| With the rapid development of society and the gradual improvement of people’s healthy living standards,the number of lower limb motor dysfunction caused by the aging of today’s population and various accidental injuries continues to rise,seriously affecting the daily life and work of patients.At present,the limitations of manual or traditional lower limb rehabilitation equipment have led to the increasing development and use of lower limb rehabilitation robots.At the same time,along with the continuous breakthroughs in science and technology,the types and functions of lower extremity rehabilitation robots have become more diversified,providing superior and comprehensive rehabilitation training for patients compared to traditional rehabilitation equipment and easing the heavy training tasks of rehabilitation instructors.Lower limb exoskeleton rehabilitation robots not only help people with lower limb movement disorders and old and frail people with mobility problems to achieve normal walking and improve their quality of life,but also play a positive role in promoting the development of China’s rehabilitation medical security system.Nowadays,intelligent lower limb exoskeleton rehabilitation robots have become a hot research topic in the field of rehabilitation instead of traditional rehabilitation equipment.However,the existing lower limb exoskeleton rehabilitation robots still have many problems that need to be improved,such as bulky exoskeleton rehabilitation equipment,fixed and single rehabilitation training mode,lack of human bionic characteristics of joint exoskeleton structure and uncoordinated movement of human-machine gait rehabilitation training.The above problems not only affect the rehabilitation efficiency of patients,but even worse,cause secondary injuries to patients.Therefore,this paper addresses the common problems in the current research of lower limb exoskeleton rehabilitation robots,and starts the research from the aspects of structural design,dynamic stability and gait planning of lower limb exoskeleton rehabilitation robots,and the main research contents of the paper are as follows.(1)Based on the physiological structure of human lower limbs and the mechanism of human gait movement,the main components of hip,knee and ankle joints of human lower limbs and their range of motion are analyzed and studied for the rehabilitation training of patients with lower limb movement disorders.Based on the combination of 3D motion capture system and CGA(Clinical Gait Analysis)gait data,we determine the degrees of freedom and active and passive joint structure of the lower limb exoskeleton rehabilitation robot.An anthropomorphic multi-degree-of-freedom lower limb exoskeleton structure design method is proposed,and the active hip,knee and passive ankle joints are studied in detail to complete the overall design of the lower limb exoskeleton rehabilitation robot.(2)Based on the anthropomorphic configuration design,an anthropomorphic hip lumbar exoskeleton structure is proposed.The exoskeleton structure is designed in the form of active and passive degrees of freedom,and the human gait training is realized by servo motor actively driving the hip flexion/extension degrees of freedom.In order to make the patients comfortable and safe for rehabilitation training,the internal/external rotation degrees of the hip joint and the lumbar rotation axis are coordinated to achieve the "anthropomorphic" design of the exoskeleton,which improves the flexibility of the internal and external rotation axis of the hip joint and enhances the fit between the movement of the exoskeleton structure and that of the human hip joint and lumbar movement.Based on the multi-axis motion characteristics of the crossed quadruple link mechanism similar to the human knee joint structure,a bionic artificial knee exoskeleton structure based on the crossed quadruple link mechanism is proposed.The crossed four-link mechanism is used to simulate the transient rotation center motion of the cruciate ligament inside the human knee joint,the servo motor driven telescopic rod to simulate the human thigh muscle to drive the knee exoskeleton motion,and the auxiliary limit locking structure to simulate the knee patella to prevent the knee exoskeleton from over-extension motion.On this basis,the ankle exoskeleton structure adopts the connection method of passive dorsiflexion/stance flexion degrees of freedom and inversion/extrusion degrees of freedom in tandem,designs the ankle exoskeleton structure degrees of freedom coaxially with the human ankle joint motion degrees of freedom,and assembles elastic elements with similar motion characteristics to the human hamstrings to improve the cushioning force when the exoskeleton falls to the ground.(3)To address the structural applicability of the lower limb exoskeleton rehabilitation robot,the kinematic model of the lower limb exoskeleton rehabilitation robot is established based on the D-H kinematic method for the three-dimensional base plane in standing and the sagittal plane in walking,and the chi-square transformation matrix of the swing leg end coordinate system is analyzed and calculated.Secondly,the kinetic model of the lower limb exoskeleton rehabilitation robot is established by using Lagrangian kinetic equations,and three different phases of exoskeleton kinetic models are established according to the phases of human gait cycle motion: single-leg support phase,double-leg support phase and doubleleg support one-leg redundant phase.Finally,the correctness of the kinetic model and the rationality of the structural design of the lower limb exoskeleton rehabilitation robot were verified by simulation analysis.(4)In this paper,we analyze the principle of traditional ZMP stability criterion and its limitations at the end of single-leg support phase,and propose a ZMP stability-based singleleg support swing projection polygon stability criterion method.The gait planning based on geometric constraint calculation analyzes and solves the gait characteristic parameters and motion trajectory of the rehabilitation robot,and optimizes the gait characteristic parameters of the rehabilitation robot by whale optimization algorithm to improve the stability and smoothness of the gait motion trajectory of the lower limb exoskeleton rehabilitation robot.To address the problems that the above gait planning methods are not fully intuitive and the gait planning is discontinuous,a cyclic gait planning method based on LSTM neural network is proposed for the lower limb exoskeleton rehabilitation robot,and the feasibility and correctness of the cyclic gait planning are verified by combining the human gait cycle motion characteristics.(5)Aiming at the problems of non-linearity of patient’s lower limb muscle group perturbation and gait suppleness of exoskeleton walking in gait reference trajectory tracking control of lower limb exoskeleton rehabilitation robot,this paper proposes iterative learning control method of RBF neural network and sliding mode control method to achieve high precision tracking of desired gait trajectory of rehabilitation robot,so that the output torque of each joint of lower limb exoskeleton rehabilitation robot tracks the input desired torque to achieve The purpose of rehabilitation training.The Lyapunov method is applied to demonstrate the global asymptotic stability of the closed-loop exoskeleton system.To further improve the safety of patients and the effectiveness of rehabilitation training,the 3D motion capture system is combined with sensor signals to establish a skeletal muscle model of the lower limb applicable to patients with leg spasticity stage,and to plan a gait training trajectory suitable for patients to ensure the efficiency and safety of rehabilitation training.Meanwhile,the knee and ankle joint training experiment,passive rehabilitation training experiment and active rehabilitation training experiment were conducted for the main performance of the lower limb exoskeleton rehabilitation robot to comprehensively evaluate the overall performance index of the lower limb exoskeleton rehabilitation robot. |
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