Biomechanical analysis and preliminary transtibial prosthesis design for pedal harpists

Abstract

The concert harp is a string instrument played using both the hands and the feet. Harpists pluck the strings with their fingers while operating seven foot-pedals that change the pitch of the string notes. For this reason, the instrument is inaccessible to individuals with lower limb amputations. This work investigates the biomechanics of harp playing and proposes a new dedicated transtibial prosthesis design. A custom pedal jig was built, replicating the pedal box of the harp, and used in motion and force capture trials conducted using a Vicon system and Plug-in-Gait model. Analysis revealed rapid pedal transitions and foot motion that are distinct from and more demanding than everyday activities such as walking or running, and that cannot be performed by current commercial prostheses. A preliminary design has been developed based on these analyses, and evaluated using CAD simulations in Autodesk Inventor, confirming that the required range of motion can be achieved. Actuator selection was based on calculated forces derived from the biomechanical data. The preliminary design meets the key functional requirements.