Providing contact sensory feedback for upper limb robotic prosthesis

Lack of the sense of touch is the fundamental problem of today's robotic prostheses. Considering the fact that touch feedback plays a significant role in identifying contacted objects, our aim in this study is to use acceleration signals, occurring due to physical contact of a prosthetic hand with objects, as sensory feedback. We apply these signals on the clavicle bone using a tactor as a haptic interface. First, a library of the acceleration signals occurring as a result of tapping on different materials is collected. Effect of the impact velocity is studied and used as a scalar for real-time applications. In order to model the contact accelerations, a stochastic signal model is developed. Due to the distinct waveform characteristics of different materials, the rate of the change of acceleration (Jerk) response signals are used to identify the hardness of the objects. In a human subject study, the whole procedure of recording, identifying and replaying the signals by the tactor is studied. Results of the human subject study showed the ability of the designed tactor to provide distinguishable hardness sensations of different materials in real time.