Optimal Design System of Robot Structures Using Sensitivity Dynamical Characteristics

A computer-aided design system of robot manipulators has been developed, which is one of the subsystems of“TOCARD (Total Computer-aided Robot Design) ”system. This system determines the detail of robot structure (not only arm dimensions but also joint sizes and machine elements such as gears and chain transmissions) of any type of robot to minimize its total weight under the constraints of deflection and natural frequency, selecting machine elements from catalog data. In this system“sensitivity”is introduced to reduce man power and make interactive design efficient. The objective function for optimization, which consists of total weight, deflection, and natural frequency, is obtained applying the penalty method to the optimal design problem of this system; the sensitivity of design parameter is defined as the differential of this objective function with respect to the parameter variation. Using this sensitivity, a designer can pick up the most sensitive parameters for optimization. Furthermore, arm cross sections are automatically converged to their optimal solution by the penalty method after the other design parameters come near to their optimal value in the above-mentioned interactive optimal design step. These interactive and automatic steps permit efficient optimal design of robot structures.