Comparative Performance Analysis of 3DoF Spatial Parallel Manipulators

Abstract

The emphasis of this study is to compare two 3-Degree of Freedom Spatial Parallel newlineRobot Manipulators viz. 3-RRS Parallel Manipulator and 3-RPS Parallel Manipulator under newlinethe effects of the link tolerances and the parasitic motions. Both these manipulators belong to newlinethe 3-[PP]S family of the manipulators and have a common motion of 1T2R (T: Translation, newlineR: Rotation) type. These robots are used in machining devices, simulating motions, telescope newlinepositioning and coordinate measuring machines. They are also used to manipulate heavy newlinepayloads, and many times used as a base part of a hybrid manipulator. newlineThis study deals with a 3-RRS Parallel Manipulator and a 3-RPS Parallel Manipulator newlineboth are symmetrical in nature means their respective three legs are evenly distributed with newline120° between them. The planes of these manipulators are arranged in a Y-pattern such that they newlineintersect at 120° newlinein a common line and hence, they belong to the 3-[PP]S-Y family of the newlinemanipulators precisely. Both these manipulators have a fixed base and a moving platform newlinewhich are in the shape of equilateral triangles, and connected with each other by three identical newlinelimbs. Being a common motion of 1T2R type, the top moving platform of these manipulators newlinehas 3-Degree of Freedom i.e., translation along Z-axis and rotation about X and Y-axes. newlineFirstly, the mobility analysis is conducted, followed by the derivation of mathematical newlinemodels for both manipulators. Subsequently, the position kinematic analysis is performed for newlineeach manipulator, and the workspace analysis is carried out. Furthermore, the error analysis is newlineconducted, considering the effect of link tolerances, and the performance measure is examined newlineunder the effect of parasitic motions. Both these effects are unavoidable and need to be study newlineto reduce the errors at the design stage. In order to evaluate the performance measure, a newlineperformance index called as the parasitic motion index (PaMoI) is proposed. newlineSubsequently, a comprehensive comparison is conducted between two.