Performance Optimization And Type Synthesis Of Precision Positioning Parallel Platform

Positioning platforms that can reach micron, or even sub-micron and nano precision have been widly used in the fields such as micro-package, performance test of novel nano- material, etc. The purpose of this paper is to do some analysis about the performance optimization of 4-DOF precision parallel positioning platform and type synthesis of new-type parallel precision positioning platforms. On the basis of in-depth and systemic analysis on the researchs about precision positioning platforms at home and abroad, the performance optimization of positioning platform and type synthesis of nevol mechanisms are given based on the screw theory.In the paper, the kinematics of the 4-DOF parallel positoning platform used in SEM (Scanning Electronics Microscopes) is analysised; the parameters'optimization of the platform is discussed which taking the indexes of working space, dexterity, velocity into account. At last, the performance atlas of each index and a group of dimension parameters with better performance result.The error vector model of 4-DOF parallel positioning platform used in SEM is established. The main errors existing in the limb and their probability model are analysed. The impact of structure errors and location of upstage-limbs on the end-effector's positioning accuracy are discussed through emulational method based on Monte Calor method. In addition, the influences caused by exoteric load on the platform's stability with the structure error exiting are discussed.A macro/micro 4-DOF parallel mechanism, 4-PUPU mechanism, is proposed. The degrees of freedom, restraint property and kinematics of this mechanism are discussed.The type synthesis of dual-driven lower-mobility parallel mechanism is discussed using the restraint synthesis method based on screw theory. The synthesis flow and principles are given. Some dual-driven 3-DOF and 4-DOF parallel mechanisms result.A method for the lower-mobility parallel mechanisms'type synthesis is proposed. The mechanism's limbs are created by replacement of equivalent linkages under the same constrants. As example, the synthesis processes of spatial 3-DOF and 4-DOF parallel mechanisms are given, and some parallel mechanisms result.The research work of this thesis is of reference significances for the designing of second-generation 4-DOF precision positioning platform and novel lower-mobility dual-driven macro/micro positioning platforms.