Design and Modeling of a Novel DNA-inspired Helix-Based Continuum Mechanism (DHCM)

Helix-based structures have been popularly used in flexible surgical tool designs due to their large bending range. However, the helix structures also have low compressional and torsional stiffness, which results in a limited payload. In this paper, we addressed these limitations by presenting a novel helix-based structure that mimicks the DNA double helix structure. This DNA-inspired helical continuum manipulator (DHCM) contains a helix structure and a constraint structure (a slender shaft or reinforced rings) that mimicks the base pairs of the DNA structure. Simulation results revealed that the stiffness of the helix structure is improved with the constraints. At the same bending stiffness, compared to the simple helix structure, the compressional and torsional stiffness of DHCM with the shaft constraint were improved by 12.3 times and 3.2 times, respectively. The kinematics of the DHCM were derived to predicate the deformation of the DHCM based on the piecewise constant curvature assumption. The model predicted deformation of the DHCM with a mean error of 4.16 mm (6.9%). The equivalent stiffness model of the DHCM was proposed and used to derive the statics of the DHCM. The mean error of distal end between statics predictions and experiment results was 1.01 mm (1.7%).