Abstract: The displacement analysis of the general spatial 7R mechanism, which is an abstraction from the serial industrial robots, is regarded as one of the most difficult tasks in the kinematics analysis of spatial mechanisms. This problem is finally solved by Chinese scholars. There is dual relation between serial robots and parallel robots. The displacement analysis of 6-SPS parallel mechanisms is also a very difficult problem without substaintial progress made in the past ten years. A new method is presented to describe the rotation matrix. Through analyzing the coupling relationships between the moving platform position and attitude variables, eleven compatible algebraic equations used to solve this problem are obtained. Based on this, through eliminating the higher terms step by step, the problem of the forward kinematics analysis of 6-SPS parallel mechanisms can be finally expressed as a seventeen order algebraic equation, and maybe it is the best result of this kind of problem.

Key words: Analytical method, Forward kinematics analysis, Parallel mechanisms