Estimation of Hydrodynamic Derivatives derived from Transient Manoeuvring Tests

包括频率的影响的水动力导数估计通过瞬态操纵试验。平面运动机构（PMM）被用于此目的，但部分改变，以允许瞬态motions. Utilizing傅立叶分析，线性导数在宽的频率范围内，它们与来自常规PMM测试。但结果的可靠性在很大程度上取决于输入瞬态运动的特性和测量力的质量。然后，研究了最大振幅和时间参数对瞬态运动的影响，每对导数（如附加质量系数和阻尼系数）在本质上满足Kramers-Kronig关系。首先，对实验结果进行希尔伯特变换，从总体上证实了这种关系。但是，由于测量频率范围的限制，它们之间存在着不可忽略的差异.其次，假设因果系统，每个传递函数被假定为具有有限阶Hurwitz多项式的有理函数。如果在传递函数中确定了一组适当的系数，我们就不需要再确认Kramers-Kronig关系。利用传递函数的波特图进行参数辨识，各项实验结果与传递函数吻合较好。

Hydrodynamic derivatives including the effect of frequency are estimated by means of transient manoeuvring tests. Planar motion mechanism (PMM) was used for this purpose, but partially changed to allow transient motions.Utilising the Fourier analysis, linear derivatives are obtained in wide frequency range and they coincide with those derived from regular PMM tests. But the reliability of the results deeply depends on the characteristics of input transient motions and on the quality of measured forces. Then, the effect of maximum amplitude and time parameters applied to the transient motions are studied.Each pairs of derivatives (e.g. added mass coefficient and damping coefficient) satisfied the Kramers-Kronig relationship in nature. First, Hilbert transform was applied to the experiment results, and the relationship was confirmed in general. But, there are unnegligible difference, because of the limitation in measured frequency range. Next, supposing the causal system, each transfer function is assumed to a rational function with a finite order of Hurwitz polynominal. If a proper set of coefficients in the transfer function is identified, we need no more to confirm the Kramers-Kronig relationship. Bode's diagram of the transfer function is used for parameter identification, and each experiment result is coincided with the transfer function very well.