Abstract
Most parallel mechanisms (PMs) encountered today have a common disadvantage, i.e., their low rotational capability. In order to develop PMs with high rotational capability, a family of novel manipulators with one or two dimensional rotations is proposed. The planar one-rotational one-translational (1R1T) and one-rotational two-translational (1R2T) PMs evolved from the crank-and-rocker mechanism (CRM) are presented by means of Lie group theory. A spatial 2R1T PM and a 2R parallel moving platform with bifurcated large-angle rotations are proposed by orthogonal combination of the RRRR limbs. According to the product principle of the displacement group theory, a hybrid 2R3T mechanism in possession of bifurcated motion is obtained by connecting the 2R parallel moving platform with a parallel part, which is constructed by four 3T1R kinematic chains. The presented manipulators possess high rotational capability. The proposed research enriches the family of spatial mechanisms and the construction method provides an instruction to design more complex mechanisms.
Highlights
1 Introduction Parallel mechanisms have been extensively researched over many years, depending on their advantages of high speed, high accuracy, large stiffness and heavy-load capability in comparison with the serial counterparts
Several approaches for the structural synthesis of parallel mechanisms (PMs) have been proposed. They are the enumeration approach based on the general mobility formula [4, 5], the constraint approach based on the reciprocal screw theory, the synthesis approach based on the Lie group theory [6,7,8], and the approach based on the theory of linear transformations [9]
PMs suffer from the problems of having relatively small useful workspace and limited rotational capability, which are crucial for their performance and applications [10]
Summary
Parallel mechanisms have been extensively researched over many years, depending on their advantages of high speed, high accuracy, large stiffness and heavy-load capability in comparison with the serial counterparts. Different limbs are connected with the degenerate CRM to synthesize a series of planar and spatial PMs with large rotational angles in terms of displacement group theory.
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