FBG Force Sensor for Tendon-Actuated Medical Robots
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Solution Overview
Problem
Existing force sensors for tendon-actuated medical robots face challenges such as design complexity, electromagnetic interference, and compatibility issues with biological environments, particularly for endoscopic robots, due to the need for electrical wiring and force decoupling, which complicates accurate real-time force measurement.
Innovation Solution
A compact force sensor using a Fibre Bragg Grating (FBG) fibre attached to a Nitinol or nickel-titanium tube body, which is attached to a tendon-actuated mechanism, allowing for strain measurement through wavelength shift, eliminating the need for force decoupling and enabling MRI compatibility and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrical sensors (piezoelectric sensor, MEMS, strain gauge sensors, thin film) are used for force measurement, then force measurement capability is achieved, but design complexity increases due to requiring force decoupling and electrical wiring
Solution Approach 1:
The patent replaces electrical sensors with an optical sensing system based on Fibre Bragg Grating (FBG) technology. The FBG fibre is attached to the tendon-sheath mechanism, and force is measured by detecting wavelength shifts in the optical fibre caused by mechanical strain, eliminating the need for electrical wiring and complex force decoupling algorithms
Solution Approach 2:
The patent introduces an optical fibre as an intermediary element that mechanically couples to the tendon-sheath structure. The FBG segment of the optical fibre acts as a mediator that transduces mechanical strain into optical wavelength shifts, providing a direct measurement path without requiring electrical components or complex signal processing
2Measurement precision
If electrical sensors are mounted on surgical instruments, then real-time force measurement is achieved, but electromagnetic interference and noise affect measurement accuracy
Solution Approach 1:
The patent substitutes electrical sensing components with an all-optical sensing system. The FBG-based optical sensor is immune to electromagnetic interference because it uses light wavelength shifts rather than electrical signals, eliminating the harmful electromagnetic effects while maintaining real-time measurement capability
3Measurement precision
If electrical wiring and sensors are exposed to biological tissue or working environment, then force measurement is achieved, but risk of damage increases
Solution Approach 1:
The patent replaces vulnerable electrical sensors and wiring with an optical fibre-based sensing system. The optical fibre and FBG segments are inherently more robust in biological environments, resistant to corrosion and degradation from exposure to bodily fluids and sterilization processes, thereby reducing the risk of damage while maintaining measurement functionality
4Volume of moving object
If compact sensor design is implemented for endoscopic use, then miniaturization is achieved, but sensor size and integration complexity increase
Solution Approach 1:
The patent employs a nested structure where the FBG fibre is integrated within or attached to the tendon-sheath mechanism itself. The optical fibre runs through the sheath structure, and the FBG segment is positioned at a specific location along the fibre, allowing the sensor to be miniaturized and integrated without adding significant bulk or complexity to the overall endoscopic device
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides accurate, real-time force measurement with high sensitivity and resolution, is biocompatible, and compatible with MRI, reducing design complexity and noise, while allowing for compact integration and easy fabrication.
Implementation Method 1
a sensor provided on the body to obtain a compression force on the body from the part of the tendon-actuated mechanism through which the tendon passes
Implementation Method 2
shift in wavelength of light transmitted by the first FBG segment is directly correlatable to the compression force on the body
Data Source
AI summary
A force sensor for a tendon-actuated mechanism, the force sensor comprising: a body having a through hole for passage of a tendon of the tendon-actuated mechanism therethrough, the body configured to be connected to a part of the tendon-actuated mechanism through which the tendon passes; and a sensor provided on the body to obtain a compression force on the body from the part of the tendon-actuated mechanism through which the tendon passes.