Non-linearity Analysis of Ship Roll Gyro-stabilizer Control System

A gyro-stabilizer is the interesting system that it can apply to marine vessels for diminishes roll motion.Today it has potentially light weight with no hy­drodynamics drag and effective at zero forward speed.The twin-gyroscope was chosen.Almost,the modelling for designing the system use linear model that it might not comprehensive mission requirement such as high sea condition.The non-linearity analysis was proved by comparison the re­sults between linear and non-linear model of gyro-stabilizer throughout fre­quency domain also same wave input,constrains and limitations.Moreover,they were cross checked by simulating in time domain.The comparison of interested of linear and non-linear close loop model in frequency domain has demonstrated the similar characteristics but gave different values at same frequency obviously.The results were confirmed again by simulation in irregular beam sea on time domain and they demonstrate the difference of behavior of both systems while the gyro-stabilizers are switching on and off.From the resulting analysis,the non-linear gyro-stabilizer model gives more real results that correspond to more accuracy in a designing gyro-sta­bilizer control system for various amplitudes and frequencies operating condition especially high sea condition.

大幅船舶横摇运动非线性附加质量惯性矩和阻尼矩特性的非参数识别

This study aims to investigate the nonlinear added mass moment of inertia and damping moment characteristics of largeamplitude ship roll motion based on transient motion data through the nonparametric system identification method.An inverse problem was formulated to solve the first-kind Volterra-type integral equation using sets of motion signal data.However,this numerical approach leads to solution instability due to noisy data.Regularization is a technique that can overcome the lack of stability;hence,Landweber’s regularization method was employed in this study.The L-curve criterion was used to select regularization parameters(number of iterations)that correspond to the accuracy of the inverse solution.The solution of this method is a discrete moment,which is the summation of nonlinear restoring,nonlinear damping,and nonlinear mass moment of inertia.A zero-crossing detection technique is used in the nonparametric system identification method on a pair of measured data of the angular velocity and angular acceleration of a ship,and the detections are matched with the inverse solution at the same discrete times.The procedure was demonstrated through a numerical model of a full nonlinear free-roll motion system in still water to examine and prove its accuracy.Results show that the method effectively and efficiently identified the functional form of the nonlinear added moment of inertia and damping moment.

A Simulation Model for Road and Maritime Environmental Performance Assessment

The White Paper published in 2011, Roadmap to a Single European Transport Area [1], urges on a 30% modal shift of road freight over 300 km to other modes (rail, maritime and inland waterways) by 2030, and more than 50% by 2050. However the environmentally friendly performance of maritime transport regarding air pollutant emissions in comparison with road transport is in doubt. This paper presents a three dimension simulation model, in which performed transport work, arisen emissions and produced impact are estimated and inter-related for the assessment of the environmental performance of both road and maritime transport. The simulation model will be a valuable decision making tool for policymakers as it enables the precise assessment of considered transport alternatives in the EU27 until 2020, and hence supports the design of future intervening actions.