Kartikeya Verma, Amit Kr. Montu, V.K. Anand
Communication Group, Automation Division, Tata Steel, Jamshedpur, India
Opencast coal-mines operate with periodic blasting and then excavations which in turn is followed by removal of Over Burden (OB) and retrieval of the coal. In the process of coal mining, two main sub processes viz. removal of OB and retrieval of coal are predominant. But most of the effort goes in the removal of OB and this has a dominant influence on the productivity. In the process of OB removal, two of the equipment viz. Rear Dumper and Excavator play a leading role. After the schedule of blasting in an specific zone of the mine has been prepared, the Excavator loads the OB into RD and each RD goes practically through four different machine states i.e. Waiting (near Loading zone), Loading, Full and Empty (at Dumping zone). This sequence of machine states of a RD constitutes one trip. Now it may be understood that to monitor the productivity automatically, one has to monitor the movement of RDs around the corresponding Excavator i.e. Loading zone to Dumping zone and back to Loading zone.
Using the facility of GPS Receivers, it is possible to find out the absolute co-ordinates of any mobile equipment. In addition the system incorporates load sensors, limit switches, RF Telemetry etc.
General System Architecture at West Bokaro Collieries
Tata Steel’s West Bokaro colliery is at present divided into 2 (two) Quarries viz. Quarry AB and Quarry E (fig: 1). Operation and Maintenance of both these Quarries are independent of each other. There is a total fleet of 70 Nos. of Mobile Equipment, out of which 14 are Excavators and balance are the Rear Dumpers. The whole fleet is almost equally divided into two; one for Quarry AB and other for Quarry E. Since the functionality of both these quarries are independent, separate Central Control Rooms have been set-up for each quarry viz: TDS Control Room for Quarry AB and TDS Control Room for Quarry E. Each Mobile Equipment has got its specific ID burnt in the firmware of its TDS Hardware installed on-board and this TDS on-board hardware comprises of an Intelligent RPU, GPS Receiver, Telemetry equipment and Graphical Touch Screen (GTS) on-board is used as the Operator’s interface, keying in delays / logins and viewing their assignments & productivity.
For the data transfer between the mobile equipment and the base server a radio network is installed. Prior to the radio-network design, a thorough radio survey was done to achieve a good understanding of potential bad coverage areas. There were several areas like at the wall of the cut or behind spoil piles and reject dumps. As landscape within a mine is dynamic and therefore it is planned that the radio coverage will be checked regularly. The performance of the system depends heavily on the successful data transmission from both sides i.e. data from the mobile equipment to the base station and from the base station to the mobile equipment. A poor radio coverage can lead to loss of data, which cannot be compromised.
Within the West Bokaro Mine two completely separate Radio networks have been installed one for quarry AB and one for Quarry E. To decide the height of antenna and place of antenna a radio survey was performed for both Quarries AB and E. After the survey it was decided that the base antenna for quarry AB will be mounted on top of the tower next to the control room and the base antenna for the quarry E will be mounted on top of the tower outside the control room.
The following diagram (Fig. 2) shows the radio network design and indicates the GPS system. This is the link for determining the equipment position and sending this information to the base. The on-board processor communicates with the GPS receiver and sends the equipment position via the radio network to the base. In the case of an excavator, this information is also required by the trucks, and the information is directly routed to them.
Each Quarry requires a radio-network of that type. Each radio network requires its own frequency. The network consists of both the Voice Communication and Data Communication. For Voice Communication we are using VHF band but for Data Communication it is the UHF Band. This is because the UHF band provides higher baud rate and more reliability for data communication, which is our requirement to run the system more efficiently, to obviate any concerns about data integrity. This is vital for the performance of the system.
Fig. 1: Site Map of West Bokaro Collieries
The DGPS is required to achieve a sufficient accuracy of the GPS of the whole quarry. The DGPS position on earth is acquired on initialization of the DGPS unit. Once the exact position is known the DGPS computes error corrections for the signal received from the satellites, and broadcasts these corrections via the radio network. All mobile equipment receiving them, take them into account on computation of their position.
The DGPS antenna is placed on the roof top to get the clear view of the sky in order to receive the satellite signals.
Fig. 2: Typical Radio Network
TDS information available at TDS Control room server is required to be distributed over the network of West Bokaro so that management also can monitor the productivity etc. This will make TDS system more useful because this way more and more people will interact with the system and share the information. It’s very difficult to lay a wired network to connect different offices to the Base station because there is uneven surface and also the structure of the mine always changes. So the wired Network is not relaible. To overcome this problem it was decided to go for Wireless LAN. It was planned to connect 5 nodes (offices) through the Wireless LAN. Now a person sitting in his office can browse the information through Internet Explorer.
The proposed WLAN is based on the Frequency Hopping Spread Spectrum technology.
Fig. 3: TDS Control System Architecture
Information Database & Server
In each quarry there are basically two Server programs running on two separate Machines. Apart from them there are Client Applications which can run on any number of machines .One Server called On-line-Server takes care of online data coming from field devices. One Serial port of this Server is connected directly to Radio network from where it receives data and other Serial port is connected to the DGPS for error correction of the Data coming from field. Other Server is called Off-line or Historical Server. This Server takes care of the Clients which are connected over network and also for storing online data coming from On-line Server in database The Clients are applications which shows the Data to end user in various easily perceptible forms.(refer Fig.3).This system is built on 3-Tier architecture.
3-Tier architecture consists of the following components.
Data base is where all the data coming from the On-line Server and also manually entered data by Clients is stored. In present case SQL Server 2000 is used as data base. Each Quarry is having its own database. However for generating composite reports both databases are accessed.
Fig. 4: TDS Application Architecture
Off-Line or Historical Server
Off-line server is the program, which interfaces database with clients. So all queries from Clients are directed to Database through off-line Server. Thus database is not directly accessible to Client. This secures database from unwanted alterations.
This is the application, which is distributed to all the Clients. This application consists of GUI, Reporting Module, Online monitoring Module, System Configuration Module and Manual Data Entry Module. GUI is the Map of the mine on which positions (Longitudes, Latitudes) as well different parameters of different on-line monitored HEMM’s are shown and updated as per actual movement of the HEMM’s. Reporting Module is used for generating different reports regarding performance of equipments. The system provides wizard as well SQL editor for making Report templates, which can be run at any time by entering criteria like date etc.
On-line Monitoring module is functionally similar to GUI except it does not show pictorial representation of the HEMM’s. In this module on-line data coming from field devices is represented in tabular form. System Configuration module takes care of various configurations as per the functionality required. This module is used only by System Engineers and all other users are not given access to this module. Data Entry Module is for entering data for non-monitored HEMM’s. So database contains information for all the HEMM’s. As a result reports coming out of system contain complete information of all the Mine Machines.
Although both On-line and Off-line Server Application can be on one machine (PC), but that makes system slow and also slow response to On-line Monitored HEMM’s whose speed is crucial. So for optimum performance of the hardware and software ,system (refer Fig. 4) contains two server, Off-line Server (Hardware ) and On-line Server (Hardware). Since On-line server gets information from field devices, so to ensure that data is not lost and response to On-line Monitored HEMM’s is sufficiently fast , this machine(PC) is generally of good configuration (RAM and Processor). Database also lies on this machine. The off-line server handles Clients, so that the client querries can be answered, without becoming slow. The Off-line server has high RAM. Any Client Machine on the network can run the Client application interfaces, TDS Online Console, TDS manual entry of data for non-monitored equipment and the TDS free format reporting system. Hence, the system maintains data integrity, while simultaneously permitting a wide range of user interactions and querries.
The implementation of the TDS spans multiple areas. These include TDS field hardware and operator software. The following tangible and / or intangible benefits are expected to accrued in the following different areas:
- TDS field hardware and operator interfaces:
All digital inputs of the TDS hardware capture key information like Engine Run Hours, Idle Hours, Over Temperature and Over Pressure, which will assist maintenance. Operators are provided with an easy to use interface. While the base system is in English, a limited number of stoppage and breakdown reasons are implemented as raster images [bitmaps], to assist the operators in the correct selection. Also Operators are provided with audio visual feedback with regard to messages from the base, loss of communication with the base, and GPS unavailability.
- TDS Online Console:
All mobile (RD&EX) equipment are viewed on a site map. All the RDs associated with a particular EX can arranged with the same color. The Key Performance Indicators (KPI) for the equipment can be viewed within a tabular list.
- TDS Manual Data Entry system:
The data for non-monitored equipment can be entered manually. To be able to record The fuel usage for equipment [vide the fuel truck], can be recorded manually. A limited data from the appropriate prep plant can be entered for use within the MIS system.
- TDS Free Format Reporting System:
An integrated data warehouse for all production equipment is provided within the mines. With this, suitable reports for each of the quarries is being generated. A single daily report on data collected by TDS across the two quarries can be provided (through wireless LAN).
Moreover some additional benefits are as follows:
- On-line Monitoring of Equipment
- Improvement in Production with pay back period less than one year
- Reduction in Operational and Maintenance Delays.
- USER FRIENDLY & Flexible Reporting System
- Ease of Re-deployment of resources during breakdowns
The GPS Based Truck Dispatch System implemented at West Bokaro Collieries is the first of its kind in India and has been a great success in achieving its objectives.
- Implementation of Engine Monitoring System (EMS) and Payload Monitoring System (PMS) and their integration with TDS
- Remote Monitoring of TDS through WLAN / VSAT Link / Internet.
- Implementation of Optimization algorithm for resource utilisation and facility of Automatic Dispatching
- Integration with Washery Plant for monitoring of Clean Coal Production.