Safety-critical Technologies Of Monorail Train Control Systems

Monorail is a light-duty,medium-speed urban rail transportation,with lots advantages of short construction periods,low manufacturing cost,without ground transportation resources,low carbon,etc.It is a potential mode of urban rail transit.Due to the specific installation requirements of monorail signaling system equipment,the traditional track circuit,train-wayside communication equipments cannot be applied directly.The foreign signal systems of monorail have achieved full automatically driving,but domestic research of this area is still at an early stage.Developing a monorail train control system is not only the urgent market demand,but also meaningful security and sustainability of urban rail transport development.This papers researches on safety-critical technologies of monorail train control systems based on in-depth analysis of related products,technologies and standards.First it researches common safety-critical computer architecture,the Double-Triple-channel Redundant and Fault-tolerant System and Triple Voting System based Dual CPU are proposed and simulated to compare RAMS(Reliability,Availability,Maintainability and Safety)performance to traditional triple and quadruple systems.Then a combined method of HAZOP(Hazard and Operability Analysis),FMECA(Failure Mode Effects and Criticality Analysis),FTA(Fault Tree Analysis)and risk matrix for hazard identification and risk assessment is used to get system safety requirements.After that architecture design,safety design and verification of monorail ATP(Automatic Train Protection)system are implemented.Then the core algorithms of the monorail ATP system including monorail vehicle brake curve model,fused GNSS(Global Navigation Satellite System)multi sensors integrated speed measuring method are studied.At last the VOU(Vital Digital Output Unit)is studied to verify the theoretical research in this paper,including processes of hazard analysis,design,development and verification.This paper focuses on the core content includes:(1)Proposes architectures of Double-Triple-channel Redundant and Fault-tolerant System and Triple Voting System based Dual CPU,simulates them using reliability block diagram and Markov process model to compare RAMS performance with traditional triple and quadruple systems.(2)The safety design and verification technology of monorail ATP system based on risk analysis is studied.During the whole system development life cycle,combined methods of HAZOP,FMECA,FTA and risk matrix are proposed in phases of hazard identification,risk analysis,hardware design and dangerous failure probability calculation.According to the results of risk analysis the system requirements are proposed,architecture design,safety design and verification are complemented.(3)The core algorithms of monorail onboard ATP system are studied.The monorail vehicle brake curve model is built to achieve overspeed protection function.A fused GNSS multi sensors integrated speed measuring method is proposed to solve the problem of speed measurement for low altitude suspension operation of monorail train.(4)Taking the VOU as an example,a combination of risk analysis is studied,system requirements are refined,design and development are complemented,and finally the performance,safety and reliability indicators are verified.The result shows that mean time between failure of VOU is up to 1.17*106h and dangerous failure probability is 1.14*10-13/h.In this paper,the safety-critical technologies of monorail train control systems are the main research content.The several safety-critical technologies including safety-critical computer architecture,monorail vehicle brake curve model,fused GNSS multi sensors integrated speed measuring method and vital digital output unit are studied.The research process follows the international safety standards such as EN 50126/8/9 and the main goul is to improve safety performance in order to ensure the production and engineering of monorail train control system.