|
GPS based truck disptach system at West Bokaro collieries
General System Architecture [2] 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.  Fig. 5 TDS Control System Architecture Radio Network 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. The GPS system is described in detail in an earlier section. 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. 6 TDS Application Architecture DGPS Antenna 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. Wireless LAN 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. |