A computer algebra approach to the design of routes and the study of their compatibility in a railway interlocking

A railway interlocking is a device that supervises train operation (signaling and position of switches) authorization and prevents conflicting actions from being authorized. An expert system for route selection in a railway interlocking is presented, that is independent of the station topology. It is Maple-based and uses lists (it performs a kind of adapted knowledge extraction and verification). Given the track arrangement, it can determine all routes that begin in a given section and all routes that are an extension of a given route (in both cases it is possible to ask what routes end at a given section). Routes can be classified according to number of sections and, given a time estimate for crossing each section, timing for each route can be calculated. Therefore, the program makes it possible to optimize the route according to different criteria. Moreover, thanks to the chosen data structure, decision making on the compatibility of a proposed route is straightforward.     

基于仿真数据的列车运动模型辨识

提出一种基于地铁列车的运行仿真数据来辨识列车传递函数的新思路。通过对列车运动模型的分析建立列车运行仿真中涉及到的多质点受力模型,用于计算不同车型混编的地铁列车的受力情况。以该受力模型为基础对列车的运行情况进行仿真实现,基于仿真软件生成的牵引力和速度随时间变化的数据,通过最小二乘法辨识出列车的传递函数。实验结果表明,辨识出的列车运动模型是有效的。     

A fuzzy Petri net model to estimate train delays

Even with the most accurate timetable, trains often operate with delays. The running and waiting times for trains can increase unexpectedly, creating primary delays that cause knock-on delays and delays for other trains. The accurate estimation of train delays is important for creating timetables, dispatching trains, and planning infrastructures. In this work, we proposed a fuzzy Petri net (FPN) model for estimating train delays. The FPN model with characteristics of hierarchy, colour, time, and fuzzy reasoning was used to simulate traffic processes and train movements in a railway system. The trains were coloured tokens, the track sections were termed places, and discrete events of train movement were termed transitions. The train primary delays were simulated by a fuzzy Petri net module in the model. The fuzzy logic system was incorporated in the FPN module in two ways. First, when there were no historical data on train delays, expert knowledge was used to define fuzzy sets and rules, transforming the expertise into a model to calculate train delays. Second, a model based on the Adaptive Network Fuzzy Inference System (ANFIS) was used for systems where the historical data on train delays were available (from detection systems or from the train dispatcher’s logs). The delay data were used to train the neuro-fuzzy ANFIS model. After the results of the fuzzy logic system were verified, the ANFIS model was replicated by a fuzzy Petri net. The simulation was validated by animating the train movement and plotting the time-distance graph of the trains. Results of the simulation were exported to a database for additional data mining and comparative analysis. The FPN model was tested on a part of the Belgrade railway node.     

Exact train pathing

Suppose we are given a schedule of train movements over a rail network into which a new train is to be included. The origin and the destination are specified for the new train; it is required that a schedule (including the path) be determined for it so as to minimize the time taken without affecting the schedules for the old trains. In the standard formulations of this single train pathing problem, the time taken by the train to traverse any block (track segment guarded by a signal) in the network is deemed to be a fixed number, independent of how the train arrived onto that block. In other words, the standard formulations of train pathing do not accurately model the acceleration/deceleration restrictions on trains. In this paper we give an algorithm to solve the single train pathing problem, while taking into account the maximum allowed acceleration and deceleration as well as explicitly modeling signals. For trains having ‘large’ maximum acceleration and deceleration, our algorithm runs in polynomial time. On the other hand, if the train to be pathed is capable of only very small acceleration so that it must take a long time to reach full speed, our algorithm takes exponential time. However, we prove that the pathing problem is NP-complete for small acceleration values, thus justifying the time required by our algorithm. Our algorithm can be used as a subroutine in a heuristic for multiple train pathing. If all trains have large (but possibly different) accelerations this algorithm will run in polynomial time. V. Nagarajan is supported in part by NSF grant CCF-0728841.     

High-Speed Trains Automatic Operation with Protection Constraints: A Resilient Nonlinear Gain-based Feedback Control Approach

This paper addresses the control design for automatic train operation of high-speed trains with protection constraints. A new resilient nonlinear gain-based feedback control approach is proposed, which is capable of guaranteeing, under some proper non-restrictive initial conditions, the protection constraints control raised by the distance-to-go (moving authority) curve and automatic train protection in practice. A new hyperbolic tangent function-based model is presented to mimic the whole operation process of high-speed trains. The proposed feedback control methods are easily implementable and computationally inexpensive because the presence of only two feedback gains guarantee satisfactory tracking performance and closed-loop stability, no adaptations of unknown parameters, function approximation of unknown nonlinearities, and attenuation of external disturbances in the proposed control strategies. Finally, rigorous proofs and comparative simulation results are given to demonstrate the effectiveness of the proposed approaches.      

Design of rocker switches for work-vehicles--an application of Kansei Engineering

Rocker switches used in vehicles meet high demands partly due to the increased focus on customer satisfaction. Previous studies focused on ergonomics and usability rather than design for emotions and affection. The aim of this study was to determine how and to what extent engineering properties influence the perception of rocker switches. Secondary aims were to compare two types of rating scales and to determine consistency over time of the ratings. As a method Kansei Engineering was used, describing a product domain from a physical and semantic point of view. A model was built and validated, and recommendations for new designs were given. It was seen that the subjective impressions of robustness, precision and design are strongly influenced by the zero position, the contact position, the form-ratio, shape and the surface of rocker switches. A 7-point scale was found suitable. The Kansei ratings were consistent over time.     

Estimating collision probabilities for trains on railroad stations based on a Poisson model

We consider the problem of estimating the probability of collision between shunting trains and passenger trains on a railroad station. We assume that the flow of shunting trains is Poisson for every turnout switch on which side collisions are possible. The data for computations include the station’s topology, timetable of passenger trains, and possible routes of their passing through the station together with the intensities of shunting trains moving through nonisolated turnout switches where collisions are possible, and also mean values of train lengths and their velocities. The proposed mathematical model of train motion can be regarded as a first approximation in modeling the collision process for trains on a railroad station. We also consider a real life example.     

改进的最小割集生成算法与联锁系统模型的安全性测试*

为保证铁路联锁模型的安全性,在故障分析法的基础上提出一种新的用Petri网来建立故障树的方法,动态地描述铁路联锁系统的安全性需求,并根据Petri网安全需求模型的可达标志图,提出一种能自动生成最小割集的算法。根据算法生成的最小割集,设计了一个联锁安全检测器,用于检测和控制联锁系统模型处于安全状态。最后用CPN工具对所建立的联锁系统模型进行仿真,仿真结果表明联锁安全检测器能够保证模型的安全性。     

Hardware-Efficient and Highly Reconfigurable 4- and 2-Track Fault-Tolerant Designs for Mesh-Connected Arrays

We consider m-track models for constructing fault-tolerant (FT) mesh systems which have one primary and m spare tracks per row and column, switches at the intersection of these tracks, and spare processors at the boundaries. A faulty system is reconfigured by finding for each fault u a reconfiguration path from the fault to a spare in which, starting from the fault u, a processor is replaced or “covered” by the nearest “available” succeeding processor on the path—a processor on the path is not available if it is faulty or is used as a “cover” on some other reconfiguration path. In previous work, a 1-track design that can support any set of node-disjoint straight reconfiguration paths, and a more reliable 3-track design that can support any set of node-disjoint rectilinear reconfiguration paths have been proposed. In this research note, we present: (1) A fundamental result regarding the universality of simple “one-to-one switches” in m-track 2-D mesh designs in terms of their reconfigurabilities. (2) A 4-track mesh design that can support any set of edge-disjoint (a much less restrictive criterion than node-disjointness) rectilinear reconfiguration paths, and that has 34% less switching overhead and significantly higher, actually close-to-optimal, reconfigurability compared to the previously proposed 3-track design. (3) A new 2-track design derived from the above 4-track design that we show can support the same set of reconfiguration paths as the previous 3-track design but with 33% less wiring overhead. (4) Results on the deterministic fault tolerance capabilities (the number of faults guaranteed reconfigurable) of our 4- and 2-track designs, and the previously proposed 1- and 3-track designs.     

Parameter estimation of permanent magnet stepper motors without mechanical sensors

The paper presents a new sensorless parameter identification method for permanent magnet stepper motors. Current sensors are assumed available, but mechanical sensors are not. Data is obtained with open-loop commands at multiple speeds. A new frame is proposed that presents advantages similar to the d–q frame, but without the need for a position sensor. The method exploits derived linear parameterizations and least-squares algorithms. In some cases, overparameterization is resolved using elimination theory. The parameters identified using the new procedure are found to be very close to those obtained with sensors. The approach is potentially applicable to other types of synchronous motors.     

An output queueing analysis of multipath ATM switches

The performance of output buffers in multipath ATM switches is closely related to the output traffic distribution, which characterizes the packet arrival rate at each output link connected to the output buffer of a given output port. Many multipath switches produce nonuniform output traffic distributions even if the input traffic patterns are uniform. Focusing on the nonuniform output traffic distribution, we analyze the output buffer performances of several multipath switches under both uniform and nonuniform input traffic patterns. It is shown that the output traffic distributions are different for the various multipath switches and the output buffer performance measured in terms of packet loss probability and mean waiting time improves as the nonuniformity of the output traffic distribution becomes higher.     

A graph theory-based approach to route location in railway interlocking

The location and verification of routes is an important component of railway interlocking logic design. The interlocking routes are typically listed manually by experienced signaling engineers, and this task is both time consuming and expensive. In this paper, an automatic, graph theory-based approach to route location and verification is presented. In this new approach, a component-based model is used to represent the topology of the station layout, and a modified matrix algorithm based on graph theory is used to locate all of the routes in a given station. This algorithm exhibits superior performance in the location and verification of routes and is universally applicable, irrespective of the station layout. When a station is modified, the designers can simply update the topological data for the station, and the new route information can be obtained automatically.     

A method for online pattern recognition of abnormal eye movements

A doctor could say that a patient is sick while he/she is healthy or could say that the patient is healthy while he/she is sick, by mistake. So it is important to generate a system that can give a good diagnosis, in this case for abnormal eye movements. An abnormal eye movement is when the patient wants to move the eye to up or down and the eye does not move or the eye moves to other place. In this paper, a method for the pattern recognition is used to provide a better diagnosis for patients related with the abnormal eye movements. The real data of signals of two eye movements (up and down) of patients are obtained using a mindset ms-100 system. A new method that uses one intelligent algorithm for online pattern recognition is proposed. The difference between the proposed method and the previous works is that, in other works, both behaviors (up and down) are trained with one intelligent algorithm, while in this work, up behavior is trained with one intelligent algorithm and down behavior is trained with other intelligent algorithm; it is because the multi-output system can always be decomposed into a collection of single-output systems with the advantage to use different parameters for each one if necessary. The intelligent algorithm used by the proposed method could be any of the following: the adaline network denoted as AN, the multilayer neural network denoted as NN, or the Sugeno fuzzy inference system denoted as SF. So the comparison results of the proposed method using each of the intelligent algorithms for online pattern recognition of two eye movements are presented.     

The Merlin-Randell problem of train journeys

Summary The following synchronization problem is studied: There is a finite set of trains, a finite set of stations, and the engine house. Each station can hold only one train. Each train has a route to follow starting and ending at the engine house. The route may be repeated one or more times. A train may leave a station (or the engine house) only when its immediate destination is an empty station or the engine house. At the beginning all trains are placed at the engine house. The problem is to find a synchronization among train movements which allows parallel movements of trains where possible and enables the completion of each train journey.A formal model of the train system is proposed assuming that each train route is deterministic and contains no repeated stations. The model is based on the notion of a movement graph being a labeled directed multigraph, the nodes of which represent stations, the arcs of which represent possible train movements. The solution proposed is based on a characterization of inadmissible situations by means of some subgraphs of the movement graph. The properties of these subgraphs, called minimal critical patterns, are investigated. Optimal and suboptimal synchronization strategies are defined. A specification of the optimal strategy in the basic COSY notation is included, and its correctness is demonstrated.The research reported in this paper was partly supported by a Grant from the Science and Engineering Research Council of Great BritainOn leave from the Institute of Mathematics, Warsaw Technical University, 00-661 Warszawa, Poland     

基于灰色遗传的高速列车速度控制器模型研究

速度控制器是列车自动驾驶系统(ATO)的核心,针对目前尚无研发成熟的速度控制器应用于高速列车的情况,引入灰色系统理论研究高速列车速度控制器模型;在灰色遗传预测模块中,对影响模型精度的λ值提出了基于遗传算法的求解方法,根据列车运行的4个目标设计其适应度函数,并加入先验知识判定对约束条件进行处理,同时建立新陈代谢GM(1,1)模型,在列车运行过程中不断求解新的模型参数a和b,实现模型在线校正,使系统可以进行长期预测;在灰色决策模块中,将高速列车的工况及运行目标转化为决策要素,应用灰靶决策产生最优策略控制列车运行;仿真结果显示了该模型应用于列车自动控速时的有效性和实时性,并使各项运行指标都有所提高。     

轨道交通虚坡模型中的二重迭代法

人们对于轨道交通的计算机仿真问题进行了较多的研究,但尚存不足之处.为此,提出了一种用于轨道交通仿真的虚坡模型.其中,列车的速度由局部环境决定,即通过所考虑列车的前方列车号、它到前方列车的距离、对应位置上的虚坡宽度以及车和前方列车的最大速度等因素确定.进而在此模型的计算中提出了一种二重迭代法.其中第一重迭代用于确定列车的新的前方列车和分水岭时刻,第二重迭代用于克服时间步末位置和速度的耦合关系.车站对于将进站停靠列车的减速作用由一个假想静止列车模拟.对实例进行了计算,结果表明上述模型是有效的.它可被用于计算列车运行图和时刻表.     

Strong unforgeability in group signature schemes

A signature scheme is strongly unforgeable if no adversary can produce a new valid signature σ on a message M even after seeing some signatures on M. We define strong unforgeability of group signature schemes and explain why the strong unforgeability of a group signature scheme is necessary. This relatively new security concept was not considered when Bellare–Micciancio–Warinschi established their security model, what we call the BMW security model, of group signature schemes. We show that a scheme proposed at Eurocrypt'06 that was proven secure in the BMW security model is not strongly unforgeable. We also present a method to convert this scheme into a strongly unforgeable group signature scheme preserving the security in the BMW security model.     

Automated platforming & routing of trains in all Belgian railway stations

Automatically generating train to platform assignments has been an active research area for some time, but systems implementing this research are still not readily available to practitioners. However, now, our train platforming model has been implemented as the tool Leopard inside Infrabel, the Belgian railway infrastructure manager. In practice, initial macroscopic timetables are often not yet feasible inside stations on the microscopic level. This means that a platforming tool must be able to handle cases where not all trains can be platformed or routed. Our model provides a platforming and routing plan for as many trains as possible and puts the remaining trains on a fictive platform. Contrary to the manually made platforming plans, the optimised platforming plans have no platform conflicts nor routing conflicts. Our model assigns as much trains as possible, given the timetable and the available infrastructure. Our tool can solve the platforming problems for all 530 stations in Belgium together in about 10 min. This means (i) it saves many man months of planning time compared to the still common manual practice to platforming and (ii) it achieves higher quality results leading to significantly less in-station train delays in practice.     

考虑倒垛因素的轧制计划编制方法

在给定粗轧制计划的基础上考虑钢坯库倒垛优化, 编制详细的轧制计划; 建立以最小化轧制计划内钢坯出 库总倒垛次数与轧制单元之间切换机架次数为目标的多目标整数规划模型; 针对模型特征, 设计一种基于钢坯匹配的单亲遗传算法. 通过基于实际生产数据的实验验证, 相对于传统的手工计算方法, 所提出的算法在优化倒垛次数和切换机架次数上平均提升20 %, 算法和模型是可行且有效的.     

Sensor/actuator faults detection for networked control systems via predictive control

Quantized fault detection for sensor/actuator faults of networked control systems (NCSs) with time delays both in the sensor-to-controller channel and controller-to-actuator channel is concerned in this paper. A fault model is set up based on the possible cases of sensor/actuator faults. Then, the model predictive control is used to compensate the time delay. When the sensors and actuators are healthy, an H ∞ stability criterion of the state predictive observer is obtained in terms of linear matrix inequality. A new threshold computational method that conforms to the actual situation is proposed. Then, the thresholds of the false alarm rate (FAR) and miss detection rate (MDR) are presented by using our proposed method, which are also compared with the ones given in the existing literatures. Finally, some numerical simulations are shown to demonstrate the effectiveness of the proposed method.