Theoretical Study Of 2RPR+SPS+SP Type Parallel Mechanism With Central Constrained Limb

In modern industry,parallel manipulator has the advantages of the high stiffness,low inertia,compact structure and wide application.Theoretical and experimental research on a variety of limited-DOF parallel manipulators is the research direction and advanced technology which domestic and foreign institutions to learn in recent years.Compared with 6-DOF parallel manipulator,the sub chain of limited-DOF parallel manipulator has the constrained forces / torques,so the limited-DOF parallel manipulator possess various kinematical characteristic in the process of movement.Due to characteristic flying,helicopter has been applied in civilian and military aspects broadly.the helicopter rotor system as the main lift sources also caused the attention of national experts.In this paper,a 2RPR+SPS+SP type 3-DOF parallel manipulator has been analyzed,including planar limb and intermediate passive constrained limb.First,the position analysis model of this parallel manipulator is obtained by using the vector method.The workspace of the parallel manipulator is described in a three dimensional software by the CAD variable geometry method.Second,based on arrangement of joints in the sub chains,the constrained forces / torques of the limited-DOF parallel manipulator are determined.The kinematic of these two kind conditions based on the theory of kinematic of rigid body are established,respectively,including Jacobian matrix and Hessian matrix.At last,the static and dynamic models of these two kind conditons are established based on the principle of virtual work.These models are verified by the simulation of advanced CAD software.Through the theoretical research on 2RPR+SPS+SP type 3-DOF parallel manipulator,combined with knowledge of the helicopter rotor,the components of the hinge moment of the rotor blade are analyzed and the relationship between the chang of the load and the chang of the draw rod is obtained.At the same time,the force of the parallel manipulator applied to the helicopter rotor blade is analyzed,which provides an effective basis for the application of the manipulator.