Kinematic Characteristics Of Some Four-Mobility Parallel Mechanisms

Spatial imperfect-DOF parallel robots have received much attention for the advantages of their simple mechanism, low cost in designing, anufacturing, and controlling, comparing with traditional six-DOF parallel mechanism.Especially symmetric imperfect-DOF parallel mechanism with identical branch, symmetric construction, isotropy have great applicable potentiality.The research of two, three-DOF parallel mechanism have basically been finished, however the research of four, five-DOF parallel mechanism just begin, which limit the development and application of this kind of parallel mechanism to some extent. In this dissertation, some kinematics characteristics of three four-DOF parallel mechanism that have existed are theoretically studied.At first, the characteristics of three four-DOF parallel mechanism 4-RPUR, 4-RRRU and 4-UPU are studied, at mean time , the DOF of the 4-RPUR ,4-RRRU and 4-UPU parallel mechanism are given by using screw theory. The accuracy of choosing input is considered. Secondly, the kinematics of the four-DOF parallel mechanism are developed. The solution of the forward and inverse position kinematics and corresponding numerical examples are given, many position, velocity and acceleration curves typical input are showed, they illustrate the kinematics characteristics. Finally , the kinematics of the four-DOF parallel mechanism is simulated by using ADAMS.The research work of this thesis establishes theoretical basis for the further research of the four-DOF parallel mechanism practically and give the theoretical support for the future application.