INNOVATIVE DESIGN, DEVELOPMENT AND PROTOTYPING OF KNEE PROSTHESIS

摘要

This paper deals with innovative solutions in semi-passive electronic controlled above knee prosthesis. The project is developed at Robotics Laboratory, Mechanical Dept. of Politecnico di Milano, with the co-operation of INAIL National Prosthesis Centre. In particular, new issues deal with mechanical, electronic and IT solutions, in order to get larger efficiency, stability, safety and easy production, innovative step control for real-time acquisition of de-ambulation information and full prosthesis-patient adaptation. Lot of care was taken about analysis in manufacturing of most advanced prosthesis available in market. From this, different solutions were found out in opposition to actual production in order to overcome many limitations. Main limits are very expensive purchase of high performance devices and high maintenance costs. Bio-robotic prosthesis prototype, getting now its final development stage, is able to set continuously and dynamically its motion parameters in order to assure the largest safety and functionality to user. Mechanical design chosen has easiness as distinctive feature as well as high performances. Innovative solutions deal with motion control: in particular flexoextension of knee prosthesis is regulated by electromechanical actuation system based on several input signals coming from sensors. Thus, device behaviour gains high adaptation towards various deambulation condition. The device has been created equipped with energy accumulation. This feature makes amputated patient able to do complex movements as far as similar to natural ones. A special constant force spring provides storage and return of potential energy in order to let prosthesis straighten during swing stroke. A small shoe brake let step regulation acting on elastic element. Brake system fills up a very limited room and get high torque-size ratio. The whole mechanical structure has been optimized by FEM analysis, achieving weight reduction and functional improvement. The device can fit patient step working in different ways according to signal acquisition by sensors system. In particular input signals are flexion and compression, rate and acceleration. Input signals are received and elaborated by small STMicroelectronics chip in order to quickly supply output signal to brake acting system. All electronics and acquisition system are very compact and miniaturized.