Comparative Modeling, Simulation, and Control of Rotary Blasthole Drills for Surface Mining

Abstract

Most rotary blasthole drills used in the mining industry today are equipped with automatic control systems. However, few, if any, implement closed-loop feedback control of the drilling process itself. This thesis investigates the potential for such control on a large rotary electric blasthole drill. The control strategy examined is Proportional-Integral-Velocity (PIV) control. The drill was successfully equipped with a data logger, and a comprehensive set of drilling data was gathered at an open pit taconite mine in northern Minnesota. This data set was used to model the dynamics of both the feed and rotary actuators. A drilling process software simulator, based on hydraulic blasthole drill data originally developed in previous work [Aboujaoude 1991], was successfully replicated in Simulink, and thoroughly documented, overcoming a major shortcoming in Aboujaoude’s work which provided incomplete information on the simulator implementation. The control strategy from the previous work was successfully integrated with the new process simulator, and its performance validated by comparison with the results presented in the previous work. The drilling process simulator was then modified by replacing the actuator dynamics with the models identified for the electric drill. The modified simulator was validated, and the behaviour of the system with the new actuator models while under feedback control was observed. The controller gains were re-tuned to achieve acceptable drilling performance with the new actuator models. This resulted in a prototype controller ready for field testing on the large rotary electric blasthole drill. In addition, this thesis has produced a fully documented drilling process simulator, suitable as a platform for future research.