H. M. Herr, A. Wilkenfeld, and J. Blaya. Patient-adaptive prosthetic and orthotic leg systems, Proceedings of the 12th Nordic Baltic Conference on Biomedical Engineering and Medical Physics, Reykjavik, Iceland, pp. 123-128, Jun. 2002.

Abstract

Two computer-controlled devices for leg rehabilitation are presented: 1) an external knee prosthesis for trans-femoral amputees; and 2) a force-controllable ankle-foot orthosis to assist individuals suffering from drop-foot, a gait pathology resulting from muscle weakness in ankle dorsiflexors. Here muscle-like actuators and biologically-inspired control schemes are employed to enhance patient stability, speed and dynamic cosmesis. Patient-adaptive control schemes are discussed in which the joint impedance of each device is automatically modulated to match patientspecific gait requirements. By measuring the total time that the prosthetic foot remains in contact with the ground during each gait cycle, the prosthetic knee controller estimates forward speed and modulates swing phase flexion and extension damping profiles to achieve biological lower-limb dynamics. For the ankle-foot orthosis, joint stiffness is automatically adapted to permit a smooth and biological heel strike to forefoot walking transition in drop-foot patients. Using only local sensing and computation, the adaptation schemes presented here automatically modulate joint impedance throughout the stance and swing phase of walking, enabling patients to walk in a safe, comfortable and smooth manner.