自動控制畢業(yè)論文中英文資料外文翻譯文獻

1、 畢業(yè)論文外文譯文學(xué) 院 自動化與電氣工程學(xué)院 專 業(yè) 自動控制 Component-based Safety Computer of Railway Signal Interlocking System1 IntroductionSignal Interlocking System is the critical equipment which can guarantee traffic safety and enhance operational efficiency in railway transportation. For a long time, the core control

2、computer adopts in interlocking system is the special customized high-grade safety computer, for example, the SIMIS of Siemens, the EI32 of Nippon Signal, and so on. Along with the rapid development of electronic technology, the customized safety computer is facing severe challenges, for instance, t

3、he high development costs, poor usability, weak expansibility and slow technology update. To overcome the flaws of the high-grade special customized computer, the U.S. Department of Defense has put forward the concept：we should adopt commercial standards to replace military norms and standards for m

4、eeting consumers demand 1. In the meantime, there are several explorations and practices about adopting open system architecture in avionics. The United Stated and Europe have do much research about utilizing cost-effective fault-tolerant computer to replace the dedicated computer in aerospace and o

5、ther safety-critical fields. In recent years, it is gradually becoming a new trend that the utilization of standardized components in aerospace, industry, transportation and other safety-critical fields.2 Railways signal interlocking system2.1 Functions of signal interlocking systemThe basic functio

6、n of signal interlocking system is to protect train safety by controlling signal equipments, such as switch points, signals and track units in a station, and it handles routes via a certain interlocking regulation.Since the birth of the railway transportation, signal interlocking system has gone thr

7、ough manual signal, mechanical signal, relay-based interlocking, and the modern computer-based Interlocking System.2.2 Architecture of signal interlocking system Generally, the Interlocking System has a hierarchical structure. According to the function of equipments, the system can be divided to the

8、 function of equipments; the system can be divided into three layers as shown in figure1.Figure 1 Architecture of Signal Interlocking System3 Component-based safety computer design3.1 Design strategyThe design concept of component-based safety critical computer is different from that of special cust

9、omized computer. Our design strategy of SIC is on a base of fault-tolerance and system integration. We separate the SIC into three layers, the standardized component unit layer, safety software layer and the system layer. Different safety functions are allocated for each layer, and the final integra

10、tion of the three layers ensures the predefined safety integrity level of the whole SIC. The three layers can be described as follows:(1) Component unit layer includes four independent standardized CPU modules. A hardware “SAFETY AND” logic is implemented in this year.(2) Safety software layer mainl

11、y utilizes fail-safe strategy and fault-tolerant management. The interlocking safety computing of the whole system adopts two outputs from different CPU, it can mostly ensure the diversity of software to hold with design errors of signal version and remove hidden risks.(3) System layer aims to impro

12、ve reliability, availability and maintainability by means of redundancy.3.2Design of hardware fault-tolerant structureAs shown in figure 2, the SIC of four independent component units (C11, C12, C21, C22). The fault-tolerant architecture adopts dual 2 vote 2 (2v22) structure, and a kind of high-perf

13、ormance standardized module has been selected as computing unit which adopts Intel X Scale kernel, 533 MHZ. The operation of SIC is based on a dual two-layer data buses. The high bus adopts the standard Ethernet and TCP/IP communication protocol, and the low bus is Controller Area Network (CAN). C11

14、、C12 and C21、C22 respectively make up of two safety computing components IC1 and IC2, which are of 2v2 structure. And each component has an external dynamic circuit watchdog that is set for computing supervision and switching. Figure 2 Hardware structure of SIC3.3Standardized component unitAfter com

15、ponent module is made certain, according to the safety-critical requirements of railway signal interlocking system, we have to do a secondary development on the module. The design includes power supply, interfaces and other embedded circuits.The fault-tolerant processing, synchronized computing, and

16、 fault diagnosis of SIC mostly depend on the safety software. Here the safety software design method is differing from that of the special computer too. For dedicated computer, the software is often specially designed based on the bare hardware. As restricted by computing ability and application obj

17、ect, a special scheduling program is commonly designed as safety software for the computer, and not a universal operating system. The fault-tolerant processing and fault diagnosis of the dedicated computer are tightly hardware-coupled. However, the safety software for SIC is exoteric and loosely har

18、dware-coupled, and it is based on a standard Linux OS. The safety software is vital element of secondary development. It includes Linux OS adjustment, fail-safe process, fault-tolerance management, and safety interlocking logic. The hierarchy relations between them are shown in Figure 4. Figure 4 Sa

19、fety software hierarchy of SIC3.4Fault-tolerant model and safety computation3.4.1 Fault-tolerant modelThe Fault-tolerant computation of SIC is of a multilevel model:SIC=F1002D(F2002(Sc11,Sc12),F2002(Sc21,Sc22)Firstly, basic computing unit Ci1 adopts one algorithm to complete the SCi1, and Ci2 finish

20、es the SCi2 via a different algorithm, secondly 2 out of 2 (2oo2) safety computing component of SIC executes 2oo2 calculation and gets FSICi from the calculation results of SCi1 SCi2, and thirdly, according the states of watchdog and switch unit block, the result of SIC is gotten via a 1 out of 2 wi

21、th diagnostics (1oo2D) calculation, which is based on FSIC1 and FSIC2.The flow of calculations is as follows:(1) Sci1=F ci1 (Dnet1,Dnet2,Ddi,Dfss)(2) Sci2=F ci2 (Dnet1,Dnet2,Ddi,Dfss)(3) FSICi=F2oo2 (Sci1, Sci2 ),(i=1,2)(4) SIC_OutPut=F1oo2D (FSIC1, FSIC2)3.4.2 Safety computationAs interlocking syst

22、em consists of a fixed set of task, the computational model of SIC is task-based. In general, applications may conform to a time-triggered, event-triggered or mixed computational model. Here the time-triggered mode is selected, tasks are executed cyclically. The consistency of computing states betwe

23、en the two units is the foundation of SIC for ensuring safety and credibility. As SIC works under a loosely coupled mode, it is different from that of dedicated hardware-coupled computer. So a specialized synchronization algorithm is necessary for SIC.SIC can be considered as a multiprocessor distri

24、buted system, and its computational model is essentially based on data comparing via high bus communication. First, an analytical approach is used to confirm the worst-case response time of each task. To guarantee the deadline of tasks that communicate across the network, the access time and delay o

25、f communication medium is set to a fixed possible value. Moreover, the computational model must meets the real time requirements of railway interlocking system, within the system computing cycle, we set many check points Pi (i=1,2,. n) , which are small enough for synchronization, and computation re

26、sult voting is executed at each point. The safety computation flow of SIC is shown in Figure 5.Figure 5 Safety computational model of SIC4. Hardware safety integrity level evaluation4.1 Safety Integrity As an authoritative international standard for safety-related system, IEC 61508 presents a defini

27、tion of safety integrity: probability of a safety-related system satisfactorily performing the required safety functions under all the stated conditions within a stated period of time. In IEC 61508, there are four levels of safety integrity are prescribe, SIL1SIL4. The SIL1 is the lowest, and SIL4 h

28、ighest.According to IEC 61508, the SIC belongs to safety-related systems in high demand or continuous mode of operation. The SIL of SIC can be evaluated via the probability of dangerous per hour. The provision of SIL about such system in IEC 61508, see table 1.Table 1-Safety Integrity levels: target

29、 failure measures for a safety function operating in high demand or continuous mode of operationSafety Integrity levelHigh demand or continuous mode of Operation(Probability of a dangerous Failure per hour)4 10-9 to 10-83 10-8 to 10-72 10-7 to 10-61 10-6 to 10-54.2 Reliability block diagram of SIC A

30、fter analyzing the structure and working principle of the SIC, we get the bock diagram of reliability, as figure 6.Figure 6 Block diagram of SIC reliability5. Conclusions In this paper, we proposed an available standardized component-based computer SIC. Railway signal interlocking is a fail-safe sys

31、tem with a required probability of less than 10-9 safety critical failures per hour. In order to meet the critical constraints, fault-tolerant architecture and safety tactics are used in SIC. Although the computational model and implementation techniques are rather complex, the philosophy of SIC pro

32、vides a cheerful prospect to safety critical applications, it renders in a simpler style of hardware, furthermore, it can shorten development cycle and reduce cost. SIC has been put into practical application, and high performance of reliability and safety has been proven. From: 模塊化安全鐵路信號計算機聯(lián)鎖系統(tǒng)1概述信

33、號聯(lián)鎖系統(tǒng)是保證交通安全、提高鐵路運輸效率的關(guān)鍵設(shè)備。長期以來，在聯(lián)鎖系統(tǒng)中采用的核心控制計算機是特定的高檔安全計算機，例如，西門子的SIMIS、日本信號的EI32等。隨著電子技術(shù)的飛速發(fā)展，定制的安全計算機面臨著嚴重的挑戰(zhàn)，例如：高的開發(fā)成本、可用性差、弱可擴展性、和緩慢的技術(shù)更新。為了克服高檔特定計算機的缺點，美國國防部提出：我們應(yīng)該采用商業(yè)標準，來取代軍事準則和滿足客戶需要的標準。與此同時，有許多關(guān)于在電子設(shè)備中采用開放式系統(tǒng)結(jié)構(gòu)的探索與實踐。美國和歐洲已經(jīng)做了很多關(guān)于利用利用劃算的容錯計算機來代替專用電腦在航天和其它安全關(guān)鍵領(lǐng)域。近年來，在航空航天、工業(yè)、交通和其它安全關(guān)鍵領(lǐng)域，利用標

34、準化部件正逐步成為一種新的趨勢。2 鐵路信號聯(lián)鎖系統(tǒng)2.1信號聯(lián)鎖系統(tǒng)的功能信號聯(lián)鎖系統(tǒng)的基本功能是通過控制信號設(shè)備，保護列車運行安全。如控制道岔的轉(zhuǎn)換、信號的開放和控制列車通過車站，它通過一種聯(lián)鎖處理規(guī)則控制線路。自鐵路運輸誕生以來、信號聯(lián)鎖系統(tǒng)已經(jīng)經(jīng)歷了手動信號、機械信號、繼電器聯(lián)鎖和現(xiàn)代計算機聯(lián)鎖系統(tǒng)。2.2信號聯(lián)鎖系統(tǒng)的構(gòu)架一般來說，聯(lián)鎖系統(tǒng)具有層次結(jié)構(gòu)。根據(jù)設(shè)備的功能，系統(tǒng)可分為三層，如圖2.1所示。圖2.1 信號聯(lián)鎖系統(tǒng)的結(jié)構(gòu)3 安全計算機的組件設(shè)計3.1設(shè)計策略模塊化安全關(guān)鍵計算機組件的設(shè)計理念不同于那些特殊定制的計算機。我們對安全聯(lián)鎖計算機的設(shè)計理念是基于系統(tǒng)的容錯性和系統(tǒng)的綜

35、合需求。將其分為三層：標準化組成單元層、軟件安全層與系統(tǒng)層，并給每一層分配不同的安全功能，最終將三層集成，并確保系統(tǒng)達到預(yù)定的安全完整性水平。三層可以描述如下： (1) 標準化組成單元層包括四個獨立的標準化CPU模塊。這一層實現(xiàn)硬件“安全”邏輯聯(lián)鎖。 (2) 軟件安全層主要用故障-安用策略和容錯算法。由于一個完整的安全聯(lián)鎖系統(tǒng)采用兩個不同的CPU輸出的結(jié)果，所以最能確保軟件設(shè)計某一版本，在設(shè)計時存在的多種錯誤，清除潛在的風(fēng)險。 (3) 系統(tǒng)層，旨在提高系統(tǒng)的可用性和冗余系統(tǒng)的可維護性。3.2容錯結(jié)構(gòu)的硬件設(shè)計如圖3.1，安全聯(lián)鎖計算機由四個獨立單元組成(C11，C12，C21，C22)。采用雙

36、容錯結(jié)構(gòu)設(shè)計(22取2)結(jié)構(gòu)，計算單元選用高可靠性、高效率的模塊，采用了英特爾XScale內(nèi)核，533兆赫的處理器。安全聯(lián)鎖計算機的操作基于兩層數(shù)據(jù)總線上。高速總線采用標準以太網(wǎng)結(jié)構(gòu)和TCP / IP通信協(xié)議、低總線控制器局域網(wǎng)(CAN)。C11、C12和C21、C22分別組成兩個獨立的安全計算部件IC1和IC2，并構(gòu)成2乘2取2結(jié)構(gòu)，并且每一部分都有計算機監(jiān)控和外部開關(guān)電路動態(tài)監(jiān)測。圖3.1 SIC硬件結(jié)構(gòu)3.3標準化組成單元在研究清楚組成模塊后，根據(jù)鐵路信號聯(lián)鎖系統(tǒng)的臨界安全性要求，我們必須做一個二次開發(fā)的模塊。該設(shè)計主要包括電源、接口和其他嵌入式電路。安全聯(lián)鎖計算機的容錯計算、處理、故障

37、的同步診斷主要依靠安全軟件。這個安全軟件的設(shè)計方法不同于其他專用的特殊計算機。在專用特殊計算機中，軟件通?；趩我宦懵队布貏e設(shè)計，限于計算處理能力和軟件兼容性，在電腦上特殊的調(diào)度程序一般基于安全性軟件設(shè)計，而不是一個普通的操作系統(tǒng)。專用計算機中容錯處理系統(tǒng)和故障診斷系統(tǒng)通過硬件耦合。然而，安全聯(lián)鎖計算機中的安全軟件是開放、寬松的，它基于標準的Linux操作系統(tǒng)。安全軟件的二次開發(fā)是至關(guān)重要的。它包括Linux系統(tǒng)調(diào)整，故障-安全導(dǎo)向、容錯性管理，安全聯(lián)鎖的邏輯。它們之間的層次關(guān)系如圖3.3。圖3.3 SIC的安全軟件層次關(guān)系3.4容錯模型和安全估計算3.4.1 容錯模型安全聯(lián)鎖計算機的多層容錯計算模型：SIC= F1oo2D (F2oo2(SC11, S C12 ), F2oo2 (SC21,SC22)首先,根據(jù)計算單元Ci1采用一個算法來完成Sci1，Ci2計算單元通過不同的算法完成Sci2，其次，安全聯(lián)鎖計算機實行二乘二取二算法計算得到的結(jié)果和Sci1、Sci2計算，輸出到FSICi中的結(jié)果，再進行二乘二取二運算，第三，根據(jù)監(jiān)視系統(tǒng)和開關(guān)單元塊，安全聯(lián)鎖計算機運算的結(jié)果在基于FSIC1和 FSIC2輸出的結(jié)果上，經(jīng)過與門的診斷處理（2取