Li Shihua

Huang Zhen

College of Mechanical Engineering,
Yanshan University,

Qinhuangdao 066004, China

Abstract: The instantaneous kinematics of a special 3-UPU parallel platform manipulator is discussed. First, the instantaneous motions of the 3-UPU manipulator in four kinds of positions and a special manipulator are studied by reciprocal screw theory. Then, the principal screws in one of four positions are obtained. It is shown that the moving platform has five degrees of freedom (DOF) in the initial position or after a translation along the z-axis; In the generic position, the mechanism only has three DOF, moreover the three DOF characteristics are different in different position. The instantaneous kinematic characteristics of alike 3-UPU mechanisms are very different in different position and special structure. The results presented are important to the use of alike 3-UPU parallel manipulator and contribute to the mechanism theory.

Key words: Parallel manipulator  Reciprocal screw  Principal screws  Instantaneous kinematic characteristics