Analysis of the contraction performance of the bending contraction artificial muscle actuated by negative pressure

Artificial muscle is a kind of common soft driver. Among them, the ones actuated by negative pressure have some advantages in comparison with those actuated by positive pressure, such as naturally limited output force and greater safety. This paper has designed a bending contraction rigid-soft hybrid artificial muscle actuated by negative pressure. It consists of elastic contraction units made of TPU and reinforcements made of PLA. It is formed of several contraction units with equal volume through serial connection. Its deformation is affected by geometrical parameters, material properties, actuating pressure, load, etc. This paper has analyzed the contraction theories of the artificial muscle, then has researched the relationship between contraction performance (turning angle of the endplate) and material properties, actuating pressure, and load through simulation. In order to study the effect of material hardness, artificial muscles made of TPU with different hardnesses have been fabricated. In the load experiment, the artificial muscles with different loads are tested for getting the changes law of turning angle and actuating pressure. The results show that the turning angle increases with the increment of actuating pressure and decreases with the increment of load. But the effect of the hardness of the contraction unit can’t be ascertained. Finally, the artificial muscle has been applied to a soft gripper, and has realized several finger cooperation grasping experiments. The gripper can stably grasp a 2.4 kg load, evidently surpassing the one with a similar structure actuated by positive pressure, whose maximum grasping load is 0.786 kg.