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Autonomous mine truck.

During Minexpo '96, visitors were able to see, either by satellite link to the Caterpillar booth at the Las Vegas exhibition or on-site at Cat's Tinaja Hills proving ground near Tucson, the Caterpillar Autonomous Mine Truck (AMT) concept. Two 777C trucks went through their paces as driverless machines demonstrating the flexibility and safety of the system that has been developed.

The AMT system employs Global Positioning System (GPS), high-frequency radios, computerised fleet management and navigation, obstacle detecting radar, as well as Caterpillar's Vital Information Management System (VIMS) to control, monitor and report truck performance.

However, mining companies cannot yet go out and develop new open pits with no thought to the hiring of truck operators. Caterpillar chose Minexpo to officially announce the 793C AMT (218 t capacity) development programme. The company intends to have "793C AMTs in developmental testing at numerous North American mine sites during 1997 and 1998. New versions will incorporate more accurate sensing devices, improved system durability, as well as offer improved user interface and upgradable system architecture." The 793C AMT is expected to be commercially available in 1999.

The first commercial machines will still have an operator's cab. Eventually, as driverless trucks are further refined and become accepted, it is expected that there will then be an opportunity to radically rethink truck design and make much more productive use of the space that is lost and extra machine weight that is added in providing for operator comforts. Without an operator and facilities for an operator, a redesigned truck, of the same empty vehicle weight as an operated unit, will be able to carry much more material, greatly lowering cost per tonne.

AMT development to date has been a steady, cautious programme - operating, without drivers, machines that weigh approaching 400 t fully loaded is not something to be taken lightly. Caterpillar first demonstrated the AMT concept on a 136 t capacity 785 in the late 1980s. Systems have been constantly updated since then as control technologies improved. However, it was 1994 before access to a complete and reliable GPS satellite constellation was available. The two 777Cs seen at Tinaja Hills were first operated autonomously in production at a limestone mine in Texas during 1994 and 1995. Here they successfully and safely hauled over 5,000 production loads on a 4.2 km cycle, further proving the concept.

The AMT is a hauler operating without a driver that uses the latest in navigational and control technology to travel a desired route. GPS pinpoints the truck's position and on-board systems control the truck and respond to dispatching commands. The AMT relies on the Navstar GPS of 24 satellites to calculate the truck's location to within 1 m through the use of triangulation and a Differential GPS receiver that serves as a known reference point. Differential correction allows the trucks to accurately navigate haul roads. Three different computer subsystems communicate with each other to control the AMT.

The on-site control system manages scheduling, routing and truck operations. On-board sensors and computers control speed, gear settings and other functions. The VIMs protects the truck in the absence of the operator.

Since the system requires no buried wires or sign posts, it is very flexible. Through this flexibility and the GPS technology, the course can easily be modified to match changing faces where the truck must load and changing dump points. The system can be customised for virtually any mining operation.

Front- and rear-mounted radar units on the truck detect obstacles, or people (anything taller than 0.5 m) and the truck will stop. Equally, should any of the systems fail, for example GPS loss or data transmission loss, the unit is automatically and immediately shut down. Thus, most of the safety concerns have been eliminated. If an obstacle detection stop occurs, the foreman can instantly reset the truck (remotely from his vehicle) after moving the object or determining the obstacle is no longer present.

GPS is going to have a very significant impact on surface mining operations in a short time. As Caterpillar group president, Glen Barton, stated recently: "The combination of information technology and GPS technology is a new milestone in mining and earthmoving technology. Benefits for the customer will be reduced surveying manpower, less machine idle time and improved job quality resulting in a lower cost for the movement of material."

Caterpillar will be developing other GPS-based products under its agreement with Trimble Navigation. These include, according to Glen Barton, "loaders with orebody displays, which allows operators to select ore grades and ore zones for mining ...and a bulldozer with grade slope and productivity displays to help an operator carry out the engineering plan for the mine."

The capabilities

The AMT demonstration at Tinaja Hills has the two trucks being loaded by a wheel loader, then travelling on an almost circular haul to the dumping point behind the loading area. Caution is still the side to err on so although the trucks are running at 40 km/hr on the straight, they are still programmed to take corners slowly.

Arriving at the dump point, the trucks stop 0.46 m from the edge of the 'crusher', the ideal spot. This demonstrates one of the advantages of autonomous operation, the truck can be programmed to employ 'best practice'. Thus it will always be in the best location for a specific circumstance or task, and through consistent 'best' operation, component life should be longer than with an operator.

Once the trucks have completed the circuit from loader to dump and are empty again, they return to the loader, awaiting the loader operator's signal to approach for loading. In a production mining situation, the loader operator's signal would also alert any other AMTs in the queue to move forward one space in the line. The loader operator also signals the truck when it is full and can move off. Thus, effectively, one operator is controlling his loading tool and all trucks assigned to it.

At the start of operation, the truck completes a self-diagnostic check before signaling the foreman that it is ready to work. Should the route for any truck requiring changing, this is a simple task. The fleet manager drives the new route in his vehicle (a pick up for instance). This provides the X,Y and Z coordinates and these GPS data are transmitted to the fleet management computer to establish a new route file. In the Tinaja Hills demonstration a new route, involving a number of S-bends, was quickly established, and the truck followed it perfectly. Changes in the mining face are handled by the GPS system on the loader.

As required, AMTs can be operated by remote control, for instance to reverse a unit into a workshop. They can, of course, under the current system, still be driven manually as well.

The advantages

Best practice operation is one great advantage of the AMT, but there are others. Doing away with the operator is a significant cost saving. In the U.S. some 20% of the total hourly operating cost is accounted for by the operator. In remote locations this also means a significant reduction in the personnel complement that has to be housed.

The consistent performance of the AMT is maintained despite low visibility, throughout long work shifts and through lunch breaks and the like. Overall, Caterpillar estimates the AMT will cut operating costs by 10-15%.

Briefly summarising, the advantages over manned trucks include:

* Reduced labour costs

* Increased production time due to the elimination of shift changes, operator breaks and other non-productive time

* Improved component reliability and wear life due to consistent operation within the truck's operational specifications

* Capability of working in adverse conditions, such as fog, dust or rain that would normally impair an operator's visibility.

* Updates truck performance data regularly so maintenance and repairs can be scheduled to avoid costly downtime

In a related development, Caterpillar is purchasing a controlling interest in Aquila Mining Systems. Aquila is a pioneer in the development of advanced software and monitoring and control systems for blasthole drills and cable shovels. These systems automatically interpret rock types from monitored drill data, calculate the effort required to excavate rock and provide precise positioning capabilities for drills and shovels based on GPS technology.

Major advances in surface mining embracing autonomous operations, safer operating conditions and lower downtime are largely being driven by GPS. Jim Sorden, Trimble's executive vice president for surveying and mapping recently noted in the National Mining Association's (U.S.) Mining Voice, that: "The heavy equipment market is without a doubt one of the most exciting new avenues for GPS integration."
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Title Annotation:automated surface mining equipment
Author:Chadwick, John
Publication:Mining Magazine
Article Type:Product/Service Evaluation
Date:Nov 1, 1996
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