Topology Optimization of a Soft Pneumatic Actuator Considering Design-Dependent Loads

Soft pneumatic actuators (SPAs) have attracted increasing attention in recent years due to their lightweight and adaptable nature, making them ideal for applications requiring gentle interaction with the environment and objects. However, SPAs are typically subjected to design-dependent pressure loads, where the load's position and direction vary based on the actuator's geometry. As a result, traditional topology optimization (TO) methods, which typically assume fixed loads that do not vary with changes in design, are not directly applicable. Therefore, this article introduces a TO method that considers design-dependent loads for synthesizing air chambers in SPAs. A multicriteria objective function is presented to maximize the bending capability of the SPA, increase its stiffness against reaction forces when contacting an object, and maximize the allowable pressure input. Finite-element analysis is employed to evaluate the performance of the design. The results show that the optimized SPA achieves an average improvement of 119% in bending curvature compared to the commercial SPA. The prototypes are fabricated using 3D printing, and experimental results show that the output force of the developed SPA reaches 5.37 N at 100 kPa input pressure. In addition, the two-finger gripper designed with our SPA has a maximum payload of 1.78 kg.