航天器机械臂柔性力控辅助装配方法

文章从装配的实际需求出发,提出一种航天器机械臂柔性力控辅助装配方法:通过在机械臂末端法兰与负载之间安装的六维力传感器感知作用力与力矩信息,人手直接作用于机械臂末端的负载,系统通过负载的重力补偿算法获得人手作用的力与力矩信息,而后以力/力矩信息作为输入来控制机械臂进行移动或转动,使负载柔性跟随人手运动。文章给出了装配方法的详细设计方案与相关算法,并进行了初步试验验证。试验表明,该装配方法可以有效提高在航天器狭小空间内进行大重量工件安装的效率,且安全可靠。     

Continuous path control of space manipulators mounted on OMV

Theoretical analysis on the formulation of kinematics for the manipulator mounted on a satellite is presented. Firstly, to solve the inverse kinematics, the authors define a new generalized Jacobian matrix, and utilizing this generalized matrix, the problem can be treated analytically. Secondly, the authors verify the method proposed here in the simulation study. Thirdly, they also discuss on the several points which are indispensable for further investigations.     

面向空间近距离操作的机械臂与服务卫星协同控制

针对航天器在轨服务任务中涉及的空间近距离操作需求,提出一种机械臂与服务卫星协同控制方法。首先建立了机械臂和服务卫星组合体动力学模型以及服务卫星和目标卫星相对位姿耦合动力学模型。然后采用全局终端滑模控制设计了机械臂轨迹跟踪控制方法,采用PD控制设计了服务卫星相对位姿耦合控制方法,并将机械臂反作用力和力矩作为前馈补偿叠加到服务卫星控制系统中,实现了两者的协同控制。最后通过数值仿真验证了控制方法的有效性。仿真结果表明,该方法能够满足空间近距离操作任务对机械臂和服务卫星的控制精度、稳定性和误差收敛时间的要求,具有工程实用性。     

Dynamics analysis of space robot manipulator with joint clearance

A computational methodology for analysis of space robot manipulator systems, considering the effects of the clearances in the joint, is presented. The contact dynamics model in joint clearance is established using the nonlinear equivalent spring-damp model and the friction effect is considered using the Coulomb friction model. The space robot system dynamic equation of manipulator with clearance is established. Then the dynamics simulation is presented and the dynamics characteristics of robot manipulator with clearance are analyzed. This work provides a practical method to analyze the dynamics characteristics of space robot manipulator with joint clearance and improves the engineering application. The computational methodology can predict the effects of clearance on space robot manipulator preferably, which is the basis of space robot manipulator design, precision analysis and ground test.     

双臂自由飞行空间机器人的姿态控制方案

自由飞行空间机器人的姿态控制可考虑利用反作用轮或反作用喷气装置以机器人本体姿态不变，但这种方法存在的最大问题是消耗燃料，直接影响机器人的轨道寿命，同时对系统产生振动而导致系统不稳定，为此本文提出了另一种新的方案，即基于受限最小干扰图的姿态控制方案。这种方案不使用反作用轮或反作用喷气装置，而通过规划机械手末端的运动轨迹，使机器人的本体姿态在机械手动作过程中基本保持不变。为验证本文提出的姿态控制方案的     

目标捕获后航天器组合体的角动量转移与抑振规划

针对失稳目标捕获后航天器组合体的位姿调整与稳定问题,提出一种组合体角动量转移与振动抑制复合规划方法。首先建立了同时考虑了空间机械臂、目标卫星太阳翼、服务卫星太阳翼等柔性构件的航天器组合体动力学模型。然后提出角动量转移优化方法,规划机械臂最终构型,保证组合体相对稳定后的角速度最小;基于粒子群算法设计了机械臂最优抑振轨迹规划方法,抑制角动量转移过程中的机械臂和太阳翼的柔性振动。最后通过数值仿真验证了规划方法的有效性。仿真结果表明,该方法能够有效实现组合体的角动量转移,并显著降低组合体的柔性振动,具有工程实用性。     

Practical approaches to handle the singularities of a wrist-partitioned space manipulator

Space robotic systems are expected to play an increasingly important role in the future. However, the control methods based on the inverse kinematics are affected by singularities. In this paper, practical approaches are proposed to solve the problems of a wrist-partitioned space manipulator. For spacecraft-referenced end-point motion control, we presented the singularity separation plus damped reciprocal (SSPDR) method, which separates the singularity parameters from the inverse of the Jacobian, and replaces their reciprocals using the damped reciprocals. For another control strategy, i.e. inertially referenced end-point motion control, including spacecraft attitude-controlled mode and free-floating mode, the linear momentum equation is used to eliminate three independent variables. With modifying some expressions, the SSPDR method is utilized to solve the singularities of spacecraft attitude-controlled space robot. When the space robot is free-floating, the singularities, i.e. the so-called dynamic singularities, cannot be predicted according to its kinematic structure. Combining with the measured angular velocity of the base, the dynamic singularity handling problem is transformed into real-time kinematic singularity avoiding problem, which can be solved by the SSPDR method. Since the SVD decomposition, the estimation of the minimum singularity value, and the calculation of the generalized Jacobian matrix are not required, the algorithm has lower computation load. Another advantage is that, only the accuracy of part velocity components is reduced by adding the damped coefficients. Simulation results verify the proposed approaches.     

平面型两关节空间机器人的自适应轨迹控制

基于参数线性分离方法，得到了平面型两关节空间机器人线性参数化形式的动力学模型，这种模型非常适合于采用自适应控制方法。控制策略考虑了机器人各关节之间的耦合及机械臂与基座航天器之间的耦合，对航天器姿态的控制和机械臂的控制进行综合，在满足手端跟踪期望轨迹的同时，保证航天器姿态基本不变。控制器由一个PD反馈项和一个补偿动力学不确定性的非线性自适应反馈项构成，能够保证对期望关节轨迹的全局渐进跟踪，提高了空间机器人操作的适应性和安全性。     

Vibration control of a flexible space manipulator during on orbit operations

Space manipulators are complex systems, composed by robotic arms accommodated on an orbiting platform. They can be used to perform a variety of tasks: launch of satellites, retrieval of spacecraft for inspection, maintenance and repair, movement of cargo and so on. All these missions require extreme precision. However, in order to respect the mass at launch requirements, manipulators arms are usually very light and flexible, and their motion involves significant structural vibrations, especially after a grasping maneuver. In order to fulfill the maneuvers of space robotic systems it is hence necessary to properly model the forces acting on the space robot, from the main terms, such as the orbital motion, to the second order perturbations, like the gravity gradient and the orbital perturbations; also flexible excitation of the links and of the joints can be of great importance in the manipulators dynamics. The case is furthermore complicated by the fact that the manipulator, together with its supporting spacecraft, is an unconstrained body. Therefore the motion of any of its parts affects the entire system configuration. The governing equations of the dynamics of such robotic systems are highly nonlinear and fully coupled. The present paper aims at designing and studying active damping strategies and relevant devices that could be used to reduce the structural vibrations of a space manipulator with flexible links during its on orbit operations. In particular an optimized adaptive vibration control via piezoelectric devices is proposed. The number of piezoelectric devices, their placement and operational mode should be correctly chosen in order to obtain maximum performance in terms of elastic oscillations reduction and power consumption. Even though an optimal placement cannot have a universal validity, since it depends on the type of maneuver and on the overall inertial and geometrical characteristics, an approach to solve the problem is proposed.     

故障容错机械臂运动学可靠性设计

从机械臂运动学的角度，定义了故障容错机械臂、故障容错机械臂的阶、通用故障容错机械臂、特定任务故障容错机械臂，论证了通过运动学关节冗余也同样可以提高机械臂系统的可靠性、故障容错机械臂应该具备的自由度数、以及针对不同的任务要求来设计故障容错机械臂的方法。通过将任务空间抽象简化为一系列的特征点，建立与机械臂参数向理想值接近程度相关的罚函数，选择有效的优化算法，设计出了通用一阶故障容错平面位置机械臂、通用一阶故障容错空间位置机械臂、以及特定任务一阶故障容错平面位置机械臂。建立起完整的故障容错机械臂设计方法，对航天机器人的研究具有一定价值。     

载人航天器柔性机械臂的动力学建模方法

空间机械臂在载人航天活动中有着迫切的应用需求。航天器尺寸、质量等因素的限制使得空间机械臂具有大柔性的特点。文章结合空间机械臂应用环境的特殊性,论述了空间柔性机械臂多体动力学和关节的动力学建模方法,分析比较了不同建模方法的特点。为了满足未来空间机械臂在航天器工程应用的要求,文章指出,空间柔性机械臂宜采用混合坐标法描述臂杆刚性运动与柔性变形的耦合;开展关节精细动力学研究,宜将重点放在齿轮传动系统的低速级上。     

纤维铺放设备机械手臂末端运动轨迹的后置处理技术研究

在已知被铺放芯模和芯模铺放纤维轨迹的基础上,对数控铺放设备的后置处理算法 进行了研究。通过铺放设备运动过程的分析,将这种冗余度机器人的七个关节分两个部分处 理：主轴关节部分和机械手臂部分。运用机器人学相关原理建立杆件坐标系,通过机器人运 动学的正解和逆解,得到了机械手臂六关节变量的解。提出利用投影向量法判断铺放螺旋轨 迹方向。同时为了实现铺放过程的运动仿真,系统阐述了铺放轨迹的前期处理方法。分析了 铺放头角度参数和位置参数的关系及铺放头角度参数的合理范围。最后通过铺放运动过程仿 真,证明了所提出的后置处理算法和轨迹数据前期处理方法的正确性。     

Telerobotics and orbital laboratories: an end-to-end analysis and demonstration

A preliminary analysis of the United States Laboratory (USL) module of the International Space Station has been completed. A major conclusion was that one of the most limited resources within the USL will be crew time. A laboratory robot would alleviate these constraints, improve safety, and reduce operational costs. A laboratory experiment manipulator system (LEMS) is proposed, made up of an on-board mobile manipulator and a computer-assisted operator control station. The on-board manipulator concept was tested with an Intelledex 660 industrial robot. Operator joystick command capability and delayed video feedback were added to simulate a Space Station Teleoperation system. The implementation of a unique predictive display was chosen for further evaluation because of its promise as a partial solution to the classical problem of robot remote control in the presence of time delay. The incorporation of various correction factors to calibrate the robot predictor model, including geometric distortion and spherical aberration caused by the video optics, is described.     

偏置式冗余空间机械臂逆运动学求解的参数化方法

针对肩、肘、腕均有偏置的空间站遥操作机械臂（SSRMS）型7DOF冗余机械臂,提出了逆运动学求解的关节角参数化及臂型角参数化两种方法。前者根据机械臂的臂型特征,推导以θ1、θ2、θ6、θ7中的一个作为给定参数时其他关节角的表达式,得出8种可能解;后者首先构造与SSRMS型机械臂相对应的零偏置球关节-旋转关节-球关节（SRS）机械臂,然后以臂型角为参数求解SRS机械臂的逆运动学,再根据SSRMS与SRS机械臂的关系,得到SSRMS的8组逆解。仿真算例校验了所提方法的有效性。     

一种带精确补偿的卫星姿态快速机动控制方法

针对挠性卫星姿态敏捷机动中,挠性模态和星体转动惯量不确知,进而影响前馈补偿的有效性的问题,提出一种将非线性状态观测器和转动惯量辨识相结合的精确补偿控制方法。证明了一般挠性卫星动力学的非线性项满足Lipschtiz条件,可引入非线性观测器,实现了挠性模态的准确估计。设计了一种基于角速度最优阶拟合的转动惯量校正方法,进一步提高前馈补偿的精度和姿态机动的快速性。数学仿真对比结果表明：本文所提的精确补偿控制方法,能够有效减少挠性附件振动和转动惯量不准确对姿态控制的影响,提高姿态控制的响应速度,满足挠性卫星机动过程的快速性和稳定性,适用于挠性卫星的姿态敏捷机动控制。     

柔性多体航天器单向递推组集建模方法

本文提出一种面向计算机建立柔性多体航天器动力学方程的新方法，其特点是完成运动学正向递推同时实现动力学方程的组集。这种方法不仅可提高航天器、空间机械臂动力学仿真的计算效率，而且可有效地克服数值积分病态的困难。文末一个空间四杆柔性机械臂的算例验证了这种建模方法的上述优点。     

过驱动航天器飞轮故障重构与姿态容错控制

针对四反作用飞轮配置的刚体航天器执行机构故障以及外部干扰等问题,提出一种姿态容错控制分配算法。该方法通过设计滑模观测器,实现在有限时间内对执行机构故障与外部干扰的精确重构;特别地,应用Lyapunov稳定性理论证明了所设计的控制器能够在有限时间内实现对闭环姿态的全局渐近稳定控制,且该控制策略可实现对反作用飞轮故障与外部干扰的鲁棒性。此外,采用计算量较小的基序最优控制分配方法快速实现了期望控制力矩到四反作用飞轮指令控制力矩分配。最后,针对某型号航天器以及各种反作用飞轮故障进行数值仿真,仿真结果表明所设计过驱动航天器飞轮故障重构与姿态容错控制方法能够在线、及时、精准地完成故障重构与控制分配。     

Adaptive and robust algorithms and tests for visual-based navigation of a space robotic manipulator

Optical navigation for guidance and control of robotic systems is a well-established technique from both theoretic and practical points of view. According to the positioning of the camera, the problem can be approached in two ways: the first one, “hand-in-eye”, deals with a fixed camera, external to the robot, which allows to determine the position of the target object to be reached. The second one, “eye-in-hand”, consists in a camera accommodated on the end-effector of the manipulator. Here, the target object position is not determined in an absolute reference frame, but with respect to the image plane of the mobile camera. In this paper, the algorithms and the test campaign applied to the case of the planar multibody manipulator developed in the Guidance and Navigation Lab at the University of Rome La Sapienza are reported with respect to the eye-in-hand case. In fact, being the space environment the target application for this research activity, it is quite difficult to imagine a fixed, non-floating camera in the case of an orbital grasping maneuver. The classic approach of Image Base Visual Servoing considers the evaluation of the control actions directly on the basis of the error between the current image of a feature and the image of the same feature in a final desired configuration. Both simulation and experimental tests show that such a classic approach can fail when navigation errors and actuation delays are included. Moreover, changing light conditions or the presence of unexpected obstacles can lead to a camera failure in target acquisition. In order to overcome these two problems, a Modified Image Based Visual Servoing algorithm and an Extended Kalman Filtering for feature position estimation are developed and applied. In particular, the filtering shows a quite good performance if target's depth information is supplied. A simple procedure for estimating initial target depth is therefore developed and tested. As a result of the application of all the novel approaches proposed, the experimental test campaign shows a remarkable increase in the robustness of the guidance, navigation and control systems.     

考虑在轨运动可靠性的空间机械臂关节力矩优化方法

提出一种考虑在轨运动可靠性的冗余度空间机械臂关节力矩优化方法。首先将机械臂操作空间中点到点的转移任务从笛卡尔空间转换至关节空间,利用七次多项式插值法对各关节变量进行参数化处理,获得粒子群算法的优化控制参数;与传统路径规划方法不同,将机械臂各关节力矩的均值和最小作为粒子群算法优化求解的目标函数;依据该目标函数以及相应优化控制参数,利用粒子群算法对空间机械臂运行轨迹进行优化求解,得到机械臂关节力矩均值和最小的运行路径。仿真实验表明,相比传统路径规划方法及以关节力矩二范数为目标函数的关节力矩优化方法,在降低冗余度空间机械臂关节力矩均值方面,文中方法分别减小了33.57%和10.47%;在降低关节力矩最大值方面,分别减小了43.25%和6.19%。     

空间站机器人最小振动操作动力学控制

提出两种空间站机器人最小振动操作动力学方法。一种是利用空间站灵活操作臂的运动学“自运动”快速消除空间机器人大型柔性机械臂的残余振动，同时使灵活操作臂在工作时不产生使柔性大臂变形和振动的激振力。第二种方法是利用灵活操作臂与空间站和柔性大臂之间的动力学耦合零空间运动进行空间站机器人的无振动操作。推导出空间机器人系统的动力学方程，得到了柔性大臂和灵活操作臂间的作用力与机器人运动之间的关系，基于渐进稳定的控制方法实现机器人的控制，以安装在弹性基础上的平面四自由度机器人进行了仿真验证。