深水钻井平台动力定位的推力分配研究

摘要

Dynamically Positioned vessels counteract environmental loads to maintain its position exclu-sively by means of its own active actuators in deepwater. The thruster system is regarded as a critical sys-tem with respect to positioning performance and safety. The role of control/force allocation in the real-time control hierarchy of DP system is addressed, and the difficulties of iterative solution for overactuated control allocation by using nonlinear programming optimization are pointed out. An explicit solution to the least square optimization with respect to extended thruster was presented to minimize power consumption for a deepwater drilling rig with redundant azimuth thrusters, the usage of extended thrust is to transform the nonlinear equal constraints to linear constrains. Since there are sector limitations for operation of the az-imuth thrusters, both amplitude and rate saturation, rate constrains on the azimuth angles and tear and ware are also taken into account. Simulation results show that the proposed thrust allocation scheme is applicable and reliable without specified requirements on storage space of memory and the control performance is satisfied with the proposed thrust allocation scheme.%　　深海动力定位主要依靠海洋结构物的自身动力来抵抗外界环境力的干扰，推进器系统作为动力定位系统的执行机构，其工作性能的好坏将直接影响到最终的定位效果。文章简述了推力分配在动力定位实时控制系统中的功能，并归纳了用非线性规划求解最优化问题可能存在的困难。针对981钻井平台冗余的全方位推力器配置，引入扩展推力将推力分配的非线性等式约束转化为线性等式约束，提出了基于扩展推力的拉格朗日最小平方优化的显性解，在最优扩展推力的基础上对每个推进器的最大推力、推力变化以及全方位推进器方向角的最大转动变化率均作了限制。仿真结果表明该推力分配策略切实可行，对实时控制系统的内存无特别要求，定位性能较好。