Structural Condition for [PP]S Parallel Mechanism without Parasitic Motion

2010 ◽  
Vol 46 (15) ◽  
pp. 31 ◽  
Author(s):  
Qinchuan LI
Keyword(s):  
Parallel Mechanism ◽  
Structural Condition ◽  
Parasitic Motion

Influence Coefficients and Singularity Analysis of a Novel 3-UPU Parallel Mechanism

2017 ◽  
Author(s):  
Ziming Chen ◽  
Dongliang Cheng ◽  
Yang Zhang ◽  
Zhiwei Yang ◽  
Jin Zhou
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Model Simulation ◽  
Hessian Matrix ◽  
Symmetry Plane ◽  
Coefficient Matrix ◽  
Singularity Analysis ◽  
Influence Coefficient ◽  
Parasitic Motion ◽  
Moving Platform

A novel 3-UPU parallel mechanism with two rotational and one translational (2R1T) degrees of freedom (DOFs) is analyzed in this paper. The base and moving platform of this mechanism are always symmetric about a middle symmetry plane. The moving platform can rotate continuously about any axis on the middle symmetry plane, so there exists no parasitic motion during the rotation. Using the kinematic influence coefficient theory and the imaginary mechanism method, the first and second order influence coefficient matrix (namely Jacobian matrix and Hessian matrix) of this mechanism are derived. The relations between the velocity and acceleration of the moving platform and the actuated links are obtained. In order to verify the correctness of the theory, two numerical examples are enumerated and varified by the 3D model simulation. The singularities of this mechanism is discussed and the singular configurations of the mechanism, including one kind of limb singularity and two kinds of platform singularities, are obtained.

Compliant Mechanism Reconfiguration Based on Position Space Concept for Reducing Parasitic Motion

2015 ◽  
Author(s):  
Haiyang Li ◽  
Guangbo Hao
Keyword(s):  
Finite Element Analysis ◽  
Parallel Mechanism ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Position Space ◽  
Element Analysis ◽  
Compact Structure ◽  
Parasitic Motion ◽  
Compliant Parallel Mechanism ◽  
Space Concept

This paper introduces a compliant mechanism reconfiguration approach that can be used to minimize the parasitic motions of a compliant mechanism. This reconfiguration approach is based on the position spaces, identified by the screw theory, of independent compliant modules in a compliant mechanism system. The parasitic motions (rotations) of a compliant mechanism are first modelled associated with the variables representing any positions of the compliant modules in the position spaces. The optimal positions of the compliant modules are then obtained where the parasitic motions are reduced to minimal values. A procedure of the compliant mechanism reconfiguration approach is summarized and demonstrated using a decoupled XYZ compliant parallel mechanism as an example. The analytical results show that the parasitic motions of the XYZ compliant parallel mechanism in the example can be dramatically reduced by the position/structure reconfiguration, which is also validated by finite element analysis. The position space of a compliant module contains a number of possible positions, thus a compliant mechanism can also be efficiently reconfigured to a variety of practical patterns such as the configuration with compact structure.

Design and Kinematic Analysis of a 3RRlS Metamorphic Parallel Mechanism for Large-Scale Reconfigurable Space Multifingered Hand

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Chong Zhao ◽  
Hongwei Guo ◽  
Rongqiang Liu ◽  
Zongquan Deng ◽  
Bing Li
Keyword(s):  
Shape Memory Alloy ◽  
Kinematic Analysis ◽  
Parallel Mechanism ◽  
Large Scale ◽  
Screw Theory ◽  
Kinematic Equation ◽  
Aerospace Application ◽  
Parasitic Motion ◽  
Geometric Conditions ◽  
In Series

Capturing noncooperative targets in space has great prospects for aerospace application. In this work, the knuckle unit of a large-scale reconfigurable space multifingered hand (LSRSMFH) for multitask requirements is studied. A plurality of knuckle units is connected in series to form a finger of the LSRSMFH. First, the lockable spherical (lS) joint, a new metamorphic joint that can function as a Hooke (lS1) or spherical (lS2) joint and is driven by shape memory alloy (SMA) material, is proposed. Based on the lS joint, this paper presents a new metamorphic parallel mechanism (MPM) (i.e., 3RRlS MPM), which has four configurations, namely, 3RRlS1, 3RRlS2, 2RRlS1-RRlS2, and 2RRlS2-RRlS1 configuration. The degree-of-freedom (DOF), overconstraint, and parasitic motion of the 3RRlS MPM are analyzed using screw theory, of which the DOF can be changed from 1 to 3. The 3RRlS1 configuration has a virtual constraint, and the 3RRlS2 configuration has parasitic motions. The results indicate that the mechanism motion screws can qualitatively represent the mechanism parasitic motions, and it is verified by deriving the kinematic equation of the 3RRlS MPM based on its spatial geometric conditions, the workspace of the 3RRlS MPM is further solved. The kinematic analysis indicates that the 3RRlS MPM can realize the folding, capturing, and reconfiguring conditions of the LSRSMFH.

Investigation of a novel 2R1T parallel mechanism and construction of its variants

Robotica ◽  
2021 ◽  
pp. 1-15
Author(s):  
Jingfang Liu ◽  
Xiangmeng Fan ◽  
Huafeng Ding
Keyword(s):  
Inverse Kinematics ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Rotation Axis ◽  
End Effector ◽  
Parasitic Motion ◽  
Structure Synthesis ◽  
Synthesis Strategy ◽  
Continuous Rotation ◽  
Large Rotations

Abstract A 3-RRPRR variable spherical symmetrical parallel mechanism (PM) with arc-shaped sliding pairs and no parasitic motion is presented, exhibiting two rotational and one translational (2R1T) degrees of freedom. Three limbs are symmetrically distributed between the base and end-effector; upper and lower parts of each limb are mirror symmetrical around the middle. The geometry, mobility, forward/inverse kinematics, workspace, and parasitic motion of the mechanism are analyzed, showing its ability to achieve large rotations around a continuous rotation axis. Finally, a structure synthesis strategy for variable spherical symmetrical PM is proposed, and several limb types meeting the conditions are obtained.

Parasitic motion comparison of 3-PRS parallel mechanism with different limb arrangements

2011 ◽  
Vol 27 (2) ◽  
pp. 389-396 ◽  
Author(s):  
Qinchuan Li ◽  
Zhi Chen ◽  
Qiaohong Chen ◽  
Chuanyu Wu ◽  
Xudong Hu
Keyword(s):  
Parallel Mechanism ◽  
Parasitic Motion

Type Synthesis of Compound Load Simulators Outputting the Bending Moment and Tension/Compression Force

2014 ◽  
Author(s):  
Yufeng Qu ◽  
Jingjun Yu ◽  
Guanghua Zong ◽  
Shusheng Bi
Keyword(s):  
Parallel Mechanism ◽  
Bending Moment ◽  
Two Dimensional ◽  
Type Synthesis ◽  
Compression Force ◽  
Pure Bending ◽  
Loading Test ◽  
One Dimensional ◽  
Parasitic Motion ◽  
Compound Load

A bending moment and a tension/compression force are two types of commonly used load patterns in loading test for mechanical components. A great number of simulator types available for the two loads have been reported widely. However, current types mainly focus on the single load pattern and only one-dimensional bending moment can be achieved. With the increasing demand of the mechanical part performance, it is urgent to build a more complex testing environment. In this situation, a novel compound load simulator capable of outputting single multi-dimensional load and compound load patterns gradually catches the attention of the researchers. The development of parallel mechanism (PM) supplies a new direction to the field of simulators, whereas there is still shortage of effective types and design principles. In this paper, type synthesis of the compound load simulators outputting the bending moment and tension/compression force is introduced. First of all, the relationship between load patterns and degree-of-freedom (DOF) of parallel mechanism is derived. Based on the derivation, the DOF correspondence with a two-dimensional pure bending moment is two-dimensional rotation and that with a tension/compression force is one-dimensional translation. Furthermore, a typical 3-PRS PM as a representative of the PM with 2R1T DOF is studied and the analysis reveals that there is parasitic motion during its two-dimensional rotation. The undesired parasitic motion will bring additional load to the part, such as shear force. Then the special characteristics of PM meeting the requirement of outputting pure bending moment are proposed. Finally, a graphical approach is utilized to synthesize the effective types of the compound simulator.

An Articulated Robotic Forceps Design with a Parallel Wrist-Gripper Mechanism and Parasitic Motion Compensation

2022 ◽  
pp. 1-18
Author(s):  
Merve Bazman ◽  
Nural Yilmaz ◽  
Ugur Tumerdem
Keyword(s):  
Minimally Invasive Surgery ◽  
Motion Compensation ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Haptic Interface ◽  
Human In The Loop ◽  
Parasitic Motion ◽  
Motion Problem ◽  
4 Degrees Of Freedom ◽  
Orientation Workspace

Abstract In this paper, a novel 4 degrees-of-freedom articulated parallel forceps mechanism with a large orientation workspace (±/−90deg in pitch and yaw, 360deg in roll rotations) is presented for robotic minimally invasive surgery. The proposed 3RSR-1UUP parallel mechanism utilizes a UUP center-leg which can convert thrust motion of the 3RSR mechanism into gripping motion. This design eliminates the need for an additional gripper actuator, but also introduces the problem of unintentional gripper opening/closing due to parasitic motion of the 3RSR mechanism. Here, position kinematics of the proposed mechanism, including the workspace, is analyzed in detail, and a solution to the parasitic motion problem is provided. Human in the loop simulations with a haptic interface are also performed to confirm the feasibility of the proposed design.

Continuous motion of a novel 3-CRC symmetrical parallel mechanism

2015 ◽  
Vol 230 (3) ◽  
pp. 392-405 ◽  
Author(s):  
Ziming Chen ◽  
Wen-ao Cao ◽  
Huafeng Ding ◽  
Zhen Huang
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Parallel Mechanisms ◽  
Numerical Examples ◽  
Parasitic Motion ◽  
Continuous Rotation ◽  
Moving Platform ◽  
Motion Characteristics ◽  
Three Degrees Of Freedom

Parallel mechanisms (PMs) with three degrees of freedom (DOFs) have been studied extensively, especially the PMs with two rotational and one translational DOFs (2R1T PMs). One major problem of the 2R1T PMs is the inherent parasitic motion. In this paper, a novel 2R1T symmetrical parallel mechanism with no parasitic motion is proposed and studied. The moving platform and the base of this mechanism are mirror symmetric with respect to a mid-plane. This moving platform can realize continuous rotation about any axis or any point on the mid-plane and can have continuous translation along the normal line of the mid-plane. The constraint and motion characteristics of this mechanism are analyzed. The kinematics solutions and the Jacobian matrix are derived. The singularities of this PM are discussed. In the end, several numerical examples are given to show the continuous rotations and continuous translations of this PM. This kind of PMs has outstanding advantages of easy path planning and controlling.

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