The Main Geometric Tolerance In The Nipper Plate Mechanisms Dynamics Analysis

Planar Linkage mechanisms are used widely in engineering,planar mechanisms are the most important objects of study in mechanical theory and methods.The widely overconstraints in the mechanisms will make the quality of the mechanism sensitive to the inevitable manufacturing and assembly errors.Generally it caused the movement of the "obstacle" and systems of certain components of deformation and movement of deputy additional dynamic load,and caused mechanical vibration,shock, noise and so on.Reducing mechanical efficiency and working performance.As the impact of the planar widespread mechanism overconstraint,planar mechanisms in theory exist overconstraint,so the planar movement and force analysis in theory should be in accordance with the spatial models.Tolerance in the past study and the distribution of size tolerance and tolerance level of study have also been made very good results,the past mechanical analysis was apt to rigid bodies,but it paid less attention on the geometric errors in mechanisms,sometimes the tolerance size distribution met the requirements,at the same time still found it difficult to meet the requirements of dynamics request.Geometric tolerance was based on past experience, not a generic dynamics effectively design standards.In this case,the geometric tolerance researches gain more and more experts and scholars' attention.In this paper,planar linkage is the main study object,overconstrainted mechanisms formula were used to analyze the relationship between overconstraints and freedom.the formula determine the existence the number of statically indeterminate and over-constraint.and then built the corresponding deformation equations.Using Structural mechanics to deal with statically indeterminate structure stress analysis method,based on the bar as the elastic rod processing,through the analysis of mechanism deformation conditions,based on the kinematic pairs azimuth error changes between theory error and actual ones,put forward a kind of quantitative methods that kinematic pairs errors exist,so as to structure design and its precision design provides a theoretical basis.In this paper,the analysis of four bar mechanisms use the quasi-static analysis, assume that the mechanism rotates a specific location,fix a pair of mechanism,it will be in accordance with the four truss analysis,the existence of form and position errors of the bar as a system,construct a set of system equations,the four bars' acting force translate into the system's internal stress.Through the analysis of a complete set of geometric tolerance approach,used in combing machine main motion mechanisms, through the institutional structure of the simplified analysis of the dynamic properties of the impact of the largest geometric tolerance,establish some relationships between tolerance and dynamic stress.Finally,the application of ADAMS software,set up an existence errors model of four bars closed chain mechanisms,using error dynamic simulation,Showing the dynamic performance to existing errors of kinematic pairs mechanisms from the perspective of qualitative and quantitative description.