Design and characteristic analysis of a vacuum-powered soft actuator with endoskeleton reinforcement

Abstract Soft pneumatic actuators, as the core component of soft robots, have undergone substantial advancements recently. However, their weak output force and risks of explosion affect the manipulation reliability. In this study, we design a vacuum-powered soft actuator (VSPA), which incorporates an endoskeleton embedded within the internal chamber walls to achieve rigid-flexible coupling. Finite element model (FEM) and experiments are conducted to investigate the bending performance. Experiment results show that the maximum bending angle and output force are 100° and 340.44 mN, respectively. Compared with the actuator without endoskeleton reinforcement, the bending angle and output force of the VSPA are improved by 30.59% and 12.36%, respectively. The stability and lateral force are also improved significantly due to the endoskeleton reinforcement. Additionally, the FEM results match well with the experimental results. The mean error between the experimental results and FEM results is less than 6.03%. Based on the validated FEM, the bending performance of the VSPA with different parameters is studied. The bending angle and output force decrease with the increase of the thickness of the front and back wall, while increasing with the included angle. The growth of the thickness of the bottom wall leads to a decrease in the bending angle but an increase in output force. The thickness of the top wall has a slight effect on the output force. Finally, a three-finger gripper is developed, and grasping experiments are conducted to demonstrate the practical application of the VSPA. Consequently, this study will extend the research on soft actuators and offer an alternative for the actuation of soft robots.