Design Of Upper-Limb Powered Exoskeleton Based On Topology Optimization

As a human-machine integrated power-assist device,the exoskeleton robot can identify the wearer’s motion intention by collecting the motion information of the human body,and provide power for the movement of his limbs.And more and more researchers have focused on the study of exoskeleton robot for its broad use prospects in medical,military and disaster relief.Lightweight design is the key point in exoskeleton robot research,and currently,to-pology optimization is a widely used method.However,the finite element analysis of the part to be optimized is usually conducted based on the single working condition of the robot with equivalent constraints,which lead to the stress analysis distortion phenomenon.In this paper,a method based on the finite element model of the robot assembly under multi-work-ing conditions is proposed to avoid the deviation and improve the rationality of the optimi-zation result.Then,this method is applied to the lightweight design of the designed 5 DOF upper limb exoskeleton robot,which is abbreviated as assembly-base topology optimization method under multi-working conditions.Aiming at the requirement of anthropomorphic design of upper-limb powered exoskel-eton,the analysis of the structure and motion mechanism of human upper limbs and the configuration design and kinematics analysis of upper limb robot are carried out.Then,the preliminary design of the exoskeleton structure is completed based on the result of above analysis.Finally,based on the kinematics analysis,the workspace of the robot is drawn by the Monte Carlo method.The relationship between the finite element analysis and topology optimization is found out by the study of their basic principle.Then the problem of the existing topology optimi-zation,which is carried out based on the finite element model of the part to be optimized by adding equivalent constraints to it,is analyzed,and the method that based on the analysis of the assembly is proposed.To verify the effectiveness of the proposed method,the lightweight design of a single-joint robot based on it and the conventional one are conducted.Then,the problem of topology optimization in serial robots based on a single working condition are analyzed,and an optimization method based on the analysis of multiple typical working conditions of the robot is proposed.The extreme working condition applied to the topology optimization of the part can be obtained by comparing the finite element analysis results of the robot under several typical working conditions.Base on the solutions above,the assem-bly-base topology optimization method under multi-working conditions is proposed,and the steps of optimization based on it are introduced.The lightweight design of the upper-limb exoskeleton is conducted based on the pro-posed structural optimization method.Meanwhile,the optimization method based on the assembly under a single working condition is also applied to the lightweight design of the same robot to verify the effectiveness of the proposed method.The total mass of the parts optimized based on the proposed method is reduced by about 40%,which shows the weight loss effect this method is close to the existing optimization method based on single working condition analysis.Besides,the finite element analysis of the optimized robot based on these two methods demonstrates that the maximum end displacement of the exoskeleton optimized under single working condition has exceeded the constraint while the robot optimized based on multi-working conditions has not.And the maximum stress of the robot optimized by the proposed method is reduced by 9.92%compared with the one optimized based on single working conditions.Therefore,the effectiveness of the proposed method based on multi-working conditions can be verified.The experiment platform of the 5 DOF exoskeleton robot is built based on the above work.Then,the load performance and command response delay of the designed exoskeleton are tested by the related experiment,and the result shows that the robot has met the design requirements.Finally,the exoskeleton was applied to the exoskeleton collaborative control experiment based on fNIRS motion intention recognition to study the motion intent recog-nition based on the fNIRS signals of human.