Closed Loop Speed Control of DC Motors used in Rock Drilling and Mud Pump Application

This paper deals with closed loop speed control of DC motors used in rock drilling. Drilling is the most important part of exploration geology. It is also used for exploration of crude-oil. Drillability of rock mass is the resistance of different rock materials against drilling, controlled by various technological and geological properties. Furthermore, the wear of the drilling equipment may be a severe factor of costs in exploration geology as well as in exploration of crude-oil. When drilling operation encounters various rock types of different drillability, then the necessity of speed control of drill bit comes into account. The closed loop PID control strategy is helpful to regulate the speed of drill bit as well as mud pump. When the drill bit cuts the hard rock without speed variation then maximum heat will be produced due to higher friction with the rock. This overheating of drill bit is one of the main causes of bit failure. In case of hard rock, the speed of the bit is less and torque requirement is more for sustaining the costly drill bit. On the other hand, more chemical mud pressure is required to control the temperature of drill bit. This chemical mud pressure is generated from mud pump which runs at higher speed. The speed of the drill bit must be reduced and at the same time speed of the mud pump will be increased by the proposed scheme. The operating circuit is simulated using PSIM software. The simulation results are plotted and shown feasible for real implementation. The entire TRIAC based speed controller system must be understood before applying geological expertise to the solution of expected or developing drillability problems.