Study on the effect of curvature radius sudden change on mechanism characteristics for the constant-breadth two circular-arc cam mechanism with an inclined flat-faced follower

Abstract

A two circular-arc cam mechanism is a special kind of constant-breadth cam. At the junction point of each cam contour, a mutation of the curvature radius may be produced, which affects the motion performance of the mechanism, especially its jerk performance at high speed. Based on a proposed motion model, the follower movements of the constant-breadth two circular-arc cam mechanism with an inclined flat-faced follower are analyzed. Bezier Curve is proposed to fit the driving law of the cam mechanism, while variable speed law is adopted to drive the cam mechanism motion, thus reducing motion characteristic value (AV)max (i.e., the maximum value of the velocity multiplied by acceleration for the follower’s motion law of the cam mechanism at the same motion time point) and the jerk of the follower. In this paper, the establishment of the optimization objective functions and constraint conditions, and the control node selections of the cam drive function are researched. The optimization results are obtained by using the primary objective method. The results of a test case calculation and simulation show that, the optimized drive function, according to the variable motor speed, can significantly reduce the value of (AV)max of the follower, while the jerks of the follower system are also reduced considerably. More precisely, the (AV)max value is reduced by 11.63% and the jerks are reduced on average by 15.35%, at the three jerk positions. The proposed methods provide a new approach to improving the kinematic performance of similar cam mechanisms.