Design and analysis of skeleton-structured soft Pneu-Net actuators

Compared to rigid manipulators, Soft Pneu-Net Actuators offer greater flexibility, adaptability, and human-computer interaction. To address the issues of low stiffness and small tip contact force in traditional soft Pneu-Net actuators, this paper presents the design of a Skeleton-Structured Soft Pneu-Net Actuator, which consists of a chamber layer, a limiting layer, and a skeletal layer. A static analysis model is developed based on the virtual work principle, which relates the input pressure to the bending angle and tip force in free space, while preserving the nonlinear characteristics of the soft actuator. Additionally, the proposed modeling method fully accounts for the internal structure of the multi-cavity soft actuator, including the chamber layer, limiting layer, skeletal layer, membrane expansion contact, and the height variation of the actuator’s inflatable chamber. Drawing inspiration from the finite element method, the model utilizes zoning to reduce coupling and complexity, thereby improving prediction accuracy. Finally, finite element simulations and experimental measurements are conducted. The results demonstrate that the tip contact force of the Skeleton-Structured soft Pneu-Net actuator can increase by up to 60% compared to the traditional soft Pneu-Net actuator under the same air pressure. The theoretical model developed in this study effectively predicts the bending angle and tip force of the soft Pneu-Net actuator, with an error margin of less than 10%.