Integrated estimator and L1 adaptive controller for well drilling systems

This paper presents an integrated adaptive estimator-controller scheme for a class of systems with only partially measured states. To estimate the non-measured states, a fast adaptive estimator is applied. The estimation is used in the L₁ adaptive controller, which adapts to time-varying unknown parameters and time-varying bounded disturbances in the system without restricting their rate of variation. The results demonstrate that the L₁ adaptive controller has guaranteed performance bounds for system´s both input and output, while using the estimation of the regulated outputs. The approach is used to control the bottom hole pressure of a well drilling system, in which the measurement of the pressure is updated at a low rate. Simulations verify the theoretical findings.