“Virtual Failure Mode and Effects Analysis” (vFMEA), a novel safety-verification method of control software for automotive electronic systems, was proposed to save prototyping cost at verification stage.
The proposed vFMEA is system-level FMEA method, which uses virtualized electronic control units (ECUs) consisting of microcontroller models on a microcontroller simulator and a transistor-level circuit models on a circuit simulator. By using the structure, the control software in binary code formats can be verified when a circuit-level fault occurs in the ECU hardware.
As an illustrative example, vFMEA was applied to an engine ECU. As a result of short-circuit fault into a driver IC, engine revolution and engine speed decreased. However, the engine continued to operate normally when an open-circuit fault occurred in a capacitor connected in parallel. Effects of the hardware faults in ECU on a vehicle are demonstrated; thereby software verification can be performed using vFMEA system.
Additionally, to realize vFMEA, it is necessary to tackle a challenge concerning degradation of simulation speed caused by analog circuit simulation. A mixed-level modeling method of a peripheral circuit in ECU, which prevents a decrease in simulation execution speed, is proposed. Application of the modeling method to the IC reduced the degradation of the execution speed.
vFMEA can, therefore, not only perform safety verification of the software when circuit-level faults occur in ECU, but also reduce the degradation of the execution speed. These mean that using vFMEA as a software-verification environment with fault injection will keep prototyping cost to a minimum.