Research On Gait Strategies And Gait Planning Of Exoskeleton For Hemiplegia Patients

In recent years,the hemiplegic patients caused by stroke have increased significantly.These patients have walking disorder and lose life self-care ability.Hemiplegic exoskeleton is used to help the patients achieve self-help walking and functional rehabilitation.The exoskeleton is a multi-interdisciplinary system intersected by robotics,bionics,automation,signal processing,etc.and depended on the multi-domain technologies including mechanics,sensing and control.This dissertation comes from Public Projects of Zhejiang Province ‘The Development of Walking-assist Lower Limb Exoskeleton for hemiplegic patients'.The status and development of exoskeleton in domestic and international scope are introduced in the dissertation.In order to solve the structure redundancy of normal exoskeleton for hemiplegic patients,a novel lower limb exoskeleton with stability supporting bionic structure is proposed.The structure and gait strategies of hemiplegic Lower Limb Exoskeleton have been designed and optimized.These research results provide the new scheme and methods for the mechanical design and performance optimization of hemiplegic exoskeleton and have a good engineering directive to the application of hemiplegic Lower Limb Exoskeleton.The main research and achievements of the dissertation are as follows:1)Bionics structure of hemiplegic lower limb exoskeletonBased on human joint model and hemiplegic gait characteristic,a design scheme of bionics structure and hemiplegic Lower Limb Exoskeleton is proposed.The design principles of wearing comfort,movement safety and interface operation convenience are investigated.2)Gait strategy of hemiplegic lower limb exoskeletonBased on the proposed above structure of hemiplegic Lower Limb Exoskeleton,several feasible gait strategies on flat ground and up/down stairs are proposed.A comprehensive gait performance evaluation index model is built,which provides a new method and objective criterion for the gait strategy study.A 3D integrated model including human and exoskeleton is built and used to carry out the gait simulation.3)Trajectory planning of hemiplegic lower limb exoskeletonThe hemiplegic Lower Limb Exoskeleton and patient are simplified as the connecting-rod model.According to this model,the motion equations of leg key-points gait trajectory on flat ground and up/down stairs are derived.Cubic spline theory is used to obtain the fitting trajectory curves of key-points.This study provides the smooth trajectories of exoskeleton corresponding to different gaits.4)Modeling and analysis of kinematics and kinetics for hemiplegic exoskeletonThe kinematics models of hemiplegic lower limb exoskeleton are deduced based on the D-H method,and then inverse kinematics in sequence stage of the exoskeleton is analyzed by the geometric constraint method.In order to simplify the model,the coordinate transformation method is used to reduce the number of connecting-rods from 4 to 3.At the same time,the kinetics model is deduced according to Lagrange method.Finally,A geometric Jacobian matrix of the exoskeleton is deduced to build the relationship between the joint velocity and terminal velocity.The study provides the theoretical basis for the design and optimization of hemiplegic exoskeleton.5)Gait regression model of hemiplegic lower limb exoskeletonIn order to increase the intelligent level of exoskeleton,A machine learning algorithm of gait trajectory is studied.A new gait characteristic parameter organization structure of hemiplegic lower limb exoskeleton is propounded to reduce the combinations number of training samples.We establish the gait trajectory regression fuzzy model for hemiplegics lower limb exoskeleton,using support vector machine to identify the model parameters.A new fuzzy kernel function is constructed for SVM.Based on the model,the gait trajectory can be automatically generated according to few Gait characteristic parameter,avoiding the unexpected dangers in the teaching programming.A algorithm of feature weighting and timing window have been applied synthetically to the fuzzy kernel function to improve the accuracy of the model effectively.6)Prototype manufacture and experimental studyBased on proposed bionic structure and related study,a physical prototype of hemiplegic lower limb exoskeleton is produced and an experimental platform is established.By the experimental study,the validity of above model and its simulation is verified.The experimental platform provides some conditions for optimization and study of the exoskeleton.