Synthesis of Watt's six-link mechanism for manipulation action in relative space

A method for dimensional synthesis of symmetrical six-link Watt's mechanism is presented. The method is based on Chebyshev's best approximation theory. The dimensions of the links are determined by partial synthesis, which involves independent solutions for the crank, and the two dyads. The synthesis problem requires a path generator, since the point of interest moves along a symmetrical trajectory with given symmetrically changing velocity, as well as a necessary symmetrical orientation of the output link. In order to satisfy the conditions of the symmetry, a special topology (e.g. the Galloway's basic four-bar mechanism) is chosen. The method provides possibilities for pre-estimation of the structural error.