Recoil control of deepwater drilling riser systems via optimal control with feedforward mechanisms

This paper deals with the problem of dynamic modeling and the optimal recoil control of a deepwater drilling riser system subject to the friction force of drilling fluid discharge. First, based on the whole fluid column model of the friction force and the curve fitting method, a linear exosystem model is established to describe the dynamic properties of the friction force, where the friction force of drilling fluid discharge is formulated as an output of the exosystem. Then a recoil dynamic model of the drilling riser in the event of emergency disconnection is proposed to describe the recoil response characteristics. Third, an optimal recoil control scheme with discharge feedforward compensation is developed to refrain the recoil response of the riser system. The existence and uniqueness conditions of the optimal recoil controller are derived, and the gain matrices of the controller can be obtained by solving an algebraic Riccati equation and a Sylvester equation. It is found through simulation results that the proposed optimal recoil controller with feedforward compensation can reduce recoil response of the riser system significantly. Moreover, the proposed controller outperforms the existing optimal recoil control scheme in the sense of the quadratic performance indices of the riser system.