A Review on Cable-driven Parallel Robots

Cable-driven parallel robots(CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several advantages, including larger workspaces, higher payload-to-weight ratio and lower manufacturing costs rather than rigid-link robots. In this paper, the history of the development of CDPRs is introduced and several successful latest application cases of CDPRs are presented. The theory development of CDPRs is introduced focusing on design, performance analysis and control theory. Research on CDPRs gains wide attention and is highly motivated by the modern engineering demand for large load capacity and workspace. A number of exciting advances in CDPRs are summarized in this paper since it is proposed in the 1980 s, which points to a fruitful future both in theory and application. In order to meet the increasing requirements of robot in different areas, future steps foresee more in-depth research and extension applications of CDPRs including intelligent control, composite materials, integrated and reconfigurable design.

可重构3-RRR并联机器人的“点对点”路径规划

通过拓扑重构,可以提高并联机器人的静刚度、故障修复等性能,但机器人重构之后能否到达任意指定的位姿且不经过奇异位形,尚无定论。为此,以可重构3-转动副转动副转动副(3-revolute-joint,revolute-joint,revolute-joint,3-RRR)并联机器人为研究对象,提出了一种能够实现“点对点”路径跟踪的规划算法。首先,建立了机构重构之前的反向运动学模型,据此确定了6组重构序列。接着,构建了一种“四步”规划算法,适用于任意自由度的可重构并联机器人的“点对点”路径跟踪,具有直观的几何解释,并且能够消除全部的奇异位形;通过算例验证了规划算法的有效性。然后,基于螺旋理论,计算出各组参量下的输入、输出和局部传递指标值,据此,确定了重构序列下的最优输入参量。最后,将“点对点”路径规划算法推广至连续路径规划的情形。

Comparison of internal force antagonism between redundant cable-driven parallel robots and redundant rigid parallel robots

The internal force antagonism(IFA)problem is one of the most important issues limiting the applications and popularization of redundant parallel robots in industry.Redundant cable-driven parallel robots(RCDPRs)and redundant rigid parallel robots(RRPRs)behave very differently in this problem.To clarify the essence of IFA,this study first analyzes the causes and influencing factors of IFA.Next,an evaluation index for IFA is proposed,and its calculating algorithm is developed.Then,three graphical analysis methods based on this index are proposed.Finally,the performance of RCDPRs and RRPRs in IFA under three configurations are analyzed.Results show that RRPRs produce IFA in nearly all the areas of the workspace,whereas RCDPRs produce IFA in only some areas of the workspace,and the IFA in RCDPRs is milder than that RRPRs.Thus,RCDPRs more fault-tolerant and easier to control and thus more conducive for industrial application and popularization than RRPRs.Furthermore,the proposed analysis methods can be used for the configuration optimization design of RCDPRs.

Parallel Manipulators Applications—A Survey

This paper presents the comparison between serial and parallel manipulators. Day by day, the applications of the parallel manipulator in various field is become apparent and with a rapid rate utilized in precise manufacturing, medical science and in space exploration equipments. A parallel manipulator can be defined as a closed loop kinematic chain mechanism whose end effector is linked to the base by several independent kinematic chains. The classification of various parallel manipulators is presented herewith. The prime focus of the paper is to realize the parallel manipulators applications for industry, space, medical science or commercial usage by orienting manipulator in the space at the high speed with a desired accuracy.

Motion Planning for a Cable-Driven Lower Limb Rehabilitation Robot with Movable Distal Anchor Points

This article introduces a cable-driven lower limb rehabilitation robot with movable distal anchor points(M-CDLR).The traditional cable-driven parallel robots(CDPRs)control the moving platform by changing the length of cables,M-CDLR can also adjust the position of the distal anchor point when the moving platform moves.The M-CDLR this article proposed has gait and single-leg training modes,which correspond to the plane and space motion of the moving platform,respectively.After introducing the system structure configuration,the generalized kinematics and dynamics of M-CDLR are established.The fully constrained CDPRs can provide more stable rehabilitation training than the under-constrained one but requires more cables.Therefore,a motion planning method for the movable distal anchor point of M-CDLR is proposed to realize the theoretically fully constrained with fewer cables.Then the expected trajectory of the moving platform is obtained from the motion capture experiment,and the motion planning of M-CDLR under two training modes is simulated.The simulation results verify the effectiveness of the proposed motion planning method.This study serves as a basic theoretical study of the structure optimization and control strategy of M-CDLR.

State-of-the-art on theories and applications of cable-driven parallel robots

Cable-driven parallel robot(CDPR)is a type of high-performance robot that integrates cable-driven kinematic chains and parallel mechanism theory.It inherits the high dynamics and heavy load capacities of the parallel mechanism and significantly improves the workspace,cost and energy efficiency simultaneously.As a result,CDPRs have had irreplaceable roles in industrial and technological fields,such as astronomy,aerospace,logistics,simulators,and rehabilitation.CDPRs follow the cutting-edge trend of rigid-flexible fusion,reflect advanced lightweight design concepts,and have become a frontier topic in robotics research.This paper summarizes the kernel theories and developments of CDPRs,covering configuration design,cable-force distribution,workspace and stiffness,performance evaluation,optimization,and motion control.Kinematic modeling,workspace analysis,and cable-force solution are illustrated.Stiffness and dynamic modeling methods are discussed.To further promote the development,researchers should strengthen the investigation in configuration innovation,rapid calculation of workspace,performance evaluation,stiffness control,and rigid-flexible coupling dynamics.In addition,engineering problems such as cable materials,reliability design,and a unified control framework require attention.

Cable-Driven Parallel Robot Workspace Identification and Optimal Design Based on the Upper Limb Functional Rehabilitation

An assessment of the human motion repeatability for three selected Activities of Daily Living(ADL)is performed in this paper.These exercises were prescribed by an occupational therapist for the upper limb rehabilitation.The movement patterns of five participants,recorded using a Qualisys motion capture system,are compared based on the Analysis of Variance(ANOVA)method.This survey is motivated by the need to find the appropriate task workspace of a 6-degrees of freedom cable-driven parallel robot for upper limb rehabilitation,which is able to reproduce the three selected exercises.This comparison is performed to justify,whether or not,there is enough similarity between the participants’gestures,and so a single reference trajectory can be adopted as the robot-prescribed workspace.Using the results of the comparative study,an optimization process of the sought robot design is carried out,where the structure size and the cable tensions simultaneously minimized.

Linear quadratic optimal controller for cable-driven parallel robots

In recent years, various cable-driven parallel robots have been investigated for their advantages, such as low structural weight, high acceleration, and large work- space, over serial and conventional parallel systems. However, the use of cables lowers the stiffness of these robots, which in turn may decrease motion accuracy. A linear quadratic （LQ） optimal controller can provide all the states of a system for the feedback, such as position and velocity. Thus, the application of such an optimal controller in cable-driven parallel robots can result in more efficient and accurate motion compared to the performance of classical controllers such as the proportional-integral-derivative controller. This paper presents an approach to apply the LQ optimal controller on cabledriven parallel robots. To employ the optimal control theory, the static and dynamic modeling of a 3-DOF planar cable-driven parallel robot （Feriba-3） is developed. The synthesis of the LQ optimal control is described, and the significant experimental results are presented and discussed.

并联腿机构在四足/两足可重组步行机器人中的应用

将并联腿机构用于助残步行机器人,可大大提高步行机器人的载重/自重比,从而节省能源,延长行走时间。为此提出并联腿机构四足步行机器人。四足稳定性好,安全性高,但是上下楼梯或台阶时座椅有较大的倾斜。为了解决这一问题,提出一种四足/两足可重组并联腿机构步行机器人。在一般路面采用四足行走,消除使用者乘坐两足步行机器人时的恐惧心理;在上下楼梯或台阶时采用两足行走,弥补四足步行机器人行走时产生的身体倾斜。提出四足/两足可重组步行机器人机构上的实现方法,分析3自由度3-UPU并联机构,以及其两两合并后的6-SPU并联机构,讨论它们在四足/两足可重组并联腿步行机器人中的应用,通过自由度计算进行四足/两足步行机器人的可动性分析,为四足/两足可重组并联腿机构步行机器人的进一步研究奠定了理论基础。

基于串并联机构的自重构移动机器人

为验证具有大输出力矩和工作空间的可重构机构对提高移动机器人运动性能的有效性,设计一种基于串并联等效球铰机构的可对接自重构多模块移动机器人。利用丝杠摇块机构构成并联机构支链,两个支链并联然后与一个旋转机构串联构成主动等效球铰机构。所提出的等效球铰机构结合并联机构和串联机构的优点,能以紧凑的结构提供较大的输出力矩和工作空间。对该串并联机构进行运动学分析,获得运动学逆解,作为机器人控制算法依据。进行机构静力学分析,获得确定驱动力和负载条件下机构的可控工作空间,为结构设计和工作路径选择提供理论指导。提出能实现平面偏差补偿和大负载能力的对接机构,实现机器人模块间的对接和脱离。设计JL-1型机器人样机,并利用该样机进行试验。试验验证了所提出串并联主动等效球铰机构和对接机构的有效性,同时证明自重构功能赋予野外机器人主动扩展地形适应性的能力,从而有效地增强机器人对环境和任务的适应性。

抓持式对接机构的设计及分析

针对多机器人崎岖地形刚性对接问题,提出了"相互独立→不完全约束→完全约束"的顺次对接方式,并设计了一种抓持式对接机构.该机构能够实现俯仰、偏摆两个自由度方向的姿态调整,并利用凸轮槽形控制机械手的张合,具备抓持物体、多机器人刚性对接、分工协作等多种作业功能.对该机构进行了运动学分析,给出了其运动学正解、逆解和工作空间模型.在此基础上研制JL-2型自重构模块化移动机器人样机,并对抓持式对接机构性能进行了实验验证.实验证明该机构具有较强的纠偏能力和较宽的抓持范围,可以完成多个机器人之间的相互对接、协作等多种任务.

可重构柔索并联机器人协同避障方法研究

针对可重构索驱动机器人自身结构与环境障碍物间高碰撞风险问题,设计了一种基于临界支撑线及多指抓握的可重构柔索机器人协同避障方法。通过简化环境障碍物与机器人结构得到一类可重构柔索机器人在复杂环境下的一般模型,在此模型基础上利用其结构的拓扑约束及障碍物间的临界支撑线求取机器人的无碰撞运动区域;通过凸包算法及凸包映射算法求取不同构型及障碍物分布下可重构柔索并联机器人的力封闭工作空间,并分析不同构型及障碍物分布对机器人无碰撞力封闭工作空间的影响;随后,通过优化算法求取指定运动轨迹上最优索分布;最后在重构索驱动机器人实验平台对所得优化结果进行验证。实验结果显示,所设计的可重构柔索机器人协同避障方法能有效避免重构索驱动机器人运动过程中的碰撞。

多运动态可重构轮履复合式机器人机械设计

针对复杂的室外地形特征,结合轮式、履带式移动机构的运动优点,提出并研制一种可重构的具有多种运动模式的轮-履复合机器人.该机器人由控制单元、两个相同的可重构车轮、翻转机构和车体组成,具有轮式、履带式、翻转式3种运动模式.轮式工作形态,机器人为两轮机器人,运行速度快,可全方位运动;履带工作状态,机器人可以适应砾石地、沙地、草地等多种复杂地形,具备较强的越障能力;翻转工作状态,履带轮整体翻转,可跨越栏杆等垂直障碍.机器人轮-履转换由车轮内部的并联四连杆机构实现,可根据地面特征选择运行模式,根据障碍类型选择越障方式.在建立运动学和力学模型的基础上,结合数字仿真方法对结构进行了参数化研究,此设计方法优化了转换机构的运动轨迹,降低了对驱动电动机的性能要求,提高了电动机的使用效率.试验表明,机器人可通过调整自身机构以合理的运动模式通过沙地、草地等路面环境,攀越阶梯和栏杆等复杂障碍,具有良好的环境适应性和越障性能,验证了该移动平台系统设计的合理性.

可重构并联机器人位置正解研究分析

针对六自由度并联机器人的位置正解特性,研究了两种结构形式的并联机器人。采用数值分析方法对并联结构机器人进行位置正解的求取,利用优化搜索原理对计算过程进行简化。最后正解模型进行仿真验证。验证结果表明,在误差允许范围内,采用数值法得到的位置正解与理想的位置正解真实值二者数值基本吻合。

一种可重构Stewart型并联机器人的静刚度分析

以一种可重构Stewart型并联机器人为研究对象,对其静刚度特性进行了理论建模和软件仿真.首先,通过设计三重复合虎克铰链和可以转换主、从运动的移动副,实现了机器人的结构降耦和变拓扑驱动;然后,基于速度基点法推导出机器人的速度雅可比矩阵,并结合虚功率原理,推导出了一种高效、精确的静刚度计算模型;最后,运用SolidWorks Simulation静力学仿真软件分析了3种重构构型的静刚度特性,并将其与理论模型结果进行了对比.结果显示,理论结果与有限元结果基本吻合,最大相对误差为18.36%.研究思路为六自由度并联机器人的结构优化、性能分析提供了理论依据.

一种可重构四足移动机器人的几何约束及其抗倾覆能力

提出了一种在倾倒后具有自我恢复能力的四足并联移动机器人。该四足机器人的腿部结构由一种可重构空间六杆机构构成,该六杆机构由两个改进型球面五杆机构并联而成,具有两种不同的运动位形。其中,运动位形Ⅰ具有1R2T共3个自由度,满足四足机器人对腿部行走机构的自由度需求;运动位形Ⅱ具有2个自由度且工作空间很大,满足其翻身所需要的工作空间条件。运用螺旋理论对球面五杆机构和可重构六杆机构的两种运动位形进行了几何约束分析,这两种运动位形具有互锁性能。运用D-H法对可重构六杆机构进行了逆运动学分析并得到其工作空间,验证了四足机器人翻身的可实现性。分析了四足机器人在翻身时的步态,得出了其在倾倒后自我恢复时腿部电机转动角度与机器人机身重心的关系。在四足机器人的翻身过程中,其腿部的可重构六杆机构均处于运动位形Ⅱ。在Adams软件中验证了预设翻身步态的正确性与合理性。

Development of a masticatory robot using a novel cable-driven linear actuator with bidirectional motion

Masticatory robots are an effective in vitro performance testing device for dental material and mandibular prostheses.A cable-driven linear actuator(CDLA)capable of bidirectional motion is proposed in this study to design a masticatory robot that can achieve increasingly human-like chewing motion.The CDLA presents remarkable advantages,such as lightweight and high stiffness structure,in using cable amplification and pulley systems.This work also exploits the proposed CDLA and designs a masticatory robot called Southeast University masticatory robot(SMAR)to solve existing problems,such as bulky driving linkage and position change of the muscle’s origin.Stiffness analysis and performance experiment validate the CDLA’s efficiency,with its stiffness reaching 1379.6 N/mm(number of cable parts n=4),which is 21.4 times the input wire stiffness.Accordingly,the CDLA’s force transmission efficiencies in two directions are 84.5%and 85.9%.Chewing experiments are carried out on the developed masticatory robot to verify whether the CDLA can help SMAR achieve a natural human-like chewing motion and sufficient chewing forces for potential applications in performance tests of dental materials or prostheses.

CUBE, a Cable-driven Device for Limb Rehabilitation

In this paper, a novel cable-driven parallel robot, CUBE, is introduced for the assistance of patients in rehabilitation exercising of both upper and lower limbs. The system is characterized by a lightweight structure that is easy to set-up and operate, for both clinical and home usage for both pre-determined and customized exercises, with control over the position of the end-effector while locking its rotation around the horizontal axes. Its cable-driven design makes it inherently safe in human/robot interactions also due to the extremely low inertia. While a novel end-effector design makes the device wearable both on the upper and lower limbs without having to disassemble any part of the structure. The design is presented with its kinematic analysis. Then, the manufacturing through 3D?printing and commercial components of a first prototype is reported. Finally, the system is validated through motion tests along simple trajectories and two different spatial exercises.

Experimental Validation of Light Cable-Driven Elbow-Assisting Device L-CADEL Design

This paper presents a new design of CADEL,a cable-driven elbow-assisting device,with light weighting and control improvements.The new device design is appropriate to be more portable and user-oriented solution,presenting additional facilities with respect to the original design.One of potential benefits of improved portability can be envisaged in the possibility of house and hospital usage keeping social distancing while allowing rehabilitation treatments even during a pandemic spread.Specific attention has been devoted to design main mechatronic components by developing specific kinematics models.The design process includes an implementation of specific control hardware and software.The kinematic model of the new design is formulated and features are evaluated through numerical simulations and experimental tests.An evaluation from original design highlights the proposed improvements mainly in terms of comfort,portability and user-oriented operation.

Pose optimization of the FAST feed support system based on the new feed cabin mechanism

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is the largest and most sensitive single-dish radio telescope in the world and has made many important scientific achievements in a few years. Given the enormous scientific research potential of the Milky Way center, it is necessary to enhance the observation zenith angle as close to the Milky Way center as possible. In this regard, a new mechanism for the feed cabin is proposed with cables and sliders, which is lighter in weight and larger in the workspace. This paper will introduce this new feed cabin and the whole feed support system and establish their mechanical models to optimize the relevant control parameters, making FAST achieve an observation zenith angle of at least 50°with satisfying the required constraints. It indicates that the new mechanism designed by the FAST team can be used for the FAST upgrade and the future FAST array project.