Research of MRM-based CTCS-3 Level Train Operation Control System Simulation Support Technology

ShangGuan Wei, Cai Bai-Gen, Wang Jian and Gou Chen-Xi State Key Laboratory of Rail Traffic Control and Safety, School of Electronic and Information Engineering

Beijing Jiaotong University Beijing, China

wshg@bjtu.edu.cn

Abstract—Train operation control system is one complex system with some feature like real-time and distributing, aim at different application purpose and operation process of system lifecycle, the emphasize point and level of detail is different. In this paper, MRM-based Simulation Support Technology and it’s application was studied, the modeling theory and method was studied systematically; the Aggregation-Disaggregation problem and settle method of MRM model run together in distributing simulation was studied, solving the couple consistency problem of MRM model; design the distributing and interactive simulation system structure base on HLA, the simulation support technology base on different level resolution was studied. Aim at practical demand of Chinese railway development, the modeling method base on MRM and modeling system structure aim at different simulation motivation was studied, the MRM modeling of key subsystem and parts of Train operation control system was studied, combine with practical work pattern of key parts, study the simulation of constructed model.

Keywords-Multiple Resolution Modeling, MRM; High Level Architecture; Simulation Support Technology; Distributing and Interactive Simulation; CTCS-3 Level Train Operation Control System

I. INTRODUCTION MRM (Multi-Resolution Modeling), one of the

worldwide hot spots in the field of Modeling and Simulation research since the 1990s, is one of the key technologies in distributing and interactive simulation of complex systems in future [1]. The concept of multi-resolution modeling is that, according to different purposes of modeling and simulation, we can use multi precision, multi-level modeling method to describe the various components of complex system, and all these multi-precision, multi-level can be defined as multi-resolution during system modeling [2-4].

MRM, originated in the United States Rand Corporation in the mid-1980s during the development of Rand Strategy Assessment System (RSAS), has been studied in the worldwide for more than twenty years. In 1992, an international conference of MRM is convened by the Defense Modeling and Simulation Office (DMSO) of United States Defense Advanced Research Projects Agency (DARPA) [5]. The United States National Science Research Council considered that MRM is one of the most fundamental challenges, which modern modeling and simulation technologies are facing. From the mid-1990s to the present, the hot spot of Multi-Resolution Modeling study is the combination of MRM, the High Level

Architecture (HLA) and Distributed Interactive Simulation (DIS) [6-8]. Martin Adelantado and other people, using Multi-Resolution Modeling techniques in an HLA-based open-space offensive and defensive simulation system, discussed the division method of the multi-resolution federal members and various Aggregation-Disaggregation problems and suggested to integrate Multi-Resolution Modeling function into RTI [9]. In application research, Gary Plotz and John Prince from the U.S. Air Force Laboratory achieved an interconnection between JMASS (Joint Modeling and Simulation System) and JWARS (Joint Warfare System) by using Multi-Resolution Modeling technique. Taylor combined Lanchester-equations-based combat analysis and simulation and entities-based tactical simulation both [10]. In the early 1980s, China started the study of the Multi-Resolution Modeling and set up a different resolutions model. LIU Bao-hong studied HLA-based Multi-Resolution Modeling framework design and application [11]. Current research focus on the point that, on the basis of the actual system needs of VV&A (Verification, Validation and Accreditation), the low-resolution optimization of the analytical simulation model can be used to test high-resolution optimization of the simulation model whether correct or not.

Train operation control system, the key point to guarantee the safety of high-speed railway and to improve the efficiency of transportation, is the "nerve center" of high-speed railway. The passenger-only lines with the speed of over 300 km/h and the Beijing-Shanghai high-speed railway under construction have already used CTCS-3 (China Train Control System) train operation control system, with high reliability and high safety, which mainly shows the vehicle speed signal, as a unified technology platform [12]. Because of the increasing complexity of problem and the expansion of simulation scale, according to different simulation needs, it is an inevitable trend in development of modeling and simulation technology of complex systems to set up the system model in different resolutions and to integrate the different models together organically for simulation studies[13]. For simulation of such complex system as train operation control system, the research should focus on Multi-Resolution Modeling in HLA-based distributed simulation supporting environments.

II. MULTI-RESOLUTION MODELING AND KEY PROBLEM

The most important thing of Multi-Resolution Modeling study is to set the resolution level for different

2009 Asia-Pacific Conference on Information Processing

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resolution model. CTCS-3 train control system is a large and complex system, which on the whole can be divided into three parts, which are ground equipment, on-board equipment and Train-ground communication. This method is mainly used to analyze the formation mechanism and formal process model of the Movement Authority (MA) at all levels of train operation control system, to study and build up the multi-resolution model of CTCS-3 sub-systems in view of multi-failure mode testing and basic performance evaluation and mainly to solve the Aggregation-Disaggregation in different resolution models and the coupling consistency problem during Multi-Resolution Model concurrent operation.

A. Aggregation-Disaggregation of Multi-Resolution Modeling Aggregation-Disaggregation is commonly used in

Multi-Resolution Modeling. Aggregation refers to process several related models on a certain abstractive level, resulting in lower resolution model set than the original one. Aggregation is a process, during which the high-resolution model changes into low-resolution one. Compared with the original model, the aggregation one has higher abstractive level, fewer entities, less information. Disaggregation is inverse process of aggregation, during which the low-resolution model changes into high-resolution one. One of the essential problems during modeling is to determine when to start Aggregation or Disaggregation.

The most important thing in CTCS-3 train operation control system are the communication between on-board equipment and Radio Block Center (RBC), the generation of traffic license and braking curve, as well as the safety of train operation, during the train traveling in the interval. Under different requirements and focus from different staff (such as decision-makers, researchers and designers) to the line, levels and details, the model is build up and discussed in three levels, which are the train safely driving view, the drawing of braking curve on DMI and check the position of the train by RBC. Fig. 1 is the typical design of MRM. Taking two-resolution-level as an example, it can be perceived at both Low-Resolution Level (LRL) and High-Resolution Level (HRL).

[ ]Hn

HHH H

XXXMRM 21= (1)

[ ]Ln

LLL L

XXXMRM 21= (2) To illustrate the simulation relation between MRMH

and MRML by describing low-resolution variables by high-resolution variables (3):

HL MRMKMRM ⋅= (3)

State

Entity property

1 ...2 ... ...nL ...

State

1 ...2 ... ...nH ...

MRMLRL HRL

Entity property

Figure 1. Typical Design of MRM

In accordance with the typical design of multi-resolution modeling, CTCS-3 train operation control system can be designed in three levels from low-resolution

to high-resolution, which are the train safely driving view, the dynamic drawing of braking curve on Driver Machine Interface (DMI) and train position check part by RBC. Fig. 2 (a) and (b) show the construction and information transmission process of Multi-Resolution Model. From the Figures, three different resolution levels are clearly seen and constitute as a whole through the information transmission.

Train position check by RBC

Braking curve made by VC according to MAView of train running

safely

High

to

low

MA made by RBC

Braking curve made

by VC according to

MA

Train running safely

according to braking curve

(a) Construction of Multi-Resolution Model (b) Information Transmission Process

Figure 2. Aggregation-Disaggregation of Multi-Resolution Model

B. Couple consistency problem during MRM model run together It is of great importance to maintain the consistency of

MRM, when models of different resolution run together. In this paper, it is suggested that, when models of different resolution run together, one homomorphism property can be maintained by only one model of certain resolution at anytime. From the view of MRM modeling, the properties of the models are divided into three parts, which are multi-resolution directly-related property, multi-resolution indirectly-related property and multi-resolution non-related property. Resolution related property could be divided into event-related property and non-determinism of event property. The classification of the property of MRM modeling is shown in Fig. 3.

Entity property

Non-related property

Directly-related property

Indirectly-related property

Event-related property

non-determinism of event property

Event-related property

non-determinism of event property Figure 3. Classification of the Property of MRM Modeling

In this paper, based on MRM model property, the consistency maintenance algorithm is: while (concurrent running model with different resolution){ when (one property s of model is changed without consistency maintenance){ if (s is the property with high-resolution){ if (s is resolution-related property){ if (s is resolution-directly-related property){ if (s is non-determinism of event property){ map the change of model property with high-resolution to

the change of model property with low-resolution;}

else if (s is event-related property){ map the change of model property with high-resolution to

the change of model property with low-resolution;

update the influenced resolution-indirectly-related property;}

} if (s is resolution-indirectly-related property) update property s and the effect caused by property s to

resolution-directly-related property; }

} if (s is the property with low-resolution){ if (s is resolution-directly-related property and also is event-

related property){ map the change of model property with low-resolution to the

change of model property with high-resolution; update the influenced resolution-indirectly-related property;} if (s resolution-indirectly-related property)

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update property s and the effect caused by property s to resolution-directly-related property;

} Label the property as updated and the consistency maintenance as completed, to prevent updating again;

} }

III. CONSTRUCTION OF SIMULATION ENVIRONMENT FOR MRM

A. Simulation technology for MRM The realization of MRM depends on the construction

of simulation environment. HLA-based simulation technology for MRM is studied on the base of analysis of different resolution grades of models. RTI (Run-Time Infrastructure) helps to build up the simulation environment and to study the federal membership model with different resolution grade and the relationship between data management and information interaction in simulation.

RTI is required as a base to study the simulation technology for MRM, because RTI could help to realize MRM structure, as shown in Fig. 4 (a). To realize the interaction as reception and sending and data process in MRMR-FOM based on HLA, user only needs to realize some standard virtual function specific-model-related and uses the function to complete the model-related multi-resolution process, as shown in Fig. 4 (b).

Simulation member

Member design framework

Extended functions

MRM MMM ... ... OM

Basic functions of RTI

FM AM OM TM PM DDM

Net protocol at base layer

MRMR-FOM

FOM in simulation

RTI

HLA-based MRM framework

program

Call MRM

Call-back relevant

functions

Call RTI

RTI call-back

(a) MRM Model Structure (b) HLA-Based MRM Model Structure

Figure 4. HLA-Based MRM Model Structure

B. Selection in simulation environment RTI, the kind of software realized in accordance with

the HLA interface specification, is the core of HLA software, which the simulation field of the world pays attention to. DMSO and MAK from the United States have already developed RTI for specific purpose, while JAVA-based pRTI and RIT-related toolkit are developed by Pitch from Sweden. StarLink, based on StarBus of CORBA (Common Object Requesting Broker Architecture) with independent intellectual property, is the first RTI software, with multi-thread technology (no need to call tick), in accordance with IEEE1516 in our country. With the character of high efficiency, full-function, learn and use easy, StarLink has good cross platform ability, which could serve general PC, workstation, server and even high-performance computer as the Galaxy, and could realize the interconnection, interworking and interoperability in different hardware and software platforms[14].

The typical RTI software adopts the function distributed structure, while StarLink-H adopts a “layered architecture”, as shown in Fig. 5. From the view of low-

resolution model, the on-board equipment in train control system, RBC and train control centers are considered as member during information exchange. And from high-resolution model, every unit from on-board equipment, including information receiving unit of track circuit, DMI, train interface unit and so on, could be considered as a federal member for information exchanged, which means that, at certain circumstances, a LRTI server is able to manage several federal members, that is why it is necessary to adopt RTI with layered architecture.

CRC

LRCmember

CRTI

LRTI LRTI

m1 m2 m3 m4LRC

member

(a) Function Distributed Mode (b) Layered Mode

Figure 5. RTI Structure

C. Division of the federal member in simulation environment When talk about division of member, several factors

should be considered, such as domain knowledge, granularity of simulation and complexity of model, network information flow, reusability of model and so on. As shown in Fig. 6, the member is divided into three modes [15]: centralized, fully distributed and partially distributed.

member

HR object

LR object

Smaple:

centralized Fully-distributed

Partially distributed

Figure 6. Division of members

To divide the members in fully distributed mode in model listed above, it is clear that RBC, VC and train safely operation view are three members, among which information exchange take RTI as a platform. In order to make simulation expansion in future, it is necessary to add one member as a federal manager, who can manage all the members. The federal management is mainly for showing how many members are in the federal and listing basic information of every member, which bring a lot convenience to model expansion and system improvement.

D. Realization of federal simulation In order to view simulation result directly and easily,

considering less model members, we could put all these members into a federal and simulate on a machine. The federal simulation structure is shown in Fig. 7. Each member will announce specific property to RTI and order required property from RTI, which means every member takes RTI as the media to complete required information exchange and to realize specific function. According to different application purpose, the layer calling for division, the resolution calling for considering, and the members, will become more and more, so the property ordered and announced by members will be more and more. Then

420

appear the advantages of MRM, as reusability and interoperability.

RTIOrder train

position

anounceM A

N oannounce

Order train position

and speed

O n-board

A nnounce train position,

brak ing curve, etc.

O rder M A

Federal m anage

m entTrain center

view

Figure 7. Federal Simulation Structures

RTI manage all the execution made by federal. According to member requirements, RTI complete all the federal-relevant operation, as member add-in, member quit, object register and object delete.

IV. MRM-BASED SIMULATION AND RELIZATION Base on MRM and simulation environment, design the

federal membership in the simulation system, every member could do such operation as to connect RTI or to quit federal manually. Several federal members are built up in simulation to realize that, the train runs safely according to braking curve. As shown in Fig. 8, the train is running safely according to the braking curve, calculated by the computer.

(a) station sketch map (b)MMI

(c) train runs safely according to braking curve (d)train inside situation

Figure 8. View of Train Running Safely

V. CONCLUSION In this paper, the basic theory and solution to some key

problems of MRM is studied systematically. Based on deeply comprehension of working principle and function of train operation control system, combined with MRM-based simulation technology, the component and subsystem of the system is described from one layer to another by MRM, according to different focus and

requirements to the system and details by different staff (as decision-maker, researcher and designer). During the establishment of large-scale simulation and application system, MRM brings a lot help to people to understand and to study the system. To start MRM-relevant research has important significance to improve the availability, reusability and interoperability of simulation. Whether the work in this paper is accurate or not determine the reliability and continuation of system simulation. Obviously, analysis on MRM is of great importance in system modeling and simulation.

ACKNOWLEDGMENT This research work was supported by National Natural

Science Foundation of China (No.60736047, No.60870016), Science and Technology Fund of BJTU (No.2008RC023) and National High Technology Research and Development Program of China (No.2007AA11Z214).

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