An ADRC-based Active Heave Compensation for Offshore Rig

Offshore drilling platform is a kind of offshore engineering structure, which provides operation and living space for the development and utilization of marine resources. There is a big difference between offshore drilling and land drilling. In this process, the drilling platform floats on the fluctuating ocean surface, while the drill pipe carries the drill bit at depth of several kilometers. In the middle and deep sea areas, under the action of waves, the offshore drilling platform will not only sway around, but also rise and fall. This periodic upward and downward motion with wave will cause the periodic upward and downward motion of drill pipe string. Periodic upward and downward movement of drill pipe string will increase or decrease the hook tension, which will directly affect the change of bottom hole drilling pressure. When the drilling pressure drops to a certain limit, the bit will be out of the bottom of the well and can not be drilled continuously. Therefore, in order to ensure the normal use of offshore drilling platform and improve drilling efficiency, it is necessary to adopt heave compensation system to reduce the relative movement of drill pipe string and seabed, and maintain constant tension load, reduce the impact of natural climate such as sea breeze, wave, current on drilling platform, and improve drilling efficiency and safety. And it can prolong the service life of drilling equipment. In this paper, the working principle of offshore rig heave compensation system is given, and the design idea of the system is described in detail. Because the speed control system lacks precise mathematical model and has the characteristics of non-linearity and variability, an ADRC control strategy is adopted. The experimental results show that the controller can effectively control the compensation speed, has high control accuracy, strong anti-interference ability, is insensitive to parameter changes, and has a certain robustness.