Abstract：The dynamics characteristic of parallel mechanisms are very important. This study analyzed the dynamics of a 2UPU/SP parallel mechanism in a hybrid robot for aerospace composite machining. A kinematics model was developed using the virtual work principle for the three-degree-of-freedom parallel mechanism including the plane constraints of the two UPU kinematic branches. The maximum acceleration of the moving platform when one driving force is a unit force and the other driving forces are less than or equal to the unit force was used to evaluate the parallel mechanism. This performance index was used to separately evaluate the effects of linear acceleration and angular acceleration of the 2UPU/SP parallel mechanism compared with a traditional 2UPS/UP parallel mechanism. The results show that the present 2UPU/SP mechanism has better acceleration characteristics.
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