Neural Dynamics for Cooperative Motion Control of Omnidirectional Mobile Manipulators in the Presence of Noises: A Distributed Approach

This paper presents a distributed scheme with limited communications, aiming to achieve cooperative motion control for multiple omnidirectional mobile manipulators(MOMMs).The proposed scheme extends the existing single-agent motion control to cater to scenarios involving the cooperative operation of MOMMs. Specifically, squeeze-free cooperative load transportation is achieved for the end-effectors of MOMMs by incorporating cooperative repetitive motion planning(CRMP), while guiding each individual to desired poses. Then, the distributed scheme is formulated as a time-varying quadratic programming(QP) and solved online utilizing a noise-tolerant zeroing neural network(NTZNN). Theoretical analysis shows that the NTZNN model converges globally to the optimal solution of QP in the presence of noise. Finally, the effectiveness of the control design is demonstrated by numerical simulations and physical platform experiments.

OPTIMAL DYNAMIC LOAD DISTRIBUTION OF MULTIPLE COOPERATING ROBOT MANIPULATORS

For the situation of multiple cooperating manipulators handling a single object,an equilibrium equation is presented in which the manipulator dynamics and control forces/torques are taken into account,and a expression is derived to allow the optimal dynamic load distribution of the combined system can be made.

NEW APPROACHES FOR COMPUTING DYNAMIC LOAD-CARRYING CAPACITY OF MULTIPLE COOPERATING ROBOTIC MANIPULATORS

A novel unified method for computing the dynamic load carrying capacity(DLCC) of multiple cooperating robotic manipulators is developed.In this method,the kinematic constraints and the governing dynamic equations of the multiple robot system are formulated in the joint space by using the method of transference of dependence from one set of generalized coordinates to another,and the virtual work principle,which includes the readily available dynamics and joint torques of individual manipulators,and the dynamic of payload.Based on this dynamic model,the upper limit of the DLCC at any points on a given trajectory is obtained by solving a small size linear programming problem.This method is conceptually straightforward,and it is applicable also to the cases of multi fingered robot hands and multi legged walking machines.

Collision Avoidance of Cooperative Dual Redundant Manipulators

Dual redundant manipulators are extremely useful for tasks in dangerous or space environments, but efficient and real time coordinated control is hard to achieve. Collision avoidance between two cooperative manipulators is vital to the successful applications of dual redundant manipulators. Although methods based on the distance function have been demonstrated simple and efficient, different collision avoidance points can usually produce completely different results and even failure. The paper discussed the choices of collision avoidance points and proposed a novel method for the choosing of those points. The method is testified by simulation results of two redundant planar manipulators.

Inverse kinematics and error analysis of cooperative welding robot with multiple manipulators

Precise welding of the T-joints between aircraft hyperbolic panels and stringers is required. Therefore, a method of solving inverse kinematics equations for a cooperative welding robot with multiple manipulators based on neural networks was investigated. To build an effective Denavit-Hartenberg(DH)model for this robot, sample data was obtained considering the movement ranges of the robot joints.Based on back propagation(BP) and radial basis function(RBF) neural networks, 18 joint sub-spaces were mapped to the workspaces of three manipulators. The high-dimensional and nonlinear inverse kinematics problem was transformed into a multi-input and multi-output prediction model. The results revealed that the prediction model of solving the cooperative welding robot kinematics equations was quite accurate. Moreover, compared with the BP-based model, the calculation process of the RBF-based prediction model was slower, but yielded more accurate predictions.

空间站机械臂人机系统设计与验证

在充分调研国际空间站机械臂人机系统设计的基础上,结合中国空间站机械臂人机协同作业需求,建立了空间站机械臂“管理-设计-验证”全周期人机设计体系,通过人机项目规划、人机功能分配等管理要素,针对性地开展了空间机械臂人机系统详细设计,最后,从仿真分析、地面验证、在轨验证三大方面对人机系统进行了全要素全流程的验证,结果表明空间站机械臂人机系统设计合理,可应用于后续航天员出舱活动,保障航天员出舱活动安全、高效。研究结果将为空间机械臂人机系统设计与验证提供体系借鉴和工程指导。

Compliance motion control of the hydraulic dual-arm manipulator with adaptive mass estimation of unknown object

Given the limited operating ability of a single robotic arm,dual-arm collaborative operations have become increasingly prominent.Compared with the electrically driven dual-arm manipulator,due to the unknown heavy load,difficulty in measuring contact forces,and control complexity during the closed-chain object transportation task,the hydraulic dual-arm manipulator(HDM)faces more difficulty in accurately tracking the desired motion trajectory,which may cause object deformation or even breakage.To overcome this problem,a compliance motion control method is proposed in this paper for the HDM.The mass parameter of the unknown object is obtained by using an adaptive method based on velocity error.Due to the difficulty in obtaining the actual internal force of the object,the pressure signal from the pressure sensor of the hydraulic system is used to estimate the contact force at the end-effector(EE)of two hydraulic manipulators(HMs).Further,the estimated contact force is used to calculate the actual internal force on the object.Then,a compliance motion controller is designed for HDM closed-chain collaboration.The position and internal force errors of the object are reduced by the feedback of the position,velocity,and internal force errors of the object to achieve the effect of the compliance motion of the HDM,i.e.,to reduce the motion error and internal force of the object.The required velocity and force at the EE of the two HMs,including the position and internal force errors of the object,are inputted into separate position controllers.In addition,the position controllers of the two individual HMs are designed to enable precise motion control by using the virtual decomposition control method.Finally,comparative experiments are carried out on a hydraulic dual-arm test bench.The proposed method is validated by the experimental results,which demonstrate improved object position accuracy and reduced internal force.

一种空间双臂机器人有限时间柔顺抓捕策略

提出了一种面向非合作目标捕获的空间双臂机器人有限时间柔顺抓捕策略。首先建立了自由漂浮基空间机械臂以末端执行器位姿自由度为广义坐标表示的末端执行器动力学模型。在此基础上基于全局快速非奇异终端滑模控制理论设计了有限时间轨迹跟踪控制器,实现了末端执行器的有限时间轨迹跟踪控制。进一步采用一种三指末端抓握机构,建立了末端执行机构-目标抓捕位置子系统动力学模型,在该模型基础上基于柔顺控制理论设计了复合柔顺抓握控制策略,解决了末端执行器对目标的柔顺抓握控制。仿真结果表明,所设计的有限时间柔顺抓捕控制策略能够实现空间双臂机器人在有限时间内对翻滚目标的柔顺抓握控制。

Kinematic Analysis of Mobile Manipulator for Measurement and Maintenance in Dangerous Environment

This paper studies the kinematic modeling of a mobile manipulator that consists of 5-DOF manipulator and an autonomous wheeled mobile platform.Then an artificial neural network to realize the coordination motion between manipulator and mobile platform is developed.On the basis of the task specifications,the algorithm determines the appropriate control variables to respond to the well tracking trajectory.The control strategy employed for either subsystem is achieved by using a robust supervised controller.A learning paradigm is used to produce the required reference variables for an overall cooperative behavior of the sys- tem.Simulation results are presented to show the effectiveness of this approach.

Optimal Trajectory Planning of the Dual Arm Manipulator Using DAMM

This paper presents an optimal trajectory planning method of the dual arm manipulator using Dual Arm Manipulability Measure （DAMM）. When the manipulator carries an object from a certain position to the destination, various trajectory candidates could be conskied. TO select the optimal trajectacy from the several candidates, energy, time, and the length of the tmjecttay could be utilized. In order to quantify the carrying effidency of dual-arms, DAMM has been defined and applied for the decision of the optimal path. DAMM is defined as the interaction of the manipulability ellipsoids of the dualarras, while the manipulability measure irdicates the relationship between the joint velocity and the Cartesian velocity for each ann. The cast function for achieving the optimal path is defined as the Summation of the distance to the goal and inverse of this DAMM, which aims to generate the efficient motion to the goal. It is confirmed that the optimal path planning keeps higher manipulability through the short distance path by using computer simulation. To show the effectiveness of this cooperative control algorithm experimentally, a 5-DOF dual-ann robot with distributed controllers for synchronization control has been developed and used for the experiments.

双臂空间机器人闭链系统的协同柔顺控制策略研究

双臂空间机器人对目标的协同操作具有负载能力大、定位精度高的特点,同时存在着闭链运动和控制力约束条件.本文以双臂六自由度空间机器人为研究对象,针对同一目标的搬运操作任务,建立了闭链系统的动力学模型.基于机器人和目标的虚切断铰接结构,以操作臂为刚性运动,协作臂为柔性运动的操作模式,分别设计了关节跟踪控制律和柔顺阻尼控制律.基于实例进行了运动仿真,验证了双臂协同控制算法的有效性.

在轨集群操控关键技术研究进展与展望

对在轨集群操控任务计划相关研究成果进行了综述,并聚焦于在轨集群操控中的集群航天器型谱化设计、群体行为建模与智能涌现、集群自组网、集群智能感知、集群自主任务规划与分布式自主协同控制等关键技术,分别对这些关键技术进行了系统梳理与分类阐述,总结了其发展趋势;提出了一套面向大型空间设施在轨建造的集群操控体系能力框架。有望为未来大型空间设施在轨建造及集群操控发展提供借鉴和参考。

基于DMPC的多机械臂协同操作控制

针对多机械臂协作搬运中的编队稳定性和协同控制优化问题,提出了一种基于迭代线性二次型调节器(iLQR)的分布式预测控制算法(DMPC)。首先,对机械臂动力学模型中的末端接触力进行受力分析,从而得到机械臂的状态空间模型。其次,通过定义多机械臂系统的刚性编队约束来维持搬运途中编队结构的稳定。然后,将编队约束整合到DMPC的代价函数中用于建立约束最优化问题,并利用iLQR算法求解优化问题。最后,仿真实验验证了所提算法的有效性。

Adaptive Sliding-Mode Disturbance Observer-Based Nonlinear Control for Unmanned Dual-Arm Aerial Manipulator Subject to State Constraints

The unmanned dual-arm aerial manipulator system is composed of a multirotor unmanned aerial vehicle(UAV)and two manipulators.Compared to a single manipulator,dual-arm always provides greater°exibility and versatility in both goods delivery and complex task execution.However,the practical application of the system is limited due to nonlinearities and complex dynamic coupling behavior between the multirotor and the manipulator,as well as the one between the inner and outer loop of the multirotor.In this paper,a holistic model of the dual-arm aerial manipulator system is¯rst derived with complete model information.Subsequently,an adaptive sliding-mode disturbance observer(ASMDO)is proposed to handle external disturbances and unmeasurable disturbances caught by unmeasurable angular velocity and acceleration of the manipulators.Moreover,for safety concerns and transient performance requirements,the state constraints should be guaranteed.To this end,an auxiliary term composed of constrained variable signals is introduced.Then,the performance of the designed method is proven by rigorous analysis.Finally,the proposed method is validated through two sets of simulation tests.

漂浮基机械臂系统耦合动力学与解耦控制方法

在执行空间任务过程中,漂浮基机械臂系统内部的动力学耦合现象使得基体姿态调整和机械臂末端定位与控制问题变得更加复杂。综合考虑多种空间漂浮基机械臂系统共性特征,关注机械臂与基体耦合规律,建立统一的耦合动力学模型,并利用整个系统的非完整性特征和耦合特点,对特定系统设计解耦控制规律。通过控制机械臂关节主动运动实现基体位姿可控和机械臂末端任务不受制约的目的。结果表明,通过合理设置控制参数,在解空间存在的情况下,能够达到漂浮基体与机械臂末端协调运动的目的。

双绳驱动空中机械臂协同搬运控制研究

为解决双绳驱动空中机械臂协同搬运时的接触控制问题,提出了一种基于非奇异快速终端滑模的阻抗控制策略。首先,考虑绳驱动机制的柔性效应,建立计及关节柔性的双机协同系统动力学模型,并推导出任务空间内的阻抗方程。然后,设计协同阻抗控制策略,借助非奇异快速终端滑模面来加快系统状态量的收敛速度,利用幂次函数削弱输出力矩抖振效应。同时,在Lyapunov框架下分析了所设计控制器的稳定性。最后,通过控制器性能比较仿真和协同搬运仿真对所提控制策略的有效性进行了验证。结果表明,所提控制器响应速度快、控制精度高及稳定性好,能够有效抑制系统抖振。

基于多相机的空间机械臂视觉系统

视觉系统是空间机械臂的重要组成部分,空间机械臂除开环控制外的所有工作模式都不能离开视觉系统的引导和辅助而独立实现。文章以建立满足空间机械臂实际应用需求的视觉系统为目标,提出通过分布在不同空间位置的多个相机的协同工作扩展并增强视觉系统的监视和测量能力,并从系统组成、工作模式、测量方式等多方面完成空间机械臂视觉系统方案设计。仿真试验结果表明,目标三维位姿的测量误差与视觉标记点检测结果的误差近似成线性关系,视觉标记点检测的准确性对目标位姿测量的精度具有重要影响。室内环境试验结果表明,在视觉系统的引导下机械臂能够自主完成对目标的定位和捕获,视觉系统满足空间机械臂大范围运动和精准操作任务的应用需求。

两柔性机器人协调操作的动力学模型及其逆动力学分析

柔性机器人动力学是当前机器人研究的热点，而其协调操作问题目前仍为空白．本文首次建立了柔性机器人协调操作刚性负载的动力学模型，利用有限元法和Ｌａｇｒａｎｇｅ方程，在柔性机器人协调操作的运动学和动力学协调约束条件基础上，推导出系统的动力学方程，提出了其逆动力学问题的解决方案。

基于多Agent可重构机器人控制方法的研究

根据多 Agent理论中的协商、合作机制和可重构机器人结构的分布性 ,将集中式的机器人控制分配到一组关节 Agent中 ,每个 Agent控制机器人的一个关节 ,使用这种分布式方法 ,得到了一种新的通用机器人控制方法 ,即将关节机器人的复杂控制转换为多个简单子系统的控制 ,该方法可应用于具有不同构型的机器人系统 ,特别适用于可重构模块化机器人的控制。利用微分运动理论提出了一种新的决策方法 ,便于 Agent之间的合作与协商。

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。