Synthesis, Design, and Prototyping of a Planar Three Degree-of-Freedom Reactionless Parallel Mechanism

2004 ◽  
Vol 126 (6) ◽  
pp. 992-999 ◽  
Author(s):  
Simon Foucault ◽  
Cle´ment M. Gosselin
Keyword(s):  
Parallel Mechanism ◽  
Degree Of Freedom ◽  
Numerical Verification ◽  
Dynamic Balancing ◽  
Synthesis Design ◽  
Reaction Forces ◽  
Three Degree Of Freedom

This paper addresses the dynamic balancing of a planar three-degree-of-freedom parallel mechanism. A mechanism is said to be dynamically balanced if, for any motion of the mechanism, the reaction forces and torques at the base are identically equal to zero, at all times. The proposed mechanism is based on legs consisting of five-bar parallelogram linkages. The balancing equations are first obtained. Then, optimization is used in order to minimize the mass and inertia of the moving links. Finally, a numerical verification of the dynamic balancing is provided and the prototype is presented.

Reactionless Two-Degree-of-Freedom Planar Parallel Mechanism With Variable Payload

2009 ◽  
Author(s):  
Alexandre Lecours ◽  
Cle´ment Gosselin
Keyword(s):  
Dynamic Simulation ◽  
Parallel Mechanism ◽  
Reaction Force ◽  
Simulation Software ◽  
Degree Of Freedom ◽  
Dynamic Balancing ◽  
End Effector ◽  
Planar Mechanism ◽  
Two Degree Of Freedom ◽  
Arbitrary Trajectory

A reactionless mechanism is one which does not exert any reaction force or moment on its base at all times, for any arbitrary trajectory of the mechanism. This paper addresses the static and dynamic balancing of a two-degree-of-freedom parallel planar mechanism (five-bar mechanism). A simple and effective adaptive balancing method is presented that allows the mechanism to maintain the reactionless condition for a range of payloads. Important proofs concerning the balancing of five-bar mechanisms are also presented. The design of a real mechanism where parallelogram linkages are used to produce pure translations at the end-effector is also presented. Finally, using dynamic simulation software, it is shown that the mechanism is reactionless for arbitrarily chosen trajectories and for a variety of payloads.

Novel Design and Analysis of a Fully Decoupled 3-DOF Spherical Parallel Robot

2009 ◽  
Author(s):  
Dan Zhang ◽  
Fan Zhang
Keyword(s):  
Physical Meaning ◽  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Parallel Robot ◽  
Degree Of Freedom ◽  
Redundant Constraints ◽  
Rotational Motions ◽  
Three Degree Of Freedom ◽  
Novel Design

In this paper, we propose a unique, decoupled Three Degree-of-Freedom (DOF) parallel wrist. The condition required for synthesizing a fully isotropic parallel mechanism is obtained based on the physical meaning of the row vector in the Jacobian Matrix. Specifically, an over-constrained spherical 3-DOF parallel mechanism is presented and the modified structure, which avoids the redundant constraints, is also introduced. The proposed manipulator is capable of decoupled rotational motions around the x, y and z axes and contains an output angle that is equal to the input angle. Since this device is analyzed with the Jacobian Matrix, which is constant, the mechanism is free of singularity and maintains homogenous stiffness over the entire workspace.

A 3-ṞPR Parallel Mechanism With Singularities That are Self-Motions

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Novona Rakotomanga ◽  
Ilian A. Bonev
Keyword(s):  
Parallel Mechanism ◽  
Control Strategies ◽  
Joint Space ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Active Joint ◽  
Cartesian Space ◽  
Three Degree Of Freedom

The Cartesian workspace of most three-degree-of-freedom parallel mechanisms is divided by Type 2 (also called parallel) singularity surfaces into several regions. Accessing more than one such region requires crossing a Type 2 singularity, which is risky and calls for sophisticated control strategies. Some mechanisms can still cross these Type 2 singularity surfaces through “holes” that represent Type 1 (also called serial) singularities only. However, what is even more desirable is if these Type 2 singularity surfaces were curves instead. Indeed, there exists at least one such parallel mechanism (the agile eye) and all of its singularities are self-motions. This paper presents another parallel mechanism, a planar one, whose singularities are self-motions. The singularities of this novel mechanism are studied in detail. While the Type 2 singularities in the Cartesian space still constitute a surface, they degenerate into lines in the active-joint space, which is the main result of this paper.

Active Control for the Complete Dynamic Balancing of Linkages

1992 ◽  
Author(s):  
Jorge Angeles ◽  
Meyer A. Nahon ◽  
Thomas Thümmel
Keyword(s):  
Active Control ◽  
Degree Of Freedom ◽  
Dynamic Balancing ◽  
Reaction Forces ◽  
The Masses ◽  
Inertia Forces ◽  
Shaking Moment

Abstract This paper deals with the dynamic balancing of linkages. For one-degree-of-freedom linkages, this task consists of eliminating both the shaking moment and the shaking force exerted by the inertia forces of the moving links on the frame. While the latter can be eliminated by properly deciding on both the location of the mass centers and the ratios of the masses and link lengths involved, the shaking moment due to these forces cannot be eliminated in this way. Indeed, the elimination of the shaking force is attained by having the two transmitted forces cancel each other, although each individual force does not necessarily vanish, thereby still producing a shaking moment. In this paper, we propose the use of redundant motors in order to eliminate the reaction forces transmitted to the base, thereby also eliminating the shaking moment due to these forces. However, the net moment acting on the frame is shown to be unaltered by this technique.

Design of a Redundantly Actuated Asymmetric Linear DELTA Parallel Mechanism for Singularity-Free Mode Changes

2014 ◽  
Vol 575 ◽  
pp. 711-715 ◽  
Author(s):  
Takashi Harada
Keyword(s):  
Numerical Simulations ◽  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Degree Of Freedom ◽  
Moving Plate ◽  
Mode Change ◽  
Redundantly Actuated ◽  
Free Mode ◽  
Linear Actuators ◽  
Three Degree Of Freedom

A novel parallel mechanism which enlarges the workspace by singularity-free mode change is proposed. The proposed mechanism is inherited the design of Linear DELTA which has three degree-of-freedom translational moving plate driven by three linear actuators, in addition, extended it by redundantly actuation by four linear actuators and asymmetric design. New criterions about redundancy and singularity of redundantly actuated parallel mechanism using summation and product of determinants of minor matrices of the transposed Jacobian matrix are proposed. Redundantly actuation and asymmetric design enables singularity-free mode changes with loss redundancy but maintain non-singularity, that are evaluated by the proposed criterions. Numerical simulations demonstrate the singularity-free mode changes of the proposed mechanism.

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