Extensible and Compressible Continuum Robot: A Preliminary Result

Continuum robot is with better flexibility and manipulability compared to traditional rigid multiple joints robot in operating in confined flexuose space. Among continuum robots, tendon-driven robot with compressible and extensible length has bigger working space than that of the non-extensible robot, though both of them can travel along the nonlinear spatial curved path. However, for the existing extensible robots, they realize extensible action based a pre-compression action, i.e., not from the natural no-load status for elastic components, like springs. This type of designs imposes restrictions on the length of the whole robot. In this paper, we present a novel tendon-driven continuum robot with extensible length from the natural no-load status for elastic components to overcome this limitation. The main contribution of our work is that the new design achieves extension based on extension of nitinol alloy super elastic bar from natural no-load status. Therefore, continuum robot based on this new design shows deeper reachability in natural orifices. Kinematic model of the proposed robot is derived and the workspace of the robot is demonstrated for one and two bending modules. A prototypical robot is built and its contractible and extensible performance is illustrated through experiments. This type of continuum robot may be useful in diagnosis and therapies for clinical scenarios, like laparoscopic surgeries and natural orifice transluminal endoscopic surgery (NOTES).