Network Multifunctional Substation with Embedded System in Coal Mine

J. China Univ of Mining Tech. English EditionVol 16 No. 2Network Multifunctional Substation withEmbedded System in Coal mineMENG Fan-rong, HUO Yan", ZHOU YongSchool of Computer Science and Technology, China University of mining& Technology, Xuzhou, Jiangsu 221008, ChinaNingbo City College of Vocational Technology, Ningbo, Zhejiang 315211, ChineAbstract: In order to solve the problems of mining monitor and control systems during the constructiondigital mining combined with network and embedded technologies, the kernel access equipment of a mininnd control system was proposed and designed. It is the architecture of a mining embedded network musubstation. This paper presents the design of hardware and software of the substation in detail. Finally, the system's efficiency was validated through experimentationKey words: mining, embedment, network multifunctional substation, architectureCLC number: TD 761 Introductioncan collect and process the environmental information of the coal mine. The information includes gasMining monitor and control systems play a very density, carbon monoxide density, wind speed, temimportant role in the whole mining production proc- perature, humidity, dust, pressure and so on. The subess. In the constructed mining Ethernet networks, the station can independently decide to provide warningproblems that must be solved for mining monitor and information and the actions of connecting and dis-control systems are as followsconnecting power to relevant equipment according to1)Research and develop the corresponding sys-of processing the environmental informa-tems'accessing equipment and software and connect tion. At the same time, the substation can pack theall of the monitor systems into the lan of the coal data by UDP and transfer them to the main station onmine.Hence, all of the subsystems will be interlinked the ground through industrial Ethernet. The substaon an open platform composed of the computer net- tion may also sometimes accept control of the mainstation on the ground and execute corresponding ac2) Integrate the data from monitor and control tions. Each substation owns a fixed IP, so it is con-systems with that from information management sys- venient to manage and it is easy to confirm the loca-tems to form a unified data mode, which supports tion corresponding to the environmental informationWeb browsing, querying, statistics and construction according to the IP. The multifunctional substationsof different types of expert systemsproposed in this paper are connected in a coal mineThe kernel equipment of the security monitor security monitor and control system. It is shown inand control system is the multifunctional substation. Fig. IIn order to solve the problem of mining monitor andEthernetcontrol systems combining with network and embeded technologies, the kernel access equipment of ander the minehe ground」 The groundmining monitor and control system was proposed anddesigned in this paper. It is the architecture of a min-Network controllerng embedded network multifunctional substationMeanwhile some key technologies are discussedOptical or electric cableMultifunctionalMultifunctional2 Kernel Technologies of a Mining Em-bedded Network Multifunctional Sub中国煤化工stationCNMHG 5An embedded network multifunctional substa-tion(hereafter referred to simply as the substation)Fig. 1 Architecture of coal mine security monitorand control systemReceived 21 Sber 2005: accepted 11 March 2006Co数据T+8651683859:-mailaddress:menger@cumt.edu.cnMENG Fan-rong et al.Network Multifunctional Substation with Embedded System in Coal Mine2.1 Architecture of substationThe frequency of the microprocessor is veryAs shown Fig. 1, the way of constructing a net. high in the substation system, but the clock of thework between the substation and the other equipmentsure the integrality of the signal and electrical source,of the coal mine security monitor and control system the circuit of the substations hardware is designed ina tree-snaped system of industrial Ethernet. In or- 2 parts: one is the 10 board of data acquisition,der to ensure compatibility, the opened TCP/IP pro- which is responsible for acquiring the parameters oftocol is adopted, and the embedded RTOS is transplanted into the substation system. The substation gas, carbon monoxide, wind speed, temperature, huCPU adopts a high-powered 32-bit ARM kernel RIsc midity, dust, pressure and so on; and the other is thenetwork CPU main board, which is responsible forembedded microprocessor to perform its high-speed, receiving and processing the parameters of the databig-capability data processing and control functionsThe substation system design is shown in Fig. 2. It acquisition board, and providing control informationconsists of hardware and softwareto the data acquisition 1o board according to theprocessing results. At the same time, the networkSoftware systemCPU main board is also responsible for entire duplexcommunication between the main stations on theground and the mine LAN. The key technologies ofthe network CPU main board and the data acquisitionH C/OS-II Kcmelth1/O board involved in the hardware architecture willHardware abstractbe briefly introduced in the following section2)Research and design of the network CPUNetwork interfacemain boardThe 32-bit microprocessor produced by SAM-SUNG Corporation is adopted as the CPU in theROM Ynetwork main board of the substations a 2M Flash isRAMTDMAused to solidify the OS and application code, andrial-port and JTAG ports are used to debug the systemFig. 2 Design of substations architectureRTL8019AS is adopted as the Ethernet interface. Inorder to connect with the data l/o board, the data bus2.2 Substation's hardware architectureand control bus are set aside on the main board. Inaddition the wire of the electrical source of the con-1)The principle of the substation's hardwaretrol board is provided through the interface bus inIn the hardware of the embedded system, various order to implement a single electrical source supply-types of the embedded microprocessors are the kernehardware of the whole embedded system The CpU g power to the system. The hardware architecture ofhe substation network CPu main board is shown inadopted in this paper is Samsung S3C44B0X based Fig 4on ARM. It is the Korean SAMSUNG's microcon-troller that takes a 32-bit RiSC ARM7TDMI micro-processor as kernel.EthernetThe principle of the substations hardware is2MB Lincshown in Fig 3. The main station communicates withFlash(ROM)RS232the substation through the network and the commu32-bitnication is TCP/IP. The entire duplex Ethernet con-8MB SDRAMbased on arMtroller RT8019AS is adopted as the network interface(RAM)S3C44B0XTAGEthernetDebug portRTL8O19ASFlash(ROM扫意S3C44BOXhe center processor modFig. 4 Hardware architecture of substation networkControlCPU main boardAD conversion中国煤化工 d as the refenceCNMHGmain board TheFilterCircuit conversionkey point is to be familiar with S3C44B0, especiallythe storage medium assignment situation of the sys-Switch signal inputs Analog signal inputstem. In this substation, the storage medium assign-ment situation of the system is listed in Table 1g3 Substation's hardwarehina Univ, of Mining Tech (English Edition)Vol 16 No. 2Table 1 Storage medium assignment situation of systemWhen the input current signal is 1-5 mA, setThe storage medium The interface with storage mediumR3=470 Q2 and adjust Rll in the circuit diagram to2M NOR Flashmake the amplified multiple K=2. 1, so that the 1-5Voutput can be obtained. Similarly, when the input16MB NAND Flashcurrent signal is 4-20 mA, set R3=100 Q2 and adjustBank 3ReservedRIl in the circuit diagram to make the amplifiedmultiple K=2.5, so the 1-5V output can be obtained.RTL8019ASFrequency signal: The circuit adopting LM2917Bank8M SDRAMto process the F/V conversion is shown in Fig. 7. TheReservedrelationship between the input frequency f and3)Research and design of the data acquisitionoutput voltage V can be expressedVu=K×V×fm×C1×R5The data acquisition board in the substation in-where K is the transfer function, K=1cludes 3 parts: analog signal input, switch signal in-out and output. The architecture of the data acquisition board is shown in Fig. 5DB& CB& PowerBus interface A/D conversion Bus interfacetage amplifyooI uFi uSwitch signal inputs Analog signal inputs(8 ways)Fig 5 Architecture of data acquisition boardFig. 7 Conversion circuit of frequency and voltage signalb) Switch signal inputa) Analog signal inputSwitch signal input includes the current signal ofThree kinds of analog signals, such as voltage, ImA/5mA and the non-electronic contact signal. Thecurrent and frequency, are accessed into the data ac-quisition board. All kinds of analog signals are con- processing method for the 1 mA/5 mA current signalverted into 0-5 V, then transferred to CPU after a/d is similar to that of the current(1-5 mA)analog sig-nal. And the processing of the non-electronic contactVoltage signal: two kinds of voltage signals canbe accepted by the substation, namely, 0-1 V and 0-5c)Switch signal output.V. The 0-5 V voltage signal needn't be converted8 groups switch outputs are designed in the sub-while the 0-1 V voltage signal needs to be converted station and an isolate relay is adopted. The digitaland amplified 5 times. Then the converted 0-5V sigsignal is transferred to DC relay through a flip-latchnal is transferred to a/d conversionand drive-circuitCurrent signal: two kinds of current signals can 2.3 Substation software architecturebe accepted by the substation, namely 1-5 mA and4-20 mA 4-20 mA is mainly used on the ground andhe uC/OS-II is selected as the RtOS prototype1-5 mA is used underground in the mine. The con-in software design of this system because it is open-version circuit of current signals is shown in Fig. 6source, small scale and short code and there are already many successful cases in practice. The key inthe design of the substations software is how to buildthe systems rToS based on the destination hardwareboard with u C/OS-ll. This includes porting uC/OSI中国煤化工8, the porting ofetcCNMHGg the file systemilt. the softwareimplementation will be realized1)Porting the uC/OS-lIRIl 100 kH C/OS-II is a kernel of an embedded andFig 6 Conversion circuits of current signal andreal-time system with open source. The porting prob-lem in the future has already been taken into accountMENG Fan-rong et alNetwork Multifunctional Substation with Embedded System in Coal Minein the design. When porting, only several interfaceo The timer functions are sys_arch_timeoutsfiles need to be modified. Now there are many arti- These can be achieved by modifing the code of call-cles and examples of porting the uC/OS-II on certain ing the function in LwIP.CPU, and the details are in the literature [4]. The fol-e The thread process creating function is syslowing is the key element of porting on ARMthread_newO). It can be implemented by adopting thea)The system can run in user mode or supervi- process creating function directly in u C/OS-IIsor mode. The supervisor mode is adopted in most ofb) Hardware interfaceporting examples. If it is necessary, the system canModify the file of ethernetif c and implementalso be set as user mode. But the switch of processing input and output at the bottom level. Sendingmode must be completed through abort processing, receiving data packages are completed by an interruptwhich makes the operation much more complicatedprocessing program. When a data package is receivedb)The system supports the nest of interrupt a message is sent to TCP/P thread process. After themasking, pushes cpsr to the stack in OS_ENTER- TCP/IP thread process is dispatched, it deals with theCRITICALO and pops it in OS_EXIT_CRITICALO. message and jumps to a different program of procThe ordinary interrupt is used in the system essing protocol according to the status of packagetimer. The interrupt masking only masks the ordinary3)Designing the driversinterrupt and the fast interrupt is set aside to processDesigning the drivers primarily includes twothe outside interrupt quicklyparts of the data acquisition board and network mod-d) Because the stack in different modes is dif- ule. In this paper, the data acquisition board takes theferent in ARM, storing the registers in the original MAX197 A/D conversion made by MAXIM Corpmode is a problem. So, first store the spsr and Ir in ration as the center. And the network module takesinterrupt mode( these two refer to cpsr and pc in the RealTek's 8019AS chip as the center. After ana-original mode), then return to the original mode by lyzing the characters of these two chips, writing driforce, and push the cpsr, pc and register ro-rl2 to ers is relatively easy, so the detail is omitted herestack in order in the end. This process is used to4)Creating file systemswitch the tasks in interruptIn order to store the history data of the substa-2) Porting the LwlPtion system, the NAND Flash K9F2808U08B with aBecause the system needs to be connected to capability of 16 M is adopted to store files.ConsidLAN, a TCP/IP protocol stack is necessary. LwIP is a ering the demand of the substation for a file system,alight and open source TCP/P protocol stack and has file system similar to FAT16 is designed in this pathe characteristics of occupying little RAM, less deAccording to the characteristic of Flash, thependency on the operating system, and completely file system adopts separation of a file allocation tablefree of charge. It has a self-contained IP,ICMP, UDP, and three level structures for design, and supplies theTCP protocol and also has the function of estimating upper level with API functions such as initializing thethe overtime, renewing and repeating quickly, adjust- file system, file opening, closing, reading, writing anding the window, etc. LwIP also provides the optional deleting, and quitting the file systemAPI functions that can be called by the upper level5)Designing the upper level applicationsprogram. Because a flexible storage mechanism ofAs a very important software level, the partitiondata packages is adopted, the data sending and re- of internal tasks of application affects the embeddedceiving in each level's protocol neednt be copied and system's integer performance directly. So, the partilittle memory is consumed. The key step of porting tion of internal tasks of application, the confirmationLwIP is in detail as followsof each task's priority and the task,s stack and thea)Overwrite the functions relevant to the operat- choice of priority scheduling policy should be takeninto account. In order to limit the length of this paper,The following functions need to be realized ac- the code is not listed in detail here. According to thecording to u C/OS-lIrequirements of the network multifunctional substaThe related functions communicating among tion system, the program flow chart of the upper levelprocesses are sys_mbox_newO, sys_mbox_- freed, software is shown in Fig 8sys_mbox_postO, sys_arch_mbox_ fetcho, sys_sem- 2.4 Testing the substation systemnewO, sys_sem_ free, sys_sem_signalO, sys_archsem_wait(. Although all these functions can be中国煤化工 of mining safetyfounded in HCyOS-lI, mbox here should be imple- monmented with the message queue in uC/OS-II Mbox comCNMHGn our lab. A hostain station and themaybe only has one message in the program and it destination board is set as the substation under min-can be realized through mailbox. But sys_mbox_ free ing. Both host computer and destination board areand sys_sem_free are difficult to implement, so the accessed to the network through a switch. The fieldmethod of allotting and call backing from free queue signal is primarily simulated by electrical instrumentscan购据dand devices in lab. 8 analog inputs adopt the signalJ. China Univ of Mining& Tech(English Edition)VoL 16 No. 2tween the main station and the substation, But thedefect of losing packages in UDP is also obvious. So,in order to analyze the substations performance completely, the substation system is tested and analyzedaccording to this problem. That is the test of whetheradopting this protocol can satisfy the system,s restation on the groundata input(8&16)quirements orBy continuously testing the quantity ofand receiving packages, it can be calculatedacquired fromformula n=(N-N,)/N, that the package losingrate is roughly the loss of a package every 1l hoursand 7 minutes, which is within the range of systempermission. It shows that this network multifunctionalbstation system passes the test at the lab stagethe index of every aspect can satisfy the system's requirements3 ConclusionsDelay 0.5 secondThe mining network multifunctional substationproposed and designed in this paper provides a reliFig 8 Program flow chart of network multifunctionalable solution to the network multifunctional substation mining monitor and control system. It can eliminate the protocol barrier among different monitor andgenerator, voltage watch, electric current watch and control platforms, conquer the shortcomings of smallothers to generate 0-5 V voltage signals and 4-20capability and bad compatibility in other monitor andcurrent ring signals(check sentence meaning,control platforms, and establish the foundation of fullfusing). 16 switch inputs adopt direct short circuits to open industrial control by forming a new incorporasimulate the switch of field contact. The relay is used tion of management, control and monitoring for real-to simulate switch output. Multimeter switch signals izing the seamless combination of OA and automaare used to measure each method, s status of connec- tion By importing the rtos into the system, the sys-tion or disconnection In the host computer terminal, tems stability can be improved. The Ethernet net-theg software developed by VB and SQL work monitor and control platform with highServer is used to monitor and analyze the status of the openness and stabilization must be the developmentsystem operating. For the advantages of UDP itself, trend of mining integrating monitor and control sys-the protocol is adopted in the communication be-temsReferences[1] LiP. Study on the Network Architecture and Routing Algorithm of Mining Broad Band Integration Operation Digital NetworkMaster dissertation]. Xuzhou: China University of Mining& Technology, 2003. (In Chinese[2] Samsung Electronics Co Ltd S3C44B0X High Performance Network Controller User's Manual Rev 1.0. 2001[3]samsungElectronicsCoLtd.S3c44bOx32-birRiscMicrocontrollerUser'sManual.http:/www.samsungcom1999[4] Jean J L. HC/OS-lI--Open Source Timing Embedded Operation System. Beijing: Tinghua University Publishing Company,c002. (In Chinese)[5]Ma ZM. 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