Haberleşme temelli tren kontrol sisteminde emniyetli fren modeli
Safe braking model in communication based train control system
Yazar: CAN BERK GENÇER
Danışman: PROF. DR. MEHMET TURAN SÖYLEMEZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Raylı Sistemler Mühendisliği Ana Bilim Dalı / Raylı Sistemler Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2020
Konu: Ulaşım = Transportation

Özet:
İnsanlık tarihi kadar bir geçmişi olan ulaşım sistemlerinin günümüzde geldiği nokta ile başlangıçtaki konumunu kıyaslandığında arada çok büyük bir değişim olduğunun farkına varılabilir. Artan kentleşme, ekonomik refah, yakıt maliyeti, trafik sıkışıklığı ve çevre sorunları toplu taşıma pazarında rekabete neden olmaktadır. Bu sorunlar, verimli toplu taşıma sistemlerine olan ihtiyacı artırmaktadır. Raylı sistem endüstrisi de yüksek güvenilirlik seviyesinde insanları düşük maliyetle taşımak için her geçen gün daha verimli bir yol arama zorluğu ile karşı karşıyadır. Bu zorluklara karşı raylı sistemlerin performansına en çok katkıda bulunan teknik alanlardan biri sinyalizasyon sistemleridir. Sinyalizasyon sistemleri trenlerin emniyetli, zamanında ve ekonomik bir şekilde işletilmesini sağlar. Burada ki emniyetli işletimi sağlamak için geleneksel sinyal sistemleri, fiziksel bloklar ile hatları bölerek ve her bloğa yalnız bir tren girmesine izin vererek trenlerin çarpışmasını engellemektedir. Raylı sistem araçları çelik tekerleğinin çelik raya temas ederek oluşturduğu düşük sürtünme kuvveti ile yuvarlanma direncini düşürerek hareket ederler. Düşük sürtünme kuvveti enerji tasarrufunu sağlamasına karşın, uzun fren mesafesini de beraberinde getirir. Uzun mesafelerde sabit blok sistemleri, tek bir hat bölgesinde tek araç mantığı ile işletmenin performansını olumsuz yönde etkilemektedir. Teknolojin gelişmesi ve toplu taşıma pazarının ihtiyaçlarını karşılamak için hatların kapasitelerinin artırılması gereksinimi doğmuştur. Bu gereksinime istinaden fiziksel blokların yerini hareketli blok sistemleri almıştır. Hareketli blok sistemleri emniyet mesafesinin artık sabit bloklar tarafından uygulanan fiziksel bir mesafeden değil, tren hızının gerçek zamanlı hesaplamasına ve en kötü durum koşulları göze alınarak trenlerin emniyetli bir şekilde ayrılmasıdır. Emniyetli tren ayrımı işlevi emniyetli fren modeli oluşturularak, ATP hız profilinin belirlenmesi ile sağlanmaktadır. Hareketli blok sistemleri kentsel taşımacılıkta tercih edilen Haberleşme Temelli Tren Kontrolü (İngilizce kısaltması ile: CBTC) sistemlerinde kullanılmaktadır.
Bu çalışmada ilk olarak trafik yönetimi ve altyapı kontrolü için tren ve hat boyu ekipmanları arasında çift yönlü haberleşme ile bir trenin kesin konumu, geleneksel sinyal sistemlerine göre daha noktasal olarak belirlenmesi temeline dayanan CBTC sisteminin mimarisi, fonksiyonları ve konfigürasyonları anlatılmıştır. Trenlerin emniyetli olarak birbirinden ayrılmasını sağlayan emniyetli fren model belirlenmesinde farklı yaklaşımlar incelenmiştir. IEEE 1698 standardının emniyetli fren model yaklaşımına göre bir formülasyon oluşturulup Matlab programı yardımıyla koda dönüştürülerek grafik arayüzü ile parametrelerin etkisi incelenmiştir. İki farklı araç parametresi girilerek emniyetli fren modeli uygulaması yapılmış en çok etkileyen parametre değerinin model üzerindeki etkisi incelenmiştir. Formülasyonun doğrulanması amacıyla benzer parametreler kullanılarak OpenTrack simülasyon programı yardımıyla en kötü koşul frenleme mesafeleri karşılaştırılmıştır. Son olarak oluşturulan algoritmaya hız limitleri girilerek model üzerindeki etki incelenmiştir.

Abstract:
It can easily be realized that there is a huge change between the transportation systems that have a history as much as human history compared to the point they have reached today and their original position. Increasing urbanization, economic prosperity, fuel costs, traffic congestion and environmental problems cause competition in the public transport market. These problems increase the need for efficient public transportation systems. The rail system industry also faces with the challenge of seeking a more efficient way to move people at a high level of reliability at a low cost. Signalling systems are one of the technical areas that contribute most to the performance of rail systems against these difficulties.
Signalling systems ensure safe, timely and economical operation of trains. The traditional signal systems prevents train from accidents by dividing the physical blocks and track. This allows only one train to enter each block to ensure safe operation. In other words, this prevents the collision of the trains. Rail system vehicles move by lowering the rolling resistance with the low friction force created by the steel wheel touching the steel rail. Although low friction force provides energy saving, it also brings long braking distance. Long-distance fixed block systems adversely affect the performance of the enterprise with a single-vehicle logic in a single line region. In order to improve technology and to meet the needs of the public transport market, there was a need to increase the capacities of the lines. Based on this requirement, physical blocks have been replaced by moving block systems. Moving block systems are no longer a physical distance applied by fixed blocks, but a safe separation of trains through taking into account the real-time calculation of train speed and worst-case conditions. Safe train separation function is provided by determining ATP speed profile by calculating safe braking model. Moving block systems are used in Communication Based Train Control (CBTC) systems which are preferred in urban transportation.
CBTC is a rail system signalling system based on bidirectional communication between train and wayside equipment for traffic management and infrastructure control. Through CBTC systems, the precise location of a train is determined more precisely than conventional signal systems. This solution is a more efficient and secure system for managing rail system traffic. 
The system is implemented by various suppliers around the world in subways, light rail systems and automatic human transport at airports. CBTC standards were first defined in 1999, about twenty years after the system was developed by the first supplier. General characteristics of the functions of automatic train protection (ATP), automatic train operation (ATO) and automatic train supervision (ATS) are described by the standards. The automatic train control (ATC) system is a control system consisting of a combination of ATP, ATO and ATS systems and it is utilized to define the rail systems architecture operated automatically in the world.
There are many types of ATC systems in the world, yet all of them basically provide ATP safety. ATO provides stop commands at stations, and ATS controls train regulation times. The ATC system is a combination of three subsystems on the train: the ATP subsystem will carry out safe train movements. The ATO subsystem will control and regulate train speed and station stops. The automatic train control subsystem will provide a wayside communication link from the train. IEEE 1474 explains how a CBTC system is in the basic CBTC characteristics. When the term CBTC is used, it is often described as an automated driverless system, but there is no reference to "driverless" or "automation" anywhere in IEEE 1474. This standard accepts that different CBTC configurations are possible depending on the specific application.
The thesis is composed of 5 chapters. After mentioning the purpose and planning of the thesis within the introduction, the second chapter introduces the signalization systems by mentioning the differences between the rail systems and other modes of transportation. In rail systems, fixed and moving block principles that arise due to long braking distances are discussed. The advantages of moving block systems and the concept of train separation are also mentioned. The next section discusses why the CBTC system is needed. CBTC system standards and architecture in general are elaborated. Functions and subcomponents described by IEEE 1474 standard are also explained. The third chapter also questions how these cross-component configurations should be. By explaining the relationship between grade of automation and CBTC systems, increasing status grade of automation are examined.
The fourth chapter discusses the safe braking model which provides safe train separation among all trains operating in the CBTC region, regardless of whether the trains are equipped with CBTC or not. The safe train separation function provides safe separation of CBTC equipped trains by determining the ATP speed profile from the safe braking model, which is later pointed out in the thesis. In case of operating mixed-mode (trains that are not equipped with CBTC on the same line as those equipped with CBTC), safe train separation should be ensured by strict adherence to auxiliary secondary train detection equipment (axle counter / track circuit etc.) and/or operating procedures. In determining this model, different approaches are examined by examining the basic brake models described by EN 14531, European rail traffic management system (ERTMS), IEC 62290, IEEE 1474 and IEEE 1698. 
Based on the IEEE 1698 standard, safe braking model components have been examined. This model is divided into 3 stages by introducing a different approach. According to these stages, a mathematical model has been created. This model provides emergency brake speed output according to 13 different track and ATP onboard vital computer parameters. This value represents the maximum speed that the vehicle can drive in a given track zone. In case of exceeding this speed on the system or vehicle side, emergency brake is to be applied.
The safe braking model formulation created was encoded with the help of the Matlab program and the model effect of the parameters has been directly observed thanks to the graphical user interface. In order to be an input parameter in the Matlab program, 2 different vehicle parameters have been created. According to these two parameters, safe braking model are calculated and changes of parameters are observed. The guaranteed emergency brake rate (GEBR) parameter, which affects the safe braking model the most, has been studied. The adhesion known as rail and wheel adhesion on this GEBR parameter was examined and its effect on emergency brake speed was examined. In order to verify the safe braking model created, it was provided to compare models created with similar input parameters using the OpenTrack simulation tool, which is a proven program in the rail system industry. 
Different algorithms have been created by entering speed limits in the created Matlab algorithm. These algorithms are entered into the Matlab program in Beta form and observed over the graphical user interface. Considering the most restrictive speed profile, the calculation is based on the most restrictive speed. In the basic braking model, the part without the speed limits is in the alpha section. Beta is the part that operates on the braking model in case of any speed limit. The speed limit is the highest speed value of the train, which comes with the movement authority in general or temporarily applied to the desired part of the track zone. The calculated speed is the speed value calculated according to the overlap points. The calculated value is determined according to the most restrictive speed principle. The maximum speed is one of the parameters entered into the algorithm and the highest speed value that the train can go in case there is no speed limit in the related line region. The final speed is the speed value created according to the target point (endpoint of the movement authority). This model shows the model used from real systems.
The last section discusses how important the safe braking model is for train separation. For the safe braking model, it is suggested that it can be expanded further by entering more parameters.