Functional Safety of Electrified Vehicles Through Model-Based Fault Diagnosis

Functional safety is of great importance for electric and hybrid electric vehicles (EV/HEVs). One way to improve functional safety of EV/HEVs is developing reliable and robust fault diagnosis and fault tolerant control systems so that, once a component failure is detected, effective remedial actions are taken to avoid system failures. Robust fault diagnosis is a necessary precursor to fault tolerant control strategies. In this paper, we use a V-diagram to present a systematic process for conducting automotive fault diagnosis, in connection with fault tolerant control development. We also introduce a diagnostic approach based on structural analysis that can form the basis of fault tolerant control. The structural analysis approach makes it possible to evaluate a system's analytic redundancy by its structural model, using the mathematical model of the system in matrix form, from which it is possible to derive a set of analytic redundant relations for fault detection and isolation. Structural analysis is useful in the early stages of diagnostic design because specific knowledge of the system parameters in numerical form is not required. In the paper, we demonstrate the application of this methodology, and its broad usefulness, by carrying out the design of a diagnostic strategy for an electric vehicle equipped with a permanent magnet synchronous machine (PMSM) drive system. The EV case study focuses on sensor faults, but the methodology is applicable to any component faults.