Modeling and analysis of bending pneumatic artificial muscle with multi-degree of freedom

Bending pneumatic artificial muscles (BPAMs) are particularly promising candidates in the area of soft robotics. Most existing BPAMs that are capable of bending in a two-dimensional plane seem to be hardly suitable for the complexity and diversity of environments. In this paper, we design a BPAM with multi-degree of freedom (multi-DOF), which can bend in three-dimensional space and extend its soft body. And a static analytical model for bending in free space is proposed to give insights into the bending deformation of the BPAM. The bending angle predicted by the developed static model matches well with the corresponding experimental and numerical results, demonstrating the validity of the modeling method for the multi-DOF BPAM. We further validate that the developed model can reliably estimate the bending angle of the BPAM with different geometric parameters. Therefore, the developed static model can be employed as an effective tool for the guidance of the BPAM designs. In addition, a flexible and versatile gripper is fabricated by utilizing the BPAM, which shows an outstanding performance in grasping fragile, irregular, and deformable objects. Experimental results indicate that the maximum grasping mass is about 400 g when the operating pressure is 120 kPa. The developed multi-DOF BPAM also provides enormous potential for future applications that require motion and manipulation in three-dimensional space.