Optimization of Center of Gravity Position and Anti-Wave Plate Angle of Amphibious Unmanned Vehicle Based on Orthogonal Experimental Method

When the amphibious vehicle navigates in water,the angle of the anti-wave plate and the position of the center of gravity greatly influence the navigation characteristics.In the relevant research on reducing the navigation resistance of amphibious vehicles by adjusting the angle of the anti-wave plate,there is a lack of scientific selection of parameters and reasonable research of simulation results by using mathematical methods,and the influence of the center of gravity position on navigation characteristics is not considered at the same time.To study the influence of the combinations of the angle of the anti-wave plate and the position of the center of gravity on the resistance reduction characteristics,a numerical calculation model of the amphibious unmanned vehicle was established by using the theory of computational fluid dynamics,and the experimental data verified the correctness of the numerical model.Based on this numerical model,the navigation characteristics of the amphibious unmanned vehicle were studied when the center of gravity was located at different positions,and the orthogonal experimental design method was used to optimize the parameters of the angle of the anti-wave plate and the position of the center of gravity.The results show that through the parameter optimization analysis based on the orthogonal experimental method,the combination of the optimal angle of the anti-wave plate and the position of the center of gravity is obtained.And the numerical simulation result of resistance is consistent with the predicted optimal solution.Compared with the maximum navigational resistance,the parameter optimization reduces the navigational resistance of the amphibious unmanned vehicle by 24%.

Theory and practice for assessing structural integrity and dynamical integrity of high-speed trains

Purpose–The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system.This paper aims to define and substantiate the assessment of the structural integrity and dynamical integrity of high-speed trains in both theory and practice.The key principles and approacheswill be proposed,and their applications to high-speed trains in Chinawill be presented.Design/methodology/approach–First,the structural integrity and dynamical integrity of high-speed trains are defined,and their relationship is introduced.Then,the principles for assessing the structural integrity of structural and dynamical components are presented and practical examples of gearboxes and dampers are provided.Finally,the principles and approaches for assessing the dynamical integrity of highspeed trains are presented and a novel operational assessment method is further presented.Findings–Vehicle system dynamics is the core of the proposed framework that provides the loads and vibrations on train components and the dynamic performance of the entire vehicle system.For assessing the structural integrity of structural components,an open-loop analysis considering both normal and abnormal vehicle conditions is needed.For assessing the structural integrity of dynamical components,a closed-loop analysis involving the influence of wear and degradation on vehicle system dynamics is needed.The analysis of vehicle system dynamics should follow the principles of complete objects,conditions and indices.Numerical,experimental and operational approaches should be combined to achieve effective assessments.Originality/value–The practical applications demonstrate that assessing the structural integrity and dynamical integrity of high-speed trains can support better control of critical defects,better lifespan management of train components and better maintenance decision-making for high-speed trains.

Investigation on nonlinear rolling dynamics of amphibious vehicle under wind and wave load

Nonlinear amphibious vehicle rolling under regular waves and wind load is analyzed by a single degree of freedom system.Considering nonlinear damping and restoring moments,a nonlinear rolling dynamical equation of amphibious vehicle is established.The Hamiltonian function of the nonlinear rolling dynamical equation of amphibious vehicle indicate when subjected to joint action of periodic wave excitation and crosswind,the nonlinear rolling system degenerates into being asymmetric.The threshold value of excited moment of wave and wind is analyzed by the Melnikov method.Finally,the nonlinear rolling motion response and phase portrait were simulated by four order Runge-Kutta method at different excited moment parameters.

Parametric analysis of wheel wear in high-speed vehicles

In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the actual measured track irregularities and line conditions were considered. The wear depth of the wheel profile was calculated by the well-known Archard wear law. Through this model, the influence of the wheel profile, primary suspension stiffness, track gage, and rail cant on the wear of wheel profile were studied through multiple iterafive calculations. Numerical simulation results show that the type XP55 wheel profile has the smallest cumulative wear depth, and the type LM wheel profile has the largest wear depth. To reduce the wear of the wheel profile, the equivalent conicity of the wheel should not be too large or too small. On the other hand, a small primary vertical stiffness, a track gage around 1,435-1,438 mm, and a rail cant around 1：35-1：40 are beneficial for dynamic performance improvement and wheel wear alleviation.

Hydrodynamics Research on Amphibious Vehicle Systems:Modeling Theory

For completing the hydrodynamics software development and the engineering application research on the amphibious vehicle systems, hydrodynamic modeling theory of the amphibious vehicle systems is elaborated, which includes to build up the dynamic system model of amphibious vehicle motion on water, gun tracking-aiming-firing, bullet hit and armored check-target, gunner operating control, and the simulation computed model of time domain for random sea wave.

Aerodynamic/control integrated optimization method for unpowered high-speed vehicle configuration design

The unpowered high-speed vehicle experiences a significant coupling between the disciplines of aerodynamics and control due to its characteristics of high flight speed and extensive maneuverability within large airspace.The conventional aircraft conceptual design process follows a sequential design approach,and there is an artificial separation between the disciplines of aerodynamics and control,neglecting the coupling effects arising from their interaction.As a result,this design process often requires extensive iterations over long periods when applied to high-speed vehicles,and may not be able to effectively achieve the desired design objectives.To enhance the overall performance and design efficiency of high-speed vehicles,this study integrates the concept of Active Control Technology(ACT)from modern aircraft into the philosophy of aerodynamic/control integrated optimization.Two integrated optimization strategies,with differences in coupling granularity,have been developed.Subsequently,these strategies are put into action on a biconical vehicle that operates at Mach 5.The results reveal that the comprehensive performance of the synthesis optimal model derived from the aerodynamic/control integrated optimization strategy is improved by 31.76%and 28.29%respectively compared to the base model under high-speed conditions,demonstrating the feasibility and effectiveness of the method and optimization strategies employed.Moreover,in comparison to the single-stage strategy,the multi-stage strategy takes into deeper consideration the impact of control capacity.As a result,the control performance of the synthesis opti-mal model derived from the multi-stage strategy improves by 13.99%,whereas the single-stage strategy only achieves a 5.79%improvement.This method enables a fruitful interaction between aerodynamic configuration design and control system design,leading to enhanced overall performance and design efficiency.Furthermore,it improves the controllability of high-speed vehicles,mitigating the risk of mission failure resulting from an ineffective control system.

Hierarchical model updating for high-speed maglev vehicle/guideway coupled system based on multiobjective optimization

The high-speed maglev vehicle/guideway coupled model is an essential simulation tool for investigating vehicle dynamics and mitigating coupled vibration.To improve its accuracy efficiently,this study investigated a hierarchical model updating method integrated with field measurements.First,a high-speed maglev vehicle/guideway coupled model,taking into account the real effect of guideway material properties and elastic restraint of bearings,was developed by integrating the finite element method,multi-body dynamics,and electromagnetic levitation control.Subsequently,simultaneous in-site measurements of the vehicle/guideway were conducted on a high-speed maglev test line to analyze the system response and structural modal parameters.During the hierarchical updating,an Elman neural network with the optimal Latin hypercube sampling method was used to substitute the FE guideway model,thus improving the computational efficiency.The multi-objective particle swarm optimization algorithm with the gray relational projection method was applied to hierarchically update the parameters of the guideway layer and magnetic force layer based on the measured modal parameters and the electromagnet vibration,respectively.Finally,the updated coupled model was compared with the field measurements,and the results demonstrated the model’s accuracy in simulating the actual dynamic response,validating the effectiveness of the updating method.

Influence of Vehicle Parameters on Critical Hunting Speed Based on Ruzicka Model

While introducing foreign advanced technology and cooperating with Chinese famous research institutes,the high-speed vehicles are designed and take the major task of passenger transport in China.In high-speed vehicle,the characteristic of shock absorber is an important parameter which determines overall behavior of the vehicle.The most existing researches neglect the influence of the series stiffness of the shock absorber on the vehicle dynamic behavior and have one-sided views on the equivalent conicity of wheel tread.In this paper,a high speed passenger vehicle in China is modeled to investigate the effect of the parameters taking series hydraulic shock absorber stiffness into consideration on Ruzicka model.Using the vehicle dynamic model,the effect of main suspension parameters on critical speed is studied.In order to verify the reasonableness of shock absorber parameter settings,vibration isolation characteristics are calculated and the relationship between suspension parameters and the vehicle critical hunting speed is studied.To study the influence of equivalent conicity on vehicle dynamic behavior,a series of wheel treads with different conicities are set and the vehicle critical hunting speeds with different wheel treads are calculated.The discipline between the equivalent conicity of wheel tread and critical speed are obtained in vehicle nonlinear system.The research results show that the critical speed of vehicle much depends on wheelset positioning stiffness and anti-hunting motion damper,and the series stiffness produces notable effect on the vehicle dynamic behavior.The critical speed has a peak value with the equivalent conicity increasing,which is different from the traditional opinion in which the critical speed will decrease with the conicity increasing.The relationship between critical speed and conicity of wheel tread is effected by the suspension parameters of the vehicle.The study results obtained offer a method and useful data to designing the parameters of the high speed vehicle and simulation study.

Progress in high-speed train technology around the world

This is a review of high-speed train development in the sense of technology advances all over the world. Three generations of high-speed trains are classified according to their technical characteristics and maximum operating speed. Emphasis is given to the newly developed high-speed train in China, CRH380. The theoretical foundations and future development of CRH380 are briefly discussed.

Damage Tolerance Assessment of a Brake Unit Bracket for High-Speed Railway Welded Bogie Frames

The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.

Development of new electromagnetic suspension-based high-speed Maglev vehicles in China:Historical and recent progress in the field of dynamical simulation

High-speed Maglev is a cutting-edge technology brought back into the focus of research by plans of the Chinese government for the development of a new 600 km/h Maglev train.A Chinese‐German cooperation with industrial and academic partners has been established to pursue this ambitious goal and bring together experts from multiple disciplines.This contribution presents the joint work and achievements of CRRC Qingdao Sifang,thyssenkrupp Transrapid,CDFEB,and the ITM of the University of Stuttgart,regarding research and development in the field of high‐speed Maglev systems.Furthermore,an overview is given of the historical development of the Transrapid in Germany,the associated development of dynamical simulation models,and recent developments regarding high-speed Maglev trains in China.

Wear characteristics and prediction of wheel profiles in high-speed trains

Wheel/rail relationship is a fundamental problem of railway system. Wear of wheel profiles has great effect on vehicle performance. Thus, it is important not just for the analysis of wear characteristics but for its prediction. Actual wheel profiles of the high-speed trains on service were measured in the high-speed line and the wear characteristics were analyzed which came to the following results. The wear location was centralized from-15 mm to 25 mm. The maximum wear value appeared at the area of 5 mm from tread center far from wheel flange and it was less than 1.5 mm. Then, wheel wear was fitted to get the polynomial functions on different locations and operation mileages. A binary numerical prediction model was raised to predict wheel wear. The prediction model was proved by vehicle system dynamics and wheel/rail contact geometry. The results show that the prediction model can reflect wear characteristics of measured profiles and vehicle performances.

Research of inverse mathematical model to high-speed trains

Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stability and passenger safety.Since wheel/rail contact forces of high-speed train are very difficult to measure directly,a new estimation process for wheel/rail contact forces was introduced in this work.Based on the state space equation,dynamic programming methods and the Bellman principle of optimality,the main theoretical derivation of the inversion mathematical model was given.The new method overcomes the weakness of large fluctuations which exist in current inverse techniques.High-speed vehicle was chosen as the research object,accelerations of axle box as input conditions,10 degrees of freedom vertical vibration model and 17 degrees of freedom lateral vibration model were established,respectively.Under 250 km/h,the vertical and lateral wheel/rail forces were identified.From the time domain and frequency domain,the comparison of the results between inverse and SIMPACK models were given.The results show that the inverse mathematical model has high precision for inversing the wheel/rail contact forces of an operation high-speed vehicle.

轮式高速两栖车辆水上航行阻力成分占比分析

对某轮式高速两栖车辆水上航行工况全航速范围的阻力成分占比开展分析,为其水动力构型的优化设计提供方向性指导。采用CFD软件FINETM/Marine开展带自由面的模型阻力数值计算,通过与模型试验结果对比验证了数值计算方法。通过叠模数值计算确定了对应各航速的水粘压阻力,其中针对高速时的“干方尾”现象,提出以动态吃水平面切割尾波谷自由面形成尾部导流体的叠模计算几何模型构建方法。结合带自由面阻力计算得到的空气阻力和其他水阻力成分,分析了不同阻力成分的占比及其随航速变化的规律。结果表明,该轮式两栖车全速度范围内的水阻力在总阻力中的占比都高于90%;排水航行阶段,水粘压阻力占比最高,约为45%~70%;过渡航行阶段,兴波和飞溅阻力占比最高,约为45%~70%;滑行阶段,水摩擦阻力占比随航速增大迅速提高,设计航速时在总阻力中占比约为36%。

水陆两栖车辆水上运动特性实时仿真系统研究

为解决水陆两栖车辆水动力性能参数获取难度大、运动姿态预测慢等问题,设计一种两栖车辆水上运动特性实时仿真系统,实现仿真模型的驱动、运动姿态预测以及数据的监测和输出,通过动态流体-物体相互作用数值计算方法对车体动力学系数进行修正,提升了实时仿真系统的精度。在此基础上研制试验样车,对不同工况下实时仿真系统的准确性进行验证。试验结果表明:所构建的两栖车辆水上运动特性实时仿真系统兼具计算精度和计算效率,可以快速准确地预测车辆的运动姿态,适用于多种复杂工况,具有姿态预测的泛用性。新系统在两栖车辆研制阶段、驾驶员培训、半实物仿真演练、复杂环境模拟等方面具有较强的应用价值和应用前景。

喷水推进两栖车辆水面航行特性试验与数值计算研究

兼具陆上机动、水面航行及水陆交界地带作业能力的特种水陆两栖车辆,是未来多域协同系统中重要组成部分。以喷水推进两栖车辆为研究对象,基于船模拖曳水池试验,获得了弱约束条件下喷水推进两栖车辆的航行特性,建立了喷水推进器与两栖车辆一体化操控的数值计算方法,对喷水推进两栖车辆水动力性能展开研究并充分验证了数值计算方法的准确性,对比分析了两栖车辆设计航速下拖曳与约束自航条件下的航行特性。相比于常规的“船-泵”一体化研究,从两栖车的角度丰富了喷水推进器和水面航行体相互影响的研究。结果表明,约束自航条件下车体阻力相比无喷水推进条件下阻力增加17.6%,喷水推进器运行导致的车辆姿态变化是造成增阻的主要因素。约束自航条件与拖曳条件相比,虚长度延伸长度从-0.864 X/L(X为距车辆重心长度,L为两栖车总长)增加至-1.513 X/L。与此同时,鸡尾流波高高度与发散波面积显著增加,从0.037 H/L(H为波面高度)增加至0.061 H/L,增加了尾流场附近能量损失。

基于神经网络算法的水陆两栖无人艇控制系统研究

针对近海登陆两栖作战等不适合士兵冲锋陷阵的高危环境,提出了基于神经网络算法的水陆两栖无人艇控制系统研究,伺服运动控制为控制系统的关键核心之一。鉴于目前传统两栖无人艇运动控制系统PID算法控制精度低、误差大、需人工调节参数等缺陷,提出BP-PID神经网络算法,同时融合GWO算法(灰狼算法),利用其搜索能力优化网络权值和阈值,加快网络收敛,提高控制精度。首先,对水陆两栖无人艇的控制系统进行需求分析,继而完成两栖无人艇伺服运行控制系统数学和控制模型设计、神经网络算法构架等设计,将设计的算法引入两栖无人艇运动控制系统中,并且进行实验验证,得到行驶曲线。结果表明控制系统运行稳定、响应速度快、误差小,行驶轨迹精确等优点。为实现不适合士兵直达近海登陆作战高危未知环境提升作战力,保护士兵安全有很重要现实意义和实用工程价值,为未来武器装备的智能化研究发展提供借鉴。

M型超高速两栖车辆静水航行数值计算分析

两栖车辆的水动力构型研究正逐步由中低航速构型转向高航速构型设计。为解决两栖车高航速阻力大、兴波强烈等问题,提出M型超高速两栖车辆构型,并基于计算流体力学方法对该车型不同直航工况进行了数值分析。分析结果表明,该构型能够通过吸收首兴波提升车体整体水动升力并显著降低两栖车辆水上航行阻力,且通过合理的重心位置设计能达成较好的纵向稳定性。

两栖车辆发动机增压匹配及控制策略研究

针对两栖车辆在水陆工况下的功率需求,开展车辆在两种工况下的动力系统增压匹配及控制策略研究。建立了车用发动机在两种工况条件下的一维仿真模型,对增压器、放气阀等关键部件进行了标定,并对整机仿真模型进行了实验验证。以此模型为基础完成了两种工况条件下的增压系统匹配,研究两栖工况下的增压发动机输出特性,制定两种工况下的废气旁通阀开度控制策略。结果表明,计算匹配的增压器和控制策略满足两栖车辆在不同工况下的功率需求。

两栖装甲车水上运动仿真平台开发与应用研究

为设计及验证两栖装甲突击车大风浪条件下的火控算法,需要开发其实时仿真平台。传统单刚体车辆动力学模型无法反映车体-炮塔-炮管间复杂的动力学耦合关系,不适合于高动态特性的火控仿真。使用twist-wrench方法建立了车辆的多刚体动力学模型,根据车体与视景中生成的海浪之间的运动关系计算浮力和水动力,水动力系数则事先通过计算流体力学方法得出。以一种滑模控制器为例验证了此系统作为火控算法开发及验证平台的有效性。