Most blasthole drills currently used in the mining industry are manually controlled. The drilling control systems which do exist are based mainly on ladder programming logic techniques. This thesis presents a comprehensive strategy for the automatic control of blasthole drills, based on closed loop feedback control approach.; A detailed model for the controlled process consisting of the drill rig's mechanical actuators, machine structure, and the drilling process at the bit-rock interface is presented. The model equations are refined and validated by experimental (field) testing. The instrumentation of an Ingersoll-Rand DM-45E drill rig and the subsequent drilling tests in a limestone quarry are described, with an in-depth discussion of the field tests results. Analysis of the field tests data establishes the dependencies between the drilling variables and ground conditions during actual drilling. The transfer functions of the mechanical actuators of the machine are also identified.; A strategy for automatic control of feed pressure and rotary speed is proposed. The controller is tested and tuned by interfacing it to a software simulator of the controlled process which implements the relationships identified from field testing. Simulation results are presented and analysed.; Results of implementing the controller on a Gardner-Denver GD-120 electric drill, and an Ingersoll-Rand DM-H hydraulic drill at two surface coal mines in British Columbia, Canada, are also presented. These results validate the drilling controller design and tuning.; The thesis concludes with suggestions for future research and refinement of the control strategy.
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