Abstract:There is a wide range of industrial applications for the 4-DOF parallel mechanism which can achieve SCARA type output motion (i.e., three translations and one rotation). However, due to the complex topological structures, the research and development of its new model are still relatively few. Firstly, according to the parallel mechanism design theory and method based on the orientation characteristic (POC), a SCARA type parallel mechanism whose structure was simple was proposed. Because the coupling degree was 2, positive solution of position and dynamics calculation of the parallel mechanism were very complex. So the new model after structure coupling-reducing (k=1) was given, its positive solutions can be easily solved by one-dimensional search method. Then the three main topological characteristics of POC set, degree of freedom and the coupling degree were respectively analyzed. The kinematics analysis of the new model whose coupling degree was one after structure coupling-reducing was given, and the solution algorithm for the forward position of this parallel mechanism was established. This method can obtain all the numerical solutions of the forward position by using one-dimensional searching method, and can verify the correctness of the forward position by the derived calculation formula of the inverse position. Finally, based on the inverse position of the mechanism, the working space of this parallel mechanism was obtained and the singularity of the mechanism was discussed, which provided a theoretical foundation for the prototype design and application of this mechanism.