In the kinematic chain of the manipulator of the hydraulic excavators, the drive of the revolute pairs is carried out by a hydraulic cylinder jointed to the both links of the pair, which realizes a planar drive mechanism of the type - Inverted Slider-Crank Mechanism, centric type (ISCM). The power capabilities of the ISCM are described by the basic transfer function of the mechanism dS/dφ, which fully describes the driving moment of the ISCM in dimensionless form. The synthesis of this mechanism begins with a preliminary choice of the small parameter λ=R/L<1, equal to the ratio of the lengths of the links of the ISCM revolute pair. The synthesis then proceeds in a few steps. First, the two moment functions are fitting - the moment of the external forces and the driving moment of the hydraulic cylinder, respectively in their dimensionless form. So that for the entire considered range of ISCM, the driving moment of the hydraulic cylinder must be greater than the external moment. In this stage, all the angles of the mechanism are fully determined, as well as the coefficient K, which converts the external moment into a dimensionless form. This is followed by next step in which the cylinder force F and the ISCM metric - the lengths R and L of the rotary pair links, are determined. However, here the coefficient K=F.R defines the two unknowns in a product, which means that by choosing a standard cylinder force F_o, the dimension R is calculated from the above relation. This can be repeated several times until acceptable mechanism dimensions and a suitable cylinder are obtained. Several examples of the described synthesis are given: an external moment with equal values at both ends of the considered range and an external moment from the forces of gravity. Of course, optimization procedures can be performed at various points in the synthesis procedure.

synthesys, inverted slider-crank, drive mechanism, hydraulic excavators