Vibrational stimulation on the skin to provide feedback about the grasping force or hand opening of forearm prostheses during daily life grasping tasks.

Sensory feedback about grasping force and hand opening of a myoelectric forearm prosthesis is very important in optimal object handling, but lacking in current commercial prostheses. We have developed and evaluated methods to provide hand opening and grasping force feedback via vibrotactile stimulation to the skin. However, virtual environments were used in the previous studies. Therefore, in this study the concepts for vibrotactile hand opening and grasping force feedback will be evaluated in daily life grasping tasks. Three kinds of grasping taks will be performed: 1) daily life grasping tasks within the standardized SHAP protocol, 2) grasping of delicate daily life objects and 3) grasping of abstract objects with varying weights, sizes and stiffness.

Grasping performance of daily life grasping tasks will be improved when vibrotactile feedback about the hand opening and grasping force is provided compared to situations without vibrotactile and visual feedback.

All measurements will be performed on 1 day. For the patient measurements, a user specific prosthesis socket will be made at least one week before the experiments.

All subjects will be asked to perform grasping tasks (1-within a standardized protcol using the SHAP test, 2-grasping of delicate daily life objects, 3-grasping of abstract objects varying in weight, size and stiffness). All tasks are being performed with a commercial myoelectric forearm prosthesis, controlled by muscle activity (EMG) from the forearm (stump). During these tasks, vibrotactile feedback about the grasping force and the hand opening of the prosthesis is provided through a single vibrating element (C2 tactor) and an array of 8 coin motors respectively.