Evaluation of the FSA Hand Force Measurement System

Abstract

The FSA (Force Sensitive Application) system measures hand force by using force resistance sensors. Compared to conventional hand force measurement systems such as Lafayette hand dynamometer and Jamar hydraulic hand dynamometer, the FSA system can be applied to analyze use of hand forces while the hand is manipulating objects for a task, However, the measurement performance of the FSA system has not been objectively evaluated. The present study tested the FSA system in terms of stability, repeatability, accuracy, and linearity at sensor (one sensor) and system (hand motions; power grip, pulp pinch, pulp press) level. In sensor level, the FSR sensor has good stability (CV ≤ 2%) and linearity (R ²=0.82), but has low repeatability (CV=11%~19%) and accuracy (22% of under evaluation on average). In system level, accuracy is dramatically worsened by increasing the number of sensors involved. For example, mean differences (MD) between the FSA and NK dynamometer are −0.09kgf, −1.15kgf, and −1.49kgf for pulp press (1 sensor), pulp pinch (2 sensors), and power grip (18 sensors). However, there is strong linear relationship between values from the FSA and NK dynamometer (R ²=0.82, 0.94, and 0.99 for pulp press, pulp pinch, and power grip). This performance result indicates that measurements from the FSA system should be used for relative comparison rather than for absolute comparison.