考虑人机协调的基于转向和制动可拓联合的车道偏离辅助控制

针对基于电动助力转向和差动制动的两种车道偏离辅助控制方法的局限性,提出可拓联合控制策略。基于可拓控制理论,充分考虑路面环境信息和车辆状态,设计可拓联合控制器,该控制器将电动助力转向和差动制动进行联合控制,以实现车道偏离辅助。为解决车道偏离辅助过程中的人机协调问题,应用模糊神经网络控制理论,设计考虑驾驶员转矩和车辆侧向偏差的人机协调控制器,通过输出辅助权重动态地调整车道偏离辅助系统的辅助转矩,实现驾驶员与辅助系统的协调控制。在CarSim/Simulink联合仿真平台和CarSim/LabVIEW硬件在环试验台架上对所提出的控制策略进行仿真和试验验证,结果表明所提出的控制策略能够有效地避免车辆偏离出车道,同时降低驾驶员和辅助系统之间的相互干扰,减小人机冲突,有较好的人机协调性能。     

高速车辆车道偏离辅助控制研究

针对高速公路上因驾驶员注意力不集中或疲劳容易发生车辆偏离车道事故的问题,提出基于动态车辆横越车道线时间(Time to lane crossing,TLC)触发阈值的辅助控制决策策略和基于差动制动的车道偏离辅助控制方法。根据车-路航向角偏差、路面附着、车速、驾驶员反应时间及执行机构响应时间实时计算动态TLC触发阈值,进行预警和辅助控制决策。在辅助控制决策的基础上,基于预瞄点处的车-路偏差、车辆状态和道路附着限制计算期望的横摆响应,设计滑模控制器控制辅助横摆力矩,通过差动制动产生横摆力矩,使车辆横摆响应跟踪目标值,达到车道偏离辅助控制的目的。在Carsim/Simulink联合仿真平台上对基于差动制动的车道偏离辅助控制方法进行仿真试验,研究结果表明所提出方法将车辆限制在车道范围内,有效避免车道偏离事故发生。建立由CarsimRT/LabviewRT实时平台及转向、制动执行机构组成的车道偏离辅助控制系统快速原型试验台架,对基于差动制动的辅助控制方法进行台架试验,其结果与Carsim/simulink联合仿真结果基本一致。     

考虑驾驶员操纵失误的车道偏离辅助人机协同控制

人机协同控制车辆是降低道路交通事故的重要手段之一,针对因驾驶员操纵失误而引发的车道偏离问题,提出一种基于人机协同的车道偏离辅助控制方法。采用模型预测控制设计的车道偏离辅助控制器可保证车辆在不同速度下稳定地跟踪车道线,通过求解跨道时间并设定其阈值有效触发车道偏离预警,控制辅助系统开启与关闭。根据驾驶员状态、车辆状态、车路相对位置关系实时决策驾驶员与辅助控制器协同控制因子,并由协同因子决定辅助系统的转向力矩。CarSim/Simulink环境下的联合仿真及基于CarSim/LabVIEWRT的硬件在环试验表明:与驾驶员单独操纵相比,基于人机协同的车道偏离辅助系统在避免车道偏离的同时使横向偏差有所减小;与无协同控制相比,人机协同降低了控制器对驾驶员操纵的干预,充分说明所提出的人机协同车道偏离辅助方法提高了车辆行驶的安全性及驾驶舒适性。     

基于安全边界车道偏离防避高性能鲁棒控制

针对现有车道偏离防避系统不能适应不同驾驶风格驾驶人,车道偏离防避转向控制器设计未同时考虑车速解耦和轮胎侧偏刚度的不确定性的问题,文中基于道路环境和车辆动力学安全边界提出了车道偏离防避高性能鲁棒控制。根据车道曲率半径、不同驾驶风格下车辆行驶横向位置标准差和局部横向位置均值,设计了确定道路环境安全边界的虚拟车道模糊控制器;根据车辆2自由度模型获得了车辆动力学安全边界。建立了基于虚拟车道跨道时间(Time to Lane Crossing, TLC)和车辆动力学安全阈值的车道偏离决策准则。通过对车辆动力学模型轮胎侧偏刚度不确定边界分析设计了H_∞鲁棒控制器,实现了车速解耦,利用CarSim/Simulink联合仿真验证了车道偏离纠正鲁棒性能。仿真结果表明,基于虚拟车道线和车辆动力学安全边界所设计的高性能鲁棒控制器可以及时纠正车辆偏离车道,且驾驶员接受度高。     

基于μ综合方法的智能车辆人机共驾的鲁棒横向控制

在大多数智能车辆横向控制研究中,存在未考虑驾驶员误操作的影响这一不足。以人机共驾控制问题为研究对象,将驾驶员操纵转矩和车辆状态作为控制器输入。首先,建立转向系统和车辆二自由度模型,在车辆局部坐标系中,根据预瞄点曲率信息实现虚拟路径的规划,基于车辆状态和目标车道设计上层期望横摆角速度控制器。其次,将侧向风和驾驶员误操作作为干扰输入,以车辆状态中的横摆角速度、转向盘转角、转矩传感器测量值和期望横摆角速度作为控制器反馈变量,考虑车辆参数摄动及传感器测量噪声等影响,设计下层μ综合控制器,使车辆跟踪期望横摆角速度和期望的横向位移,确保车辆能稳定地跟踪目标路径。最后,进行自动换道和车道保持仿真,并基于Carsim/Labview的硬件在环试验台上进行硬件在环试验,仿真和试验结果均表明,提出的横向控制方法能辅助驾驶员更好的跟踪目标车道,且对侧向风和驾驶员误操作均有很好的干扰抑制性能。     

基于差动制动的车道偏离辅助控制

针对高速公路上因驾驶员注意力不集中容易发生车辆偏离车道事故的问题,提出采用四轮差动制动对车辆施加辅助横摆力矩以避免车辆偏离车道的方法。基于预瞄点处的车-路偏差、车辆状态和道路附着限制计算期望的横摆响应,设计滑模控制器控制辅助横 摆力矩。通过在同侧车轮定比例分配制动力产生横摆力矩,使车辆横摆响应跟踪目标值,达到车道偏离辅助控制的目的。在Carsim/Simulink联合仿真平台上对基于差动制动的车道偏离辅助控制方法进行仿真实验,研究结果表明所提出方法将车辆限制在车道范围内,有效避免了车道偏离事故的发生。     

基于参数时变人工势场的车道保持协调控制

针对传统人工势场法应用于车道保持系统时控制精度不高的问题,提出一种基于变参数道路势场的车道保持辅助控制方法。首先考虑汽车状态对车道保持控制的影响,引入汽车纵向车速和侧向车速两个变参数用于构建道路势场函数,通过势场梯度求解期望转向角。利用轨迹预测理论确定势场函数的设计参数,再建立包含变参数的路径跟踪误差变量状态方程模型,并分析闭环控制系统的稳定性。在此基础上,设计车道保持辅助转矩控制器,并考虑控制过程中的人机协调问题,以驾驶员转矩及其意图路径为输入,利用模糊规则动态地调整辅助控制权重。基于Matlab/Simulink和CarSim软件平台对所提出的控制方法进行仿真试验,其结果表明,该方法能够有效地提升车道保持控制精度,同时获得较好的人机协调性能。在CarSim/LabView硬件在环试验台架上对该方法进行试验验证,所得结论与仿真基本一致。     

人机协同下辅助驾驶系统的车道保持控制

为兼顾驾驶员和辅助驾驶系统在车道保持控制中的优势,根据实时驾驶员操作动作和车辆道路信息对车辆横向安全性进行评价,并对车辆控制权在驾驶员和辅助驾驶系统之间做出实时决策,以实现人机协同控制。在车道识别方面,采用了同帧图像的分区识别、相邻帧图像的车道候选区估计等方法。在车道跟踪控制时,根据车辆横向安全性高低采用不同控制策略,并基于模糊规则确定辅助驾驶控制力度以计算人机协同控制时的实际辅助驾驶控制量。在不同车速和不同道路条件下,采用人工驾驶和人机协同控制两种方式进行车道保持实车试验。试验结果表明,所采用的方法能够有效识别道路车道线,且人机协同控制下的车道跟踪具有较好的精确性和稳定性。     

人机协同控制的车道保持辅助系统安全性能研究

针对大部分车道保持辅助系统未考虑驾驶员行为和环境因素干扰,驾驶员模式和助力纠偏模式过渡困难,极易造成人机冲突等问题,提出了一种基于人机协同控制的车道保持辅助系统。该系统建立二自由度车辆动力学模型,通过最优线性二次型调节横向控制算法得到最优前轮转角;提出车辆偏离安全评估模型、扭矩控制和安全退出策略,实现了人机友好交互、协同共驾。基于CarSim/Simulink仿真平台对横向控制算法进行联合仿真,验证了控制算法的可行性,并在江淮轻卡试验车上进行了系统安全性能测试。仿真和试验结果表明该系统能够实现车道保持功能,获得较好的安全性。     

轮毂电机驱动汽车电子差速与差动助力转向的协调控制

为提高轮毂电机驱动电动汽车转向过程的操纵稳定性和转向轻便性,提出电子差速与差动助力转向的协调控制方法,通过分配左右轮毂电机的转矩,实现对汽车转向稳定性和转向盘转向助力协调优化控制。分别对电子差速与差动助力转向控制方式进行分析,得出两种控制趋势以及与车辆状态变化响应的一致性,验证了协调控制的可行性;采用设置权重系数的方法设计了协调控制策略。分析车速及转向盘转角对车辆横摆角速度以及驾驶员转向盘转矩的影响,设计出车速自适应的协调控制权重系数。进行Matlab与CarSim的联合仿真以及实车道路试验验证,仿真与道路试验结果均表明协调控制策略兼顾了车辆差速转向稳定性与驾驶员转向盘转向助力的性能,实现了低速时差动助力转向控制为主以降低驾驶员转向手力,高速时电子差速为主以提高车辆稳定性的综合控制目标。     

Lane departure avoidance by man-machine cooperative control based on EPS and ESP systems

The ability to avoid lane departure has become an important feature for development of driving assistance technology, and the design of lane departure avoidance system (LDAS) which can achieve cooperative control with human driver is still a challenge. This paper presented a new lane departure decision algorithm along with main parameters of the electric power steering (EPS) and electronic stability program (ESP) system’s sensor. During normal situations, steering control based on EPS system was involved to avoid lane departure. However, when the vehicle reached the handling limits, both steering and braking control collaborated together to avoid lane departure based on EPS and ESP systems. Due to the time varying vehicle speed and the uncertainty of tire cornering stiffness, a gain scheduling brake controller was designed based on the energy-to-peak performance indicator, and an upper monitor was designed for activation the braking controller to ensure comfortable ride. Because the relationship between the lane departure degree with a lateral offset in the single- point preview and the driver torque could not be accurately described, a man-machine cooperative control fuzzy observer for the LDAS was designed. In order to accomplish smooth switching for driving mode to ensure ride comfort, a switching criterion was proposed. The proposed method was evaluated via numerical simulation by CarSim/Simulink. A hardware-in-the-loop test platform was set up, and the effectiveness of the proposed control strategy was compared via the driver-in-the-loop experiment. The obtained results show that the proposed man-machine cooperative control strategy not only can return the vehicle to the normal lane effectively, but also realize smooth switching from man-machine cooperative control to driver control.

     

Development of a lane departure monitoring and control system

The lane departure avoidance systems have been considered promising to assist human drivers in AVCS (Advanced Vehicle Control System). In this paper, a lane departure monitoring and control system is developed and evaluated in the hardware-in-the-loop simulations. This system consists of lane sensing, lane departure monitoring and active steering control subsystems. The road image is obtained based on a vision sensor and the lane parameters are estimated using image processing and Kalman Filter technique. The active steering controller for avoiding the lane departure is designed based on the lane departure metric. The proposed lane departure avoidance system is realized in a steering HILS (hardware-in-the-loop simulation) tool and its performance is evaluated with a driver in the loop.     

四轮轮毂电机驱动智能电动汽车转向失效容错控制研究

四轮轮毂电机驱动电动汽车各轮驱动力矩独立可控,可通过控制前轴左右两轮的力矩差实现前轮转向。以四轮轮毂电机驱动智能电动汽车为研究对象,针对线控转向系统执行机构失效时的轨迹跟踪和横摆稳定性协同控制问题,提出一种基于差动转向与直接横摆力矩协同的容错控制方法。该方法采用分层控制架构,上层控制器首先基于时变线性模型预测控制方法求解期望前轮转角和附加横摆力矩,然后考虑转向执行机构建模不确定性以及路面干扰,设计基于滑模变结构控制的前轮转角跟踪控制策略。下层控制器以轮胎负荷率最小化为目标,利用有效集法实现四轮转矩优化分配。最后,分别在高速换道和双移线工况下仿真验证了该控制方法的有效性和实时性。     

一类基于轨迹预测的驾驶员方向控制模型

驾驶员方向控制模型在人-车-路闭环系统仿真、驾驶员辅助系统开发和智能汽车控制中具有重要作用。在假设驾驶员具有汽车轨迹预测能力的基础上,提出一类基于轨迹预测的驾驶员方向控制模型。分别假定汽车在将来一段时间内保持恒定的横摆角速度或横摆角加速度,并结合汽车状态参数预测汽车的行驶轨迹,采用期望式、增量式以及期望式与增量式集成的转角决策方法建立5种不同的驾驶员模型。在ve DYNA/Simulink联合仿真平台上对各驾驶员模型进行仿真试验,结果表明,增量式驾驶员模型表现出良好的路径跟踪精度和很强的鲁棒性,期望式模型的转向操纵更加平滑,而集成式模型则具备综合优势。在ve DYNA/Labview硬件在环实时试验台架上对所提出的驾驶员模型进行模拟试验,所得结论与仿真基本一致。     

基于滑模变结构理论的车辆主动横向稳定杆控制

为实现对车辆的侧倾控制,自主设计了主动横向稳定杆（AARB）装置。针对车辆在侧倾中存在的非线性、时变性特点,采用滑模变结构控制理论建立了滑模控制器从而实现对理想侧倾角的跟踪,并采用鱼钩与双移线转向工况进行了仿真试验。仿真结果表明,该主动横向稳定杆装置与传统被动横向稳定杆装置相比,能有效减小车辆的侧倾,同时具有良好反馈特性以,有利于驾驶员对车身姿态的判断,从而大大提高了车辆行驶的安全性与乘坐舒适性。     

Drive control algorithm for an independent 8 in-wheel motor drive vehicle

This paper describes a drive control algorithm based on optimal coordination of drive torque for an independent 8 in-wheel motor drive vehicle. The drive controller improves lateral stability and maneuverability. The drive controller consists of upper level controller and lower level controller. The upper level controller determines front, middle steering angle, additional net yaw moment and longitudinal net force according to the reference velocity and steering commands. The lower level controller coordinates additional tractive and braking forces to guarantee desired longitudinal net force and yaw moment. This controller is based on optimal control theory and takes into consideration the friction circle related to the vertical tire force and friction coefficient acting on the road and tire. Distributed tractive and braking forces are determined as proportional to the size of the friction circle according to the changes at driving conditions. The response of the 8 in-wheel drive vehicle implemented with this drive controller has been evaluated via computer simulations conducted using Matlab/Simulink dynamic model. Computer simulations of an open-loop J-turn maneuver and a closed-loop driver model subjected to double lane change have been conducted to demonstrate improved performance and stability of the proposed drive controller.     

Variable structure controller design for steer-by-wire system of a passenger car

The electric power steering (EPS) system was developed and the steer-by-wire (SBW) system achieves the purposes of EPS. The advantages of SBW are packaging flexibility, advanced vehicle control system, and superior performance. No mechanical linkage exists between the steering gear and steering column in the SBW system. The steering wheel and front-wheel steering can be controlled independently. The SBW system consists of two motors controlled by an electronic control unit (ECU). One motor is in the steering wheel and develops the steering feel of the driver and the other motor is in the steering linkage and improves vehicle maneuverability and stability. Moreover, the active front steering (AFS) system can be added to the SBW system. AFS reduces the difference between actual and estimated vehicle yaw rate. Up-to-date information from the steering wheel enables drivers to identify road conditions through the tire force, which should be fed back to the steering wheel. Furthermore, several control algorithms related to the vehicle and motor can be used together through the self-aligning torque, which is fed back to the steering wheel. This study proposes a method to control the vehicle yaw rate through an SBW system. This control method is based on a PID control method for the steering-wheel-motor controller, as well as on a sliding mode control (SMC) method for the front-wheel-motor controller and yaw stability controller. The SBW system is modeled using a bond graph method. Results imply that the controllers are robust enough when in contact with nonlinear properties of tire and road conditions. This study is expected to guide further research on the SBW system.     

电动转向控制系统跟踪性能研究

电动转向系统依靠助力电动机实现转向助力,控制系统的跟踪性能是影响电动转向系统助力性能的重要因素,较差的跟踪性能将会产生转向助力滞后现象,使驾驶路感变差。助力转矩偏差直接影响到转向系统的跟踪性能,影响助力转矩偏差的因素有转向盘输入转矩和转向轴转矩测量噪声,抑制转向盘输入转矩和转向轴转矩测量噪声引起的电动机助力转矩偏差是提高电动转向系统跟踪性能的有效手段。将H_∞控制理论应用于电动转向控制系统跟踪性能的研究,建立了电动转向系统数学模型,采用线性矩阵不等式处理方法设计了最优H_∞控制器,应用Matlab软件进行了计算机仿真,并根据最优H_∞控制器编制了电动转向系统控制程序,进行了台架试验。仿真和试验结果表明,所设计的电动转向控制系统具有较好的跟踪性能。