液壓支架外文翻譯

1、外文資料翻譯學(xué)生姓名： xxx 專(zhuān)業(yè)班級(jí)： xxx 指導(dǎo)教師： xxx 內(nèi)蒙古科技大學(xué)機(jī)械工程學(xué)院2013年6月對(duì)煤礦開(kāi)采中液壓支架電液控制系統(tǒng)的研究Research on electro-hydraulic control system for hydraulic support at coal mine 學(xué) 生 姓 名：xxx 學(xué) 號(hào)：xxx 專(zhuān) 業(yè)： xxx 班級(jí)：xxx 學(xué) 院（系）：xxx 指 導(dǎo) 教 師：xxx 對(duì)煤礦開(kāi)采中液壓支架電液控制系統(tǒng)的研究摘要 基于國(guó)內(nèi)外全面綜采工作面情況的分析和調(diào)查，提出、設(shè)計(jì)、實(shí)現(xiàn)液壓支架電液控制系統(tǒng)的新要求。它采用本質(zhì)安全電路的設(shè)計(jì)技術(shù)和

2、現(xiàn)場(chǎng)總線技術(shù)以連接到主機(jī)的所有控制單元。每個(gè)控制單元的控制系統(tǒng)是配備一個(gè)液壓支架。由其他控制單元或主機(jī)所控制的某些控制單元能夠提供相鄰支撐、遠(yuǎn)程支撐和一組的支持。在防爆外殼的電腦主機(jī)也有的實(shí)時(shí)監(jiān)控，遠(yuǎn)程控制，故障診斷和上傳數(shù)據(jù)等功能。三個(gè)月的工業(yè)性試驗(yàn)的結(jié)果表明，該系統(tǒng)工作可靠，達(dá)到了設(shè)計(jì)要求。關(guān)鍵字 液壓支架；電液控制系統(tǒng)；主機(jī)1. 引言電液控制系統(tǒng)是液壓支架完全機(jī)械化采煤工作面的的核心，可以實(shí)現(xiàn)自動(dòng)控制生產(chǎn),提高生產(chǎn)效率、工作條件和采煤工作面的安全?；诰W(wǎng)絡(luò)的系統(tǒng)檢測(cè)采煤機(jī)的位置，實(shí)現(xiàn)液壓支架自動(dòng)控制。此外，它有能力監(jiān)控其他設(shè)備，實(shí)現(xiàn)地面和地下的計(jì)算機(jī)之間的通信，完成遠(yuǎn)程控制。與其他電液控

3、制系統(tǒng)相比，它具有顯著的優(yōu)點(diǎn)，如抗高壓，防燃防爆，防塵，防腐蝕，抗震動(dòng)，抗電磁干擾。國(guó)外自70年代中期人們已經(jīng)開(kāi)始研究液壓支架電液控制系統(tǒng)，九十年代經(jīng)過(guò)近十年推出產(chǎn)品并逐步完善。目前，許多國(guó)家在推廣階段已經(jīng)有了不同特點(diǎn)的成熟的產(chǎn)品，如德國(guó)、美國(guó)、英國(guó)、波蘭、日本、法國(guó)和俄羅斯等。目前，在中國(guó)生產(chǎn)的液壓支架的控制方式以手工操作為主，這相當(dāng)于發(fā)達(dá)國(guó)家在1970年的控制水平。配備了電液控制系統(tǒng)液壓支架生產(chǎn)于國(guó)外，特別是在德國(guó)。那些已經(jīng)進(jìn)入國(guó)內(nèi)市場(chǎng)的優(yōu)秀的企業(yè)主要是德國(guó)的德伯特（DBT，它的總部是在美國(guó)比塞洛斯），瑪克（Marco），EEP和TIEFENBACH和美國(guó)的JOY公司。盡管我們的政府從九十

4、年代起已經(jīng)投入了大量資金支持液壓支架電液控制系統(tǒng)的技術(shù)研究，但我們還沒(méi)有實(shí)現(xiàn)系統(tǒng)的產(chǎn)業(yè)化和本土化的目標(biāo)。為了提高采礦設(shè)備的水平，增強(qiáng)的際競(jìng)爭(zhēng)力，打破國(guó)際技術(shù)壟斷，就必須研究和自主生產(chǎn)液壓支架的電液控制系統(tǒng)。2. 電液壓控制系統(tǒng)的結(jié)構(gòu)通過(guò)對(duì)由德國(guó)的EEP公司、瑪克（Marco）公司所生產(chǎn)液壓支架的電液控制系統(tǒng)的結(jié)構(gòu)分析，結(jié)合實(shí)際應(yīng)用程序，提出了自行設(shè)計(jì)的電液壓控制系統(tǒng)的方框圖如圖1。圖1 自行設(shè)計(jì)的電液壓控制系統(tǒng)的方框圖液壓支架電液控制系統(tǒng)主要包括控制單元，主機(jī)和本質(zhì)安全的網(wǎng)絡(luò)。輔助控制單元包括控制器，傳感器，電磁導(dǎo)閥和主控制閥。該控制單元由主纜相互連接的?？刂破鞑捎米远x的幀格式RS422的通

5、信方式。然而，控制其整體采用CAN總線按照標(biāo)準(zhǔn)的擴(kuò)展幀格式的通信方式。主機(jī)監(jiān)控所有控制器通過(guò)CAN總線網(wǎng)絡(luò)。本質(zhì)安全網(wǎng)絡(luò)信號(hào)通過(guò)隔離器連接所有控制單元和主機(jī)。該控制器使用壓力傳感器、位置傳感器和位移傳感器來(lái)檢測(cè)液壓支架的工作狀態(tài)，并利用CAN總線網(wǎng)絡(luò)將信息傳送到主機(jī)電腦，然后由電腦主機(jī)決定和實(shí)施液壓支架的自動(dòng)控制。3. 支撐控制器研究控制器是電液控制系統(tǒng)核心?？刂破鞯脑O(shè)計(jì)水平?jīng)Q定該系統(tǒng)的整體水平。外國(guó)的控制器通過(guò)使用處理器實(shí)現(xiàn)，德國(guó)的瑪克（Marco），EEP和TIEFENBACH等以及美國(guó)的公司都是如此。國(guó)內(nèi)個(gè)別業(yè)主或科研人員則是嘗試使用可編程邏輯控制器（PLC）實(shí)現(xiàn)。實(shí)踐表明后者雖然具有相

6、對(duì)高的抗干擾性能，但是因?yàn)轶w積大、笨重、設(shè)計(jì)不靈活的因素，無(wú)法實(shí)現(xiàn)應(yīng)用程序（IAP）和自動(dòng)識(shí)別自身地址的技術(shù)，導(dǎo)致它不適用于特殊的地下應(yīng)用。國(guó)外發(fā)展較早，所以絕大多數(shù)采用普通單片機(jī)作為為核心處理器。目前隨著技術(shù)的發(fā)展和進(jìn)步，有許多高性能的處理器，如ARM，DSP等。然而，在考慮設(shè)計(jì)的功能、功耗和總體成本等因素時(shí)，與MCS-51兼容的增強(qiáng)型處理器是更好的選擇。使用處理器為核心的控制器，如圖框圖2。圖2 控制單元的方框圖控制器的外設(shè)配置不僅要滿足當(dāng)前的需求，也要具有可擴(kuò)展性。電磁先導(dǎo)閥的輸出端的驅(qū)動(dòng)器的數(shù)目是20。模擬輸入的數(shù)目通常是3，用于輸入抽樣信號(hào)的位移，壓力和溫度。在未來(lái)的設(shè)計(jì)中數(shù)目為6，

7、用以角度和多壓力的測(cè)量。并且，有兩個(gè)開(kāi)關(guān)輸出接口為聲光報(bào)警，兩個(gè)開(kāi)關(guān)輸入接口用于在緊急停機(jī)開(kāi)關(guān)和鎖定切換。此外，在硬件和軟件的可靠性與傳統(tǒng)的設(shè)計(jì)中，有三個(gè)特殊方法，即，閉環(huán)反饋機(jī)制，多控制驅(qū)動(dòng)器輸出機(jī)制和驅(qū)動(dòng)停止聯(lián)動(dòng)機(jī)制。首先，閉環(huán)反饋機(jī)制確保準(zhǔn)確和可靠的驅(qū)動(dòng)控制。閉環(huán)反饋機(jī)制意味著比較由計(jì)算基本指令所得到的預(yù)期的輸出狀態(tài)和由處理器所采樣的實(shí)際驅(qū)動(dòng)的輸出狀態(tài)。而且，如果比較的結(jié)果是相同的，所述處理器保持運(yùn)行。否則，采取措施，停止變頻器的輸出，立即避免生命和財(cái)產(chǎn)的損失。其次，多控制驅(qū)動(dòng)器輸出機(jī)制表明，通過(guò)硬件的驅(qū)動(dòng)指令的實(shí)施需要多個(gè)控制變頻器的輸出。例如，在主電源開(kāi)關(guān)關(guān)閉時(shí)，子開(kāi)關(guān)接通不起控制作

8、用。因此，當(dāng)子開(kāi)關(guān)關(guān)閉不能硬件對(duì)硬件產(chǎn)生效果時(shí)，它可以關(guān)閉主電源開(kāi)關(guān)，停止意想不到的驅(qū)動(dòng)器輸出的動(dòng)作。最后是驅(qū)動(dòng)器停止聯(lián)動(dòng)機(jī)制。多站點(diǎn)的調(diào)查發(fā)現(xiàn)，煤礦工人在發(fā)生故障時(shí)習(xí)慣于使用緊急停機(jī)開(kāi)關(guān)。鑒于安全考慮，為了避免緊急開(kāi)關(guān)的故障，該機(jī)制是緊急停機(jī)開(kāi)關(guān)與在硬件電路的鎖定開(kāi)關(guān)相連接。在這種情況下，按下緊急開(kāi)關(guān)，這意味著同時(shí)按下鎖定開(kāi)關(guān)。因此，如果緊急開(kāi)關(guān)發(fā)生故障，鎖定開(kāi)關(guān)仍然工作以確保工人的安全。該軟件設(shè)計(jì)采用模塊化的設(shè)計(jì)。在不同的礦區(qū)搭配不同的液壓支架，這會(huì)帶來(lái)高性能的軟件控制單的。4. 主機(jī)研究電腦主機(jī)主要是由軟件和硬件組成，通過(guò)連接現(xiàn)場(chǎng)總線與所有的控制器形成通信網(wǎng)絡(luò)，實(shí)時(shí)監(jiān)控每個(gè)液壓支架的工作

9、狀態(tài)。因?yàn)橹鳈C(jī)計(jì)算機(jī)在地下工作，它是必需得有防濕、防塵和防爆性能。主機(jī)的設(shè)計(jì)也需要符合可擴(kuò)展性和兼容性原則。硬件設(shè)計(jì)需要充分考慮系統(tǒng)的可擴(kuò)展性，充分支持硬件接口和軟件性能。與常見(jiàn)的計(jì)算機(jī)硬件和軟件的相容性也很重要，以便它可以利用存在的技術(shù)減少重復(fù)工作。電腦主機(jī)通常是通過(guò)采用工業(yè)計(jì)算機(jī)和滿足環(huán)保要求的防爆計(jì)算機(jī)實(shí)現(xiàn)，但它的可擴(kuò)展性差，因此該系統(tǒng)的主機(jī)采用嵌入式PC104的定制方案。主機(jī)計(jì)算機(jī)有大量的擴(kuò)展接口，如RS232，RS485，CAN總線，光纖接口，電流環(huán)接口等。每個(gè)接口都有符合安全標(biāo)準(zhǔn)的光電隔離電路，因此主機(jī)具有很強(qiáng)的可擴(kuò)展性和很好的兼容性。它可以直接連接到采煤機(jī)、破碎機(jī)、階段裝載器、刮

10、板輸送機(jī)和監(jiān)測(cè)地下的設(shè)備通信接口，從而實(shí)現(xiàn)綜采工作面全自動(dòng)化。圖3 液壓支架的應(yīng)用軟件的主界面主機(jī)的監(jiān)控功能是通過(guò)在嵌入式操作系統(tǒng)上運(yùn)行的應(yīng)用軟件實(shí)現(xiàn)的。應(yīng)用軟件包含后臺(tái)數(shù)據(jù)處理部分和前臺(tái)顯示部分。后臺(tái)程序通過(guò)現(xiàn)場(chǎng)總線收集相關(guān)數(shù)據(jù)，處理后儲(chǔ)在數(shù)據(jù)庫(kù)中。前臺(tái)程序?qū)崿F(xiàn)了讀取、搜索數(shù)據(jù)庫(kù)，并在主界面中顯示，如圖3所示。類(lèi)別WindowsDosVxworkslinux成本付費(fèi)付費(fèi)貴免費(fèi)定制中壞好非常好源代碼不公開(kāi)不公開(kāi)不公開(kāi)公開(kāi)實(shí)時(shí)表現(xiàn)壞壞好一般硬件良好良好良好良好功能多任務(wù)單任務(wù)多任務(wù)多任務(wù)表1 操作系統(tǒng)相比該控制系統(tǒng)采用嵌入式Linux操作系統(tǒng)。Linux操作系統(tǒng)和其他操作系統(tǒng)之間的比較顯示在表1

11、上。從上面的表格可以看出，嵌入式Linux操作系統(tǒng)具有相當(dāng)大的優(yōu)勢(shì)，如低成本，高度可定制的，穩(wěn)定的運(yùn)行和廣泛的硬件支持，以及完全免費(fèi)。5. 本質(zhì)安全網(wǎng)絡(luò)的研究在現(xiàn)場(chǎng)總線使用中，德國(guó)EEP公司采用PROFIBUS技術(shù)實(shí)現(xiàn)信息的傳遞，而MARCO公司使用自定義格式集電極開(kāi)路技術(shù)。目前，在國(guó)內(nèi)使用的成熟的技術(shù)是由德國(guó)的 BOTCH 公司所提出的CAN總線技術(shù)?？紤]到實(shí)際系統(tǒng)中龐大的數(shù)據(jù)傳輸，控制器之間的通信由全雙工RS422技術(shù)來(lái)實(shí)現(xiàn)。當(dāng)在井下作業(yè)時(shí)，現(xiàn)場(chǎng)總線需要特殊處理。因?yàn)楸举|(zhì)安全的要求，電源裝置的功率受到嚴(yán)格的限制。根據(jù)電源裝置、控制器和電流驅(qū)動(dòng)閥門(mén)的總功率，通常每個(gè)電源只能提供五或六個(gè)控制器

12、。因此，系統(tǒng)需要大量的獨(dú)立電源裝置。為了避免因電流不平衡導(dǎo)致失去內(nèi)在安全性，在控制器之間的數(shù)據(jù)信號(hào)是由可切斷電連接信號(hào)隔離器相連接。6. 總結(jié)國(guó)在外現(xiàn)有技術(shù)的廣泛調(diào)查的基礎(chǔ)上，完成了液壓支架電液控制系統(tǒng)設(shè)計(jì)和實(shí)現(xiàn)，并已通過(guò)了國(guó)家機(jī)構(gòu)的認(rèn)證資格。在河南省平煤集團(tuán)的工業(yè)性試驗(yàn)中該系統(tǒng)可靠運(yùn)行三個(gè)月。電液控制系統(tǒng)奠定了煤礦安全、高效生產(chǎn)的基礎(chǔ)，將會(huì)使國(guó)內(nèi)的全機(jī)械化采煤技術(shù)上升到新的臺(tái)階。致謝這篇研究報(bào)告是由中國(guó)人民科學(xué)技術(shù)部（國(guó)家863計(jì)劃項(xiàng)目，項(xiàng)目編號(hào)2008AA062200）和中國(guó)煤炭工業(yè)協(xié)會(huì)（項(xiàng)目的號(hào)碼是MTKJ08-301的）共同資助下完成。The 6th International Con

13、ference on Mining Science & TechnologyResearch on electro-hydraulic control system for hydraulic support at coal mineYu Yuesen, Dai Peng, Xu Yajun, Peng Liming, Wu Xiaojie *School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221008, ChinaAbstractBa

14、sed on the investigation and analysis of the situation in full mechanized coal mining face at home and abroad, the electrohydraulic control system for hydraulic support is put forward, designed and realized. It adopted intrinsically safe circuit design technology and field bus technology to connect

15、all control units to the host computer. Each control unit of the control system is equipped with one hydraulic support. Certain control unit(s) controlled by either the other control units or the host computer can operate adjacent support, distant support or a group of supports. Host computer in an

16、explosion-proof housing also has the functions of real-time monitoring, remote control, fault diagnosis and upload data etc. The result of industrial experiment up to three months shows that the system works reliably and meets the design requirements. Keywords: Hydraulic Support, Electro-hydraulic C

17、ontrol System, Host Computer1. IntroductionElectro-hydraulic control system for hydraulic supports is the core of full mechanized coal mining face. And It can implement automatic control of production equipments and improve the production efficiency, working conditions and safety of coal mining face

18、. The system based on network detects the position of the shearer and hydraulic supports automatically to achieve automatic control. Besides, it has the ability to monitor states of other equipments, to implement the communications between ground and underground computers and to complete the remote

19、control. Compared with other industrial electro-hydraulic control systems, it has special characteristics, such as high pressure, anti-burning explosion-proof, dust-proof, anti-corrosion, anti-vibration and anti-electromagnetic interference.Since the mid-1970's people abroad have started to stud

20、y electro-hydraulic control system for hydraulic supports,launched the product after nearly a decade and perfected gradually the system after the 1990's. At present, many countries already have had mature products with different characteristics in the promotion stage, such as Germany, the United

21、 States, United Kingdom, Poland, Japan, France, and Russia etc.At present, the control method of hydraulic supports made in China is mainly manual, which is equivalent to the control level of developed countries in the 1970s. The electro-hydraulic control system equipped with hydraulic supports is m

22、anufactured in foreign countries, especially in Germany. The outstanding companies which have already come into home market are DBT (its HQ is Bucyrus in the USA), Marco, EEP and TIEFENBACH in Germany and JOY in America. We have not achieved the target of industrialization and indigenization of the

23、system, although our government has invested much in technical research of the electro-hydraulic control system for hydraulic supports from the 1990s. In order to improve the level of mining equipments, strengthen the international competition and break through the international technical monopoly,

24、it is urgent to research and produce utonomously electro-hydraulic control system for hydraulic supports.2. Structure of the electro-hydraulic control systemThrough the structure analysis of the electro-hydraulic control systems for hydraulic supports made by the EEP Company and Marco Company in Ger

25、many, combined with the actual application, block diagram of the self-designed electro-hydraulic control system is put forward and shown in Fig. 1. Fig. 1. Block diagram of hydraulic supports electro-hydraulic control systemElectro-hydraulic control system for hydraulic supports mainly contains the

26、control units, host computer and the intrinsically safe network. The support control unit includes the controller, sensors, electromagnetic pilot valves and main control valves. The control unit connects each other by the main cable. The controller adopts RS422 communication in accordance with self-

27、definitional frame format. However, the overall adopts CAN bus communication in accordance with the standard extend frame format. The host computer monitors all controllers through the CAN bus network. The intrinsically safe network connects all the control units and host computer by signal isolator

28、s. The controller uses the pressure sensor, the position sensor and the displacement sensor to detect the working state of hydraulic supports and takes advantage of CAN bus network to transfer information to the host computer, then the host computer makes decision to implement the automatic control

29、of hydraulic supports.3. Research on support controllerThe controller is the core of electro-hydraulic control system support. The design level of controller determines the entire level of the system. The foreign controller is achieved by using processors in not only the Germany companies, such as M

30、ARCO, EEP and TIEFENBACH and so on, but also the American companies. Domestic individual owners or scientific researchers try to use the programmable logic controller (PLC) to achieve the core processing. Practice shows that it has relatively high anti-interference performance, but is not suitable f

31、or special underground applications because of the factors such as large, bulky, designed inflexible, in application program (IAP) not achieved, self-address not automatic identification. Development in foreign countries is earlier, so the vast majority uses the ordinary MCU as the core processor. C

32、urrently with the development and progress of technology, there are many high-performance processors such as ARM, DSP etc. However, in consideration of the factors of design features, the power consumption and overall cost etc, the enhanced processor compatible with MCS-51 has been chosen. The block

33、 diagram of the controller using the processor as the core is shown in Fig. 2. Fig. 2. Block diagram of control unitPeripheral configuration in the controller is considered to meet not only the current needs but also the expansibility. The number of the drive outputs for electromagnetic pilot valves

34、 is 20. The number of the analog input is usually 3 used for sampling signals of displacement, pressure and infrared. And the designed is 6 for the measurement of the angle and multi-pressure in the future. In addition, there are two switching output interfaces for the sound and light alarm and two

35、switching input interfaces for the emergency shutdown switch and the lock switch.In addition to conventional design for reliability in hardware and software, there are three special treatments used, namely, the closed-loop feedback mechanism, the drive output of multiple control mechanism and the dr

36、ive stop linkage mechanism. Firstly, the closed-loop feedback mechanism ensures the drive control accurate and reliable. The closed-loop feedback mechanism means comparing the drive actual output state sampled by the processor with the expected output state calculating on the basis of the command. A

37、nd if the compared result is the same, the processor keeps running. Otherwise, it takes measures to stop the drive output immediately avoiding losing of life and property. Secondly, the drive output of multiple control mechanism indicates that the implementation of the drive command needs multiple-c

38、ontrol through hardware. For example, before the main switch is off, the sub-switch turned on can not implement the action. Therefore, when the sub-switch turning off cannot take effect in hardware, it is possible to turn off the main switch to stop the unexpected drive output action. The last is th

39、e drive stop linkage mechanism. The multiple-site survey has found that mine workers are used to use emergency shutdown switch to stop action in the event of failure. In order to avoid failure of the emergency switch concerning the safety, it is linked with the lock switch in the hardware circuit. I

40、n this case, when the incident occurred, pressing the emergency switch, means pressing the lock switch simultaneously. So if the failure of the emergency switch occurs, the lock switch still works to ensure the safety of workers.The modular design is adopted in software design. Different hydraulic s

41、hields are collocated at different mines. And this brings the differences in software for high performance of control unit.4. Research on host computerHost computer is mainly composed of software and hardware, and it forms communications network through field bus and all controllers, which is real-t

42、ime monitoring the work states of every hydraulic support. Because the host computer works underground, it is required that it should have a moisture-proof, dust-proof and explosion-proof performance. Design of the host computer also needs to meet the principle of expansibility and compatibility. Th

43、e proceeding of hardware design demands fully considering system expansibility, which is supported by hardware interface and software performance. The compatibility of hardware and software with the common computer is also important, so that it can utilize the technology in existence and reduce dupl

44、icated effort. Host computer usually is realized through adopting industrial computer and explosion-proof computer which satisfy the environmental requirements, but its expansibility is poor. So the host computer of this system adopts customized scheme with embedded PC104.Host computer has a lot of

45、extended interfaces, such as RS232, RS485, CAN bus, fiber interface and current loop interface and so on. Each interface has a photoelectric isolation circuit which is in compliance with the safety standards, thus the host computer has very strong expansibility and very well compatibility. It can co

46、nnect directly to communication interfaces of the shearer, crusher, stage loader, scraper conveyor and monitor underground equipments, so as to realize the automation of full mechanized coal mining face.Fig. 3. The main interface of application software for hydraulic supportsThe monitoring function

47、of the host computer is achieved by application software running on the embedded operating system. The application software consists of background data processing section and foreground display section. Background program collects relevant data through field bus and stores in the database after proc

48、essing. Foreground program achieves the read and search of the database and displays the data in the main interface which is shown in fig.3Table 1. Operating systems comparedItemWindowsDosVxworksLinuxCostNot freeNot freeExpensiveFreeCustomizingnot badBadWellVery wellSource codeNot openNot openNot op

49、enOpenReal time performanceBadBadWellCommonlyHardwareWellWellWellWellFunctionMultitaskSingle-taskMultitaskMultitask This control system uses the embedded Linux operating system. And the comparison between Linux operating system and other operating systems is shown in table.1.It can be seen from the

50、above table that the embedded Linux OS has considerable advantages such as completely free of cost, highly customizable, stable operation and a wide range of hardware support.5. Research on the intrinsically safe networkIn field bus use, EEP Company in Germany adopts profibus technology to achieve i

51、nformation transfer, while MARCO Company uses the custom format open collector technology. At present, the mature technology widely used in domestic is CAN bus technology put forward by BOTCH Company in Germany. Communication between controllers is achieved by full-duplex RS422 technology in conside

52、ration of the vast transferred data in the actua system.Field bus needs special treatment when working underground. And because of the request of intrinsically safe,the power of the power supply subjects to strict limitations. Usually each power supply can only supply five or six controllers accordi

53、ng to the power of power supply, controllers and current-driven valves. Thus a large number of independent power supplies are needed for the system. In order to avoid current imbalance leading to lose intrinsic safety, the data signal between the controllers is communicated by signal isolators which

54、 can cut off electrical connection.6. ConclusionBasing on wide investigation of existing technology abroad, the electro-hydraulic control system for hydraulic supports was designed and realized, and it has passed the national institutions certification examination. The system has run reliably for three months in industrial experiment at Pingmei Group in Henan province. The electrohydraulic control system has laid the foundation successfully for safe and high efficient coal mine, which improves significantly the domestic automation level of full mechanized coa