Energy Flow Method for the Study of Motorcycle Wobble Mode

SUMMARY

A concept of the energy flow is introduced in order to study the motorcycle wobble mode. The activation mechanism of the wobble oscillation is made clear in the framework of the energy flow concept It is found that the wobble mode is activated mainly by the yaw rate and roll rate motion and is suppressed by the lateral acceleration and the force of the front time. A designing guide to stabilize the wobble mode is mentioned.     

On the wobble mode of a bicycle

Wheel shimmy and wobble are well-known dynamic phenomena at automobiles, aeroplanes and motorcycles. In particular, wobble at the motorcycle is an (unstable) eigenmode with oscillations of the wheel about the steering axis, and it is no surprise that unstable bicycle wobble is perceived unpleasant or may be dangerous, if not controlled by the rider in time. Basic research on wobble at motorcycles within the last decades has revealed a better understanding of the sudden onset of wobble, and the complex relations between parameters affecting wobble have been identified. These fundamental findings have been transferred to bicycles. As mass distribution and inertial properties, rider influence and lateral compliances of tyre and frame differ at bicycle and motorcycle, models to represent wobble at motorcycles have to prove themselves, when applied to bicycles. For that purpose numerical results are compared with measurements from test runs, and parametric influences on the stability of the wobble mode at bicycles have been evolved. All numerical analysis and measurements are based on a specific test bicycle equipped with steering angle sensor, wheel-speed sensor, global positioning system (GPS) 3-axis accelerometer, and 3-axis angular velocity gyroscopic sensor.     

The Effect of Topboxes on Motorcycle Stability

Hot wire anenometry measurements have been made in the wake of a model motorcycle and rider mounted in a windtunnel. Only in tests with a topbox present is there clear evidence of eddy shedding. Calculations have been performed on the corresponding full-scale motorcycle to determine the frequencies of the weave and wobble modes. Comparison with the wake frequencies extrapolated to full size show that at speeds of 31-34 m/s they coincide with those of the wobble mode which is found to be efficiently coupled to the aerodynamic excitation.     

A nonlinear model of bicycle shimmy

This paper presents a nonlinear model accurately describing, both qualitatively and quantitatively, the onset and dynamics of bicycle shimmy. Methods of nonlinear dynamics, such as numerical continuation and bifurcation analysis, show that the model exhibits two stable periodic motions found experimentally in on-road tests: the weave and wobble (or shimmy) mode. The modelling results are compared with experimental data collected by riding a racing bicycle downhill at high speeds with hands on the handlebar. The model predicts with surprising accuracy the amplitudes and frequencies of the oscillations, the longitudinal velocity at which they occur, as well as the substantial independence of wobble frequency and amplitude from the forward speed. The lateral acceleration of the upper tube of the frame near the steering axis reaches 5–10?g, both in the model and in the data. The analysis shows that wobble onset and amplitude is particularly sensitive to changes in the torsional stiffness of the frame and strongly depends on tyre lateral force and aligning torque at the wheel–road contact point. It also allows to quantify the additional viscous rotary damping that should be added to the steering assembly to prevent wobble.     

The influence of frame compliance and rider mobility on the scooter stability

This article investigates the effect of frame compliance and rider mobility on the scooter stability. Particular attention is given to the wobble mode, because it may easily become unstable in the vehicle speed range. This article includes a synthetic discussion of previous works, presents a new mathematical model, and discusses the results of both numerical and experimental analyses of the vehicle stability by varying the vehicle characteristics and motion conditions.

The mathematical model describes the out-of-plane dynamics of the scooter and consists of a twelve-degree-freedom linear model. It describes the main scooter features and, in particular, includes the frame compliance, rider mobility, and an advanced tire model. The torsion and bending compliance of both the front fork and swingarm are modelled using lumped rotational springs; similarly, the rider mobility is described by means of two soft springs which connect the rider body to the chassis. The tire model describes in detail the carcass geometry and its compliance. The full scooter model is available on the website www.dinamoto.it and has been derived using ‘MBSymba’, which is a package for the symbolic modelling of multibody systems.

The scooter stability has been investigated at both low and high speeds; in particular, the effect of vehicle compliance and rider mobility on the weave and wobble modes have been examined. Numerical simulations show that the bending flexibility of the front fork stabilizes wobble mode at high speed and has a contrary effect at low speed, whereas the torsion flexibility of the fork does not appear to have a remarkable influence; the bending flexibility of the swingarm slightly stabilizes the weave mode at very high speeds whereas the torsion flexibility of the swingarm has a contrary effect. The effect of rider mobility is to stabilize the weave mode at high speed and the wobble mode at low speed. Several experimental tests have been carried out in the same speed range and a good correlation between simulations and tests has been found. The variation of some important vehicle parameters has been investigated; in particular, tests were repeated for different values of the rear-frame inertia, the rear-chassis stiffness, the front-tire characteristics, the normal trail, and the steer inertia.     

Experimental study of performance and emission characteristics of DEE-assisted minimally processed ethanol fuelled HCCI engine

The homogeneous charge compression ignition (HCCI) is an alternative combustion concept for reciprocating engines. This study investigates an HCCI engine fuelled with Diethyl ether (DEE) ignition assisted wet ethanol (ethanol with 20% water content). The direct use of wet ethanol could reduce the associated energy required for distillation and dehydration of ethanol. The HCCI engine offers significant benefits in terms of its high efficiency and ultra low emissions. The experiment is conducted with various DEE flow rates and at different air-fuel ratios, for which stable HCCI combustion is achieved. Incylinder pressure, heat release analysis and exhaust emissions were observed. In this study, the effect of DEE on combustion parameters, thermal efficiency and emissions is analysed and discussed in detail. The experimental results indicate that the DEE flow rates have a significant effect on the maximum in-cylinder pressure and its position, thermal efficiency, maximum rate of pressure rise and the heat release rate. Results show that for all stable operating points, brake thermal efficiency is higher than reference mode at lower loads and almost same at higher loads. The emission parameters such as NO, HC and CO are lower than the dual fuel mode which is considered as a reference model for this experiment.     

Dynamic modelling and experimental validation of three wheeled tilting vehicles

The present paper describes the study of the stability in the straight running of a three-wheeled tilting vehicle for urban and sub-urban mobility. The analysis was carried out by developing a multibody model in the Matlab/SimulinkSimMechanics environment. An Adams-Motorcycle model and an equivalent analytical model were developed for the cross-validation and for highlighting the similarities with the lateral dynamics of motorcycles. Field tests were carried out to validate the model and identify some critical parameters, such as the damping on the steering system. The stability analysis demonstrates that the lateral dynamic motions are characterised by vibration modes that are similar to that of a motorcycle. Additionally, it shows that the wobble mode is significantly affected by the castor trail, whereas it is only slightly affected by the dynamics of the front suspension. For the present case study, the frame compliance also has no influence on the weave and wobble.     

Active controller design for an electromagnetic energy-regenerative suspension

In this paper, with the parameters acquired from measured and tested data, a three-phase mathematical model is applied to the motor component of the developed electromagnetic suspension actuator. A main/inner-loop structure is used for its active control, and the constraints of the control current and energy flow states of actuator are analyzed by simplifying the inner-loop control system. Two different control modes, i.e., Consumptive Full Active (CFA) and Regenerative Semi Active (RSA) modes, which emphasize vibration control of sprung mass and vibration energy regeneration caused by road roughness, respectively, are proposed. Simulations are carried out using different road conditions, and the results demonstrate that the CFA mode can improve vehicle ride comfort by more than 30 percent, despite battery energy consumption; in RSA mode, the ride comfort can be improved by up to 10 percent with the battery charged by regenerated energy.     

汽车发动机怠速抖动机理研究

汽车发动机怠速抖动是实际运用中的一个难题。讨论了发动机机体正常振动时的激振源和振动形式,并运用机械振动理论,研究了怠速抖动时它们的变化。指出,由于发动机的各种故障会引起个别气缸气体作用力减小,导致总的反倒力矩平衡性恶化,致使发动机横向摆动加大,出现怠速抖动。对发动机进行了振动试验,验证了结论。为解决发动机怠速抖动问题及改进设计提供了理论指导。     

家庭分布式储能的发展前景

电动汽车的大规模推广应用,将对现有储能方式产生重大的影响和挑战,本文结合对国内外电动汽车动力电池选型、现有大规模储能模式及其特点的分析,提出了家庭分布式储能的概念及其应用前景。     

某车型后背门开裂问题分析及解决

由于某车型后背门受力较大且比较集中,其后背门铰链安装点处钣金在前期道路试验中,多次出现疲劳开裂问题.为解决此问题,通过CAE分析,对耐久强度薄弱点直接进行加强,并对后背门限位方式进行优化,有效地提高了安装点强度,并减小行车中后背门摆动,成功地消除了该位置的疲劳开裂.     

均匀风量集中排烟隧道火灾烟气流动分析与足尺试验

隧道火灾集中排烟系统集纵向和横向排烟模式的优势,应用愈加广泛。然而在排烟过程中,大量烟气易从离风机较近的排烟阀排出,极大降低了排烟效率并浪费了能源,为解决此类问题提出均匀风量集中排烟模式的概念,通过调节排烟阀开启角度,使各排烟阀排烟量均匀一致,最大限度的将高温烟气由火源附近的排烟阀排出。基于质量、动量和能量守恒方程,以排烟道内烟流为控制体,建立均匀排烟模式下关于排烟阀流速、排烟量、排烟阀开启角度和排烟风机风压关系的理论预测模型并求出解析解;同时,以港珠澳大桥海底沉管隧道为原型,建立世界最大断面尺寸沉管试验隧道,开展足尺验证试验。研究结果表明：均匀风量排烟系统能够通过控制排烟阀开启角度平衡各排烟阀排烟量实现高效排烟的目的;提出火灾时应开启火源最近处排烟阀且在满足烟气流速限值的情况下,控制排烟阀开启数量,既能缩短烟气蔓延范围又能实现有效节能;均匀排烟模式下,各排烟阀排烟量均匀一致,排烟阀开启角度呈逐渐增大趋势,离火源越近排烟阀开启角度越小。最后,以10 MW火灾为例,通过足尺试验验证均匀风量集中排烟烟气运动理论模型的正确性。     

Experimental and numerical analysis of the influence of tyres’ properties on the straight running stability of a sport-touring motorcycle

The behaviour of a motorcycle on the road is largely governed by tyre properties. This paper presents experimental and numerical analyses dealing with the influence of tyre properties on the stability of weave and wobble in straight running. The final goal is to find optimal sets of tyre properties that improve the stability of a motorcycle. The investigation is based on road tests carried out on a sport-touring motorcycle equipped with sensors. Three sets of tyres are tested at different speeds in the presence of weave and wobble. The analysis of telemetry data highlights significant differences in the trends of frequency and damping of weave and wobble against speed. The experimental analysis is integrated by a parametric numerical analysis. Tyre properties are varied according to the design of experiments method, in order to highlight the single effects on stability of lateral and cornering coefficient of front and rear tyres.     

Energy recovery based on pedal situation for regenerative braking system of electric vehicle

ABSTRACT

Energy recovery is a key technology to improve energy efficiency and extend driving range of electric vehicle. It is still a challenging issue to maximise energy recovery. We present an energy recovery mode (mode A) which recovers braking energy under all situations that accelerator pedal (AP) is lifted, brake pedal (BP) is depressed, as well as AP and BP are released completely; and propose a control strategy of regenerative braking based on driver's intention identified by a fuzzy recognition method. Other two modes: (1) recovery braking energy only the BP is depressed (mode B), (2) no energy recovery, have been studied to compare with mode A. Simulations are carried out on different adhesion conditions. Recovered energy and driving range are also obtained under FTP75 driving cycle. Road test is implemented to validate simulation results. Results show that mode A can improve energy recovery by almost 15.8% compared with mode B, and extend driving range by almost 8.81% compared with mode B and 20.39% with the mode of no energy recovery; the control strategy of regenerative braking can balance energy recovery and braking stability. The proposed energy recovery mode provides a possibility to achieve a single-pedal design of the electric vehicle.     

平行导坑超前多作业面平行施工通风节能技术研究

隧道多作业面平行施工时,其通风难度一般都比较大。以三都隧道进口工区为依托,分别对射流巷道式通风方案、主扇式通风方案及压入式通风方案从技术、经济2方面进行对比,分析通风方案的经济合理性;从理论上论述通风机的自动控制变频节能原理与节能效果,并经过工程实践及现场通风效果测试,达到了整个通风系统高效节能的目的。     

摆盘发动机及其用于装甲车辆的探讨

介绍了摆盘发动机基本结构及动力学特点,对摆盘发动机与曲柄连杆机构发动机性能进行了对比分析,分析了摆盘发动机用于坦克装甲车辆的益处及应解决的问题。     

On the influence of tyre and structural properties on the stability of bicycles

In recent years the Whipple Carvallo Bicycle Model has been extended to analyse high speed stability of bicycles. Various researchers have developed models taking into account the effects of front frame compliance and tyre properties, nonetheless, a systematic analysis has not been yet carried out. This paper aims at analysing parametrically the influence of front frame compliance and tyre properties on the open loop stability of bicycles. Some indexes based on the eigenvalues of the dynamic system are defined to evaluate quantitatively bicycle stability. The parametric analysis is carried out with a factorial design approach to determine the most influential parameters. A commuting and a racing bicycle are considered and numerical results show different effects of the various parameters on each bicycle. In the commuting bicycle, the tyre properties have greater influence than front frame compliance, and the weave mode has the main effect on stability. Conversely, in the racing bicycle, the front frame compliance parameters have greater influence than tyre properties, and the wobble mode has the main effect on stability.     

插电式混合动力汽车低SOC能量流试验研究

为制定最优的能量分配策略,对某款插电式混合动力汽车在不同运行工况下的能量流进行分析。通过试验测试了低SOC状态下整车部件能量传递的相关参数,包括:温度、压力、转矩、转速和流量等,之后计算和分析整车的能量分布,并对比了NEDC和WLTC工况下整车能量流向和能量回收率。结果表明,在电池处于低SOC时,WLTC工况下的发动机平均油耗是NEDC工况平均油耗的1.6倍左右;且两种工况下车辆行驶所消耗的能量绝大部分来自于发动机;另外,WLTC工况行驶能量低于NEDC工况,其差值不足1%,但WLTC工况的能量回收率低于NEDC工况,其差值达2.31%。     

机动车道路排放的实时测试系统开发及试验研究

在OEM-2100基础上开发了一种机动车道路排放实时测试系统,并在实际道路上进行了轻型车的实时排放测试。计算了路段排放因子和排放总量,分析了车辆各行驶工况所占时间和排放量比例以及平均排放率,研究了各工况下机动车尾气污染物的贡献率,为准确测定交通流中单车污染物提供一种可行的方法。该测试系统为建立排放模型提供数据依据,对于评价交通控制改进措施和智能交通系统对排放的影响具有重要的意义。     

基于能量流分析的纯电动汽车电耗优化研究

能量流分析研究是了解车辆能量利用情况和优化车辆经济性的有效方式,针对于某款纯电动汽车电量消耗偏大的问题,设计了纯电动汽车能量流测试方案,完成了主要部件性能对标测试分析;通过理论分析建立了影响电量消耗的数学模型和基于价值因子的优化参数选取方法;基于CRUISE电耗仿真分析模型,分别从电驱动系统效率提升、滚阻优化、提升制动...