A Soft Pneumatic Actuator with Multiple Motion Patterns Based on Length-tuning Strain-limiting Layers

Soft pneumatic actuator with strain-limiting layers has played an important role in soft robotics in the last decades. However, limited by their pre-designed and permanent strain-limiting layers, their motion pattern is usually single. Here, we proposed a soft pneumatic actuator with multiple motion patterns based on length-tuning strain-limiting layers. We integrated 4 cable-based strain-limiting layers into a 3D printed soft pneumatic actuator. A cable locking system is proposed to lock the cables as strain-limiting layers. The system is actuated by a small fabric balloon and can provide up to 79 N blocking force. With a rotatory sensor, it can also monitor the actual length of the cable. The soft pneumatic actuator can achieve omnidirectional bending and extension by regulating the state of the 4 cable locking systems. By experiments, we verify the work principle of cable locking system. The actuator here can also vary its stiffness from 6 N/m to 97 N/m by antagonism.