Environment discrimination with vibration feedback to the foot, arm, and fingertip

Haptic feedback for upper-limb prostheses is desirable to enable a user to interact naturally with his or her environment, including operating the limb without vision and performing activities of daily living. We present a noninvasive method of providing one type of haptic feedback, vibration, to an upper-limb prosthesis user to enable discrimination of environment properties. Using a telemanipulation system that emulates an ideal prosthesis, able-bodied subjects tapped on materials of varying stiffness while vibration signals were recorded using an accelerometer. The vibrations were displayed in real time to the user through a C2 tactor mounted on the fingertip, foot, or upper arm. A three-alternative forced choice experiment was conducted, in which pairs of materials were presented. The subjects identified the stiffer surface or stated that they were of equal stiffness. Differing visual and force cues among the materials were eliminated through the use of the teleoperator and a graphical display. Results for five users indicate that vibration feedback to the foot enables environment discrimination comparable to that of the fingertip, and that the foot is better than the upper arm. The foot is a promising location for haptic feedback because of its sensitivity to haptic stimuli and the convenience of placing small devices and power sources within the shoe.