Engineers at the University of Texas at Dallas have developed a new robotic prosthetic leg based around a "space station" motor, offering improved force while drawing less battery power than existing designs.
"Our prosthetic leg consumes approximately half the battery power of state-of-art robotic legs," says project lead Professor Robert Gregg, who led the study at the University of Texas at Dallas before moving to the University of Michigan, "yet can produce more force."
The secret lies in a novel compact yet powerful motor, originally designed to drive a robot arm installed on the International Space Station (ISS). Fitted in a robotic prosthesis, the motors power the knee and ankle while allowing the knee to swing freely in motion — and use regenerative braking in order to boost battery life.
Where rival designs use small motors and a series of gears to provide enough torque, the new motors are powerful enough to work with far fewer gears — reducing the complexity of the design, the noise level in use, and absorbing shocks when the foot hits the ground.
"In some cases, [study participants] have observed that they feel like muscles in their hips and back are working less with our leg, compared to their conventional leg," says Gregg. "We're able to reduce compensations at the hips."
"We designed our joints to be as compliant, or flexible, as possible," adds first author Dr. Toby Elery. "Our robotic leg can perform and even react like a human joint would, enabling a naturally free-swinging knee and shock absorption when contacting the ground."
The team's work has been published under closed-access terms in the journal IEEE Transactions on Robotics; the Universities of Texas at Dallas and Michigan have indicated they are jointly pursuing patent protection and commercialisation, while working to develop control algorithms which allow the leg to automatically adjust gait, pace, and accommodate different terrains.