Analysis And Simulation Of Kinematics Performance Indices Of A New Coaxial Hybrid Mechanism

The helicopter is widely used in civil and military fields because of its vertical take-off, hovering in the air, autorotation and many other unique flight abilities. Comparing with the traditional single rotor helicopter, three blades coaxial helicopter has the advantages of compact structure, stable center of gravity and excellent maneuver ability. In recent years, with the demands of domestic helicopters continue to expand, three blade coaxial helicopter has draw increasingly attention in the field of small unmanned helicopter and had a broad prospect of application.Firstly, this paper introduced a reduced DOF coaxial hybrid mechanism which was the simplified equivalent mechanism according to the Kamov series three blades coaxial helicopter. This mechanism replaced the complex control lever with 3SPS+RRS+PS parallel mechanism which had 3 symmetric distributed SPS branches with the angle of 120°. As a result, the operating mechanism became more easily to control.Secondly, the kinematics analysis of the hybrid mechanism of coaxial was carried out, which mainly included DOF analysis, positive and inverse displacement solution, and velocity and acceleration analysis. Derivation of the following operating mechanism position equation could get the velocity and acceleration of the input components. The position relationships between the rotating ring space attitude, the moving chain and pitch hinge were analyzed at the same time.Additionally, the global performance index theory was used to analyze the kinematics character of the following operating mechanism to optimize the size of following operating mechanism. Relationship diagram between kinematics performance and the size of operating mechanism was mapped by MATLAB software. The speed performance of the coaxial hybrid mechanism, which was composed of the following operating mechanism and the following pitch hinge mechanism was then analyzed.The first order kinematic influence coefficient matrix of these two parallel mechanisms was established by using the method of virtual mechanism. Relationship diagram between speed performance and the size of coaxial hybrid mechanism was mapped as well. According to the diagram, dimension parameterwas optimized to realize a better performance.Finally, the 3D simulation model of coaxial hybrid mechanism of two different size parameters was built and simulated by PRO/E and ADAMS respectively.The comparison of speed fluctuation of two mechanisms was performed by ADAMS, which was in accordance with the theory result of speed performance of the coaxial hybrid mechanism.