Research On Functional Safety Of Logic Control Unit Of Subway Train

Rail transit plays an important role in solving urban traffic problems and has become one of the most popular travel modes.The existing subway train electrical control system uses relay control,which has the disadvantages of high failure rate and poor flexibility.With the rapid development of power electronics technology,microcontrollers,switching components,and network communication technologies have become more mature.It is the future development trend that the non-contact programmable controller represented by the train logic control unit(LCU)replaces the traditional relay control circuit.As the control and intelligent monitoring equipment of rail transit vehicles,LCU is closely related to the normal operation of trains,and its safety cannot be ignored.It is of great significance to study the functional safety of LCU.To this end,the thesis starts with LCU to study the security of the system composed of programmable electronics.This thesis mainly studies the functional safety of LCU.The main research content includes the safety design and functional safety assessment of LCU.Firstly,the research background and significance of functional safety and train LCU are introduced,and then the theory and technology of functional safety assessment are analyzed by the thesis,including the introduction of safety integrity and the analysis of factors affecting functional safety,which lays the foundation for the safety design and analysis later.Secondly,the overall design,hardware design and software design of the LCU are studied,especially focusing on the application of the 1oo2D structure in the LCU control system and how to use redundant design and diagnostic circuits to ensure the safety and reliability of the system.Then,the hardware safety integrity assessment of the LCU is researched,which includes the acquisition of failure data and the establishment of an evaluation model.Through failure mode and impact analysis,the basic failure data required by the functional safety model is calculated.The Markov and fault tree methods are used to conduct modeling and analysis to calculate the safety integrity level of the LCU.In view of the problems found in the research process,the measures to reduce common cause failures are analyzed,the common cause failure β factor model is revised,and finally the fuzzy fault tree method is used to improve the calculation model,indicating that the improved model is more in line with the actual characteristics of the failure model.The research results show that the LCU designed based on the safety theory has high safety.Various calculation models verify that the safety integrity level(SIL)can reach SIL2 level.Rail transportation products that meet safety standards are not only safer and more reliable in practical applications,but also have greater competitiveness in domestic and foreign markets.