Design, Fabrication, and Experiments of a Soft Pneumatic Gripper with Closed-Loop Position Control

Abstract

Soft pneumatic grippers (SPGs) contribute significantly to the development of soft robotic devices and help enable different and complex hardware designs for soft robots. Apart from the many advantages, the lack of position feedback of soft grippers presents a problem for position control. This study aims to examine this problem with the SPG, which is fabricated using additive manufacturing technology. The soft gripper is fabricated in two parts using the molding technique. The structure of the gripper consists of molded silicone (room -temperature-vulcanizing [room-temperature-vulcanizing]-3015) and polyethylene terephthalate (PET) film consisting of chambers. These sections are an active chamber consisting of 10 airtight sections that can be operated with compressed air and a passive chamber covered with PET film. During the bending of the SPG, the PET film inside the passive chamber begins to be compressed by the compressed air, resulting in a higher load-holding capacity of the gripper. In addition, the position of the feedback module made of flex sensor is integrated during fabrication. Various experiments were carried out to evaluate the performance of the SPG. Finite element analysis of the gripper was performed with COMSOL to compare the accuracy of realtime experiments. With the experimental studies' results, the SPG's motion characteristics, the relationship between the bending angle and the pressure, and the position-tracking performance were analyzed. Experimental results of the SPG were found to be in good agreement with the simulation results. The experimental results determined that the SPG showed successful trajectory tracking performance with the proportional-integral-derivative control algorithm. The root mean square value for the controller is calculated as 0.1245 degrees.