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

Abstract

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, slidercrank 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.

A general method for the determination of the instantaneous screw axes of one-degree-of-freedom spatial mechanisms

“…In 2016, Kim et al (2016) presented a method for the determination of the instantaneous centers of velocity of planar mechanisms. The basis of their approach is to set up the equations for the solution of the velocity analysis of the mechanism, whose instantaneous centers are to be determined.…”

“…Instantaneous centers that can be determined by the application of the very same definition are denoted as primary. If the instantaneous center of rotation requires the application of the Aronhold-Kennedy theorem or other techniques such as the one proposed by Kim et al (2016) and generalized in this contribution are denoted as secondary.…”

“…It is important to note that despite the references cited by Kim et al (2016) all the mechanisms presented in their paper are determined; i.e. all their secondary centers can be obtained by using only the Aronhold-Kennedy theorem.…”

“…-In the last paragraph of the second column of page 1, Kim et al (2016) state "This method 1 is very intuitive from the geometry, but it has disadvantages of complexity in calculation and difficulty in determining the direc-tion of the linkage movement.". However, properly applied the application of the instantaneous centers of velocity can determine the direction of the linkage movement in an easy and straightforward way.…”

“…-In the fourth paragraph of the first column of page 2, Kim et al (2016) state "The method has three advantages in machine analysis. First, it can calculate the IC with a single representation for an arbitrary choice of fixed link.…”