This paper focuses on the problem of linear track keeping for marine surface vessels. The influence exerted by sea currents on the kinematic equation of ships is considered first. The input-to-state stability (ISS) theory used to verify the system is input-to-state stable. Combining the Nussbaum gain with backstepping techniques, a robust adaptive fuzzy algorithm is presented by employing fuzzy systems as an approximator for unknown nonlinearities in the system. It is proved that the proposed algorithm that guarantees all signals in the closed-loop system are ultimately bounded. Consequently, a ship’s linear track-keeping control can be implemented. Simulation results using Dalian Maritime University’s ocean-going training ship ‘YULONG’ are presented to validate the effectiveness of the proposed algorithm.

This paper investigates the vibration characteristics of diesel engine cylinder heads by means of the time series method. With the concept of “Assumed System”, the vibration transfer function of real cylinder head structures is established using the autoregressive-moving average models (ARMA models) of cylinder head surface vibration signals. Then this transfer function is successfully used to reconstruct the gas pressure trace inside the cylinder from measured cylinder head vibration signals. This offers an effective means for diesel engine cylinder pressure detection and condition monitoring.

A classical time-varying signal, the multi-component Chirp signal has been widely used and the ability to estimate its instantaneous frequency (IF) is very useful. But in noisy environments, it is hard to estimate the IF of a multi-component Chirp signal accurately. Wigner distribution maxima (WDM) are usually utilized for this estimation. But in practice, estimation bias increases when some points deviate from the true IF in high noise environments. This paper presents a new method of multi-component Chirp signal IF estimation named Wigner Viterbi fit (WVF), based on Wigner-Ville distribution (WVD) and the Viterbi algorithm. First, we transform the WVD of the Chirp signal into digital image, and apply the Viterbi algorithm to separate the components and estimate their IF. At last, we establish a linear model to fit the estimation results. Theoretical analysis and simulation results prove that this new method has high precision and better performance than WDM in high noise environments, and better suppression of interference and the edge effect. Compared with WDM, WVF can reduce the mean square error (MSE) by 50% when the signal to noise ration (SNR) is in the range of −15dB to −11dB. WVF is an effective and promising IF estimation method.

The non-linear finite element software ABAQUS was used to simulate the dynamic response of a marine supercharged boiler when subjected to impact loading. Shock resistance was analyzed by the time-domain simulation method. After exhaustive simulations, the effect of air pressure induced by different working conditions on the shock response of a supercharged boiler was reviewed, leading to conclusions about the variability of structural response with different loading parameters. In order to simulate the real impulsive environments of supercharged boilers, the integration of equipment and ship structure was then primarily used to analyze shock response. These distinctly different equipment shock test methods, run under equivalent work conditions, were compared and the causes of discrepancy were analyzed. The main purpose of this paper is to present references for the anti-shock design of marine supercharged boilers.

To analyse a possible way to improve the propulsion performance of ships, the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field. The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller, which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data, which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.

To design a more effective blade pitch adjustment mechanism, research was done on changes to the hydrodynamic characteristics of VVPs (Variable Vector Propeller) caused by different rules for changing pitch angle. A mathematical method for predicting the hydrodynamic characteristics of a VVP under unsteady conditions is presented based on the panel method. Mathematical models for evaluation based on potential flow theory and the Green theorem are also presented. The hydrodynamic characteristics are numerically predicted. To avoid gaps between panels, hyperboloidal quadrilateral panels were used. The pressure Kutta condition on the trailing edge of the VVP blade was satisfied by the Newton-Raphson iterative procedure. The influence coefficients of the panels were calculated by Morino’s analytical formulations to improve numerical calculation speed, and the method developed by Yanagizawa was used to eliminate the point singularity on derivation calculus while determining the velocities on propeller surfaces. The calculation results show that it’s best for the hydrodynamic characteristics of the VVP that pitch angle changes follow the sine rule.

The phase change characteristic of the power source of an underwater glider propelled by the ocean’s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source’s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38mm needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.

A new type of self-propelled barge was designed specifically for use on the Chishui River. This paper presents experimental results of its performance from tests in water of different depths, while bearing different loads. For test purposes, one of the best self-propelled barges from the Chishui River was used as a performance reference. The comparison showed that the new design has better maneuvering performance.

Predicting damage to vibration isolators in a raft experiencing heavy shock loadings from explosions is an important task when designing a raft system. It is also vital to be able to research the vulnerability of heavily shocked floating rafts. The conventional approach to prediction has been unreliable, especially when the allowable values or ultimate values of vibration isolators of supposedly uniform standard in a raft actually have differing and uncertain values due to defective workmanship. A new model for predicting damage to vibration isolators in a shocked floating raft system is presented in this paper. It is based on a support vector machine(SVM), which uses Artificial Intelligence to characterize complicated nonlinear mapping between the impacting environment and damage to the vibration isolators. The effectiveness of the new method for predicting damage was illustrated by numerical simulations, and shown to be effective when relevant parameters of the model were chosen reasonably. The effect determining parameters, including kernel function and penalty factors, has on prediction results is also discussed. It can be concluded that the SVM will probably become a valid tool to study damage or vulnerability in a shocked raft system.

For the structural-acoustic radiation optimization problem under external loading, acoustic radiation power was considered to be an objective function in the optimization method. The finite element method (FEM) and boundary element method (BEM) were adopted in numerical calculations, and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function, the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example, the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.

A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, (σ, ε) ∝ r ^−1/n−1). The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n → ∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund’s elastic-ideally plastic material by analyzing basic equations.