Abstract:Comparing with the 3-DOF Delta mechanism, the 4-DOF parallel mechanisms which can achieve SCARA motion (i.e., three translations and one rotation) have their own complex topological structures with coupling degree k=2, which results in the higher complexity level of solutions for forward kinematics and dynamics. According to the design theory for parallel mechanisms (PMs) based on position and orientation characteristic (POC) equation and the principle for the coupling degree reducing, a novel 4-DOF SCARA type parallel manipulator with lower coupling degree of k=1 was proposed. Firstly, the structure of the 4-DOF SCARA PM was introduced and the coupling degree of the mechanisms was calculated as being k=1. Secondly, the direct position and the inverse kinematics problem of the mechanism was solved by using the modeling methods based on the ordered SOC unit, and the positive and inverse solutions were verified by numerical methods using Matlab. Furthermore, the workspace of the mechanism was analyzed based on inverse solutions formula. Meanwhile, rotation ability of the PM was analyzed. Finally, the singularity analysis of the mechanism was also performed based on Jacobian matrix, from which three kinds of singular conditions were obtained. The results showed that the manipulator had a simpler mechanical structure and larger workspace and rotation ability than H4 or Cross—Ⅳ under the same set of structural parameters. The research provided a theoretical base for its kinematics and dynamics and optimal design of this manipulator.