Qualitative Analysis and Exploration of a Novel Mechanism: Twisted String and Spiral Hose Mechanism

In the field of soft robotics, many intriguing robots incorporate helical deformation. Helical deformation possesses the advantage of flexibility, and there are various approaches to achieve it, such as Pneumatic Artificial Muscles (PAMs), magnetically actuator, tendon-like actuator and so on. In the other hand, Twisted String Actuators (TSAs), as a flexible actuation solution, can facilitate linear motion and have been applied in numerous robotic systems. In this study, helical deformation is combined with TSAs, a novel mechanism is proposed, it can achieve helical deformation very easy. The main components consist of a string installed within a hose, and the rotation of the string causes the hose to deform into a conical spiral shape. Experiments are conducted to validate and explore this intriguing deformation. Some interesting tentative conclusions are derived: when the rigidity of the string and hose is determined, a virtual conical surface is established. The rotation of the string continuously causes the hose to spiral upward on this virtual conical surface, and altering the length of the hose merely increases the height of the conical spiral shape without changing the cone angle. Experiments utilizing this mechanism for grasping objects were also conducted. Furthermore, some simulation computations are conducted.