Discrete recoil control system modelling and optimal recoil damping of deepwater drilling riser systems

This study addresses discrete dynamic modelling and the optimal recoil control problem of deepwater drilling riser systems subject to the friction resistance of fluid discharge and platform heave motion. First, a discretetime exosystem model for friction resistance of drilling fluid discharge is developed; then, a discrete -time dynamic model of platform heave motion is established. Third, a finite -time discrete optimal recoil controller with feedforward compensation mechanisms was designed. The optimal recoil controller gains can be obtained by iteratively solving discrete equations. The simulation results show that under the discrete feedforward and feedback optimal recoil controller and pure feedback optimal recoil controller, the recoil movements of the riser system are significantly restrained. Moreover, the former is more effective than the latter at resisting the riser recoil response.