Static accuracy of resistive bend sensors

Sensing of finger joint rotation can be difficult due to the hand's many degrees-of-freedom within a small space. Resistive bend sensors offer a potentially attractive option for making these measurements due to their low profile, small mass, and low cost. Further characterization of these bend sensors is needed, however, to ensure that readings are accurate. Specifically the static accuracy when bending and straightening the sensor has not been investigated. In this study, two-inch resistive sensors were bent from 0° to 90° and back to 0° while measuring the voltage output. Five calibration models were fitted to the measured data and used to determine the sensor's accuracy. When used with coated sensors, both the cubic and pchip models demonstrated non-monotonic behavior at low bend angles. Using uncoated sensors, the pchip calibration function and raw data resulted in a median error of 1.7° (SD 1.7°, range 12.1°).