WASHINGTON, Aug. 15 (Xinhua) -- The U.S. engineers developed a soft, portable exosuit that can give a boost to wearers' walking and running by generating an external extension torque at the hip joint.
The study published on Thursday in the journal Science showed that the lightweight exosuit, made of flexible textile components worn at the waist and thighs, could reduce the metabolic rates of walking by 9.3 percent and of running by 4 percent compared to when they were walking and running without the device.
The researchers attached to its lower back a mobile actuation system, which is controlled by an algorithm that can robustly detect the transition between walking and running.
The exosuit, weighing 5 kilograms, assists the wearer via the cable actuation system which applies a tensile force between the waist belt and thigh wraps.
People tend to choose the gait that allows them to consume the least amount of energy at a given speed. So they walk at slow speed and run at high speed.
During walking, the body's center of mass moves upward after heel-strike, then reaches maximum height at the middle of the stance phase to descend towards the end of the stance phase. In running, however, the movement of the center of mass is opposite. It descends towards a minimum height at the middle of the stance phase and then moves upward towards push-off.
Therefore, a challenge for a versatile exosuit is to assist walking and running with a single device as the two gaits have fundamentally different biomechanics.
The researchers developed a biologically inspired gait classification algorithm that can robustly and reliably detect a transition from one gait to the other by monitoring the acceleration of an individual's center of mass with sensors that are attached to the body.
Once a gait transition is detected, the exosuit can automatically adjust the timing of its actuation profile to assist the other gait, thus reducing metabolic oxygen consumption in wearers, according to the study.
"We are excited to continue to apply it to a range of applications, including assisting those with gait impairments, industry workers at risk of injury performing physically strenuous tasks, or recreational weekend warriors," said Harvard engineering professor Conor Walsh, who led the study.