Global Stiffness Optimization of Parallel Robots Using Kinetostatic Performance Indices

Development of a new parallel manipulator can be very time consuming due to the traditional method of producing kinematic, dynamic and static calculation models and then evaluating them to determine aspects of the manipulator’s performance indices such as the mechanism’s workspace and singularity analysis. By extending the virtual chain approach to the type synthesis of parallel manipulators, this paper proposes a virtual-chain approach to the workspace analysis of parallel manipulators. This method is illustrated by producing and evaluating the workspace of several parallel robots including the well known DELTA robot by utilising the three-dimensional CAD software SolidWorks to produce a virtual prototype of a manipulator with an embedded virtual chain. The virtual chain represents the motion pattern of a manipulator’s end-effector and is very useful in the production of a graphical representation of the workspace of the manipulator. Using this approach, the link interferences and transmission indices can be easily taken into consideration in determining the workspace of a parallel manipulator.

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Performance Indices for Parallel Robots Considering Motion/Force Transmissibility

Intelligent Robotics and Applications - Lecture Notes in Computer Science ◽

10.1007/978-3-319-13966-1_4 ◽

2014 ◽

pp. 35-43 ◽

Cited By ~ 5

Author(s):

Fugui Xie ◽

Xin-Jun Liu ◽

Jie Li

Keyword(s):

Parallel Robots ◽

Performance Indices ◽

Force Transmissibility

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Screw Theory-Based Motion/Force Transmissibility Analysis of High-Speed Parallel Robots With Articulated Platforms

Journal of Mechanisms and Robotics ◽

10.1115/1.4046031 ◽

2020 ◽

Vol 12 (4) ◽

Author(s):

Qizhi Meng ◽

Fugui Xie ◽

Xin-Jun Liu ◽

Yukio Takeda

Keyword(s):

High Speed ◽

Screw Theory ◽

Parallel Robots ◽

Essential Property ◽

Performance Indices ◽

Transmission Index ◽

Force Transmissibility ◽

Kinematic Performance ◽

Insight Into ◽

Local Transmission

Abstract Motion/force transmissibility is an essential property reflecting the kinematic performance of parallel robots. Research on this performance of the single-platform parallel robots (SPPRs) has long been concerned and studied. In contrast, although many innovations and applications of the high-speed articulated-platform parallel robots (APPRs) have been presented, few studies on their motion/force transmissibility have been reported. This paper deals with the motion/force transmissibility analysis of high-speed parallel robots with articulated platforms. A modified output transmission index (MOTI) for the high-speed parallel robots with articulated platforms is proposed based on a newly defined concept of equivalent transmission wrench screw. Furthermore, by having an insight into the instantaneous relative motion inside the mobile platform, a medial transmission index (MTI) is proposed to evaluate its internal motion/force transmissibility. Based on these foundations, the local transmission index (LTI) is redefined as the minimum value of the input, modified output, and medial transmission indices. Under the framework of the above performance indices, motion/force transmissibility analysis of two typical high-speed articulated-platform parallel robots, i.e., Heli4 and Par4, are presented. The proposed indices are excepted to be applied to the optimal design of high-speed parallel robots with articulated platforms.

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Optimizing Stiffness and Dexterity of Planar Adaptive Cable-Driven Parallel Robots

Journal of Mechanisms and Robotics ◽

10.1115/1.4035681 ◽

2017 ◽

Vol 9 (3) ◽

Cited By ~ 19

Author(s):

Saeed Abdolshah ◽

Damiano Zanotto ◽

Giulio Rosati ◽

Sunil K. Agrawal

Keyword(s):

Trajectory Planning ◽

Performance Index ◽

Elastic Stiffness ◽

Parallel Robots ◽

Kinematic Redundancy ◽

Performance Indices ◽

Systematic Method ◽

End Effector ◽

Driven Systems ◽

Optimal Values

Adaptive cable-driven parallel robots are a special subclass of cable-driven systems in which the locations of the pulley blocks are modified as a function of the end-effector pose to obtain optimal values of given performance indices within a target workspace. Due to their augmented kinematic redundancy, such systems enable larger workspace volume and higher performance compared to traditional designs featuring the same number of cables. Previous studies have introduced a systematic method to optimize design and trajectory planning of the moving pulley-blocks for a given performance index. In this paper, we study the motions of the pulley blocks that optimize two performance indices simultaneously: stiffness and dexterity. Specifically, we present a method to determine the pulley blocks motions that guarantee ideal dexterity with the best feasible elastic stiffness, as well as those that guarantee isotropic elastic stiffness with the best feasible dexterity. We demonstrate the proposed approach on some practical cases of planar adaptive cable-driven parallel robots.

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On the Minimum Cable Tensions for the Cable-Based Parallel Robots

Journal of Applied Mathematics ◽

10.1155/2014/350492 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Peng Liu ◽

Yuanying Qiu ◽

Yu Su ◽

Jiantao Chang

Keyword(s):

Convex Optimization ◽

Optimization Algorithm ◽

Kinematic Model ◽

Optimization Theory ◽

Parallel Robot ◽

Parallel Robots ◽

Performance Indices ◽

Cable Tension ◽

The Stability ◽

The Relationship

This paper investigates the minimum cable tension distributions in the workspace for cable-based parallel robots to find out more information on the stability. First, the kinematic model of a cable-based parallel robot is derived based on the wrench matrix. Then, a noniterative polynomial-based optimization algorithm with the proper optimal objective function is presented based on the convex optimization theory, in which the minimum cable tension at any pose is determined. Additionally, three performance indices are proposed to show the distributions of the minimum cable tensions in a specified region of the workspace. An important thing is that the three performance indices can be used to evaluate the stability of the cable-based parallel robots. Furthermore, a new workspace, the Specified Minimum Cable Tension Workspace (SMCTW), is introduced, within which all the minimum tensions exceed a specified value, therefore meeting the specified stability requirement. Finally, a camera robot parallel driven by four cables for aerial panoramic photographing is selected to illustrate the distributions of the minimum cable tensions in the workspace and the relationship between the three performance indices and the stability.

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