Reliability Analysis Of Lower Extremity Assisted Exoskeleton Robot Based On FMECA And FTA

In view of the increasing number of disabled people with lower limbs and the increasing demand for rehabilitation training equipment,the lower extremity assisted exoskeleton robot has gradually begun to be applied in modern rehabilitation medicine as an intelligent rehabilitation medical equipment.In the medical device specification,equipment reliability is an extremely important indicator,which has a significant impact on the normal operation of the equipment and even the safety of the user.Therefore,reliability analysis of exoskeleton is of great significance.The combination of FMECA(Failure Mode Effects and Criticality Analysis)and FTA(Fault Tree Analysis)is an effective reliability assurance technology,which can find the defects and weaknesses of system design by analyzing the impact of fault mode on the system and the internal relationship of fault factors.Thus we can specifically improve the reliability of the exoskeleton system.This article will use FMECA and FTA to analyze the reliability of a lower extremity assisted exoskeleton robot.The specific work content is summarized as follows:(1)The structural composition and working principle of the lower extremity assisted exoskeleton robot are analyzed,and the whole system is divided into four subsystems.On this basis,the reliability model of the system is established.According to the FMECA principle and the actual situation,the level of agreement of the subsystem is divided,and the correspondence diagram of the structure function is drawn.(2)According to the collected failure mode data,the criterion for evaluating the hazard of the lower extremity assisted exoskeleton robot is established.Combined with the FMECA principle,the causes and effects of various failure modes of the lower extremity assisted exoskeleton are analyzed,and the FMECA form is output.According to the results of FMECA analysis,the high-risk failure modes in each subsystem are pointed out,and corresponding improvement measures are proposed.(3)The four subsystems of the lower extremity assisted exoskeleton are respectively modeled by the fault tree to find the intrinsic relationship between the fault factors.And qualitative analysis,the results show that the order of the minimum cut set in each subsystem fault tree is one,the bottom event is a single point of failure,should take compensation measures to try to avoid.At the same time,in view of the lack of reliability data of the lower extremity assisted exoskeleton system and the failure of the traditional FTA quantitative analysis method,this paper uses fuzzy FTA to quantitatively analyze the fault tree,calculates the probability of fuzzy occurrence and importance,and the main factors leading to the top event in each subsystem are obtained.Through the above analysis work,the high-risk failure mode and weak parts of the lower extremity assisted exoskeleton robot are obtained,which provides a reference for the improvement of the exoskeleton system and the reliability improvement.