Real-time Distributed Force Sensing-Based Position Feedback Control for Fiber-Driven Miniaturized Continuum Robots

Abstract

Continuum robots are widely used in the medical scenarios due to their dexterity and flexibility. However, precise end-to-end control of continuum robots remains challenging, limited by the kinematic or kinetostatic accuracy and no enough space for additional sensors configurations. This paper proposes a precise position control method for fiber-driven continuum robots using the reconstructed shape based on distributed force sensing from the same fibers, where the optical fibers serve as both robot actuation and force sensing simultaneously without requiring additional sensors. First, we use single-core optical fibers (SCFs) as the actuation cables of the continuum robot, and each fiber has multiple fiber Bragg grating (FBG) sensors inscribed on it to sense distributed force along the entire cables. Then, the forward kinetostatics model of the fiber-driven continuum robot is established using the known distributed forces as the inputs. Notably, the nonlinear friction between the cables and actuation channels does not require an additional estimation model. Benefiting from this, the shape can be accurately reconstructed after the stiffness calibration of the continuum robot. Finally, a position controller based on real-time feedback from shape is developed to achieve the tip position control of the continuum robot. Experimental results demonstrate that the proposed forward kinetostatics model can achieve the shape reconstruction with the errors of 0.45 mm and 0.57 mm in planar bending and spatial bending states, respectively. By comparison to the traditional constant curvature kinematics-based control method, the proposed methods can achieve the mean absolute error of 0.37 and 0.6 mm in two distinct path tracking tests. The proposed method using distributed forces sensing enables a real-time accurate position feedback control combined with kinetostatic model, instead of modelling the nonlinear friction or adding additional external sensors.