Study On Topology Structure Design And Kinematics Of Lower-Mobility Parallel Robot

The parallel mechanism is a kind of robot structure. It has the characteristics of high accuracy, rigidity, speed, and large load carrying capability. 6-DOF Stewart platform robot has been studied thoroughly and been used in many industy domains. Nowadays, Low mobility parallel robot has drawn a lot of interest in the area of robot because of its simple structure, easy to be controlled, low cost, and suitable for many tasks requiring less than 6-DOF. In this dissertation, firstly, the toplogy stucture synthesis method of low mobility parallel robots are fully analysed, then, the designing method and steps of 4-DOF parallel robots are thoroughly studied, secondly, the kinematics of 2-RPS-2-SPS parallel robot are researched, finally, the aspect of over-constraint and adjustable structure design of low mobility parallel robot are discussed and the affection and application of partial freedom have also been anylased.. The most important basis of parallel robot design is the relations of DOFs between limbs and mobile platform. Based on the theory of displacement subgroup and its kinematic pairs, the S, G, C pairs can be substituted by more than one R or P pairs. Based on the concepts of kinematics bond and its mechanical generators, the principle of intersection and union operations of kinematics bond are discussed. So far, this dissertation prensents a systematic method for toplogical structure synthesis of lower mobility parallel robot. Using the theory mentioned above, the toplogical structure synthesis of 4-DOF parallel robot has beed researched thoroughly. Through the union operation of kinematics bond, many useful limb structures have been established, furthermore, many knowed and novel structures of 4-DOF parallel robots have been built by combining different limbs. It proves the correctness of the theory of toplogical structure synthesis of low mobility parallel robot. As an example, the following fields of 2-RPS-2-SPS parallel robot has been analysised: the selection of drivers, the kinematics. A novel 5 DOF parallel machine has been proposed. Using the Matlab programming language, simulation program has beed design, and the curve of driver dispalcement and the pose of the limbs are plotted based on the trajectory of moving platfrom, furthermore, the constant-orientation workspace also been obtained. On the point of view of uncertainty of constraint proposed by professor Huang, the over-constraint of lower mobility parallel robot has been researched, and the design method of zero over-constrainted adjustable mechanism is proposed. The affection and application of partial freedom has beed discussed. This disertation is sponsored by NSF project "Design and practice of adjustable mechanisms based on the uncertainty of planar constraint"and the new century education reform project "Study and practice of the reform of teachings on mechanical theory and experiment" sub projects" The development of parallel robot for experimentation ".