基于主动式截断控制的深水系泊系统混合模型试验技术研究

With the quick development of the ocean oil and gas to deeper water, the depths of offshore basins are often found unsatisfied with the requirements of the model tests of deepwater floaters, then the mooring lines have to be equivalent truncated, and the passive hybrid model testing is adopted which includes model testing, numerical reconstruction and numerical extrapolation, and that is the popular method presently. The static characteristics of the truncated mooring system can agree well with those of the un-truncated system, but the difference of the dynamic characteristics always exists. To avoid the difficulty, the active hybrid model testing method is proposed in this thesis, which is the combination of mooring truncation and active control system. The characteristic parameters of the mooring line above the truncation point and the external loads on it are unchanged, the truncated line is simulated through dynamic analysis, the motion of the truncation point is controlled by the servo system. Considering the coupling among the three parts, and based on the slender rod theory and the PID control method, a fast numerical simulation system of the active truncated mooring lines in time domain is established, the mooring damping and large stretch and slow drift force is accurately simulated, and the dynamic similarity between the truncated and un-truncated mooring system is realized. The time step and controlling parameters are optimized, and also the computational efficiency and real-time delivery of data are guaranteed. Finally, a set of automatic control system is designed, representative cases are selected and model tests in deepwater basin are implemented, which verifies the reliability of the active testing method and the feasibility of the substitution to the existing passive testing method, which provides a base for future researches in this field.

随着海洋油汽的开发生产向越来越深海域发展,海洋工程水池深度经常不能满足深水平台系泊系统模型试验的要求，对系泊线进行等效截断设计，然后进行水池试验、数值重构、数值外推的被动式混合模型试验是目前国内外采取的主要办法之一。现有研究只能保证截断前后系泊线的静力特性一致，而动力特性则很难保持一致。为避免以上难题，本课题提出将系泊截断与主动控制相结合的主动式混合模型试验方法。保持截断点以上系泊线特性参数和外部载荷不变，被截断的系泊线由动力分析得到，截断点的运动由伺服系统进行控制。考虑三者之间的耦合作用，基于细长杆理论和PID控制方法，建立一套主动式截断系泊快速时域数值仿真系统，准确模拟系泊线的动力特性，优化时间步长和控制参数，保证计算效率和数据的实时传递。设计一套自动控制系统，选择典型案例在我校深水池进行模型试验，证明主动式试验方法的可靠性和取代被动式试验方法的可行性，为今后的相关研究奠定基础。

本申请项目针对目前深水系泊系统模型试验存在的水池尺度不能满足需要的情况，提出了主动式混合模型试验方法。基于细长杆理论和PID控制方法，考虑未截断系泊线、控制系统及被截断系泊线之间的耦合作用，建立了一套主动式截断系泊时域数值仿真系统。通过优化时间步长和控制参数，可以对截断点进行很好的控制，准确模拟系泊线的动力特性。通过不同类型系泊系统的案例分析，在顶端施加不同的运动形式，比较截断前后系泊线的动力特性，吻合良好，证明了该系统的通用性。最后在深水池对一深水SPAR系泊系统进行了模型试验，并与被动式截断模型试验结果和全水深系统计算结果进行了比较，证明了主动式截断方法的优越性和可靠性。从而为今后的相关研究奠定了基础。