Doctoral students at Arizona State University have created a ‘robotic tendon’ for a prosthetic ankle, which they hope will some day allow wounded soldiers to run like normal.
The device, nicknamed SPARKy, short for Spring Ankle with Regenerative Kinetics, will be a first-of-its-kind smart, active and energy-storing transtibial (below-the-knee) prosthesis.
Existing technology in prosthetic devices is largely passive and requires the amputee to use 20 to 30 percent more energy to propel themselves forward when walking compared to an able-bodied person, according to Thomas Sugar, ASU assistant professor of engineering at the Polytechnic campus.
Once complete, SPARKy is expected to provide functionality with enhanced ankle motion and push-off power comparable to the gait of an able-bodied individual.
“What we hope to create is a robotic tendon that actively stretches springs when the ankle rolls over the foot, thus allowing the springs to thrust or propel the artificial foot forward for the next step,” said Sugar. “Because energy is stored, a lightweight motor can be used to adjust the position of a uniquely tuned spring that provides most of the power required for gait. Thus, less energy is required from the individual.”
The team is the first to apply regenerative kinetics to design a lightweight prosthetic device. Others are using large motors combined with harmonic drives, a monopropellant or extremely high-pressure oil.
“We expect this device to revolutionize prosthetics and will be especially helpful for military personnel wounded in active duty,” says Hitt.
The first phase of SPARKy featuring the robotic tendon is expected to be ready for demonstration in December 2007. “I will know it is successful when a wounded solider is able to walk using the device on a treadmill,” said Sugar about this phase.