| As people’s requirements for vehicle intelligence and networking increase,ECUs with multiple functions are widely used in Premium cars,and the complexity of electronic control systems has gradually increased.Along with the diversification and complexity of automotive electronic control systems,automotive safety issues caused by the failure of automotive electrical and electronic components have also attracted widespread attention.For this reason,ISO issued the ISO 26262 standard.The three stages of electronic products(the concept stage,the product development stage,and the product release stage)put forward requirements.In this paper,the safety module software is added to the original HPCR(high-pressure common-rail)diesel engine ECU software based on torque control,and after the software is integrated,joint simulation test research is conducted.The research content and results include:First,according to the requirements of functional safety standard ISO 26262 for software development,including software design and testing,the safety issues of ECU control software for HPCR diesel engines are analyzed.As there are many software safety issues in the electronic control system of diesel engines,taking the acceleration of vehicles not required by the driver as an example,hazard analysis and risk assessment are carried out.Determine the safety target to prevent non-driver demand acceleration and the automobile safety integrity level ASIL C level according to the three failure modes that cause unexpected acceleration of the vehicle(brake pedal failure,spontaneous acceleration,braking hysteresis)The fault tree analysis method analyzes the three failure modes separately,finds the modules that may cause unexpected acceleration,and merges the software functions of these modules into the ECU software safety requirements to avoid non-driver’s intention to accelerate.Secondly,based on the principle proposed by the ISO 26262 standard for the development of the "V" shape,and based on the safety requirements of the ECU software,Matlab / Simulink is used to add a functional safety control model to the original HPCR diesel ECU control software.The model includes modules such as power supply,brake pedal,accelerator pedal,rail pressure,and torque limit.Perform fault detection on the original sensor signal(including power supply voltage failure,brake pedal state failure,accelerator pedal overrun or unreasonable signal failure,rail pressure overrun fault,and sensor contact fault failure,etc.),according to different failure modes of each fault,Choose different alternative methods,such as accelerator pedal signal 1 overrun fault,then use twice the accelerator pedal signal 2 as the pedal opening output,and limit the output torque and reduce the amount of fuel injection,so as to avoid the acceleration of non-driver intention.Finally,in order to verify the functionality and reliability of the functional safety control model,the control model in Simulink environment and the controlled model of diesel engine in GT-Power environment are coupled for joint simulation.The first part tests unit module of the Simulink control model to verify the functionality and logic of the five unit modules;the second part tests joint simulation to integrate functional safety modules into the original diesel ECU control software.The interface connects the Simulink control model with the diesel GT-Power physical model to conduct simulation test research on the functional safety model.Under three operating conditions(1400 r/min,load rate 10%;1500 r/min,load rate 25%;1800 r/min,load rate 50%),the functional safety model can limit the engine speed from 2200 r/min By 2050 r/min,the engine output torque is limited from 304.12 Nm to 265.53 Nm and the fuel injection volume is reduced from 55.18 mg/cyc to 47.78 mg/cyc to ensure the safety of the system.The results of joint simulation show that the functional safety control model runs reliably and meets the requirements of functional safety. |
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