New Indices for Optimal Design of Redundantly Actuated Parallel Manipulators

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Qinchuan Li ◽  
Ningbin Zhang ◽  
Feibo Wang
Keyword(s):  
Optimal Design ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Mean Value ◽  
Transmission Performance ◽  
Transmission Index ◽  
Redundantly Actuated ◽  
Lower Mobility ◽  
Six Dof ◽  
Force Transmissibility

Redundantly actuated parallel manipulators (PMs) receive growing interest due to their reduced singularity and enlarged workspace. This paper proposes new indices for optimal design and analysis of redundantly actuated PMs by evaluating their motion/force transmissibility. First, we proposed a method to extract a multi-DOF (degrees-of-freedom) redundantly actuated PM into several subsidiary one-DOF PMs with two or more actuators by locking some actuators in an ergodic manner. Then, a new index of output transmission performance is proposed by investigating the mean value of the instantaneous power produced by the multiple actuation wrenches and one twist of the moving platform of one-DOF PMs. A local transmission index (LTI) is defined as the minimum value of the index of output and input transmission performance. A global transmission index (GTI) is then established based on the LTI. The proposed LTI and GTI are coordinate-free and have clear physical interpretation. Finally, the validity and universality of the new indices are demonstrated by optimization and analysis of redundantly actuated lower-mobility PMs with extra articulated six-DOF or limited-DOF limbs.

Mobility, Kinematic Analysis, and Dimensional Optimization of New Three-Degrees-of-Freedom Parallel Manipulator With Actuation Redundancy

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
Lingmin Xu ◽  
Qinchuan Li ◽  
Ningbin Zhang ◽  
Qiaohong Chen
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Force Transmission ◽  
Transmission Index ◽  
Prismatic Joints ◽  
Redundantly Actuated ◽  
Force Transmissibility ◽  
Solution Velocity ◽  
Three Degrees Of Freedom

Parallel manipulators (PMs) with redundant actuation are attracting increasing research interest because they have demonstrated improved stiffness and fewer singularities. This paper proposes a new redundantly actuated parallel manipulator that has three degrees-of-freedom (DOFs) and four limbs. The proposed manipulator is a 2UPR-2PRU parallel manipulator (where P represents an actuated prismatic joint, R represents a revolute joint, and U represents a universal joint) that is actuated using four prismatic joints; two of these joints are mounted on the base to reduce the movable mass. Mobility analysis shows that the moving platform has two rotational DOFs and one translational DOF. First, the inverse displacement solution, velocity, and singularity analyses are discussed. Next, the local transmission index (LTI) and the good transmission workspace are used to evaluate the motion/force transmissibility of the 2UPR-2PRU parallel manipulator. Finally, the parameter-finiteness normalization method (PFNM) is used to produce an optimal design that considers the good transmission workspace. It is thus shown that the motion/force transmission of the proposed manipulator is improved by optimizing the link parameters.

Kinematic Synthesis of Spatial in-Parallel Wire-Driven Mechanism With Six Degrees of Freedom With High Force Transmissibility

2000 ◽  
Author(s):  
Yukio Takeda ◽  
Hiroaki Funabashi
Keyword(s):  
Degrees Of Freedom ◽  
Force Transmission ◽  
Kinematic Synthesis ◽  
Parallel Wire ◽  
Six Degrees Of Freedom ◽  
Output Force ◽  
Transmission Index ◽  
Six Dof ◽  
Force Transmissibility ◽  
The Relationship

Abstract We propose an index for evaluating the force transmission characteristics in general N degree-of-freedom (dof) in-parallel wire-driven mechanisms (PWDMs) with N + 1 wires. The relationship between input force and output force in an N dof in-parallel actuated mechanism with only rigid links was used for defining the transmission index for a PWDM. The index has been applied to the kinematic synthesis of spatial six dof PWDM with seven wires, and novel PWDMs with high force transmissibility have been obtained.

scholarly journals Optimum Seeking of Redundant Actuators for M-RCM 3-UPU Parallel Mechanism

2020 ◽  
Author(s):  
Chen Zhao ◽  
Jingke Song ◽  
Xuechan Chen ◽  
Ziming Chen ◽  
Huafeng Ding
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Universal Joint ◽  
Prismatic Joint ◽  
Transmission Index ◽  
Redundant Actuators ◽  
Force Transmissibility ◽  
Singular Configuration

Abstract This paper focuses on a 2R1T 3-UPU (U for universal joint and P for prismatic joint) parallel mechanism (PM) with two rotational and one translational (2R1T) degrees of freedom (DOFs) and the ability of multiple remote centers of motion (M-RCM). The singularity analysis based on the indexes of motion/force transmissibility and constraint shows that this PM has transmission singularity, constraint singularity, mixed singularity and limb singularity. To solve these singularproblems, the quantifiable redundancy transmission index (RTI) and the redundancy constraint index (RCI) are proposed for optimum seeking of redundant actuators for this PM. Then the appropriate redundant actuators are selected and the working scheme for redundant actuators near the corresponding singular configuration are given to help the PM go through the singularity.

Optimal Design of a Metamorphic Parallel Mechanism With Reconfigurable 1T2R and 3R Motion Based on Unified Motion/Force Transmissibility

2016 ◽  
Author(s):  
Dongming Gan ◽  
Jian S. Dai ◽  
Jorge Dias ◽  
Lakmal D. Seneviratne
Keyword(s):  
Optimal Design ◽  
Inverse Kinematics ◽  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Rotation Axis ◽  
Geometric Constraint ◽  
Transmission Performance ◽  
Trade Off ◽  
Pure Rotation ◽  
Force Transmissibility

This paper presents a metamorphic parallel mechanism which can switch its motion between one translation and two rotation (1T2R) motion and pure rotation (3R) motion. This feature stems from a reconfigurable revolute (rR) joint of which the rotation axis can be altered freely. Screw based geometric constraint is used to demonstrate the reconfiguration and mobility. Unified inverse kinematics, Jacobian matrix and motion/force transmissibility are provided using screws. Based on those, singularity loci are illustrated and optimal design of some key parameters are conducted considering both the 1T2R and 3R phases. Trade-off can be made between the maximum singularity-free workspace and transmission performance based on the optimal design results in this paper for specific applications requiring 1T2R and 3R motion.

Optimal Design of Spherical 5R Parallel Manipulators Considering the Motion/Force Transmissibility

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Chao Wu ◽  
Xin-Jun Liu ◽  
Liping Wang ◽  
Jinsong Wang
Keyword(s):  
Performance Evaluation ◽  
Optimal Design ◽  
Parallel Manipulator ◽  
Screw Theory ◽  
Parallel Manipulators ◽  
Dimensional Synthesis ◽  
Force Transmission ◽  
Minimally Invasive Surgical ◽  
Pointing Device ◽  
Force Transmissibility

The spherical 5R parallel manipulator is a typical parallel manipulator. It can be used as a pointing device or as a minimally invasive surgical robot. This study addresses the motion/force transmission analysis and optimization of the manipulator by taking into account the motion/force transmissibility. The kinematics of the manipulator is analyzed. Several transmission indices are defined by using screw theory for the performance evaluation and dimensional synthesis. The process of determining the optimal angular parameters based on performance charts is presented. The manipulator that has a large workspace and good motion/force transmissibility is identified.

Conceptual Design of Lower-Mobility Parallel Manipulators Based on Wrench Graphs

2014 ◽  
Author(s):  
Gamal El-Ghazaly ◽  
Stéphane Caro
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Three Dimensional ◽  
Main Idea ◽  
Parallel Manipulators ◽  
Geometric Constraints ◽  
Design Stage ◽  
Case Scenario ◽  
Worst Case ◽  
Lower Mobility

This paper presents a design methodology for lower-mobility parallel manipulators based on classification of wrench systems into four main classes. Wrench systems are represented in a three-dimensional projective space ℙ3 using wrench graphs where it is easy to incorporate geometric constraints to have simple singularity conditions using Grassmann-Cayley algebra (GCA). The main idea of the approach is to design a PM with an overall (constraint and actuation) wrench system that complies with a given wrench graph for which singularity conditions have been predetermined. The main advantage of this methodology is that the singularity conditions are already known a priori and consequently, it gives an opportunity to avoid such conditions at the design stage and make them unreachable. In the worst case scenario, where none of singularity conditions cannot be avoided, one can have a PM with known singular configurations which are always difficult to determine for already designed manipulators. As illustrative examples, two different five degrees-of-freedom (dof) mechanisms have been designed based on some of the defined wrench graphs giving 3T2R motion pattern. The first mechanism has some avoided singularities and the second one is free of singularity.

Evaluation of Force/Torque Transmission Quality for Parallel Manipulators

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Xiang Chen ◽  
Chao Chen ◽  
Xin-Jun Liu
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Analysis And Design ◽  
Torque Transmission ◽  
Transmission Index ◽  
Internal Forces ◽  
Transmission Quality ◽  
End Effectors ◽  
External Loads

Performance evaluation is one of the most important issues in the analysis and design of parallel manipulators. The internal forces and torques in parallel manipulators contribute to manipulating the end-effectors and resisting the external loads. In this work, we propose a transmission index to evaluate the force and torque transmission quality of parallel manipulators. The index is normalized and used to analyze the exactly constrained parallel manipulators, based on the transmission matrix spanned by transmission wrench screws (TWSs). Furthermore, the index is applied to parallel manipulators with different degrees of freedom (DOF) in order to illustrate and validate the proposed approach and index. Finally, a typical parallel manipulator is selected to address the comparison analysis between different indices, which demonstrates that the proposed index, possessing respective merits, could be complementary to other existing indices.

Determination of the closed-form workspace area expression and dimensional optimization of planar parallel manipulators

Robotica ◽  
2016 ◽  
Vol 35 (10) ◽  
pp. 2056-2075 ◽  
Author(s):  
M. Ganesh ◽  
Banke Bihari ◽  
Vijay Singh Rathore ◽  
Dhiraj Kumar ◽  
Chandan Kumar ◽  
...  
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Solution Space ◽  
Optimization Procedure ◽  
Parallel Manipulators ◽  
Force Transmission ◽  
Workspace Analysis ◽  
Planar Parallel Manipulator ◽  
Transmission Index ◽  
Planar Parallel Manipulators

SUMMARYOptimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.

Workspace Analysis of a Novel Six-Degrees-of-Freedom Parallel Manipulator With Coaxial Actuated Arms

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Mats Isaksson ◽  
Matthew Watson
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Limited Range ◽  
Parallel Mechanisms ◽  
Six Degrees Of Freedom ◽  
Serial Robots ◽  
High Acceleration ◽  
Redundantly Actuated

Parallel manipulators possess several advantages compared to serial robots, including the possibilities for high acceleration and high accuracy positioning of the manipulated platform. However, the majority of all proposed parallel mechanisms suffer from the combined drawbacks of a small positional workspace in relation to the manipulator footprint and a limited range of rotations of the manipulated platform. This paper analyses a recently proposed six-degrees-of-freedom parallel mechanism that aims to address both these issues while maintaining the traditional advantages of a parallel mechanism. The investigated manipulator consists of six actuated coaxial upper arms that are allowed to rotate indefinitely around a central cylindrical base column and a manipulated platform where five of the six joint positions are collinear. The axis-symmetric arm system leads to an extensive positional workspace while the proposed link arrangement increases the range of achievable platform rotations. The manipulator workspace is analyzed in detail and two methods to further increase the rotational workspace are presented. It is shown that the proposed manipulator has the possibility of a nonsingular transition of assembly modes, which extends the usable workspace. Furthermore, it is demonstrated how an additional kinematic chain can be utilized to achieve infinite platform rotation around one platform axis. By introducing additional mobility in the manipulated platform, a redundantly actuated mechanism is avoided.

scholarly journals Optimum Seeking of Redundant Actuators for M-RCM 3-UPU Parallel Mechanism

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Chen Zhao ◽  
Jingke Song ◽  
Xuechan Chen ◽  
Ziming Chen ◽  
Huafeng Ding
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Quantitative Criterion ◽  
Singularity Problem ◽  
Transmission Index ◽  
Redundant Actuators ◽  
Open Issue ◽  
Force Transmissibility ◽  
Singular Configuration

AbstractThe singularity problem brings troubles to the design and application for the parallel mechanism. Currently, redundant actuation is one of the useful methods to solve this singularity problem. However, faced to the numerous joints in a parallel mechanism, how to make a quantitative criterion of seeking the most efficient joints added actuators for letting the mechanism passes through singularity is a necessarily open issue. This paper focuses on a 2R1T 3-UPU (U for universal joint and P for prismatic joint) parallel mechanism (PM) with two rotational and one translational (2R1T) degrees of freedom (DOFs) and the ability of multiple remote centers of motion (M-RCM). The singularity analysis based on the indexes of motion/force transmissibility and constraint shows that this PM has transmission singularity, constraint singularity, mixed singularity and limb singularity. To solve these singular problems, the quantifiable redundancy transmission index (RTI) and the redundancy constraint index (RCI) are proposed for optimum seeking of redundant actuators for this PM. Then the appropriate redundant actuators are selected and the working scheme for redundant actuators near the corresponding singular configuration are given to help the PM passes through the singularity. This research proposes a quantitative criterion to optimum seeking of redundant actuators for the parallel mechanism to solve its singularity.

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