Adaptive output-feedback control of torsional vibration in off-shore rotary oil drilling systems

Motivated by an engineering application of torsional vibration suppression of off-shore oil drilling, we design an adaptive output-feedback controller for a one-dimensional wave partial differential equation (PDE) system, where an anti-damping term with an unknown coefficient and a general harmonic disturbance with unknown amplitudes exist in the bit, which is modeled as a second-order-in-time boundary. The control input anti-collocated with this boundary subject to uncertainty, is designed by using the adaptive control method and infinite-dimensional backstepping technique. The asymptotic convergence to zero of the uncontrolled boundary states, i.e., the oscillations of the angular displacement and velocity at the bit, and the boundedness of all states in the closed-loop system, are proved via Lyapunov analysis. The effectiveness of the proposed adaptive controller is verified via numerical simulation. The results also can be applied to other applications, such as vibration control of cable elevators with uncertain cage-guide friction and cage disturbances.