Page 264 - Handbook of Biomechatronics

258 Georgios A. Bertos and Evangelos G. Papadopoulos

Fig. 10 The C-Leg 4 from Otto-Bock, a microprocessor-controlled knee joint, provides
real-time swing phase control and stumble recovery support. (From http://www.
ottobock.com. © by Otto Bock.)

and moment exerted on the prosthesis and the angular position of the knee
joint (Fig. 11). The mechanism also includes a damping device filled with a
magnetorheological fluid that can adjust rapidly to changes in external
forces. Input from the sensors and software algorithms controls the damping
qualities of the device. The fluid, which was developed by Lord Corp.
(Cary, North Carolina), (http://www.mrfluid.com), is designed to change
consistency—from a fluid to a near-solid state—in response to the strength
of a magnetic field applied to it. According to the company, the time
required to react to changing forces is 20 times faster than systems that
use passive fluids. According to the firm, such results match more closely
human neural response times than hydraulic mechanisms with motor-
controlled valve systems. The unique characteristics of Lord Rheonetic
MR fluid dampers—high controllability, millisecond response time, and
velocity-independent force—make this product possible.