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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.

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Linkage mechanisms driven at constant angular velocity (CV) using a motor and flywheel have traditionally been used to produce fixed nonuniform motions. This type of system offers advantages of smooth motor torques, energy conservation and fast operational speeds. By incorporating a servo motor drive with a conventional CV drive in a two degree of freedom (DOF) linkage, the resulting hybrid machine can provide programmability. In this paper, two different hybrid mechanisms are optimally designed to provide a range of output motions with minimized torque and power requirements from the servo motor. The results are compared with those for a direct servo motor drive system.

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