Optimum structural design of a two-limb Schönflies motion generator

The optimum dimensions of a two-limb Schönflies motion generator, to maximize the overall stiffness of the robot structure is the subject of this paper. In the six-dimensional Cartesian space, for a mechanical system, six independent stiffnesses can be defined: three translational along three independent directions and three rotational about axes parallel to these directions. In this study, the objective is to maximize the maximum translational and rotational stiffnesses when the robot is at a specific pose. To this end, first, the stiffness matrix of the robot is obtained using the concept of the generalized spring; second, by introducing the translational and rotational stiffness indices κt and κr, respectively, two objective functions are defined. For the optimization procedure, a genetic algorithm (GA) is used. As a result, three different designs are introduced, their stiffness performance over a test trajectory then being analyzed. At the end, the sensitivity analysis of the robot stiffness with respect to some design parameters is studied.