Type synthesis of the hybrid rotary platform mechanism with three degrees of freedom

Abstract

To improve the carrying capacity, a novel hybrid mechanism for rotary platform with three degrees of freedom (DOFs) is proposed, the serial mechanism is located on the moving platform (MP) of the parallel mechanism (PM), but its actuation system are located on the base, and the rolling motion is transferred by a motion transferring chain. The constraint wrench imposed on the upper MP of the hybrid rotary platform is analyzed, the type synthesis of the motion transferring chain was carried out using the constraint-synthesis method based on reciprocal screw theory. The relationship between input of the transferring chain and output of the upper MP is established, then the principle of transferring rolling motion by the motion transferring chain is explained. Finally, based on the motion transferring chain after optimization, two hybrid mechanisms for the rotary platform with three DOFs are obtained, which can meet the demands presented above.