Realization of a Measuring Device for Recordning the Relative Movement between Residual Limb and Prosthetic Socket

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Virginia Tech

Relative motion between residual limb and prosthetic socket is an indication of poor fit. Both the fabrication and fitting processes are highly subjective and a favorable result depends upon the technician's expertise. Although numerous methods exist to measure the relative motion, all have limitations and are not well suited for clinical use. A measurement system using optical sensors has been proposed by students at the Technische Universität Darmstadt and evaluations of a functional model have yielded promising results. In this thesis, the existing functional model is improved and expanded to use an array of sensors. A new microcontroller is selected and incorporated into the system. The software and data communication are optimized for fast, reliable performance and the system is then evaluated on a test rig to determine favorable calibration settings and quantify performance. System frequencies up to 1299 Hz are achieved. It is found that the surface microstructure has a dominant effect over short measurement distances; calibrations performed over longer distances are to be preferred. For the chosen calibration factors, the greatest relative errors over a 40 mm distance are found to be 0.90% ± 0.51% in the X direction and -4.76% ± 1.61% in the Y-direction. A systematic drift is also identified. The final system accommodates up to eight sensors and is controlled from a feature-rich MATLAB GUI.

Pistoning, Lower Limb Prosthesis, Optical Sensor, Measuring Device