Design And Optimization Of The Wearable Upper Exoskeleton's Key Parts

The wearable exoskeleton is widely used and it can play an important role in the military and daily life.In particular,China's elderly population is increasing every year,and older persons are in lack of physical functions.In addition,a large number of people lose the normal functions due to a variety of reasons,and they cannot completely adapt to daily life.The wearable exoskeleton can help them live a normal life.However,the characteristics of heavy weight,high price and difficult maintenance greatly hinder the promotion and application of wearable exoskeleton.As an important part of the exoskeleton,the dynamic joint can provide a driving force for the exoskeleton.Now there are no uniform and universal modules.Therefore,in this paper,a kind of universal dynamic joint featured by low costs and simple maintenance is designed,which is significant to the exoskeleton.First,the driving mode of the dynamic joint for wearable exoskeleton at home and abroad is analyzed.In addition,the qualitative analysis is made on the usability,weight,efficiency,output capacity,cost,reliability and controllability and other aspects of three kinds of drive systems,such as motor drive system,hydraulic drive system and pneumatic drive system.The motor and gear reducer are selected as driving power for the dynamic joint.Then based on the input and output parameters of gear reducer and the calculations of gear safety factors,the gear materials for dynamic joint are selected.According to the transmission requirements and characteristics of dynamic joint,the final drive of joint output adopts the planetary drive mode.Compared with the traditional drive mode,the transmission efficiency is improved and the overall volume is reduced.In addition,using the software MATLAB,with the constraints of transmission ratio,contact fatigue strength of tooth surface,bending fatigue strength of tooth root and tooth width,with the moment of inertia and weight as the objective,the gear transmission is optimized so as to provide the best mechanical characteristics for the later application and control.Meanwhile,the finite element analysis is made on the optimized gear in the case of simulated meshing,and the strength and stiffness of gear are checked.With the resulting stress nephogram and displacement fringe,the gear portions with relatively small internal stress and displacement are removed to reduce the overall inertia and quality,so as to achieve the purpose of further optimization.Finally,the geometric design is made on the dynamic joint cabinet,and the finite element analysis is made on the planetary carrier and the output rocker in the various stress conditions respectively.The stress nephogram and displacement fringe are obtained.With the design of insight function,the overall stress of the cabinet is checked so as to ensure the safety performance of the cabinet in all cases.According to the design of the gear transmission and the box to make the test specimens,the experimental results show that the key parts of the external skeleton of the mechanical design of the dynamic joint can satisfy the requirements of strength and stiffness.