Abstract

Based on screw theory and the principle of one- leg driving by an independent motor, a methodology for the structural synthesis of fully-decoupled three-rotational and one-translational (3R1T) parallel mechanisms is proposed by analysing the characteristics of the input-output relationships for fully-decoupled parallel mechanisms. Firstly, the desired forms for both the direct and the inverse Jacobian matrices of fully-decoupled parallel mechanisms are constructed by virtue of screw theory; this is in order to satisfy the demand that these two Jacobian matrices should be non-zero diagonal matrices. Secondly, the effective screw, the actuated screw and the mobile un-actuated screws of each limb are established via reciprocal screw theory, while all the possible topology structures fulfilling the requirements are obtained, based on different connectivities for each limb. Finally, the desired fully-decoupled parallel mechanisms can be synthesized using the structural synthesis rule, while the structural synthesis of fully-decoupled 3R1T parallel mechanisms can be obtained by exploiting the above-mentioned methodology. Moreover, the Jacobian matrix of a synthesized 3R1T parallel mechanism is deduced to demonstrate the decoupling feature of the parallel mechanism, which also validates the correctness of the methodology for the type synthesis of fully-decoupled 3R1T parallel mechanisms. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the 3R1T fully-decoupled parallel mechanisms. Motors are mounted one per leg, with each one of them actuating a one Degree-of-freedom (DoF) of the fully-decoupled parallel mechanism through a one-to-one velocity relationship.

Highlights

  • For more than two decades, parallel manipulator systems have become one of the research interests in robotics

  • As the authors are aware that most of the work reported above has dealt with the type synthesis of fully-decoupled parallel mechanisms with three-rotational DoFs or three-translational DoFs, respec‐ tively, much less work has been reported on the topic of the type synthesis of fully-decoupled 3R1T parallel mecha‐ nisms, which is the main contribution of the present paper

  • This paper mainly addresses the type synthesis of fullydecoupled 3R1T parallel mechanisms

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Summary

Introduction

For more than two decades, parallel manipulator systems have become one of the research interests in robotics. According to the expected kinematic characteristics of the fully-decoupled 3R1T parallel mechanisms, a method is proposed to synthesize the desired forms for both the direct and the inverse Jacobian matrices.

Basic Concepts of Screw Theory
The effective screw
The constraint screw
Instantaneous Kinematics Analysis of Fully-decoupled Parallel Mechanisms
Architecture Design for Four Legs of Fully-decoupled 3R1T Parallel Mechanisms
The first leg
The third leg
The fourth leg
Conclusions and Future Works
Full Text
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