Flexible Bio-tensegrity Manipulator with Multi-degree of Freedom and Variable Structure

Conventional manipulators with rigid structures and sti ness actuators have poor flexibility,limited obstacle avoidance capability,and constrained workspace.Some developed flexible or soft manipulators in recent years have the characteristics of infinite degrees of freedom,high flexibility,environmental adaptability,and extended manipulation capability.However,these existing manipulators still cannot achieve the shrinking motion and independent control of specified segments like the animals,which hinders their applications.In this paper,a flexible bio-tensegrity manipulator,inspired by the longitudinal and transversal muscles of octopus tentacles,was proposed to mimic the shrinking behavior and achieve the variable motion patterns of each segment.Such proposed manipulator uses the elastic spring as the backbone,which is driven by four cables and has one variable structure mechanism in each segment to achieve the independent control of each segment.The variable structure mechanism innovatively contains seven lock-release states to independently control the bending and shrinking motion of each segment.After the kinematic modeling and analysis,one prototype of such bionic flexible manipulator was built and the open-loop control method was proposed.Some proof-of-concept experiments,including the shrinking motion,bending motion,and variable structure motion,were carried out by controlling the length of four cables and changing the lock-release states of the variable structure mechanism,which validate the feasibility and validity of our proposed prototype.Meanwhile,the experimental results show the flexible manipulator can accomplish the bending and shrinking motion with the relative error less than 6.8%through the simple independent control of each segment using the variable structure mechanism.This proposed manipulator has the features of controllable degree-of-freedom in each segment,which extend their environmental adaptability,and manipulation capability.

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.

OPTIMAL CONTROL OF THE FLEXI-BLE LINK MANIPULATOR WITH CONTROLLABLE LOCAL DEGREES OF FREEDOM

Although flexible manipulators own many potential advantages, one of their major disadvantages is the deterioration of the end-effector accuracy due to the flexibility. Therefore, how to reduce vibration is a significant problem. Inspired by the observation on the motion behaviors of animals, a new idea of decreasing motion deflection of the flexible manipulator is suggested. The concept of controllable local degrees of freedom is proposed and analyzed. By way of optimizing local motion provided by the controllable local degrees of freedom, the end-effector deflection of the flexible manipulator can be effectively decreased through dynamic coupling. The corresponding optimal method for vibration control of the flexible manipulator is put forward. The kinematic simulation is carried ant on a three-link flexible manipulator The corresponding results verify the feasibility of this method.

Impact vibration reduction for flexible manipulators via controllable local degrees of freedom

When performing operation tasks, the interaction between a flexible manipulator and a grasped object usually results in an impact. In this paper, a new way is suggested to alleviate impact vibration of a flexible manipulator via its structural characteristic when capturing a moving object. Controllable local degrees of freedom are introduced to the topological structure of the flexible manipulator, and used as an effective tool to combat impact vibration through dynamic coupling. A corresponding method is put forward to reduce impact vibration responses of the flexible manip- ulator via the controllable local degrees of freedom. By planning motion of the controllable local degrees of freedom, appropriate control force can be constructed to increase the modal damping and stiffness and eliminate the exciting force simultaneously, thereby reducing impact vibration responses of the flexible manipulator. Simulations are conducted and results are shown to prove the presented method.

Parameter optimization of controllable local degree of freedom for reducing vibration of flexible manipulator

Parameter optimization of the controllable local degree of freedom is studied for reducing vibration of the flexible manipulator at the lowest possible cost. The controllable local degrees of freedom are suggested and introduced to the topological structure of the flexible manipulator, and used as an effective way to alleviate vibration through dynamic coupling. Parameters introduced by the controllable local degrees of freedom are analyzed and their influences on vibration reduction are investigated. A strategy to optimize these parameters is put forward and the corresponding optimization method is suggested based on Particle Swarm Optimization （PSO）. Simulations are conducted and results of case studies confirm that the proposed optimization method is effective in reducing vibration of the flexible manipulator at the lowest possible cost.

多自由度柔性机械臂非线性连续时变反馈控制方法

针对当前多自由度柔性机械臂控制过程中,机械臂定位控制系数选择合理性较低,导致多自由度柔性机械臂控制时延较长且运动轨迹与预设轨迹存在较大差异的问题,提出多自由度柔性机械臂非线性连续时变反馈控制方法。将拉格朗日算子作为计算基础,以能量的方式构建多自由度柔性机械臂动力学模型。考虑到机械臂的负载状态,计算机械臂的重力矩,识别机械臂非线性连续时变反馈控制参数。设定非线性连续时变反馈控制规则,构建机械臂非线性控制器,实现机械臂定位控制。构建实验环节,实验结果表明:该方法可有效提升机械臂运动轨迹与预设轨迹的一致性,缩短机械臂定位控制时延,进一步提升机械臂应用效果。

六自由度机械臂位置误差分析与结构优化

为了研究六自由度液压机械臂在重载工况下连杆结构的微小弹性变形对末端位置精度的影响,利用ADAMS软件对六自由度液压机械臂进行了刚性体及柔性体的动力学仿真分析,获取各连杆在最差工作条件下的载荷分布,利用ANSYS软件对各连杆进行了结构分析,根据分析结果得出了连杆结构的弹性变形对六自由度机械臂末端位置误差的影响程度,并对各连杆机械结构进行了优化。

多自由度柔性机械手的控制系统实现

本文介绍了一种基于西门子PLC和气动控制设计的多自由度柔性搬运机械手控制系统,实现了柔性自动生产线中两个位置的物料抓取和传送,结构简单、性能可靠、成本低廉,有较强的推广价值。

N自由度柔性机械臂通用的动力学建模方法研究

针对多自由度柔性机械臂动力学建模过程复杂的问题,提出一种适用于N自由度柔性臂刚柔耦合动力学建模的通用方法。该方法基于拉格朗日方程(Lagrange)和假设模态法(ASM),归纳推导得到了N自由度柔性机械臂动力学模型的最简通用符号表达式,根据该建模方法开发了"N-DOF柔性机械臂动力学方程符号计算软件";最后以两自由度柔性机械臂为例进行位置跟踪控制实验,用开发的软件自动生成了动力学模型,并搭建了实物模型进行对比验证,结果具有一致性,表明了该建模方法的正确性。与传统建模方法相比,该建模方法可减少90%以上计算时间,极大降低了建模过程的复杂性,同时对多自由度柔性臂动力学建模也具有通用性。

基于气动人工肌肉机械手的研究

目前机械手普遍使用气缸,虽然可以实现对操作位置和作用力的有效控制,但是气缸响应速度慢,柔顺性差,不适合应用在医疗和福利领域。用柔性执行器气动人工肌肉为新型执行器构建气动人工肌肉机械手系统,特别是多自由度的平台,是气动方向一项新的研究内容。文章在现有研究工作基础上,对气动机械手系统进行研究,对系统的结构、电气路设计进行了详细描述。机械手系统的可行性与有效性得到了实验的证明。

排爆机器人五自由度操作臂灵活度优化方法

针对传统机器人操作臂灵活度优化方法忽略了获取机器人雅克比矩阵奇异值,导致操作臂灵活度过程效率降低,排爆准确度得不到明显提高。提出排爆机器人五自由度操作臂灵活度优化方法。首先对操作臂构造动力学模型,获取拉格朗日动力学方程及相关参数,对姿态概率系数和可操作度进行描述。以五自由度操作臂工作球为基础分析操作臂姿态概率系数;针对操作臂的可操作度,通过排爆机器人雅克比矩阵奇异值实现构造,建立操作臂在工作空间内的灵活度优化目标函数,通过遗传算法对目标函数进行求解,实现排爆机器人操作臂灵活度的优化。实验结果表明,所提方法优化性能佳,可有效提高操作臂灵活度。

柔性冲压生产线自动输送设备设计

介绍柔性冲压生产线自动输送系统整机构成。采用自动送料、上料小车将板片料通过气动自动分离吸盘手抓取至输送线上,通过抹油机构、三自由度机械手、自动提升装置等送入冲压成型液压机构;利用无动力传送机构降低系统能耗。经生产调试运行,该系统运行安全、稳定。