A Robust H∞ Full-State Observer for Under-Tendon-Driven Prosthetic Hands

Controlling different characteristics like force, speed and position is a relevant aspect in assistive robotics, because their interaction with diverse, common, everyday objects is divergent. Usual approaches to solve this issue involve the implementation of sensors; however, the unnecessary use of such devices increases the prosthetics' prices in a significant manner. Thus, this work focuses on the design of an H
_∞
full-state observer to estimate the angular position and velocity of the motor's gearhead in order to determine parameters such as the joints' torque, fingertip force and the generalized coordinates of the digits of an under-tendon-driven system to replace the transductors. This is achieved by measuring the current demanded by the brushed DC motors operating the fingers of an open-source, 3D-printed and intrinsic prosthetic hand. Besides, the proposed method guarantees disturbance attenuation, as well as the asymptotic stability of the error estimation. In addition to that, the theoretical model was validated through its implementation on a prosthetic finger, showing successful results.