The Research Of Knee Passive Exoskeleton Assistant During Stair Descent

The lower limb passive exoskeleton has potential advantages in enhancing human walking ability and reducing the burden in a certain range of gait due to its characteristics of light weight,portability and high stability.Compared with other gaits,lower extremity knee joint shows larger bending Angle,extension moment and more negative power interval.In this paper,the following floor is a special scene.Linear and nonlinear energy storage elements are taken as the research objects respectively,to provide a set of new design solutions for the passive spring-like knee exoskeleton.Specific research work includes:Establishment of a spring-like passive knee exoskeleton assist model.Based on the published literature on gait and biomechanics,the kinematics characteristics of knee joint,anatomical characteristics of knee joint,in vivo kinematics and muscle biomechanics models of daily gait were summarized.According to the design principle of the exoskeleton and the gait of the knee joint of the normal young people,the mechanism of two kinds of spring arrangement forms,parallel arrangement and action Angle arrangement,was established.Finally,a spring-like passive knee exoskeleton assisted model based on the downstairs scene was established.Study on the downstairs aided design of the linear passive knee exoskeleton.According to the characteristics of linear energy storage element,the method of action Angle arrangement is adopted to further simulate and verify the power assist principle.The exoskeleton layout design is discussed in detail considering the man-machine adaptability,and the double-hinge design is designed to accommodate the valvation of the knee joint.To respectively to discuss the effect of different angles and stiffness simulation finally gets the optimal linear passive exoskeleton Angle and the energy storage element stiffness parameters,plane vortex coil spring is put forward as a kind of spring energy storage element to realize linear class spring mechanism,the function of knee joint energy storage and release through finite element simulation verifies the stiffness curve design parameters,Finally,a prototype of linear passive knee exoskeleton was designed and developed.Design of nonlinear spring-like knee exoskeleton mechanism.The extension of the class of linear spring energy storage element stiffness matrix to order n,knee extension torque,peak to peak knee negative power and knee is power as the optimization goal,the direction of the former kind of spring mechanism as constraint conditions,the resulting nonlinear class spring mechanism under different weight 1 ～ 6 order to optimize the stiffness matrix,and carries on the statistical analysis with different weights,finally it is concluded that the optimal weights.The results of optimal weight optimization show that the effect tends to be stable when the stiffness matrix is above the third order.The CAM and spring mechanisms are used to design the optimized stiffness matrix mechanism.The results show that the design mechanism is consistent with the 5th order stiffness matrix.Finally,a prototype of the nonlinear spring-like mechanism is designed and developed.The construction of the experimental test and evaluation system and the verification of the prototype exoskeleton.A prototype of the test system with dry electromyography and inertial measurement unit(inertial measurement unit)as the sensing system is built.Gait consistency was evaluated by measuring ankle and knee angle data with the linear exoskeleton prototype,and the test results showed that there was no significant difference in ankle and knee angle between wearing and unwearying knee exoskeleton.The auxiliary effect of the linear exoskeleton prototype on the human body in the process of descending was evaluated by the EMG signals.The rectus femoris muscle and biceps femoris muscle of human lower limbs were selected as the typical genicular extensor muscle and genicular flexor muscle respectively as the test objects.The test results showed that the linear exoskeleton prototype could reduce the average normalized activation degree of the rectus femoris muscle by 6.12～13.54%.The stiffness curve of the nonlinear spring-like mechanism was verified by setting up a mechanism operating stiffness test bench.The torque of the prototype of the nonlinear spring-like mechanism at 0～95° was tested.The results of loading and unloading sampling points showed that the stiffness curve of the mechanism was consistent with the trend of the optimization results.