Design and application of integrated automation system platform of mine based on PON

CHENG Xue-zhen,YUAN Xing-jie,PANG Ming-xiang,WEI A-ying

(College of Electrical Engineering and Automation,Shandong University of Science and Technology,Qingdao 266590,China)

0 Introduction

Automation level of mine is an important index for modern mining enterprises. It is mainly used to realize the information exchange of each subsystem which can be seamlessly transferred to the central management system,and it has great significance for a mine construction to establish a stable,efficient and open transmission platform[1,2]. Mine automation system in China has developed from the early single host to network now mainly based on switched Ethernet,which has realized the network transmission of information,remote management and other functions[3]but affected the communication quality of active devices seriously due to the bad environment underground. Real time conditions of Ethernet in case of overload are difficult to be effectively guaranteed[4]. Therefore,integrated automation system design of a new network transmission platform has become the significant work[5,6]. This paper introduces the integrated automation platform based on passive optical network (PON).

1 PON

1.1 Composition of PON

Mine PON is mainly composed of optical network unit (ONU),passive optical splitter (POS) and optical line terminal (OLT)[7]. Role of optical network unit (ONU) in PON system is to receive the broadcast data from OLT; at the same time,the user sends the Ethernet data from OLT allocation sending window in upward direction. It is important for each subsystem to access to the network and conduct the data exchange with the upper network which makes the system to exchange information quickly and efficiently. The function of mining passive optical splitter (POS) is to connect OLT and ONU,and is useful for the distribution of the optical power in the PON system. Normally POS line rate is at 2,4,8,16,32,and can cascade operation between the beam splitters. Optical line terminal (OLT) is the core equipment of PON system. At boot time,corresponding bandwidth allocation of the ONU is important for the light distribution network interface,data cross-linking and the underlying ONU registration. When control ranging process is launched and the distance information is recorded,centralized control center's instruction downward direction after OLT will be sent to the lower level of ONU,eventually to the underlying device. The data which ONU gathered in upward direction after OLT can be entered to the centralized control center.

Compared with the Ethernet switch,applications of PON in the industrial real-time monitoring network perform are well. If the switch has aMport,its transmission delay time isM×N×82 μs,and its overload delay time is (N×(82+1)+5) μs. But for the PON system with ONU,its transmission delay time is (N×(82+1)+5) μs. Based on the above analysis,the results show that overload operation of the transmission rate of PON is the same as the normal circumstances,so the PON system has better real-time performance than the Ethernet switch and can ensure the system work normally.

1.2 Working principle of PON

IEEE (Institute of Electrical and Electronics Engineers) EFM working group was established in 2000 at the end of the Ethernet in the First Mile study group,and introduced a new access technology standard of EPON (Ethernet Passive Optical Network)[8]. In 2004,IEEE EFM working group released the EPON standard,and incorporated into ah-standard 2005 in 2005.

According to the IEEE802.3 protocol,PON can send data of word length up to 1 518 bytes. EPON can send the data from OLT to multiple ONU and receive the data from a number of ONUs to OLT,which is adopted by the different transmission technologies[9]. It is shown in Fig.1.

Fig.1 Flow chart of PON

There is a great difference in the information transmission process between PON uplink and downlink. In the upward direction,all the ONUs share the upload bandwidth,and use the same wavelength. When the ONU is registered successfully,OLT will allocate the corresponding bandwidth system with time division multiple access (TDMA) technology to organize data of multiple ONU into TDM information flow,which is transferred to the OLT. Each ONU only transmits data at the beginning. Simultaneously the PON system also uses dynamic bandwidth allocation (DBA) through the specific algorithm and the ONU dynamic allocation upward band width which guarantees each ONU to transmit the data without the conflict. In the downside direction,transmission of data uses another wavelength. During the transmission procedure,it periodically broadcasts on this port to allow access to the information such as the time. OLT will assign a link identifier unique to different ONUs. Information will be transmitted in the form of packets with the maximum length of 1 518 bytes. Each packet will uniquely identify the destination of ONU[10]. When ONU receives the data,it will only accept logo of the information,and ignore other information.

1.3 PON structure

PON belongs to the access network. Topology of the PON in communication has circular,total linear and star. In the practical applications of optimal network design principle,the combination should select which kind of or several according to the specific circumstances of the scene. Using different ratios of the beam splitters can also achieve the network topology structure. Generally we use the combination of two or more forms[11]. The network with redundancy also has network features simplicity. The network topology structures are shown in Figs.2-4.

Fig.2 Tree network of PON structure

Fig.3 Loop network of PON structure

Fig.4 Bus network of PON structure

2 Design of integrated automation system platform

2.1 Design of system hardware

Every independent subsystem of the mining enterprises can be integrated with PON to implement centralized management and share information. At the same time,the network has a lot of advantages such as dynamic distributed bandwidth,easy installation,maintenance and construction of low cost[12]. Interface of RJ45 or RS-485 will carry on transmission of video and voice,and product data information to control center whose transmission speed can reach 1 000 Mb/s which meets the requirement of mine integrated automation system. Depending on its unique redundancy mode,the damage point of PON on fiber optic lines will not have a significant impact on the overall system.

According to the wide coverage of underground in a coal mine and related to the various subsystems,the design intends to use PON of three double loop. One is used for the access of each subsystem on the ground,and the others in the underground in different levels are used to ensure that the data such as transmission system and image information can be transferred stably and highly efficient.

As shown in Fig.5,it is diagram of mine integrated automation system structure.

Fig.5 Diagram of mine integrated automation system structure

2.1.1 Layout of ONU

ONU is the key equipment of the PON,which affects the state of communication of network. Each piece of subsystem information by RJ45 or serial port is allowed access to the PON and should configurate POS and ONU as close as possible.

ONU should configurate in air compressor room which has ventilation,water pumping stations and other places related to the production safety,and the equipment should be protected effectively[13]. At the same time,various automation subsystem,industrial TV system and digital voice information could be transmitted to the center monitoring. Table 1 is the layout of the underground ONU.

Table 1 Layout of underground ONU configuration

2.1.2 Layout of OLT

OLT is the core of PON system,and it is arranged in the center of control room. In view of the important position of OLT in PON system,design of the PON uses 2 OLTs to form of 1∶1 backup. Each OLT supports up to 256 ONUs,and the farthest distance is about 20 km. In order to ensure the network reliability,the redundancy devices of OLT are used to switch to ensure network uninterrupted.

2.1.3 Network management

In order to ensure convenient maintenance and use of the network and normal communication function,the serial ports serve to manage the whole net. This design embraces automatic mode and manual mode,and automatic mode can be used when the system is in normal operation; and the manual mode is switched when the system is in the maintenance,overhaul and expansion.

The network also has redundant Ethernet and serial transmission interface for mine future system upgrade or some new systems installation.

2.2 Design of software platform

2.2.1 Integrated software system

The software platform is the core of mine integrated automation system platform,which can ensure each paru of the system coordinated operation[14].

Construction of the platfosm adopts SCADA software. Through the OPC software interface technology and othes software platforms such as the personnel positioning,industrial television system integrated into the platform,we can build up unified monitoring platform software. Other software platforms are integrated into this platform through the OPC software interface technology to build up unified monitoring platform softwase. Man-machine interface through this platform (HMI) can real-time monitor the equipment condition of subsystem and can be used to control each subsystem of I/O. System leaves enough space to expand and facilitates the subsequent system to upgrade. Fig.6 is block diagram of the system software simulation.

Fig.6 Block diagram of system software simulation

2.2.2 Software function

Through the integrated software platform,the interface integration of upper monitor adopts the set of comprehensive HMI which can switch to each subsystem. In order to realize the integration of management and control system,the mine control center should receive the real-time data that can carry out comprehensive analysis and process the information.

This design uses a new algorithm,which makes the comprehensive analysis of the equipment running status and historical state corresponding to make some prediction and alarm of equipment. Engineers can process the corresponding operation according to the system prompt with those on-site equipments measured by the automatic system of data.

2.3 Access to subsystem

2.3.1 Access to video system

The wide applications of digital video system make the image transmission quality greatly improved; digital video can be transmitted with Ethernet to reduce construction cost. According to the actual mine requirements,several digital video cameras can serially be connectted according to the actual situation,and the transmission of video information can be allowed access to the nearest ONU. Ultimately,it will reach the real-time display in the central control room TV wall.

2.3.2 Access to voice system

Due to the telephone,PHS system is a realization of the data exchange to complete communication network system. As long as access to the network switch with recent ONU connection can realize voice system.

2.3.3 Data access device

The underground substation,pump station and transportation system via Ethernet interface to access PON[15]. Realization of remote monitoring,control of equipment data,preservation and processing the corresponding device data are included in the integrated processing platform.

3 Conclusion

This article designs the set of mine integrated automation system based on PON access technology. PON system adopting Ethernet frame structure can also be seamless docking with the Internet of the ground to form a unified network without the need of transformation among the formats,so we can improve the operation efficiency and reduce the management cost of the system. It can be well integrated of integrated automation system of each subsystem. The stability of transmission can also achieve the purpose of saving transmission line laying and reducing maintenance cost by improving communication speed.

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