In this talk, we present some recent developments for estimating and controlling the torsional motion of a drilling device. We introduce first the stick-slip phenomenology and explain its physical causes. We present a mathematical distributed model that can accurately describe the torsional motion of the drilling device.
Soft string and stiff string models are two different mathematical models which are used for torque and drag analysis. They were developed to describe the mechanical behavior of the drill string inside the borehole, and they have their own theoretical background and assumptions.