Ship Deformation Research Articles

Improved whale optimization-based parameter identification algorithm for dynamic deformation of large ships

In the field of ship deformation measurement, the inertial matching method has become a current research hotspot due to its advantages of high accuracy, easy implementation, and strong real-time performance. However, the parameters of dynamic deformation are affected by the environment, which severely restricts the further improvement of its accuracy. In response to this problem, this paper derives the mapping mechanism between the angular velocity difference and the dynamic deformation angle. And the data in the sliding window is used to establish the objective function on this basis. After that an improved whale optimization algorithm (IWOA) based on logic mapping is designed to perform parameters identification. Simulation and turntable experiment results show that the algorithm proposed in this paper can effectively identify the parameters. The results of the shipboard experiment show that the measurement accuracy of the deformation angle is significantly improved after parameters identification, and the RMS of estimation errors for the pitch, roll and yaw are 10.04′′,12.16′′,9.07′′ respectively.

A Deformation Measurement Algorithm Based on Adaptive Variable Parameter Multiple Model for Large Ships

Accurate measurement of ship deformation angle is of great significance for building a unified space attitude reference and improving the combat performance of the entire ship. However, many problems existing in the actual sailing process restrict its measurement accuracy severely, such as the time delay between measurement equipment, the unknown characteristics of measurement noise, and the unknown model parameters of the dynamic deformation. This article proposes an adaptive variable parameter multiple model (AVPMM) algorithm that can simultaneously solve these problems. First, a time delay compensation algorithm is derived to suppress the influence of time delay on measurement accuracy; then an adaptive cubature Kalman filter is designed based on the idea of adaptive filtering to suppress the influence of unknown characteristics of measurement noise; and finally, an AVPMM algorithm is designed by combining the above ideas to reduce the impact of unknown model parameters of dynamic deformation. The results of the simulation and turntable experiment show that this algorithm has good measurement accuracy and the error is less than $0.15^\prime$ .

Improved Ship Deformation Measurement System Based on OCC

With the development of image sensor frame rate and the intelligent terminal embedded camera, the Optical Camera Communication technology (OCC) which developed from the existing image sensor is being applied in more areas. Based on the principle of OCC technology and the research of 3D ship deformation measurement system, an improved 3D ship deformation measurement scheme is put forward. The hardware structure of the system is improved by using data simulation, and the time unit is integrated into the system by using infrared communication technology, and the circuit design is also carried out. The results show that the improved measurement system has lower hardware complexity and higher availability.

An inertial measurement method of ship deformation based on IMM filtering

Matching filtering algorithm based on inertial measurement unit is the development trend of deformation of ship hull. Kalman filter requires that the system model parameters are known accurately, however the parameters of the actual ship hull deformation model are unknown or uncertain. According to the above problem, this paper introduces interacting multiple models (IMM) Kalman filtering method based on the “velocity plus angular velocity” model matching. The estimated residuals of each model are used to calculate the probability of the corresponding model. Finally, simulation results show fast convergence, good stability and high accuracy of the proposed algorithm. Then, we use the Monte Carlo simulation. The results show that the IMM can increase 5%–10% accuracy than the Kalman filter. The IMM algorithm can improve the estimation accuracy of the deformation angle and the environmental adaptability compared with the traditional Kalman filter.

Dynamic Ship-Impact Load on Bridge Structures Emphasizing Shock Spectrum Approximation

AbstractIn current design specifications, a static procedure using code-prescribed loads has been commonly used to design bridges against ship collisions. However, the collision-induced response may be greatly underestimated as a result of the absence of the dynamic amplification effect in the static procedure. Hence, the safety of bridge structures exposed to ship collisions is still a concern, although they have been designed according to the current specifications. To this end, this paper aims to determine the dynamic ship-impact load on bridge structures and to evaluate its rationality. A simple approach to determining the dynamic ship-impact load was first developed based on the ship-bow force–deformation relationship (i.e., P–a curve) and the analytical model considering the structural stiffness. The equations for estimating the load duration and the time history of ship deformation were analytically derived. To evaluate the accuracy of the developed ship-impact loads and some other impact loads in ...

姿态匹配法测量船体变形角中时间延迟的补偿

姿态匹配法测量船体变形角中时间延迟的补偿

Large Ship Fluidsolid Coupling Dynamic Mathematic Model with Explicitly Form

In ship dynamics research field, large ship moving on sea water is a hot research project of water transportation. The fluidsolid coupling dynamics model of large ship is built by using time-dependent solid dynamics theory and fluid dynamics theory of ship. The linear analysis solution formula of ship deformation is obtained from the linear fluid-solid coupling equation. The hull displacements are obtained and the maximal displacement is found when the wave-hull resonance number becomes an integer.

Influence Analysis of Hull Deformation on Dynamic Behavior of Propulsion Shafting

The aim of this paper is to study the influence of hull deformation on dynamic behavior of ship propulsion shafting. Taking an 8530TEU container ship as an objective and using the finite element method, a global ship structure model is built up to evaluate the hull deformations under typical loading cases. Then the hull bottom-propulsion shafting integrated model is adopted to analyze the effect of hull deformation on shafting natural frequency under dry and wet mode. The results show that the natural frequencies of the shafting will increase due to the effect of hull deformation. Consequently, it is necessary to consider the effect of ship deformation when dealing with the dynamic behavior of ship propulsion shafting.

High-Accuracy Modeling of Ship Deformation Based on Inertial Measuring Method

High-accuracy modeling is the key problem of ship deformation measurement based on inertial measuring method. This paper is to find a high-accuracy modeling method based on the ship deformation data measured by optical devices. According to different modeling methods, mathematical models are designed by the analysis of the initial measurement data. Wavelet analysis method is introduced in the process of modeling. Attitude matching method is selected as the simulation algorithm and Kalman filter equations are set up based on the algorithm. Simulation results show that the ship deformation can be represented accurately by mathematical models. The Precision Estimation result is better than 0.4''.

An Anomaly Detection and Correction Method Based on Measurement Representation Model

Tracking data containing outliers would seriously distort the accuracy of data processing for space tracking ships. Effective measures have to be adopted for the detection and correction of outliers. The time series of observations obtained by space tracking ships contain complex periodical elements caused by ship deformation and rolling. It brings difficulty to the detection of outliers. To solve the problem, a variety of detection methods were studied based on measurement elements representation model. The paper gives an analysis about the characteristic of measurements taken by the ships and proposes to detect the information about outliers by considering the correlation in time, space and data properties. A detection model based on spline function representation model is constructed and tested. Numerical results show that the proposed method can detect and correct outliers effectively, and provide an alternative to the current method of the measurements processing for the space tracking ships.

A Ship Deformation Measurement Method Based on Quasi-Static Model

Angular matching method was used to measure ship’s deformation, three-axis fiber optic gyroscope units(FGU) are installed on various point of the ship, based on the model advanced by Mochalov, considering the character of ship’s static deforming angle varies, a quasi-static model was established, Kalman filter was introduced to estimate the ship’s quasi-static and dynamic deforming angles. To make the estimation more precise, gyro drifts was taking into account. Besides the theory simulation, practical experiment in sea area is also carried out, which lays the firm foundation for actual application of ship deformation measurement based on three-axis fiber optic gyroscope.

Numerical Modeling and Assessment of the Ebe Schooner-Brig

The Ebe schooner-brig was built in 1921 and sailed the Mediterranean Sea for almost 40 years before being dissected into 90 parts to be transported to Milan (Italy). There, the schooner was reassembled, and the naval pavilion of the National Museum of Science and Technology was built around the ship. After 45 years in the museum, the ship presents significant deformations of both the deck and the keel, particularly in correspondence with the external supports. Despite several interventions in the past and a recent restoration, the deformation phenomenon is still worrying, and the real cause has yet to be understood. Experts have already advanced some hypotheses, often in opposition to one another; unfortunately, a continuous monitoring of the ship deformation has not been installed. In the present study, the schooner structure is modeled with the commercial finite element code Diana, considering a two-dimensional model of the ship section and a three-dimensional model of the whole schooner, accounting for different levels of details and discretization. The results obtained allow for a deeper understanding of the stress-strain field in the schooner, providing a first safety assessment and useful hints for the design of the monitoring and future interventions.

Pose-relay videometrics based ship deformation measurement system and sea trials

The measurement of ship deformation has been a difficult problem for the global ship building industry and navigation field research. So far, an effective and proven method for measuring 3D position and attitude deformation remains unavailable. This article proposes an innovative pose-relay videometrics measurement system for ship deformation on the basis of primary research and experimental validation. The system offers solutions to the important technical problems such as infrared marker manufacture, high-precision detection and multi-camera synchronization and control. Sea trials were carried out, and reasonable, long-term, and continuous 3D data of position and attitude deformations between a given deck point and the ship reference, and between the ship’s head and the stern were acquired for the first time. The experiments have highlighted the considerable applicability of the proposed method of deformation measurement and long-term monitoring of ships and similar large structures.

Numerical Assessment of the Ebe Schooner-Brig

The Ebe schooner-brig was built in 1921 and sailed the Mediterranean’s sea for almost forty years, before being dissected into ninety parts to be transported in Milan (Italy). There, the schooner was reassembled and the naval pavilion of the National Museum of Science and Technology was built up all around the ship. After forty years in the museum, the ship presents significant deformations of both the deck and the keel, particularly in correspondence of the external supports. Despite several interventions in the past and a recent restoration, the deformation phenomenon is still worrying, and the understanding of the real cause is lacking from many aspects. Experts have already advanced some hypotheses, often in opposition to one another, and unfortunately, a continuous monitoring of the ship deformation has not been started yet. In the present paper, the schooner structure is modeled with the commercial finite element code Diana, considering a two-dimensional model of the ship cross-section. The obtained results allow for a deeper understanding of the stress-strain field in the schooner, providing a first safety assessment and useful hints for the design of the monitoring and future interventions.

Fold-ray videometrics method for the deformation measurement of nonintervisible large structures

An optical measurement method, the fold-ray videometrics method, that is applicable to the deformation measurement of large structures is proposed. Through an illustration of ship deformation, the principle of fold-ray videometrics and the composition of the deformation measurement system are introduced. The fold-ray videometrics method is able to transfer or relay three-dimensional geometric information with a fold-ray optical path and thus is capable of real-time measurement of three-dimensional positions, attitudes, and deformations between nonintervisible objects and those of intervisible objects with a very large angle of view. The proposed method therefore has the potential to be applied in deformation measurement of large structures.

CRACK TIP STRAIN ON SHIP AND IN SITU MEASUREMENT IN SHIPYARDS

The paper presents the application extent of procedures for measurement deformations on ships. The actual deformation distribution was measured on the surface of the specimen by the optical grating method (OGM) parallel to the CTOD measurements. Displacements are actually measured with two cameras, i.e. stereometric method. The stereometric method for monitoring deformation is presented with an example of application. The deformation of the surface was measured by recording the displacements of the optical marks, and captured in such a way that the 3D coordinates are connected with picture coordinates. Further calculation of the ship deformation gradient is possible by using the theory of large deformations, which allows large plastic deformations as well as rigid ship motion. Further development of research is focused on constant deformation and damage monitoring in order to take full advantage of computer technology.

Structural design of process decks for floating production, storage and offloading units

This work analyzes the influence of ship motion and deformation on the structural design of decks to support production plants in floating production, storage and offloading units (FPSOs). These decks are space frames with lengths ranging from 30 to 100 mr, with a variable number of rigid supports linked to the ship hull. The deck and ship hull are modeled together for naval and structural analysis. A global, coupled analysis is performed considering the deck and ship structures; sea loads are evaluated by means of probabilistic methods.

Ship Impact on Inland Waterways

Ship impact on civil engineering structures along inland waterways is discussed, with particular reference to the Rhine River at Basle, Switzerland. Hazard and impact scenarios are developed and ship deformation is analyzed. These findings are applied to the design of structural components, e.g., bridge piers.

The Deformation of Ship's Hull under Construction (No. 5)

In this report, three subjects will be dealt with. First, an example of variation of transverse shrinkage of ship's bottom plating during progress of hull welding will be illustrated, which variation of shrinkage somewhat resembles that found in fore & aft direction.Secondly, an attempt will be made to explain results observed in actual cases of ship construcition which indicated that the ship's bottom deformation such as the rising of the stern was caused chiefly by welding the bottom in the vicinity of the deformation and was little affected by welding of the main deck & structures above the main deck.The third and major discussion will concern the influence of ship's deformation on the propulsion shafting. When main propulsion shaft bearings are out of line, many troubles should be anticipated, such as shaft failure, extraordinary wear-down of bush or bearings, vibration or whirling, and loss of power etc.Regarding the problem of untrue shaft bearing, the variation of bearing reactions and the bending moments in shafting corresponding to various alignment conditions were calculated on one ship. The comparison of the resulting calculations led to the conclusion that the most important thing is to equalize the bearing reaction and bending moment of shafting everywhere as much as possible. It is only of secondary importance to maintain all bearings on straight line.Another conclusion resulting from the calculation is that a faired deflection of bearing position such as deformation due to ship's hogging or sagging, even if the amount of deviation of bearing position from a reference line is remarkably large, will do little harm the shafting. Rugged deformation such as in case of stern bush wear-down or local deformation due to welding will be harmful to the shafting.