Study On The Kinematic Synergy Of The Human Lower Limb And Synergy-based Design Of Exoskeleton With Anthropomorphic Locomotion

The excellent lower limb motor ability of humans provides an important guarantee for their healthy life and work.Exploring the mystery of human locomotion and then repairing or enhancing the lower limb motor ability with engineering science methods have become the research hotspot in the field of wearable lower limb exoskeleton robotics.Focusing on the challenging issue of how to design a lower limb exoskeleton with the motor ability to match the human natural locomotion and the capacity to assist human mobility,this dissertation carries out a systematic and in-depth study on the exploration of the movement mechanism of the lower limb and the mechanical reproduction of the lower limb natural movements.The main innovative researches of the dissertation are as follows:To uncover the unclear generation mechanism of the lower limb natural movements,we investigate and reveal the kinematic synergy underlying the lower limb natural movements.By using a motion capture system,a joint motion dataset consisting of thirtysix lower limb movement patterns is built,which takes into account five common lower limb movement patterns(i.e.,walking,running,hopping,turning,and sitting-downstanding-up)and five environment constraints(i.e.,level ground,cross slopes,longitudinal slopes,obstacles,and stairs).By the feature extraction and feature analysis of the motion data of each pattern,it can be found that there exist synergistic movement relationships among the lower limb joints,and the six joint motions of one lower limb can be decomposed into six basic motor modules(called motor primitives)in each pattern.Furthermore,it can be found that the linear combination of a small number of motor primitives(one to three)can effectively reconstruct the lower limb joint motions in each pattern(reconstruction accuracy > 90%).To address the problem of whether the motor primitives are similar among the movement patterns,a comprehensive similarity index of the motor primitives is proposed to measure the similarities and differences among the movement patterns.Based on the similarity measurements,the natural grouping structure of the movement patterns is explored using the cluster analysis method.The result reveals the movement patterns that adopt similar motor primitives and five different movement pattern groups.By comparison,the similarities and differences in the synergistic movement features are further found among the different movement pattern groups.Altogether,the findings suggest that humans can simplify the motor control by adopting similar synergistic movement strategies in various movement patterns.As suggested by the similarities of the synergistic movement features within and among the above movement pattern groups,there may be some common synergistic movement features underlying all the movement patterns.To address this problem and break through the limitation of local observation in single or partial movement patterns,a new approach for analyzing the lower limb movements from a holistic viewpoint is proposed.A method for extracting the common synergistic movement features of all the movement patterns is presented,and it can be found that three common motor primitives can reconstruct the lower limb joint motions during walking,running,hopping,and sittingdown-standing-up(reconstruction accuracy > 90%).The related findings provide a theoretical basis for the design of a multifunctional and versatile lower limb exoskeleton.Based on the above findings about the kinematic synergy of the lower limb,a design method for a lower limb exoskeleton with anthropomorphic movements is presented.According to the movement analysis results and combining with the cluster analysis of joint motion correlations,an extraction method of the motor primitives with the grouped coupling of the lower limb joints is proposed.Based on this,the method of the decomposition and synthesis of the motor primitives is studied.The mechanical reproduction principle of the motor primitives is proposed,and the mechanism design method of the exoskeleton with the ability to generate anthropomorphic movements is then built.Based on the equivalent movement transformation of the motor primitives,a design method of the movement reproduction mechanism that ensures the compactness and lightweight of the exoskeleton is proposed.The tests on an exoskeleton prototype verify the effectiveness of the proposed exoskeleton design method.