The synthesis of hybrid five-bar path generating mechanisms using genetic algorithms

This paper presents a methodology for the synthesis of multi-degree of freedom mechanisms using genetic algorithms. A Five-Bar mechanism is a 2-DOF system which requires two inputs to fully describe the output motion. In a hybrid mechanism, one of these inputs is supplied by a constant velocity (CV) motor and one is supplied by a programmable servo motor. Such configurations can have considerable savings in power consumption, when the armature inertia of the servo motor is low when compared to the load inertia. In the presented synthesis of such mechanisms the two inputs required are provided by the CV input and the desired position of the end effector. The genetic algorithm is used to search for the optimum link lengths and ground point positions to minimise a multi-criteria objective function. The criteria which contribute to the objective function value are the error between the actual path of the end effector and the desired path, the mobility of the mechanism, and the RMS value of the servo motor displacements.