scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Mobility Change in Two Types of Metamorphic Parallel Mechanisms

01 Nov 2009-Journal of Mechanisms and Robotics (American Society of Mechanical Engineers)-Vol. 1, Iss: 4, pp 041007
TL;DR: In this paper, a new joint coined as the rT joint was proposed and two types of metamorphic parallel mechanisms assembled with this joint were proposed, i.e., a 3SPS-1 (rT)P(rT)-parallel mechanism with variable mobility from 3 to 6 and a 3RT-P(RT) parallel mechanism having various configurations including pure translations, pure rotations, and mobility 4.
Abstract: This paper presents a new joint coined as the rT joint and proposes two types of metamorphic parallel mechanisms assembled with this rT joint. In the first type, the mechanism changes its topology by turning the rT joints in all limbs into different configurations. This change in mobility is completed by two cases illustrated by a 3(rT)PS metamorphic parallel mechanism having variable mobility from 3 to 6 and a 3(rT)P(rT) parallel mechanism having various configurations including pure translations, pure rotations, and mobility 4. In the second type, a central strut with the rT joint is added in a parallel mechanism. The variable mobility of the mechanism results from the topological change of the central (rT)P(rT) strut. This is illustrated in a 3SPS-1 (rT)P(rT) metamorphic parallel mechanism, which changes its mobility from 4 to 5. It is demonstrated in mobility analysis that the change in local mobility of each limb results in the change in the platform mobility that a metamorphic process can be achieved. This particular analysis leads to advancement of improved Grubler-Kutzbach criterion by introducing the local mobility factor in the mobility analysis.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mobility and kinematics of the Hoberman switch-pitch ball, and particularly, its variant that does not resort to bevel gears.
Abstract: This paper investigates the mobility and kinematics of the Hoberman switch-pitch ball, and particularly, its variant that does not resort to bevel gears. The ball variant is a general case of the Hoberman switch-pitch ball and constitutes the ball. This paper starts from examining the geometry of the ball variant and its composition, and decomposes it into loops containing eight-bar radially foldable linkages. To investigate the eight-bar radially foldable linkage, constraint matrices are developed using the screw-loop equation. This paper extends the study to the ball variant and investigates the singularity and various configurations based on the geometry and kinematics of the ball variant. This leads to the investigation of the Hoberman switch-pitch ball as a special case of the ball variant with bevel gears to simultaneously drive three joints in every vertex of the ball mechanism. The analysis is then followed by a numerical demonstration of the kinematic characteristics of the Hoberman switch-pitch ball. DOI: 10.1115/1.4001730

90 citations

Journal ArticleDOI
TL;DR: In this paper, a reconfigurable modular parallel robot is presented, where the spherical joint which connects each leg to the end-effector is realized as a combination of revolute pairs; a locking system allows one to alternatively fix one of the revolute joints, giving the machine different 3-CPU kinematic configurations which correspond to different types of mobility.

90 citations

Journal ArticleDOI
TL;DR: In this paper, the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel mechanism with multiple operation modes was performed using the Euler parameter quaternions and algebraic geometry approach.

86 citations

Journal ArticleDOI
TL;DR: In this article, a unique feature of geometric constraint of adjacent axes of the variable-axis (vA) joint is presented, resulting in variation of mobility configuration of two 3SvPSv metamorphic parallel mechanisms.
Abstract: This paper presents a unique feature of geometric constraint of adjacent axes of the variable-axis (vA) joint and analyses the effectiveness in the constructed limb, resulting in variation of mobility configuration of two 3SvPSv metamorphic parallel mechanisms. The underlying principle of the metamorphosis of this vA joint is unravelled by investigating the dependence of the corresponding screw system comprising of line vectors, leading to evolution of the vA joint from the source phase Sv to the variable Hooke’s joint phase Uv and the variable revolute-joint phase Rv. The kinematic chain installed with the vA joint forms a reconfigurable limb and is then used to construct two 3SvPSv metamorphic parallel mechanisms proposed in this paper. The phase change of the vA joints incurs the constraint change of the SvPSv limb and subsequently results in the change of mobility configuration of the metamorphic parallel mechanisms. The paper further addresses the geometrical condition for constructing 3SvPSv metamorphic parallel mechanisms following the constraints delivered by the reconfigurable limbs, leading to the analysis of mobility change of the mechanisms induced by the phase change of the limbs.

84 citations

Journal ArticleDOI
TL;DR: In this article, a reconfigurable revolute (rR) joint was proposed for a metamorphic parallel mechanism based on three rRPS (r-R joint-prismatic joint-spherical joint) limbs.

84 citations

References
More filters
Journal ArticleDOI
01 Jun 1965
TL;DR: In this article, the authors describe a six-degree-of-freedom control with six motors, each having a ground abutment, for simulating flight conditions in the training of pilots.
Abstract: This paper describes a mechanism which has six degrees of freedom, controlled in any combination by six motors, each having a ground abutment. It is considered that by its particular arrangement, this mechanism may form an elegant design for simulating flight conditions in the training of pilots. Unlike most simulators, it has no fixed axes relative to the ground, and therefore within the limits of amplitude of the design it can truly simulate the conditions of banking by carrying the simulation of control surfaces into the axes of the new attitude.Variations in control arrangements are described and their respective design merits considered.Other possible uses for this mechanism are mentioned, including automation of production.

2,341 citations

Journal ArticleDOI
TL;DR: The Stewart Platform is one example of a parallel connection robot manipulator as discussed by the authors, and it has been used extensively in the past several years for a variety of tasks in the field of robotics.
Abstract: The Stewart Platform is one example of a parallel connection robot manipulator. This paper summarizes work that has been done at Oregon State University over the past several years on this topic. T...

820 citations

Journal ArticleDOI
TL;DR: A review of the literature on the six-degree-of-freedom parallel manipulator commonly known as the Stewart platform can be found in this article, where the authors highlight the distinctions of this class from the conventional serial robot manipulators and the novel perspectives that are necessary for the analysis and design of the Stewart platforms in particular and parallel manipulators in general.

637 citations

Journal ArticleDOI
TL;DR: In this paper, the authors revisited the concepts of Jacobian matrix, manipulability and condition number for parallel robots as accuracy indices in view of optimal design and showed that their real significance is not always well understood.
Abstract: Although the concepts of Jacobian matrix, manipulability, and condition number have existed since the very early beginning of robotics their real significance is not always well understood. In this paper we revisit these concepts for parallel robots as accuracy indices in view of optimal design. We first show that the usual Jacobian matrix derived from the input-output velocities equations may not be sufficient to analyze the positioning errors of the platform. We then examine the concept of manipulability and show that its classical interpretation is erroneous. We then consider various common local dexterity indices, most of which are based on the condition number of the Jacobian matrix. It is emphasized that even for a given robot in a particular pose there are a variety of condition numbers and that their values are not coherent between themselves but also with what we may expect from an accuracy index. Global conditioning indices are then examined. Apart from the problem of being based on the local accuracy indices that are questionable, there is a computational problem in their calculation that is neglected most of the time. Finally, we examine what other indices may be used for optimal design and show that their calculation is most challenging.

587 citations