Study of Lower Limb Exoskeleton Stair Movement Based on Multicoupled Continuous Dynamic Primitive Gait Learning Strategy

Stair walking, as the most common gait pattern in daily life, also has a positive effect on the recovery of limb function in patients with lower limb disabilities. To realize steady walk on stairs, the most important problem is the structure design and gait planning of lower limb exoskeleton. A novel assisted exoskeleton system was proposed based on biomechanics characteristics. The four-point segmented gait generation strategy based on cubic spline interpolation was proposed, and the gait trajectory during stair walking was described. To ensure walking stability, the constraint relationship between the swing leg and the stair step was constructed. In addition, the constraint function was constructed for stable walking in horizontal and vertical directions based on zero moment point (ZMP). Then, the multicoupled continuous dynamic primitive gait learning strategy (PIRDMPs) was proposed to achieve fine-grained learning of stair gait trajectories. Finally, the proposed method was validated by human-machine wear experiments. Compared with the dynamic motion primitive (DMP) method, the average trajectory fits for the hip and knee joints obtained based on the PIRDMPs method were increased by 11.28% and 7.17%, respectively. Also, the average deviation values of ZMP in the sagittal plane (ZMP-X) and coronal plane (ZMP-Y) of the man-machine system were reduced by 109.2 and 125.3 mm, respectively.