Synthesis of the Four-Bar Double-Constraint Mechanisms by the Application of the Grubler's Method

The paper provides investigations on the structural synthesis of kinematic schemes of a spatial double-constraint mechanisms with one DOF. The investigations have been carried out with the use of the Grubler's method. The Grubler's condition for planar closed kinematic chains was developed for spatial chains including two general imposed constraints with consideration of relative movements and kinematic pairs. By means of introduction of two rotative joints, one screw pair and one cylindrical joint two different variations of spatial four-bar closed kinematic chains have been designed in the current investigation. Six kinematic schemes of non-isomorphic one DOF mechanisms have been designed from these two chains by fixing one link. The approach offered in this paper can be applied for the structural synthesis of spatial mechanisms from other families in accordance with the used kinematic pairs and numbers of imposed constraints. (C) 2016 The Authors. Published by Elsevier Ltd.