Development Of EMCVT Fault Diagnosis System Based On Road Vehicle Functional Safety

With the development of electronic technology,automotive electronic control technology has been widely used,bringing convenience to consumers,but also new safety issues.The application of many electronic control units makes the automobile constitute a complex electronic and electrical system,and the harm caused by the failure of electronic products has gradually become a hot topic in the process of research and development of automobile products.Aiming at the failure of automotive electronics,the ISO26262 functional safety standard regulates and guides the development process of automotive electronics products.As an important part of the vehicle transmission system equipped with EMCVT.Therefore,it is of great significance to carry out systematic functional safety design in accordance with ISO26262 standard in the software design process of TCU for improving the functional safety level of the vehicle,meeting the prevailing industry standards and product generalization.In this paper,the fault diagnosis system of EMCVT is designed based on functional safety standard.The main work of this paper is as follows:(1)Taking the ISO 26262 functional safety standard Part 3 as the theoretical basis,the concept phase design of EMCVT is carried out.According to the functional requirements,working environment and known failure modes of EMCVT,relevant item definitions,hazard analysis and risk assessment are carried out,3 influencing factors of quantitative risk and the assessment details and principles of ASIL are analyzed,and safety goals are obtained;Perform FTA analysis on hazard events according to safety goals,and derive functional safety requirements and technical safety requirements for single points of failure that violate safety goals.(2)EMCVT functional safety design.According to the functional safety requirements and technical safety requirements,the fault diagnosis theory based on structural analysis method is used to design the fault diagnosis,fault tolerance control and safety state transition system of EMCVT.Firstly,the fault modeling is carried out for the key faults that cause the failure of the ratio control function,and the fault diagnosis system is designed to realize the real-time monitoring of the key signals of the system.According to the diagnosis results,the control signal is reconstructed to control the sensor fault,the key signals in the ratio control system are obtained again,and the fault signals are switched to the reconstructed signals,to realize the fault-tolerant control of the ratio control function under the sensor fault state,and make the system run stably.(3)EMCVT functional safety test.According to the model-based design method,the model-in-the-loop test and software-in-the-loop test of the control system are completed,and the control model is checked and verified to ensure that the model is consistent with the requirements and conforms to the modeling standards;The EMCVT hardware-in-the-loop test system based on the NI-PXI platform is built,and the fault injection test is carried out for several faults that may directly lead to the failure of the speed regulation function.The hardware-in-the-loop test results show that the designed safety system can achieve safety state transition within the fault-tolerant time interval,which can provide a feasible solution to the safety problem of EMCVT speed regulation function.