Workspace analysis of cable-driven continuum manipulators based on static model

- The static model of continuum manipulators is proposed and experimentally validated.
- Workspace of continuum manipulators is analyzed based on the static model.
- Workspace obtained by the static modeling is payload dependent.
- The statics has to be considered in workspace analysis of continuum manipulators.

Cable-driven continuum manipulators are widely used in confined space applications, e.g. minimally invasive surgery. Different from conventional rigid manipulators, their end-effectors are positioned by deforming the flexible backbone. Existing workspace analysis of cable-driven continuum manipulators is based on kinematic modeling, in which the piecewise constant curvature assumption is adopted and the effect from external payload is fully neglected. In this work, we propose a method of analyzing the workspace using static analysis, which takes into account the internal cable tension, the external payload and the gravity force. Experiments are made through a continuum manipulator that is 90 mm in length and 7 mm in diameter to validate the proposed static model. Root-mean-square errors (RMSEs) are used to evaluate the differences between modeling and experiment. Results show that the average RMSEs along axial and lateral directions are 0.8 mm and 1.1 mm for the horizontal experimental layout, 0.4 mm and 0.1 mm for the vertical experimental layout. Based on the experimentally validated static model, workspace of a cable-driven continuum manipulator is analyzed. Results show that the workspace is much affected by the external axial force and lateral force, while is not affected by a pure bending moment. This indicates that the statics has to be considered in workspace analysis of continuum manipulators.