Abstract: Pneumatic soft actuators have broad application prospects in engineering fields. The whole deformation investigation on soft actuators used to be carried out mainly by adopting simple models such as beams and rods, which is different from hard contact of rigid materials. Therefore, the establishment of accurate mechanical models and analysis of the overall configuration and stress distribution for soft contact of soft actuators are still challenging conundrums. Aimed at the soft contact problem between two adjacent air chambers of a pneumatic soft actuator with multiple chambers, a novel modeling approach is proposed in this paper by combining the complexity of the air chamber structure with geometric and material nonlinearities, and employing the segment-to-segment contact method for multiple-point contact. It has solved the interpenetration problem between two adjacent air chambers without considering the contact interaction, which is suitable for analyzing soft structures with large deformation. Compared with traditional models like beams and rods, this model can not only improve the accuracy in simulating the overall deformation, but also accurately describe the stress distribution law inside the air chamber structure. The simulation results for the pneumatic soft actuator with multiple chambers demonstrate that the soft contact between adjacent air chambers has a remarkable effect on large deflection of the actuator. Finally, the quasi-static research on the whole process of grasping a cylinder by a soft four-claw mechanism is implemented, and the overall configuration variations and Mises stress distribution are elaborated in detail. The results show that the stress in the contact area reaches a maximum value. This paper is of theoretical guiding significance for the mechanical property analysis and optimal design of soft actuators.

Key words: pneumatic soft actuators with multiple chambers, soft contact, penetration, configuration and stress