Synthesis and performance evaluation of manipulator-link using improved weighted density matrix approach with topology optimization method

Abstract

Topology optimization is recently employed for the design of light-weight manipulator-link that enhances energy-efficiency. However, the optimized topology at one angular-position is non-optimal for others because of dynamic loading. In this work, two approaches are proposed to synthesize ‘a single optimized topology’ that performs best for all angular-positions. The first approach is based on a weighted-density parameter, where highly sensitive elements are given high weightage to the final topology. The second approach is based on the superimposition of optimized topologies, followed by normalization and re-penalization to achieve desired volume fraction. An image-processing based techniques are also performed for reduction of stresses and geometrical complexities. 1-degree-of-freedom (DOF) manipulator-link is considered for topology optimization using an objective function as minimum compliance; deflection, stress, and torque are selected as performance values. The dynamic model is prepared considering the link-trajectory of 360° rotation. A 3-phase AC-servomotor and programmable logic controller based experimental setup are devised with online measurement of strain, torque, current, and position. The theoretical performance of the synthesized link using MATLAB code is validated through simulations (ANSYS-Workbench) and experiments. The synthesized-link through the proposed approaches shows similar deflection and 36% less stress compared to the conventional method. A reduction of 50% volume fraction minimizes joint torque by 43.6% within the permissible levels of a rigid link. The proposed method is illustrated on a 1-DOF link, which can be extended to the multi-DOF system and 3-dimensional links.