As technology progresses in recent years, the advances in transportation continue rapidly. Some of these advances are seen in the railway industry. Especially the innovations in the railway interlocking system make this industry more preferable. One of these innovations is moving block signaling. In an urban rail transport system, moving block signaling has gradually started to replace the fixed block signaling with the development of driverless and communication-based control systems. In this study, an approach has been proposed for moving block signaling. The movement situations between the stations have been shown, by determining a reference speed profile and the relationship between the locations for the following railway vehicles have been evaluated by simulations obtained by MATLAB/SimulinkTM.

This article proposes an algebraic model predictive control (MPC) method for automatic landing. While defining the constraint functions in the optimization problem, the tangent hyperbolic function is preferred. Therefore, the optimization problem turns into an unconstrained, continuous, and differentiable form. An analytical two-step method is also proposed to solve the rest of the problem. In the first step, it is assumed that only input constraints are active and states are unconstrained. The optimal solution for this case is calculated directly with the optimality condition. The calculated control signal is revised in the second step according to system dynamics and state constraints. Simulation results of the auto-landing system show that the MPC computation speed is significantly increased by the new algebraic MPC (AMPC) without compromising the control performance, which makes the method realistic for using MPC in systems with high-speed changing dynamics.

Bu çalışmada, doğru akım (DA) raylı ulaşım sistemlerinde rejeneratif enerji kazanımını gerçekleştiren şebeke bağlantılı üç fazlı evirici birimine yönelik yeni bir kontrol mekanizması önerilmiştir. DA raylı ulaşım sistemlerinde trenlerin frenleme sırasında üretmiş olduğu rejeneratif enerjiye bağlı olarak hat gerilimi hızlı şekilde değişebilmektedir. Hat gerilimindeki bu değişimlere hızlı cevap vermek amacıyla evirici birimi kontrol yapısı içerisinde, baskın kutup atama yöntemine göre tasarlanan bir oransal-integral-türevsel (PID) kontrolör kullanılmıştır. PID içerisinde yer alan türevsel etki ile sistem tepkisi hızlandırılmış böylelikle hat gerilimindeki değişimlere hızlı cevap verilmesi sağlanmıştır. Ayrıca literatürdeki sabit gerilim değerinde çalışmasını gerçekleştiren sistemlerden farklı olarak iki farklı gerilim değerini dikkate alan yeni bir çalışma stratejisi önerilmiştir. Böylece, evirici çalışma bölgesi artırılarak daha fazla rejeneratif enerji kazanımı ile enerji verimliliğine katkı sağlanmıştır. Son olarak, Matlab/Simulink ortamında gerçek bir sistemin ayrıntılı modeli oluşturulmuş ve önerilen yöntemin uygulanabilirliğini göstermek amacıyla PID tabanlı kontrol yapısının performansını PI tabanlı kontrol ile karşılaştıran benzetim çalışmaları sunulmuştur.

Safety-critical systems are widely used in many sectors to prevent fatal accidents and prevent loss of life, damage of property, or deterioration of the environment. Implementation of software safety standards as part of the development of safety-critical software is generally considered an essential element of any safety program. Therefore, it has become more critical to produce highly reliable software to meet the safety requirements established by functional safety standards, such as IEC 61508, ISO 26262, and EN 50128. IEC 61508 supports well-known safety mechanisms such as design diversity like N-version (multi-version) programming. N-version (multi-version) programming is a method where multiple functionally equivalent programs are independently developed from the same software specifications. N-version (multi-version) programming is particularly an effective approach to increase the quality of software in a safety-critical system. In this paper, one of the well-known and widely used algorithms in the field of N-version (multi-version) programming, the majority voting algorithm, has been modified with an online stability checker where the decisions of the voter are judged against the stability of the underlying system. The plant where all the theoretical results are implemented is a tilt-rotor system with the proposed N-version (multi-version) programming–based controller. The experimental results show that the modified majority voter-based N-version (multi-version) programming controller provides more reliable control of the plant.

In this paper, we propose a novel method to solve the model predictive control (MPC) problem for linear time‐invariant (LTI) systems with input and output constraints. We establish an algebraic control rule to solve the MPC problem to overcome the computational time of online optimization methods. For this purpose, we express system constraints as a continuous function through the tangent‐hyperbolic function, hence the optimization problem is reformulated. There are two steps for the solution of the optimization problem. In the first step, the optimal control signal is determined by the use of the necessary condition for optimality, assuming that there is only input constraint. In the latter, the solution obtained in the first step is revised to keep the system states in a feasible region. It is shown that the solution is suboptimal. The proposed solution method is simulated for three different sample systems, and the results are compared with the classical MPC, which show that the new algebraic method dramatically reduces the computational time of MPC.

Safety-critical systems in various industries such as transportation or nuclear energy have been paid more attention with the development of societies due to increased attachment of importance to the life of human, their property, and nature. While developing such systems, detailed availability and safety characteristics are to be taken into account in parallel with architectural design decisions such as synchronization between different computing units or real-time task management. For fulfilling top-level requirements in international standards, ambitious quantitative targets like 0.012 FIT for HW units are to be reached where the industry has difficulties to achieve it. In this paper, this problem is handled by proposing an augmented Markov model for diverse architectures that is superior to the formulas provided in the main safety standard IEC 61508 and previous studies. With the proposed method it is possible to cover all safety-relevant states, which leads to more accuracy and lower hazard rates helping to reach these ambitious quantitative targets. Besides, the reliability parameters are investigated and optimized to increase safety performance. Consequently, the proposed novel model including enhanced reliability parameters is used for an industry application, namely safety-critical computer used for unmanned metro and high-speed rail transportation. The result obtained by the proposed model is compared with the results obtained using state of art models in literature and using the formulas in IEC 61508. As domain independent references IEC 61508 and Markovian approach are used in the paper, this study is applicable to other safety critical areas such as automotive or avionic industry.

In this paper, a new control method is presented for the 4-poster test systems. The primary aim of the paper is to improve the convergence speed and decrease the error rate for model-based iterative learning control (ILC), a widely used method as a tracking control. First, the dynamic equations of the system are generated, and the control problem is formulated. Then, an inverse model of the system is established directly through the adaptive neuro-fuzzy inference system (ANFIS) with auxiliary parameter (piston position) as a serial combination of two sub-models. In order to construct a neuro-fuzzy ILC (NFILC) structure, these sub-models are integrated into the neuro-fuzzy inverse controller (NFIC). Because of this new structure, the modified ILC rule has two layers. In the first layer, the controlled parameter, namely, the acceleration is iterated, whereas, in the second layer, the auxiliary parameter is iterated. The outcomes of the proposed control method are scrutinized by testing through a numerical simulation. Finally, it is demonstrated that the modified ILC rule dramatically increase the convergence speed and reduce the final error rate.

This paper describes a model for railway signals in the context of interlocking. Since the design and construction of the software models shall be obtained in a formal way, the models were created using Petri nets to allow automatic verification and validation. A generic model for railway signals was designed and further utilized for the German railway signaling systems (The Ks signaling system). Simplified Petri net models for points, track segments and signals are given as a frame. The obtained models are also applied to a real station layout.

This paper makes an evaluation of the safety standards of electrical/electronic/programmable electronic safety-related systems (E/E/PES) with regards to consistency of the information provided in these standards and their applicability. It provides open discussion and proposals for essential moot questions utilizing experiences gained in various safety-critical projects in long years, especially in the railway industry. IEC 61508 and CENELEC EN 50126, 50128 and 50129 are used as safety standards in this study.

The choice of the voting algorithm in N-version programming directly affects the evaluation of the results of N software versions and determines the correct result. The result of the voting algorithm is also the outcome of the N-version software. Therefore, the choice of the voting algorithm is vital. However, many voting algorithms were already developed and they may be selected for implementation, based on the specifics of the analysis of input data of these algorithms. This article presents a brief overview of major fuzzy voting algorithms.

Probably the most important part during a flight is the landing phase because most of the accidents occur in this phase. Automatic landing systems (ALS) take over the control during this phase to avoid potential pilot-induced risks. However, some external disturbances such as windshear can jeopardize the safe landing. In this paper, the flare part of ALS is handled in a different way. A combination of some useful design methods is brought together to improve the performance of the conventional ALS even under severe weather conditions. Model following method is combined with the H∞ synthesis method to find out the optimal solution for a given cost function. Resultant H∞ optimal control problem is solved using Linear Matrix Inequalities (LMIs) and then a dynamic controller is constructed. On the other hand, the overall system is formed into P-K configuration, thus the system can be reconfigured easily when there exists a change in the system such as addition or removal of disturbance, noise and so on. We achieved significant performance on the system without any disturbance. In addition to that, the robustness takes an important role for the flight systems and needs to be handled correctly. Therefore, two kinds of windshear are taken care of and their effects minimized in a way that the tracking performance remains unaffected. Thus, highly considerable results are obtained using the proposed method even under severe weather conditions.

Bu çalışmada, ürünlerin dayanım ve performanslarının belirlenmesi için kullanılan hidrolik test sistemlerinin kontrolü için Model Öngörülü Kontrol (Model Predictive Control- MPC) tasarımı yapılmıştır Sistem kısıtlarının optimal kontrol kuralına dahil edilmesiyle test sistemi uygulamalarında karşılaşılan doyum problemleri için performans artımı sağlanması hedeflenmiştir. Bu amaçla, ilk olarak örnek sistem için sistemin doğrusal olmayan dinamik denklemleri oluşturulmuştur. Model çalışma noktası etrafında doğrusallaştırılarak, ivme durum değişkeni olacak şekilde durum uzayı modeli oluşturulmuştur. Elde edilen model, örnek sisteme ait model parametreleri kullanılarak, MPC içerisinde kullanılmak üzere ayrıklaştırılmıştır. MPC kuralı, yığın metodu (batch method) yardımı ile oluşturularak, kısıtlamalı optimal kontrol problemi arama algoritması yardımı ile çözülmüştür. Kontrol performansının tespiti amacı ile LQR ile karşılaştırmalı sayısal benzetim sonuçları sunulmuştur. Ayrıca sayısal benzetim testleri model belirsizliği ve ölçüm gürültüsü koşulları altında tekrarlanmış ve sonuçlar sunulmuştur. Elde edilen sonuçlar yorumlanmıştır ve gelecek çalışmalar için önerilerde bulunulmuştur.

This study represents a moving block signaling system model. In this system, different from the conventional railway systems, there are access points near the railway and moving trains communicates via them. In this way, not only railway traffic flow is increased but also waiting time for the passengers is decreased, especially in metro lines. In this work, representing a multi-carriage train, multi-degree of freedom mass-spring-damper models are used. Then, a tractive force and braking force are applied to the system as an input and location is obtained from this output. In addition, a limit movement authority is defined for control algorithm. So, trains move according to this authority. Finally, for the safe stop of trains, brake distance value is calculated. This equation is solved depending on the speed of the rear train. So, if the rear train accelerates, the distance will increase according to the square of the speed of the rear train. Besides, depending on the speed of the rear train and travel time, a safety margin distance is obtained. The proposed technic is simulated by using Matlab-Simulink™ and the results including train models, speed profiles, locations, accelerations etc. are shown in Figures.

Bu çalışmada, ürünlerin dayanım ve performanslarının belirlenmesi için kullanılan hidrolik test sistemlerinin kontrolü için Model Öngörülü Kontrol (Model Predictive Control-MPC) tasarımı yapılmıştır Sistem kısıtlarının optimal kontrol kuralına dahil edilmesiyle test sistemi uygulamalarında karşılaşılan doyum problemleri için performans artımı sağlanması hedeflenmiştir.Bu amaçla, ilk olarak örnek sistem için sistemin doğrusal olmayan dinamik denklemleri oluşturulmuştur.Model çalışma noktası etrafında doğrusallaştırılarak, ivme durum değişkeni olacak şekilde durum uzayı modeli oluşturulmuştur.Elde edilen model, örnek sisteme ait model parametreleri kullanılarak, MPC içerisinde kullanılmak üzere ayrıklaştırılmıştır.MPC kuralı, yığın metodu (batch method) yardımı ile oluşturularak, kısıtlamalı optimal kontrol problemi arama algoritması yardımı ile çözülmüştür.Kontrol performansının tespiti amacı ile LQR ile karşılaştırmalı sayısal benzetim sonuçları sunulmuştur.Ayrıca sayısal benzetim testleri model belirsizliği ve ölçüm gürültüsü koşulları altında tekrarlanmış ve sonuçlar sunulmuştur.Elde edilen sonuçlar yorumlanmıştır ve gelecek çalışmalar için önerilerde

Developing safety critical systems require long years of planned investments, broad theoretical knowledge and domain experience. Data interchange between CPUs, synchronization, computation speed and diagnostic measures shall exhaustively be evaluated along with the effects of the parameters used in the reliability and safety calculations ex tunc. This study focuses on the effects of calculation parameters for different architectures. Special attention is paid for the architecture 1oo2D regarding its model and normative definition. It has also been revealed that there are correlations between some parameters which seem independent. An advising route map is created to distill what kind of methods can be applied to decrease the hazard rates. For concretizing some concepts and sharing field experience, railway domain is selected, however the study is fully applicable to other domains due to deeming the norm IEC 61508 along the entire paper.

Safety requirements aim avoidance and control of systematic faults as well as control of random faults. For demonstrating that random faults are kept under the tolerable rates, quantitative hazard analyses are performed. Paramount importance shall be attached to the definition of tolerable hazard rates (THR) since the definition of what the hazard rate is allocated to influences the expected outcomes and the correct operation of the safety-critical system. In this paper, two approaches used in railway industry are discussed by mentioning technical specifications and referencing railway standards. It is found that there are misinterpretations for the quantitative hazard rates and use cases are provided to show the results of different approaches. Moreover, safety integrity level (SIL) of the human-machine interface (HMI) related functions for on-board and trackside applications are investigated, and their drawbacks are explained for the mission-critical systems. Finally, some findings of tool usage for fulfilling SIL requirements are detailed. Beside theoretical information, this paper includes field experiences gained during the development of safety-critical on-board and trackside interlocking (IXL) projects.

Typically, software development processes are time consuming, expensive, and rigorous, particularly for safety-critical applications. Even if guidelines and recommendations are defined by sector-specific functional safety standards, development process may not be completed because of excessive costs or insufficient planning. The V-model is one of the most well-known software development lifecycle model. In this study, the V-model lifecycle is modified by adding an intermediate step. The proposed modification is realized by checking the fault diagnosability of each module. The proposed modification provides three advantages: (1) it checks whether the constructed model covers all software requirements related with faults; (2) it decreases costs by early detection of modeling deficiencies before the coding and testing phases; and (3) it enables code simplicity in decision of fault occurrence.

Development of a Generic Application or Product (GAP) is always challenging, because it should be designed as much as generic and simply configurable for the final specific applications. If such a development is also safety critical, then the complexity increases dramatically as the resulted system will have impacts on human life, property and environment. The safety management plays a major role to keep this tough development process under control by avoiding systematic faults. Setting up correct organizational structure as well as applying Verification & Validation (V&V) concepts, which are two fundamental elements of safety management, in an accurate way are therefore crucial. This paper discusses railway safety management in terms of organizational structure and V&V with regards to the current normative status with its drawbacks. Proposals are provided for an updated organization and more harmonized V&V concepts including relations with safety management and quality assurance by sharing practical experiences.

Development of mission critical safety systems requires much effort as the resulted system will have impacts on the human life, property and environment. The design criteria such as data interchange between CPUs, synchronization, computation speed and diagnostic measures shall exhaustively be evaluated along with the effects of the parameters used in the reliability and safety calculations ex tunc. This study focuses on the average frequency of a dangerous failure of the safety function (PFHG). In comparison to formulas provided in IEC 61508, a comprehensive and innovative Markov model is proposed for diverse architecture, which helps to cover different safety relevant states to get quantitative results more correctly than provided in the standards and previous studies. The proposed model is applied to the vital computer to be used in the railway domain for CBTC metro and ERTMS ETCS systems and compared with the current models.

Bu çalışmada, ürünlerin dayanım ve performanslarının belirlenmesi için kullanılan hidrolik test sistemlerinin kontrolü için Model Öngörülü Kontrol (Model Predictive ControlMPC) tasarımı yapılmıştır Sistem kısıtlarının optimal kontrol kuralına dahil edilmesiyle test sistemi uygulamalarında karşılaşılan doyum problemleri için performans artımı sağlanması hedeflenmiştir. Bu amaçla, ilk olarak örnek sistem için sistemin doğrusal olmayan dinamik denklemleri oluşturulmuştur. Model çalışma noktası etrafında doğrusallaştırılarak, ivme durum değişkeni olacak şekilde durum uzayı modeli oluşturulmuştur. Elde edilen model, örnek sisteme ait model parametreleri kullanılarak, MPC içerisinde kullanılmak üzere ayrıklaştırılmıştır. MPC kuralı, yığın metodu (batch method) yardımı ile oluşturularak, kısıtlamalı optimal kontrol problemi arama algoritması yardımı ile çözülmüştür. Kontrol performansının tespiti amacı ile LQR ile karşılaştırmalı sayısal benzetim sonuçları sunulmuştur. Ayrıca sayısal benzetim testleri model belirsizliği ve ölçüm gürültüsü koşulları altında tekrarlanmış ve sonuçlar sunulmuştur. Elde edilen sonuçlar yorumlanmıştır ve gelecek çalışmalar için önerilerde bulunulmuştur. In this study, Model Predictive Control (MPC) is designed for the control of hydraulic test systems that are used for determining the strength and performance of the product. It is aimed to increase the performance of the saturation problems faced during the test system applications while including the system constraints in the optimal control rule. For this purpose, the nonlinear dynamic equations are first obtained for the considered test system. The state space model is obtained by linearizing the model around the equilibrium point in a way that the design variable is considered to be acceleration. The obtained model is discretized for employing it in MPC by using the model parameters of the considered system. MPC rule is solved via constituting batch approach method through constrained optimal control problem search algorithm. The simulation result of the comparisons with LQR is presented with the aim of examining the control performance. In addition, numerical simulations are repeated under parametric model uncertainty and measurement noise conditions and results are presented. The obtained results are discussed, and future studies are suggested.