Suppressing stick–slip oscillations in drill-strings by Modified Integral Resonant Control

Control of Stick-slip Oscillations in Oil Well Drill Strings Using the Back-stepping Technique

This paper deals with the problem of suppression of stick-slip oscillations in oil well drill-strings. The backstepping technique is used to design two control schemes for the system. The first controller is a typical backstepping controller; the second controller is a sliding back-stepping controller. Moreover, a reduced order observer is proposed to estimate the unmeasurable states of the sys...

Integral resonant control of collocated smart structures

This paper introduces integral resonant control, IRC, a simple, robust and well-performing technique for vibration control in smart structures with collocated sensors and actuators. By adding a direct feed-through to a collocated system, the transfer function can be modified from containing resonant poles followed by interlaced zeros, to zeros followed by interlaced poles. It is shown that this...

Avoiding and Suppressing Oscillations

A telegrapher equation for electric - telemetering in drill strings

A reliable method of transmitting downhole information to the surface while drilling is essential to improve drilling applications. We have designed a numerical algorithm for simulation of electric-signal transmission through the drill string, based on the telegrapher equation (a circuit model). The drill string is then represented by a transmission line with varying geometrical and electromagn...

On the group velocity of guided waves in drill strings.

A key element to verify the drill-bit signal processing is the estimation of the time delay of the guided waves transmitted through the drill string from the bit to the surface. This delay can be measured from drill-bit vibrations or calculated using the mechanical properties of the drill string. The calculation of the complete solution and the exact dispersion relations requires expensive nume...