Research On The Assisting Strategy Of Exoskeleton For Ankle Joint With Load

Weight bearing walking is the most common exercise in human daily activities.Exoskeleton assiting for lower limb can reduce walking metabolic energy.In this paper,the biomechanical modeling and calculation of the lower limbs are carried out to quantify the biomechanical characteristics of the hip,knee and ankle joints.The general assisting strategy of the ankle exoskeleton is studied to reduce walking metabolism.The difference of assistance between individuals is analyzed.Based on this,the personalized assisting strategy of the ankle exoskeleton is explored to further optimize the assistance effect of the exoskeleton.Finally,universal and personalized ankle exoskeleton assisting strategies are verified on the experimental platform.This paper provides a new idea and engineering scientific method for the assisting strategy of ankle exoskeleton under weight-bearing walking.(1)Biomechanical study of human lower limb walking.The function and structure of key muscles are analyzed.Based on the mathematical model of muscle force and metabolizable energy,the influence of weight-bearing on joint torque and key muscle power is calculated,and the dynamic characteristics of hip,knee and ankle joints are quantified.The results show that compared with hip and knee joint,ankle joint under weight-bearing walking has greater assiting potential.(2)The universal assisting strategy of ankle exoskeleton.A human-exoskeleton coupling dynamics simulation platform is studied.The assiting force curves composed of different assiting time were designed to study the influence of the universal assisting strategy composed of four help curves on the metabolism of weight-bearing walking.The results show that there are differences in assiting parameters among individuals.The later peak time can achieve better assisting effect and reduce 6.85 ±2.35% metabolic energy.(3)Research on personalized assisting strategy of ankle exoskeleton.In the humanexoskeleton coupling dynamics simulation platform,taking the minimum metabolic energy of weight-bearing walking as the objective function,Bayesian optimization algorithm is used to iteratively optimize the starting time and peak time of assisting force curve to find the optimal parameters of ankle exoskeleton.The results show that the parameters optimized by personalized assisting strategy can further reduce the metabolic energy by 7.56 ±2.09%.(4)The experimental verification of assisting strategy of ankle exoskeleton.On the platform of ankle exoskeleton,the weight-bearing walking assistance experiment of 7subjects was carried out to compare changes in metabolic without and without assistance.To verify the universal assisting strategy,it was found that the best assistinge curve reduced the net metabolism by 9.6 ±9.8%,and the exoskeleton assisting parameter has individual differences.The personalized ankle exoskeleton assistance strategy was verified,and it was found that the optimized assistance parameters further reduced the net metabolism by19.7 ±8.5%.Bayesian optimization algorithm converges in14.4 ±2.6 minutes.