Mine control room for small and medium-sized mining companies
Fig. 1. // Bild 1. Staircase (1).
The MoSc (Modern SCADA System) mine control station developed at the TU Bergakademie Freiberg’s research and education mine Reiche Zeche uses modern, scalable software and has been designed to operate on a mid-range computer. Users have complete flexibility when it comes to the choice of peripheral device (computer, smartphone or tablet) to be used for visualisation. The software is platform independent and can easily be integrated into an existing company network. Data retrieval within the intranet is carried out in combination with a user ID while external access is achieved via an additional VPN client. The system has been designed for the integration and interconnection of all relevant underground processes as part of a “real-time mining strategy”. All the data are to be processed, stored and visualised in accordance with the requirements of a holistic mine process control system whose ultimate objective is to provide support for management decision making. To this end a number of different data classes were directly linked together, as shown in Figure 1.
Technology components of MoSc
MoSc was developed with the aid of various technologies that were designed to ensure both the scalability and the robustness of the system. These will now be presented below.
.NET Core, which was first released in November 2015, enables the development of applications for product distribution and marketing. Version 2.1, which also sustains other software architectures and was designed for long-term support, was released on 30th May 2018. This freely available and open-source software can be used free of cost. It is used for the development and execution of user programs and contains programming languages, tools and technologies for product development. The entire backend of the control room was developed with this software in order to achieve platform independence. The application package can be altered while the system is running without having to reboot (2).
Firebird DB is used as a database management system for the mine control station. It is both open source and industry approved and tested as it is the free version of a commercial database. .NET Core automatically generates the database structure, thereby reducing the IT skills required from the user on site (3).
Angular and WebGL are used for the browser-based front-end solution. Angular is a JavaScript-based language that was released as open-source software. It enables websites to be created that automatically adapt to the desired periphery (4). The 3D model of the mine plan can be incorporated using WebGL and then displayed with a web browser. Depending on the size of the mine plan, however, allowance has to be made for a time lag when generating the webpage (5).
OPC Unified Architecture forms the core of the data integration. It is a platform-independent, open-source communications protocol based on Ethernet technology. One of the fundamental innovations is the transition from master-slave architecture to server-client architecture, which allows the creation of a network in which each device has the ability to communicate and control. For this reason it is often designated as an important technology for the Internet of Things (IoT). Another significant advantage is the change in the data transfer process. The network is no longer swamped with data, some of which may not be needed, since this is now only sent to a user on request. This results in a more complex set of communication structures, which is why this communications protocol is not able to control real-time applications (millisecond range). In fact, it is much more useful for horizontal and vertical communication operations within a company, or in this case a mine.
OPC UA supports plug and play within its systems. Two services are provided in this context:
- Discovery Server – enables a server to register at a central point, whereby it can be automatically integrated into the communication; and
- certification – an optional validation process for OPC UA profiles that is managed by independent institutions.
Using MoSc
In order to use MoSc the OPC UA server first has to be started followed by the client. This initially opens the main screen for the user login. This is needed in order to provide each user with his or her specific rights of usage along with information that is specified via the aforementioned user ID. The various symbols and measurement data then appear on the mine plan, as shown in figure 2.
Fig. 2. MoSc – main display screen (1). // Bild 2. MoSc – Hauptbildschirm (1).
The points marked in green are active measurements that indicate the reception of data. The red points show that there is currently no connection (failure or delay). Frequently used sensors/units, such as gas sensors or fans, can be positioned by drag and drop with a few clicks on the main screen, this only requiring the sensor type and the IP address of the sensor to be keyed in. The new unit can be freely positioned on the mine plan. The exact position can then be stored once the mine surveyor has measured the precise location.
The tab cards along the edge of the screen allow the users to access their projects and data. The integration of both wired and wireless data transmission was successfully tested for the research and education mine Reiche Zeche facility. The tab card for the fibre rope test rig is shown in figure 3 by way of example.
Fig. 3. MoSc – fibre rope test rig (1). // Bild 3. MoSc – Faserseilversuchsstand (1).
The access rights of each user are determined on the basis of the user login referred-to above, with only relevant and approved content being put on display. The access rights of selected personnel are given below:
- The mine manager has access to, and full control of, all data. Naturally there are various tasks that can be delegated, however in the event of an incident occurring the manager always has full rights of access.
- By contrast, the electrical engineer only has write access to data that relates directly or indirectly to the power supply system. Of course these engineers will also have read access to all the other data for work planning purposes and for safety reasons.
- In the case of the esearch and education mine Reiche Zeche there is also another group with special rights of access, namely the scientific staff who run the projects. These employees have full access to their research laboratory and read access to safety-relevant information.
Data transmission concepts
As well as the “logical” transmission of data the information also has to be transferred physically from the measurement site to the target. In certain cases a cable-based transmission system is not possible, especially in remote and distant parts of the mine and/or where access is difficult. The Reiche Zeche research and education mine has therefore been testing various systems designed to provide the wireless transfer of measurement data.
Leaky feeder for mine roadway digitisation
The propagation of electromagnetic waves is defined by the electromagnetic properties of the rock, its porosity and the fluids it contains. Experiences with typical wireless transmission equipment, such as WLAN, have demonstrated that such systems can only be used for transmittance through mine workings if there is a visual connection between client and server (9). A new system was therefore developed in collaboration with Freiberg-based project partners IBeWa (Engineering Partnership for Mining, Water and Landfill Technology) that provides an efficient, wireless network coverage even in narrow and curving mine roadways. This concept has now been successfully demonstrated with the installation of leaky feeder antennas and Cisco W-Lan technology. The following tests were carried out:
- transmission distance trials;
- identification of limiting rock properties; and
- proof of an increased transmission range when using repeaters.
Through-the-Earth communication (TTE) for engaging remote measurement stations
Electromagnetic waves have been used for many years for the exploration of geological structures (e. g. ground-penetrating radar) and this technology is now taken to be the state of the art in science and technology (10, 14, 15, 16). The first development of TTE technology based on very low frequency waves (VLF) dates back to the 1920s, e.g. (7). Over the last ten years research and development has focused increasingly on concepts for using electromagnetic waves to transmit data through rock for mining applications (10, 11). One of the driving forces behind the development of this technology has been the need to monitor the pressure conditions in and behind impermeable underground sealing systems for mine shafts and galleries. One of the first installations for wireless data transmission, which in this case is equipped with three radio sensors for measuring pressure and temperature, has been undergoing successful trials at the Morsleben radioactive waste repository (ERAM) since December 2010 (10, 12). A further application commenced in 2019 with the installation of a radio sensor for a large-diameter borehole test aimed at investigating the use of MgO concrete for sealing shafts in rock salt formations (13). The radio technology used in these sensors (ultra high frequency – UHF) is optimised for the dry conditions present in salt mines. For this reason the Reiche Zeche research and education mine has started work on the development and testing of concepts based on TTE technology with VLF with a view to evaluating a system for transmitting data through wet Freiberg gneiss.
In the past the use of TTE was primarily focused on text-based communication. However, this technology has also the potential for bi-directional data transmission between a transmitter and a receiver (two-client connection). For this purpose an extension of the E-field communication system (ECS) is now being used for monitoring duties in the mine. This set-up can transmit pre-processed values of up to 228 bits per second at frequencies of between 40 and 132.6 kHz (6). A series of underground tests on the VLF-based data transfer system was carried out in mine roadways in order to optimise data transmission between boreholes by varying the antenna configuration and the electromagnetic coupling to the rock. Significant differences in transmission behaviour were identified when the antenna was installed in a borehole and at the rock face (Figure 4).
Fig. 4. Field tests with TTE cover (6). // Bild 4. Feldversuche mit TTE-Abdeckung (6).
A transmission range of over 140 m was only successfully achieved in large-diameter boreholes (BH1 and BH2, work done by the German Society of Geosciences (German Research Centre for Geosciences)). The specific transmission behaviour is determined by the specific resistance of gneiss, which is dependent on the water content and varies from 6.8 x 104 Ωm (wet) to 3 x 106 Ωm (dry), and the dielectric constant, which is about 8.5 to 10 times lower than that of water. The transmission process is mainly controlled by more highly conductive, wet anisotropies, such as joints and fissures.
Trial link-up of both technologies for comprehensive coverage at the Reiche Zeche research and education mine
Finally, a combined TTE/WIFI data transmission concept has now been developed with a view to transmitting monitoring data from abandoned underground roadways to an OPC UA-structured surface control room and demonstrating the operating viability of this technology. Figure 5 shows the linked TTE/WIFI equipment that has been set up in the mine for the transmission of various data types, including for example the LIBS (laser induced breakdown spectroscopy) measurement technology developed by Spectral Industries (1).
Fig. 5. TTE module in the Wilhelm-Stehender-Nord section (LIBS) (left), TTE module in the Glück-Auf-Spat section (T/p) (right) (1). // Bild 5. TTE-Modul am Wilhelm-Stehender-Nord (LIBS) (links), TTE-Modul am Glück-Auf-Spat (T/p) (rechts) (1).
In anticipation of future collaborative work the IBeWa and TU Bergakademie Freiberg have been looking at the potential of a fixed TTE demonstrator network capable of providing the mine control room with safety-relevant measurement data. The IBeWa is also pressing ahead with the development of miniaturised sensors for TTE-based monitoring in boreholes (1, 17).
References/Quellenverzeichnis
References/Quellenverzeichnis
(1) Krichler, T. et al. (2019): Real-Time Mining Deliverable – Report on Integration of central Real-Time Mining control cockpit from WP6 with ZG from task 9.1.
(2) Wikipedia .NET Core: https://de.wikipedia.org/wiki/.NET_Core
(3) Wikipedia Firebird DB: https://de.wikipedia.org/wiki/Firebird_(Datenbank)
(4) Wikipedia Angular: https://de.wikipedia.org/wiki/Angular
(5) Wikipedia WebGL: https://de.wikipedia.org/wiki/WebGL
(6) Horner, D. et al. (2017): Real-Time Mining – Deliverable – Advanced Mine Monitoring Control, Operation and Safety System for Small Scale Mines.
(7) Jakovsky, J. J.; Zellers, D. H. (1924): Factors Retarding Transmission of Radio Signals Underground, and some further Experiments and Conclusions. 2651, U.S. Bureau of Mines, Washington, D.C.
(8) Giese, R.; Jaksch, K. (2016): GFZ Underground Laboratory in the Research and Education Mine “Reiche Zeche” Freiberg. In: Journal of large-scale research facilities, 2, A68 (2016), 6 p. doi:10.17815/jlsrf-2-131.
(9) Grafe, F.; Horner, D.; Rössel, A.; Schieweg, A.; Viertel, T.; Wilsnack, T.; Mischo, H. (2018): Data acquisition & transmission in mining operations. In: Kali & Steinsalz, 02/2018
(10) MoDeRn (2013): Monitoring in Geological Disposal of Radioactive Waste – Objectives, Strategies, Technologies and Public Involvement. Proceedings of an International Conference and Workshop, Luxembourg, 19 – 21 March 2013
(11) IBeWa (2012): Non-destructive in situ permeability determination. IBeWa-Ingenieurpartnerschaft subsidized by the German Federal Ministry of Economy and Technology (BMWi) FKZ: 02E10447.
(12) Wilsnack, T.; Rössel, A.; Grafe, F. (2012): Kabellose Daten-übertragung im Salinar. In: Kali und Steinsalz, Heft 2/2012.
(13) ELSA-2 (2020): Kudla et al.: Schachtverschlüsse für Endlager für hochradioaktive Abfälle (ELSA – Phase II): Konzeptentwicklung für Schachtverschlüsse und Test von Funktionselementen von Schachtverschlüssen. Förderkennzeichen 02E11193A.
(14) Geyer, R. G. (1973): USBM Contract Final Report (G133023). Thru-The-Earth Electromagnetics Workshop. In: R.G. Geyer (ed.) Department of Interior, Golden, CO.
(15) Geyer, R. G.; Keller, G. V. (1976): Constraints affecting through-the-earth electromagnetic signaling and location techniques. In: Radio Science, Vol. 11, No. 4, pp. 323-342.
(16) Large, D. B.; Ball, L.; Farstad, A. J. (1973): Radio transmission to and from underground coal mines – theory and measurement. In: IEEE Transactions on Communications, Vol. COM-21, No. 3, pp. 194 – 202.
(17) Kosmos (2020): Entwicklung eines kabellosen Monitoring-Systems zur Langzeitüberwachung des Gebirgsdruckes. Forschungsvorhaben gefördert durch die Arbeitsgemeinschaft industrieller Forschungsvereinigungen „Otto von Guericke“ e. V. (AiF), FKZ: ZF4486501GR7 (laufendes Vorhaben).