Dynamic Analysis Of A2-PRS-PRRU Parallel Robot

Compared with the general6-DOF (degrees of freedom) parallel robots (PR),lower-mobility parallel robots have advantages of simple structure and design, lowercost in manufacturing and maintenance. The [PP]S parallel robot is an importantcategory of lower-mobility parallel robot which can undergo one translational DOFand two rotational DOFs. Thus, it has received extensive attention from internationalindustrial and academic circles and has great value in industry application.This paper focuses on dynamic analysis of a2-PRS-PRRU PR. The maincontributions are as follows.Based on the forward and inverse position analysis, the centroid velocity andangular velocity of each part is analyzed. The Jacobian of a2-PRS-PRRU parallelrobot is established.Based on the velocity analysis of each limb, the velocity mapping between thegeneral coordinate of moving platform and the centroid velocity and angular velocityof each frame member are established. Applied and inertial wrenches exerted on PRSlimbs and PRRU limb are analyzed respectively. Finally the inverse dynamicformulation is obtained by adopting virtual principle.Based on the analysis of driving force caused by each part mass and rotationalinertial on three limbs, a simplified dynamic modeling method is presented ignoringthe rotational inertias of two limbs. Thus, a simplified dynamic model is alsoestablished on the basis of virtual principle.A numerical simulation example is given where the extremity trace of tool is aspiral line. Another numerical simulation example of simplified dynamic modeling isalso given in contrast to the above dynamic modeling. The driving force of each limbcalculated by numerical simulation compared with the one that dynamic analysissoftware simulated, which verifies the inverse dynamic theory analysis.Based on the analysis of parallel robot singularity and spherical links constraint,the jigging motion range of PR at a fixed height is determined. Cartesian mass matrix is established and general inertial ellipsoids are depicted,which contribute to judgethe dynamical acceleration characteristic of points in workspace.The achievements stated in this thesis lay a solid theory foundation for therealization of dynamic optimal design and control.