Topology Optimization of Compliant Grippers Based on Stress Constraints

Abstract

This paper presents a topology optimization method of compliant grippers considering stress constraints. The proportional topology optimization (PTO) algorithm is applied to the design of compliant grippers, and it is improved by introducing weight factors into the objective function and adding stress conditions on the basis of constraints. In the current gradient modeling of topology optimization, the global maximum stress is measured by P-norm function, and its sensitivity analysis of stress constraints is derived by adjoint equations. It is worth noting that more rigorous gradient calculations are employed in stress problems and their computation brings an additional computational burden. By contrast, the non-gradient method using PTO algorithm allocates design variables to the element proportionally according to the values of stress. It can eliminate difficulties in the analytical derivation and calculation of gradient, and improve the calculation efficiency. Subsequently, performances of compliant grippers generated by these two methods are compared through finite element analysis. Finally, the optimized compliant gripper prototype is manufactured by three-dimensional (3D) printing using flexible thermoplastic urethane. Experimental results indicate that the non-gradient method is effective, and the optimized compliant gripper has excellent characteristics of low stress and high output performance.