As an essential tool for installing subsea structures, heave compensation setup needs to be verified to make sure that the mechanical and control system meets the requirements, and this procedure can only be realized by simulations. However, because the mechanical structure and the mechanical model are very complex, precise modeling is complicated. A highly simplified mathematical model of the system can lead unrealistic simulation results, while more detailed models will need more computation time and more effort on debugging. To mitigate these problems, this paper uses a semi-physical test and combined simulation innovatively to validate the control effect for heave compensation setup based on the active disturbance rejection control (ADRC) technology.
The amount of offshore oil resources accounts for about 34% of the total global oil resources, and most of them are distributed in the deep-water areas with a water depth of more than 300m (Zhu, 2017). Deepwater oil and gas development relies on the support of subsea production equipment such as subsea manifold. When installing underwater equipment, the vessels are forced to do generalized heave movement (consists of the heave, pitch and roll). Due to the action of vessel heave, sea water damping and elastic force of the steel wire rope, a coupled dynamic response of underwater equipment mounted at the bottom of the winch cable will be produced (Bo Woo Nam, 2013). The response lags and the amplitude is much larger than the heave motion, which threatens the safety of the operation. For safety purpose, deep water equipment lowering system must be equipped with a heave compensator (Sungil
Shin, 2014; Kuchler S, 2011; Mingjie Li, 2013). Fig. 1 shows that the main body of the heave compensation system is a set of composite hydraulic cylinders mounted on the steel wire rope between the winch and the lifting point. The wave excitation signal is transmitted to the lifting point through the vessel, and the movement signal of the lifting point is measured by MRU and serves as the input signal of the heave compensation control system (Nam, 2012; Be, 2010). The elongation of the hydraulic piston is the output signal of the control system, and the length change of the hydraulic cylinder can compensate the heave of the wire rope (Weicai Quan, 2016; Mingjie Li, 2018;). Its application can extend the sea operation time, improve operation efficiency, and ensure the safety of operation (J.K. Woodacre, 2015; W. P. Li, 2016).
