车-车协同下无人驾驶车辆的换道汇入控制方法

多车协同驾驶是智能车路系统领域的研究热点之一,可有效降低道路交通控制管理的复杂程度,减少环境污染的同时保障道路交通安全。基于多车协同驾驶控制结构,提出了一种无人驾驶车辆换道汇入的驾驶模型及策略,系统分析了多车协同运行状态的稳定条件。在综合分析无人驾驶车辆换道汇入的协作准则、安全性评估后,基于高阶多项式方法,结合车辆运行特性,通过引入乘坐舒适性的指标函数,设计得到无人驾驶车辆换道汇入的有效运动轨迹。通过研究汇入车辆与车队中汇入点前、后各车辆的运动关系,详细分析车辆发生碰撞的类型和影响因素,给出避免碰撞的条件准则,从而确保无人驾驶车辆汇入过程中多车行驶的安全性和稳定性。基于车辆运动学建立车辆位置误差模型,结合系统大范围渐进稳定的条件,选取线速度和角速度作为输入,应用李雅普诺夫稳定性理论和Backstepping非线性控制算法,设计了无人驾驶车辆换道汇入后的路径跟踪控制器。仿真试验和实车试验结果表明：所设计的换道汇入路径是可行、安全的,控制器具有良好的跟踪效果,纵向和横向的距离误差在15 cm以内,方向偏差的相对误差在10%以内。研究结果为智能车路系统中的多车状态变迁与协同驾驶研究提供了参考,可服务于未来道路交通安全设计和评价。     

Safe Platooning in Automated Highway Systems Part II: Velocity Tracking Controller

This paper presents the design of a velocity tracking controller for safe vehicle maneuvering in Automated Highway Systems (AHS) in which traffic is organized into platoons of closely spaced vehicles. The notion of safety is related to the absence of collisions that exceed a given relative velocity threshold. In a companion paper, state dependent safety regions for the platoons are designed in such a way that, whenever the state of a platoon is inside these safety regions, it is guaranteed that platoon maneuvering will be safe and follow the behavior prescribed by the finite state machines that control vehicles maneuvers. Velocity profiles inside these safety regions are derived for all the single lane maneuvers and a nonlinear velocity tracking controller is designed to track these profiles. This controller attempts to complete the maneuvers with comfort in minimum time, whenever safety is not compromised. The control schemes presented in this paper were implemented and tested using AHS simulation software.     

车路协同下车队避让紧急车辆的换道引导方法

为保证紧急车辆更安全、高效地到达紧急事故现场,基于车路协同系统,提出车队避让紧急车辆的换道引导策略。针对目标车道无车辆、有车辆和有车队3种不同场景,分别提出确保紧急车辆快速通过的协同换道策略。通过协同换道策略引导紧急车辆前方行驶的车队和目标车道的车辆改变速度以调整车辆间距,使其满足换道安全距离,依据换道轨迹规划使车队完成换道,并提出紧急车辆发送紧急避让信号的位置方法,计算当不影响紧急车辆的速度情况下,其发送紧急避让信号时与车队尾车的最短距离。利用SUMO交通仿真软件,实现车路协同环境下3种不同场景车队避让紧急车辆的换道引导,并比较目标车道为车队的场景下,车队换道至目标车队的每个空档中（方式A）和车队换道至目标车队的同一个空档中（方式B）2种不同的换道引导策略。研究结果表明：目标车道有车队的场景下,方式B的协同换道时间更短,发送紧急信号的位置距车队尾车82 m,较方式A的87 m更近,对周围车辆影响更小,因此此场景采用方式B的协同换道策略;在目标车道无车辆、有车辆和有车队3种场景下,紧急车辆分别距车队尾车71,71,82 m时发送紧急避让信号,其可以维持期望速度,验证了最短距离与车辆速度的关系式;与未使用换道引导策略的情况相比,紧急车辆的速度提高,延误减少。     

纯电动商用车异质队列的多目标控制

队列行驶的研究能有效解决商用车货运安全、能耗浪费和环境污染等问题,但现有研究多基于单一跟车目标控制的匀质队列,这在货运场景中无法达到很好的控制效果。本文中构造了纯电动异质商用车队列,为其设计了分布式非线性模型预测控制器。根据道路环境信息和车辆跟车、安全、舒适和节能等特性,分别建立了领航车和跟随车的控制器模型,实现异质队列的多目标控制。为验证所提出控制方法的有效性,由5辆动力学特性相异的商用车组成队列,并搭建了控制仿真平台进行Trucksim/Simulink联合仿真。结果表明,本文中提出的控制算法能有效实现异质商用车队列的多目标控制,与PID定速巡航控制相比,能耗可降低5.3%以上。     

基于自然驾驶数据的切入场景队列跟驰仿真

车辆切入是常见的驾驶行为，频繁的变道切入行为影响了通行效率与交通安全。因此，揭示切入场景下的驾驶特性对研究交通拥堵和行驶安全机理具有重要意义。在自然驾驶数据的基础上，根据驾驶人的主观风险感知特性，探究驾驶人的切入行为发生条件，并在期望安全裕度（DSM）模型的基础上，标定了切入场景下的相关参数，根据标定结果进行切入场景下的队列跟驰仿真。仿真结果表明:在仿真区间内，队列的长度、行驶速度以及切入车的切入位置不同会影响队列的稳定性以及队列的调整，当队列长度由4辆变为13辆，速度由5 m/s增至20 m/s，切入车的位置由贴近前后车变为前后2辆车中间时，切入行为对队列的稳定性影响变得越小，队列越容易恢复到稳定状态。      

Fuzzy Logic Traction Controllers and their Effect on Longitudinal Vehicle Platoon Systems

This paper presents two fuzzy logic traction controllers and investigates their effect on longitudinal platoon systems. A fuzzy logic approach is appealing for traction control because of the nonlinearity and time-varying uncertainty involved in traction control systems

The fuzzy logic traction controllers we present regulate brake torque to control wheel slip, which is the normalized difference between wheel and vehicle speed. One fuzzy controller estimates the peak slip corresponding to the maximum tire-road adhesion coefficient and regulates wheel slip at the peak slip. The controller is attractive because of its ability to maximize acceleration and deceleration regardless of road condition. However, we find through simulations the controller's performance degrades in the presence of time-varying uncertainties. The other fuzzy logic controller regulates wheel slip at any desired value. Through simulations we find the controller robust against changing road conditions and uncertainties. The target slip is predetermined and not necessarily the peak slip for all road conditions. If the target slip is set low, stable acceleration and deceleration is guaranteed, regardless of road condition

We also study the effect of traction control on longitudinal vehicle platoon systems using simulations. The simulations include acceleration and deceleration maneuvers on an icy road. The results indicate traction control may substantially improve longitudinal platoon performance, especially when icy road conditions exist.     

Automated Vehicle Merging Maneuver Implementation for AHS

Summary This paper presents a real-time implementation of a general merging algorithm for automated highway systems. A merging control problem is proposed first. A real-time algorithm is then presented, which is used to calculate a smooth reference speed trajectory for the merging vehicle based on the speed of the main lane vehicle. This algorithm can also be applied even when the main lane vehicles change speed. To make the algorithm adapt to different road layouts and to increase safety, a concept of virtual platooning is proposed. It effectively shifts the time of platoon formation forward prior to the start of real merging. Aspects closely related to real-time implementation are discussed, such as the controller adopted, the use of magnetometer based distance measurement and information passing by communication from main lane vehicles. Test results are presented and briefly analyzed.     

Design and Evaluation of Robust Cooperative Adaptive Cruise Control Systems in Parameter Space

This paper is on the design of cooperative adaptive cruise control systems for automated driving of platoons of vehicles in the longitudinal direction. Longitudinal models of vehicles with simple dynamics, an uncertain first order time constant and vehicle to vehicle communication with a communication delay are used in the vehicle modeling. A robust parameter space approach is developed and applied to the design of the cooperative adaptive cruise control system. D-stability is chosen as the robust performance goal and the feedback PD controller is designed in controller parameter space to achieve this D-stability goal for a range of possible longitudinal dynamics time constants and different values of time gap. Preceding vehicle acceleration is sent to the ego vehicle using vehicle to vehicle communication and a feedforward controller is used in this inter-vehicle loop to improve performance. Simulation results of an eight vehicle platoon of heterogeneous vehicles are presented and evaluated to demonstrate the efficiency of the proposed design method. Also, the proposed method is compared with a benchmark controller and the feedback only controller. Time gap regulation and string stability are used to assess performance and the effect of the vehicle to vehicle communication frequency on control system performance is also investigated.     

A real-time multi-vehicle simulator for longitudinal controller design

This paper presents a new multi-vehicle simulator for platoon simulation. The main new feature of the developed simulator is a network structure for the real-time simulation of multiple vehicles, each with a detailed powertrain and engine model. It has a small initial delay, which is determined by the number of connected PCs, but the actual simulation is performed and displayed in real-time after this initial and one-time delay. Several longitudinal controllers, including a PID controller with gain scheduling, an adaptive controller, and a fuzzy controller, are also implemented in the simulator. Various system parameters can be modified interactively in the simulator screen, which is very useful for simulating a platoon of heterogeneous vehicles, in which vehicles with different dynamics and different longitudinal controllers may be involved. The simulator provides an excellent tool to develop vehicle longitudinal controllers and to study platoon behaviors. The developed simulator is also effective in testing the effects of nonlinearities neglected in the controller design phase, such as actuator delays and gear shifting schedule.     

A real-time multi-vehicle simulator for longitudinal controller design

This paper presents a new multi-vehicle simulator for platoon simulation. The main new feature of the developed simulator is a network structure for the real-time simulation of multiple vehicles, each with a detailed powertrain and engine model. It has a small initial delay, which is determined by the number of connected PCs, but the actual simulation is performed and displayed in real-time after this initial and one-time delay. Several longitudinal controllers, including a PID controller with gain scheduling, an adaptive controller, and a fuzzy controller, are also implemented in the simulator. Various system parameters can be modified interactively in the simulator screen, which is very useful for simulating a platoon of heterogeneous vehicles, in which vehicles with different dynamics and different longitudinal controllers may be involved. The simulator provides an excellent tool to develop vehicle longitudinal controllers and to study platoon behaviors. The developed simulator is also effective in testing the effects of nonlinearities neglected in the controller design phase, such as actuator delays and gear shifting schedule.     

汽车半主动悬架的模型参考自适应控制

在1／4车辆动力学模型的基础上，基于李雅普诺夫稳定性理论，以天棚阻尼半主动悬架为参考模型，设计了半主动悬架模型参考自适应控制器。自适应控制器包括可调前置控制器和状态反馈控制器两个部分。推导了自适应控制律与相应的约束条件。仿真结果表明：该控制器对于模型参数的不确定性具有良好的鲁棒特性。自适应控制器不仅明显降低了车身加速度，提高了平顺性，同时也使汽车的行驶安全性获得了改善，悬架动变形稍有增大。     

Decoupled robust control of vehicular platoon with identical controller and rigid information flow

Platoon driving has potential to significantly benefit road traffic. This study presents a decoupled robust control strategy for a vehicular platoon with identical feedback controller and rigid information topology. The node dynamics of vehicle with a lower-level controller is assumed to be covered by a multiplicative uncertainty model. The vehicular platoon control system is skillfully decomposed into an uncertain part and a diagonal system by applying linear transformation and eigenvalue decomposition on information flow graph. Then the requirements of robust stability and distance tracking error are equivalent to the H-infinity norm of decoupled sub-systems. Comparative simulations with a non-robust controller and different communication topologies are conducted to demonstrate the robust stability and distance tracking performances of the proposed method.     

Safety Oriented Maneuvers for IVHS

The IVHS architecture of the California PATH program organizes traffic into platoons of closely spaced vehicles. Platoons are formed and broken up by two longitudinal control maneuvers, the merge and the split. A third longitudinal maneuver, decelerate to change lane, allows a platoon switching from one lane to another to enter its new lane at a safe spacing and speed. The maneuvers, particularly the merge, can be potentially hazardous. In a merge, the cars in the trail platoon are moving faster than those in the lead platoon, while the gap separating the two platoons is smaller than usual. A sudden deceleration by the lead platoon could cause a high-speed collision. If the relative velocities of the merging platoons can be constrained so that they are guaranteed never to collide at a high relative velocity, the merge can be considered safe. A maximum safe velocity for the trail platoon can be found for any given spacing and lead-platoon velocity. This paper presents a merge maneuver in which the velocity of the trail platoon never exceeds the maximum safe velocity. The controller switches among several feedback control laws that keep the velocity of the trail platoon inside a safe region and within comfort limits on jerk and acceleration, under normal circumstances. This merge maneuver can be considered to be the fastest merge strategy mat does not violate bounds on safety and comfort. The controller is also more robust to changes in the vehicles' acceleration capability than those that use a desired open-loop trajectory

The control approach used for the merge maneuver can be applied to the other maneuvers to ensure that they never result in a collision. The switching controllers for the split and decelerate to change lane maneuvers that are safe and yield a more comfortable ride than those that track a timed trajectory are also presented.     

路段上集群智能网联汽车的车队形成机制

智能网联汽车是解决城市交通问题的关键技术之一,对于未来城市智能交通体系建设有着关键作用。集群的智能网联汽车已经具备了涌现的基本条件,设计科学合理的交互规则,可以实现车辆的自组织,分布式涌现控制。以微观仿真软件VISSIM及C2X模块为研究平台,修改驾驶模型参数,在C2X模块中编程实现3条交互规则:速度一致、尽量靠近、避免碰撞,在仿真软件中构建单车道仿真模型,运行仿真实验,统计车辆在路段上不同距离形成车队情况,利用车头时距分布的熵值来衡量车流的有序性。仿真结果表明,车辆在运行至50s后初步形成车队,随着时间的增加,形成的车队越稳定,车流熵值在路段上随距离增加而减小,说明形成车队后更加有序,在路段上呈现出涌现现象。     

队列行驶车辆间距对气动特性的影响

为了研究车辆前后间距和车辆数目对智能交通系统中队列行驶车辆气动特性的影响,首先对单辆车进行数值模拟,并将模拟结果与风洞试验结果进行对比,然后对两辆车在5种不同间距下以及3～7辆车在固定间距下队列行驶的情况分别进行了数值模拟及分析。研究表明:单辆车数值模拟结果与风洞试验结果基本吻合。队列行驶车辆随着车辆间距的减小,各车阻力系数不断降低。在固定间距下,随着队列中车辆数目的增加,平均阻力系数可降低20%～30%,阻力最低的车大致处于车队的中心位置。     

Safe Platooning in Automated Highway Systems Part I: Safety Regions Design

This paper addresses the problem of designing safe controllers for vehicle manuevering in Automated Highway Systems (AHS) in which traffic is organized into platoons of closely spaced vehicles. Conditions to achieve safe platooning under normal modes of operation are investigated. The notion of safety is related with the absence of collisions that exceed a given relative velocity threshold. State dependent safety regions for the platoons are designed in such a way that, whenever the state of a platoon is inside these safety regions, it is guaranteed that platoon maneuvering will be safe and follow the behavior prescribed by the finite state machines that control vehicles manuevers. It is shown that it is possible to design control laws that keep the state of the platoons inside these safety regions. The results obtained allow one to decouple the controllers for the regulation of the manuevers and the finite state machines that determine their proper sequence in AHS architectures. The overall complexity of the design and verification of the AHS as an hybrid system is therefore greatly reduced.     

Safe Platooning in Automated Highway Systems Part I: Safety Regions Design

This paper addresses the problem of designing safe controllers for vehicle manuevering in Automated Highway Systems (AHS) in which traffic is organized into platoons of closely spaced vehicles. Conditions to achieve safe platooning under normal modes of operation are investigated. The notion of safety is related with the absence of collisions that exceed a given relative velocity threshold. State dependent safety regions for the platoons are designed in such a way that, whenever the state of a platoon is inside these safety regions, it is guaranteed that platoon maneuvering will be safe and follow the behavior prescribed by the finite state machines that control vehicles manuevers. It is shown that it is possible to design control laws that keep the state of the platoons inside these safety regions. The results obtained allow one to decouple the controllers for the regulation of the manuevers and the finite state machines that determine their proper sequence in AHS architectures. The overall complexity of the design and verification of the AHS as an hybrid system is therefore greatly reduced.     

队列车辆碰撞严重性及车队排布策略

针对自动驾驶车辆队列发生不可避免碰撞的事故场景,研究以整体碰撞严重性达到最低为目标的车队排布策略.首先根据引发事故的障碍物是否会明显影响领航车运动,将碰撞划分为队内碰撞和队外碰撞.队列几何构型一定时,针对均质化队列发生一维碰撞过程建立理论模型,计入碰撞前车辆对前车紧急制动的感应及自车进行紧急制动的过程,计算并定义时间截...     

Fuzzy adaptive sliding mode controller for an air spring active suspension

A fuzzy adaptive sliding mode controller for an air spring active suspension system is developed. Due to nonlinearity, preload-dependent spring force and parameter uncertainty in the air spring, it is difficult to control the suspension system. To achieve the desired performance, a fuzzy adaptive sliding mode controller (FASMC) is designed to improve the passenger comfort and the manipulability of the vehicle. The fuzzy adaptive system handles the nonlinearity and uncertainty of the air suspension. A normal linear suspension model with an optimal state feedback control is designed as the reference model. The simulation results show that this control scheme more effectively and robustly isolates vibrations of the vehicle body than the conventional sliding mode controller (CSMC).     

Generalized magnetorheological (MR) damper model and its application in semi-active control of vehicle suspension system

In this paper, analytical characterization of the magneto-rheological (MR) damper is done using a new modified algebraic model. Algebraic model is also more preferable because of its low computational expenses compared to differential Bouc-Wen’s model which is highly computationally demanding. This model along with the obtained model parameters is used as a semi-active suspension device in a quarter car model and the stationary response of the vehicle traversing on a rough road is obtained. The control part consists of two nested controllers. One of them is the system controller which generates the desired damping force and the other is the damper controller which adjusts the voltage level to MR damper so as to track the desired damping force. For the system controller a model reference skyhook Sliding Mode Controller (SMC) is used and for the damper controller a continuous state algorithm is built to determine the input voltage so as to gain the desired damping force. The analytical model is subsequently used in the quarter car vehicle model and the vehicular responses are studied. A simulation study is performed to prove the effectiveness and robustness of the semi-active control approach. Results show that the semi-active controller can achieve compatible performance as that of active suspension controller except for a little deterioration.