Study on Actuation Speed Improvement of Pneumatic Artificial Muscle with Exhaust Mechanism

Pneumatic actuators exhibit non-linear character- istics in their pressure response to input to electromagnetic valves. This is because the discharge speed of compressed air supplied to the actuator is slower than the charge speed. The objective of this study is to develop an exhaust mechanism that improves the driving speed of pneumatic artificial muscles and mitigates non-linear characteristics. The proposed exhaust mechanism consists primarily of a bellows and a check valve, driven by the pressure passing through them. The exhaust valve is installed at the tip of the artificial muscle, enabling pressure discharge to the atmosphere at the position closest to the artificial muscle. In experiments, the pressure response was compared when a rectangular wave voltage signal was input to the electro-pneumatic valve, verifying the validity of the proposed method. The results confirmed that the artificial muscle equipped with the developed exhaust valve exhibited a slight decrease in charge speed but a significant improvement in exhaust speed compared to the conventional method. Further optimisation of the exhaust valve design is expected to mitigate nonlinear characteristics in the future.