The Eleventh International Conference on Machine Design and Production 13 - 15 October 2004, Antalya, Turkey OPTIMAL KINEMATIC DESIGN FOR A GENERAL 3-PRS SPATIAL PARALLEL MANIPULATOR BASED ON DEXTERITY AND WORKSPACE Yangmin LI, ymli@umac.mo University of Macau, Taipa, Macao SAR, P. R. China Qingsong XU, ma26678@umac.mo University of Macau, Taipa, Macao SAR, P. R. China ABSTRACT Optimal design of parallel robots is a crucial step ahead of manufacture and application. An optimal kinematic design for a general type of 3-PRS parallel manipulator is conducted in consideration of the performance of a weighted sum of global dexterity index and a space utility ratio - a new performance index. The Jacobian matrix is derived analytically and the manipulator workspace is generated by a numerical search method. Simulation results illustrate the necessity to introduce a mixed performance index using the space utility ratio for kinematic optimization of the manipulator, and the optimization process is carried out with the goal of reaching a compromise between the two indices. The analytical results are helpful in designing a general 3-PRS parallel manipulator, and the proposed design methodology can also be applied to architectural optimization of other types of parallel manipulators. 1. INTRODUCTION Parallel mechanical architectures were first introduced in tire testing by Gough, and later were used by Stewart as motion simulators. A parallel manipulator typically consists of a moving platform that is connected to a fixed base by several kinematic chains in parallel. A general six degrees-of-freedom (DOF) parallel manipulator has many advantages such as high accuracy, stiffness, and load carrying capability. However 6-DOF is not always needed in many situations. In recent years, parallel manipulators with less than 6-DOF, that maintain the inherent advantages of parallel mechanisms and possess several other advantages such as reduction of the total cost of the device including manufacturing and operations, are attracting attentions of many researchers. Various 3-DOF parallel manipulators have been designed and investigated for relevant applications [Clavel, 1988] [Lee, Arjunan, 1991] [Tsai, Walsh, Stamper, 1996].