Observer-Based Control of Drilling Mode in Rotary Drilling Systems

Algorithms for regulation of the vertical rate of penetration and the drilling power in rotary drilling systems are presented. The algorithms are designed under the assumption that the parameters of the rock-bit interaction are unknown. In contrast with the previous results, the algorithms do not require real-time measurement and communication of the downhole variables, such as rotational velocity, torque-on-bit, etc. This is achieved through the use of high-order sliding mode observers which estimate the required downhole variables based on measurements performed at the ground level. Simulation results are presented which confirm efficiency of the proposed control methods.