Axial compression intrinsic sensing of continuum robot based on elastic modulus on-line estimation

This paper presents an axial compression intrinsic sensing algorithm of the primary backbone for continuum robot using superelastic NiTi backbones. The elastic limit of superelastic NiTi is much larger than that of ordinary materials, and it no longer obeys Hooke's law. Axial compression of pri-mary backbone is extremely small and has been found to have an important impact on the external force sensing accuracy of continuum robot using super elastic nickel titanium alloy backbones. Firstly, the dynamic model of the continuum robot is revised and the general formula for estimating the tension of multiple driving cables (more than 3) of the continuum robot in the presence of external forces are given. The value of the elastic modulus estimated online by quasi-static conditions is used with other generalized coordinates as the input of the axial compression intrinsic sensing algorithm, so as to obtain the estimated result of real-time axial compression. The method provides a feasible path for predicting the axial deformation of continuum robot while allowing for fast computation. Experiments present the results of intrinsic sensing of axial compression in the cases of three different driving forces.