Open Cut » Overburden Removal
Reduction in the cost of overburden removal from open cut coal mines has been identified as the most important means of improving the economic performance of Australian open cut coal mines. The automation of the dragline dump cycle has been developed to improve the efficiency of this mining process. In addition to the potential productivity gains of the system, the constrained nature of computer generated control signals may lead to additional savings through reduced dragline maintenance costs.
The following have been demonstrated on the Bucyrus Erie BE1370W dragline at Tarong Coal's Meandu Mine.
- Coordinated computer control of dragline drag, hoist, and slew drives resulting in a system capable of moving the bucket between operator specified dig and dump sites through via points if required.
- Placing the bucket on the ground at the end of the cycle ready for the operator to fill it.
- Effective swing damping at dump and dig sites.
- Online estimation of bucket weight, which is used to determine when the bucket has emptied during dumping.
- Bucket recovery.
- Over 100 fully completed automated cycles.
- The system can match the performance of an operator under some digging conditions.
A major issue in this project has been dragline access for system testing. Testing of the control system's hardware and its sensors was performed without interruption to production and proceeded well. Testing of the controller required diverting the dragline from production. We over-estimated the dragline's availability for this form of testing. In practice we received permission to test on just 12 days in the period February to September 1998. A test day gave us control of the dragline for an average of 2 hours. While early dragline controller testing produced dragline productivity of almost zero, in latter testing production rose to greater than 50% of normal production.
The results achieved clearly demonstrate the feasibility of an automated dragline swing cycle but do not quantify the potential advantages to the mining industry. The true benefit to the industry of an automated dragline swing cycle can only be quantified after the following three issues are addressed.
Operator Interface The servoed operator controls of the existing system have been an outstanding success but the system's control and training interface needs to be developed to provide minimal delay in setup and operation.
Optimal Trajectory A bucked trajectory optimisation system is required to take account of the day to day variation in dragline performance and compute optimum (ie shortest time) bucket paths.
Productivity Study The Julius Kruttschnitt Mineral Research Centre (JKMRC) developed as part of the current project, methods for comparing the performance of different dragline operational strategies based on analysis of Tritronics monitor data files. These techniques need to be applied to a dragline fitted with an automated swing cycle in a production environment to determine the true benefit of such a system.
The current location at Tarong is extremely convenient for the researchers and considerable resources have been devoted to installation of equipment and developing a good working relationship with mine maintenance staff and dragline operators. However, if mine management can not provide in the order of 100 hours of dragline access spread over 6 months for controller testing, then the project will not continue at Tarong.