Haptic Feedback Improvements for Prostheses

Haptic feedback improvements for prostheses tactile sensory feedback or haptic is a fundamental element of life. While vital for interaction with the outside world, current prostheses do not have a mechanism to convey sensory information, making it difficult for users to feel connected to their environments through their prostheses, and to engage in active grasping and exploration tasks. Benefits from vibratory feedback have previously been demonstrated. This project will optimize haptic system design parameters and more thoroughly evaluate the impact of a vibratory haptic system for prosthetics. In order to accomplish this goal, the following specific objectives will be addressed: (1) building a hardware and software test bed for non-invasive voluntary control of a prosthetic hand with vibratory haptic feedback, (2) optimizing the factor application, (3) assessing the effectiveness of factor vibratory feedback on cognitive loading interpretations, and (4) assessing perceptions of subjects regarding the actual use of haptic feedback. Objective One will involve the construction of a controlled box. Fingertip sensors on the thumb and index finger of a myoelectric arm will convey pressure data to a microprocessor. Using a mapping algorithm, the processor will generate a corresponding waveform that will be sent to feedback devices (tactors) placed on the skin of the upper arm. Objectives Two through Four will involve testing the vibratory feedback on seven below elbow amputees. Objective Two will determine the best tactor location, vibration waveform and time duration until deterioration in skin sensitivity occurs by measuring how well the subjects can sense a change in vibration frequency (as identified in previous work as a spectrum of interest). This information will help determine when a resting period from vibrotactile stimulation should be required to avoid overstimulation of the skin. Objective Three will test the ability of the vibrotactile feedback to provide information on grasping force with the myoelectric hand. The myoelectric hand will be controlled by the contraction intensity of the wrist extensor and flexor muscles as detected by EMG electrodes. Trials will involve using the myoelectric hand to grasp a plush ball at forty percent, sixty percent, and eighty percent of the subject’s maximum grasping force. Trials, using vibrotactile feedback, vibrotactile feedback and visual feedback, and no feedback will be compared. Objective Four will require the subjects to rate the system in terms of level of comfort, accuracy, user friendliness, level of discomfort, and overall usefulness in grasping activities.