Mobility Change in Two Types of Metamorphic Parallel Mechanisms

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 Grübler–Kutzbach criterion by introducing the local mobility factor in the mobility analysis.

Type Synthesis of 3-DOF multi-mode translational/spherical parallel mechanisms with lockable joints

“…(4) instead of Eq. (6), the approach presented in this paper can also be extended to the design of metamorphic PMs with reconfigurable joints or variable-axis joints [11][12][13] for generating two specified motion patterns.…”

“…A systematic study has also been made on metamorphic mechanisms [11] and metamorphic PMs [10,12,13,16]. For example, metamorphic PMs have been proposed by using reconfigurable U joint [10,12] and the variable axis joints [13].…”

Task-based structure synthesis of source metamorphic mechanisms and constrained forms of metamorphic joints

“…Zhang et al created a new metamorphic joint as a variable axis joint that can realize the change of the DOF between 1 and 3 so that three distinct kinematic pairs for constructing metamorphic mechanisms can be formed [12]. Gan et al invented a reconfigurable Hooke joint which can be utilized to change configurations for parallel mechanisms [13,14]. Also, Zhang et al proposed a new structure synthesis method to metamorphic mechanisms [15].…”

Unified Singularity Modeling and Reconfiguration of 3rTPS Metamorphic Parallel Mechanisms with Parallel Constraint Screws

“…Recently, some work has been done on metamorphic parallel mechanisms. Based on a reconfigurable Hooke (rT) joint, two types of MPMs were introduced [4] and detailed topology reconfiguration of an MPM with mobility change from 1 to 6 was investigated [19]. A general construction method for MPMs was introduced using screw theory [20] and a metamorphic parallel mechanism with ability of performing phase change and orientation switch was also proposed in [21].…”

“…In order to keep these advantages of traditional parallel mechanisms [2,3] but add additional adaptability, metamorphic parallel mechanisms (MPMs) [4] were developed. MPMs are a class of mechanisms that possess adaptability and reconfigurability to change permanent finite mobility based on topological structure change.…”