Control of ITH percussive longhole drilling in hard rock

This thesis aims to develop a comprehensive strategy for automatic control of the ITH percussive drilling process. Such automation would provide the benefits of improved productivity and quality in terms of penetration rate and hole deviation, as well as enhanced hole quality and machine life.Analysis of field data acquired from drilling experiments performed at INCO's Little Stobie Mine is presented. As a result of this analysis, a control algorithm is formulated to enhance the drilling process efficiency. This algorithm calculates the specific energy (SE) of the rock and adjusts the applied feed force based on this SE value, using a relationship obtained from the field data analysis.A model of the percussive drilling process is developed and simulated in software. The proposed control algorithm is tested through simulations on this simulated drilling process. The results of the simulation show a significant increase in efficiency of the drilling process.As a result of vibration data analysis it is concluded that vibration should be controlled through an improved design of the shock-absorber, rather than through drilling variables. A detailed shock-absorber test data analysis is therefore presented. Recommendations for design changes in the shock-absorber are also given.Deviation analysis is also presented in the thesis, which shows a poor correlation between the machine variables and the hole deviation data. Hence, it is recommended that deviation be controlled by steering. An innovative guided drilling mechanism for controlling the hole deviation is also proposed. This mechanism consists of an eccentric ITH percussive hammer with controlled rotational speed, which can be employed as an actuator to steer the drill string in a desired direction without using any down hole instrumentation. Modelling and simulation analysis of this system is also presented