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This paper proposes an improved sparrow search algorithm (ADGSSA) based on multi-strategy fusion, and studies and verifies it in the thrust distribution of the dynamic positioning system of the new research vessel of Dalian Maritime University. First, the sparrow search algorithm is introduced. Aiming at its shortcomings in convergence speed, optimization accuracy and easy to fall into local optimality, a multi-strategy fusion improvement scheme including piecewise nonlinear dynamic random convergence factor strategy, warning position update condition and formula adjustment strategy, and golden sine perturbation strategy is proposed. Subsequently, the improved algorithm is applied to 12 benchmark functions with different characteristics and compared with Coati optimization algorithm (COA), whale optimization algorithm (WOA) and sparrow search algorithm (SSA). Experimental results show that ADGSSA outperforms the other three algorithms in optimization accuracy, convergence performance and stability. In the evaluation of 12 benchmark functions, ADGSSA demonstrates superior performance compared to SSA, WOA, and COA. Specifically, ADGSSA achieves the closest optimal value in 83% of the functions, provides the best average value in 85% of the functions, and has the lowest standard deviation in 75% of the functions. In the actual application of the thrust distribution system, ADGSSA shows significant advantages. Compared with WOA, the average power of the thruster is reduced by about 75%; compared with SSA, it is reduced by about 35%; compared with COA, it is reduced by about 17%. In addition, in 12 sets of thrust tests, the thruster wear of ADGSSA reached the smallest proportion of 82% among the four algorithms, which is significantly better than other algorithms. The test results and convergence curves further show that ADGSSA has significant effectiveness and superiority in improving the thrust distribution performance of the dynamic positioning system, proving the potential for promotion and application of multi-strategy fusion methods in control strategies.

Prediction of the self-propulsion performance of seawater MHD underwater vehicles is of great significance for the design and rapid optimization of the vehicle. Based on a typical advanced two-pole superconducting magnet (with a large warm hole of 260mm and a high magnitude of the magnetic field of 6.5T) which is close to practical application, this paper considers the underwater vehicle with the most promising application prospect of the MHD thruster as a research object. Based on the Fluent MHD module, using the full three-dimensional CFD numerical simulation method, and starting from the coupling mechanism of electric, magnetic and fluid physical fields of the MHD thruster, the paper analyzes the generation sources, influencing factors, and variation laws of thrust under self-propulsion from the point of view of electromagnetic, pressure and viscous forces. Efficiency characteristics of MHD thrusters are analyzed by considering propulsion, channel, electromagnetic, and jetting efficiency. Finally, a more comprehensive self-propulsion performance of the seawater MHD thruster is obtained. [ABSTRACT FROM AUTHOR]

Distribution pattern of thrust force on double-row stabilizing piles is one of the essential factors for the design of stabilizing piles. For a bedrock-overburden landslide strengthened with double-row stabilizing piles, four sets of laboratory physical model test are conducted considering various rear-row pile configurations. In particular, slip surface softening effect due to heavy rainfall is physically simulated using external water injection and infiltration into the shear band through a special channel. Distribution characteristics of the landslide thrust on the two piles are measured, which is further verified by a numerical simulation method FLAC3D. The test results show that the thrusts on the rear and fore piles present a parabolic distribution pattern, and the location with peak value is relatively close to the slip surface. If the pile location remains unchanged, the peak value of the thrust force behind the rear pile decreases with the increase of its embedded depth and the position with peak value moves upward; while the peak value of the thrust behind the fore pile increases with the embedded depth of the rear pile top, and the position with peak value changes unobviously. The slip surface softening effect does not change the distribution pattern of the thrust forces on piles, but it can increase the thrusts behind the piles; compared with the top and bottom of the piles, the increase of the thrust in the middle part of the piles is relatively larger. The thrust forces on the rear and fore piles under external water injection are about 14.3%~21.4% and 17.9%~24.8% higher than those before the softening action, respectively.

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[Objectives] To solve the issue of thrust loss caused by the interaction between the ship thrusters and the excessive power fluctuation in the power system, an improved A success-history adaptive differential evolution(SHADE)algorithm is proposed.[Methods] A multivariable optimization problem is established,which takes the power consumption of the propulsion system as the objective function,the thrust and the directional angle of the thruster as the control variables,and the change rate of the thrust and the directional angle of the thruster as the constraint conditions. For the traditional SHADE algorithm, an improved SHADE algorithm based on the degree of iteration is proposed to solve the thrust distribution optimization issue. The simulation results of the traditional SHADE algorithm and the improved SHADE algorithm are compared.[Results] The simulation results show that under the same simulation environment,the error between the actual thrust torque instruction obtained by the traditional SHADE algorithm and the desired thrust torque instruction generated by the dynamic positioning controller is large,and the power of the thruster fluctuates greatly;while the improved SHADE algorithm can control the torque command error of the expected thrust and the actual thrust within a small range,in which the surge and the sway error is within ±5×10-5 kN,and the yaw error is within ±3×10-5 kN·m.[Conclusions] The improved SHADE algorithm can transfer the dynamic positioning command controller more accurately under the action of environmental disturbance, to solve the problem of ship power system thrust distribution,and lay the foundation for how to use the thrust distribution to maintain the stability of the ship's power system.

Objectives In order to make the dynamic positioning of azimuth thrusters respond to external environmental forces in time, avoid the large-scale rotation of the thrusters and achieve high precision dynamic fixed-point positioning control, research on the optimal workspace of azimuth thrusters is carried out. Methods Taking the dynamic positioning self-driven model with two azimuth thrusters and a lateral thruster as the research object, the problem of the current thrust allocation singularity optimization index is analyzed, and the thrust limits of the thrusters are further considered. The method of traversing the thrust and azimuth of the thruster to establish the axial maximum capability matrix is applied. According to the external environmental force mean and variance, the minimum axial capability requirements are calculated, the optimal workspaces of the thrusters in different external environments are determined by combining the prohibition angle, and a new thrust allocation logic framework is proposed. The fixed-point positioning experiment of a dynamic positioning ship model based on the traditional singularity index and optimal workspace is carried out. Results The experimental results show that the proposed method can overcome the shortcomings of the previous singularity index and achieve control accuracy of 0.1 m radius position and 0.5 degree direction control accuracy under the propeller azimuth within the range of fifty degrees.Conclusions This method can replace the singularity index; it also satisfies the requirements of the ship model dynamic positioning experiment and has certain practical engineering value.

With the widespread use of unmanned aerial vehicles in the aviation industry, the importance of detailed examination of propellers, whose task is to provide thrust, has also increased. A propeller is a part that is formed by attaching more than one aerodynamically shaped blade to a hub and produces thrust by being rotated by a motor. The amount of thrust that is produced by a propeller depends on some parameters such as diameter, number of blades, pitch angle, etc. The aim of this study is to investigate the thrust distribution along a propeller diameter section with the gradual increase of the hub diameter. Related studies show that the maximum thrust of a propeller is obtained in the region between 75% and 85% of the propeller length. In order to obtain the necessary data, numerical flow analyzes were made and the results were discussed. As a conclusion, at the very closer to the root of the propeller blade, the amount of produced thrust is considerably low compared to the near tip of the propeller. Therefore, the thrust loss due to the increase of the propeller hub diameter is negligible and maximum thrust is obtained in the expected region. [ABSTRACT FROM AUTHOR]

A thrust distribution approach is proposed in this paper for a variable thrust solid propulsion system with an attitude control system (ACS) that uses a reduced number of nozzles for a three-axis attitude maneuver. Although a conventional variable thrust solid propulsion system needs six ACS nozzles, this paper proposes a thrust system with four ACS nozzles to reduce the complexity and mass of the system. The performance of the new system was analyzed with numerical simulations, and the results show that the performance of the system with four ACS nozzles was similar to the original system while the mass of the whole system was simultaneously reduced. Moreover, a feasibility analysis was performed to determine whether a thrust system with three ACS nozzles is possible. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate force distribution characteristics for propelling system of tunneling machines in mixed ground. First, a mechanical model for pushing system in composite strata is constructed. Then, eccentricity trunk is determined using spatial force ellipse eccentricity to measure the degree of uniformity of forces applied on rear segments in a thrust system. Finally, the eccentricity trunk is used to the thrust system of a tunneling machine applied in engineering. Force distribution performance of various arrangements with equal quantities of jacks is discussed in detail. Results from virtual prototype simulation prove the numerical analytical results. A theoretical foundation and support is provided for the design of non-equidistant pushing system of tunneling machines under composite stratum. [ABSTRACT FROM AUTHOR]

Disc cutter is mainly used in cutting through hard rock. Disc cutter wear is inevitable during tunnel boring machine (TBM) tunneling, and excessive wear can lead to a decrease in tunneling efficiency and increase construction risks. Therefore, the importance of predicting the disc cutter wear accurately and arranging the cutter change plan can never be overemphasized. In this study, disc cutter wear data and replacement records for three shield chamber openings were analyzed, which were collected from a water conveyance tunnel project in Guangdong, China. It was found that the normal wear failure accounted for approximately 76.19%, while the abnormal wear failure accounted for 23.81%, and the range of tools to be replaced due to normal wear continues expanded as the tunneling distance increased. Based on the observed wear data, it is found that the wear rate of edge tools is much lower than that of center tools, which does not conform to the normal wear rules. Subsequently, a new disc cutter wear prediction model was developed considering energy conversion and uneven thrust distribution for explaining this problem. The determination method of the energy conversion coefficient k and thrust distribution coefficient b was proposed, and they had been obtained from the wear data in the first replacement. On the other hand, the proposed model has higher accuracy in both cutter wear and cutter change range prediction compared with the existing models. However, the prediction accuracy of the proposed model will decrease with the increase of the tunneling distance, so the undetermined coefficients k and b need to be updated in a timely manner. • Cutter wear data, tunneling parameters and cutter life in a tunnel project are collected and analyzed. • A new disc cutter wear prediction model is established considering uneven thrust distribution. • The prediction results verified the effectiveness of the proposed model in this paper. [ABSTRACT FROM AUTHOR]