Design, analysis and experimental validation of a robust nonlinear path following controller for marine surface vessels

The problem of path following for marine surface vessels using the rudder angle is addressed in this paper. A four-degree-of-freedom nonlinear surface vessel model, together with the Serret-Frenet equations, is introduced to describe the ship dynamics and path following error dynamics. While similar models have been used and reported in the literature for path following control algorithm development, the novelty of the approach presented in this work lies in the following aspects. (a) The back-stepping nonlinear controller design is based on feedback dominance, instead of feedback linearization and nonlinearity cancelation; (b) additional design parameters are employed in the Lyapunov function that lead to simplification of the controller in the design procedure and normalization of different variables in the Lyapunov function to improve the controller performance; (c) relying on feedback dominance and the introduction of the additional parameters in the Lyapunov function, the resulting controller is almost linear, with very benign nonlinearities allowing for analysis and evaluation; and (d) the performance of the nonlinear controller, in terms of path following, is analyzed for robustness in the presence of model uncertainties. The simulation results are presented to verify and illustrate the analytic development and the effectiveness of the resulting control against rudder saturation and rate limits, and delays in the control execution, as well as measurement noises. Furthermore, the control design is validated by experimental results conducted in a tank using a model ship.     

舰载无人机着舰轨迹跟踪鲁棒控制器设计

为确保舰载无人机着舰阶段精确地跟踪下滑轨迹,并且在稳态性能基础上具有更好的瞬态性能,本文在新的等效误差模型的基础上提出了受限指令预设性能控制律设计方法.首先考虑了舵面受限和角速率受限等实际工程问题,引入受限指令滤波方法,然后综合考虑建模误差和外界扰动,引入了连续的双曲正切函数对饱和函数进行近似,并设计了自适应律对模型未知参数进行估计,最后引入了预设性能方法对着舰的瞬态性能进行了重点分析.通过理论推导和仿真验证,证明了本文提出的方法在复杂着舰环境下有较好的瞬态性能和较好的鲁棒性.     

无人水面艇复合自适应轨迹跟踪控制

针对存在模型参数不确定性和极易受到风、浪、流等时变干扰的欠驱动无人水面艇的轨迹跟踪控制问题,根据扰动观测器能对不确定项和外界干扰进行估计和补偿且具有鲁棒性特点,提出一种基于复合扰动观测器的自适应轨迹跟踪控制。该复合自适应观测器利用跟踪误差和估计误差共同调节自适应参数,在不激励高频未建模动态的情况下,该复合自适应闭环控制系统可得到更快的收敛速度和更高的跟踪精度。理论分析和仿真实验证明了所提出的无人水面艇复合自适应控制的有效性。     

欠驱动无人船非奇异固定时间鲁棒包容控制

针对外界干扰下的欠驱动无人船包容控制问题,提出一种新型非奇异固定时间滑模控制策略.整个控制器设计过程分为运动学回路设计和动力学回路设计.在运动学回路设计中,利用图论知识和固定时间稳定性理论设计非奇异固定时间分布式虚拟控制律,使得所有跟随船在固定时间内收敛于领导船张成的凸包内;在动力学回路设计中,为实现对虚拟控制律的跟踪控制,利用固定时间滑模控制法设计鲁棒包容控制律.最后,证明系统跟踪误差在固定时间收敛于平衡点,且与船舶的初始状态无关.仿真结果验证了所提出控制策略的有效性.     

非线性变参数无人船艏向$H_infty$鲁棒控制

针对水流冲击引起无人船(unmanned surface vehicle,USV)转艏呈现非线性特点,建立基于转艏运动的非线性变参数(nonlinear parameter-varying,NPV)USV模型,并提出一种NPV $H_\infty$ 艏向控制方法,以提高艏向调节的快速性和鲁棒性.首先,考虑低展弦比机翼理论能较好地描述船体受水流冲击的特点,建立基于水动力阻尼的非线性Fossen模型.通过忽略横荡速度和横流阻力将动力学模型简化为操纵动力学模型,并引入艏向角,建立NPV艏向模型.其次,构造与艏向控制系统状态和纵荡速度变参相关的Lyapunov函数,推导出满足艏向闭环控制系统$H_\infty$鲁棒稳定的非线性控制器求解条件,该条件是一个非线性矩阵不等式(nonlinear matrix inequality,NLMI).由于NLMI难以求解,根据平方和(sums of squares,SOS)理论,用多项式矩阵代替NLMI中的非线性矩阵,并将NLMI 转化为可使用SOS工具求解的多项式线性矩阵不等式.仿真结果表明,NPV $H_\infty$控制器在艏向调节时具有较快的系统响应和更高的准确性.     

Pareto optimum design of an adaptive robust backstepping controller for an unmanned aerial vehicle

This research develops an adaptive robust backstepping (AR-backstepping) controller for stabilization of an unmanned aerial vehicle (UAV) having strong coupling and highly nonlinear dynamics. At first, the backstepping control method as the basic stabilizer is utilized to determine the control efforts of the considered UAV. Next, an adaptive-robust mechanism subject to gradient decent methods and sliding surfaces is implemented to regulate the control gains. In fact, this mechanism determines the speed of changes of the gain values of the backstepping controller to make better responses in the presence of disturbances and uncertainties. Then, the optimum values of the design parameters related to the adaptive-robust mechanism are selected by using a multi-objective ant-lion optimization (MOALO) algorithm to simultaneously minimize the total error and control efforts. Finally, the results for a UAV developed in the Sirjan University of Technology, Sirjan, Iran, are given to confirm the effectiveness, robustness, and advantages of the designed AR-backstepping controller.     

Experimental validation of a model-based robust controller for multi-body mechanisms with flexible links

This paper presents the experimental validation of a model-based robust approach to the synthesis of position and vibration controllers for flexible link mechanisms. The design approach is based on the solution of a mixed-norm (H ₂/H _∞) problem, which allows ensuring, at the same time, satisfactory performances and robustness. A chief advantage of the approach proposed is that it allows designing robust control schemes by incorporating appropriate linear or piece-wise linear observers and regulators, which in turn can be synthesized making use of the accurate dynamic models currently available in literature.     

基于扰动观测器的水面无人船自适应模糊控制器设计

为了使水面无人船(USV)获得更好的跟踪性能,本文设计了基于扰动观测器和命令滤波器的自适应模糊控制器.对于该系统存在建模不确定性和外部环境的扰动,采用模糊逻辑系统(FLS)和一个新的扰动观测器对其进行逼近和补偿.在扰动观测器和控制器中加入了一个新的自适应参数,用来改善控制精度.基于此,本文设计了命令滤波反步控制方法,可以保证系统在所有状态下都是有界的,且跟踪误差在有限时间内小于规定的精度.仿真结果显示该方法有效,且可以满足给定的控制精度.     

小型无人直升机姿态非线性鲁棒控制设计

本文针对小型无人直升机的姿态控制问题,通过系统参数辨识,获得了较为准确的无人直升机姿态动力学模型.并根据无人直升机的动态特性,设计了基于神经网络前馈与滑模控制的非线性鲁棒姿态控制律,该控制律对直升机模型的先验知识要求较低.利用基于Lyapunov的分析方法证明,设计的控制律能够实现对无人直升机姿态角的半全局指数收敛镇定控制,并能确保闭环系统的稳定性.基于姿态飞行控制实验平台的实时飞行控制实验结果表明,提出的控制设计取得了很好的姿态控制效果,并对系统不确定性和外界风扰动具有较好的鲁棒性.     

Adaptive output-feedback formation control for underactuated surface vessels

ABSTRACT

This paper investigates the leader–follower formation problem of underactuated surface vessels. Velocities of both leader and follower vessels are unavailable. Model uncertainties and ocean disturbances are also considered. By incorporating adaptive control, neural networks (NNs), the high-gain observer (HGO) and the minimal learning parameter (MLP) algorithm in the backstepping procedure, a novel adaptive output-feedback formation control scheme is developed. We show that formation errors can be guaranteed to be semiglobally uniformly ultimately bounded (SGUUB) with the proposed controller. Compared with existing methods, the formation can be achieved only with position and yaw angle of both leader and follower. Meanwhile, the developed scheme can enhance the robustness of the closed-loop system with less computational effort, where only two online parameters need to be tuned. Simulation and comparison results are provided to illustrate the effectiveness of theoretical results.     

基于状态反馈控制器的多无人水面船集群控制

研究在时变环境干扰和输入饱和约束条件下,基于状态反馈控制器的多无人水面船集群控制.首先,为了准确地估计时变的海洋环境干扰,提出一种有限时间干扰观测器;然后,为了处理执行机构的物理约束,采用一种辅助动态系统;最后,为了实现多无人水面船集群控制,设计一种状态反馈控制器.采用李雅普诺夫方法证明了系统的稳定性,仿真结果验证了所设计的状态反馈控制器的有效性.     

基于改进DWA的多无人水面艇分布式避碰算法

针对多艘无人水面艇(USV)相遇自主避碰问题,考虑可能存在异常行驶的USV,基于改进动态窗口法(DWA)提出一种包含碰撞风险检测和行驶职责划分的分布式避碰算法.首先,引入障碍物预测轨迹和权重因子改进传统DWA的距离评价函数,提高USV躲避多个动态障碍物的能力,同时,结合国际海上避碰规则(COLREGS)引入新的规则评价函数约束USV的避让动作;然后,引入期望速度和航向改进现有碰撞风险检测算法,减少因碰撞风险变化导致的轨迹波动;接着,针对COLREGS仅规定两船相遇时的行驶职责划分问题,提出一种考虑异常USV的多USV职责划分方法;最后,基于Matlab实现多USV相遇自主避碰仿真.实验结果表明,即使存在异常USV,分布式避碰算法依旧保证正常USV能够作出符合COLREGS的安全避让动作.     

Data‐driven robust backstepping control of unmanned surface vehicles

In this article, a novel data‐driven robust backstepping control (DRBC) approach for tracking of unmanned surface vehicles (USVs) with uncertainties and unknown parametric dynamics has been developed. Main contributions are fourfold: (a) Unlike previous approaches, within the DRBC scheme, backstepping decoupled technique and data‐driven sliding‐mode control (DSMC) can be effectively cohered. (b) Using backstepping philosophy, a new data‐driven PI‐type sliding‐mode surface is devised, such that strong robustness with simple structure can be ensured. (c) Complex unknowns including couplings, uncertainties and parametric dynamics are sufficiently lumped, and are totally compensated by the extended state observer. (d) The entire DRBC scheme eventually achieves accurate tracking of USVs with strong couplings, uncertainties and unknown parametric dynamics. The efficacy and superiority of the proposed DRBC approach is validated on a prototype USV.     

小型无人直升机的无模型自适应鲁棒控制设计

本文针对小型无人直升机的姿态控制问题,考虑到现有基于模型的控制方法对系统动力学模型的依赖性,以及未建模动态对系统控制性能的影响,设计了一种新的基于数据驱动的无模型自适应鲁棒控制律.通过基于数据驱动的设计方法,降低了控制器对直升机动力学模型先验知识的依赖,补偿了未建模不确定性的影响.仅利用无人直升机的输入输出数据,即可实现对无人直升机系统的稳定姿态控制.然后本文结合离散滑模控制设计,补偿了未知外界扰动的影响,提高了系统的鲁棒性,并通过理论证明了控制误差的收敛性和闭环系统的稳定性.最后,在本研究组自主开发的无人直升机飞行控制实验平台上,进行了无人机实时控制实验.实验结果表明,本文所提出的控制算法取得了很好的姿态控制效果,并对系统不确定性和外界风扰动具有良好的鲁棒性.     

High-level mobility controller for a remotely operated unmanned land vehicle

The U.S. Army Laboratory Command, as part of the Department of Defense Robotics Testbed Program, is developing a testbed for cooperative, real-time control of unmanned land vehicles. The program entails the development and integration of many elements which allow the vehicles to perform both autonomous and teleoperated functions. The National Institute of Standards and Technology (NIST) is supporting this program by developing the vehicle control system using the Real-time Control System (RCS) architecture. RCS is a hierarchical, sensory-based control system, initially developed for the control of industrial robots and automated manufacturing systems. NIST is developing the portions of RCS that control all vehicle mobility functions, coordinate the operations of the other subsystems on the vehicle, and communicate between the vehicle and the remote operator control station. This paper reviews the overall control system architecture, the design and implementation of the mobility and communication functions, and results from recent testing.This work is funded by the U.S. Army Laboratory Command. This paper was prepared by U.S. Government employees and is not subject to copyright. Equipment listings do not imply a recommendation by NIST.     

无人艇全分布式动态事件触发编队控制

针对通信资源受限的多无人艇(USV)编队控制问题, 本文提出了一种动态事件触发数据传输机制以降低通信频率, 减少控制算法对系统带宽的占用. 首先, 基于滑模和自适应控制算法设计一种全分布式编队控制器, 使得所有编队成员在保持预设队形的同时能够完成对期望轨迹的跟踪. 与现有编队控制器相比, 该控制器不需要通信网络的全局信息. 然后, 基于Lyapunov稳定性理论证明了编队跟踪误差以及所有闭环信号都能达到稳定状态. 此外,该算法能够保证触发时间序列不表现出Zeno行为. 最后, 通过数值仿真验证了全分布式编队控制器的有效性     

A simple robust control for global asymptotic position stabilization of underactuated surface vessels

Global asymptotic stabilization of underactuated surface vessels is generally achieved only by designing complicated controllers. This paper proposes a very simple control law that globally asymptotically stabilizes the position of underactuated surface vessel to a desired constant location and its velocities to zero. The proposed controller is independent of velocity signals and is robust to model parameters. It neither includes an observer nor an adaptive/sliding‐mode law. Controller development and stability analysis rely on a novel Lyapunov function and LaSalle's theorem. Furthermore, by extending the proposed control strategy, a saturated control law is also obtained ensuring the semiglobal asymptotic stability of position error system. Effectiveness of the proposed control schemes is demonstrated by simulation examples. Copyright © 2017 John Wiley & Sons, Ltd.     

无人机吊挂飞行的非线性控制方法设计

针对四旋翼无人机吊挂飞行系统,本文设计了一种新型控制策略.本文首先建立了四旋翼无人机吊挂系统的数学模型.其中负载被看作由刚性绳悬挂在四旋翼无人机重心位置的质点.之后本文通过能量分析的方法设计了针对此系统的非线性控制器.本文提出的控制方法可以在抑制吊挂负载摆动的同时将四旋翼无人机移动到目标位置.本文运用李雅普诺夫稳定性分析和拉塞尔不变性原理对闭环系统的稳定性进行了证明.最后,通过数值仿真,分别将本控制器镇定控制和调节控制的控制效果与线性二次调节器(linear-quadratic regulator,LQR)控制器进行了对比.     

Experimental investigation on adaptive robust controller designs applied to a free-floating space manipulator

This paper aims to formulate and investigate the application of various nonlinear H_∞ control methods to a free-floating space manipulator subject to parametric uncertainties and external disturbances. From a tutorial perspective, a model-based approach and adaptive procedures based on linear parametrization, neural networks and fuzzy systems are covered by this work. A comparative study is conducted based on experimental implementations performed with an actual underactuated fixed-base planar manipulator which is, following the DEM concept, dynamically equivalent to a free-floating space manipulator.     

基于无线数传技术的无人船控制系统设计与实现

针对于现有的无人船(unmanned surface vehicle)存在的问题,为提高其控制行驶最大距离,设计一种以无线数据传输模块为传输介质的系统,传输下位机与上位机之间的数据;从激光雷达的二维扫描图像信息,根据SLAM (simultaneous localization and mapping)算法制作出水面环境的栅格地图圈定卫星地图盲区,组合多种传感器定位的方式估算无人船相对位置并定位在卫星离线地图,以达到按路径规划行进的目的;设计了上位机软件和基于STM32的控制器;无人船位姿信息发送到上/下位机,上位机得到信息向下位机传输实现远程遥控行驶的目的;实验结果表明,与常规的网络信号发射和接收传输数据不一样,在无网络基站环境中仍能够在1 200 m以内保持良好的远程控制,证实了系统的可靠性和准确性。