A vibrotactile display design for the feedback of external prosthesis sensory information to the amputee wearer

Abstract

This thesis documents the development of a vibrotactile display to be incorporated into a powered ankle-foot prosthesis. Although existing devices have addressed the need for tactile and proprioceptive feedback in external prostheses, there has not yet been an attempt to develop and clinically evaluate a comprehensive vibrotactile display and signaling schematic for use with an active myoelectric prosthesis. The development and evaluation of two different hardware solutions are presented including an array of vibrating pancake motors embedded into the exterior of a carbon fiber prosthetic socket and an array of vibrating pancake motors embedded into a silicone socket liner. Three haptic mappings were designed based on previous work in psychophysics, haptics, and HCI. These schematics include a spatial discrimination pattern, an amplitude modulated pattern, and a gap detection pattern. To assess the effectiveness of the system, lower-limb amputees were asked to learn the three haptic mappings and use the feedback system to control a virtual ankle to a desired ankle position using a physical knob interface. Results show an overall recognition rate of 85% for all three haptic mappings and error response averages ranging from 8.2 s to 11.6 s.

(cont.) The high recognition rates and lack of variance between the mappings suggest that the three vibration parameters of spatial discrimination, amplitude modulation, and gap detection may be successfully used to represent different ankle parameters. However, the overall successful integration of the vibrotactile display ultimately depends on the interaction between the components of the whole prosthetic system.