computers in railways vii, c.a. brebbia j.allan, r.j. hill ... · it is a leading graphical...

Simulation study of moving automatic block

system based on MATRIXx® 6.0

Y. Zhang &X. WangAutomatic Research Institute of Transportation Science and Technology,Northern Jiaotong University, China

Abstract

Moving automatic block system is an advanced system for railway trafficcontrol, which is based on modern communication technology. It can not onlyensure traffic safety, but also greatly improve traffic efficiency. It can reduce theheadway to minimum by applying AI techniques to railway traffic control.However, as to the practical application of moving automatic block system,lacking of public acknowledgement is still a great concern, therefore, computersimulation is quite necessary to illustrate the characteristics of moving automaticblock system. This paper is an analysis of moving automatic block system bycomputer simulation based on a powerful simulation platform— MATRIXx® 6.0.Based on the models we have implemented, further study on various optimalalgorithms for train control can be easily carried out; furthermore, a morecomplicated train movement simulation system can be constructed to illustratethe advantages of moving automatic block system.

1 Introduction

Moving automatic block system is an advanced system for railway trafficcontrol, which is based on modern communication technology. It can not onlyensure traffic safety, but also greatly improve traffic efficiency. It can reduce theheadway to minimum by applying AI techniques to railway traffic control.However, as to the practical application of moving automatic block system,lacking of public acknowledgement is still a great concern. Therefore, computersimulation is quite necessary to illustrate the characteristics of moving automaticblock system.

Computers in Railways VII, C.A. Brebbia J.Allan, R.J. Hill, G. Sciutto & S. Sone (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-826-0

i i A £ Computers in Railways VII

Traditional simulations of train movement are based on general purposeprogramming languages, such as C, FORTRAN or special purpose simulationlanguages, such as SIMSCRJPT II. By these means, it is not convenient toobserve several outputs simultaneously during the simulation process. Additionalcode or special post-processing software is required to visualize the simulationdata. Furthermore, the simulation software is normally very complicated andcannot be constructed without the cooperation of several programmers. It isusually not so convenient for the duplication, debugging, transplanting of thecode.In this paper, a simulation model based on a powerful simulation platform—MATRIXx® 6.0 is constructed. MATRIXx® 6.0 is the latest version of MATRIXxfamily, which is an industrial application oriented product introduced byAmerican Integrated System Inc. It supplies a whole set of hardware andsoftware solution for the simulation of practical systems, making it easy for aseries of tasks, including system modeling, result validation, software code anddocument generation, design test and validation, as well as personnel training tobe finished in an integrated simulation environment.The paper is organized as following. Section 2 will give a brief introduction toMATRIXx® 6.0; section 3 is the mathematical models for train followingoperation under moving automatic block system; section 4 is the implementationof simulation model based on MATRIXx /SystemBuild; section 5 presents somesimulation results; section 6 draws some conclusions.

2 Brief introduction to MATRIXx® 6.0

MATRIXx consists of five parts, namely, SystemBuild, Xmath, Autocode,Documentlt and RealSim Series.SystemBuild is the core of MATRIXx family. It is a leading graphical modelingand simulation tool in industrial field, enabling the user to describe the system ingreat accuracy, design the simulation and test the simulation results in a singleintegrated environment. It supports the simulation of not only continuous,discrete and hybrid system, but also multi-rate system. Apart from a largepredefined functional module library, it also supports user defined libraries. Withthe support of interactive and non-interactive simulation capacity, the user canchange the simulation parameters, control the simulation process with great ease.SystemBuild also has good interfaces to many third party products.Xmath is an object-oriented analysis tool with powerful graphical ability. It notonly contains a rich basic function library for signal processing, mathematicalcomputation, but also supplies various special purpose function libraries, such asinteractive system identification module, interactive control system designmodule. Xmath works with SystemBuild seamlessly. The user can not onlymanage and display the simulation data in Xmath, but also use these two toolssimultaneously to speed his design.AutoCode can generate C or Ada code for a model established in SystemBuild in


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an efficient and accurate way according to the templates predefined by the user.Documentlt can generate documents for the model. It supports many kinds offormat, such as Microsoft Word, FrameMake and Interleaf markup language aswell as user defined format.RealSim Series is a fast prototype generation and real time simulation tool,enabling the user to test his design in the hardware-in-the-loop environment. Itcan automatically finish such work as code generation, hardware connection,application software downloading and linking of. The user can change rapidlyfrom digital simulation to hardware-in-the-loop simulation.With the help of MATRIXx, the development cycle of a product can be greatlyshortened. MATRIXx has been widely used in industrial field abroad. In recentyears, MARAIXx has been paid more and more attention at home. This paper isthe first attempt to apply MATRIXx in the simulation of railway traffic control.

3 M athmatical model for train movement

3.1 Model for single train movement

3.1.1 Forces acting upon a trainThere are three kinds of forces acting upon a moving train, namely, the tractionforce F, train movement resistance W (including the basic train runningresistance, the additional resistance caused by gradient, curves and tunnels, etc.)as well as train braking force B.When the locomotive is working in traction mode, the unit resultant force actingupon a train is,

- - J g— + /, (N/kN) 1

When in coasting mode, the unit resultant force is,

When in braking mode, the unit resultant force is,

-(W + B)"* - + 500̂ 0, +/. (N/kN) 3^ a ;l

where / ̂ F is the total traction force (N) 9^ i s the conversion braking

rate P is the total weight of the locomotives G is the train load g is the

acceleration of gravity; i • is the conversion gradient; w^ and WQ^ is the unit


Computers in Railways VII

basic running resistance of locomotive when operating in traction mode and

coasting mode respectively (N/kN) WQ is the unit running resistance of the

wagons (N/kN) WQ , w^ and WQ can be expressed as the function of train speed

, as shown in eqn (4) for an example,

w = # + 6v + cv^ (4)

where a, b and c are empirical coefficients, v is train speed.

<Ph is the conversion friction coefficient of the brake shoe, which can be

expressed as a nonlinear function of train speed, as shown in eqn (5) for an

example,

<p = Q.356 + 0.006(100 - v,) — — (5)* 14v + 100 ^ '6v + 100

where VQ is the initial speed for braking.

3.1.2 Train movement dynamicsIf regarding the train as a mass point, train movement equation can be expressed

as[l]

(6)

where a is the acceleration, and C is the unit resultant force.Hence, train speed and position can be obtained from eqn (7) and eqn (8)respectively,

(7)' = fat

s= \\adtdt (8)

3.2 Model for train following operation in sections under moving automaticblock system

Models for train following operation in sections under moving automatic blocksystem have been established in [2]. This paper focuses on how to implement themodel in MATRIXx/SystemBuild environment.Under automatic block system, the minimum headway distance between twotrains in succession is expressed as [2]

L"*=Lc+Lt+L?+le+Ls+Lr (9)


Computers in Railways VII i

where L^ is the distance traveled by a train during the information

transmission cycle t̂ L̂ is the distance traveled by train in the driver(or train

borne equipment ) reaction time ̂ L^ r e presents all kinds of errors, e.g. the

errors in speed/distance measurement L$ is the required safety protection

distance L^ is the train length.; L^ is the service braking distance wh ich is

expressed as [1]

3.6

where t^ is the idle running time. V^ and V^ is the initial and end speed in a

speed interval respectively.

4 Model implementation in MATRIXx/SystemBuild

Based on the mathematical models described above, a simulation model isimplemented in MATRIXx 6.0/SystemBuild environment as shown in figure 2.The model is constructed in a hierarchical way. In the uppermost level, there aretwo parts. The first part is the SystemBuild model of train following operation.The second part is the Altia Design 2.3 user interface. The details are describedbelow.

4.1 SystemBuild model of train following operation

The SystemBuild model of train following operation is shown in figure 3. It isassumed that three trains follow in succession in sections under movingautomatic block system. The first train is a freight train, the second and third arepassenger trains. This model is logically divided into two parts, namely, singletrain movement module (shown in figure 3 as First Train, Second Train, ThirdTrain) and train separation control module (shown in figure 3 as choose mode,choose model).


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Continuous SuperBlock Inputs Outputsfollows 0 12

Figure 2: Simulation model of train following operation

Continuous SuperBlock Inputs Outputsfollowing moddl 5 13

Figure 3: SystemBuild model for train following operation

4.1.1 Single train movement moduleThe role of this module is to simulate the movement of single train whoseSystemBuild model is shown in figure 4. It consists of 6 modules:(l)traction/braking force calculation module w hich calculates the traction or


Computers in Railways VII1151

Figure 4: SystemBuild model of single train operation

braking force according to the current operating mode (traction mode, brakingmode or coasting mode) and the traction level of the locomotive; (2)basicrunning resistance calculation module; (3Additional resistance(caused bygradient) calculation module, w hich calculate the gradient of the line accordingto the current position of the train, namely the equivalent gradientresistance (4)acceleration calculation module; (5)train speed calculationmodule; (6)train position calculation module.

4.1.2 Train separation control moduleThe role of this module is to control the operating mode of the locomotive of thefollowing train, according to the operating status of the preceding train, in orderto keep the separation between two trains to be longer than the minimumheadway. Its SystemBuild model is shown in Figure 5, which consists offollowing modules: (1) train braking distance calculation module; (2) trainseparation calculation module; (3) minimum headway calculation module, whichcalculates the minimum headway distance according to eqn(9); (4) locomotiveoperating mode control module, which change the operating mode of thelocomotive of the following train based on certain constraints. This module isrealized with a State Transition Block.


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4.2 Altia design user interface


Figure 5: SystemBuild model of train separation control module

Altia Design 2.3 is a software package for graphic and user interface design. Itworks with SystemBuild and RealSim series seamlessly. It contains an editor, arun time engine and a large ready made components library on the basis of whichthe user can rapidly generate an interactive interface for the simulation inSystemBuild. Furthermore, custom made components can be made by modifyingthe existing components. Because these characteristics, a designer can rapidlygenerate a user interface much look like the real product either in function orappearance.In this paper, an interactive simulation user interface has been designed withAltia Design 2.3, as shown in figure 6. Many kinds of information can bedisplayed, such as train speed, line gradient, simulation time. A group of buttonsis supplied for the user to start or stop any of the train during the simulationprocess. The operating mode and traction level of the first train can bemanipulated, in order to observe the reactions of the following trains. Of course,this is only a simple demonstration of the great power of Altia Design

Figure 6: Interactive user interface designed with Altia Design 2.3



5 Simulation results

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The simulation results for the above model is shown in Figure 7 and Figure 8.Figure 7 is generated automatically when the simulation process is terminated. Itshows the curves of position vs. time, speed vs. time, locomotive operating modevs. time, etc. Figure 8 is easily generated through programming with MathScriptlanguage under Xmath based on the simulation results. In figure 8, the first groupof curves shows the distance vs. time curves of three trains, the second groupshows the speed vs. time curves. The third group shows the contrast of actualtrain separation and the minimum headway distance of the first and second train;the fourth group shows the contrast of the actual train separation and theminimum headway distance of the second train and the third train. It can be seenthat the actual separation between two trains in succession is always longer thanthe minimum headway distance, showing that the control algorithm is valid forsecuring the safety of train following operation.

Figure 7: Simulation results


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1000 1500domain

1000500

Figure 8: Simulation results

6 Conclusion

MATRIXx 6.0 is a very powerful simulation platform. It can greatly shorten thedevelopment cycle of a product, reduce the programming work. Furthermore, itis very convenient for the cooperative development of a project. The hierarchicalmodeling power is also very charming. Based on the models we have developedin this paper, various train movement control algorithms can be furtherresearched, and more complicated and accurate models can be established.Currently, a train movement simulation system based on MATRIXx is underconstruction.

References

[1] Rao, Z. Train Performance Calculation C hina Railway Press, Beijing1997

[2] Wang, X. & Zhang, Y, Analysis of Block Carrying Capacity under MovingAutomatic block System, COMPRAIL'98, Lisbon, Portugal, Sept.Computers in Railways VI, pp.981-990,1998

[3] Zhang, Y. New Train Control System—Theoretical Analysis and ComputerSimulation of Line Capacity under Moving Automatic Block System, Ph.D.Dissertation, Northern Jiaotong University, 1998

[4] Integrated Systems. SystemBuild User's Guide. Sants Clara:IntegratedSystems. 1997


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