The Singularity Analysis Of3-PRUU Parallel Mechanism Based On Screw Theory

Parallel robotic, or called parallel mechanism, is an important branch of roboticsresearch; it is also one of the hot topics in the study of scholars at home and abroad. Butbecause the parallel mechanism has complex structure and its particularity, the study ofparallel mechanism still have quite difficulty. The singularity of parallel mechanism isabundant and complicated, is one of its important characteristics. It affects the mechanism’sperformance, such as kinematic, force, control and precision, is an important part of thestudy of theory of parallel mechanism.This paper researches a new kind of3-PRUU parallel mechanism by using screwtheory to turn motion pairs into motion screw, and further analysis of the parallelmechanism singularity.Firstly, this paper generally introduces the recent research about parallel robotics, theapplication of screw theory and the singularity. A series of achievements are introduced inthis paper.Secondly, according to the structure characteristics of the new type3-PRUU parallelmechanism, this paper reasonably set up the fixed and dynamic coordinate system, anddescribe the characteristics of the parallel mechanism in detail. Based on that,3-PRUUparallel mechanism s branch of motion screw is established, and the degree of freedom iscalculated.Thirdly, an overview of fundamental theories on singularity of parallel mechanisms isintroduced. And the singularity of the3-PRUU parallel mechanism based on the screwtheory is analyzed followed, which include kinematics singularity and constraint singularity.This paper divides the movement of the mechanism into only translational motion and onlyrotational motion, and discusses the singularity in these two cases.Finally, this paper does further researches about the conclusions which acquired in theprocess of analysis for the parallel mechanism.(1)using of special geometric structurecharacteristics of the UU hinge to reduce variables during the process of setting up branchmotion screw.(2)the rotation input is a constant value when the mechanism only translation.(3)the singularity for general orientation and general position.