Abstract: An optimal synthesis method of adjustable spherical Stephenson Ⅲ six-bar mechanisms for multi-path generation is put forward. Based on kinematic synthesis of spherical Stephenson Ⅲ six-bar mechanisms, a set of nonlinear equations of multi-path kinematic synthesis for adjustable spherical six-bar mechanisms is established. The relationship of the number of tasks, the number of coupler positions, and the number of arbitrary choice of parameter are analyzed. In order to make the crank be continuous rotation one-way and the mechanisms have good transmission quality, the condition of crank existing of the spherical Stephenson Ⅲ six-bar mechanisms is deduced, and the formula of transmission angle is derived. The mathematical model for optimization is presented, and a virus evolution genetic algorithm is utilized to obtain the global optimal solution. The virus evolution genetic algorithm has good convergence speed and convergence stability, which combines dynamically main group’s overall evolution with virus group’s local evolution. It can be ensureed to obtain the global optimal solution of the mechanism synthesis. A numerical example is given to illustrate the effectiveness of the proposed method.

Key words: Adjustable mechanisms, Path synthesis, Spherical six-bar mechanisms, Virus evolution genetic algorithm