Real-time OHT Dispatching Mechanism for the Interbay Automated Material Handling System with Shortcuts and Bypasses

As a key to improve the performance of the interbay automated material handling system (AMHS) in 300 mm semiconductor wafer fabrication system, the real-time overhead hoist transport (OHT) dispatching problem has received much attention. This problem is first formulated as a special form of assignment problem and it is proved that more than one solution will be obtained by Hungarian algorithm simultaneously. Through proposing and strictly proving two propositions related to the characteristics of these solutions, a modified Hungarian algorithm is designed to distinguish these solutions. Finally, a new real-time OHT dispatching method is carefully designed by implementing the solution obtained by the modified Hungarian algorithm. The experimental results of discrete event simulations show that, compared with conventional Hungarian algorithm dispatching method, the proposed dispatching method that chooses the solution with the maximum variance respectively reduces on average 4 s of the average waiting time and average lead time of wafer lots, and its performance is rather stable in multiple different scenarios of the interbay AMHS with different quantities of shortcuts. This research provides an efficient real-time OHT dispatching mechanism for the interbay AMHS with shortcuts and bypasses.     

Coordinated path following of multiple underacutated marine surface vehicles along one curve

This paper investigates the coordinated path following problem for a fleet of underactuated marine surface vehicles (MSVs) along one curve. The dedicated control design is divided into two tasks. One is to steer individual underactuated MSV to track the given spatial path, and the other is to force the vehicles dispersed on a parameterized path subject to the constraints of a communication network. Specifically, a robust individual path following controller is developed based on a line-of-sight (LOS) guidance law and a reduced-order extended state observer (ESO). The vehicle sideslip angle due to environmental disturbances can be exactly identified. Then, the vehicle coordination is achieved by a path variable containment approach, under which the path variables are evenly dispersed between two virtual leaders. Another reduced-order ESO is developed to identify the composite disturbance related to the speed of virtual leaders and neighboring vehicles. The proposed coordination design is distributed since the reference speed does not need to be known by all vehicles as a priori. The input-to-state stability of the closed-loop network system is established via cascade theory. Simulation results demonstrate the effectiveness of the proposed design method.     

基于改进 A * 算法的四向穿梭车路径规划

针对传统四向穿梭车系统路径规划易出现路径交叉死锁问题,提出一种改进 A * 算法的路径规划算法。参考多辆穿梭车路径的路径交叉长度、路径冲突车辆总数对路径搜索的影响,使得多辆穿梭车路径分布均匀,减少车辆路径的点边冲突,降低实时路径检测中避让策略的复杂度,提高系统的稳定性与效率。栅格地图环境中,将该算法应用于复杂环境中的四向穿梭车路径规划,仿真结果表明,该算法在路径规划中是可行和有效的。     

基于最优控制的汽车操纵逆动力学的研究

提出了一种基于最优控制理论的汽车操纵逆动力学研究方法，用于识别不同汽车跟踪同一期望路径的方向盘转角输入。以驾驶员对汽车施加的方向盘转角输入为控制变量，以精确跟踪期望路径为控制目标，将汽车操纵逆动力学问题转化为最优控制问题。利用直接配置方法将最优控制问题转化为非线性规划问题，运用序列二次规划方法求解。仿真结果表明：该方法能够使汽车很好地跟踪所期望的路径，且可以比较跟踪同一路径的不同汽车的操纵性能。     

Extended model predictive control scheme for smooth path following of autonomous vehicles

This paper presents an extended model predictive control (MPC) scheme for implementing optimal path following of autonomous vehicles, which has multiple constraints and an integrated model of vehicle and road dynamics. Road curvature and inclination factors are used in the construction of the vehicle dynamic model to describe its lateral and roll dynamics accurately. Sideslip, rollover, and vehicle envelopes are used as multiple constraints in the MPC controller formulation. Then, an extended MPC method solved by differential evolution optimization algorithm is proposed to realize optimal smooth path following based on driving path features. Finally, simulation and real experiments are carried out to evaluate the feasibility and the effectiveness of the extended MPC scheme. Results indicate that the proposed method can obtain the smooth transition to follow the optimal drivable path and satisfy the lateral dynamic stability and environmental constraints, which can improve the path following quality for better ride comfort and road availability of autonomous vehicles.     

动力模块车组的运动建模与规划

大型动力平板车及其动力模块车组是重载超大型设备与物件运输的核心装备,具有轮组数量多、轮组与转向盘采用数字连接、各轮组独立转向驱动和控制等特点,合理的轮组运动建模与规划是保证其正常高效作业的基础。根据工程应用实际需求并保证计算的实时性要求,提出典型和一般两大类运动模式。典型运动模式即绕某一固定点旋转,采用梯形转向解析法建立各轮组转角模型,并得出最小转弯半径;一般运动模式即沿任意曲线路径行进,通过分解转化为典型运动模式,再相应解算。多车并车为动力模块车组时,基于模块化思想,通过全局向单车坐标系的转换,将车组运动转化成各单车运动,再由各单车解算轮组转角,实现动力模块车组的分布式实时计算。数值仿真验证了所提方法的可行性。     

现代物流系统中基于路径的RFID立方体构建方法

为有效地存储和管理海量数据,提出了一种基于路径的射频识别技术数据立方体构建方法。该方法不受射频识别技术系统的物理分布影响,只与路径数据库的规模有关;在最小兴趣层和观察层之间,选择物化某些立方体单元,以保证能够快速构建立方体结构和较快响应系统不同用户的路径查询。理论分析和实验结果表明了该方法的有效性。     

Intelligent vehicle electrical power supply system with central coordinated protection

The current research of vehicle electrical power supply system mainly focuses on electric vehicles (EV) and hybrid electric vehicles (HEV). The vehicle electrical power supply system used in traditional fuel vehicles is rather simple and imperfect;electrical/electronic devices (EEDs) applied in vehicles are usually directly connected with the vehicle’s battery. With increasing numbers of EEDs being applied in traditional fuel vehicles, vehicle electrical power supply systems should be optimized and improved so that they can work more safely and more effectively. In this paper, a new vehicle electrical power supply system for traditional fuel vehicles, which accounts for all electrical/electronic devices and complex work conditions, is proposed based on a smart electrical/electronic device (SEED) system. Working as an independent intelligent electrical power supply network, the proposed system is isolated from the electrical control module and communication network, and access to the vehicle system is made through a bus interface. This results in a clean controller power supply with no electromagnetic interference. A new practical battery state of charge (SoC) estimation method is also proposed to achieve more accurate SoC estimation for lead-acid batteries in traditional fuel vehicles so that the intelligent power system can monitor the status of the battery for an over-current state in each power channel. Optimized protection methods are also used to ensure power supply safety. Experiments and tests on a traditional fuel vehicle are performed, and the results reveal that the battery SoC is calculated quickly and sufficiently accurately for battery over-discharge protection. Over-current protection is achieved, and the entire vehicle’s power utilization is optimized. For traditional fuel vehicles, the proposed vehicle electrical power supply system is comprehensive and has a unified system architecture, enhancing system reliability and security.     

Real time traversability analysis to enhance rough terrain navigation for an 6 × 6 autonomous vehicle

An autonomous vehicle should be driven at a velocity that allows it to feasibly track a predetermined path. For autonomous vehicles that require high velocity navigation over rough terrain, the driving velocity should be calculated in real time and maximized without exceeding any safety limits. In order to compute the driving velocity in real time, several factors including path curvature, terrain characteristics, vehicle dynamics, and interaction between vehicle and terrain need to be taken into account, along with real time constraints. In this study, a method based on real time traversability analysis is proposed to determine the maximum permissible velocity at which an autonomous vehicle can traverse rough terrain with guaranteed stability. Simulations validated the proposed method for a 6 × 6 autonomous vehicle with articulated suspension traveling over rough terrain.     

基于Matlab与三维空间几何变换的车辆动态包络线获取方法研究

为了更加便捷地获取车辆的动态包络线,研究出一种基于Matlab软件与三维空间几何变换理论来获取车辆动态包络线的新方法。以某地铁车辆为研究对象,对地铁车辆进行线路实测,获得车辆的动态偏移量,结合CJJ96—2003《地铁限界标准》计算方法得到车辆的静态偏移量,基于三维空间几何变换理论推导控制点实时坐标,利用Matlab软件仿真计算在实际线路上运行的地铁车辆动态轮廓,得到所有动态轮廓上控制点的坐标,并输出车辆的动态包络线。该研究方法,使得车辆动态包络线的获取更便捷,最终结果更切合实际,从而更加充分地利用限界的有效空间,也为车辆限界计算提供新思路。     

基于期望横摆角速度的视觉导航智能车辆横向控制

针对采用传统位置偏差控制方法的车道保持系统横向控制精度不高以及鲁棒性差等问题,提出一种跟踪期望横摆角速度的车辆横向控制方法。在车辆当前行驶位置和道路预瞄点之间实时规划逼近目标路径的虚拟路径,同时分析当前时刻车辆以无偏差形式沿此虚拟路径行驶时决定车辆行驶位置的横摆角速度及速度之间的关系。结合车辆道路相对位置及车身状态信息,设计期望横摆角速度生成器。基于7自由度非线性车辆动力学模型,设计滑模控制器跟踪期望横摆角速度,使得车辆稳定地跟踪目标路径。根据车道线宽度和边缘点数量统计进行边缘检测,能有效识别模糊车道边缘和抑制噪声,并通过对消失点的检测来有效去除非车道线的干扰。仿真及试验结果表明,与传统的位置偏差控制方法相比,期望横摆角速度法不仅能提高车辆横向控制的精确性且跟随偏差随车辆速度及道路曲率的变化波动范围小,具有很好的鲁棒性和自适应性。     

The evaluation of search range assignment in 300 mm automated material handling system (AMHS)

In the 300 mm AMHS with a connected loops layout, the vehicle can travel not just in one loop but all around the wide fab to execute tool-to-tool delivery. Determining how far the waiting FOUPs (WFs) or idle vehicles (IVs) should be considered before selecting a dispatching rule might make dispatching more efficient. A two-phase approach with simulation has been developed to assign the search range (SR) for studying this idea. The model of a simplified 300 mm AMHS was built using eM-Plant and Design Expert to design experiments and analyse the results. In phase I, the number of WF and IV in the system at the time of dispatching will affect the distance of the vehicle’s empty trip (DVemp). Further, the SR was assigned and evaluated based on the average and standard deviation of DVemp under different numbers of WF and IV in phase II. The results indicated that the SR significantly affects the performance, and a longer SR used in a light system is feasible; a shorter SR is applicable for a heavy system.     

融合动态能耗与路网信息的电动汽车充电路径规划策略

针对电动汽车续驶里程短的问题，以电动汽车为研究对象，基于“车路网”智能系统建立了道路拓扑模型、阻抗评价模型以及整车能耗模型，分别以电动汽车行驶时间最优、能耗最优和综合最优为目标，运用A*算法对电动汽车进行了充电路径规划。以福州市区交通为实例，采集了各路段主要行驶工况数据，将规划路段与行驶工况数据匹配用于车辆行驶时间和能耗的预测，并结合充电等待时间计算各目标阻抗成本。研究结果表明：所提出的充电路径规划策略能够根据驾驶员的不同需求分别规划出考虑时间、能耗以及综合最优的充电路径。     

基于模糊控制的汽车路径跟踪研究

汽车是一个非常复杂的非线性动力学系统,难以建立精确的数学模型,而模糊控制方法适用于难以建立精确数学模型的对象。将模糊控制理论引入汽车操纵逆动力学中,以汽车三自由度模型为研究对象,根据侧向偏差和偏差变化率设计了车辆的路径跟踪模糊控制器。对某车型跟踪给定双移线和蛇形路径行驶情况进行了仿真。结果表明,模糊控制方法可保证汽车准确地跟踪给定参考路径,可以作为车辆路径跟踪控制的一种有效控制方法。     

基于道路势场的车道偏离自动校正自适应控制

针对车道偏离自动校正控制中采用传统位置偏差控制方法路径跟踪精度不高以及实时性差等问题,提出了一种基于道路人工势场法的车辆路径跟踪方法,控制车辆能够实时保持沿着目标道路中心线行驶。该方法在车辆所处的环境道路上产生一个势场,该势场包含车辆与道路中心线的偏差信息及前方预瞄信息,对处在势场中的车辆具有阻碍其偏离车道中心线的势场力的作用。将势场产生的控制力加入车辆动力学模型中,实时控制车辆稳定地跟踪车道中心线。仿真及试验结果表明,所提方法比位置偏差法跟踪精度更高且跟踪误差随车辆速度变化波动范围小,具有较强的鲁棒性和实时性。     

智能汽车路径跟踪混合控制策略研究

针对传统单一控制算法无法有效协调智能汽车不同转向工况下横向控制性能要求的问题,根据智能汽车在高速和低速转向工况下呈现出的系统特性差异,设计了一种基于PID控制和模型预测控制的智能汽车路径跟踪混合控制策略。该控制策略在低速模式下采用PID控制,在高速模式下则采用模型预测控制,通过车辆速度确定路径跟踪控制模式,进而设计带稳定监督的控制模式切换机制,实现了横向控制系统的平滑切换。基于Carsim和MATLAB/Simulink仿真平台对所设计的智能汽车路径跟踪混合控制策略进行了仿真验证,在此基础上,进一步完成了实车试验。仿真和实车试验结果表明,所设计的混合控制策略能够保证智能汽车不同速度下的路径跟踪性能,具有较好的跟踪精度、实时性和车辆行驶稳定性。     

Dynamic dispatching for interbay material handling by using modified Hungarian algorithm and fuzzy-logic-based control

Semiconductor Wafer Fabrication System (SWFS) is one of the most complicate discrete processing systems in the world. As the wafer size grows from 200 to 300 mm and then to 450 mm in recent years, the interbay automated material handling system (AMHS) has been widely adopted. How to improve the overall efficiency of interbay material handling has therefore become a critical and urgent problem to be solved. However, the large-scale, dynamic and stochastic production environment significantly substantiates the complexity of the scheduling problem. Aiming to meet the demands of adaptive adjusting, efficient scheduling and multiple-objective optimization, a dynamic dispatching method based on modified Hungarian algorithm is proposed. The system parameters, including cassette due date, cassette waiting time, and system load are simultaneously considered, and furthermore the multi-parameters’ weight coefficients are adjusted dynamically by using the fuzzy-logic-based control. Discrete event simulation models are constructed with the eM-Plant software to evaluate the proposed approach. Experimental results show that the proposed dynamic dispatching method improves the system efficiency in terms of mean delivery time, mean waiting time and so on. Meanwhile, the proposed dispatching method has a better comprehensive performance such as the robustness compared to conventional vehicle dispatching approaches.     

Design of a stable controller for accurate path tracking of automated guided vehicles systems

This paper deals with the path tracking and stability of motion of automated guided vehicle systems and wheeled mobile robots. A two degree-of-freedom dynamic model is developed to represent the plane motion of the vehicle. This model along with the instantaneous posture errors (position and orientation errors) of the vehicle are used to formulate their path-tracking problem in state space format. Implementation of stability criterion and application of the actual physical limits of the pertinent parameters of the system are the strategies used to design the controller. It is shown that implementation of a control strategy based on the vehicles’ position and orientation errors gives satisfactory results in vehicles’ path tracking. The feasibility of the approach and the performance of the controlled system are demonstrated by using a prototype vehicle.     

基于信息融合的自动泊车系统车位线车位识别和决策规划

通过融合距离和视觉信息,提出了一种基于信息融合的车位线车位识别方法。首先利用摄像头采集车位角点在俯视图像中的坐标,然后采用基于逆透视变换的平面测距模型获取车身侧面距车位角点的侧向距离,最后融合超声波传感器和车辆里程信息建立车位线车位平面模型,确定了车辆后轴中心点坐标及相对初始偏航角,实现车位线车位的识别。根据识别出的车位信息进行路径规划并仿真分析,经过实车试验验证,该车位识别方法能够有效实现对车位线车位的识别,所规划路径合理、可行。     

毫米波雷达与视觉传感器信息融合的车辆跟踪

为提高车辆前向防碰撞预警系统对前方道路环境感知的准确性,提出一种毫米波雷达与视觉传感器信息融合的车辆跟踪方法。提出的剔除雷达干扰目标算法缩短了对干扰目标的处理时间;提出的对称检测算法可对雷达目标兴趣区域进行对称检测,减小雷达目标兴趣区域的横向位置误差;提出的KCF-KF组合滤波算法可提高跟踪车辆的精度。实车试验表明,该方法可有效跟踪车辆位置信息,像素坐标系下的X、Y坐标跟踪准确率分别超过97.34%与95.19%。