  This paper evaluates the capabilities of a soft robotic pneumatic actuator
derived from the terrain display haptic device, "The Smart Shoe." The bladder
design of the Smart Shoe is upgraded to include a pressure supply and greater
output flow capabilities. A bench top setup is created to rigorously test this
new type of actuator. The bandwidth and stiffness capability of this new
actuator are evaluated relative to forces and displacements encountered during
human gait. Four force vs. displacement profiles relevant to haptic terrain
display are proposed and tested using sliding-mode tracking control. It was
found that the actuator could sustain a stiffness similar to a soft-soled shoe
on concrete, as well as other terrain (sand, dirt, etc.), while the bandwidth
of 7.3 Hz fell short of the goal bandwidth of 10 Hz. Compressions of the
bladder done at 20 mm/s, which is similar to the speed of human gait, showed
promising results in tracking a desired force trajectory. The results in this
paper show this actuator is capable of displaying haptic terrain trajectories,
providing a basis for futurep wearable haptic terrain display devices.
