Design and Validation of a Novel Fuzzy-Logic-Based Static Feedback Controller for Tendon-Driven Continuum Robots

Abstract

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 article, a slender tendon-driven CR (length/diameter: 715/12.7 mm) is introduced for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> 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 CR, in comparison with PCC-based method, validate the stability and universality of the developed controller, which can reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm 1 - $</tex-math></inline-formula> mm overall positioning accuracy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm 0.5$</tex-math></inline-formula> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</b> mm positional accuracy for 75% of the test points in both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> directions. Further, a set of trails on two distal sections of a long robot demonstrate that the controller can also effectively minimize the section coupling issue.