Design of Novel Cable-driven Continuum Robot for Fish Gait Emulation Using Kinetostatic Modelling Approach

Abstract The design of robotic fish is an active area of research due to their significant potential in unique underwater applications. Recent developments have suggested using flexible fish bodies for improved locomotion efficiency. The cable-driven continuum mechanism is one of the promising techniques that can be explored in this regard due to its inherent compliance. In this research, we have demonstrated that Cable-driven Continuum robots (CCRs) with actively controlled radial cable offsets can be used to emulate different types of Body and/or Caudal Fin (BCF) fish gaits. This capability to generate multiple fish gaits is enabled by our two main contributions: a novel kinetostatic model for CCRs with non constant radial cable offsets, and a novel robot design controlled by only two cables using an active cable routing mechanism. First, an accurate forward kinetostatic model of the CCR with varying radial cable offsets was developed. The model is shown to predict the deformed profile of a 420 mm long robot prototype with high accuracy. An inverse kine tostatic model was developed that can estimate the necessary routing characteristics of a CCR, given the required final profile of the robot. Finally, a novel robot of length 500 mm that can actively control the cable routing was designed and prototyped. Using the developed kinetostatic models, the robot is shown to emulate five BCF gaits with a maximum RMS error of 6.20 mm.