Research On Mechanical Response Of Human Lower Limb Skeletal Muscle And Feedback Control Of Active Muscle Force

Human numerical model is widely used for biomechanical research in biomedical engineering,traffic safety,sports science,and other human involved activities because of its high flexibility and reproducibility.The human finite element models currently established are mostly based on animal experiments to obtain the material parameters of soft tissues,and less active muscle force control strategies are considered in the finite element models.In this paper,we based on the 3D active muscle lower limb model established by the team's previous research to further enhance the bio-fidelity of the finite element model,at the same time,the active muscle force control strategy is coupled to establish a biomechanical lower limb model that can monitor the tissue stress under motion.The main research results are as follows:1.Taking animal skeletal muscle and human lower limb skeletal muscle as experimental samples,the uniaxial compression experiments were carried out on the two parameters of strain rate and skeletal muscle fiber direction,and the influence of experimental parameters on the passive compression mechanical response of skeletal muscle was studied.The experimental results show that the mec hanical response of the skeletal muscle of the animal is significantly different from that of the human skeletal muscle.The strain rate has a significant effect on the mechanical properties of the skeletal muscle,and the stress increases with the increas e of the strain rate.The influence of the skeletal muscle fiber direction on the mechanical properties is also significantly,the compressive stress in the 90 degree fiber direction is significantly greater than the 0 degree fiber direction.2.The finite element model of skeletal muscle with the same experimental conditions was established to simulate the mechanical properties of three different materials constitutive(third-order QLV model,second-order Ogden model,first-order Ogden-coupled third-order QLV model).Based on the inverse finite element method,the skeletal muscle compression experimental curve was fitted by parameter inverse and optimization,and the optimal material constitutive model of skeletal muscle and its material parameters were determined.The simulation results show that the first-order Ogden coupled third-order QLV constitutive model can better characterize the kinetic characteristics of skeletal muscle,and the experimental results are consistent with the simulation results.3.Based on the obtained material parameters,the relevant parameters of soft tissue in the finite element model of lower limbs were updated.At the same time,three different muscle force control methods(CMC,PID,CMC coupled PID)were coupled to establish a finite element model of lower limbs with active muscle force controllable.The established model was used to study the differences in lower limb kinematics with different control methods,and verified the validity by compared with experimental data.The simulation results show that the control method of CMC coupled PID can better fit the experimental data and achieve active muscle force control.Based on the existing 3D active muscle lower limb model of the human body,this study further enhances the bio-fidelity of the model through skeletal muscle material characteristics experiments and parameter inverse optimization.At the same time,through the comparative analysis and the establishment of a new muscle control strategy,coupled with the finite element model of the lower limbs,effective motion control and stress monitoring under dynamic loading are realized.The new model of integrated muscle control strategy will lay the foundation for theory and model of human lower limb injury analysis and auxiliary equipment design.