UML-based urban rail train overspeed protection system modeling

This paper analyzes the main features of Rhapsody software of I-Logix and uses UML to model the ATP system on-board equipment of Beijing Metro Line 1 in the Rhapsody development environment. It also introduces the system-level debugging function.

Abstract: This paper analyzes the main features of Rhapsody software of I-Logix in UML modeling of the ATP system on-board equipment of Beijing Metro Line 1 in the Rhapsody development environment, and introduces the system-level debugging function.

Unified Modeling Language UML (UnifiedModelingLanguage) is by far the best unified object-oriented modeling language. it replaces various previous object-oriented representations and can comprehensively and meticulously describe business and software systems at the same time, seamless and unified full-lifecycle modeling for software development. The combination of UML and OOAD (Object-Oriented Analysis and Design) tools makes the realization of software engineering idea a huge step forward.

Rhapsody of American I-Logix is an integrated visual environment based on UML2.0 for embedded application development. It provides a four-way support platform for embedded software development, visualization, engineering, automation, and team-based. Rhapsody is rapidly becoming the preferred MDD (model-driven development, ModelDrivenDevelopment) development environment in the defense/aerospace field, in a series of projects (such as FutureCombatSystems (FCS) andF22) used as the main development tool.

The automatic train protection system (ATP) is an integral part of the urban rail transit operation control system. It mainly ensures that the speed limit information is provided to maintain the safety interval between trains, so that the trains can run at the specified speed. As an important part of the automatic train protection system, the ATP vehicle equipment is responsible for completing the functions of the ATP vehicle part. The LCF100DT vehicle-mounted device used by Beijing Metro Line 1 is a vehicle safety control device dedicated to subway signal technology to ensure train operation safety and improve transport capability. This article first introduces the main feature of Rhapsody-real-time framework, and then analyzes the working principle of the ATP system, based on Rhapsody, the software system of the ATP system on-board equipment of Beijing Metro Line 1 is modeled. Finally, the system-level debugging function is analyzed.

1. Rhapsody framework features

The real-time framework of Rhapsody is a vertical framework with specially selected and optimized design templates for embedded and real-time applications. it implements internal processing (such as the implementation of state machines and containers) code rewriting. the real-time framework makes the design model irrelevant to the operating system. through the real-time framework, applications can be easily transplanted from a real-time operating system to other operating systems.

The real-time framework consists of four main parts, as shown in 1. The object execution framework provides the basic structure of UML model execution to manage the execution of thread state machines. The Association mode between objects manages one-to-many and many-to-many relationships between objects, the abstract operating system has nothing to do with the framework itself and the real-time operating system, which facilitates the porting of animations to the framework. the debugging framework allows users to perform model-based debugging, for example, breakpoint settings based on the status chart and message ing between capturing different objects. The main elements in the object execution framework are analyzed below.

2. automatic overspeed protection system

2.1 Overview of automatic overspeed protection system

ATP (automatic train protection system) provides over-speed protection, zero-speed detection, and door restriction functions to maintain the safety interval between trains, enables the train to run at a specified speed. The vehicle-mounted equipment for overspeed protection is an important part of the train overspeed protection system. it is based on the train operation control commands received from the ATP ground equipment, A security equipment that monitors the real-time speed of trains.

2.2 Beijing Metro Line 1 ATP system

The devices required for the implementation of the ATP subsystem include ground devices and vehicle-mounted devices. The ground equipment is mainly composed of a centralized ground track circuit FS2500 non-insulated track circuit, which consists of a transmitter, receiver, code generator and a tuning unit. its code sending is controlled by a microcomputer interlocking device and a control center, to ensure security tracking interval and temporary speed limit. The functions of the vehicle-mounted devices are completed by the ground information receiving part, speed measuring part, and speed comparison control part. when the train speed exceeds the permitted speed, the deceleration control is automatically completed, the on-board device consists of a microprocessor-based safety subsystem and a non-safety subsystem, a speedometer, an antenna, and a speed motor mounted on different shafts.

The function of the ATP system includes: when the block partition is set, the minimum safety interval during train tracking is ensured to prevent train tail tracking accidents. The train operates at the maximum allowable safe speed of the line, prevents trains from speeding up; ensures proper and safe routes; ensures that doors are properly opened and closed; and provides temporary speed limits.

2.3 Use software Rhapsody to model ATP (on-board equipment)

In order to ensure high reliability and maintainability of system software, structuring and modularization are the key to system software design. the division of software modules should be as clear and relatively independent as possible, the entry and exit parameters have clear meanings. The software Rhapsody only supports the English environment.

2.3.1 requirement analysis

Demand Analysis is to clarify the functions required by the train operation control simulation system from the perspective of peripheral systems. In the past demand analysis, there was never a proper tool to ensure the complete expression of system requirements, which directly led to the inconsistency found in the detection after the system was completed.

In the analysis phase, the Rhapsody, an effective formal tool that fully supports UML, is introduced to express the above functional requirements in a complete and unambiguous language, reducing the understanding deviation of designers, simplified communication during development.

This example graph shows the relationship between objects and use cases. The driver determines whether to perform ATP operations. Once the ATP overspeed protection system is enabled, the ATPdevice (ATP in-vehicle device) is in the overspeed protection status and receives the target speed and real-time running speed, if the driver operates the train at the permitted speed, the speed monitoring equipment does not interfere with the normal operation of the driver. When the driver violates regulations or the train operation exceeds the permitted speed, the ATP vehicle-mounted device will automatically implement braking. The on-board devices mainly implement the following functions: initialtrain (self-check and initialization of on-board devices), acquireactualspeed (get the actual speed), and acquireactualspeed (get the real-time speed of the train operation ), acquirelmiitedspeed (get the permitted speed, that is, the train speed of the entrance section), acquiregoalspeed (get the target speed of the exit section), and protectspeed (speed protection and supervision for train operation ), announceemergency (speeding alarm), braketrain (when the train is found to exceed the permitted speed, forced braking of the train), the driver's function is: brakebyhuman (manual braking) and activitateATP (selection of the mode switch and collection of the status of the control switch ).

2.3.2 Classification and processing of classes

It is determined by functional requirement analysis. by using the object-oriented design idea, each part is described with an object, and the object with certain attributes and operations is clustered into a class. Logically, an object is an independent module. from the outside, you only need to know what functions it has and how to implement these functions is blocked from the outside world. Objects in the system are dynamically linked through the message activation mechanism, and the inheritance of classes in object-oriented modeling can be used to simplify the generation of classes and objects. If different classes have common attributes and methods, these common attributes are summarized as general classes according to the class hierarchy.

Object model diagram of this system.

The exit Inspection method used by Beijing Metro Line 1 is the hierarchical speed control method. in a block partition, only one allowed speed is used to determine whether the train is speeding, in addition, the driver is required to reduce the train running speed to the target speed in the blocked partition. the device checks the train running speed at the exit of the blocked partition. this process is mainly achieved through the ProtectSpee (protection speed) class. The allowable speed of the train is the entrance speed of the section. the locomotive signal display shows the target speed. The target speed of this section is the allowable speed of the next block partition. the acquisition of various speeds is achieved in SignalConditionIn (signal input), and DriverCommand (driving Command) is also set up) and BrakeControlle (brake control) to start the train brake operation of ATP. The functions and events of each class are not described in detail here.

2.3.3 status chart analysis

The UML programming process is defined in the state diagram. because the expression and scalability of the state diagram are good, UML uses them as the formal FSM (finite state machine) representation. A finite state machine is defined by a finite set of existing conditions (known as "states"). It is also a finite set of state transfer triggered by transactions between states. The behavior in this case is defined by the status and conversion relationships of various classes. in order to make the status chart not more complicated and more accurate, we will assign the status chart to each class. Here, we will discuss the main category-ProtectSpeed (protection speed class) (see), including CompareSpeed (train speed in the protection section is controlled below permitted speed) getdownActualSpeed (to ensure that the speed of the train at the exit of the section is reduced to the target speed) and RefreshActualSpeed (to continuously get the actual running speed of the train ).

For example, in RefreshActualSpeed (refresh Speed), you need to obtain the processed numeric Speed. in this status, add Actual-Speed = SignalConditionerIn-> GetActualSpeed (), in this way, the actual train running speed can be obtained from SignalConditionIn (signal input.

In the CompareSpeed (speed comparison), compare the actual speed with the maximum allowed speed. if the braking status changes beyond the rule, the status chart enters the BrakeController status chart.

2.4 code generation and system-level debugging

When the above design is complete, we can generate code and test the system model. We need to use the Component to tell the Rhapsody environment. We usually use a Microsoft environment (Windows operating system and Visual C ++ compiler), so that Rhapsody can generate Visual C ++ 6.0 and VxWorks-based C ++ programs.

Rhapsody promotes modeling-level debugging through the dynamic state diagram and sequence diagram. You can debug an application in one step on an "object-oriented" scale (Operation call, single event processing, and entire event queue, observe the influence of the status chart (for example, the change of the activity chart ). Rhapsody provides three different levels of animation control commands (add settings in conf iguration ). 1st types are none, that is, the code to be generated can be released; 2nd types are tracing, which can display the execution trace information of text on the standard output device of the host as the execution process occurs, the 3rd layers are anmiation (graphic animation), which is presented in an animated form.

When the Rhapsody code runs on the target machine, the running status is dynamically fed back to the design model. for example, breakpoint settings based on the status chart and message ing between different objects are captured on the sequence chart. Joint debugging with the code-level debugging tool while performing design-level debugging. Through model-level/code-level joint debugging and verification, Rhapsody can intuitively detect system design errors or defects as early as possible, so as to identify or reduce project risks earlier.

In addition, Rhapsody can generate high-quality Chinese documents and generate the framework structure, runtime library, compilation file, communication mode, and implementation strategy required by the software application. Furthermore, the consistency of the model and code ensures the consistency of the document and code, and provides a good platform for us to smoothly complete development and accumulate later experience. You can customize templates to generate documents suitable for specific work requirements.

3 Conclusion

By modeling UML of Beijing Metro Line 1, the development cycle of vehicle-mounted equipment and software can be shortened. In this paper, the LCF-100DT-type vehicle-mounted equipment of Beijing Metro Line 1 is modeled by UML, and the development environment of Rhapsody based on UML language is used, it also facilitates the use of CASE tools to automatically generate code, greatly improving the development efficiency and project manageability of vehicle-mounted device software. Rhapsody uses model-based development to provide a clear structure and reusable software modules for system development, which can effectively improve the efficiency and maintainability of real-time software development, it can also be debugged at the system level to improve system reliability and timeliness. Rhapsody provides a complete application software for complex real-time embedded systems, from analysis, design to code implementation and software testing.