The Research On The Functional Safety Designing And Analysis Of EPS Controller

With the application of Electronic/Electrical/Programmable system(E/E/PES) in vehicles becoming more and more influent, the function of vehicle are very rich and the traffic and recalling of vehicles as the failure of electronic system is also increasing too. Although EPS system brings the driving comfort to the drivers, at the same time EPS controller is closely related to safety, it is particularly urgent to do research on how to make the controller meet the assistance performance and the functional safety requirements simultaneously. Since the promulgation of road functional safety standard ISO26262 in 2011, it makes some norms of product development security process life cycle of automotive electrical and electronic, at the same time the fifth part of the standard guides the process of hardware development and evaluation.In this paper, the safety life cycle and automobile safety integrity level is introduced, and the ASIL and safety goal values of the EPS system are confirmed. The hardware structure and the every function module circuits are designed based on the dual core microprocessor of MPC5643 L chip.With the ISO26262 standards and IEC62380 data of handbook, through the calculation of the failure data of components, the hardware architecture of parallel redundant circuit of torque sensing is calculated. And an improved strategy with higher hardware architecture value- heterogeneous redundancy circuit, in addition the diagnosis strategy is added into the software strategy to achieve higher hardware architecture.Then with the aid of Isograph fault tree analysis software, the fault tree model of EPS controller is established with "non driver’s intention steer" as the top event, in accordance with the sort of acquisition, decision-making, implementation until to the electronic components in the circuit. Through the quantitative calculation of FTA, Probabilistic Metric for Random Hardware Failures value is got to compare and evaluate with the safety goal value.Finally, the steering test bench and the upper monitoring software are established. Redundant signal of torque and basic functional of the EPS controller is tested and verified. Through the development of fault injection circuits, faults are injected into the torque signal, and the security mechanism of EPS controller is verified that can meet the demand of function safety.