Nonlinear observer and robust controller design for enhancement of vehicle lateral stability

This paper describes the design of a sliding mode controller to control wheel slip. A yaw motion controller (YMC), which uses a PID control method, is also proposed for controlling the brake pressure of the rear and inner wheels to enhance lateral stability. It induces the yaw rate to track the reference yaw rate, and it reduces a slip angle on a slippery road. A nonlinear observer is also developed to estimate the vehicle variables difficult to measure directly. The braking and steering performances of the anti-lock brake system (ABS) and YMC are evaluated for various driving conditions, including straight, J-turn, and sinusoidal maneuvers. The simulation results show that developed ABS reduces the stopping distance and increases the longitudinal stability. The observer estimates velocity, slip angle, and yaw rate very well. The results also reveal that the YMC improves vehicle lateral stability and controllability when various steering inputs are applied. In addition, the YMC enhances the vehicle safety on a split-μ road.     

汽车ABS系统的PID控制策略及仿真分析

运用汽车动力学理论,建立了PID控制器模型、制动时整车动力学模型、车轮模型。提出了以滑移率为控制目标的ABS系统的控制仿真分析,将PID控制器应用于单个ABS系统控制研究,以车轮滑移率为控制目标,通过轮速与车速传感器采集汽车速度、车轮转速,计算出汽车各轮胎实际滑移率,与期望滑移率进行比较后,将二者的偏差作为PID控制器的输入量,反复调节控制器的控制参数,使其实际滑移率始终处于最佳滑移率附近,通过PID控制最终使汽车在最佳滑移率所对应的地面制动力下进行制动。     

基于MATLAB下的制动系统建模、仿真及ABS控制器设计

本文对某汽车ABS制动系统进行仿真建模,并对其进行单轮模型和分段线性的轮胎模型的建立;在Matlab环境下对ABS控制器进行设计和仿真分析;提出了一种门限值控制算法,对制动液压控制系统实现增压、保压、减压动作,使得汽车制动时的滑移率控制在一定范围内,以保证汽车的平稳制动.得出ABS控制下的滑移率时域结果图、车轮前进速度...     

Estimation of Road Friction Coefficient in Different Road Conditions Based on Vehicle Braking Dynamics

The accurate estimation of road friction coefficient in the active safety control system has become increasingly prominent. Most previous studies on road friction estimation have only used vehicle longitudinal or lateral dynamics and often ignored the load transfer, which tends to cause inaccurate of the actual road friction coefficient. A novel method considering load transfer of front and rear axles is proposed to estimate road friction coefficient based on braking dynamic model of two-wheeled vehicle. Sliding mode control technique is used to build the ideal braking torque controller, which control target is to control the actual wheel slip ratio of front and rear wheels tracking the ideal wheel slip ratio. In order to eliminate the chattering problem of the sliding mode controller, integral switching surface is used to design the sliding mode surface. A second order linear extended state observer is designed to observe road friction coefficient based on wheel speed and braking torque of front and rear wheels.The proposed road friction coefficient estimation schemes are evaluated by simulation in ADAMS/Car. The results show that the estimated values can well agree with the actual values in different road conditions. The observer can estimate road friction coefficient exactly in real-time andresist external disturbance. The proposed research provides a novel method to estimate road friction coefficient with strong robustness and more accurate.     

基于EMB和路面自动识别的汽车ABS仿真

针对电子机械制动系统(EMB)车辆进行研究,给出了简化的车辆仿真模型和EMB制动器仿真模型,并结合路面识别技术为之设计了相应的ABS模糊PID控制器仿真模型.ABS制动控制器模型采用基于车轮最优滑移率的控制策略,最优滑移率由路面自动识别系统准实时的得出,ABS控制算法采用模糊PID控制,对EMB制动器进行滑移率S和制动压力F的闭环控制.仿真采用Matlab中的simulink工具箱建模,仿真结果证明路面识别系统能够正确识别路面并确定最优滑移率,基于EMB制动控制器的车辆的ABS控制器始终将制动过程滑移率控制在路面识别系统确定的最优滑移率附近.     

Design,implementation, and test of skid steering-based autonomous driving controller for a robotic vehicle with articulated suspension

This paper describes an autonomous driving control algorithm based on skid steering for a Robotic Vehicle with Articulated Suspension (RVAS). The driving control algorithm consisted of four parts: speed controller for following the desired speed, trajectory tracking controller to track the desired trajectory, longitudinal tire force distribution algorithm which determines the optimal desired longitudinal tire force and wheel torque controller which determines the wheel torque command at each wheel to keep the slip ratio below the limit value as well as to track the desired tire force. The longitudinal and vertical tire force estimators were designed for optimal tire force distribution and wheel slip control. The dynamic model of the RVAS is validated using vehicle test data. Simulation and vehicle tests were conducted in order to evaluate the proposed driving control algorithm. Based on the simulation and test results, the proposed driving controller was shown to produces satisfactory trajectory tracking performance.     

Improvement of vehicle directional stability in cornering based on yaw moment control

In this research any abnormal motion of a vehicle is detected by utilizing the difference between the reference and actual yaw velocities as sell as the information on vehicle slip angle and slip angular velocity. This information is then used as a criterion for execution of the yaw moment control. A yaw moment control algorithm based on the brake control is proposed for improving the directional stability of the vehicle. The controller executes brake controls to provide each wheel with adequate brake pressures, which generate the needed yaw moment. It is shown that the proposed yaw moment control logic can provide excellent cornering capabilities even on low friction roads. This active control scheme can prevent a vehicle from behaving abnormally, and can assist normal drivers in coping with dangerous situations as well as experienced drivers.     

基于鲁棒积分滑模的四轮轮毂电机驱动电动汽车电液复合制动防抱死控制研究

为了充分发挥四轮轮毂电机驱动电动汽车电机制动与液压摩擦制动响应快且独立可控的优势,提高紧急制动时车辆稳定性与安全性,提出一种基于鲁棒积分滑模的电液复合制动防抱死控制策略。采用分层控制架构,上层控制器为基于鲁棒积分滑模的车轮滑移率控制,下层控制器为电液复合制动力协调分配。建立整车动力学与电液复合制动系统模型,基于Simulink-AMESim-Carsim联合仿真平台,在四种典型制动工况下对上述电液复合制动防抱死控制策略进行仿真验证。结果表明,在无需实时获取路面附着系数与轮胎纵向力的情况下,所提出的控制策略仍能消除外界干扰使车轮滑移率收敛至期望值,适用于多种紧急制动工况,响应迅速且鲁棒性强;电机再生制动与液压摩擦制动可稳定协同工作,在保证制动可靠性的同时提升了乘坐舒适性。     

Brake performance evaluation of ABS with sliding mode controller on a split road with driver model

In this paper, Sliding Mode Controller (SMC) is proposed to enhance Anti-Lock Brake System (ABS) performance. To verify SMC performance, a real-time Hardware in the loop simulation has been created with a hydraulic brake line. Therefore, the hydraulic brake model and vehicle model should be properly set up to acquire exact simulation results. In addition, the experiment results are compared with that of the commercial ABS with ECU only, and verified how much the performance is improved. The control strategy is to follow the target slip ratio by means of sliding mode controller and secure the vehicle stability while the vehicle braking on various road conditions, such as dry road, wet road, icy road and even split road condition. The driver model is useless on the uniform slip ratio of a straight road. However, the split road has to adopt the driver model. The split road condition has a different slip ratio at each wheel, causing the vehicle to spin out. Test results show that ABS with sliding mode controller has better performance than existing ABS and also ensures improved vehicle stability. Furthermore, the test result on the split road shows how the vehicle will follow the desired path with the driver model and hold the target slip ratio.     

汽车防抱死制动系统分级智能控制

在分析车辆制动时轮胎与地面接触力学特性的基础上,提出一种用轮速峰值连线来求解参考车速和参考滑移率的方法。为了解决汽车防抱死制动系统(ABS)在各种条件下复杂的控制问题,设计出一种由运行控制、参数校正和组织协调构成的分级智能控制系统。在运行控制级,给出参考滑移率误差的目标轨迹,建立特征模型、控制模态集和推理规则集,以此设计出基于参考滑移率的仿人智能控制器。在参数校正级,为了弥补只针对参考滑移率控制的不足,用车轮角减速度对仿人智能控制量进行校正。在组织协调级,设计出基于轮减速度和参考滑移率的模糊智能控制器来自动辨别制动时的路面信息,给出四轮制动的协调控制规则。运用Matlab进行汽车ABS的仿人智能控制系统研究,搭建出汽车ABS全车测控系统,参照国际标准,在不同条件下进行道路试验。试验结果表明,相对于逻辑门限控制,ABS分级智能控制具有良好的制动平稳性和自适应性,可提高控制精度,是一种有效的新的ABS控制方法。     

电源特性对电子机械制动防抱死性能的影响研究

为研究电子机械制动系统(EMBS)的电源特性对其制动防抱死性能的影响,阐述了EMBS制动防抱死工作原理,建立了带有EMBS的单轮车辆动力学模型,以脉宽调制变换器的占空比为控制量,设计了基于车轮滑移率的制动防抱死滑模变结构控制器.对控制模型在Matlab/Simulink环境下进行的仿真分析结果表明:系统具有良好的稳定性...     

四轮驱动汽车牵引力控制算法

提出了实用的四轮驱动汽车牵引力控制算法。在确定控制系统结构的基础上,设计了车速估算算法、油门位置PI控制器和制动门限控制算法。为实现牵引力控制算法的快速开发,建立由传感器、执行器、工控机、采集卡和输入输出电路组成的车载快速开发平台。硬件在环试验和道路试验表明:传感器能准确检测输入信号,控制算法能根据输入信号生成控制指令,执行器能快速、准确产生动作以消除驱动轮过度滑转。     

四轮轮毂电机驱动电动汽车电液复合制动平顺性控制策略

液压制动与电机再生制动的时域响应差异导致电动汽车在制动模式切换时产生冲击感,影响驾驶员驾驶感受和乘坐舒适性。以四轮轮毂电机驱动电动汽车为研究对象,提出一种基于分层架构的电液复合制动平顺性控制策略。针对"高压蓄能器+电机泵"式电子液压制动系统(EHB),上层控制器提出基于模糊控制的轮缸压力控制策略;针对制动模式切换过程中产生的冲击,下层控制器提出包括液压介入预测模块和电机制动补偿模块的电液复合制动平顺性控制策略。通过Simulink-AMESim联合仿真平台进行仿真试验验证。结果表明,轮缸压力控制策略能够保证轮缸液压力较好地追随目标压力,且稳态误差不超过2%;电液复合制动平顺性控制策略能够有效提高制动系统的响应速度,同时显著降低制动模式切换时的冲击,能提升车辆制动平顺性和乘坐舒适性。     

Design and performance analysis of an iterative flux sliding-mode observer for the sensorless control of PMSM drives

To improve the performance of permanent magnet synchronous motor (PMSM) drives, a sensorless control scheme based on a novel iterative flux sliding-mode observer (IFSMO) is proposed in this paper. Two major drawbacks of the conventional sliding-mode observer (SMO), namely, chattering phenomena and high-order harmonics, are discussed. These drawbacks affect the estimation accuracy of the SMO and reduce the control reliability of the system. To eliminate high-order harmonics, a flux SMO is designed by expanding the PMSM state equations with the PM flux. The flux SMO estimates the rotor speed and position using the flux linkage instead of back-EMF information. Moreover, to reduce the chattering in the estimation results, the proposed flux SMO is iteratively used in one current sampling period to adaptively adjust the observer gain. An overall PMSM sensorless control system based on the proposed IFSMO is designed, and an experimental platform using the TMS320F28335 digital signal processor (DSP) controller is built. The superior chattering reduction and harmonic suppression characteristics of the proposed IFSMO are experimentally validated, and the experimental results verify the feasibility of using the proposed IFSMO-based PMSM sensorless scheme in practical applications.     

MB-CVT电液控制系统智能优化设计

为了提高配有金属带式无级变速器车型燃油经济性,提出基于滑模极值搜索理论的控制算法和基于滑模极值搜索控制与传统夹紧力控制相结合的一体化式联合控制方法;设计了滑模极值搜索控制和传统液压控制合为一体化的联合控制系统。建立具有非线性、离散性的数学模型;分析无级变速器传动效率和金属带滑差率在一定速比下存在特殊曲线关系;测试主/从动轮夹紧力比值系数,完成了速比跟踪控制器及变化率控制流程设计。依据滑模极值搜索算法原理,完成了滑模极值搜索控制器设计。在具有环境仓的转鼓试验台上进行整车试验,试验结果表明:采用一体化式控制的金属带式无级变速器车型油耗为7.18L/100km,比传统控制系统的油耗降低约5.64%;主、从动压力安全系数倒数指标均小于1。满足整车提高燃油经济需求的可靠性、稳定性及优化性能。     

汽车ABS制动过程车速的一种测量方法

汽车ABS是改善汽车主动安全性的重要装置。通过调节制动力,使汽车获得良好的制动效能并保持罗高方向操纵稳定性,车轮滑移率是制动力调节的主要依据,车速是其不可缺少的参数,本文提出一种利用对加速传感器测得的加速度积分获得制动过程车速的方法,并经试验证实其可行性。     

Advanced lagged slip ratio for stable analysis of wheel dynamics at low-speed and high-speed

Real-time interpretation of a vehicle is mainly used for the speed estimation of autonomous vehicles and hardware-in-the-loop simulation. For real-time analysis of vehicles, an explicit integrator is more suitable than an implicit integrator. The implicit integrator guarantees the stability of the numerical analysis, whereas the explicit integrator requires a smaller amount of computation, which enables quick analysis. However, the lagged slip ratio, which is the most typical slip ratio in the tire model for vehicle dynamics simulation, shows that the numerical results of the explicit integrator are unstable in low-speed and high-speed driving situations. This is because the pole of the wheel dynamics system applying the lagged slip ratio deviates from the stability region of the explicit integrator depending on the driving speed. Generally, the instability of the lagged slip ratio is eliminated by applying an arbitrary damper system. In this study, an advanced lagged slip ratio is proposed to maintain the pole of the wheel dynamics in the stability region using an explicit integrator. The validity and stability of the proposed method is confirmed by comparing the driving simulation results with the conventional slip ratio.     

Development and comparison of integrated dynamics control systems with fuzzy logic control and sliding mode control

In this study, four integrated dynamics control (IDC) systems abbreviated as IDCB, IDCS, IDCF, and IDCR are developed, evaluated and compared. IDC systems were integrated with brake and steer control systems to enhance lateral stability and handling performance. To construct the IDC systems, a vehicle model with fourteen degrees of freedom, a fuzzy logic controller, and a sliding mode ABS controller were used. They were tested with various steering inputs when excessive full brake pressure or no brake pressure was applied on dry asphalt, wet asphalt, a snow-covered paved road, and a split-μ road. The results showed that an IDC-equipped vehicle improved lateral stability and controllability in every driving condition compared to an ABS-equipped vehicle. Under all road conditions, IDC controllers enabled the yaw rate to follow the reference yaw rate almost perfectly and reduced the body slip angle. On a split-road, IDCB, IDCS, IDCF, and IDCR vehicles drove straight ahead with only very small deviations.     

Variable parameter sliding controller design for vehicle brake with wheel slip

In this paper, a 4-wheel vehicle model including the effects of tire slip was considered, along with variable parameter sliding control, pushrod force as the end control parameter, and an antilock sliding control, in order to improve the performance of the vehicle longitudinal response. The variable sliding parameter is made to be proportional to the square root of the pressure derivative at the wheel, in order to compensate for large pressure changes in the brake cylinder. A typical tire force-relative slip curve for dry road conditions was used to generate an analytical tire force-relative slip function, and an antilock sliding control process based on the analytical tire force-relative slip function was used. A retrofitted brake system, with the pushrod force as the end control parameter, was employed, and an average decay function was used to suppress the simulation oscillations. Simulation results indicate that the velocity and spacing errors were slightly larger than the results that without considering wheel slip effect, the spacing errors of the lead and follower were insensitive to the adhesion coefficient up to the critical wheel slip value, and the limit for the antilock control on non-constant adhesion road condition was determined by the minimum of the equivalent adhesion coefficient.     

ABSs系统模糊控制器优化设计

已经开发了的ABSs系统改善了突然制动和特别是滑动路面状况时车辆控制。这样的控制目标是在保持车辆合适稳定性及可操纵性和缩短车辆刹车距离情况下在要求的方向增大车轮的牵引力。本文提出了ABSs系统优化的模糊控制器。从保持其车轮滑动值为目标函数获得车轮最大的牵引力和车轮最大的减速度。采用遗传算法优化模糊系统的全部组件。采用误差数整体优化方法收敛接近最优点。仿真结果表明快速收敛和对不同路况的控制器的最好性能。