Design and Modeling of an Extensible Soft Robotic Arm

Soft robotic arms are receiving more and more attention for their intrinsic safety and natural compliance. Instead of traditional serialized rotary joints, soft robotic arms often have complex joints with coupled degrees of freedom like bending, rotation, and elongation, enabling them with more freedoms in achieving sophisticated movements. However, currently soft robotic arms are mostly focusing on bending and rotation, whereas elongation is either unavailable due to the inextensible backbone or only has a small range because of the limited contraction ratio of actuators. Furthermore, the coupling of actuators and complex structure makes the modeling and control hard. In this letter, we introduced an extensible soft robotic arm with a large elongation ratio of 400%, and give a novel modeling method from a new perspective of the force balance of the arm. The models were experimentally tested both in loaded and unloaded situations, showing the effectiveness of predicting the bending, rotation, and elongation of the arm.