A Path Synthesis Method Of Planar Four-bar Linkage And Visual Expression

Linkage mechanism especially planar four-bar mechanism is usually used invarious types of machinery to realize the movement whose trajectory is known, forexample, transplanting mechanism of the rice transplanter, blender, cranes, etc in thepractical application. People have a continuous research on path synthesis method oflink mechanism, path synthesis of link mechanism is the basis of innovative design ofmechanical system, it has great significance both in academic research and engineeringapplications.In order to improve the speed and accuracy of path synthesis, planar four-barlinkage was used as the research object, a path synthesis method based on cubicnon-uniform B-spline curves’theory was proposed.Firstly, abundant data of coupler curves were generated, a normalization methodof coupler curves was proposed. The created original coupler curves were unifiednormalized which eliminated the correlation of coupler curves with scaling, the placedbearing, which also facilitate the characteristics matching of the path curve, greatlyreducing the redundancy of data in electronic atlas.Secondly, in order to avoid the sorting treatment of lots of shapes of couplercurves, the paper researched the selection method of shape points. The automaticallychoose programs of shape points were wrote, it greatly simplified the process of pathsynthesis.Thirdly, this paper put forward using closed cubic non-uniform B-spline curves tofitting coupler curves, and used angles between the two adjacent sides of the B-splinecurve control polygon as characteristic parameters of coupler curves. Angles betweenthe two adjacent sides of the B-spline curve control polygon in the process of backcalculation were used as characteristic parameters of coupler curves, which can bothrepresent the shape characteristic of coupler curves and reduce the number of the inputdata of artificial neural network, and as well can avoid to reduce the efficiency ofcharacteristics matching because of having too many characteristic parameters.Fourthly, using the generalized regression neural network for characteristicsmatching of path curves, the relationship between actual mechanisms with thedimension parameters of desired mechanisms was studied, and the antinormalizationmethod was proposed, which can quickly obtain the actual mechanism. The vectorgeneration method of cognate mechanisms of the actual mechanism was given,Robert-chebyshev theorem was proved by using geometry method. Mathematicexpressions of limit positions of the double rocker gear five-bar mechanism were studied and set up. A access method of rotating area of driving part in the doublerocker gear five-bar mechanism was shown.Finally, a visualization software was compiled using the above research results, itcan quickly implement the path synthesis of a certain number of ordered discretepoints which were given, and it has a high precision of path synthesis.