Design and Analysis of Soft Bellows Actuators for Multi-Degree-of-Freedom Flexible Motion

Soft robots, due to their excellent compliance and adaptability, demonstrate great potential in applications such as grasping fragile objects, operating in unstructured environments, and human-machine interaction. However, existing silicone soft actuators often suffer from excessive radial expansion during movement, leading to instability. To address this issue, this study introduces a soft actuator with an outer bellows structure that limits radial expansion, enabling stable multi-degree-of-freedom movement. The design of the actuator's structure is first presented, including an analysis of the geometric model and deformation characteristics of the bellows actuator. A pneumatic control system with precise pressure regulation is then developed, and the relationship between pressure and deformation is experimentally tested. Finally, a soft robotic gripper and a three-segment soft robotic arm are developed based on the bellows actuator. Experimental results confirm the stability of the gripper during object manipulation and demonstrate the arm's flexible, multi-degree-of-freedom movement, significantly enhancing actuator stability.