Workspace Performance Optimization of Fully Restrained Cable-Driven Parallel Manipulators (original) (raw)
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Workspace analysis of fully restrained cable-driven manipulators
2009
For Cable-Driven Parallel Manipulators (CDPMs), employing redundant driving cables is necessary to obtain the full manipulation of the moving platform because of the unilateral driving property of the cables. Unlike rigid-link manipulators, the workspace of CDPMs is always determined and characterized by positive tension status of driving cables. In addition, it has been realized that the Tension Factor (TF) reflecting the relative tension distribution among the driving cables is an appropriate measure to evaluate the quality of tension restraint for CDPMs. However, since redundant cables are employed to drive the moving platform, the TF values are not unique for a particular moving platform pose. Therefore, how to determine the workspace and obtain the optimal TF value so as to generate a workspace with optimized performance become the major subjects of this paper. It is shown that the workspace can be generally formed from tension conditions verified by a recursive dimension-reduction approach and that the optimal TF value at every pose can be efficiently determined through a linear optimization approach, although it is essentially a nonlinear optimization problem. Computational examples are provided to demonstrate the effectiveness of the proposed algorithms.
Journal of Mechanical Design, 2011
In this paper, a technique to generate the wrench-closure workspace for general case completely restrained cable driven parallel mechanisms is proposed. Existing methods can be classified as either numerically or analytically based approaches. Numerical techniques exhaustively sample the task space, which can be inaccurate due to discretisation and is computationally expensive. In comparison, analytical formulations have higher accuracy, but often provides only qualitative workspace information. The proposed hybrid approach combines the high accuracy of the analytical approach and the algorithmic versatility of the numerical approach. Additionally, this is achieved with significantly lower computational costs compared to numerical methods. It is shown that the wrench-closure workspace can be reduced to a set of univariate polynomial inequalities with respect to a single variable of the end-effector motion. In this form, the workspace can then be efficiently determined and quantitati...
A generic force-closure analysis algorithm for cable-driven parallel manipulators
2011
Cable-driven parallel manipulators (CDPMs) are a special class of parallel manipulators that are driven by cables instead of rigid links. Due to the unilateral driving property of cables, the cables in a CDPM must always maintain positive tension. In this paper, a methodology based on convex analysis is developed for the force-closure analysis of fully-constrained CDPMs. This method is systematic, easy to implement and satisfies both the necessary and sufficient conditions. The key point of this method is to define a critical vector that must be positively expressed by the tension vectors associated with the driving cables. The solution can be found by resolving a limited set of linear equations. Following the same approach, the method is also extended to generate the static workspace for under-constrained CDPMs. Therefore, this generic force-closure analysis can cater to the workspace analysis of both fully-constrained and under-constrained CDPMs. The computationally efficiency of the algorithm is verified through simulations.
2011
Abstract This paper deals with the wrench-feasible workspace (WFW) of n-degree-of-freedom parallel robots driven by n or more than n cables. The WFW is the set of mobile platform poses for which the cables can balance any wrench of a given set of wrenches, such that the tension in each cable remains within a prescribed range. Requirements of nonnegative cable tensions, as well as maximum admissible tensions, are thus satisfied.
Force-closure workspace analysis of cable-driven parallel mechanisms
2006
A cable-driven parallel mechanism (CDPM) possesses a number of promising advantages over the conventional rigid-link mechanisms, such as simple and lightweight mechanical structure, high-loading capacity, and large reachable workspace. However, the formulations and results obtained for the rigid-link mechanisms cannot be directly applied to CDPMs due to the unilateral property of cables. This paper focuses on the workspace analysis of fully restrained positioning mechanisms. Because the cable tension is the most essential issue to constrain the moving platform, the force-closure workspace is mainly studied. A general approach is proposed to check the force-closure condition. This condition is expressed in terms of the convex hull which encloses the origin. However, such a condition is formulated and expressed in high dimensions. To simplify the analysis, a recursive dimension reduction algorithm is proposed to check convex hulls in one dimension spaces. This algorithm is verified through simulation results of various CDPMs.
Optimal Design of Dexterous Cable Driven Parallel Manipulators
Optimal design of parallel manipulators is known as a challenging problem especially for cable driven robots. In this paper, optimal design of cable driven redundant parallel manipulators (CDRPM) is studied in detail. Visual Inspection method is proposed as a systematic design process of the manipulator. A brief review of various design criteria shows that the optimal design of a CDRPM cannot be performed based on single objective. Therefore, a multi objective optimal design problem is formulated in this paper through an overall cost function. Furthermore, a proper weighting selection for the overall cost function is proposed, which can be viewed as a promising method to the open problem of parallel manipulator design. In order to verify the effectiveness of the proposed method, it is applied on the design of KNTU CDRPM, an eight actuated with six degrees of freedom CDRPM, which is under investigation for possible high speed and wide workspace applications in K. N. Toosi University of Technology. Finally, a combined numerical optimization algorithm is used to find the unique global optimum point. The result shows a significant enhancement in the performance characteristics of the KNTU CDRPM compared to that of the other CDRPMs. Since the proposed method is not restricted to any particular assumption on the objectives and design parameters, it can be used for optimal design of other manipulators.
In this paper, we study the design and workspace of a 6-6 cable-suspended parallel robot. The workspace volume is characterized as the set of points where the centroid of the moving platform can reach with tensions in all suspension cables at a constant orientation. This paper attempts to tackle some aspects of optimal design of a 6DOF cable robot by addressing the variations of the workspace volume and the accuracy of the robot using different geometric configurations, different sizes and orientations of the moving platform. The global condition index is used as a performance index of a robot with respect to the force and velocity transmission over the whole workspace. The results are used for design analysis of the cable-robot for a specific motion of the moving platform.
Design and workspace analysis of a 6–6 cable-suspended parallel robot
Mechanism and Machine Theory, 2004
In this paper, we study the design and workspace of a 6-6 cable-suspended parallel robot. The workspace volume is characterized as the set of points where the centroid of the MP (MP) can reach with tensions in all suspension cables at a constant orientation. This paper attempts to tackle some aspects of optimal design of a 6DOF cable robot by addressing the variations of the workspace volume and the accuracy of the robot using different geometric configurations, different sizes and orientations of the MP. The global condition index is used as a performance index of a robot with respect to the force and velocity transmission over the whole workspace. The results are used for design analysis of the cable-robot for a specific motion of the MP. 0-7803-7860-1/03/$17.00
2016
ARTICLE INFORMATION ABSTRACT Original Research Paper Received 18 October 2015 Accepted 10 November 2015 Available Online 15 December 2015 Cable-Driven Parallel Robot has many advantages. However, the problems of cable collision between each other and environment, the lack of proper structure and non-positive cable tension prevent the spread of them. Therefore, connecting a serial manipulator to mobile platform improves the ability of object manipulation. This paper investigates the multi-objective optimization structure design and comparative study of spatial constrained and suspended cable-driven parallel robot. Installed serial manipulators possess a full hybrid robot’s features. The workspace volume, kinematic stiffness and sensitivity are three sets of optimization criteria. The workspace volume is calculated by a novel approach of combination constraints to prevent cables colliding with each other, cable collision with moving platform, uncontrollability and singularity of the r...
Optimal design of cable-driven parallel robots for large industrial structures
2014 IEEE International Conference on Robotics and Automation (ICRA), 2014
This paper presents the preliminary studies dedicated to the design of cable-driven parallel robots (CDPRs) for industrial purposes. The goal is to transport the proper tools around a jacket, an offshore structure supporting a wind turbine, in order to perform painting and sandblasting tasks. In this paper, a simplified case study consisting of a structure composed of four tubes is investigated. A fully constrained CDPR and a suspended CDPR are studied. The design problems of the CDPRs at hand are formulated as optimization problems. They aim at determining the locations of the base anchor points of the cables that minimize the size of the CDPR, while satisfying a set of constraints. Those constraints guarantee that the moving platform can support the external wrenches and that there is no interference between the cables and between the cables and the environment, all along the path to be followed by the moving platform.