Multi-objective optimization of a three-stage displacement-amplifying compliant gripper based on NSGA-II

Abstract

To address the insufficient output displacement and local stress concentration of compliant grippers used in polarizer attachment and flexible film handling, this paper proposes a multi-objective optimization method for a three-stage displacement-amplifying compliant gripper using NSGA-II. A parametric model was established, and a surrogate model was constructed by combining finite element analysis, sensitivity analysis, central composite design, and response surface methodology. To improve the reproducibility of the optimization procedure, the normalized sensitivity coefficient, the prescribed input displacement and the nominal displacement amplification factor are explicitly defined. The optimization objectives were to maximize the output displacement of the gripping end and minimize the maximum equivalent stress. The results show that seven key design variables were selected through sensitivity analysis. Under an input displacement of 0.2 mm, the optimized design achieved an output displacement of approximately 0.480 mm, corresponding to a nominal amplification factor of 2.40. Compared with the initial design, the output displacement and nominal amplification factor were both improved by 20%, while the maximum equivalent stress remained within the allowable range. The proposed method provides a useful reference for the structural optimization of compliant grippers used for flexible film components.