Temporal Resolvability of Stimulus

Abstract

If the time spacing between two consecutive, perceptually significant kinesthetic force stimuli is less than the minimum time spacing (temporal resolution $T_r$) required in perceiving the jump discontinuity, then the second force stimulus will not be perceived even if it is well above the just noticeable difference. Hence, there is no need to transmit the second force sample to the operator. Thus, for haptic transmission in a teleoperation, the temporal resolution $T_r$ needs also to be considered while effecting perceptually adaptive sampling. In this chapter, we estimate the temporal resolution $T_r$ for the kinesthetic stimulus. For that purpose, we define an experimental setup where a user is subjected to a specific type of kinesthetic force stimulus. The force stimulus has two perceptually significant consecutive jumps separated by a variable time spacing. The user is asked to respond whenever she can perceive the discontinuity between the jumps by pressing a button of the stylus. If for a particular time spacing, the jump discontinuity is perceived, the user response is labeled as 1, and −1 otherwise. In this way, we record the labeled haptic responses for several users. In order to estimate the temporal resolution $T_r$, we use a classical psychometric approach. It is observed that $T_r$ lies between 17 and 37 ms for different users. Further, we also study how the physical fatigue (possibly including the effect of boredom) of muscles affects the temporal resolvability of a human operator in perceiving the jump discontinuity. It is observed that the resolvability in perceiving the jump discontinuity decreases by about $30\%$ due to the fatigue. Hence, the fatigue does affect the temporal resolvability significantly. In order to alleviate this problem during teleoperation, it is recommended that the robot should be slowed down accordingly if a task is to be carried out over a longer period.