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Robotic miner brings economic and environmental benefits

   
 
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Three partners have created a robot capable of recognising and selectively cutting minerals in a potash mine. The robotic mining machine is a conventional roadheader controlled by a computer. A video image of the rock face is processed to map the distribution of minerals which are then cut in a sequence planned to minimise the final cost of bringing the potash ore waste to the surface. The robotic cutter proved more efficient than human operators in discriminating between ore and waste, with important economic and environmental benefits.

The work of the miner is one of the most difficult and dangerous in the world. It calls out for automation, yet robotic technology has made little headway in the mining industry. Until now there has been no substitute for the hand and eye of a human being in the efficient extraction of minerals.
It is not hard to see why. Most industrial robots, such as those on car assembly lines, work on repetitive tasks in carefully structured and controlled environments. Conditions in a mine, on the other hand, could hardly be more different - heat, jolts, vibration, dust - with constantly changing surroundings as the cutting proceeds. Moreover, the miner - whether robot or human - must recognise the difference between seams of valuable ore and worthless waste, and ensure that one is extracted and the other discarded.
Despite these challenging problems, this project, involving three partners from Spain and France, is a continuation of a project funded by the EC Raw Materials Programme to develop a robotic cutting machine for use in mines. The project was centred on the Potasas del Llobregat potash mine in Sallent, Spain, which supplied an existing 'roadheader' mining machine to be modified for robotic working. Most of the development work was done by the project leader, AITEMIN, a mining technology research centre in Madrid, in cooperation with LAAS-CNRS, the national Laboratory for Automation and Systems Analysis at Toulouse.
The roadheader was a 95-tonne Vöest-Alpine AM-100, a tracked vehicle with a cutting head attached to a long boom. In manual operation the vehicle is positioned in front of the face and the operator cuts the rock by eye, moving the cutting head with controls in the cabin. About 40 cubic metres of rock can be cut before the vehicle needs to be moved forward.
For robotic control an industrial VME computer was fitted on board the vehicle, protected against dust and cooled against the 38C temperatures found in the mine. It was linked for monitoring purposes to another VME on the surface four kilometres away.

Video cameras create a face map

An early problem was how the machine could 'see' the rock face and identify the different minerals. After experiments with mapping gamma radiation over the face (potassium salts are slightly radioactive), and investigating the use of microwave absorption and other techniques, the team decided that visual mapping was likely to be the fastest and most efficient method. To cover the 45 square-metre face in sufficient detail (some of the layers of clay between the seams are less than a centimetre thick) four video cameras were positioned on the roadheader, grouped in pairs, each pair with its own integral lighting. A major success of the project is the creation of software to fuse the four overlapping images to make a single 'face map' of the rock in front of the machine.
Next, the computer analyses the map to identify the different minerals and their precise boundaries. The potash ore in the Sallent mine is a reddish mineral known as sylvinite, a form of potassium chloride. It is found in two layers separated by orange-coloured halite (rock salt) which is not needed. A poorer quality potash ore, carnallite, is also present but regarded as waste.
The computer finds the boundaries between the various seams, and identifies them primarily by colour and texture (sylvinite is redder and more coarsely layered than the others) with the assistance of neural networks. The final face map then shows the precise location of the various minerals in front of the roadheader.
Based on the map, the planning module decides the most cost-effective way to cut the minerals so that the final cost per tonne of mined potash is as low as possible.

Catching up with the robotic miner

In the Sallent mine the cut minerals are carried away from the face by shuttle trucks and the sylvinite taken to the surface by conveyor belt while the waste is deposited in worked-out caverns within the mine. A major problem of efficiency is that the roadheader can work faster than the trucks can remove the minerals, and it often has to stop cutting to wait for the next truck. One aim of the planning module is to minimise the number of trucks needed by ensuring that, as far as possible, each one is filled to capacity and the waiting time is reduced.
Finally, the computer controls the movements of the cutting head, much like a robot arm, excavating the different minerals according to the plan. Normally the rock salt is removed first, followed by the sylvinite.
The robotic roadheader is capable of excavating the entire face unattended - some 35 tonnes of rock - but it has to be paused manually to ensure that the trucks are in position. Where the seams are uniform the machine can automatically move forward for the next cut, but manual positioning is still required where there are changes of seam thickness and slope. The problem of automatically navigating a roadheader along a seam has not been addressed in this project.

A money-saver with environmental benefits

Trials at the Sallent mine were a great success. The robotic roadheader proved to be better than human beings in discriminating and cutting the different minerals. The economic advantages of this are clear - no mining company wants to spend money bringing waste material to the surface, and clean ore naturally fetches a higher market price than contaminated ores. The environmental benefits are equally obvious, as there is ultimately less waste to be disposed of on the surface.
While research into automated mining is going on elsewhere in the world, notably Canada, the partners believe that their robotic roadheader is the most advanced of its kind.
Possible spin-offs include using the image-processing software by itself to make geological analyses from photographs of mine faces, and using positional data from the roadheader to make three-dimensional models of mine workings with accurate estimates of the amount of each mineral present.

An idea whose time has not yet come

The project has been stalled since the EC contract was completed in 1994. With the European mining industry suffering from recession and restructuring, industrial development of a robotic roadheader is not seen as a high priority. AITEMIN believes that robotic technology, while desirable, may be too sophisticated for an industry traditionally reliant on simple, robust and easily maintained equipment. Ten years hence the outlook may be different, but for now the robotic miner remains an idea whose time is still to come.

 

Project Title:  
Robotization of roadheaders for automatic selective cutting

Programmes:
Industrial and Materials Technologies (BRITE-EURAM/CRAFT/SMT)

Contract Reference: PL-55

Cordis DatabaseFor more information on this project,
go to the CORDIS Database Record

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