Journal of Bionic Engineering (2021) 18:1358–1368 https://doi.org/10.1007/s42235-021-00077-w

Design, Characterization and Optimization of Multi-directional Bending Pneumatic Artifcial Muscles

Wei Xiao1,2 · Dean Hu1,2 · Weixiong Chen1,2 · Gang Yang1,2 · Xu Han1,2,3 

1 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People’s Republic of China 
2 Key Laboratory of Advanced Design and Simulation Techniques for Special Equipment, Ministry of Education, Hunan University, Changsha 410082, People’s Republic of China
3 School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, People’s Republic of China

Abstract  Bending Pneumatic Artifcial Muscles (PAMs) are particularly attractive and extensively applied to the soft grasper, snakelike robot, etc. To extend the application of PAMs, we fabricate a Multi-directional Bending Pneumatic Artifcial Muscle (MBPAM) that can bend in eight directions by changing the pressurized chambers. The maximum bending angle and output force are 151° and 0.643 N under the pressure of 100 kPa, respectively. Additionally, the Finite Element Model (FEM) is established to further investigate the performance. The experimental and numerical results demonstrate the nonlinear relationship between the pressure and the bending angle and output force. Moreover, the efects of parameters on the performance are studied with the validated FEM. The results reveal that the amplitude of waves and the thickness of the base layer can be optimized. Thus, multi-objective optimization is performed to improve the bending performance of the MBPAM. The optimization results indicate that the output force can be increased by 7.8% with the identical bending angle of the initial design, while the bending angle can be improved by 8.6% with the same output force. Finally, the grasp tests demonstrate the grip capability of the soft four-fnger gripper and display the application prospect of the MBPAM in soft robots. 

Keywords  Pneumatic artifcial muscles · Multi-directional bending · Soft robots · Parameter optimization

Fabrication process of the MBPAM. Step1: fabricating the half of MBPAM with two open chambers. Step2: sealing the half of MBPAM with uncured silicone rubber. Step3: cementing the half of the unsealed MBPAM and the half of the sealed MBPAM together via uncured silicone rubber