FBG-Based Control of a Continuum Manipulator Interacting with Obstacles

Abstract

Tracking and controlling the shape of continuum dexterous manipulators (CDM) in constraint environments is a challenging task. The imposed constraints and interaction with unknown obstacles may conform the CDM's shape and therefore demands for shape sensing methods which do not rely on direct line of sight. To address these issues, we integrate a novel Fiber Bragg Grating (FBG) shape sensing unit into a CDM, reconstruct the shape in real-time, and develop an optimization-based control algorithm using FBG tip position feedback. The CDM is designed for less-invasive treatment of osteolysis (bone degradation). To evaluate the performance of the feedback control algorithm when the CDM interacts with obstacles, we perform a set of experiments similar to the real scenario of the CDM interaction with soft and hard lesions during the treatment of osteolysis. In addition, we propose methods for identification of the CDM collisions with soft or hard obstacles using the jacobian information. Results demonstrate successful control of the CDM tip based on the FBG feedback and indicate repeatability and robustness of the proposed method when interacting with unknown obstacles.

A Contact Force Sensor Based on S-Shaped Beams and Optoelectronic Sensors for Flexible Manipulators for Minimally Invasive Surgery (MIS)

“…Recently, state-of-the-art flexible manipulators [23][24][25][26][27][28] have integrated various sensing modalities such as shape and stretch sensing units, tactile sensing units and multi-axis force/torque sensors. For example, the continuum manipulators are integrated with light intensity modulation based fibre optic sensors to measure force/torque [19,23] as well as the manipulators' shape [29] based on stretch sensing elements [49].…”

“…However, it is typically difficult to miniaturise the overall size of the manipulator due to the space needed to house the optical fibres. The Fibre Bragg Grating (FBG) sensing elements are widely used to measure contact forces and the shape of the flexible manipulators [25][26][27]. This element helps to cut down the size of the manipulator without the loss of outstanding sensing modalities.…”

“…This structure can measure contact force components in every segment and estimate arbitrary shapes using orientation information. Conventional shape sensing methods employing fibre optic and FBG assume constant curvature model [25][26][27] whereas our approach does not need such an assumption since an arbitrary shape can be estimated by composition of a series of relative orientation matrices. Consequently, this may achieve precise closed-loop motion control as well as acquisition of accurate contact force information [31][32][33].…”

Variable Stiffness Model Construction and Simulation Verification of Coupled Notch Continuum Manipulator

“…The kinematics model of the continuum manipulator is usually established using the hypothesis of constant curvature or piecewise constant curvature [2], [3]. Armand [4]- [6] et al developed a nested continuum, which cut the rectangular notch on both sides of a Nitinol tube. The kinematic model is obtained through the assumption of constant curvature.…”

Learning to Detect Collisions for Continuum Manipulators Without a Prior Model

“…FBG sensors have been used for shape, force, and torsion sensing in applications with CMs, biopsy needles, catheters, and other flexible medical instruments [7,8,9,12,13,14,19]. To this end, we implement our proposed method on a CM previously developed for MIS applications, equipped with FBG sensors for shape estimation [15,16,17]. Using the proposed method, the FBG sensor will serve as a dual-purpose simultaneous shape sensor and collision detector, preserving CM small size from additional sensors.…”