EPS Functional Safety Design And Test Based On MCU-in-the-Loop Simulation

Electric power steering system (EPS) uses the motor as the power source, while theelectronic control unit controls the size of assistant torque, so it can ensure portability ofsteering at low speed, while maintaining a sense of road at high speed. Also, EPS has moreadvantages, such as energy saving and environmental protection. Nowadays, EPS are moreand more favored by consumers and auto companies, and has broad application prospects.EPS assists the driver’s steering movements with real-time intervention, and thereforeits safety is particularly important. Based on functional safety as the main line, reference toRoad Vehicle Functional Safety standards ISO26262, this paper studied the design andtesting method of EPS system, and implemented the functional safety goal-driven designmodus, and proposed a new test method called MCU-in-the-Loop Simulation.Functional safety goal-driven design method is to first determine the function of thesystem safety goal, and then studies how to design the system architecture and securitymechanism can satisfy the security goals, finally, in accordance with the requirements of thesystem architecture and security mechanism for the development of hardware and software.According to the above design method, this paper carried out the EPS system hazardanalysis and risk assessment, and made "prevent Unintended Steering" as the functionalsafety goal of EPS system, and defined the safety integrity level and system functional safetyrequirements. Then, with the functional safety goal and requirements as a guide, this paperdesigned the EPS system architecture and safety mechanisms. Finally, according to the EPSsystem architecture, this paper designed the hardware architecture and the hardware circuit;On the software side, according to the idea of a hierarchical and modular design of the EPSsystem software architecture and safety monitoring software, this paper carried out the workof software development and testing of integration unit.MCU-in-the-Loop Simulation is an optimized Hardware-in-the-Loop Simulation, it can be convenient for ECU external and internal circuit fault injection simulation test, to helpdevelopers verifying the safety of an electronic control system.In order to confirm the design of the EPS system meets the functional safety goal andrequirements, this paper established the MCU-in-the-Loop Simulation test system. Thispaper took aim at the faults that may lead to the occurrence of "unintended steering", andcarried out the fault injection test to verify whether the EPS controller can detect a fault’soccurrence, and promptly switch the system to a safe state.