mathematically, an optimum power management algorithm(MOES) was developed for fuel consumption minimization, this algorithm was integrated into the developed vehicle model and the controlled vehicle was compared with conventional vehicle in terms of fuel consumption. Even though MOES has some similarities with equivalent consumption minimization strategy, it uses a new variable which is the ratio of gained energy of parallel charge and regenerative braking and its formulation is different to express the overall efficiency term. In this strategy, vehicle is thought as a system and aim is maximizing the overall efficiency of the vehicle. Simulations were performed in three different control modes; conventional mode, only regenerative braking mode and optimization algorithm mode using CarMaker software in ECE cycle’s inner city part. The aim of these 3 simulations is analyzing effects of regenerative braking and optimization into fuel consumption minimization separately. When it is compared with the conventional mode of the vehicle, successful fuel consumption minimization was obtained with this new control strategy in the simulations.Yüksek LisansM.Sc

Conversion of a Conventional Wheelchair into an Autonomous Personal Transportation Testbed

Personal transportation is the act of transporting an individual by using a small, low-speed vehicle. It is a very hot research topic both in industry and academia. There are many different types of personal transportation vehicles, and wheelchairs are one of them. Autonomous driving is another very popular subject that is applicable to the personal transportation vehicles. Autonomous personal transportation vehicles are good examples of service robotics applications. In this study, conversion procedure of a conventional electric wheelchair into an autonomous personal transportation testbed and the application of some basic autonomous driving algorithms on the developed testbed are explained. In literature, there are several studies providing information on wheelchairs’ autonomy but not deep information about the conversion itself. In this paper, the conversion process is investigated in detail, under two main sections. The first part is by-wire conversion, which allows the wheelchair to be controlled via computer commands. The second part includes the studies on sensors, computational system, and human interface. After making such modifications on wheelchair, fundamental algorithms required for autonomy, such as mapping and localization, are implemented successfully. The results are promising for the usage of the developed system as a testbed for examining new autonomous algorithms and evaluating the performance of the perceptional/computational components

The frequency of Duchenne muscular dystrophy/Becker muscular dystrophy and Pompe disease in children with isolated transaminase elevation: results from the observational VICTORIA study

IntroductionElevated transaminases and/or creatine phosphokinase can indicate underlying muscle disease. Therefore, this study aims to determine the frequency of Duchenne muscular dystrophy/Becker muscular dystrophy (DMD/BMD) in male children and Pompe disease (PD) in male and female children with isolated hypertransaminasemia.MethodsThis multi-center, prospective study enrolled patients aged 3–216 months with serum alanine transaminase (ALT) and/or aspartate transaminase (AST) levels >2× the upper limit of normal (ULN) for ≥3 months. Patients with a known history of liver or muscle disease or physical examination findings suggestive of liver disease were excluded. Patients were screened for creatinine phosphokinase (CPK) levels, and molecular genetic tests for DMD/BMD in male patients and enzyme analysis for PD in male and female patients with elevated CPK levels were performed. Genetic analyses confirmed PD. Demographic, clinical, and laboratory characteristics of the patients were analyzed.ResultsOverall, 589 patients [66.8% male, mean age of 63.4 months (standard deviation: 60.5)] were included. In total, 251 patients (188 male and 63 female) had CPK levels above the ULN. Of the patients assessed, 47% (85/182) of male patients were diagnosed with DMD/BMD and 1% (3/228) of male and female patients were diagnosed with PD. The median ALT, AST, and CPK levels were statistically significantly higher, and the questioned neurological symptoms and previously unnoticed examination findings were more common in DMD/BMD patients than those without DMD/BMD or PD (p < 0.001).DiscussionQuestioning neurological symptoms, conducting a complete physical examination, and testing for CPK levels in patients with isolated hypertransaminasemia will prevent costly and time-consuming investigations for liver diseases and will lead to the diagnosis of occult neuromuscular diseases. Trial RegistrationClinicaltrials.gov NCT04120168

Design of a Semi-Autonomous Electric Wheelchair Controlled by Head Movements

In this study, the design and development of a semi-autonomous electric wheelchair which is controlled by head movements is explained. For the system to function at the desired level, various algorithms are specially adapted to the system in the framework of the defined problem. The user is able to turn on and turn off the system or switch between assisted and unassisted driving modes, by doing the special pre-defined head movements. In the assisted driving mode, which constitutes the main scope of the work, the semi-autonomous system supports and improves driving by interfering in different rates when it is necessary. So that the faulty user inputs do not result with dangerous situations. The algorithms for a semi-autonomous solution are tested on a real wheelchair platform successfully and the results are presented