There are about 185,000 lower limb amputations in the United States each year. Moving lower limb prosthetics often requires greater metabolic costs and often slows amputees’ walking gaits. Current active prosthetics, which react autonomously to changing surroundings, gait cues, and more, are unable to optimize themselves to large changes in pace: For example, a motorized device optimized for stair climbing has a high transmission ratio that is unable to move fast enough to provide assistance walking.
University of Utah researchers at the Bionic Engineering Lab have developed a passively variable transmission system, enabling passive transmission ratio fluctuation. The passively variable elements of the transmission change length and/or orientation with variations in direction and magnitude of torque and force from elements of the prosthesis.