【作者】 向先波；

【导师】 黄心汉；

【作者基本信息】 华中科技大学 ， 控制理论与控制工程， 2010， 博士

【摘要】 21世纪是海洋的世纪,日益增长的海洋开发需求,以及自主式水下机器人(Autonomous Underwater Vehicle, AUV)技术的快速发展,使得欠驱动水下机器人已成为AUV家族的重要成员和海洋探测开发的重要工具。欠驱动水下机器人属于二阶非完整性系统,且具有本质上的强非线性,其运动控制问题非常具有挑战性。因此,二阶非完整性欠驱动水下机器人的非线性运动控制研究具有重要的理论价值和实用价值,已经成为水下机器人控制领域的热点问题。本文深入分析了国内外关于二阶非完整性水下机器人运动控制方面的研究成果,并总结了所存在的问题,在此基础上完成了二阶非完整性水下机器人的路径跟踪控制,并对基于路径跟踪的机器人编队协调控制进行了研究。主要研究内容如下：首先,简要介绍了非完整性系统,比较了路径跟踪与轨迹跟踪各自的特点,选择了建立路径跟踪误差动力学的合适方案。以一阶非完整性移动机器人为研究对象,深入探讨机器人路径跟踪控制的设计方法,在Serret-Frenet移动坐标系下,提出基于虚拟参考目标点“协作式”路径跟踪的控制策略,完成具有“时空解耦”特性的控制器设计。其次,建立水下机器人运动学、动力学模型,基于一阶与二阶非完整性系统运动控制的部分相似性,借鉴一阶非完整性机器人路径跟踪的控制策略,实现二阶非完整性水下机器人的三自由度全状态欠驱动路径跟踪控制器,并解除了普遍存在的角速度持续激励的路径跟踪限制条件。通过引入建立在Serret-Frenet移动坐标系且可随路径曲率自适应变化的视线角,将其由传统的船舶直线路径跟踪,扩展到水下机器人曲线参考路径的跟踪控制。采用“视线角导航”和“位置”分步设计,简化了路径跟踪控制律。利用Lyapunov直接法和反演设计技术,将运动学路径跟踪控制器反演至动力学。在此基础上,给出了欠驱动与全驱动水下机器人侧漂角及其加速度的计算处理方法,得到完善的AUV路径跟踪控制解决方案,从而保证了高精度的路径跟踪控制。在海流扰动情况下,基于输入-状态稳定性分析和直接抵抗海流这两种方法,完成路径跟踪控制器设计。再次,在水下声通信受到通信距离、通信带宽等限制条件下,将二阶非完整性AUV路径跟踪与刚性编队协调有机结合起来,使得基于路径跟踪的AUV编队协调控制更具可行性和实用价值。采用编队参考点与虚拟结构相结合的方法,设定编队路径并增加了编队结构的灵活性。同时,将“时空解耦”的路径跟踪策略嵌入到多AUV编队协调控制设计之中,利用单个机器人的路径跟踪控制器完成三自由度空间位姿跟踪任务,通过对多AUV速度的整体协调控制,实现编队队形。基于主从式控制结构,设计了单源、单向通信机制下的编队协调控制律；通过引入代数图理论知识,得到多机器人复杂网络通信拓扑的数学表达,进而基于无领航者的分散式控制结构,完成AUV编队协调控制器的设计,且考虑了机器人速度饱和的限制。对于存在水下通信时延和可变通信拓扑的情况,提出了基于平均一致连接性切换网络的时延协调控制律。另外,基于水下声纳导航信息,通过引入修正的AUV视线角,利用输入-状态稳定性原理,完成水下机器人编队协调下的路径跟踪及同时避障、避碰的控制设计。最后,总结了本文的主要研究成果和创新点,并对二阶非完整性水下机器人路径跟踪及编队协调控制的进一步研究工作进行了展望。更多还原

【Abstract】 In the 21th Century, oceans will play a key role in the human society. With the emerging requirement on ocean exploration and exploitation, and the rapid development of Autonomous Underwater Vehicles (AUV), underactuated AUV becomes an important type of underwater vehicles as a significant tool for ocean engineering. Underactuaed AUV suffers from the second-order nonholonomic constraints, has strong nonlinear characteristics. Hence, research on the motion control for underactuaed AUV, is very interesting and valuable from both practical and therotical point of view.In this dissertation, the state of art of motion control on the second-order nonholonomic AUV has been reviewed, and the exsisting problem is posed. After that, the path following control of underactuated AUV is choosen as the core topic of control design, and the path following based coordinated formation control is also proposed later. The contents of the paper are as follows.Firstly, the nonholonomic system is introduced, the characteristics of path following and trajectory tracking are compared, and the suitable method to build the tracking error dynamics is chosen. The strategy of path following control is carefully analyzed based on the first-order nonholonomic mobile robot. In the Serret-Frenet frame, the virtual reference point on the path is highlighted which can collaborately help the convergence of robot towarding the path. With the extra control freedom from virtual point, the time-space decoupling path following controller rises up.Secondly, the modeling of AUV kinematics and dynamics is analyzed. Based on the similarity between the first and second order nonholonomic system, standing on the useful control strategy for the first-order nonholonomic mobile robot, the similar control design is proposed for the second-order nonholonomic AUV, relieving the limation of angular persistent excitation on some other controllers for path following. By introducing the line-of-sight (LOS) angle adapting with the curvature of curves to the AUV, which is originally used for straight line tracking of ships, and using separated LOS navigation and position control, the path following controller is simplified. Based on Lyapunov design and backstepping technique, the kinematic controller is extended to the dynamic controller. Moreover, the acceleration of AUV side-slip angle is deliberately tackled, such that the complete path following controller is obtained, and the high precision path following is guaranteed. Under the disturbance of ocean current, the principle of input-state-stability and the idea of directly rejecting disturbance are used to design the new path following controllers.Thirdly, under the constraints of limited communication distance and bandwidth of underwater acoustic communication, path following and rigid formation control is integrated, such that the coordinated formation of AUVs based on path following control is more feasible and valuable in practice. Using the methods of formation reference point and virtual structure, the paths are ready for coordinated AUVs with control flexibility. The time-space decoupling characteristic is also embodied in the coordinated controller design, which means each vehicle employs individual path following control to reach the desired spatial position and orientation, and the coordinated controller adjusting speeds of multiple AUVs can assure the formation structure. Later, two types of controller, i.e., leader-follower based controller and decentralized controller are proposed, to realize the path following based formation control of multiple AUVs. The single source and uni-direction of acoustic communication renders leader-follower structure, and the algebraic graph theory is used to build complex underwater communication network, which is helpful to design the decentralized controller. Moreover, the speed saturation of underwater vehicle has been considered in the multi-vehicle controller design. The revised controller is also designed to deal with the varied communication topology and the time-delay in the acoustic communication network, in case of the communication graph is uniformly connected in mean. After that, based on the sensor information supported by the underwater looking forward sonar, the trimmed line-of-sight angle is introduced and the principle of input-state-stability is used to propose the novel controller, in order to achieve the simultaneous path following and obstacle avoidance/collision free for multiple AUVs under formation control.Finally, the research work in the dissertation is concluded, and the innovative idea is highlighted. The future work on path following and coordinated control for the second-order nonholonomic AUV is also indicated.更多还原