Structural Design And Performance Analysis Of Spatial Translational Compliant Micro-positioning Stage

Compliant mechanisms transmit force or motion by elastic deformation of the material,Therefore,clearance,friction,wear and return errors can be avoided,and the service life of the mechanism is prolonged.At the same time,they are free from lubrication,assembly and frequent maintenance,which is conducive to achieving stable and high-precision motion.Spatial translational compliant mechanism has a wide range of applications in micro-nano machining,micro-manipulation and three-dimensional scanning of atomic force microscopes and it is a key type of freedom in compliant mechanisms.Structural design and performance analysis of spatial translational compliant micro-positioning stage with excellent static and dynamic characteristics are hot and difficult points in this field.Therefore,this article has done the following research:(1)Firstly,series structure was compared with parallel structure in terms of kinematic accuracy,load capacity,working space and dynamic performance,and the research type of spatial translational compliant micro-positioning stage was determined to be a parallel structure.Then,the design requirements of spatial translational compliant parallel micro-positioning stage(STCPMS)with excellent-performance were clarified.Next,three common structural design methods for compliant mechanisms include rigid body replacement method,constraint-based design method,freedom and constraint topologies(FACT)method were introduced.Finally,integrating the advantages of the design methods mentioned above,a technology roadmap for structural design of high-performance STCPMS was proposed.(2)In order to solve the problem that the structure layouts of existing 3-limb STCPMS are not compact,and parasitic motion of each kinematic joint accumulates during multi-axis actuate,which leads to the augment of cross-axis coupling error.Firstly,an original structure of distributed compliance 3-PPP type STCPMS based on leaf beams was proposed by rigid body replacement method and FACT method.Then,its structure volume was reduced,and the parasitic motion accumulation phenomenon of prismatic joints was eliminated by structural optimization.Next,theoretical model of input stiffness was deduced by compliance matrix method.The validity of the theoretical model was proved by finite element simulation.(FES)Besides,natural frequency of the STCPMS was calculated,and the relationship between natural frequency of the STCPMS and size parameters of leaf beams was explored.Finally,comparative analysis of the STCPMS before and after structural optimization was conducted by FES.The results show that after structural optimization the volume of the STCPMS was reduced by 67% after structure optimization,its first three orders natural frequency are 94.5Hz,the coupling error is less than 0.39%,the lost motion is less than 0.09% and the STCPMS has better kinematic decoupling characteristic and input output consistency in both single-axis and multi-axis actuating.(3)In order to further improve the motion range and decoupling performance of the STCPMS.Firstly,an original structure of distributed compliance 3-PPPR type STCPMS was proposed by rigid body replacement method and FACT method.Then,a large-range 3-PPPR type STCPMS based on wire beam was proposed through structural optimization.Next,considering load stiffening effect under the condition of large motion range,nonlinear model of force-displacement relationship was established.The input stiffness model of the STCPMS was established by compliance matrix method,and its natural frequency was calculated.Finally,the theoretical model and static、dynamic performances of the STCPMS were verified and analyzed by FES.The results show that the first three orders natural frequency of the STCPMS are 44 Hz,it can achieve 1mm of motion range at least,the coupling error is less than 0.23% and the lost motion is less than 0.17%.(4)In order to further improve the output decoupling performance of the STCPMS.Firstly,new 5-PPPR and 4-PPP&PPPR type STCPMS with large motion range were designed using the compliant kinematic joints of the 3-limb STCPMS mentioned above.Then,theoretical model of the force-displacement relationship,input coupling and lost motion of the 4-PPP&PPPR type STCPMS was established by nonlinear method,and its stiffness and natural frequency model was established by compliance matrix method.Next,optimal parameter was searched to improve both static and dynamic performance of the STCPMS.Finally,the validity of theoretical model was proved by FES.The results show that the first order natural frequency of the STCPMS is 49.6 Hz.In 1 mm motion range,the lost motion is less than 0.32% in x axis and 0.7% in z axis,the input coupling is less than 1.2% and the output motion is completely decoupled.