A Tactile Display System for Hand Prostheses to Discriminate Pressure and Individual Finger Localization

No current commercially available myoelectrically controlled prosthetic hands provide conscious sensory feedback to the user. A system aiming at relocation of sensory input from a prosthetic hand equipped with force sensors to the forearm skin of amputees, a tactile display, has been developed and constructed. The system consists of five piezoresistive force sensors or, alternatively, a prosthetic hand equipped with force sensors, five digital servomotors with a lever and a circular plastic disk pushing on the skin, control electronics based on an MSP430 microcontroller and a test application implemented in LabVIEW running on a PC. The tactile display system is intended to be integrated into the socket of a hand prosthesis and used as a conscious sensory feedback system for hand amputees using a myoelectrically controlled hand prosthesis. The system will provide continuous force feedback from sensors in the fingertips of each prosthetic finger and will likely improve the users' controllability and perception of the prosthetic hand. Here we report on tests made on "a five site" localization discrimination task and three pressure level discrimination tasks on the forearm of five healthy participants (non-amputees) using the LabView application to generate the stimulations. A mean five-finger discrimination accuracy of 86% and a mean three-level pressure discrimination accuracy of 93% were achieved, indicating the system to be a viable method of producing sensory feedback on the level of individual fingers.