Recoil control of nonlinear drilling riser systems via integral sliding mode schemes

This paper studies the nonlinear modeling and the integral sliding mode recoil control for drilling risers subject to heave motion of drilling platform, friction force of drilling discharge, and perturbation of control input. First, by taking into account nonlinear characteristics of the tension, a nonlinear model of the recoil system with input perturbations and external disturbances is presented. Second, an optimal integral sliding mode recoil control strategy is proposed to resist the recoil movement of the riser, and the existence condition and designed algorithm of the sliding mode recoil controller are provided. Third, to address the physically realizable issue of the sliding mode recoil controller, friction force and platform heave motion observers are designed. Simulation results demonstrate that the optimal integral sliding mode recoil controller can attenuate the riser's recoil motion significantly. In addition, it is robust to the perturbations of control input and outperforms the existing recoil controllers from the standpoint of ensuring zero steady-state errors of the riser.