Knee Joint Motion Detection Based on Demodulation of Overlapping Spectrum Using Fiber Bragg Grating Sensor

Area of Science:

• Biomedical Engineering
• Optical Sensing Technologies
• Biomechanics

Background:

• Accurate knee joint motion analysis is crucial for diagnosing and treating musculoskeletal disorders.
• Existing methods for motion detection often involve complex setups or limited real-time feedback.
• Fiber Bragg Grating (FBG) sensors offer potential for non-invasive, high-resolution strain measurement.

Purpose of the Study:

• To develop and validate a novel knee joint motion detection method using FBG technology.
• To simplify the demodulation process from complex spectral analysis to optical power measurement.
• To assess the repeatability and practical potential of the proposed system for real-time monitoring.

Main Methods:

• A flexible FBG sensor, encapsulated in polydimethylsiloxane (PDMS), was attached to the knee joint surface.
• Joint motion induced axial strain in the FBG, causing a shift in its central reflection wavelength.
• Overlapping spectrum demodulation was employed, relating FBG wavelength shift to changes in optical power measured by a power meter.

Main Results:

• The study established a theoretical and experimental relationship between optical power and FBG wavelength shift due to joint motion.
• Real-time demodulation of knee joint motion was successfully achieved.
• Experimental results demonstrated good repeatability in monitoring knee joint movements.

Conclusions:

• The proposed FBG-based overlapping spectrum demodulation method offers an intuitive and effective approach for knee joint motion detection.
• The system simplifies spectral analysis into optical power measurement, enhancing practicality.
• The technology shows promise for real-time biomechanical analysis and clinical applications, warranting further investigation into its limitations.