具有冗余度的三分支空间机器人的运动学分析

基于例如空间站等恶劣的应用环境,研制了一种具有冗余度的三分支空间机器人。该机器人的一个分支的末端可以和基座固联,另外两个分支可以进行控制来完成各种作业。在宇航员不在的情况下,该机器人可以代替宇航员对科学实验载荷进行操作。利用旋量理论对机器人的逆运动学进行了分析,并建立了统一的数学模型给出了其运动学优化、动力学优化以及容错控制的理论基础。基于球腕的封闭解,提出了一个简单的逆运动学模型。最后,通过计算机结果演示验证了所提出逆运动学模型的有效性。     

打磨机操作臂运动学仿真研究

采用D—H方法建立打磨机操作臂的运动学方程,并讨论该操作臂的运动学问题。首次将MATLAB中的Robotics Toolbox命令与编写的MATLAB程序相结合应用于新型打磨机操作臂正运动学、逆运动学仿真,并对正、逆运动学以及空间轨迹进行了实例仿真。通过仿真观察到操作臂各个关节的运动并得到了所需的数据,说明操作臂建模以及所设计参数的合理性和运动算法的正确性,为打磨机的动力学、控制和规划的研究提供了可靠的参数。     

虚拟机械臂和ADAMS在空间机械臂研究中的应用

首先阐述了虚拟机械臂的概念。其次利用虚拟机械臂技术和ADAMS软件分析空间机械臂的工作空间、逆运动学问题。最后利用ADAMS/Controls模块将ADAMS的动力学模型与Mat-lab的控制模型结合起来,对空间机械臂进行控制仿真。仿真结果表明,虚拟机械臂技术和AD-AMS的结合使用为空间机械臂的研究带来极大的方便,ADAMS和Matlab联合仿真的分析方法是有效的。     

惯性参数不确定的自由漂浮空间机器人自适应控制研究

针对自由漂浮空间机器人系统惯性参数不确定问题,提出一种笛卡儿空间内的自适应轨迹跟踪控制方法。采用扩展机械臂模型建立了自由漂浮空间机器人关节空间动力学方程,进而推导笛卡儿空间中的自由漂浮空间机器人动力学方程。在基于逆动力学法的自由漂浮空间机器人自适应控制器设计中,利用标称控制器离线固定控制参数与补偿控制器在线补偿方法,既可以保证惯量矩阵可逆,又可以使控制参数实时估计。采用Lyapunov方法的稳定性分析表明系统是稳定且渐进收敛的。最后,应用该控制方法对两杆平面自由漂浮空间机器人进行了仿真研究。仿真结果显示自由漂浮空间机器人末端执行器在笛卡儿空间具有良好的轨迹跟踪能力。     

Failure treatment strategy and fault-tolerant path planning of a space manipulator with free-swinging joint failure

Aiming at a space manipulator with free-swinging joint failure, a failure treatment strategy and fault-tolerant path planning method is proposed in this paper. This method can realize failure treatment of a space manipulator with free-swinging joint failure through determination of the optimal locked joint angle and dynamics model reconfiguration. Fault-tolerant path planning is realized by the establishment of the degraded workspace with integrated kinematics performance (DWWIKP) and an improved A-Star (A1) algorithm. This paper has the following contributions. The determination of the optimal locked joint angle can ensure that the manipulator is able to continue follow-up tasks while maximizing the workspace of the manipulator after locking the fault joint. Underactuated control of a high degree-of-freedom (DOF) manipulator can be effectively solved through dynamics model reconfiguration. The analysis process of the dynamics coupling relationship can be applied to cases where the active joint and the passive joint are parallel or perpendicular to each other. The establishment of the DWWIKP can demonstrate the kinematics performance of the manipulator in both joint space and operation space comprehensively. The improved A1 algorithm based on the integrated kinematics performance index (IKPI) can search a fault-tolerant task trajectory that satisfies the requirements of reachability and the overall kinematics performance simultaneously. The method proposed in this paper is verified by a 7-DOF manipulator, and it is available to any DOF manipulator with free-swinging joint failure.     

参数不确定空间机械臂系统的增广自适应控制

讨论了载体位置与姿态均不受控制的漂浮基两杆空间机械臂系统的控制问题,为此对系统的运动学、动力学作了分析。结果表明 :结合系统动量守恒及动量矩守恒关系得到的系统广义Jacobi关系、以及系统的动力学方程将为系统惯性参数的非线性函数。证明了借助于增广变量法可以将增广广义Jacobi矩阵以及系统动力学方程表示为一组适当选择的惯性参数的线性函数。在此基础上,给出了系统参数未知时,空间机械臂末端抓手跟踪惯性空间期望轨迹的增广自适应控制方案。通过仿真运算,证实了方法的有效性。     

Vibration Reduction of Open-chain Flexible Manipulators by Optimizing Independent Motions of Branch Links

In order to suppress vibration in flexible manipulators, a new type of manipulator mechanism with controllable local degrees of freedom is proposed. This mechanism consists of a main chain and some branch links. The main chain is of a flexible open-chain configuration with an end-effector installed at its tip, and the rigid branch links are able to perform active movements. It is proved by kinematics and dynamic analysis that, the branch links bear no direct kinematic relation to the main chain, but their independent motions can strongly affect the dynamic behavior and performance of the flexible manipulator. Then comes a new idea of suppressing vibration, in which independent motions of the branch links are used to suppress the undesired vibration of the flexible main chain through dynamic coupling. On this basis, an optimal method for reducing vibration of flexible manipulators is proposed. Finally, the effectiveness of this method is verified by numerical simulations.     

基于RBF网络的机械手臂逆问题的求解

机械手臂的研究,要涉及到机械手运动学逆问题,即由已知机械手末端的位姿求出机械手各个关节的关节量。逆问题的解析法存在着无解的问题,数值解法计算量太大。应用RBF神经网络良好的非线性逼近能力,对机械手臂的运动学逆问题进行非线性逼近,利用训练好的网络可以精确,快速地求出逆问题的解,且在多解情况下可以求得最优解。     

Adaptive fuzzy terminal sliding mode control for the free-floating space manipulator with free-swinging joint failure

Space manipulator with free-swinging joint failure simultaneously contains kinematic and dynamic coupling relationships, so it belongs to a new underactuated system. To allow the manipulator to carry on tasks, an effective robust underactuated control method for the space manipulator with free-swinging joint failure is studied in this paper. Considering the effect of model uncertainty and joint torque disturbance, a robust underactuated control system based on the Terminal Sliding Mode Controller (TSMC) is designed, but two drawbacks are discussed: (A) Robustness depraves with eliminating chattering. (B) Control parameters are difficult to be determined under unknown uncertainty and disturbance. To improve the TSMC, the adaptive fuzzy controller is introduced to estimate the real effect of unknown uncertainty and disturbance according to deviations of sliding mode and its reaching law. The estimated result is directly compensated into active joints torque. In simulation, the space manipulator with free-swinging joint executes tasks based on the TSMC and the Adaptive Fuzzy Terminal Sliding Mode Controller (AFTSMC) respectively. Same tasks can be finished with smaller joints torque and stronger robustness based on the AFTSMC. Therefore, AFTSMC can serve as an effective robust control method for the space manipulator with free-swinging joint failure under unknown model uncertainty and torque disturbance.     

基于模糊PID算法的六自由度并联机构控制研究

针对六自由度并联机构难以实现高精度及快速响应的问题,分析六自由度并联机构模型,提出基于模糊PID的六自由度并联机构的控制算法.介绍了六自由度并联机构的运动学反解模型及机械系统模型;在此基础上确定模糊算法的模糊语言变量、隶属函数和模糊规则,完成了六自由度并联机构模糊PID控制器的设计.针对一组PID控制参数进行了仿真和实验,结果表明,加入模糊算法的PID控制提高了系统的动态响应特性及运动精度.     

一个超冗余度移动操作臂机器人系统的实现与运动控制

冗余度或超冗余度移动操作臂机器人可在空间站上为宇航员提供很大的帮助.对一个超冗余度移动操作臂机器人系统的设计和实现作了介绍,这个系统由一个8自由度的模块机器人和一个1自由度的电机驱动的导轨组成;对该系统的逆运动学解法进行了讨论,提出了一种基于避关节极限与位形优化的简化逆运动学控制方法;并提供了仿真和实验结果.     

Postcapture stabilization of space robots considering actuator failures with bounded torques

Space robotics is regarded as one of the most impressing approaches for space debris removal missions. Due to the residual momentum of debris, it is essential to stabilize the base rapidly after capture. This paper presents a novel control strategy for stabilization of a space robot in postcapture considering actuator failures and bounded torques. In the control strategy, the motion of the manipulator is not regarded as a disturbance to the base; in contrast, it is utilized to compensate for the limitation of the control torques by means of an inverse dynamical model of the system. Different scenarios where actuators are external mechanisms or momentum exchange devices have been carried out, and for actuator failures, both single- and two-actuator failures have been considered. Regarding to the performance of actuators, control torques are bounded. In cases that either single or two actuators have failed, the base can be stabilized kinematically when actuators are external mechanisms, but can only be stabilized dynamically when only momentum exchange devices are used. Finally, a space robot with a seven-degree-of-freedom manipulator in postcapture is studied to verify the validity and feasibility of the proposed control scheme. Simulation results show that the whole system can be stabilized rapidly.     

冗余铺丝机械手自运动流形分析及优化

针对传统位姿分离式铺丝机械手灵活性不足的特点,为了提高航空复合材料铺丝过程的灵活性和避障碍能力,提出一种位姿耦合式冗余铺丝机械手自运动流形的新算法。由于冗余铺丝机械手各关节之间的强耦合性增加了逆解的求解难度,该算法将冗余铺丝机械手的关节逆解分解为已知的Paden-Kahan旋量子问题以及由位置关节组成的特殊旋量子问题,并针对特殊旋量子问题进行求解得到冗余铺丝机械手全部逆解,这样相对于位姿分离式解法有效提高了冗余铺丝机械手逆解的求解效率以及求解直观性。由于冗余铺丝机械手的逆解呈现出流形的结构,所以根据冗余铺丝机械手自运动流形的多维特性,将冗余铺丝机械手的自运动流形分别映射到位置关节空间和姿态关节空间得到其三维仿真曲线。由于冗余铺丝机械手逆解流形中的优化流形在实际控制中更具应用价值,所以在铺丝机械手末端执行器沿芯模轨迹运动速度平稳的前提下为了使机械手各关节速度变化最小,提出以冗余铺丝机械手关节速度组成的约束泛函为目标得到相应的运动学优化流形,并为后续的最优控制奠定了基础。最后以某型号飞机S形进气道为例验证了所提方法的可行性。     

轮腿式火星探测机器人的多目标协同控制

火星探测任务要求机器人具有对未知的不规则地形的自适应能力和动态稳定性。针对轮腿式火星探测机器人,提出了基于运动学反解模型、车体姿态和轮壤接触力的多目标协同控制策略。通过车体姿态调整运动学建模、一阶低通滤波及腿部阻抗控制算法和基于腿部运动危险系数的重心高度调整算法,实现了车体姿态的跟踪控制、轮壤恒力接触控制和重心最优高度控制,提升了轮腿机器人在非结构地形中的自适应能力、运动稳定性及腿部运动空间的安全性。在MATLAB和UG中建立联合仿真模型,验证了控制策略的有效性。     

基于干扰观测器的柔性空间机器人在轨精细操作控制方法

由于强非线性、强耦合和强时变等特征,柔性空间机器人的稳定精细控制问题一直是一个重大挑战。轻质小型化机器人受空间及重量限制,其关节柔性通常不可忽略,这部分柔性主要是由谐波减速器和力矩传感器的柔性造成的。传统的运动学控制在空载时能保持稳定,但是对大负载、快速运动时的适应性差,严重时机械臂抖动剧烈甚至发散。针对以上特征,提出了一种基于非线性干扰观测器和动力学极点配置的柔性空间机器人在轨精细操作控制方法。仿真实验证明,该方法可以有效地抑制柔性激振,保证响应的快速性和准确性,同时有较好的鲁棒性,能够适应不同类型扰动的影响和末端环境柔顺控制的要求,对工程应用具有一定的参考意义。     

带有空间机械臂的航天器系统惯性参数辨识

针对航天器惯性参数在轨辨识问题,文章以空间机械臂为研究对象,建立了带有空间机械臂的航天器系统动力学模型,并进行了空间机械臂的动力学分析。通过规划一种复杂的空间机械臂的运动轨迹,对机械臂各关节施加合适激励的方法,使空间机械臂做充分可变构型运动。该运动会改变航天器系统的惯性分布,从而引起航天器系统速度变化。然后,通过ADAMS(Automatic Dynamic Analysis of Mechanical Systems,机械系统动力学自动分析)软件建模测量这些速度变化,计算出空间机械臂的惯性变化,进而基于动量和动量距守恒的方法建立线性回归方程。最后,通过应用递推最小二乘法解线性回归方程组,辨识出了航天器的惯性参数。仿真分析结果表明了所辨识的航天器惯性参数的有效性和准确性。     

自由漂浮空间机器人点到点避奇异运动控制方法

针对具有冗余机械臂的自由漂浮空间机器人（Free Floating Space Robot, FFSR）点到点避免奇异性规划和控制问题,提出了一种冗余FFSR的点到点避免奇异控制方法。首先,该方法基于离散状态依赖李卡提方程（DSDRE）控制器设计方法,利用FFSR的动力学和运动学方程实现了FFSR系统方程的伪线性重构;然后,基于伪线性重构系统及DSDRE状态调节器设计方法实现了FFSR的关节角速度和末端位姿的同时跟踪控制;其次,根据跟踪控制器对FFSR广义雅克比矩阵（GJM）行满秩的设计要求,定义FFSR的奇异性判别依据,构造了避奇异约束函数;再次,由于冗余FFSR系统具有多逆运动学解特点,考虑关节角及关节角速度约束,结合避奇异约束函数设计了FFSR的期望轨迹在线规划器,进一步将设计的跟踪控制器与规划器相结合提出了冗余FFSR末端点到点避奇异运动控制方法。最后,为验证所提方法的有效性同时考虑简化计算,采用平面4连杆FFSR模型进行数值仿真,仿真结果表明所提点到点避奇异运动控制方法能够有效实现冗余FFSR系统的点到点避奇异运动。     

一种基于旋量理论的自动钻铆机调姿反解算法

运动学反解是实现机床运动控制的技术基础,也是提高运动精度的技术保证。根据飞机装配自动化钻铆的需求分析,以龙门式自动钻铆机为研究对象,基于旋量理论建立其运动学模型。采用Paden-Kalan子问题模型和自动钻铆机上下末端执行器的几何关系相结合的方法,提出了一种基于旋量理论的自动钻铆机运动学反解算法,并在CATIA中的DMU模块下对算法进行算例验证。结果表明:基于旋量理论的运动学反解算法正确,为自动钻铆机的运动控制提供了理论基础。     

Analysis of reaction torque-based control of a redundant free-floating space robot

Owing to the dynamics coupling between a free-floating base and a manipulator,the non-stationary base of a space robot will face the issue of base disturbance due to a manipulator's motion.The reaction torque acted on the satellite base's centroid is an important index to measure the satellite base's disturbance.In this paper,a comprehensive analysis of the reaction torque is made,and a novel way to derive the analytical form of the reaction torque is proposed.In addition,the reaction torque null-space is derived,in which the manipulator's joint motion is dynamically decoupled from the motion of the satellite base,and its novel expression demonstrates the equivalence between the reaction torque null-space and the reaction null-space.Furthermore,the reaction torque acted as an optimization index can be utilized to achieve satellite base disturbance minimization in the generalized Jacobian-based end-effector Cartesian path tracking task.Besides,supposing that the redundant degrees of freedom are abundant to achieve reaction torque-based active control,the reaction torque can be used to realize satellite base attitude control,that is,base attitude adjustment or maintenance.Moreover,because reaction torque-based control is a second-order control scheme,joint torque minimization can be regarded as the optimization task in reaction torque-based active or in-active control.A real-time simulation system of a 7-DOF space robot under Linux/RTAI is developed to verify and test the feasibility and reliability of the proposed ideas.Our extensive empirical results demonstrate that the corresponding analysis about the reaction torque is correct and the proposed methods are feasible.     

主被动复合驱动空间探测柔性伸杆机构的参数匹配

基于主被动复合驱动的思想提出一种大伸展/收拢比、高载荷/自重比的新型伸缩式伸杆机构,以满足微纳探测器的实际应用需求,用于支撑各类探测载荷远离航天器本体,避免本体剩磁对空间待测信号的干扰,保证探测数据的准确性。首先,探索描述被动驱动源（弹簧铰链）的力矩驱动特性;然后,分析柔性伸杆的弯曲、扭转、压平和卷曲等力学性能。在此基础上,结合建立的柔性伸杆伸展速度、负载动能、弹簧铰链势能及主动驱动（电动机）力矩等参数的能量流约束方程,进行主、被动驱动和柔性伸杆的参数匹配研究;最后,利用有限元软件仿真和样机平台实验验证了参数匹配的合理性。仿真与实验结果表明,针对主被动复合驱动的空间探测柔性伸杆机构,通过合理的参数匹配,可实现柔性伸杆无褶皱地平稳伸展和收拢,为后续的机构设计和控制方案奠定了基础。