| Cam mechanism is mainly used for transmission, guidance and control components, andits kinematics and dynamics performance have a great influence on precision, efficiency,speed and other characteristics of automatic machine. By analyzing and reviewing theexisting related research achievements about cam mechanism at home and abroad, a newdesign and manufacturing method for cam mechanism was proposed. To improve thekinematics and dynamics of cam mechanism, profile of cam was reconstructed using non-uniform rational B-splines (NURBS) to meet all kinds of automatic machinery increasinglypursuit of high speed, high precision work.Considering its excellent global expression and powerful local regulation, NURBS hasaroused the attention in engineering field and has been applied in various fields. Firstly,Thispaper analyzed the mathematical model and the model characteristics of NURBS curve andsurface, and designed the NURBS curve and surface reconstruction process. The studyfocused on the geometric meaning and calculation method of control parameter node vector,power factor and control points, which affect the shape of curve and surface.Secondly, based on the study of NURBS curve and surface reconstruction method, a newdesign method was presented to reconstruct cam profile with NURBS. In order to improvethe spatial cam surfaces modeling and machining precision, the geometric characteristics ofspace cam were analyzed with ruled surface and offset surface theory. Applying the singleparametric curve enveloping theory, the profile equation of spatial cam was established anddiscrete point cloud data were obtained. Non-uniform rational B-splines has been adopted toreconstruct the profile of spatial cam. Based on the parametric feature model, the spatial camindexing mechanism was set up to perform kinematics simulation, and then the anufacturingmodel was generated to simulate the spatial cam NC machining.Thirdly, To improve dynamic characteristics of high-speed cam mechanisms，Non-uniform rational B-Spline was used to fit a modified-sine curve． Based on the SDOFelastic dynamic theory，a multi-objective dynamic optimization model for NURBS profilewas designed here． The multi-objective dynamic model was optimized to search a Paretooptimal solution with an improved artificial fish swarm algorithm，the optimized NURBS profile was acquired． The dynamic responses of a high-speed cam mechanism underNURBS profile and modified sine profile were analyzed and compared． The resultsshowed that the improved artificial fish swarm algorithm can effectively solve the multi-objective optimization problem. The optimized NURBS profile keeps the modified sineprofile’s fine kinematic characteristics，and the residual vibration is reduced. The high-speed cam mechanism designed by using this method has advantages of stable transmissionand lower noise．Finally, kinematic design was proposed for grooved cam plastic film collector using non-uniform rational B-splines. By considering Joint friction, a dynamic model of plastic filmcollector was established and the equation for calculating the contact stress was deducedusing Hertz contact theory. Taking the minimum contact stress and the minimumacceleration as the optimal objective, integrated design model for respective kinematic anddynamic design approaches was set up and optimized with an improved artificial fish swarmalgorithm. The results show NURBS profile has better kinematic and dynamic performances.The impact of the plastic film collector is reduced and wear characteristics are improved.The research results of this paper provide a new method for the design and manufacturingof cam mechanism, which promote cam mechanism research and development level in ourcountry, and has theoretical research value and application prospect in engineering. |
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