欠驱动ODINs的全局逆最优循迹控制（英文）

This paper presents a design of optimal controllers with respect to a meaningful cost function to force an underactuated omni-directional intelligent navigator(ODIN) under unknown constant environmental loads to track a reference trajectory in two-dimensional space. Motivated by the vehicle’s steering practice, the yaw angle regarded as a virtual control plus the surge thrust force are used to force the position of the vehicle to globally track its reference trajectory. The control design is based on several recent results developed for inverse optimal control and stability analysis of nonlinear systems, a new design of bounded disturbance observers, and backstepping and Lyapunov’s direct methods. Both state- and output-feedback control designs are addressed. Simulations are included to illustrate the effectiveness of the proposed results.     

Parameter optimization and parametric deviation influence for shock resistance of double-stage vibration isolation system with limiters北大核心CSCD

［Objectives］For marine nuclear power plants, the relative displacement of the pump supported by a vibration isolation system should be strictly restricted. In order to improve the shock resistance of a vibration isolation system with displacement limiters, the parameter optimization and parametric deviation influence are studied. ［Methods］The theoretical model of a double-stage vibration isolation system with typical limiter parameters is established, the analysis of the shock response characteristics of the system is carried out using the direct integration method, the optimal limiter parameters are obtained using a genetic algorithm, and the influence of parameter deviation on the shock resistance of the system is studied. ［Results］Limiter parameters significantly affect the shock response characteristics of the vibration isolation system. The optimal limiter parameters improve the shock resistance of the system, but parameter deviation has a great influence on shock resistance. Based on the influence of parameter deviation, a deviation control strategy is proposed in which the elastic parameter should have a positive deviation and the gap parameter a negative deviation. The simulation results show that the proposed strategy can effectively alleviate the shock resistance degradation caused by deviation.［Conclusions］The results of this study can be used to guide the design, manufacturing and variation control of limiters for vibration isolation systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

桩倾角对导管架平台斜桩响应影响的参数研究（英文）

Offshore jacket-type platforms are attached to the seabed by long batter piles. In this paper, results from a finite element analysis, verified against experimental data, are used to study the effect of the pile's inclination angle, and its interaction with the geometrical properties of the pile and the geotechnical characteristics of the surrounding soil on the behavior of the inclined piles supporting the jacket platforms. Results show that the inclination angle is one of the main parameters affecting the behavior of an offshore pile. We investigated the effect of the inclination angle on the maximum von Mises stress, maximum von Mises elastic strain, maximum displacement vector sum, maximum displacement in the horizontal direction, and maximum displacement in the vertical direction. Results indicate that the pile's operationally optimal degree of inclination is approximately 5°. By exceeding this value, the instability in the surrounding soil under applied loads grows extensively in all the geotechnical properties considered. Cohesive soils tend to display poorer results compared to grained soils.     

Optimization of Wigley Hull Form in order to Ensure the Objective Functions of the Seakeeping Performance

The research performed in this paper was carried out to investigate the computational procedure to design seakeeping optimized ship hull form. To reach the optimized hull form, four stages should be done, which consists of： generate alternative hull form, seakeeping calculations, objective functions and optimization techniques. There are many parameters that may be determined in ship hull form optimization. This paper deals with developed strip theory for determining the seakeeping performance, genetic algorithm （GA） as optimization method, high order equations for curve fitting of the hull form and finally reaching to the minimum bow vertical motion in regular head waves. The Wigley hull is selected as an initial hull and carried to be optimized. Two cases are considered. For the first case, the only form coefficients of the hull （CB, CM, Cw, Cp） are changed and main dimensions （L, B, 7） are fixed. In the second case both hull form and main dimensions are varied simultaneously. Finally, optimized hull form and its seakeeping performances are presented. The results of optimization procedure demonstrate that the optimized hull forms yield a reduction in vertical motion and acceleration.     

作用在双圆柱桩上波浪力准确解和有限差分解的比较

The wave force exerted on vertical piles of offshore structures is the main criterion in designing them.In structures with more than one large pile,the influence of piles on each other is one of the most important issues being concerned in past researches.An efficient method for determining the interaction of piles is introduced in present research.First the wave force is calculated by the exact method using the diffraction theory,then in the finite difference numerical method the force is calculated by adding the velocity potentials of each pile and integration of pressure on their surface.The results showed that the ratio of the wave force on each of the double piles to a single pile has a damped oscillation around unity in which the amplitude of oscillation decreases with the increase in the spacing parameter.Also different wave incident directions and diffraction parameters were used and the results showed that the numerical solution has acceptable accuracy when the diffraction parameter is larger than unity.     

Experimental research on spray and combustion characteristics of the third generation conical spray

A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. High-speed photograph was used to investigate the spatial distribution characteristics of the new spray for cases of different impingement angles and needle valve opening pressures. The results show that, by applying spray impingement orientation, fuel jets spread along the cone surface as shape of sectors, so the dispersion of jets is increased obviously. Changing on impingement angle leads to variation of penetration, which is critical in homogeneous mixture preparation. Due to the flexibility of spray penetration in design, the spray impingement on liner is avoided in a great extent. The results also indicate that higher needle valve opening pressure results in longer penetration and larger spray angle after impingement. Combustion characteristics of the impinged conical spray were studied in the 1135 type diesel engine. The new impinged conical spray system work smoothly in full load range with better fuel economy and lower emissions of NOx and soot than the original test engine.     

毂帽鳍对调距桨推进效率影响的数值研究(英文)

Numerical simulation is investigated to disclose how propeller boss cap fins (PBCF) operate utilizing Reynolds-averaged Navier-Stokes (RANS) method. In addition, exploration of the influencing mechanism of PBCF on the open water efficiency of one controllable-pitch propeller is analyzed through the open water characteristic curves, blade surface pressure distribution and hub streamline distribution. On this basis, the influence of parameters including airfoil profile, diameter, axial position of installation and circumferential installation angle on the open water efficiency of the controllable-pitch propeller is investigated. Numerical results show: for the controllable-pitch propeller, the thrust generated is at the optimum when the radius of boss cap fins is 1.5 times of propeller hub with an optimal installation position in the axial direction, and its optimal circumferential installation position is the midpoint of the extension line of the front and back ends of two adjacent propeller roots in the front of fin root. Under these optimal parameters, the gain of open water efficiency of the controllable-pitch propeller with different advance velocity coefficients is greater than 0.01, which accounts for approximately an increase of 1%-5% of open water efficiency.     

Numerical analysis of the high skew propeller of an underwater vehicle

A numerical analysis based on the boundary element method (BEM) was presented for the hydrodynamic performance of a high skew propeller (HSP) which is employed by an underwater vehicle (UV). Since UVs operate at two different working conditions (surface and submerged conditions), the design of such a propeller is a cumbersome task. This is primarily due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different. Therefore, some factors are necessary for the design of the optimum propeller to utilize the power at the mentioned conditions. The design objectives of the optimum propeller are to obtain the highest possible thrust, minimum torque, and efficiency. In the current study, a 5-bladed HSP was chosen for running the UV. This propeller operated at the stern of the UV hull where the inflow velocity to the propeller was non-uniform. Some parameters of the propeller were predicted based on the UV geometrical hull and operating conditions. The computed results include the pressure distribution and the hydrodynamic characteristics of the HSP in open water conditions, and comparison of these results with those of the experimental data indicates good agreement. The propeller efficiency for both submerged and surface conditions was found to be 67% and 64%, respectively, which compared to conventional propellers is a significantly higher efficiency.     

Analysis of deformation of rotor and influence on the performance of gyro based on B-spline wavelet FEM

Some construct characteristics and composing material of the new Gyro＇ s rotor are introduced. Some factors resulting in deformation of the rotor surface are analyzed. Under different loads such as the fo,＇ce of deflecting center, the change of temperature, the fo,ce of pressure and couple factors, the deformation of rotor is analyzed with the wavelet finite element simulation software. The vector distributing map of rotor reformation is given. The deformation resulting from the pressure force of photon is studied. Finally, the influence on Gyro＇ s performance because of anomalous surface of rotor due to deformation of rotor is researched and the result is useful to forecast the performance of the drift of gyroscope. The disturbing moment resulting from the deformation of rotor can be compensated using the mathematic method, and provides an important reference for both design and optimization of the rotor.     

Scattering of surface water waves involving semi-infinite floating elastic plates on water of finite depth

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates,separated by a gap of finite width,floating horizontally on water of finite depth,are investigated in the present work for a two-dimensional time-harmonic case.Within the frame of linear water wave theory,the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions.Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem.In both the problems,the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates.Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations.The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration.The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.     

绞吸式挖泥船光刃绞刀的切削性能

为研究光刃绞刀的切削性能,采用数值分析软件LS-DYNA分析光刃绞刀和带齿绞刀的切削动力学过程,对比这2种绞刀在不同切削工况下对土壤和岩石的切削性能.结果表明:在切削岩石时,光刃绞刀在切削力和切削能耗方面的表现均优于带齿绞刀;在切削土壤时,光刃绞刀在切削力和切削能耗方面的表现与带齿绞刀相近.由此可见,将光刃绞刀应用于含杂物的软质土壤切削作业中具有一定的可行性.     

单耙齿切削黏土机理试验研究

黏土是疏浚工程中分布广泛且较为难挖的土质。为了分析黏土切削过程中的土体破坏机理，对2种不同含水率的黏土进行二维与三维切削试验研究。试验考虑不同切削角度（30°、45°和60°）和不同切削深度（50、100和150 mm）对黏土切削力的影响。通过切削力传感器测得切削过程产生的水平和垂直切削力；并在切削刀具表面不同位置布置压力传感器，测得切削过程中刀具不同位置受到的土体压力；布置摩擦力传感器，测得切削过程产生的摩擦力；在切削过程中观察土体的变形和破坏形态。通过黏土的切削试验，讨论不同的切削参数对黏土切削力的影响，分析黏土切削的土体破坏机理。     

6500m3/h绞吸船用泥泵四叶片叶轮研发

为适应绞吸挖泥船超长排距时的施工需要,在6500m³/h绞吸挖泥船原三叶片高效高压泥泵的基础上,保证叶轮外形尺寸不变、叶轮流道通过能力不下降的情况下,分别对叶轮轴面和轴面流线进行水力设计,设计叶轮为四叶片扭曲叶片,并结合数值模拟对叶片包角进行优化计算,确定叶片包角为138°。通过模型泵试验,对比测试与模拟计算结果,验证叶轮的水力性能。通过对比四叶片与原三叶片高效高压泥泵的性能参数,预测两者在不同土质、不同排距下的生产率与能耗情况。结果表明,四叶片泥泵扬程比原三叶片高效高压泥泵提高了18 m以上,最高效率达到86%,且通过球径均为425 mm;土质为0.2 mm细砂时,研发泥泵的生产率提高了9%以上,排距提高了14%以上,耗功最小值降低了约3.5%。     

基于多目标遗传算法的复式转叶舵机结构优化

针对舰船转叶舵机运动时舵叶与水动力之间存在强力位耦合的问题,设计一种新型复式液压摆动缸转舵机构。为减小结构整体占地面积,基于多目标遗传算法(Multi-Objective Genetic Algorithm, MOGA)建立以复式摆动缸壳体内径、力矩解耦缸转子内径、驱动缸转子轮毂直径、动静叶片高度、动静叶片宽度和壳体厚度几何尺寸为设计变量的多目标优化模型。在使用遗传算法(Genetic Algorithm, GA)求解非线性约束条件下的多变量优化问题时,通过设计罚函数,将适应度函数与约束条件分离以处理约束条件,根据设定的准则择优筛选最优尺寸参数。通过有限元软件ANSYS对摆动缸壳体、力矩解耦缸转子和驱动缸转子进行应力应变分析。结果表明,在满足结构强度、刚度和安全因数的前提下,复式摆动缸结构尺寸最优,验证优化后结构的可靠性。     

操纵运动潜艇水动力计算研究

采用FLUENT软件对一模型艇在不同漂角下运动的升沉力系数和表面压力分布进行计算,验证了该软件解决此类问题的有效性。在此基础上,对作操纵运动的潜艇主体和带附体的全艇体,在一定攻角和漂角下的垂向力、俯仰力矩和横向力、纵倾力矩进行计算,取得了工程上较为满意、实用的精度,为解决潜艇操纵运动水动力预报的困难做出了有益的探索。     

基于遗传算法的水平轴海流发电机叶片优化方法

提出一种基于遗传算法优化(GA)的水平轴海流发电机叶片优化方法,采用Xfoil和BEMT作为分析工具,适用于二维翼型和三维叶片的多目标优化,并以此为基础编写一套叶片优化程序。该优化方法在增加叶片获能效率和减小推力方面具有显著效果,同时对于翼型性能的提升也同样出色。     

天津港区硬质黏土切削过程的有限元模拟

硬质黏土的挖掘存在效率低的问题,需要研究该种土质的切削机理.利用数值模拟技术,建立刀齿切削硬质黏土的三维分析模型.土体的本构模型采用非线性弹塑性模型,应用单元损伤失效准则模拟硬质黏土的切屑,并基于显式积分算法实现了硬质黏土全物理过程的数值仿真,分析不同时刻的土体变形状态,得到刀齿的切削荷载.结果表明,对于所选定的硬质黏...     

基于正交—主元分析对柴油机燃烧参数匹配优化

基于电控化改造后的4190柴油机，利用AVL—FIRE软件建立天然气—柴油双燃料发动机燃烧室高压循环模型，并与原机进行验证。采用正交试验法以指示功率和NOX生成量为优化目标，并对燃烧参数进行匹配，进行仿真试验。利用主成分分析法对仿真结果进行优化分析，将优化结果与正交试验结果对比并最终代入模型进行检验。通过正交—主成分分析得出：柴油机运行参数对低温燃烧影响的主次顺序与正交试验设计基本一致，且具有更高的可靠性和准确度。优化后的参数为：天然气替代率45%，进气压力0.224MPa，EGR率12.5%，进气温度335.15K，喷油提前角22.7°对应的指示功率为37.83kW，NOX生成质量分数比原机降低78.73%，比极差分析最优组合降低10.92%。该优化方案在保证动力性的前提下可以有效地降低NOX排放。     

基于正交试验的喷水推进器参数优化设计

采用正交实验法对喷水推进器进行参数优化设计,以推力作为评价指标,基于信噪比的概念,分析了转子叶片数、定子叶片数以及定子安装角度对喷水推进器参数的影响。结果表明：定子叶片数在影响因素中的贡献度较低,转子叶片数与定子安装角度有着较强的交互作用,且呈负相关关系,当转子叶片数较多时,流体轴向速度较大,因此定子安装角度不宜过大。通过正交实验与非线性理论模型的构建,基于自适应粒子群算法寻优,得出最佳化参数组合为转子叶片4片、定子叶片数为5片以及定子安装角度为10度,优化结果经类比实验性能测试,效果较佳。     

螺旋桨叶剖面优化设计比较研究

比较研究了船舶螺旋桨最高空泡起始航速的叶剖面优化设计方法。优化设计方法由剖面参数表达、空泡斗预报和最佳空泡起始性能遗传算法翼型优化三部分组成。Eppler方法采用10个参数表达任一翼型,已被有效应用到最高起始航速的螺旋桨叶剖面优化设计中。除了Eppler方法中的设计参数,剖面参数表达也可采用B样条曲线的控制点参数实现。对上述两种剖面参数表达方法进行了叶剖面优化设计比较研究,得到了一些结论。