A new instantaneous center analysis methodology for planar closed chains via graphical representation

Instantaneous center (IC) analysis of a mechanism is very important in mechanism analysis, since the analysis gives intuition about the global movement of the mechanism, and the analysis also makes the numerical analysis of velocities faster. Previous IC analysis methods have used geometrical information from the mechanism configuration. Such methods have disadvantages of complexity in calculation and difficulty determining the direction of linkage movement due to geometric complexity. This research suggests a new IC analysis method for planar closed chains. The proposed method determines the IC simply from the relation between joint velocities based on graphical representation. Twists in screw theory are used to define the joint velocities in a closed chain and also to calculate the IC. Three different kinds of mechanisms are analyzed by the method: a four-bar mechanism, slider crank mechanism, and a multiple closed-chain mechanism composed of four-bar and slider-crank mechanisms. The analysis methodology can be applied to calculate the ICs of various planar closed chains.This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2014R1A1A4A01009290)