Application of Semi-Hertzian Approach to Predict the Dynamic Behavior of Railway Vehicles Through a Wear Evolution Model

Wear prediction due to the wheel-rail interaction in a railway vehicle has a significant role in the view of running stability (critical speed), dynamic performance and maintenance scheduling. In this article, we have focused on the estimation of wear distribution on the wheel profile through co-simulation between the vehicle and the wear evolution models, built in the multi-body simulation (MBS) software ADAMS (VI-Rail) and MATLAB environments, respectively. As the shape of the contact patches varies from elliptical to non-elliptical depending upon the contact patch location on the rail and the wheel, the contact forces/stresses are calculated by using a combined formulation of semi-Hertzian approach with modified FASTSIM. The wear distribution is obtained using Archard’s wear model. The wheel profiles are updated after calculating the wear depth for a particular distance travelled by the vehicle. The dynamic behavior of the vehicle with the worn wheel profile is utilized to predict additional wear during a further fixed distance of travel and this profile updating and dynamic simulation process is repeated. The vehicle’s dynamic performance and passenger comfort are evaluated for various levels of wheel wear.     

Static and Dynamic Slider Air-Bearing Behavior in Heat-Assisted Magnetic Recording Under Thermal Flying Height Control and Laser System-Induced Protrusion

The air bearing’s response to regions of elevated temperature on its bounding surfaces (the slider and disk) may be an important consideration in the head–disk interface design of heat-assisted magnetic recording (HAMR) systems. We implement the general non-isothermal molecular gas lubrication equation into an iterative static solver and dynamic air-bearing solver to evaluate the effect of localized heating of the air-bearing surface (ABS) due to the near-field transducer (NFT). The heat-dissipating components in our simplified HAMR design are the NFT, laser diode, and thermal flying height control (TFC) heater. We investigate the effect of each HAMR slider component on ABS temperature and thermal deformation and the slider’s flying height. The NFT induces a localized thermal spot and protrusion on the larger TFC bulge, and it is the location of maximum temperature. This ABS temperature profile alters the air-bearing pressure distribution, increasing the pressure at the hot NFT location compared with predictions of an isothermal air-bearing solver, so that the center of the pressure acting on the ABS is slightly closer to the trailing edge, thereby decreasing the pitch angle and increasing the minimum flying height. Other researchers have shown that the NFT’s thermal response time may be much faster than its protrusion response time (Xu et al. in IEEE Trans Magn 48:3280–3283, 2012). The slider’s dynamic response to a time-varying NFT thermal spot on the ABS while the combined TFC and NFT induced thermal protrusion remains constant is investigated with our dynamic air-bearing solver. We simulate the slider’s step response to a suddenly applied ABS temperature profile and a pulsed temperature profile that represents laser-on over data zones and laser-off over servo zones. The sudden (step) or rapid (pulse) increase in ABS temperature induces a sudden or rapid increase in pressure at the NFT location, thereby exciting the air bearing’s first pitch mode. For the slider design and simulation conditions used here, the result of the pitch mode excitation is to alter the position of the center of pressure in the slider’s length direction, thereby changing the pitch moment. In response, the pitch angle and minimum flying height change. The step response decays after approximately 0.15 ms. Because the laser duty cycle is much shorter than this response time, a periodic disturbance is predicted for the center of pressure coordinate, pitch angle, and minimum flying height. The peak-to-peak minimum flying height modulations are relatively small (only up to 0.126 nm); more significantly, the time-averaged minimum flying height increases 0.5 nm for the NFT that reached 208 °C compared to simulations of the isothermal ABS at ambient temperature.     

六轮车辆滑移转向动力学建模和运动特性分析

轮式滑移转向车辆由于其机动灵活和结构简单可靠而具有广泛的应用价值。针对一种六轮车辆,车轮触地点的速度分析、轮轴转动副摩擦分析和车辆力平衡关系,建立了稳态滑移转向时的动力学模型,分析了车辆主要结构参数和左右侧车轮转速的不同对滑移转向的瞬心位置、转向角速度和车轮所需力矩的影响规律。研究结果可为六轮车辆的合理设计和实现滑移转向时的轮速控制与驱动提供理论依据。     

基于随机动态规划的混合动力履带车辆能量管理策略

混合动力履带车辆采用发动机—发电机组和电池组混合供电,必须设计满足车辆动力性和燃油经济性约束的能量管理策略。针对串联式混合动力履带车辆,提出一种基于随机动态规划的能量管理策略设计方法。以实车行驶试验数据为目标工况,将驾驶员功率需求抽象为随车速变化的马尔科夫过程。建立发动机—发电机组、电池组以及直流母线功率平衡动态模型。以目标工况中燃油消耗及电池最终荷电状态的偏差作为车辆的优化控制成本函数,建立车辆能量管理最优控制问题。采用策略迭代法求解以发动机转速、电池组荷电状态、车速和驾驶员功率需求为输入、发动机电子节气门为输出的最优控制策略。所得控制策略通过基于前向车辆模型的仿真以及行驶试验验证。结果表明,相对于原发动机多点控制策略,所得最优控制在满足目标工况同时,燃油经济性明显提高。     

Modeling and control of an electronic-vacuum booster for vehicle cruise control

A mathematical model and control laws for an Electronic-Vacuum Booster (EVB) For application to vehicle cruise control will be presented. Also this paper includes performance test result of EVB and vehicle cruise control experiments. The pressure difference between the vacuum chamber and the apply chamber is controlled by a PWM-solenoid-valve. Since the pressure at the vacuum chamber is identical to that of the engine intake manifold, the output of the electronic-vacuum booster is sensitive to engine speed. The performance characteristics of the electronic-vacuum booster have been investigated via computer simulations and vehicle tests. The mathematical model of the electronic-vacuum booster developed in this study and a two-state dynamic engine model have been used in the simulations. It has been shown by simulations and vehicle tests that the EVB-cruise control system can provide a vehicle with good distance control performance in both high speed and low speed stop and go driving situations.     

Design of a stable controller for accurate path tracking of automated guided vehicles systems

This paper deals with the path tracking and stability of motion of automated guided vehicle systems and wheeled mobile robots. A two degree-of-freedom dynamic model is developed to represent the plane motion of the vehicle. This model along with the instantaneous posture errors (position and orientation errors) of the vehicle are used to formulate their path-tracking problem in state space format. Implementation of stability criterion and application of the actual physical limits of the pertinent parameters of the system are the strategies used to design the controller. It is shown that implementation of a control strategy based on the vehicles’ position and orientation errors gives satisfactory results in vehicles’ path tracking. The feasibility of the approach and the performance of the controlled system are demonstrated by using a prototype vehicle.     

Distributed coordinated attitude tracking control for spacecraft formation with communication delays

This paper investigates the distributed coordinated attitude tracking control problem for spacecraft formation with time-varying communication delays under the condition that the dynamic leader spacecraft is a neighbor of only a subset of follower spacecrafts. We consider two cases for the leader spacecraft: i) the attitude derivative is constant, and ii) the attitude derivative is time-varying. In the first case, a distributed estimator is proposed for each follower spacecraft by using its neighbors’ information with communication delays. In the second case, to express the dynamic leader’s attitude, an improved distributed observer is developed to estimate the leader’s information. Based on the estimated values, adaptive coordinated attitude tracking control laws are designed to compensate for parametric uncertainties and unknown disturbances. By employing the Lyapunov–Krasovskii functional approach, the attitude tracking errors and estimation errors are proven to converge to zero asymptotically. Numerical simulations are presented to illustrate the effectiveness of theoretical results.     

受生物启发的扑翼飞行器弹跳机构概念设计

针对扑翼飞行器自主起降能力缺失、严重影响其适用场景的问题，开展了仿生弹跳机构设计研究。对鸟类跳跃起飞过程中典型的运动状态进行分析，结合其各阶段的后肢骨骼结构、重心、力、速度等运动变化规律，对扑翼飞行器弹跳起飞动态过程进行了设计。基于鸟腿的骨骼解剖学结构，设计了闭链齿轮-五杆仿鸟腿弹跳机构，并基于D-H法推导出弹跳机构运动学方程，利用拉格朗日方程建立了弹跳机构起跳阶段的动力学方程。对弹跳机构进行了详细结构设计，采用ADAMS对简化的弹跳模型进行了仿真分析。仿真结果显示，借助该仿生弹跳机构，扑翼飞行器系统质心速度达到8.4 m/s，大于“信鸽”飞行器起飞所需的速度7.9 m/s，具备弹跳起飞的可能性。     

自动变速器液压系统动态响应特性试验研究

为满足不断提高的车辆换挡品质的控制要求,以某6挡液力机械自动变速器的液压系统为研究对象,在分析其工作原理的基础上试制了其中的核心部件--换挡控制回路,通过搭建液压系统测试平台对其进行动态响应特性试验,得到了换挡过程中各离合器换挡控制回路输出压力的动态响应特性曲线。试验结果表明,液压系统中各电磁阀控制的换挡控制回路的压力响应时间能满足实际换挡品质控制的要求,并得到油温变化对换挡控制回路的稳态压力和动态响应的影响。研究结果可以为自动变速器换挡品质控制的设计和优化提供有效依据。     

Clutch wear prediction via a deterministic-stochastic modeling approach

The front surface temperature of a clutch pressure plate is studied for clutch wear prediction. A combined deterministic plus stochastic modeling approach is proposed to fit the front surface temperature data. The underlying clutch engagement process is explained by a deterministic function, whereas the inherent dynamics are explained by the stochastic model. The results of the combined modeling approach indicate that the front surface temperature can be modeled accurately to within ± 4°F.     

转K7柔性副构架多体系统动力学建模研究

高速和重载是中国铁路发展的两个重要方向,铁道车辆的轻量化设计理念也被普遍采用。但轻量化设计却导致许多部件弹性变形比较明显,影响车辆动力学性能。以往将车辆各部件全部考虑成刚体的刚体动力学得出的结论与实际差距较大。因此,将弹性变形比较明显的部件考虑成柔性体,建立刚柔耦合的多体动力学模型来仿真是目前铁道车辆动力学的发展方向之一。以转K7转向架为例,详细分析介绍利用ANSYS和SIMPACK软件建立柔性副构架刚柔耦合动力学模型的建模思路和方法。     

Highly precise determination of the state of charge of vehicular battery

An intelligent battery sensor is an important component for vehicular energy management, and the precision of online estimation of the state of charge determines sensor’s performance. A simple equivalent circuit was employed to describe the dynamic properties of vehicle lead-acid batteries. A model is reported to estimate the state of charge using the approximately linear relationship of open circuit voltage with this parameter. A time-varying circuit of the model was prepared and an identification model was derived to improve the accuracy. A method that employed a cascaded combination of double improved extended Kalman filters is reported and employed in a demonstration intelligent battery sensor. This approach has higher precision and speed in estimating the state of charge compared to previous protocols.     

基于两级气压伺服系统的高速受电弓主动控制研究

针对弹性链型悬挂接触网利用有限元法建立接触网模型,采用多体动力学建立受电弓模型,通过接触力元将接触网和受电弓进行耦合建立弓网耦合模型.然后建立气压伺服系统数学模型,根据车速信号采用比例控制策略控制升弓气囊提供弓网静态接触压力,根据采集得到的动态接触力信号采用模糊控制策略控制空气弹簧提供动态接触压力的补偿力.作动器分别作用于下臂杆和弓头悬挂,通过底架上的低频调节和弓头上的高频调节两级方式,主动控制接触压力,实现高速受电弓的稳定受流.     

A novel fractional order PID navigation guidance law by finite time stability approach

In this paper, a novel fractional order proportional–integral–differential navigation guidance law utilizing finite time stability approach is presented in order to achieve robust performance for intercepting incoming targets. The proposed guidance law is designed following three-loop guidance and control scheme, considering the interceptor’s nonlinear 6 degrees-of-freedom model. In the outer loop, normal acceleration commands are generated by the proposed guidance law. In the intermediate loop, these commands are converted into equivalent body rate commands, which are tracked by dynamic inversion based autopilot in the inner loop. A fractional order circle criterion is developed for the finite time stability analysis of this proposed guidance law, whose stability conditions give an analytical bound for the flight up time in which stability can be insured. Extensive 6 degrees-of-freedom simulations and a variety of comparison studies against maneuvering targets are implemented to demonstrate the effectiveness of the proposed guidance law. The simulation results show that the proposed guidance law has better performance when comparing with the proportional navigation and proportional–integral–differential navigation guidance laws.     

DCT车辆起步及换挡过程双离合器H∞鲁棒控制

根据自主研发的双离合器自动变速器（DCT）结构和工作原理,建立了DCT车辆起步及换挡过程动力学模型。考虑起步及换挡过程中发动机扭矩波动及油门踏板抖动等不确定性因素,基于Riccati不等式和线性矩阵不等式设计了H∞鲁棒控制器,分析了冲击度和滑摩功两项离合器接合性能指标,探讨了离合器最优传递扭矩的求解问题,并与线性二次型最优控制策略进行了仿真对比分析,结果表明：H∞鲁棒控制可以较好地解决DCT车辆起步与换挡过程离合器压力控制问题,并能显著地改善离合器控制的鲁棒性能。     

基于虚拟激励法的三维随机路面仿真

通过改进的虚拟激励法原理,在现有二维路面谱的基础上,从空间路面频率谱出发,将之拓展到三维空间内的路面谱,给出模拟随机路面谱的方法。同时,为了给虚拟样机仿真分析提供较为复杂三维仿真路面环境,基于单点FFT路面不平度时域模型,建立了三维FFT随机路面数学模型,并实现了其在Matlab中的仿真;依据改进的虚拟激励法理论,建立了生成三维路面文件的通用模型,包括节点的生成和单元生成算法,并导入Adams形成所需的三维路面仿真环境。应用上述方法生成C级路面.对所选择的车辆样机进行了行驶平顺性仿真,与GB/T 13441—92标准对比分析得到了该车行驶平顺舒适性的合理时间。     

Transfer function modeling of structural vibration of complex aerospace structures based on finite element analysis

An approach to establish the transfer function of complex aerospace structures to express their structural vibration behavior through finite element modeling is proposed. The fundamental idea of the approach is to characterize the vibrations of complicated structures through the transfer function model for an advanced control system design, while the parameters of the model are identified from the response data obtained through finite element analysis. The proposed method comprises four steps, namely, finite element modeling and validation, data preparation based on the finite element analysis, parameter identification of the transfer function, and model validation, and is presented from both frequency and time domains. The developed approach is applied to a cantilever beam, a strap-on launch vehicle, and a local part of the aerospace structure to demonstrate the method’s effectiveness and satisfactory performance.     

纯电动汽车能量回馈效率特性测试分析

进行高效的能量回馈,可有效延长纯电动车辆续驶里程,而能量回馈效率受到电动机转速、制动转矩、电池组荷电状态等因素的影响。利用电动汽车动力总成性能测试试验台,测试分析电动机转速、制动转矩、电池组荷电状态及电池组温度对能量回馈效率的影响规律;讨论电动机温度对能量回馈时最大制动转矩的限制;参考实车测试数据,设定能量回馈效率特性研究工况范围,对不同电动机转速、制动转矩及电池组荷电状态下的能量回馈效率进行测试;基于实测数据构建能量回馈效率预测模型,并通过台架试验验证该模型的有效性。参考能量回馈效率模型开发控制策略,实车滑行能量回馈过程中,回收能量相对于原车控制策略提高了4.8%,这表明该模型可为高效能量回馈控制策略的制定提供参考依据。     

Investigation of vehicle crash modeling techniques: theory and application

Creating a mathematical model of a vehicle crash is a task which involves considerations and analysis of different areas which need to be addressed because of the mathematical complexity of a crash event representation. Therefore, to simplify the analysis and enhance the modeling process, in this work, a brief overview of different vehicle crash modeling methodologies is proposed. The acceleration of a colliding vehicle is measured in its center of gravity—this crash pulse contains detailed information about vehicle behavior throughout a collision. A virtual model of a collision scenario is established in order to provide an additional data set further used to evaluate a suggested approach. Three different approaches are discussed here: lumped parameter modeling of viscoelastic systems, data-based approach taking advantage of neural networks and autoregressive models and wavelet-based method of signal reconstruction. The comparative analysis between each method’s outcomes is performed and reliability of the proposed methodologies and tools is evaluated.