基于轨迹预瞄的智能汽车变道动态轨迹规划与跟踪控制

为实现实际动态交通环境下智能汽车的变道控制, 提出了基于轨迹预瞄的智能汽车变道动态轨迹规划与跟踪控制策略; 针对实际交通环境下目标车道车速和加速度的动态变化, 提出了智能汽车变道动态轨迹规划算法, 获得了能够避免智能汽车发生碰撞的变道轨迹的动态最大纵向长度; 设计了兼顾变道效率和乘员舒适性的优化目标函数, 优化获得了在变道轨迹最大纵向长度范围内的实时动态最优变道轨迹; 利用轨迹预瞄前馈和状态反馈相结合的类人转向控制方式, 实现了智能汽车变道动态轨迹跟踪和乘员舒适性的最优控制, 并利用硬件在环试验台验证了所提控制策略的正确性。研究结果表明: 定速工况下实际与参考轨迹的侧向位移误差、航向角误差和最大侧向加速度分别为1.4%、4.8%和0.59 m·s^-2; 定加速度工况下实际与参考轨迹的侧向位移误差、航向角误差和最大侧向加速度分别为1.1%、4.6%和0.48 m·s^-2; 变加速度激烈工况下实际与参考轨迹的侧向位移误差和最大侧向加速度分别为1.7%和0.80 m·s^-2, 航向角超调后能迅速重新跟踪动态轨迹航向角; 所提控制策略可以很好地跟踪控制实际交通环境下目标车道汽车在定车速、定加速度和变加速度工况下的智能汽车动态变道轨迹, 从而能实现智能汽车最优变道, 可确保变道过程中不与目标车道汽车发生碰撞, 并兼顾变道效率和乘员舒适性。     

预瞄信息空气悬架汽车在加速/制动工况下的LQG控制

建立了基于空气悬架的1/2车辆加速/制动系统模型,通过轴距预瞄在后轮处提前预测路面不平度;设计了基于轴距预瞄控制算法的加速/制动最优控制器;进行了白噪声仿真分析。仿真结果表明:与被动空气悬架加速/制动系统相比,基于轴距预瞄控制的主动空气悬架加速/制动系统能有效降低车辆振动。与最优控制空气悬架加速/制动系统相比,质心加速度和后轮对应处的车身加速度、悬架动行程、轮胎动载均有显著减小,较好的改善了车辆在加速/制动时的平顺性和操纵稳定性。     

A stability analysis of tandem offloading systems at sea

In this article, we analyze the linear stability of tandem offloading systems in wind, current, and waves. The wind and current forces are evaluated with the help of published experimental data, while the hydrodynamic coefficients and wave drift forces are rigorously estimated by using a three-dimensional singularity distribution method based on potential theory. The bow hawser and mooring lines are described quasistatically by elastic catenary equations. In order to examine the linear static and dynamic stability of the system, the equations for surge, sway, and yaw are linearized. The effect of design parameters such as turret position, mooring stiffness, and hawser length and stiffness on stability is investigated based on linearized model. The stability analysis clarifies the mechanism of the limit cycle for tandem offloading systems, which is known as fishtailing motion. The theoretical results of the shape and amplitude of the limit cycle are found to be in good agreement with those of simulations and experiments.     

驾驶员方向控制模型及在汽车智能驾驶研究中的应用

分析了驾驶员开车行为特性，利用模糊决策理论介绍了汽车预期行驶轨迹驾驶员模糊决策模型，并结合驾驶员预瞄最优曲率模型建立了一个新的驾驶员方向控制模型，同时也论述了该驾驶员方向控制模型在汽车智能驾驶研究中的应用。仿真结果表明所提出的模型可以描述驾驶员对汽车行驶方向的控制行为，并为汽车智能驾驶的研究提供了一条可行途径。     

Robust <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> preview control of an active suspension system with norm-bounded uncertainties

A robust H _∞ preview control is investigated for an active suspension system with look-ahead sensors. The uncertain system is described by a state-space model with linear nominal parts and additional nonlinear time-varying norm-bounded uncertainties. Proof of robust stability and a feedback-type robust H _∞ preview controller are derived by augmenting the dynamics of the original system and previewed road input. As, however, the augmented previewed road input gives the system a much larger dimension than the original system, much more computation time is required for solving of Riccati equations. To resolve this problem, a decomposed robust H _∞ preview controller is proposed. Robust stability and performance variations for system uncertainties are shown using a numerical example of a quarter-car model.     

融合预瞄与势场栅格法的紧急避撞驾驶人模型

紧急避障工况下的驾驶人操作具有响应快且动作幅值较大的特点,传统预瞄驾驶人模型已不能适应紧急避障工况的需求,故考虑实际避撞场景开发相应的驾驶人模型就显得尤为必要。针对此种状况,基于驾驶模拟器,结合紧急避撞工况实际驾驶人操纵数据,提出了一种融合预瞄与势场栅格法的紧急避撞驾驶人模型。首先针对紧急避撞工况下车辆运动特点,建立车辆横、纵向耦合非线性动力学模型,并给出其状态空间方程描述;其次,离线仿真分析紧急避撞系统特征,并结合线性二次型最优控制,建立最优曲率预瞄+跟踪误差反馈驾驶人模型;再者,基于紧急避撞工况下真实驾驶人经验转向行为数据,开发基于势场栅格法的驾驶人模型,为进一步提高驾驶人模型对避障行驶工况的适应性,将基于势场栅格法的驾驶人模型与最优曲率预瞄+跟踪误差反馈驾驶人模型进行融合,并基于Sigmoid函数实现两者输出的权重分配;最后,针对所提出的融合预瞄与势场栅格法的驾驶人模型,开展基于避撞台架的驾驶人在环仿真试验以及实车试验。研究结果表明：在紧急避撞工况下,对比最优曲率预瞄+跟踪误差反馈驾驶人模型,融合预瞄与势场栅格法的驾驶人模型输出的转向动作与实际驾驶人行为较为接近,可在保证避障安全性的前提下,兼顾避障路径跟踪精度与车辆行驶的稳定性。     

基于前馈补偿的路网规划方法

交通需求与交通供给之间的正反馈效应，使得路网规划方案难以适应交通需求的变化。在研究交通需求与路网容量关系的基础上，提出了采用前馈的手段，把交通需求的变化预载到规划模型中，规划模型是以建设成本、建成后的运营成本和未满足的交通需求所造成的机会损失成本之和的年平均值最小为目标，并让总成本具有时间性来克服规划方案与未来实际情况之间的偏差，达到对当前的规划工作采取前馈控制，使规划方案兼顾未来的需求和规模上的控制，在一定程度上克服交通需求的不确定性。     

基于轴距预瞄的汽车半主动悬架控制及试验

为了研究轴距预瞄控制技术对半主动悬架系统性能的影响, 构建了基于轴距预瞄的1/2车辆半主动悬架综合模型, 结合神经网络和PID控制理论, 提出了单神经元自适应PID控制算法, 设计了轴距预瞄半主动悬架单神经元PID控制系统, 进行了仿真计算。为研究单神经元自适应PID控制策略的有效性及其控制系统的可靠性, 同时进行了基于轴距预瞄的实车道路试验。研究结果表明: 与被动悬架系统相比, 在车速为50km.h^-1时, 车身质心垂直加速度的峰值和标准差分别减少了20.91%和19.11%;车速为60km.h^-1时, 分别减少了24.42%和26.85%, 并且俯仰角加速度也有一定程度降低, 较好改善了车辆的行驶平顺性。     

Optimal control to modelling motorcycle rider steering: local versus global coordinate systems in rider preview

The response of a motorcycle is heavily dependent on the rider’s control actions, and consequently a means of replicating the rider’s behaviour provides an important extension to motorcycle dynamics. The primary objective here is to develop effective path-following simulations and to understand how riders control motorcycles. Optimal control theory is applied to the tracking of roadway by a motorcycle, using a non-linear motorcycle model operating in free control by steering torque input. A path-following controller with road preview is designed by minimising tracking errors and control effort. Tight controls with high weightings on performance and loose controls with high weightings on control power are defined. Special attention is paid to the modelling of multipoint preview in local and global coordinate systems. The controller model is simulated over a standard single lane-change manoeuvre. It is argued that the local coordinates point of view is more representative of the way that a human rider operates and interprets information. The simulations suggest that for accurate path following, using optimal control, the problem must be solved by the local coordinates approach in order to achieve accurate results with short preview horizons. Furthermore, some weaknesses of the optimal control approach are highlighted here.     

Using the lead vehicle as preview sensor in convoy vehicle active suspension control

Both ride quality and roadholding of actively suspended vehicles can be improved by sensing the road ahead of the vehicle and using this information in a preview controller. Previous applications have used look-ahead sensors mounted on the front bumper to measure terrain beneath. Such sensors are vulnerable, potentially confused by water, snow, or other soft obstacles and offer a fixed preview time. For convoy vehicle applications, this paper proposes using the overall response of the preceding vehicle(s) to generate preview controller information for follower vehicles. A robust observer is used to estimate the states of a quarter-car vehicle model, from which road profile is estimated and passed on to the follower vehicle(s) to generate a preview function. The preview-active suspension, implemented in discrete time using a shift register approach to improve simulation time, reduces sprung mass acceleration and dynamic tyre deflection peaks by more than 50% and 40%, respectively. Terrain can change from one vehicle to the next if a loose obstacle is dislodged, or if the vehicle paths are sufficiently different so that one vehicle misses a discrete road event. The resulting spurious preview information can give suspension performance worse than that of a passive or conventional active system. In this paper, each vehicle can effectively estimate the road profile based on its own state trajectory. By comparing its own road estimate with the preview information, preview errors can be detected and suspension control quickly switched from preview to conventional active control to preserve performance improvements compared to passive suspensions.