> GPShomepage > GPSpaper
> GPShomepage > GPSpaper
A
Low-cost GPS-based Locomotive Tracking System
R. K. JHA, K. K. MALLIK, S.JHA & T. WILLEMS
Abstract
Integrated steel plants rely heavily on rail transport infrastructure for the transportation of goods within the plant. Generally, this network encompasses the entire plant premises, connecting all major shops and stockyards. Smooth functioning of this network has a substantial impact on the overall productivity of the plant. Material tracking and fleet management of locomotives always poses a stiff challenge to the traffic department which operates the rail transport infrastructure on a continuous basis. Managing this infrastructure can be eased and can be made more efficient through the installation of a GPS-based locomotive tracking system (LTS). Based on the typical organisational structure of an integrated steel plant, a customised LTS system has been designed to solve this perennial problem. The installation of a few small stand-alone LTS systems, each concentrating on a different area of activity, appears to be the most economical option. This also allows the use of VHF radio links for the data exchange. While the proposed system typically costs twice more than a conventional voice only VHF network, its benefits can be more easily quantified. Its cost-benefit ratio is particularly persuasive when the much higher installation cost of radio trunking systems is taken into account.
Key words: telemetry, fleet management, Location Based Services (LBS), steel plant, locomotive.
1.
Introduction
Rail transport forms an integral part of any integrated steel plant’s operation. The raw materials, the intermediate and the finished products all move on rails because of their heavy weight. Managing this infrastructure is a complex task.
Consider, for example, the Bokaro steel plant. This 4 million tonnes integrated steel plant has a fleet of 60 locomotives (see Figure 1). There are about 50 locomotives in operation on a 24x7x365 basis. In the period of one hour, each locomotive consumes about 18.08 litre of diesel and about 0.57 litre of oil. One locomotive run-hour, i.e. running one locomotive for one hour, costs about Rs. 2000 in total.
The introduction of a GPS-based locomotive tracking system (LTS) can ease the management and ensure the efficient use of a steel plant’s rail transport infrastructure.
Figure 1. Left: Six ladles coupled to a locomotive.
Right: Close-up of a locomotive, with an indication
of scale.
2.
GPS-based Locomotive Tracking Systems
A basic GPS-based locomotive tracking system consists of one control centre and a number of mobile units. The mobile units, which are installed on the locomotives, determine their position using a GPS receiver. They communicate with the control centre in a wireless way. The control centre communicates with the different mobile units and offers location services to the end users.
In our application, the required accuracy for the locomotives’ position is about 50 meters, which can be achieved with just about any GPS receiver available off the shelf. The central station also needs reference position data of the rail track network over the entire steel plant as well as point of interest data along the rail tracks such as the position of the blast furnace, rolling mill, coke ovens etc. This data can be collected using a hand-held GPS receiver with the facility to record waypoints along the rail tracks. This data can then be overlaid on a map with the help of GIS/mapping software such as ArcViewTM, MapInfoTM etc.
In very general terms, the control centre’s function is data management and dissemination of location services. Location data, geocoded data or map data needs to be managed and manipulated at the control centre in order to provide various services to the users. The technical requirement for geoencoding services can vary from uncomplicated to demanding. Our requirement in this locomotive tracking application is simple: one should be able to know where the locomotives are located and in which direction they are moving.
The most costly part of the LTS system is the communication link. Various means of wireless communication could be used: VHF/UHF radio links, cellular telephony, satellite based data communication systems such as ORBCOMMTM etc. The means of wireless communication can be used in two ways: a continuous or a polled setup.
In a polled setup, the central station requests position reports from the mobile units. When the position of a mobile unit is required, the central station sends out a request to that particular mobile unit, which replies to the central station with a position report. The central station is able to retrieve the position of all mobile units by means of two-way communication between the central station and the mobile units.
In a continuous setup, the mobile units send a position report to the central station on a regular basis. As a result, a recent position report of each mobile unit is available at the central station at any time. Only one-way communication, i.e. from the mobile units to the central station, is required. However, special care should be taken to prevent simultaneous transmissions. A solution to this problem could be based on the synchronisation in time of the mobile units by making additional use of their GPS receiver for accurate synchronisation.
3.
Steel Plant System Requirements
The
organisational structure of the traffic department at the Bokaro steel plant is
depicted in Figure 2.
The
head office takes major decisions such as locomotive allotment, repairs,
fuelling etc. whereas the branch offices carry out the day-to-day operations.
The branch offices give instructions with regard to the movement of the
locomotives and assigns them specific work.
As
can be observed, the traffic control facilities are scattered around the steel
plant, each catering to specific needs. For example, one group of locomotives
may be working in the rolling mill area, another group in the blast furnace area
and yet another group at the coke oven shops etc.
Each
group of locomotives is controlled by a specific traffic office, typically
situated near the area of operation. The traffic department is not an isolated
department but works in close co-ordination with the production shops. This
close interaction and interdependence leads to decentralised multiple traffic
offices around the steel plant.
Considering
this typical organisation, the installation of a few small stand-alone LTS
systems appears to be the most economical option. A GPS-based LTS system will be
located at each of the branch offices. This essentially justifies the need for a
low cost system with one control station and 10 to 15 mobiles. The coverage
radius should be about 10 km, the infrastructure set up costs should be low and
its operation should require little maintenance.
Figure 2. Organisational structure at the Bokaro steel plant.
4. A GPS-based LTS System using VHF Links
Considering
all the above, data communication through VHF links was chosen for our
application. All
the VHF radios will operate on the same frequency in simplex mode. The control
centre only needs to be equipped with a single radio.
Because
of the use of VHF links, the infrastructure set up cost is low. It has been
observed that a comparable two channel MPT-1327 based trunking system would cost
ten times more than this simplex system. This is because of the multi-channel
requirement (control channel and data channel) of the trunking system. Such type
of system is recommended for large fleets where the infrastructure costs can be
justified, but not for smaller fleets where a simplex system provides the best
price/performance ratio.
In
addition, a two-channel trunking system requires four frequencies whereas the
simplex system requires just one spot frequency. Frequencies, being a natural
resource, are very costly and acquiring multiple frequencies from government
agencies is also more difficult compared to a single spot frequency.
Although
VHF radios operate on line-of-sight, their range is sufficient for our
application. As a rule of thumb, VHF radios with a 25 watt RF output have a
range of up to 25 km, depending on antenna height and gain. Another advantage of
VHF radios is that they can still occasionally be used in voice mode. The data
mode will obviously be inhibited during that period of time.
The
heart of the simplex system is the control centre which runs tracking and
mapping software. It is interfaced to a VHF base station operating on any
simplex dedicated radio frequency. The control centre communicates with the
mobile units and records position information. Each locomotive is equipped with
a mobile terminal unit (see Figure 3). The terminals can receive short messages
and send pre-programmed short messages back to the control centre in addition to
position reports based on their GPS receiver’s output. The mobile terminal
units also have several inputs/outputs for telemetry of vehicular status
sensors. The mobile terminal units interface with a standard commercial VHF
transceiver.
Figure 3. System architecture of a GPS-based LTS system using VHF links.
5. Real-life Deployment Scenario at the Bokaro Steel
Plant
We
will briefly present the deployment of such a system in one such zone at a steel
plant. There are 5 blast furnaces at the Bokaro steel plant. Every 8 hours, each
of the blast furnaces is tapped for hot metal and liquid slag. The liquid slag
is transported in slag ladles to the slag granulation plant, where it is
granulated into tiny slag modules. This slag is a useful by-product and is sold
to cement plants where it serves as an important raw material.
In
this area, a total of 150 slag ladles are in circulation at any given time. The
dry weight of each ladle is 15 tonnes and it can carry slag of 15 tonnes in
weight (see Figure 1). The average circulation time of a ladle is 5 hours from
blast furnace to slag granulation plant and back to blast furnace. About 10
locomotives are operating in this area on a 24x7x365 basis, which amounts to a
total of 240 run-hours per day. Recall that the total cost of one run-hour is
about Rs. 2000.
Effective
deployment of LTS systems can suitably reduce the locomotive run-hours besides
improving the operation and maintenance effectiveness of the steel plant. For
instance, a 10% reduction in locomotive run-hours per day would lead to a
benefit of approximately 24x2000x365=175 lakhs per annum.
GPS-based LTS systems for steel plants as introduced above can lead to optimisation of fleet size, increase in productivity and reduction in locomotive run-hours and fuel costs. The proposed system typically costs twice more than a conventional voice only VHF network, but with more quantified benefits, leading to its justification on the return on investment scale. The design of the LTS system is such that it can be deployed alike two-way radios. It is easily extendable while its cost remains proportional to the number of mobiles.
The need for such a low cost LTS system can not be more justified than for a developing country such as India. The lower the cost of such systems is, the more widespread its use will be. This follows the continuing trend in industry towards the widespread combined use of GPS and Location Based Services (LBS).
7.
References
- Blacksher Steve & Foley Tom, “Boulder HOPs Aboard GPS Tracking”, GPS World, January 2002.
- Kealy Allison, Scott-Young Stephen, Leahy Frank & Cross Paul, “Intelligent Navigation, Inertial Navigation: Double Assistance for GPS”, GPS World, May 2002.
- Magon Ajay & Shukla Reena, “LBS, the ingredients and the alternatives”, Proceedings of The Asian GPS Conference 2001.
- Proietti Mario, “Carrier Choices in Location – The System Integrator’s View”, GPS World, March 2002.
- Verma Kartikeya, Montu Kr. Amit & Anand V. K., “GPS based truck dispatch system at West Bokaro collieries”, Proceedings of The Asian GPS Conference 2001.
- Willems Tom, “GPS Dial-up Project”, Report for the Research and Development Centre for Iron and Steel, August 2002.
> GPShomepage > GPSpaper