Achieving Bayes MMSE performance in the sparse signal + Gaussian white noise model when the noise level is unknown

A new physical parameter identification method with a name of EKPF-LS is proposed for shear frame structures under limited inputs and outputs by a combination of extended Kalman particle filter (EKPF) and least square (LS) algorithm. The basic principle of EKPF-LS is to establish the proposed distribution function of the particle filter through EKF-LS. In this method, EKPF is introduced to get rid of the restriction of Gaussian white noise model and reduce the linearization error caused by EKF. Meanwhile, LS is utilized to address the problem of unmeasured excitation estimations. The effectiveness and accuracy of the proposed EKPF-LS method is verified by a numerical example of a four-story hysteretic shear frame under an earthquake excitation and an experimental test of a four-story shear type frame using Gaussian white noise and sine sweep signal as excitations, respectively. Gaussian colored noises are then added to the solved and measured response signals in the numerical example and experimental test, respectively. The results demonstrate that the proposed method can identify the stiffness of shear frame structures effectively and is superior to the existed EKF-LS approach when the structural system is nonlinear structural system or Colored noise model.

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Experimental study on effect of side-mooring lines on dynamics of a catenary moored semi-submersible system

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090219858820 ◽

2019 ◽

Vol 234 (1) ◽

pp. 127-142

Author(s):

Sheng Xu ◽

Chun-yan Ji ◽

C Guedes Soares

Keyword(s):

White Noise ◽

Model Tests ◽

Noise Model ◽

Floating Platform ◽

Mooring Lines ◽

Motion Response ◽

Free Decay ◽

Wave Basin ◽

White Noise Model ◽

Response Amplitude Operators

In this article, a novel mooring system with side-mooring lines is proposed for a traditional shape semi-submersible platform with four columns. To obtain the dynamics of moored system, model tests were carried out at a wave basin, including free-decay model tests, white noise model tests and irregular model tests. The natural periods in heave, roll and pitch models were measured and compared with numerical results. The motion response amplitude operators under 90° and 135° waves were obtained from white noise model tests and then compared with numerical simulations. A 100-year sea state in South China Sea was simulated in the wave basin by the JONSWAP spectrum, and the 6-degree-of-freedom motion responses of semi-submersible and mooring tensions were recorded in beam and quartering seas. The effects of the side-mooring lines on the floating platform motion response, mooring tensions and mooring fatigue damage are evaluated by comparing the results with and without side-mooring lines installed.

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