旋翼飞行机械臂系统的混合视觉伺服控制

旋翼飞行机械臂是一种具有强耦合特性的机器人系统,借助视觉进行自主作业还存在诸多问题,如实时深度估计、目标极易丢失以及目标笛卡尔空间模型重建等.本文针对传统的基于图像与基于位置的视觉伺服的缺陷以及系统自身欠驱动等问题,建立了运动学模型和提出了基于力平衡原理的动力学联合建模,并通过欧几里得单应性矩阵分解设计出旋翼飞行机械臂系统的混合视觉伺服控制方法,在图像空间控制平移、笛卡尔空间控制旋转,减弱了平移与旋转之间的相互影响实现解耦效果,改善了系统对非结构因素的抗扰性能和全局稳定性.通过仿真和实验检验了系统鲁棒性和算法优越性.     

旋翼飞行机器人研究进展

旋翼飞行机器人是面向空中自主作业需求,将旋翼飞行器与多自由度机械臂相结合所提出的新型机器人.该机器人作业过程中旋翼飞行器、机械臂与作业目标之间的动态相对运动以及与作业目标接触过程中未建模外力、力矩扰动使自主控制受到极大挑战.本文将针对旋翼飞行机器人的结构演变及关键技术、作业机构集成技术进行综述.从动力学建模及动力学特性分析、动态运动约束/力约束下的协调规划、非结构环境下的运动和作业控制、面向任务动态操作的环境感知、面向任务的实验系统构建与实验验证五个方面初步构建了旋翼飞行机器人自主作业理论体系.     

四旋翼飞行仿真器的建模研究

本文针对四旋翼飞行仿真器系统的非线性.采用RBF-ARX模型对四旋翼飞行仿真器系统进行了离线动态特性建模的研究.着重讨论了RBF-ARX模型结构的选取,模型参数辨识,RBF参数优化等问题.RBF-ARX模型与ARX模型的一步预测输出比较的结果证实了RBF-ARX模型在非线性系统建模中的优越性.     

双闭环四旋翼飞行器姿态稳定算法研究

小型四旋翼飞行器系统属于欠驱动、强耦合度的控制系统,在复杂外部空间飞行环境中,需要建立飞行姿态动力学模型,对多变量系统受到自然环境、气流、陀螺效应等的影响进行控制.虽然近年来新型材料、磁惯导技术和控制技术得到快速发展,但仍旧要针对四旋翼飞行器垂直起降、平行飞行等环节,选取模糊自整定PID控制、反演滑模控制、动态逆控制、线性二次高斯控制等方式,进行四旋翼飞行器飞行姿态与抖动的控制.采用自适应反演滑模控制算法,设计自适应高度控制器、补偿器,进行飞行器转动惯量、多变量负载控制,提高系统自我调节和抗干扰能力.     

四旋翼飞行姿态测试平台设计及稳定性分析

四旋翼飞行器非线性、强耦合以及欠驱动的特性极大地增加了算法设计与姿态控制的难度。为了减少四旋翼飞行器飞行过程中不必要的干扰因素和事故率,自主设计了四旋翼飞行姿态测试平台。通过对系统进行受力分析和动态建模,采用能够快速稳定的双闭环串级PID控制算法设计了姿态控制器,并使用卡尔曼滤波算法进行姿态估计,然后分别在Matlab环境和平台上验证了飞行姿态的稳定性。实验结果表明了平台设计的合理性和可行性,是一种有效的四旋翼飞行姿态测试平台。     

四旋翼无人机吊挂系统防摆控制方法研究北大核心CSCD

为了解决四旋翼无人机在吊挂负载飞行过程中吊挂负载在其水平方向摆角波动过大、不能消除、四旋翼无人机无法精确定位等实际工程问题,通过能量分析的方法研究提出了一种基于能量分析的四旋翼无人机吊挂飞行系统非线性耦合防摆控制器。首先,采用拉格朗日法建立了四旋翼无人机吊挂飞行系统的二维动力学模型;然后,通过非线性能量耦合的方法设计了针对此系统的非线性耦合防摆控制器,通过拉塞尔不变性原理和李雅普诺夫方法证明了该闭环反馈控制系统的稳定性。结果表明,所提出的非线性能量耦合控制器能够适用于多种飞行运输情景,在其改变飞行目标位置、吊挂负载质量、附加初始摆动时均有良好的控制效果。最后,通过数值仿真,与其他基于能量分析的控制器,就其目标定位、摆角消除等控制效果进行了对比,结果表明所提出的控制器在改变飞行目标位置、吊挂负载质量、附加初始摆动时,均具有良好的鲁棒性。     

四旋翼飞行器建模及其运动控制

针对四旋翼飞行器是一个欠驱动、强耦合、非线性系统,提出了运用反步法解决系统非线性问题,达到对飞行器快速、准确、稳定控制目的.研究了以反步法作为非线性设计工具对飞行器控制系统的设计问题,将飞行控制系统分为内外环2个子系统.建立四旋翼飞行器动力学及运动学方程,并对数学模型进行适当简化.利用反步法求解飞行器内环姿态控制律,实现对目标姿态角的稳定控制;利用比例—积分—微分(PID)作为飞行器外环位置控制律,实现对目标位置的稳定控制.搭建飞行器系统模型,进行Matlab/Simulink仿真实验,结果表明:在小角度飞行和悬停状态下,飞行器的位置与姿态精度得到了有效控制,验证了数学模型与控制律设计的准确性.     

沈阳自动化所旋翼飞行机器人完成全功能自主飞行试验

由中科院沈阳自动化所机器人学国家重点实验室旋翼无人机组自主研发的15公斤负载级旋翼飞行机器人,日前在无锡某空域完成了全自主起飞、悬停、爬升、加减速、航迹跟踪、下降等飞行科目后,稳稳地降落在了预定位置,成功完成了全功能自主飞行。此次试飞标志着旋翼飞行机器人完成使命任务过程中已经实现不需要任何人为参与,为多项国家级项目的完成奠定了重要的基础。旋翼飞行机器人以其在多领域的潜在用途而受到国内外的普遍重视。但受其涉及多学科、系统复杂、技术封闭等影响,目前仅有美国、奥地利、瑞士等少数国家具备旋翼飞行机器人全功能自主飞行技术。此次试飞成功标志着沈阳自动化所在旋翼飞行机器人研究方面取得了重大突破。     

开环机器人运动优化的仿真研究

本文基于递推多体动力学的李群表示方法,提出了使用混合编程和句柄图形来设计机器人仿真软件的思想。进一步地,在VisualC++6.0编译环境下,调用MATLAB函数库开发了三维可视化的开环机器人仿真软件。此软件能够实现欠驱动系统、机器人、步行机械等复杂系统建模和运动优化,且可以完全独立于MATLAB运行,灵活性强。可对欠驱动系统和人类运动系统进行运动优化,具有良好的应用价值。     

基于自抗扰控制技术的实时飞行仿真研究(英文)

针对四旋翼无人机欠驱动、强耦合的非线性动力学特性,文中研究设计了基于自抗扰控制技术的闭环飞行控制系统。自抗扰控制技术中,扩张观测器与基于误差的非线性反馈控制是其重要的两个部分。扩张状态观测器估计外部干扰和模型不确定性,以实现干扰和模型不确定性的动态补偿;此外,采用基于误差的非线性反馈可以改善控制效果。为保证飞行任务中精确的航迹跟踪,文中分析设计了一种实用的制导策略,并构建实时可视化飞行仿真系统以实现对所设计的制导策略和自抗扰飞行控制系统更为严格有效的验证。仿真结果表明所研究设计的制导策略和闭环飞行控制系统具有良好的制导和控制性能。     

Adaptive Interconnection and Damping Assignment Passivity Based Control for Underactuated Mechanical Systems

In this paper, we present two adaptive control approaches to handle uncertainties caused by parametric and modeling errors in a class of nonlinear systems with uncertainties. The methods use the Port-controlled Hamiltonian (PCH) modelling framework and the interconnection and damping assignment passivity-based control (IDA-PBC) control design methodology being the most effectively applicable method to such models. The methods explore an extension on the classical IDA-PBC by adopting the state-transformation, yielding a dynamic state-feedback controller that asymptotically stabilizes a class of underactuated mechanical systems and preserves the PCH structure of the augmented closed-loop system. The results are applied to the underactuated mechanical systems that are a class of mechanical systems with broad applications and are more interesting as well as challenging control problems within this context. The results are illustrated with numerical simulations applied to two underactuated robotic systems; the Acrobot and non-prehensile planar rolling robotic (disk-on-disk) systems.

     

Nonlinear coupling tracking control for underactuated construction lifting robots with load hoisting/lowering under initial input saturations

Underactuated construction lifting robots, which have been widely concerned by erudite researchers, always contain load hoisting/lowering motion. When the cable length is utilized as a variable, construction lifting robots produce violent load swing, which affects the construction safety undoubtedly and brings great challenges to the development of the controller. Moreover, most existing controllers may not take into account issues, such as initial input saturations and poor ability to suppress load swing, and they may utilize linearization or approximation. Inspired by these phenomena, a nonlinear coupling tracking controller for underactuated construction lifting robots with load hoisting/lowering under initial input saturations is proposed. With reference to expected trajectories to ensure the smooth operation of the construction lifting robot system, the initial input saturations are considered to make the trolley and cable start stably, respectively; a coupling signal, which contains actuated variables and underactuated variables, is constructed to improve the transient control performance of construction lifting robots. Combined with theoretical derivation, simulation, and experimental verification, the proposed controller achieves superior control performance, which ensures the accurate positionings of the system, and suppresses and eliminates the load swing effectively, so as to ensure the safe construction; the proposed controller admits outstanding robustness with respect to the changes of system parameters and the adverse effects of external disturbances. The proposed controller provides a novel antiswing strategy for construction lifting robots with load hoisting/lowering, which possesses excellent practical significance.     

The dexterity and singularities of an underactuated robot

Underactuated robots are robotic systems with more joints than actuators. A robot may be underactuated by design as in the case of a hyper‐redundant robot with passive joints or may become underactuated as a result of an actuator failure. In this article, we examine the dexterity of underactuated robots whose passive joints operate in either a locked or free‐swinging mode. The ability to an analyze the dexterity of an underactuated robot has important applications especially for the control of passive joints with brakes and for the fault tolerance analysis of an otherwise fully actuated kinematically redundant robot. The approach applied here is to use kinematics and dynamics‐based formulations of manipulator dexterity. We then characterize passive‐joint singularities, i.e., configurations where full end‐effector control is lost because one or more joints are passive instead of active. Lastly, we introduce a new characterization of joint‐limit singularities, which are configurations where full end‐effector control cannot be achieved because one or more joints are at their joint limits. © 2001 John Wiley & Sons, Inc.     

An adaptive vision-based autopilot for mini flying machines guidance,navigation and control

The design of reliable navigation and control systems for Unmanned Aerial Vehicles (UAVs) based only on visual cues and inertial data has many unsolved challenging problems, ranging from hardware and software development to pure control-theoretical issues. This paper addresses these issues by developing and implementing an adaptive vision-based autopilot for navigation and control of small and mini rotorcraft UAVs. The proposed autopilot includes a Visual Odometer (VO) for navigation in GPS-denied environments and a nonlinear control system for flight control and target tracking. The VO estimates the rotorcraft ego-motion by identifying and tracking visual features in the environment, using a single camera mounted on-board the vehicle. The VO has been augmented by an adaptive mechanism that fuses optic flow and inertial measurements to determine the range and to recover the 3D position and velocity of the vehicle. The adaptive VO pose estimates are then exploited by a nonlinear hierarchical controller for achieving various navigational tasks such as take-off, landing, hovering, trajectory tracking, target tracking, etc. Furthermore, the asymptotic stability of the entire closed-loop system has been established using systems in cascade and adaptive control theories. Experimental flight test data over various ranges of the flight envelope illustrate that the proposed vision-based autopilot performs well and allows a mini rotorcraft UAV to achieve autonomously advanced flight behaviours by using vision.     

Robust adaptive path following of underactuated ships

Robust path following is an issue of vital practical importance to the ship industry. In this paper, a nonlinear robust adaptive control strategy is developed to force an underactuated surface ship to follow a predefined path at a desired speed, despite the presence of environmental disturbances induced by wave, wind and ocean-current. The proposed controller is scalable and is designed using Lyapunov's direct method and the popular backstepping and parameter projection techniques. Along the way of proving closed-loop stability, we obtain a new stability result for nonlinear cascade systems with non-vanishing uncertainties. Interestingly, it is shown in this paper that our developed control strategy is easily extendible to situations of practical importance such as parking and point-to-point navigation. Numerical simulations using the real data of a monohull ship are provided to illustrate the effectiveness of the proposed methodology for path following of underactuated ships.     

基于自适应Backstepping的欠驱动AUV三维航迹跟踪控制

为了实现欠驱动自治水下机器人（AUV）三维航迹跟踪控制,基于非完整系统理论分析了AUV缺少横向推进器时的欠驱动控制系统特性,并验证了欠驱动AUV存在加速度约束不可积性.基于李亚普诺夫稳定性理论,利用自适应Backstepping设计连续时变的航迹点跟踪控制器,以抑制外界海流的干扰.仿真实验表明,所设计的控制器能实现欠驱动AUV对一序列三维航迹点的渐近镇定,并且航迹跟踪的精确性和鲁棒性明显优于PID控制.     

Mini Rotorcraft Flight Formation Control Using Bounded Inputs

In this paper, the flight formation control and trajectory tracking control design of multiple mini rotorcraft systems are discussed. The dynamic model of a mini rotorcraft is presented using the Newton-Euler formalism. Our approach is based on a leader/follower structure of multiple robot systems. The centroid of the coordinated control subsystem is used for trajectory tracking purposes. A nonlinear controller based on separated saturations and a multi-agent consensus algorithm is developed. The analytic results are supported by simulation tests. Experimental results include yaw coordination and tracking only.     

含不等式约束的欠驱动系统约束跟随控制

在运动控制领域, 欠驱动机械系统通常需要满足一系列的等式约束(完整或非完整的)以便获得较好的运动 表现, 同时出于安全考虑还需要满足一定的不等式约束条件. 本文提出了一种约束跟随控制方法, 用以解决同时含 等式和不等式约束的欠驱动系统控制问题. 该控制设计主要分为两步: 第1步: 只考虑系统需要满足的等式约束, 运 用约束跟随控制方法推导出基于系统模型的状态反馈控制律; 第2步: 考虑系统需要满足的不等式约束, 先通过状 态变量映射将不等式约束整合到原等式约束中以得到新的等式约束, 再基于新的等式约束和第1步所述的约束跟随 控制方法, 推导出系统所需的状态反馈控制律. 将该约束跟随控制方法应用于三自由度非线性强耦合的欠驱动平面 垂直起降(PVTOL)飞行器. 仿真结果表明, 该控制方法能有效处理PVTOL飞行器运动过程中需满足的等式约束(轨 迹跟踪和姿态保持)和不等式约束(边界服从).     

一类欠驱动机械系统的动态及其稳定控制

Abstract The control of underactuated mechanical systems is very complex for the loss of its control inputs. The model of underactuated mechanical systems in a potential field is built with Lagrangian method and its structural properties are analyzed in detail. A stable control approach is proposed for the class of underactuated mechanical systems. This approach is applied to an unde ractuated double-pendulum-type overhead crane and the simulation results illustrate the correctness of dynamics analysis and validity of the proposed control algorithm.     

Globally Stabilizing a Class of Underactuated Mechanical Systems on the Basis of Finite-Time Stabilizing Observer

Globally exponentially stabilizing a class of underactuated mechanical systems (UMS) with nonaffine nonlinear dynamics is investigated in this paper. The considered UMS has a nonaffine nonlinear subsystem that can be globally asymptotically stabilized by saturated feedbacks, but the saturated feedback cannot be analytically expressed in closed-form. This obstacle limits the real-time applications of most controllers presented in literatures. In this paper, a hybrid feedback strategy is presented to globally exponentially stabilize the UMS with nonaffine and strict-feedback canonical forms. The hybrid feedback strategy is characterized by the composition of partial states feedback and partial virtual outputs feedback based on a higher-order finite-time stabilizing observer. The presented hybrid feedback controller can be synthesized by applying Lyapunov stability theory. Some numerical simulations associated with two underactuated nonlinear systems, the Acrobot system and the Inertia-Wheel-Pendulum (IWP) system, are employed to demonstrate the effectiveness of the proposed controller. The presented control strategy can be applied in real time, thus providing a new feasible dynamic model other than the differential flatness systems for synthesizing the mechanical systems of general underactuated legged robots.