Ultiobjective Optimum Design of a 3-RRR Spherical Parallel Manipulator with Kinematic and Dynamic Dexterities

Guanglei Wu

doi:10.4173/mic.2012.3.3

Abstract

This paper deals with the kinematic synthesis problem of a 3-RRR spherical parallel manipulator, based on the evaluation criteria of the kinematic, kinetostatic and dynamic performances of the manipulator. A multiobjective optimization problem is formulated to optimize the structural and geometric parameters of the spherical parallel manipulator. The proposed approach is illustrated with the optimum design of a special spherical parallel manipulator with unlimited rolling motion. The corresponding optimization problem aims to maximize the kinematic and dynamic dexterities over its regular shaped workspace.

Highlights

A three Degrees of Freedom (3-DOF) spherical parallel manipulator (SPM) is generally composed of two pyramid-shaped platforms, namely, a mobile platform (MP) and a fixed base that are connected together by three identical legs, each one consisting of two curved links and three revolute joints
A multiobjective design optimization problem based on the genetic algorithm was formulated in order to determine the mechanism optimum structural and geometric parameters
The objective functions were defined on the basis of the criteria of both kinematic and kinetostatic/dynamic performances

Summary

Introduction

A three Degrees of Freedom (3-DOF) spherical parallel manipulator (SPM) is generally composed of two pyramid-shaped platforms, namely, a mobile platform (MP) and a fixed base that are connected together by three identical legs, each one consisting of two curved links and three revolute joints. The axes of all joints intersect at a common point, namely, the center of rotation Such a spherical parallel manipulator provides a three degrees of freedom rotational motion. Most of the SPMs find their applications as orienting devices, such as camera orienting and medical instrument alignment (Gosselin and Hamel, 1994; Li and Payandeh, 2002; Cavallo and Michelini, 2004; Chaker et al, 2012). They can be used to develop active spherical manipulators, i.e., wrist joint (Asada and Granito, 1985). In Ref. (Bai, 2010), the SPM dexterity was optimized within a prescribed workspace by identifying doi:10.4173/2012.3.3 c 2012 Norwegian Society of Automatic Control

Objectives

Methods

Conclusion