Sensitivity Analysis of Tracking Point for A Visual Tracking System on Lower Limb Joint Assessment

No matter accurate that putting a sensor in its place there is always a possibility that the position of the sensor is not correct. An inaccurate position may produce an error, which eventually affects the result of the measurement. Sensitivity analysis is intended to determine the amount of error that may occur in measurement by varying important parameters slightly in that measurement and calculating the change of the result. In this paper, sensitivity analysis was simulated in the visual tracking system for lower limb joint measurements. In doing the measurements, markers were put on the limbs of the patients at determined positions. Sensitivity analysis was then simulated by moving the points slightly. There was a total of 729 possible positions coming from three marker positions. The effects of the changes for the distances to be measured were analyzed. It is found that the errors depend on the size of the marker; for a 10-mm marker, the maximum error is only 7.85%, which is relatively small for practical application. When the marker diameter is 13 mm, the maximum error is slightly over 10%, which is still acceptable for practical purposes. There are exactly 27 positions that do not produce errors. Knowing these positions will help the user to reduce the error that may occur during the measurement.