基于交互车辆轨迹预测的自动驾驶车辆轨迹规划

针对城市道路等复杂行车场景,提出了一种基于交互车辆轨迹预测的自动驾驶车辆轨迹规划方法,将高维度的轨迹规划解耦为低维度的路径规划和速度规划;首先,采用五次多项式曲线和碰撞剩余时间规划车辆行驶路径;其次,在社会生成对抗网络Social-GAN的基础上结合车辆空间影响和注意力机制对交互车辆进行轨迹预测;然后,结合主车规划路径、交互车辆预测轨迹及碰撞判定模型得到主车S-T图,采用动态规划和数值优化方法求解S-T图,从而得到满足车辆动力学约束的安全、舒适最优速度曲线;最后,搭建PreScan-CarSim-Matlab&Simulink-Python联合仿真模型进行实验验证。仿真结果表明,提出的轨迹规划方法能够在对交互车辆有效避撞的前提下,保证车辆行驶的舒适性和高效性。     

城市交叉口车辆速度与交通信号协同优化控制

为了降低城市交通中的行车延误与燃油消耗,针对人类驾驶车辆与自动驾驶车辆混合交通环境,提出一种基于交通信息物理系统(TCPS)的车辆速度与交通信号协同优化控制方法.首先,综合考虑路口交通信号、人类驾驶车辆、自动驾驶车辆三者之间的相互影响,设计一种适用于自动驾驶车辆与人类驾驶车辆混合组队特性的过路口速度规划模型;其次,针对车辆速度规划单一应用时的局限性,即无法减少车辆路口通行延误且易出现无解情况,提出一种双目标协同优化模型,能够综合考虑车辆速度规划与路口交通信号控制,同时降低车辆燃油消耗与路口平均延误.由于双目标优化问题求解的复杂性,设计一种遗传算法-粒子群算法混合求解策略.基于SUMO的仿真实验验证了所提出方法的有效性.     

过饱和交通状态下的停车延误协调控制模型

选取整个过饱和状态持续作用时间作为研究时段,利用交叉口进口道的车辆到达–驶离图,根据行驶车队头车到达下游交叉口进口道的不同时刻,分别针对行驶车队在一个以红灯启亮为起始的信号周期之内到达和跨越一个以红灯启亮为起始的信号周期到达两种情况,对过饱和交通状态下行驶车队通过协调信号控制交叉口的停车延误进行了分析研究,建立了一套过饱和交通状态下的停车延误协调控制模型,得到了滞留车辆数、停车次数、延误时间等性能指标与相邻交叉口相对相位差、公共信号周期等协调控制变量之间的相关关系,并通过交通仿真对控制模型进行了分析验证,为过饱和交通状态下的协调控制技术方法研究提供了相关理论依据.     

复杂车路环境下自动驾驶车辆换道仿真研究

自动驾驶车辆换道决策的算法设计对确保自动驾驶车辆的安全平稳运行至关重要.在现有研究基础上,综合考虑了换道车辆与原车道、目标车道前后多辆车的冲突关系,通过引入车辆侵略系数建立复杂路况下的多人动态博弈模型,以寻找自动驾驶车辆在复杂车路环境下的换道决策以及轨迹线规划的最佳策略.随后,通过NGSIM(Next Generation Simulation)数据探究车辆行驶特性,得到车辆侵略系数的准确分布,搭建仿真环境,给出本模型下自动驾驶车辆在不同路况中的策略选择以及对应的轨迹线示意,并将结果与其它模型求得结果进行比较.根据仿真结果,上述算法有效地完成了自动驾驶车辆在复杂车路环境下换道的关键技术问题,可为自动驾驶车辆的换道决策提供一定的技术指导.     

交叉口混合交通流微观控制模型

为构建智能网联汽车(CAV)和有人驾驶汽车(HDV)混合通行情况下的交叉口通行机制与控制方法, 本文提出CAV专用道条件下交叉口协同通行模型. 首先, 设计CAV专用道条件下的交叉口布置, 对交叉口进行网格化处理,将CAV通行时隙和HDV绿灯相位对交叉口某部分网格某时段的占用统一到交叉口时空资源描述框架下; 其次, 建立兼顾CAV与HDV的交叉口时空网格资源分配模型, 构建自适应信号灯控制算法和CAV轨迹规划算法; 再次, 以车辆最小延误为目标进行自适应信号灯配时优化和CAV轨迹优化; 最后, 选取广州某典型交叉口建立仿真实验对所提方法的有效性进行了验证.     

基于改进蚁群优化算法的自动驾驶多车协同运动规划

当前面向多辆自动驾驶汽车的协同运动规划方法能有效保证运行车辆与障碍物及其他车辆之间避免发生碰撞并保持安全距离,但车辆间的在线协同与规划能力仍有待提升。为实现多辆自动驾驶汽车在运动过程中的协同控制,提出一种基于改进蚁群优化算法的多车在线协同规划方法。以空间协同与轨迹代价为优化目标,构造多目标优化函数,确保了多车行驶过程中的协同安全性与轨迹平滑性。将多目标优化函数引入蚁群优化算法的信息素更新过程中,根据自动驾驶车辆数量产生多个种群,使得种群之间相互独立的同时为每辆自动驾驶汽车规划可行路线。最终对蚁群优化算法中的挥发因子进行自适应调整,提升了算法全局搜索能力及收敛速度。实验结果表明,该方法能使多辆自动驾驶汽车在运动过程中保持协同控制并规划出无碰撞路线,相比于基于人工势场和模型预测的协同驾驶方法在复杂道路场景下车辆间的协同效果更好且适应性更强。     

混行交叉口下智能车辆驾驶轨迹控制方法

考虑车辆之间的相互影响和交通环境的不确定性，且混行交叉口的路况较为复杂，导致驾驶轨迹跟踪控制误差较大。为此提出混行交叉口下智能车辆驾驶轨迹跟踪控制方法。构建智能车辆驾驶模型，在IDM场景计算车辆加速度，确定车速和安全距离。利用线性时变模型将智能车辆驾驶轨迹线性时变表达，并建立轨迹预测方程，求出预测时域状态量和输出量；构建驾驶轨迹限制条件，引入前轮转角的控制量、控制增量与重心偏移角度，通过构建目标函数，计算实际控制量，通过设定理想时间，获取时域内外纵速度，结合欧拉积分完成驾驶轨迹跟踪控制。仿真结果表明，所提方法驾驶轨迹跟踪控制误差小，保证智能车辆安全稳定运行。     

无人车稳定性DP优化协调控制方法仿真

为了提高无人车驾驶的稳定性，提出基于DP优化的无人车稳定性协调控制方法。设计无人车动力学模型，确保无人车自身稳定性的同时，实现车辆行驶过程路径的快速与高精度跟踪。利用五次多项式方程描述无人车的换道轨迹曲线，建立换道约束条件，在满足约束条件的前提下，获得最优换道路线。采用DP优化算法解决车辆行驶过程中频繁换挡的问题，实现无人车稳定性协调控制，提高无人车行驶过程中的稳定性和安全性。实验结果表明，所提方法可以提高无人车路径跟踪精度，保证车辆驾驶的稳定性和安全性。     

基于模型预测的自动导引车区间轨迹跟踪控制

针对自动导引车(AGV)轨迹跟踪问题,在确定其可行驶区域的基础上,考虑自动导引车的大小和形状,本文设计了一种基于模型预测控制理论的轨迹跟踪控制方法.首先,将车辆运动学模型进行线性化处理,得到车辆动力学线性模型;其次,运用模型预测控制方法,利用预测路径与期望路径之间的误差,通过优化得到使性能指标最优的控制序列;最后,在MATLAB软件上对轨迹跟踪控制器进行仿真.实验结果表明,AGV可以稳定地跟踪参考轨迹,且距离偏差和角度偏差都在给定的可行范围内,证明了提出的基于模型预测控制的轨迹跟踪算法具有良好的跟踪性能.     

时空图注意力网络在交叉口车辆轨迹预测的应用

随着人工智能和大数据技术的快速发展,以深度学习为代表的自动驾驶轨迹预测是未来的热点研究方向.在混合交通场景下,如何准确地预测机动车与非机动车的轨迹,是实现自动驾驶技术中安全行驶和高效轨迹规划等问题的前提.针对交叉路口中不同运动对象之间发生交互时的轨迹预测问题,提出了基于图注意力网络的建模方案.所采用的模型结合了时间与空间上研究对象之间的相互作用,对机动车与非机动车的未来轨迹做出了更准确的预测,可应用于自动驾驶的轨迹规划方案,确保在复杂交通场景下,机动车与非机动车能够安全且高效地通过交叉路口.该模型在简单交互情况下,可取得较小的轨迹平均位移误差和最终位移误差,而在复杂交互情况下,可提供更为合理的规划路径.     

Vehicle Motion Prediction at Intersections Based on the Turning Intention and Prior Trajectories Model

Intersections are quite important and complex traffic scenarios, where the future motion of surrounding vehicles is an indispensable reference factor for the decision-making or path planning of autonomous vehicles. Considering that the motion trajectory of a vehicle at an intersection partly obeys the statistical law of historical data once its driving intention is determined, this paper proposes a long short-term memory based (LSTM-based) framework that combines intention prediction and trajectory prediction together. First, we build an intersection prior trajectories model (IPTM) by clustering and statistically analyzing a large number of prior traffic flow trajectories. The prior trajectories model with fitted probabilistic density is used to approximate the distribution of the predicted trajectory, and also serves as a reference for credibility evaluation. Second, we conduct the intention prediction through another LSTM model and regard it as a crucial cue for a trajectory forecast at the early stage. Furthermore, the predicted intention is also a key that is associated with the prior trajectories model. The proposed framework is validated on two publically released datasets, next generation simulation (NGSIM) and INTERACTION. Compared with other prediction methods, our framework is able to sample a trajectory from the estimated distribution, with its accuracy improved by about 20%. Finally, the credibility evaluation, which is based on the prior trajectories model, makes the framework more practical in the real-world applications.      

自主车辆安全系数估计与T形路口避碰规划

针对自主车辆T形路口协作问题,通过测量车辆速度和预碰点距离,提出安全系数估计方法,结合人工势场基本思想,实现车辆路口避碰,提高路口协作效率.首先以计算得到的安全系数为依据,评价驶入T形路口两辆自主车各自的安全程度,并利用人工势场产生的推拉作用估计协作自主车辆的期望控制力和速度.然后将估计的期望车速与反馈的实际车速形成偏差,利用增量型数字PI控制器实现自主车纵向车速的准确控制.最后以一定的策略完成两辆自主车的并线协作.仿真结果验证了基于安全系数估计的自主车辆T形路口协作避碰的可行性与有效性.     

不确定性车辆路口的轨迹预测

在城市道路中,实时、准确、可靠地对移动车辆进行轨迹预测具有极高的应用价值,不仅可以提供准确的基于位置的服务,而且可以帮助过往车辆预知前方的交通状况。目前,移动车辆的轨迹预测方法主要基于历史轨迹的欧氏空间进行,并未考虑在受限路网中采用不确定性历史数据的车辆轨迹预测。针对这一问题,提出一种补全路径的基于马尔科夫链的轨迹预测方法,其优势在于:重新定义了补全路径算法,弥补了不确定性历史数据的不完整性,利用马尔科夫链低时间复杂度、高预测准确度的优势实现预测,避免了因频繁模式挖掘带来的查询时间过长而影响预测效率以及存在多余噪声影响轨迹预测准确率的问题。通过真实数据和实验分析表明:在参数设置相同的情况下,该方法比挖掘频繁轨迹模式算法的预测准确率平均提高了18.8%,预测时间平均缩减了80.4%。因此,该方法对于车辆路口的轨迹预测具有较高的预测准确率,并且能预测一系列的车辆未来轨迹。     

Receding-Horizon Trajectory Planning for Under-Actuated Autonomous Vehicles Based on Collaborative Neurodynamic Optimization

This paper addresses a major issue in planning the trajectories of under-actuated autonomous vehicles based on neurodynamic optimization. A receding-horizon vehicle trajectory planning task is formulated as a sequential global optimization problem with weighted quadratic navigation functions and obstacle avoidance constraints based on given vehicle goal configurations. The feasibility of the formulated optimization problem is guaranteed under derived conditions. The optimization problem is sequentially solved via collaborative neurodynamic optimization in a neurodynamics-driven trajectory planning method/procedure. Simulation results with under-actuated unmanned wheeled vehicles and autonomous surface vehicles are elaborated to substantiate the efficacy of the neurodynamics-driven trajectory planning method.      

Fuzzy logic steering control of autonomous vehicles inside roundabouts

The expansion of roads and the development of new road infrastructures have increased in recent years, linked to the population growing in large cities. In the last two decades, roundabouts have largely replaced traditional intersections in many countries. They have the advantage of allowing drivers continuous flow when traffic is clear, without the usual delay caused by traffic lights. Although roundabouts with and without traffic-signal control have been widely used and considered in the literature, driverless control on roundabouts has not been studied in depth yet. The behavior of autonomous vehicles in roundabouts can be divided into three stages: entrance, inside, and exit. The first and last may be handled as an extension of intersections. However, autonomous driving on the roundabout requires special attention. In this paper, the design and implementation of a fuzzy logic system for the steering control of autonomous vehicles inside the roundabout is proposed. Cascade architecture for lateral control and parametric trajectory generation are used. Fuzzy control has proved to be easy to define using expert knowledge. Experiments with a real prototype have been carried out, taking into account different speed profiles and lane change maneuvers inside the roundabout, with very satisfactory results.     

Rough Terrain Autonomous Mobility—Part 2: An Active Vision, Predictive Control Approach

Off-road autonomous navigation is one of the most difficult automation challenges from the point of view of constraints on mobility, speed of motion, lack of environmental structure, density of hazards, and typical lack of prior information. This paper describes an autonomous navigation software system for outdoor vehicles which includes perception, mapping, obstacle detection and avoidance, and goal seeking. It has been used on several vehicle testbeds including autonomous HMMWV's and planetary rover prototypes. To date, it has achieved speeds of 15 km/hr and excursions of 15 km.We introduce algorithms for optimal processing and computational stabilization of range imagery for terrain mapping purposes. We formulate the problem of trajectory generation as one of predictive control searching trajectories expressed in command space. We also formulate the problem of goal arbitration in local autonomous mobility as an optimal control problem. We emphasize the modeling of vehicles in state space form. The resulting high fidelity models stabilize coordinated control of a high speed vehicle for both obstacle avoidance and goal seeking purposes. An intermediate predictive control layer is introduced between the typical high-level strategic or artificial intelligence layer and the typical low-level servo control layer. This layer incorporates some deliberation, and some environmental mapping as do deliberative AI planners, yet it also emphasizes the real-time aspects of the problem as do minimalist reactive architectures.