Research On The Design Of A6-DOF Serial-Parallel Precision Motion Stage

Precision motion stages (PMS) are applied in the fields of national defense,aeronautics and astronautics, biology and medicine, optics, mechanical manufacturingand many other areas, especially in optical path alignment which is increasing indemand. However, the existing precision motion stages have the limitations in travelrange, degrees of freedom and motion accuracy, which remain to be solved for furtherresearch.According to the demands of research project for precision motion stages in thelimitations mentioned above, this paper studies a kind of serial-parallel precisionmotion stage of six-degrees-of-freedom. The research of this paper mainlyconcerns:(1) the effect of three different structures of PMS on the performance of thestage;(2) modeling, analyze and evaluate the motion errors of each axis andcomprehensive error of the developed serial-parallel precision motion stage;(3) theresearch on the developed serial-parallel precision motion stage for the kinematicanalysis and simulation;(4) modal analysis on the structure of the developedserial-parallel precision motion stage.In order to figure out the effect of structural configurations on the performance ofthe developed precision motion stage, three kinds of structure configurations arecompared and analyzed:(1) parallel mechanism: aiming at a typical six degree offreedom parallel mechanism, motion simulation is studied by using Simulink inMatlab, and calculate the output position curve, the changed length of link andgeometric error characteristics;(2) serial mechanism: design a kind of serial motionstages six degrees of six-degrees-of-freedom specifically, and the size of themechanism and error characteristic are studied;(3) serial-parallel mechanism: by integrating the characteristics in serial mechanism and parallel mechanism organically,a kind of serial-parallel precision motion stage of six-degrees-of-freedom is designed,and its degrees of freedom, motion accuracy and motion accuracy are studied andanalyzed.Based on the existed products and technology, the structure of each motion axisis designed, and the motion error of each axis is analyzed. Then study the serial partand parallel part respectively. The error model of serial mechanism is established byusing the D-H method and general accuracy algorithm is adopted to carry out the erroranalysis and evaluation; Euler angle representations method is used to establish thegeometric error model of the parallel mechanism, which is analyzed and evaluated bythe method of orthogonal design. On the basis, the comprehensive geometric error ofthe serial-parallel precision stage is briefly analyzed and evaluated.It is important to analyze of the motion characteristics of the developedserial-parallel precision stage. First of all, it is to establish the series and parallelcoordinate system and to solve the position and orientation of the output of the model,and then the mathematical analysis is done. Secondly, the prototype model of themotion stage is built by using the software ADAMS. And the output characteristics ofthe prototype is solved, analyzed and evaluated by motion simulation.The modal analyzes for the parallel part of the serial-parallel precision stage ofsix degrees of freedom is done by the finite element analysis method. First of all, partsof the stage are simplified reasonably, especially the joints. And it draws thesimplified finite element model of the parallel mechanism; it is divided into gridsreasonably. Secondly, it draws the top ten order of formation and the correspondingnatural frequency of parallel mechanism by calculating and analyzing of using thefinite element simulation, and it is also analyzed and evaluated.According to the above analysis and research, the following four conclusionsindicate that the developed serial-parallel6-dof precision motion stage is able to breakthrough the existing similar institutions of the travel range, freedom and accuracy.(1)The workspace and accuracy of the parallel mechanism of6-dof still have limitations.The size of the serial mechanism is relatively large and the rigidity of that is inferior. And it is easy to emerge the cumulative error. But the serial-to-parallel hybridinstitutions are the organic integration of serial mechanism and parallel institutions. Itis easy to achieve a larger stroke and capable of precision positioning and having sixdegrees of freedom, so it is an ideal structure configuration.(2) The accuracy of eachaxis of motion achieved by designing and analyzing meets the demand of the research.From the geometric accuracy of view, the motion stage machine can achieve thedesired accuracy requirements, the unit axis positioning accuracy is still a majorfactor restricting the overall accuracy, and they are depended on the errorcompensation and installed base accuracy and other factors.(3) The kinematic analysisindicates that the development of string and serial-parallel precision motion stage canachieve the range of travel of the six degrees of freedom to move, and lay thefoundation for the path planning.(4) It obtains the natural frequency and orderformation of the actual structure of the system by the modal analysis of the parallelpart of the stage. And it provides a basis to design the stability-based stage.