A Study on Development of Control System for Long Riser

在海洋活动中，长的海洋锚有多种用途。与横截面面积相比，它们的长度很长，因此，刚度相对降低，并且海洋船体显示出非常柔性的行为。这些海洋浮体经常受到重力、流体力和浮体反力等多种外力的作用，为了建立悬挂式柔性立管涡激振动的时间序列模拟方案，进行了不规则强迫振动实验。立管模型的顶端在水平面（X方向）内不规则地振荡。我们认为这种不规则运动是由海浪引起的浮式结构物的纵荡运动。对于不规则纵荡运动的波浪数据，我们使用国际船舶和海洋结构物大会（I.S.S.C）波浪谱，其定义为具有有效波高（Hw）和平均周期（Tw）。实验条件被确定为Hw和Tw的组合。用CCD摄像机测量模型的三维运动，并使用运动图像分析方法对结果进行分析。最后，通过数值计算与实验结果的对比，验证了该数值格式的准确性。在上述研究的基础上，开发了长立管的控制系统。采用线性变参数控制方法设计了增益调度控制器，同时将其设计问题转化为线性时不变性能优化问题。通过与实验结果的比较，验证了该控制器的性能。

Long marine risers are used for many purposes in ocean activities. Their lengths are very long compared with their cross section area, therefore, the stiffness relatively decreases and marine risers show very flexible behavior. These marine risers are always exposed to many external forces such as gravity, fluid forces and reaction force form the floating structure.In this research, in order to develop a scheme of the time series simulation of the VIV of the hanging flexible riser, we carried out some irregular forced oscillating experiments. The top end of the riser model was oscillated irregularly in a horizontal plane (X direction). We think this irregular motion as the surging motion of the floating structure caused by ocean waves. For the wave data of irregular surging motion, we used an International Ship and Offshore Structures Congress (I.S.S.C) wave spectrum, which is defined as having significant wave height (Hw) and mean period (Tw). Experimental conditions were determined as combinations of the Hw and Tw. The resulting three-dimensional motion of the model was measured with CCD cameras, and the results were analyzed using a motion picture analysis method..Finally, by comparing the numerical and experimental results, the accuracy of this numerical scheme was validated.On the basis of above research, we developed a control system of a long riser. A gain scheduling controller is designed using LPV (Linear parameter varying) control method, where its design problem is formulated into a performance optimization problem with LMI (Linear Time Invariant) simultaneously. The performance of this controller is validated by comparing with experimental results.