Modal and Kineto-Elastodynamic Analyses of Balanced Four-Bar Linkages

This paper investigates the effects produced by two common techniques of force and static balancing on the dynamic performances of closed-chain linkages, taking into account the flexibility of the mechanism components. The long-term goal of the research consists in determining an optimal balancing strategy for parallel spatial manipulators. The present contribution is a starting point and it focuses on the planar four-bar linkage, intended as the simplest example of closed-chain mechanism. The dynamic performances of an unbalanced four-bar linkage and two balanced ones, respectively obtained by mass and elastic balancing, are numerically compared. The natural frequencies and mode shapes of these mechanisms are estimated by modal analysis, whereas the dynamic performances at three different operating regimes are assessed by kineto-elastodynamic investigation. The purpose of this study is to obtain preliminary results, to be refined and broadened in future developments.