Spatial lower-mobility parallel robots have received considerable schola- rs' attention of all the world and have a broad perspective in industry product- ion and other fields for the advantages of their simple mechanism, high stiffn- ess and low cost. In this dessertation, some kinematics characteristics of two lower-mobility parallel robot mechanisms that have existed are theoretically studied.(1)The forward position, the reverse position, the velocity and the acceleration of a 3-RRR spherical parallel mechanism are analyzed, the solutions of which and corresponding numerical examples are given. Many position, velocity and acceleration curves versus typical input are showed, which illustrate the kinematics characteristics. Some singular configurations are found when giving the position analyses.(2)The forward position and the reverse position of a 3-RRRRR 5-DOF parallel mechanism and corresponding numerical examples are given.(3)The spherical and analytical theory is used when solving the forward and reverse positions and it is convenient for solving some kinematics characteristics of some spherical parallel mechanisms because good corresponding relations are between them.(4)The DOFs of the 3-RRR and the 3-RRRRR parallel mechanisms are given by using screw theory. The general solution formula of DOF is deeply explained. The singular configurations got when analyzing the forward position before by applying the screw theory are validated.The research work of this thesis establishes theoretical basis for the further research of the two parallel mechanisms practically and give the theor- etical support for the future application. |