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 oiland gas exploration, are flexible rotor systems. One of themain concerns about drill strings is stick-slip oscillations. Inorder to eliminate such vibrations, a second order dynamicmodel of a drill string has been chosen to design an adaptivenonlinear backstepping controller. The dry friction model isused to demonstrate the torque on bit. It is essential for thecontroller to be adaptive since the model to describe thetorque on bit contains uncertain terms. Results indicate thatthe adaptive controller has an appropriate performanceregarding the response time and tracking behavior. It isconcluded that this control strategy can be applied to higherorder models of drill strings in order to suit for morerealistic applications.

Keywords:

Drill string , Dry friction , Stick-slip , Adaptivebackstepping control