In rock excavation processes, hydraulic rotary-percussive drilling is used for drilling and blasting in both surface and underground drilling operations. A hydraulic percussive drilling system is composed of percussion, rotation, feed, and flushing functions. In this paper, we detail the interaction of feed and rotation functions using a rock model. The feed actuator is a cylinder drive and a hydraulic motor actuator rotates the drill bit. The feed is force controlled and rotation is torque controlled by a feed reduction valve acting on the pressure compensator of the mobile hydraulic proportional directional control valve. In addition, in this work an individual load sensing variable displacement pump is used for both hydraulic functions. A suitable rock model is developed and verified against a measurement set. The inputs of the rock model are percussion drill flow rate, percussion pressure, feed force, and rotation torque, and the outputs are drill bit penetration rate and rotational speed. The modeling work is carried out to enable intelligent rock drilling control system development for changing rock conditions. The simulation results obtained verify that the simple rock model emulates various rock characteristics ranging from extremely hard rock like granite to softer minerals and that the changes in drilling parameters were as expected.

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