Admittance measurements of the foot during ´maintain position´ and ´relax´ tasks on a gas pedal

The goal of this study is to determine the effect of ´maintain position´ and ´relax´ tasks on the dynamic of the foot while manipulating a gas pedal The foot is viewed as a mass-spring-damper system, of which the viscoelasticity can be altered by reflexive feedback and muscle (co-)contraction. The dynamic properties of the foot are described by the mechanical admittance, which determines the foot position as a dynamic function of an external force perturbation. It is hypothesized that humans would change their admittance based on task perception. Experiments were done to estimate the endpoint foot admittance with frequency response functions (FRFs). An experimental setup that can simulate a gas pedal with different static and dynamic properties was used to apply continuous force perturbations to the foot. Eight subjects were instructed to either minimize the resulting pedal deviations (´maintain position´) or do nothing and just rest their foot on the pedal (´relax´). The force perturbation, pedal position, and reaction force were measured, and transformed to the frequency domain to estimate the closed-loop admittance. All subjects showed a considerable difference between the two tasks, confirming the hypothesis that drivers change the dynamics of their foot to best accomplish a perceived task.