| Low back pain is one of the occupational diseases in the field of transportation,and is the focus of seat comfort research.Reasonable design of car seat can effectively relieve discomfort such as waist fatigue.Starting from biomechanical indicators such as joint strength and muscle strength,it is expected to explain the inherent biomechanical reasons of seat discomfort.This article aims to establish a human musculoskeletal biomechanical model that can solve joint force and muscle force.Quantitative assessment of joint force and muscle force provides theoretical guidance for the prevention of low back pain and seat comfort design from the perspective of biomechanical loading.The OpenSim biomechanical simulation platform was used to build a full-body model with detailed spinal information,and add head,neck and limbs based on the Christophy spinal biomechanical model,then adjust the degrees of freedom at the joints of the limbs according to the true degrees of freedom of the human limbs to simulate daily human movement.In addition,the Thelen-type muscle-tendon model was built to add muscle groups of the lower limbs of human body.The intervertebral mechanical model was characterized by the intervertebral stiffness value obtained from the load displacement experiment.In order to verify the model and change the posture of the human model,the lumbar joints were adjusted to 6 degrees of freedom,and the lumbar spine joint angle distribution relationship was set in flexion-extension and roll motions.Validate the human musculoskeletal model in terms of joint strength,muscle force,kinematics.In order to effectively avoid human differences,the correlation between the simulation results and the experimental measurement data in the literature was analyzed.The correlation coefficients of the L4-L5,L3-L4 joint force,the erector spinae muscle force,the intervertebral pressure and the result of EMG signal were all greater than 0.9,which indicate that the biomechanical simulation has a strong correlation with the experimental measurement results,and the error of the direct comparison between the L4-L5,L1-L2 joint force and the literature was 6.3% and8.2%,respectively.Verifying the kinematics trend of the biomechanical model showed that the model was in good agreement with previous researches and experimental results.The musculoskeletal model can be used as a suitable method to explore the inherent biological mechanism of seat comfort.Use this model to perform simulation analysis of car seat comfort on OpenSim platform,and the effects of lumbar support thickness,human body size,and seat back tilt angle on driver comfort were discussed.The results of different lumbar support thickness studies have shown that 4cm thickness lumbar support can significantly reduce the driver’s waist load and improve comfort,and the joint forces of L5-S1,L4-L5 were reduced by 11.82% and 11.33% on average.The effect of height and weight on biomechanical load shows that the joint force and muscle force of each lumbar spine increased approximately linearly with the increase of body weight,but their correlation with height was insignificant.Consequently,the biomechanical load is mainly affected by the weight of the receptor.When the inclination of the seat cushion was 10 degrees,the biomechanical load did not decrease with the process of adjusting the seat back tilt angle from 23 degrees to 33 degrees,but peaked at 25 degrees.Taking the radiological assessment conclusion into consideration,the recommended seat back tilt angle was 29 degrees and 31 degrees. |
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