Abstract: Loop circuit incremental method is applied to error analysis of multi-loop parallel mechanism, and presents the loop circuit selection principle. Based on D-H parameter and characteristics of mechanism with actuation redundancy, the error model of spherical 2-DOF parallel manipulator with actuation redundancy is established by virtue of loop circuit incremental method which includes both position error and posture error. In the error model, mechanical structural parameter error is considered, at the same time, considering the deviation between axis of each revolute joint and center of sphere from the reason of processing and assembling etc. These make the error model more close to actual project. Based on the error model, the reason of jammed phenomenon which spherical mechanism appears is further analyzed, and the mechanical error is estimated. This lays a theoretical foundation for kinematics calibration research of the prototype.

Key words: 2-DOF, Actuation redundancy, D-H transformation matrix, Error modeling, Spherical manipulator