Analysis And Synthesis Of Classic Lower-Mobility Parallel Manipulator

The parallel mechanism is a kind of robot structure which enjoys the advantages of high accuracy, rigidity, speed, and large load carrying capability. 6-DOF Stewart platform robot has been studied adequately and been used in many engineering domains. Nowadays, Low mobility parallel robot has drawn a lot of interest in the area of robot because of its simple structure, easiness to be controlled, low cost, and suitablility for many tasks requiring less than 6-DOF. In this dissertation, such items are studied: structure design, structure choice and kinematics of classic and applied 3 or 4 DOFs parallel mechanism, consulting the latest development of oversea parallel manipulator research. With analyzing their capability, workspace, locus layout, it tries to find the applied method of performance analysis and design for promoting low mobility parallel robot performance. Furthermore, experiment parallel mechanism is designed according the need of the experiment and education center.Topology structure of parallel manipulator is researched systematically in this dissertation. The twenty-seven topology structures of planar parallel mechanism are obtained according to the changing kinematic pair. The topology-structure-synthetised method based on single open chain(SOC) is also introducted. Many topology structures are obtanited by using this method, take some low coupling structures for example. It introduces the method of analysing parallel manipulator's nature, including the judgement for basic kinematic chain, the type of DOFs and the coupling of mechanism. Some classic types of 3 or 4 DOFs parallel manipulators proposed by scholars are analysed and compared. So their advantages and disadvantages are made clear through their practical use.The procedures for choosing optimal type of parallel manipulators are obtained according the basic performance request in practice. The best type of parallel manipulators is acquested accoding this mehtod.Symmetric planar parallel manipulator, classic 2T1R parallel manipulator and classic 1T3R parallel manipulator are analysed by the numbers including kinematic forward and backward analysis, workspace analysis, singularity analysis, velocity and acceleration analysis. The shape and the area of the workspace depending on different length of links are obtained. It is also obtained that the sisuations under which the planar parallel manipulator can get as much workspace as possible. The over constraint of planar parallel manipulator is studied, too. The method of formation and counting for over constraint is analysed. The over constraint of planar parallel manipulator is calculated. The structure with non-over-constraint of planar parallel manipulator is designed. And the self-adjustable displacement curve is obtained by simulating the adjustable mechanism of 3-RRR planar parallel manipulator.The input and output curve are obtained by the forward and backward kinematic simulation of 3-crank planar parallel manipulator model. The hybrid experiment platform with 4 axes is designed based on 2T1R parallel mechanism. The curve surface machining simulation is researched by modeling the platform and layouting the machining locus. The theory curve and simulation curve are compared by simulating the classic 1T3R parallel manipulator.