Stair-ascent strategies and performance evaluation for a lower limb exoskeleton

Power lower limb exoskeleton has gained considerable interests since it is widely applied in both walking assistance and rehabilitation related applications. The most challenge problem of these kinds lower exoskeletons is how to deal with the complex environment, such as stairs in daily life. Based on a developed lower limb exoskeleton named AssItive DEvice for paRalyzed patients ( AIDER ), this paper proposed a novel stair parameters perception approach named Stick From the Origin (SFO) and a bio-spired stair gait trajectory generator based on Dynamic Movement Primitives (DMPs) and summarized the joint torque and power requirements. With two distance sensors, the low-cost and real-time stair parameters perception approach could be tested and verified in practice with acceptable accuracy. During the process, the Center of Pressure (CoP) of the whole system would be concerned to keep the pilot’s safety. With the reference stair gait and stair parameters brought in, a natural and flexible stair-ascent gait can be generated by the bio-spired stair gait trajectory generator based on DMPs, which was validated in practical application on the AIDER system with and without pilot. Based on the averaged torques and power across these trials, the peak body-mass-normalized knee and hip joint power, knee and hip torque during the stair-ascent movement are 1.82 W/kg and 1.52 W/kg, 1.36 Nm/kg and 1.22 Nm/kg, which are required during the process of lifting the leg onto the stair tread.