Locomotive dynamic performance under traction/braking conditions considering effect of gear transmissions

Traction or braking operations are usually applied to trains or locomotives for acceleration, speed adjustment, and stopping. During these operations, gear transmission equipment plays a very significant role in the delivery of traction or electrical braking power. Failures of the gear transmissions are likely to cause power loses and even threaten the operation safety of the train. Its dynamic performance is closely related to the normal operation and service safety of the entire train, especially under some emergency braking conditions. In this paper, a locomotive–track coupled vertical–longitudinal dynamics model is employed with considering the dynamic action from the gear transmissions. This dynamics model enables the detailed analysis and more practical simulation on the characteristics of power transmission path, namely motor–gear transmission–wheelset–longitudinal motion of locomotive, especially for traction or braking conditions. Multi-excitation sources, such as time-varying mesh stiffness and nonlinear wheel–rail contact excitations, are considered in this study. This dynamics model is then validated by comparing the simulated results with the experimental test results under braking conditions. The calculated results indicate that involvement of gear transmission could reveal the load reduction of the wheelset due to transmitted forces. Vibrations of the wheelset and the motor are dominated by variation of the gear dynamic mesh forces in the low speed range and by rail geometric irregularity in the higher speed range. Rail vertical geometric irregularity could also cause wheelset longitudinal vibrations, and do modulations to the gear dynamic mesh forces. Besides, the hauling weight has little effect on the locomotive vibrations and the dynamic mesh forces of the gear transmissions for both traction and braking conditions under the same running speed.     

Effect of vehicle vibration environment of high-speed train on dynamic performance of axle box bearing

In this study, we developed a comprehensive three-dimensional vehicle–track coupled dynamics model considering the traction drive system and axle box bearing. In this model, dynamic interactions between the axle box bearing and other components, such as the wheelset and bogie frame, are considered based on a detailed analysis of the structural properties and working mechanism of the axle box bearing. A few complicated dynamic excitations, such as the time-varying mesh stiffness of gears, time-varying stiffness of bearing, bearing gaps and track irregularities, are considered. Then, the dynamic responses of the vehicle–track system are demonstrated via numerical simulations based on the established dynamics model. The results indicate that the traction drive system and track irregularities can significantly influence the dynamic interactions of the axle box bearing. The necessity of considering the excitation caused by gear meshing and track irregularities when assessing the dynamic performance of the axle box bearing is demonstrated.     

Dynamics Analysis of Torsional Vibration Induced by Clutch and Gear Set in Automatic Transmission

The torsional vibration generated during clutch engagement directly affects the shifting quality of automatic transmissions, where the noise source stems from both the clutch and the gear set. To predict the dynamical response and driveline oscillation, a comprehensive mathematical model of the vehicle powertrain equipped with automatic transmission is developed with consideration of nonlinearities in the clutch and the planetary gear set. For the clutch, the dynamics of stickslip is described for the transition between the slipping to locked states. The gear backlash model is used to analyze the rattle noise of the planetary gear set. Based on extensive powertrain simulations for the clutch engagement process, the magnitude of vibration propagation in the driveline are predicted to identify the primary factors of noise generation.     

MASTA的微型车变速哭齿轮啮合

齿轮作为手动变速器的主要传动部件,其啮合情况对整个变速器的性能好坏有着至关重要的影响。文章采用MASTA软件实现了对某微型车变速器的齿轮啮合分析,并建立了变速器的仿真模型,模拟其实际负载状况完成变速器的齿轮传动过程分析;同时利用软件的齿轮微观修形模块,优化齿面啮合的接触斑点,减小传递误差,达到了改善齿面接触状况的目的。表明运用专业软件进行建模与仿真分析,可有效减少试验费用,缩短研发周期,为今后新变速器齿轮的开发与应用提供了较好的指导作用。     

准双曲面齿轮齿面主动设计与先进制造技术

准双曲面齿轮的具面形状对其传动性能起着决定性的作用。现行齿轮设计技术只能在有限的几种模式中被动地选择齿面形式，这限制了齿轮传动性能的进一步提高。齿面主动设计直接以齿面在其全啮合过程中的主要啮合性能参数作为设计变量来确定齿面的形状参数，齿面形式不受传统的摇台结构机床的限制。研究表明，只需用三轴联动CNC铣齿机就能加工出主动设计得到的啮合性能良好的准双曲面齿轮。本文介绍了确定CNC机床参数的原理，提供了直接面向CNC铣齿机的有关的切齿加工计算公式，并给出了计算示例。     

一种基于预测的电控汽油机怠速稳定性控制方法

根据发动机怠速工作过程的非线性、时变性和不确定性，分析了传统怠速稳定性控制的控制机理及存在的不足，提出了一种基于预测的发动机怠速稳定性控制方法——动态矩阵预测控制(DMC)算法，并建立了预测控制模型。试验表明，该预测控制方法能够较好地克服各种不确定性因素和复杂变化对怠速稳定性的影响。     

行星齿轮传动系中啮合相位关系

以前对行星齿轮传动机构的分析主要集中在各种制造和装配误差对齿轮系的影响，很少考虑相位差的影响因素。文中通过行星齿轮系简化模型，结合行星齿轮传动系的结构特点，详细说明了行星齿轮中啮合相位差的关系特性，建立了能适应于行星齿轮系分析模型的参数描述，并分析了直齿轮和斜齿轮的行星齿轮传动系相位关系及啮合刚度影响系数的异同。     

准双曲面齿轮有摩擦承载接触分析

本文推导了准双曲面齿轮有摩擦承载接触问题的数学规划解法，首先采用有限元方法计算工作齿面网格结点的柔度张量，并通过插值和叠加获得一对啮合齿在各接触位置上接触椭圆长轴离散点的综合柔度，然后结合齿面几何因素（包括齿面间隙，滑动系数，法矢和切矢对于转轴的矢径等）建立了接触问题的线性规划模型，采用载荷增量法求解了摩擦的接触变形过程，本文还以一对准双曲面齿轮为例，进行了整个啮合过程的承载接触分析。     

Vibrational characteristics of automotive transmission

A mathematical model of an automotive transmission is developed, that considers the flexibility of the shafts, bearings, and gear teeth, and gyroscopic effects of geared rotors. The transverse, torsional, and axial motions are strongly coupled due to helical gearing. The excitation forces acting on the automotive transmission are classified into first, second, and third grades, based on the magnitudes of the forces that are determined by the perturbation method. The excitation forces are caused by the mass imbalances among gears, misalignment of shafts, clearance and non-linear deformation of bearings, transmission errors, and the periodic variation of the gear mesh stiffness. A bench test on loading conditions is carried out for the third speed of the automotive transmission. The experimental results of vibration characteristics are compared with those from theoretical analysis. The results show good agreement, i.e., within a tolerance of 3.3%.     

乘用车手动变速箱动态换挡性能测试与分析

本文通过对乘用车手动变速箱的动态换档性能试验研究,制定了测试方法、测试工况以及数据分析。本文着重对快速换档、慢速换档和怠速时的换档特性进行了阐述,并通过具体数据举例,对动态换档性能提出了性能要求,对设计改进有一定的指导意义。     

Prediction of vibrating forces on meshing gears for a gear rattle using a new multi-body dynamic model

An efficient multibody dynamic model was developed to predict the vibrating transmitted gear forces of loaded and unloaded pairs of helical gears simultaneously at all speeds. The model can also calculate the bearing forces of a manual transmission that, in turn, may be converted to rattling noises. The bending of meshing gear teeth and torsional flexibility of transmission shafts were considered and embodied effectively in the multibody dynamic model by calculating the tooth bending stiffness and adding a torsion spring on a shaft section between two gears, respectively. The reactive forces on teeth and bearings were calculated and compared using three different models that were developed for this study — an equivalent model, a rigid-body model, and a frequency-based model. The equivalent model took only 58% computation time, compared to the frequency-based method, even though the two showed very similar results.     

汽车齿轮修形的研究

由于汽车齿轮存在制造和安装误差，以及轮齿的弹性变形、扭转变形、热变表等因素，使齿轮在啮合过程中产生冲击、振动和偏载。通过研究与分析指出，汽车齿轮的修形可以改善汽车齿轮的传动。探讨了齿轮修形量的确定方法。     

Nonlinear tire-road friction control based on tire model parameter identification

A hierarchical control structure is a more suitable structural scheme for integrated chassis control. Generally, this type of structure has two main functions. The upper layer manages global control and force allocation, while the bottom layer allocates realized forces with 4 independent local tire controllers. The way to properly allocate these target forces poses a difficult task for the bottom layer. There are two key problems that require attention: obtaining the nonlinear time-varying coefficient of friction between the tire and different road surfaces and accurately tracking the desired forces from the upper layer. This paper mainly focuses on longitudinal tire-road friction allocation and control strategies that are based on the antilock braking system (ABS). Although it is difficult to precisely measure longitudinal tire-road friction forces for frequently changing road surface conditions, they can be estimated with a real-time measurement of brake force and angular acceleration at the wheels. The Magic Formula model is proposed as the reference model, and its key parameters are identified online using a constrained hybrid genetic algorithm to describe the evolution of tire-road friction with respect to the wheel slip. The desired wheel slip, with respect to the reference tire-road friction force from the top layer, is estimated with the inverse quadratic interpolation method. The tire-road friction controller of the extended anti-lock braking system (Ext-ABS) is designed through use of the nonlinear sliding mode control method. Simulation results indicate that acceptable modifications to changes in road surface conditions and adequate stability can be expected from the proposed control strategy.     

A locomotive–track coupled vertical dynamics model with gear transmissions

A gear transmission system is a key element in a locomotive for the transmission of traction or braking forces between the motor and the wheel–rail interface. Its dynamic performance has a direct effect on the operational reliability of the locomotive and its components. This paper proposes a comprehensive locomotive–track coupled vertical dynamics model, in which the locomotive is driven by axle-hung motors. In this coupled dynamics model, the dynamic interactions between the gear transmission system and the other components, e.g. motor and wheelset, are considered based on the detailed analysis of its structural properties and working mechanism. Thus, the mechanical transmission system for power delivery from the motor to the wheelset via gear transmission is coupled with a traditional locomotive–track dynamics system via the wheel–rail contact interface and the gear mesh interface. This developed dynamics model enables investigations of the dynamic performance of the entire dynamics system under the excitations from the wheel–rail contact interface and/or the gear mesh interface. Dynamic interactions are demonstrated by numerical simulations using this dynamics model. The results indicate that both of the excitations from the wheel–rail contact interface and the gear mesh interface have a significant effect on the dynamic responses of the components in this coupled dynamics system.     

变速比变厚齿扇齿面滑移及接触应力特性的理论分析

本文以齿条齿面共轭线方程及变速比变厚齿扇齿面数学模型为基础，提出了汽车循环球式转向器变速比变厚齿扇齿面滑移及齿面接触应力特性的离散数值计算方法；提示了速比变化比值对齿面滑移及齿面接触应力特性的影响。     

Modelling polymer draft gears

This paper developed a new and simple approach to model polymer draft gears. Two types of polymer draft gears were modelled and compared with experimental data. Impact characteristics, in-train characteristics and frequency responses of these polymer draft gears were studied and compared with those of a friction draft gear. The impact simulations show that polymer draft gears can withstand higher impact speeds than the friction draft gear. Longitudinal train dynamics simulations show that polymer draft gears have significantly longer deflections than friction draft gears in normal train operations. The maximum draft gear working velocities are lower than 0.2?m/s, which are significantly lower than the impact velocities during shunting operations. Draft gears’ in-train characteristics are similar to their static characteristics but are very different from their impact characteristics; this conclusion has also been reached from frequency response simulations. An analysis of gangway bridge plate failures was also conducted and it was found that they were caused by coupler angling behaviour and long draft gear deflections.     

变速比转向器齿轮副的机理分析

本文运用啮合原理分析方法给出了变速比转向器齿条齿扇传动的啮合线方程、齿扇的齿廓方程,导出了锥形齿扇被切削时小端不根切、大端不尖的变位系数和齿扇几何尺寸计算公式。     

准双曲面齿轮传动的轮齿接触分析

本文推导了准双曲面齿轮传动的轮齿接触分析方法，包括齿面接触分析和边缘接触分析，代表了齿轮啮合的完整过程。该方法便于在计算机上实现，通过计算机数值仿真，可准确地显示不同参数，不同误差的齿轮啮合过程和性能，能有效地降低产品成本，提高产品质量。     

基于CATIA的斜齿圆柱齿轮参数化设计

为了减少在圆柱齿轮计算机辅助设计过程中,参数化设计、有限元分析和运动仿真的跨平台数据传递,基于CATIAV5以参数绘制齿廓渐开线,通过多截面曲面绘制出齿型曲面并运用曲面缝合功能实现齿型闭合,实现斜齿轮的精确建模。利用CAE和运动仿真模块并结合斜齿轮传动原理和齿面受力,对斜齿轮齿进行有限元分析和啮合状态运动仿真,检验设计结果符合要求,从而为设计和精密制造以及工程失效分析提供精确的数据参考。     

齿面微观修形在汽车变速器降噪中的应用研究

针对汽车变速器啸叫噪声,借助软件RomaxDesigner对齿轮啮合情况进行分析,建立了齿轮静传递误差模型;结合接触斑点试验并采用多因素实验设计得出最佳的齿面微观修形参数.据此进行了齿面微观修形,并对修形前后峰值传递误差和驾驶员位置的声压水平进行对比,结果表明经过合理的齿面修形,静传递误差减小了,齿轮发出的啸叫噪声降低约10dB.