引入悬架K&C特性参数的汽车操纵稳定性数学模型

基于经典操纵稳定性二自由度线性数学模型研究方法,通过力学分析建立了包含悬架K&C特性参数的汽车操纵稳定性线性数学模型,并建立其MATLAB模型。将经典操纵稳定性二自由度数学模型和引入悬架K&C特性参数的操纵稳定性数学模型对整车不足转向度及横摆角速度的影响进行对比分析,研究悬架K&C特性参数与操纵稳定性的关系。依据三种小型SUV的悬架K&C数据及整车阶跃试验数据,对两种操纵稳定性数学模型进行计算,并与试验结果进行了对比,验证了引入悬架K&C特性参数的操纵稳定性数学模型的准确性。     

影响铰接式自卸车操纵稳定性的结构参数分析

铰接式自卸车的工作环境恶劣但载重量较大,对其操纵稳定性具有较高的要求,整车中对此性能的影响因素较多,对影响铰接式自卸车操纵稳定性的结构参数进行分析具有重要意义。稳定性与动态特性是准确描述车辆运行过程中操纵性能的重要特性,根据铰接式自卸车结构特点,为建立准确的整车多自由度操纵动力学模型,用多体系统动力学原理,对整车进行分析并建模。基于多体动力学模型,车辆运行在满载和空载状态时,系统采用角阶跃输入,对各状态参量的瞬态与稳态响应进行分析;分析重要结构参数变化时,对各状态参量的响应情况进行分析,得结构参数对车辆操纵稳定性的不同影响。前轮胎侧偏刚度越小,而后轮的侧偏刚度在一定范围内增大时,整车的操纵稳定性越好,且能够很好的减小车辆转向稳态时的簧载质量侧倾角;车辆悬架刚度对整车状态参量影响较小;轴距越靠前、铰接点越靠前布置越有利于提高操纵稳定性。研究方法和结果为此类车辆设计提供参考。     

分布式驱动电动汽车操纵稳定性影响因素分析研究

为了探究影响分布式驱动电动汽车操纵稳定性的因素,以某车型为研究对象,对各影响因素进行仿真分析。基于Carsim软件和Simulink软件分别建立了整车动力学模型和电机模型,通过改变汽车的行驶速度、质心高度、质心前后位置以及路面附着系数,对整车操纵稳定性进行仿真分析,分别获得了不同行驶速度、不同质心位置和不同路面附着系数下的汽车横摆角速度瞬态响应曲线和汽车质心侧偏角瞬态响应曲线。研究结果表明,行驶速度、质心位置和路面附着系数均对汽车操纵稳定性有不同程度的影响,通过对分布式驱动电动汽车操纵稳定性的仿真分析,能够有效地反应出影响汽车操纵稳定性的因素,为今后汽车结构参数设计提供一定的理论依据。     

车辆操纵稳定性评价方法及其在车辆基本结构参数设计中的应用

介绍了车辆操纵稳定性的客观评价方法,讨论了显著影响汽车操纵稳定性的结构参数。这些基本参数包括整车质量、质心位置、前后轮侧偏刚度、后轴侧倾转向系数以及转向系刚度和传动比等。同时介绍了通过仿真分析,在ADAMS等多体仿真环境下根据汽车稳定性来优化基本结构参数,从而提高汽车的操纵稳定性。     

结构参数变化对三轴车辆操纵稳定性的影响分析

多轴车辆由于轴数多、车身长、载重量大,其转弯半径大,高速转向时容易甩尾,稳定性差,为提高多轴车辆低速时的机动灵活性和中高速的稳定性,三轴车辆为研究对象,建立了二自由度操纵稳定性模型,对由于车辆结构变化引起的质心、转动惯量等参数进行了重新计算,分析了轴距、侧偏刚度等结构参数的变化对车辆操纵稳定性的影响。根据分析结果对车辆的改装提出了合理的设计建议。另外还分析了二轴车辆改装成三轴车辆后,后轴距的变化对车辆性能的影响。     

全地形车前悬架系统对操纵稳定性的影响研究

全地形车是指适合各种地形的交通工具,具有良好的机动性,操纵稳定性是全地形车重要性能之一,而悬架的定位参数对全地形车的操纵稳定性具有较大的影响。以全地形车前悬架系统为研究对象,在ADAMS/Car中建立了其参数化模型,通过仿真得出全地形车前悬架参数随车轮上下跳动的变化曲线。分析了前轮定位参数(包括前轮外倾角、前轮前束角、主销内倾角、主销后倾角)对操纵稳定性的影响,找出优化目标,调整悬架硬点参数,进行参数优化设计,最终得到满足悬架和整车设计要求的悬架系统。研究结果表明,采用该方法研究悬架系统对操控稳定性的影响是可行的。     

基于响应面法的整车操纵稳定性多目标优化

针对某轿车操纵稳定性较差的问题,利用ADAMS/Car据实车参数建立整车多体动力学模型,并利用相同工况下模型仿真与实车试验结果进行对比验证,确定模型的精确性.在此基础上对多个参数进行操纵稳定性对比分析,经分析发现前轮定位参数和悬架弹簧刚度等参数对汽车的操纵稳定性影响较大,以此为设计变量,采用响应面法结合统一目标法对汽车的操纵稳定性进行多目标优化,以此来提高该轿车的操纵稳定性.结果 表明,该方法对汽车的操纵稳定性优化效果显著.     

基于虚拟样机技术的汽车悬架转向系的研究

研究了汽车前悬架的定位参数,通过ADAMS/CAR建立悬架转向系的虚拟样机模型,进行了双轮同向激振仿真试验分析,得到各响应曲线,分析了结构参数对悬架系统操纵稳定性及转向特性的影响,为汽车悬架转向系的结构设计提供依据.     

基于ADAMS/Car的双叉臂独立悬架优化设计

利用ADAMS建立了某国产跑车的双叉臂独立悬架的虚拟样机模型.在ADAMS/CAR中针对该跑车悬架系统进行仿真,研究悬架参数对操纵稳定性的影响并分析在路试过程中出现的操纵稳定性较差、轮胎磨损严重等问题的原因.通过优化分析提出了悬架参数的改进意见.     

液压动力转向车辆的蛇行试验与仿真

汽车的操纵稳定性决定了汽车的操控性、行驶安全性和抗外界干扰能力,而转向系统与汽车操纵稳定性关系最为密切。为研究液压动力转向车辆的操纵稳定性,利用Matlab/Simulink建立了液压动力转向系统以及整车三自由度状态方程的仿真模型,在使用试验数据验证仿真模型正确性的基础上,对模型进行了蛇行试验的操纵稳定性仿真,分析了液压动力转向系统的系统结构参数对蛇行试验的影响,仿真结果的分析为动力转向系统的设计和提高车辆操纵稳定性提供了依据。     

半挂汽车列车操纵稳定性仿真研究

通过建立半挂汽车列车的动力学模型,对其进行拉氏变换,求出系统的传递函数;改变半挂汽车列车的使用和结构参数,利用MATLAB编程进行数字仿真,通过系统的传递函数求出其根轨迹;再根据根轨迹变化趋势,判断系统是否稳定及稳定裕度的大小;结果表明:车速、轮胎侧偏刚度、牵引车与挂车的质量、挂车质心到铰接点的距离、牵引车质心到铰接点的距离等参数,对半挂汽车列车操纵稳定性的影响程度不同,选择合理的参数可以提高半挂汽车列车的操纵稳定性。     

A new and simple method to construct root locus of general fractional-order systems

Recently fractional-order (FO) differential equations are widely used in the areas of modeling and control. They are multivalued in nature hence their stability is defined using Riemann surfaces. The stability analysis of FO linear systems using the technique of Root Locus is the main focus of this paper. Procedure to plot root locus of FO systems in s-plane has been proposed by many authors, which are complicated, and analysis using these methods is also difficult and incomplete. In this paper, we have proposed a simple method of plotting root locus of FO systems. In the proposed method, the FO system is transformed into its integer-order counterpart and then root locus of this transformed system is plotted. It is shown with the help of examples that the root locus of this transformed system (which is obviously very easy to plot) has exactly the same shape and structure as the root locus of the original FO system. So stability of the FO system can be directly deduced and analyzed from the root locus of the transformed IO system. This proposed procedure of developing and analyzing the root locus of FO systems is much easier and straightforward than the existing methods suggested in the literature. This root locus plot is used to comment about the stability of FO system. It also gives the range for the amplifier gain k required to maintain this stability. The reliability of the method is verified with analytical calculations.     

Carbody hunting investigation of a high speed passenger car

This paper describes the low frequency carbody hunting problem of a high speed passenger car emerged in the process of tests and service operations. It causes a significant deterioration of lateral comfort. First, the vehicle model is established as a multiple rigid body system. Using root locus analysis, the effect of system parameters on the carbody hunting stability has been studied. It shows that carbody hunting instability has something to do with suspension parameters and wheel/rail conditions. To find the causes of this carbody hunting problem, component tests have been carried out. Based on the theoretical hunting stability analysis and component tests, solutions are proposed and then validated in the field test.     

Hurwitz stability analysis of fractional order LTI systems according to principal characteristic equations

With power mapping (conformal mapping), stability analyses of fractional order linear time invariant (LTI) systems are carried out by consideration of the root locus of expanded degree integer order polynomials in the principal Riemann sheet. However, it is essential to show the left half plane (LHP) stability analysis of fractional order characteristic polynomials in the s plane in order to close the gap emerging in stability analyses of fractional order and integer order systems. In this study, after briefly discussing the relation between the characteristic root orientations and the system stability, the author presents a methodology to establish principal characteristic polynomials to perform the LHP stability analysis of fractional order systems. The principal characteristic polynomials are formed by factorizing principal characteristic roots. Then, the LHP stability analysis of fractional order systems can be carried out by using the root equivalency of fractional order principal characteristic polynomials. Illustrative examples are presented to explain how to find equivalent roots of fractional order principal characteristic polynomials in order to carry out the LHP stability analyses of fractional order nominal and interval systems.     

A new design method for PI–PD control of unstable processes with dead time

PID controllers are still widely practiced in the industrial systems. In the literature, many publications can be found considering PID controller design for unstable processes. However, owing to the structural limitations of PID controllers, generally, good closed loop performance cannot be achieved with a PID for controlling unstable processes and usually a step response with a high overshoot and oscillation is obtained. On the other hand, PI–PD controllers are proved to give very satisfactory closed loop performances for unstable processes. The paper presents a simple design method to tune parameters of a PI–PD controller for the control of the unstable processes with time delay. The proposed method is based on plotting the stability boundary locus, which is a locus dependent on the parameters of the controller and frequency, in the parameter plane. The method uses a new concept named centroid of the convex stability region. Simulation examples and an experimental application are given to illustrate the superiority of the proposed method over some existing ones.     

汽车侧翻及稳定性分析

通过对三自由度线性汽车侧翻模型的理论分析,得到了汽车侧翻系统准动态稳定因子。与静态稳定因子进行了比较,并应用劳斯-赫尔维茨稳定性判据得到了汽车侧翻系统的稳定性条件。通过数值仿真分析得到了汽车结构参数对侧翻稳定区域的影响,并通过固定转角及变车道行驶两个实例仿真来验证,得到结果与理论分析一致。     

起重机伸缩臂最优截面形式的研究

利用ANSYS有限元分析软件的APDL语言进行二次开发,完成臂架参数化建模,分析不同截面参数的变化对臂架刚度、强度及稳定性的影响程度,确定了影响臂架结构整体性能的主要因素和相对次要因素,并对其截面尺寸进行优化．分别以臂架的刚度、强度及稳定性作为性能指标,对伸缩臂结构模型进行性能参数优化,得出不同条件下的最优截面形式．     

磁电轴承中抑制不平衡振动的陷波滤波器设计方法

为解决陷波滤波器在实际应用中存在影响控制系统稳定性的问题和兼顾系统的干扰抑制和稳定特性,提出了一种陷波滤波器的设计方法。该陷波滤波器采用通用式结构,其中心频率分布在转子转速附近以抑制不平衡振动。陷波滤波器中的其他三个参数,与滤波器的带宽和极点分布相关,可影响系统的稳定性。推导出包含该陷波滤波器的系统传递函数和稳定方程,综合采用根轨迹、频域分析的方法,给出了这三个参数与系统稳定性的关系。然后考虑稳定裕量、刚度、振荡幅度和滤波效果的要求以设计陷波滤波器。试验结果表明,采用该设计方法的陷波滤波器,不仅使磁电轴承的转速衰减率和控制电压噪声分别减小91％和67％,而且也使系统的稳定性指标和附加振荡幅度满足设计指标。     

基础摆动条件下主动电磁轴承-柔性转子系统的稳定性

与基础平动不同,基础摆动不仅会给转子系统产生额外的激励力,而且还会改变转子系统的阻尼及刚度特性,对系统的稳定性产生影响。以电磁轴承支承的柔性转子系统为例,研究了基础摆动条件下转子系统的稳定性。首先,用有限元法建立了基础摆动条件下电磁轴承–柔性转子系统的动力学模型,然后基于Routh-Hurwitz准则推导了基础恒定摆动条件下转子系统的稳定性条件,并用特征根轨迹进行分析。之后,基于Floquet理论研究了基础正弦摆动对电磁轴承柔性转子系统稳定性的影响,得到了系统的稳定性边界,并利用转子系统响应进行了验证。最后,研究了PID控制器参数对基础摆动条件下电磁轴承–柔性转子系统稳定性的影响,针对基础正弦摆动,提出了使用相位补偿器补偿转子系统稳定性的方法。研究结果表明,基础恒定摆动条件下,主动柔性转子系统的稳定性与摆动的幅值有关;基础正弦摆动条件下,转子系统的稳定性与摆动的幅值和频率有关。合理地选择PID控制器的参数能够改善转子系统的稳定性。PID控制器串联相位补偿器,对于基础正弦摆动条件下电磁轴承–柔性转子系统的稳定性具有良好的补偿效果。     

Experimental research on improving accuracy of electrochemical machining of deep narrow grooves

The aim of this study is to increase the dynamic stability of the quadrotor unmanned aerial vehicles in varying structural parameters. The qualitative analysis is considered the main method for analyzing the dynamic stability, while the index of qualitative analysis of the structural stability and the dynamic stability is still hard to establish. Therefore, the process during takeoff, pitching, or yawing is selected for investigating in the present papers, the method of Lyapunov exponent is adopted for establishing the quantification relationship between structural parameters of the quadrotor unmanned aerial vehicles and dynamic stability, which provides for guiding the design of the vehicle’s mechanical structure and the optimization of its stability control by using the relationship. As compared to its counterpart of Lyapunov’s second method, the main advantage of the concept of Lyapunov exponents is that the methods for calculating the exponent process are constructive which makes the stability analysis of complex nonlinear systems possible.