Exploring the Tactor Configurations of Vibrotactile Feedback Systems for Use in Lower-Limb Prostheses¹

Vibrotactile feedback may be able to compensate for the loss of sensory input in lower-limb prosthesis users to improve the mobility function. Designing an effective vibrotactile feedback system requires that users are able to perceive and respond to vibrotactile stimuli correctly and in a timely manner. Our study explored four key tactor configuration variables (i.e., tactors’ prosthetic layer, vibration intensity, prosthetic pressure, and spacing between adjacent tactors) through two experiments. The vibration propagation experiment investigated the effects of tactor configurations on vibration amplitude at the prosthesis–limb interface. Results revealed a positive relationship between vibration amplitude and intensity and a weak relationship between vibration amplitude and prosthetic pressure. Highest vibration amplitudes were observed when the tactor was located on the inner socket layer. The second experiment involving a sample of ten able-bodied and three amputee subjects investigated the effects of tactor configurations on user perception measured by response time, accuracy identifying tactors’ stimulation patterns, and spatial error in locating the tactors. Results showed that placing the tactors on the inner socket layer, greater spacing between adjacent tactors, and higher vibration intensity resulted in better user perception. The above findings can be directly applied to the design of vibrotactile feedback systems to increase the user response accuracy and decrease the response time required for dynamic tasks such as gait. They can also help to inform future clinical trials informing the optimization of tactor configuration variables.