Exploring Perceptual Intensity Properties Using Electrotactile Stimulation on Fingertips

Understanding electrotactile parametric properties is a crucial milestone in achieving intuitive haptics. Perceptual intensity is a primary property, but its exploration remains challenging due to subjectivity. To address this problem, this study conducted two experiments on fingertips and proposed two metrics based on significant findings. Experiment 1 found a significant linear relationship (R$^{2}$ = 0.981) between pulse amplitude (PA) and pulse width (PW) in the logarithmic plane, and proposed a metric of parameter intensity (PI) to estimate the intensity of parameters. In Experiment 2, subjective intensity (SI) was defined and measured using a scale of 0 to 10. A metric model of SI (SI model) was derived based on the linear relationship (R$^{2}>$0.78) between PI and measured SI. A calibration method was proposed and its prediction accuracy has been verified. An average RMSE of 11.2$\%$ indicated an accuracy close to the subjective judgment error of 8.7$\%$. Results are consistent across subjects and four different electrode-skin conditions (ESC). The findings of this study provide theoretical support for SI prediction and regulation, which is significant for electrotactile feedback.