HOSM control of stick-slip oscillations in oil well drillstrings

This paper presents a technique to control torsional oscillations in oil well drillstrings based on switching systems. The main idea of this work is to design a Sliding Mode Control (SM) to suppress the limit cycle responsible for stick-slip oscillations on oil well drillstrings. To achieve this we first design a Sliding Mode Control (SMC), that induces a sliding bifurcation on the system and eliminates stick-slip oscillations. However, this method introduces undesirable chattering behavior. In order to avoid chattering a Higher Order Sliding Mode (HOSM) control is proposed. Simulation results comparing these two controllers are shown.