An Adaptive Nonlinear Control Design for a Rotary Drilling System with Stick-Slip Oscillations

Drill strings, which are a component of rotary drill rig in oil and gas exploration, are flexible rotor systems. One of the main concerns about drill strings is stick-slip oscillations. In order to eliminate such vibrations, a second order dynamic model of a drill string has been chosen to design an adaptive nonlinear backstepping controller. The dry friction model is used to demonstrate the torque on bit. It is essential for the controller to be adaptive since the model to describe the torque on bit contains uncertain terms. Results indicate that the adaptive controller has an appropriate performance regarding the response time and tracking behavior. It is concluded that this control strategy can be applied to higher order models of drill strings in order to suit for more realistic applications.