Structure And Design Simulation Analysis Of Hip-knee Posture Synergy Exoskeleton

With an ageing population and a low birth rate,there is an increasing demand for lower limb exoskeleton robots that can assist,enhance or restore mobility to the human body.As an interdisciplinary and complex product,the mechanical structure of a lower limb exoskeleton robot is a key focus of research,as it acts as an actuator for the control of the exoskeleton robot and as a bridge to the human body,and the design of the mechanism has a significant impact on the performance of the exoskeleton.The movement of the human lower limb can be regarded as a rhythmic movement,and the temporal and spatial characteristics of the hip,knee and ankle flexion and extension postures during walking have certain stability,repeatability and synergy.To address this characteristic,this paper proposes a mechanical reproduction method around the spatial synergistic feature reproduction of human lower limb movements,and designs an underdriven exoskeleton robot,which reduces the use of exoskeleton robot actuators and provides theoretical and basic experimental support for subsequent research on enhancing human loading capacity and mobility.The main research elements of this paper are as follows:1.Research on the human lower limb posture synergy relationship is conducted.We designed human joint angle data acquisition experiments,created joint motion data sets,used mathematical dimensionality reduction methods to extract human lower limb posture synergy features,established the mechanical reproduction principle of human lower limb posture synergy,and provided a theoretical basis for the underdriven exoskeleton using wire rope pulley as the drive.To address the joint misalignment problem during human-machine knee motion,a five-link knee joint is designed so that the instantaneous center of the knee joint of the exoskeleton and the instantaneous center of knee joint rotation of the natural gait are in the same motion trajectory.The particle swarm-genetic hybrid optimization algorithm(GA-PSO hybrid optimization algorithm)is applied to determine the linkage rod parameters.Thus,the human-machine motion synergy and motion compatibility are ensured in the mechanism.2.Research on the design of lower limb exoskeleton structure based on the lower limb posture synergy relationship.Firstly,the design of the lower limb exoskeleton actuator was carried out using the human lower limb posture synergy characteristics.Then the structural design of the back adjustment structure,hip joint,ankle joint,large and small leg adjustment mechanism and other components of the main part of the lower limb exoskeleton was completed.3.The kinematic dynamics of the hip and knee joint postural synergy exoskeleton was studied.Firstly,the kinematic equations of the exoskeleton were established using the D-H method,and the end position posture matrix was obtained.Then,according to the motion law of human walking cycle,the kinetic models of single-leg support phase and swing phase of the exoskeleton were established by using Lagrangian method,and the relationships of wire rope tension,wire rope displacement,joint driving torque and joint turning angle were obtained by combining with the principle of virtual work.5.A control strategy for the co-assisted lower limb exoskeleton with split-time assistance is established.Since a single wire rope is used to drive both joints,the time period in which the two joint moments have the same polarity and contain the most positive power is found by combining the moment and power curves of the hip and knee joints,thus obtaining the percentage of the time of the assist to the total gait cycle.Based on the human-machine coupled dynamics model established by the Lagrangian method,the desired moment trajectory is obtained,leading to the design of an underdrive control scheme with an outer loop of force feedback and an inner loop of position feedback.The simulation results demonstrate the effectiveness of the control scheme and the ability of the lower limb exoskeleton designed using postural synergy theory to reproduce human lower limb movements.