海上风电结构在运行过程中由于受到复杂的海洋环境作用，不可避免地会发生机械故障。而风机结构模态轨迹包含了丰富的结构运行状态信息，是判断海上风电结构是否发生故障的重要技术手段。但是在真实的海洋环境中很难找到固定的参考点测量结构的位移信息，而直接对加速度积分会导致得到的位移信息产生虚假漂移。该研究发展了一种基于低阶状态空间模型的海上风电结构模态轨迹计算方法，首先通过复指数分解方法对实测的加速度信号进行分解，通过引入低阶状态空间模型将计算中的高阶微分方程转化为低阶矩阵微分方程，克服了传统复指数分解方法对噪声敏感的病态问题，极大地提升了分解精度，然后通过求解得到的复指数参数得到位移中的模态信息，实现海上风电结构的运动监测。该研究首先通过五自由度数值模型验证了提出方法的正确性，并通过单桩海上风电结构的实测数据验证了算法在处理实测信号的有效性。结果表明所提出的方法可以为海上风电结构的模态轨迹计算提供理论指导，具有潜在的工程应用价值。

During the operation of offshore wind turbines, due to the complex marine environment, mechanical failure is inevitable.The modal trajectory of the offshore wind turbine contains a wealth of information on the operation status of the structure, and is an important index to determine whether the structure has failed.A method was developed for calculating the modal trajectory of the offshore wind turbine based on a low-order state space model, and the motion monitoring of the modal trajectory was implemented.To investigate the performance of the proposed method, two examples were introduced.First, a numerical model with five-degree-of-freedom was used to verify the correctness of the proposed method.And then, the measured data of a monopile offshore wind turbine was used to investigate the effectiveness of the proposed method in processing actual signals.The results show that the proposed method can provide theoretical guidance for calculating the modal trajectory of offshore wind turbines, and has potential engineering application values.