Design and Preliminary Testing of a Lightweight and Low-Cost Knee Exoskeleton For Human Gait Assistance

Pediatric exoskeletons have the potential to aid the walking of children with neuromuscular conditions such as crouch gait. However, current exoskeleton devices often rely on bulky batteries and motors. Recent developments in 3D-printing technologies now allow the construction of lightweight yet stiff parts that are easy to customize and use for pediatric applications. We present the mechanical design of a 3D-printed and spring-powered knee exoskeleton for gait assistance. The device had a mass of ∼1.25 kg per leg and provided a knee extensor moment during the stance phase of gait, simulating the spring-like behavior of the knee. Conversely, the exoskeleton provided no resistance during swing to allow free motion of the joint. To validate the device, we recruited two neurologically intact children to walk on a treadmill with and without the exoskeleton while we recorded kinematics, kinetics, and muscle activity data. Our exoskeleton generated knee extensor moments proportional to its angular excursion and had a peak mean moment of ∼0.1 N·m/kg during stance. Kinetic data showed that subjects decreased their biological knee moment and joint spring-like behavior to compensate for the added exoskeleton moment and stiffness, respectively. We ultimately show that the device is robust and capable of generating extensor moments comparable to devices used to assist the knee in children with crouch gait.