Evaluation of an Experimental Procedure to Calibrate In Situ an Instrumented Glove for Measuring Biomechanical Overloads

The contact force measurement is a crucial step for the biomechanical overloads evaluation. OCRA index is one of the most widespread for this analysis, but the force measurement is actually based on subjective scales. The aims of this study are: (i) the design of an instrumented glove characterized by 5 piezoresistive sensors, and (ii) the evaluation of an experimental procedure for the in-situ calibration to optimize the force measurement accuracy. Output data from the instrumented glove worn by ten subjects were gathered using a load cell as. For the calibration procedure, subjects were asked to wear the glove and manually impose a gradual force up to 40 N. The calibration procedure was performed in three sessions, and each session consists of five repetitions per each sensor. This approach allowed the assessment of the repeatability and reproducibility of the calibration procedure due to the consecutive use of the glove and its re-worn. The calibration parameters were determined using both linear and exponential regression models. Results indicated that the exponential regression method provided greater accuracy, with an interpolation uncertainty consistently below 1% of the full scale (FS), compared to over 5% FS with linear regression. To highlight the best calibration procedure, the root mean square error (RMSE) was computed in several conditions. The best results have been gathered when the glove is calibrated using multiple calibrations performed by the same subject without the glove removal, with an accuracy in average of 10% FS. These findings suggest the necessity to create a portable set-up for the in-situ glove calibration that must be repeated each time the subject wear the glove.