Design and validation of a novel fuzzy-logic-based static feedback controller for tendon-driven continuum robots

IEEE Continuum robots (CRs) outperform the conventional rigid-link manipulators in aspects of hyper-redundant and compliant features. They provide universal and efficient solutions to access to constrained environments, e.g., aero-engines and industrial vessels. In this paper, a slender tendon-driven continuum robot (length/diameter: 715mm/12.7mm) is introduced for in-situ maintenance of aero-engine combustors. Two control challenges, the piecewise-constant-curvature (PCC) assumption mismatch and sections coupling issues, are discussed to explain the defect of model-based kinematic controllers on specific designs. Then, inspired by the tug of war, a novel local model-less controller utilizing a fuzzy logic algorithm is proposed for the feedback control of a single section. This implements the control policies directly from the task space to the actuation space, avoiding the model mismatch of the PCC assumption owing to the explicit call of arc parameters. Experiments on a single section of the tendon-driven continuum robot, in comparison with PCC-based method, validate the stability and universality of the developed controller, which can reach 1mm overall positioning accuracy and 0.5mm positional accuracy for 75% of the test points in both X and Y directions. Further, a set of trails on two distal sections of a long robot demonstrate that the controller can also effectively minimise the section coupling issue.