Modeling and Characteristics Analysis of Intelligent Pneumatic Muscle with Shape Memory Alloy Braided Shell

Pneumatic muscles mimic function of human muscles and are used as robot actuators. The intelligent pneumatic muscle (IPM) with shape memory alloy (SMA) wires braided shell was proposed to improve characteristics. The mechanism was designed and prototype test-bench was made. Output force model was established through static force equilibrium analysis. The equation between temperature and contraction ratio of SMA wires was deduced through analyzing the volume ratio of Martensite to Austenite during crystalline structure transformation. This equation was adopted to get calculating methods of the contraction ratio, contractile force per cross-section area and variable stiffness of intelligent pneumatic muscle. Characteristics simulation was done on MATLAB and different pneumatic muscles’ characteristics were compared. The results show IPM has greater shell braided angle, greater contractile force and more flexible stiffness through adjusting SMA contraction ratio.