A novel wearable pouch-type pneumatic artificial muscle with contraction and force sensing

In this study, a novel pouch-type pneumatic artificial muscle for wearable applications with a high contraction ratio was proposed. It utilizes a rotary plate-belt mechanism to transfer the expansion of the folded pouch into the contraction of the belt. Modular design of the actuation unit enhances the adaptivity to multiple application scenarios. Based on the principle of virtual work, a force-contraction model considering energy loss was established and verified experimentally. Test results indicate that the actuation unit can attain a contraction force of 35.3 N and contraction ratio of 49.27%. Moreover, self-contained displacement and force sensing were designed, calibrated, and validated for this actuator. The good displacement tracking and force monitoring performance in the primary feedback control test proved the effectiveness of the self-sensing methods. Finally, surface electromyography (sEMG) of biceps brachii with actuator revealed that muscle activation could be reduced by 30.72% and 41.27% without and with 3 kg load, respectively.