Analytical modeling and optimization of a corrugated soft pneumatic finger considering the performance of pinch and power grasps

Abstract For good adaptability and simple actuation, soft pneumatic actuators (SPAs) are increasingly used as fingers to make adaptable grippers. Due to low stiffness, the application of pneumatic grippers is mostly limited to the power grasp, while the precision (pinch) grasp has not been well studied. Although the SPA stiffness can increase with the pressure, low working pressure is required to ensure safe interaction with human. To address the stiffness issues and achieve a comprehensive performance improvement, the SPA finger design should be optimized. Focusing on dominant grasp indices, we propose analytical models to predict the bending pressure, tip force, distributed force, and torsional stiffness of a high-performance corrugated SPA Optimization is established based on the analytical models considering the daily grasps of the human hand. Accuracy of the models are verified with finite element simulations and physical experiments. The optimum fingers satisfy the optimization constraints on bending pressure, force, and twisting (out-of-plane bending). To evaluate the fingers performance in practice, a two-fingered gripper is made. Heavy loads up to 350g and 830g were successfully manipulated by pinch and power grasps respectively with the pressure below 50 kPa, which suggests a wider application for SPA grippers. Proposed modeling and optimization approaches are accurate and efficient, and have a high potential to prompt the applications of corrugated SPAs.