Workspace and singularity analysis of a 3-DOF planar parallel manipulator with actuation redundancy
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SUMMARY This paper deals with the position workspace, orientation workspace, and singularity of a 3-degree-of-freedom (DOF) planar parallel manipulator with actuation redundancy, which is created by introducing a redundant link with active actuator to a 3-DOF nonredundant parallel manipulator. Based on the kinematic analysis, the position workspace and orientation workspace of the redundantly actuated parallel manipulator and its corresponding nonredundant parallel manipulator are analyzed, respectively. In the singularity analysis phase, the relationship between the generalized input velocity and the generalized output velocity is researched on the basis of the theory of singular value decomposition. Then a method to investigate the singularity of parallel manipulators is presented, which is used to determine the singularity of the redundantly actuated parallel manipulator. In contrast to the corresponding nonredundant parallel manipulator, the redundant one has larger orientation workspace and less singular configurations. The redundantly actuated parallel manipulator is incorporated into a 4-DOF hybrid machine tool which also includes a feed worktable to demonstrate its applicability.Keywords:
Work space
Position (finance)
It is well-known that when singularities are located within the workspace of the parallel mechanism (PM), the usefulness of its workspace is significantly deteriorated. To handle this problem, we suggest an optimal design method which leads to more useful and larger workspace of the PM by taking its singularity locations into consideration in design process. Kinematic models of three selected planar PMs, a 5R type PM, a 3-RPR type planar PM, and a 3-RRR type planar PM, are derived via screw theory and their singularity analyses are conducted. Then workspace optimal designs for those three PMs are conducted to verify that the suggested design method leads more useful and larger workspace in which deterioration by singularity is minimal.
Work space
Optimal design
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The manipulator workspace denotes the work area of a manipulator and it is an important foundation of designing a robot. The workspace of a novel symmetrical 4-DOF 3-RRUR parallel manipulator is researched here based on the inverse solution. Five essential conditions of a point within the workspace of the manipulator are presented and the cause of the existence of each condition is given. According to the characteristics of this parallel mechanism and the geometrics, and based on the inverse kinematical solution of the mechanism, the reachable workspace under the five conditions is ascertained. The three-dimensional graph and its section graphs of the workspace are obtained. The thoroughness of the workspace of the manipulator is proved. The mechanism with the advantages of simple symmetric structure and large stiffness can be applied to the developments of four-dimensional force sensors, NC positioning platforms, parallel machine tools and micro-positional parallel manipulators. This work is with great significance to the practical application of the manipulator.
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Stewart platform
Mobile manipulator
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SUMMARY This paper deals with the position workspace, orientation workspace, and singularity of a 3-degree-of-freedom (DOF) planar parallel manipulator with actuation redundancy, which is created by introducing a redundant link with active actuator to a 3-DOF nonredundant parallel manipulator. Based on the kinematic analysis, the position workspace and orientation workspace of the redundantly actuated parallel manipulator and its corresponding nonredundant parallel manipulator are analyzed, respectively. In the singularity analysis phase, the relationship between the generalized input velocity and the generalized output velocity is researched on the basis of the theory of singular value decomposition. Then a method to investigate the singularity of parallel manipulators is presented, which is used to determine the singularity of the redundantly actuated parallel manipulator. In contrast to the corresponding nonredundant parallel manipulator, the redundant one has larger orientation workspace and less singular configurations. The redundantly actuated parallel manipulator is incorporated into a 4-DOF hybrid machine tool which also includes a feed worktable to demonstrate its applicability.
Work space
Position (finance)
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The workspace of parallel manipulator 6-SPS is studied in this paper. By means of the algorithm of mathematical analysis,the working envelopes and the reachable spaces with known structural parameters can be calculated accurately and rapidly. The influence of the structural parameters on the working envelopes is explored. Some regular variations of significance are found. These results are significant for the designing and usage of the parallel manipulator.
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In this paper, the Singularity representation and workspace determination of the parrallel robot PAR4 are presented. The serial singularity (type 1) is determined using the kinematic matrix. This type of singularity indicates the unreachable points in the workspace. Based on the inverse geomatric model (MGI) of the parallel robot PAR4 the workspace is determined. Numerical results are presented showing some singularity of type 1 and their representation of the robot PAR4. Also, the workspace of this robot is presented.
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Representation
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The high-redundancy actuator concept that is inspired by biomimetic is an approach to fault tolerant actuator that aims to provide fault tolerance using relatively large numbers of small actuation elements. The actuation elements are assembled in parallel and series configurations to form a single actuator that has intrinsic fault tolerance. During normal operations, it is possible that some of these elements are operational and some are faulty. In this situation, the high-redundancy actuator will still work, but with graceful degradation. This paper discusses the modelling aspect of the high-redundancy actuator that consists of 12 actuation elements based on linear electromechanical actuation technology. Simulation results are validated with real-time experimental results using both a single actuator and the full high-redundancy actuator in open-loop and closed-loop.
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With focus on parallel manipulator in robot research, the research on parallel mechanism theory has been going through rapid development and the theories on kinematics, dynamics, performance analysis etc. have been enriching. This article quoted lots of documents on workspace in performance analysis and thoroughly analyzed current status of workspace, which is one branch of parallel manipulator in research.
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Manipulator (device)
Robot manipulator
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This paper studies the singularity of a five-degree-of-freedom 3-RRUR parallel manipulator, presents singularity equations and the geometry conditions of singularity of the 3-RRUR parallel manipulator. The input plan is optimized based on the analysis on singularity of the manipulator. The special characteristics in singularity of the parallel manipulator is given. This parallel manipulator can be used to build industrial robots for assembly or dummy axis machine tools with simple symmetry structure, less error accumulating and high rigidness.
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In this study, kinematics design and workspace analysis of a novel spatial parallel mechanism is elaborated. The proposed mechanism is to be exploited in a hybrid serial-parallel mobile robot to fulfill stable motion of the robotic system when handling heavy objects by a serial manipulator mounted on the parallel mechanism. In fact, this parallel mechanism has been designed to obtain an appropriate maneuverability and fulfill the tipover stability of a hybrid serial-parallel mobile robotic system after grasping heavy objects. The proposed mechanism is made of three legs while each leg has one active degree of freedom (DOF) so that the mechanism contains 3-DOF. In order to investigate this novel parallel mechanism, inverse and forward kinematics model is developed and verified using two maneuvers. Next, the workspace of the manipulator is demonstrated symbolically, besides a numerical analysis will be studied. Finally, the advantages of exploiting such a parallel manipulator are discussed in order to be used in a hybrid serial-parallel mobile robotic system.
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Serial manipulator
Mobile manipulator
Forward kinematics
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The workspace of parallel robot manipulator is studied in this paper. As the method of input-trans-formation is used in algorithm, the optimization procedure is simplified. In the paper, the workspace sec-tions of parallel robot manipulator are analyzed, and the relation between size and workspace is discussedin detail. The method of workspace enlargement obtained in this paper is significant for designing and us-ing parallel robot manipulator.
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Mobile manipulator
Manipulator (device)
Robot manipulator
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