Sensitivity analysis of side-slip angle observer based on a tire model

We investigated the sensitivity of an observer based on a tire model using simulation in linear and nonlinear regions. In the linear region, we investigated the influence of vehicle speed by doing the same simulation at three speed levels. In the nonlinear region, the simulation condition was set such that the vehicle became unstable. In the linear region, steering input and cornering stiffness have a relatively large effect on the estimation error because these quantities determine tire side force. In the nonlinear region, the road surface's friction coefficient becomes a crucial factor. In both the regions, the observer is sensitive to yaw rate and longitudinal speed.     

Analytical dynamic tire model

Modeling of tire friction is one of the central problems for vehicle control systems design. LuGre-type dynamic tire model has been proposed and well discussed in previous studies, because it offers a compact form of dynamic model that is convenient in advanced control studies. It has been successfully used in tire slip control design and vehicle state estimation problems. In this article, a concept of time-constrained Stribeck effect is introduced to interpret the mechanism of the LuGre friction model in predicting tire friction characteristics. A modified two-dimensional (2D) dynamic LuGre friction model is introduced to make it compatible with the governing theorem in the steady state. An analytical 2D modified LuGre-type dynamic tire model is developed, in which some fundamental limitations of classical LuGre models are eliminated. The main modifications involve a change in the structure of the 2D LuGre friction model, introduction of load-dependent parameters in 1D and 2D tire models, and a changed structure in the distributed parameter model. The proposed model is compared, in the steady state, to both the Magic Formula and the classical LuGre model. It improves model accuracy in the steady state and gives a physically reasonable distribution of the bristle deflection. A first-order lumped parameter (LP) nonlinear model, which has simpler structure than the distributed parameter model and the classical LP LuGre model, is then derived. Numerical simulations show that the proposed LP model has a good estimation for tire transient dynamics. Thus, the proposed model retains the merits of LuGre-type models and improves the agreement with observation and experimental data on friction force distribution along the patch and on the steady-state friction prediction.     

Analytical dynamic tire model

Modeling of tire friction is one of the central problems for vehicle control systems design. LuGre-type dynamic tire model has been proposed and well discussed in previous studies, because it offers a compact form of dynamic model that is convenient in advanced control studies. It has been successfully used in tire slip control design and vehicle state estimation problems. In this article, a concept of time-constrained Stribeck effect is introduced to interpret the mechanism of the LuGre friction model in predicting tire friction characteristics. A modified two-dimensional (2D) dynamic LuGre friction model is introduced to make it compatible with the governing theorem in the steady state. An analytical 2D modified LuGre-type dynamic tire model is developed, in which some fundamental limitations of classical LuGre models are eliminated. The main modifications involve a change in the structure of the 2D LuGre friction model, introduction of load-dependent parameters in 1D and 2D tire models, and a changed structure in the distributed parameter model. The proposed model is compared, in the steady state, to both the Magic Formula and the classical LuGre model. It improves model accuracy in the steady state and gives a physically reasonable distribution of the bristle deflection. A first-order lumped parameter (LP) nonlinear model, which has simpler structure than the distributed parameter model and the classical LP LuGre model, is then derived. Numerical simulations show that the proposed LP model has a good estimation for tire transient dynamics. Thus, the proposed model retains the merits of LuGre-type models and improves the agreement with observation and experimental data on friction force distribution along the patch and on the steady-state friction prediction.     

车辆轮胎动力学仿真模型分析

分析了各种常用轮胎模型的特点和利用范围,介绍了ADAMS中轮胎试验台(tiretesting)这一轮胎参数可视化工具,利用这一工具分析比较一种物理轮胎模型与一种经验-半经验轮胎模型间关于侧向力与纵向力、纵向力与纵向滑移率、回正力矩与纵向滑移率的力学特性,针对一种魔术公式轮胎模型验证了侧向力和纵向滑移率、纵向力和纵向滑移率在不同载荷下的力学关系特性。     

A semi-empirical dynamic tire model for combined-slip forces

This article presents a semi-empirical combined-slip tire model including transient behavior. It is assumed that the transient behavior is a result from the dynamic deformation of the tire carcass and that the interaction between the lateral and longitudinal slip, and forces can be explained by the deformation of the rubber treads. The deformation of the tire carcass makes the tread slip deviate from the wheel-rim motion in a way that may be described by differential equations. A method based on brush-model tire mechanics is used to construct the combined-slip forces as nonlinear scalings of corresponding pure-slip forces.     

A reduced-order nonlinear sliding mode observer for vehicle slip angle and tyre forces

In this paper, a reduced-order sliding mode observer (RO-SMO) is developed for vehicle state estimation. Several improvements are achieved in this paper. First, the reference model accuracy is improved by considering vehicle load transfers and using a precise nonlinear tyre model ‘UniTire’. Second, without the reference model accuracy degraded, the computing burden of the state observer is decreased by a reduced-order approach. Third, nonlinear system damping is integrated into the SMO to speed convergence and reduce chattering. The proposed RO-SMO is evaluated through simulation and experiments based on an in-wheel motor electric vehicle. The results show that the proposed observer accurately predicts the vehicle states.     

Prediction of tire natural frequency with consideration of the enveloping property

A lumped tire model was developed with consideration of the enveloping property in order to predict the natural tire frequency. Tire stiffness was classified into vertical, sidewall, and enveloping stiffnesses, and the tire characteristics were analyzed in detail experimentally and via finite element analysis. In addition, the effective masses of the tire tread and belt were extracted directly from design specifications taking into account the sizes and material properties of different rubber blocks. Using the design parameters of the tires, natural frequencies were calculated from the derived model and were compared with experimental results. Finally, based on good agreement with experimental results, sensitivity analysis was performed to verify the effect of tire stiffnesses on the natural frequencies.     

Development and validation of a Kalman filter-based model for vehicle slip angle estimation

It is well known that vehicle slip angle is one of the most difficult parameters to measure on a vehicle during testing or racing activities. Moreover, the appropriate sensor is very expensive and it is often difficult to fit to a car, especially on race cars. We propose here a strategy to eliminate the need for this sensor by using a mathematical tool which gives a good estimation of the vehicle slip angle. A single-track car model, coupled with an extended Kalman filter, was used in order to achieve the result. Moreover, a tuning procedure is proposed that takes into consideration both nonlinear and saturation characteristics typical of vehicle lateral dynamics. The effectiveness of the proposed algorithm has been proven by both simulation results and real-world data.     

Parameter identification for a LuGre model based on steady-state tire conditions

The purpose of this study was to effectively identify parameters for a LuGre friction model based on experimental measures. In earlier work related to this study (Yang et al., 2009), which was based on the characters of polygonal wear (Sueoka and Ryu, 1997), we showed a frictional vibration model for a mass on a moving belt. This model reflected lateral vibrations caused by velocity and toe-in angle. An important aspect of the present study is the improved friction model. A previous friction model, which divided the process into four parts, expressed the sable excited vibration well but failed to reflect the hysteresis loop change when vehicles accelerated or decelerated continuously. A LuGre friction model can solve this problem, but several model parameters must be obtained experimentally. We measured contact width and length of tires as vertical pressure changed; this provided a theoretical basis for apparent stiffness of a unit of tire tread. Based on tire data from Bakker E’s article in a SAE paper from 1987, we identified the Stribeck exponent and Stribeck velocity in LuGre. Then, the results were implemented in a vibration system that verified the rationality of the data.     

固定角软化桁架模型的新计算方法

对钢筋混凝土薄板单元的固定角软化桁架模型提出了一种从应力到应变的新计算方法 ,与原计算方法相比 ,该计算方法试算次数少 ,计算精度高 ,可以模拟 τlt～γlt曲线的下降段 ,计算结果与6个板的试验结果吻合较好。     

轮胎动力学特性仿真分析研究

分析了各种常用轮胎模型的特点与应用范围,根据汽车操纵动力学研究的需求,在Matlab环境下运用魔术公式建立了轮胎动力学模型,并对汽车轮胎力与纵向滑移率,纵向力、侧向力及回正力矩与纵向滑移率、侧偏角、外倾角、垂直载荷的关系等轮胎特性进行了仿真分析,实验结果表明,魔术公式轮胎动力学模型可以较好地模拟轮胎的动力学特性,适用于车辆动力学研究领域。     

动力总成悬置设计中惯性参数的灵敏度分析

分析动力总成惯性参数变化对系统振动特性的影响,进而确定参数测定或计算中的允许误差,对于悬置系统的成功设计具有重要意义。应用经典模态方法,推导了系统固有频率和主振动中最大振动能量对惯性参数灵敏度的计算式。结合具体实例,分析了动力总成质量、转动惯量以及惯性积对系统动态特性的影响,讨论了悬置系统设计中作为基本参数的惯性参数测定或计算结果可接受的误差容限。     

高速滚动汽车轮胎温度场的非稳态热分析

以试验数据为基础，分析了高速滚动轮胎温度场的非稳态热状况，应用最小二乘法对试验数据进行了拟合分析，建立了轮胎温升－时间历程关系式，并与理论计算公式作了对比，结果表明试验数据可靠；同时，分析了使用条件（速度、载荷、胎压及环境温度）对轮胎温升时间和大小的影响，结果表明，使用条件只影响轮胎温升大小，而不影响轮胎温升时间。用此方法建立了轮胎降温－时间历程关系式，分析了轮胎散热情况，分析表明温降时间也与使用条件无关。拟合关系式可用于初步预测轮胎温升及指导轮胎设计。     

载货汽车驾驶室疲劳寿命的敏感度分析

针对某重型载货汽车驾驶室底板发生开裂破坏的现象,建立了包含驾驶室柔性体的刚弹耦合动力学模型。由实测信号作为输入计算得到柔性体的应变-时间历程,进行驾驶室底板的疲劳寿命分析。在此基础上通过软件集成,以载荷幅值和材料特性为变量,用蒙特卡洛方法进行了疲劳寿命的敏感度分析,找到了影响较大的因素,为改进结构提供了依据。     

新能源汽车对主驱电机特性的敏感性研究

为研究新能源汽车能耗、性能匹配等关键因素对电机效率MAP的敏感性及其外特性影响,文章以一台8.5m纯电动公交大巴为研究对象,结合高级车辆仿真软件ADVISOR,对主驱电机性能匹配的敏感性因素进行了详实的分析,校核了电机的爬坡动力性能、最高车速性能,以及模拟了车辆在中国典型城市道路工况下的行驶里程及能量消耗情况,并提出了...     

基于灵敏度分析的SUV白车身优化设计

采用Hypermesh软件建立某SUV白车身有限元模型,通过Radioss对该模型进行自由模态分析计算;利用Optistruct对该模型的部分板件进行灵敏度分析,并以计算结果为依据,对白车身进行尺寸优化,在保证质量基本不变的情况下,提高一阶模态的频率。     

轿车白车身动态特征灵敏度分析及优化设计

建立了国产某轿车白车身有限元模型,计算得出了该白车身低阶振动固有频率和固有振型,进行了振动固有频率对壳体厚度等结构参数的灵敏度分析.在灵敏度分析的基础上,选取灵敏部件进行了结构优化设计.优化结果表明,该车身质量得到了更好的分布.     

Roll angle estimator based on angular rate measurements for bicycles

ABSTRACT

Measuring the roll angle of single-track vehicles has always been a challenging task; however, accurate and reliable measurements of this magnitude are paramount for controlling the stability of these vehicles, both for autonomous riding and for safety reasons. A roll angle estimation is also useful in other situations, such as tests to perform the identification of the parameters of the rider control. In this work, a new algorithm is presented for estimating the roll angle of bicycles. This estimator, based on the well-known Kalman filter, employs a wheel speed sensor to approximate the speed of the vehicle, and three angular rate sensors, which are currently small and affordable sensors. The proposed method was implemented in a microcontroller and tested in a bicycle and the results were compared with measurements obtained with optical sensors, showing a good correlation. Although it has not been tested in motorcycles, comparable results are expected.