Kinematic feature analysis of a 6-degree-of-freedom in-parallel manipulator for micro-positioning surgical

This paper presents a kinematic analysis of a parallel manipulator we have been developing for the micro-positioning application that requires high control bandwidth and high precision. The developed manipulator is a class of in-parallel platforms with 3 PRPS (prismatic-revolute-prismatic-spherical joints) chain geometry. The main advantages of this manipulator, compared with the typical Stewart platjorm type, are the capability to produce pure rotation and the easy prediction of the moving platform motion. The purpose of this paper is to develop an eficient kinematic model which can be used for realtime control and to propose systematic design methods that considers the existence conditions of the forward kinematic solutio,v, singularity, manipulability, and resistivity. A series of simulation are carried out to show the kinematic characteristics and performance of the mechanism. The proposed manipulator has potentials in a wide range of applicationsfiom micro surgery robots to highly dextrous wrist mechanism of assembly robots. Other configurations for parallel manipulators with six-degree-of-fieedom have also been proposed. Behi[G] developed a configuration with three legs where each leg consists of a PRPS chain. Hudgens and TesarL71 investigated a device with six inextensible legs where each leg is driven by a four-bar mechanism mounted on the base platform. Alizade et al.[8] proposed a parallel manipulator which has three legs, mounted on moving sliders passing through a circular trajectory. Although these modified Stewart platform mechanisms are developed to overcome some of disadvantages of the Stewart platform, previous works with these manipulators have shown few industrial applications. Particularly, only a few researchers have suggested designs of parallel manipulators with PRPS joint for industrial applications. This paper presents a kinematic analysis of a parallel manipulator we have been developing for applications that requires high control bandwidth and micropositioning such as micro-surgery and assembly of highly integrated semiconductors as shown in Fig. 1.