This paper presents a model-based fault diagnosis and prognosis scheme for a vehicle steering system. The steering system is modeled as a hybrid system with continuous dynamics and discrete modes using the hybrid bond graph tool. Multiple faults of different types, i.e., abrupt fault, incipient fault, and intermittent fault, are considered using the concept of Augmented Global Analytical Redundancy Relations (AGARRs). A fault discriminator is constructed to distinguish the type of faults once

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... ey are detected. After that, a fault identification scheme is proposed to estimate the magnitude of abrupt faults, the characteristic of intermittent faults, and the degradation behavior of incipient faults. The fault identification is realized by using a new adaptive hybrid differential evolution (AHDE) algorithm with less control parameters. Based on the identified degradation behavior of incipient faults, prognosis is carried out to predict the remaining useful life of faulty components. The proposed algorithm is verified experimentally on the steering system of a CyCab electric vehicle. Index Terms-Adaptive hybrid differential evolution (AHDE), augmented global analytical redundancy relations (AGARRs), fault discriminator, model-based diagnosis and prognosis, remaining useful life (RUL). NOMENCLATURE AGA Adaptive genetic algorithm AGARRs Augmented global analytical redundancy relations AHDE Adaptive hybrid differential evolution ARRs Analytical redundancy relations BDE Binary-valued differential evolution BG Bond graph DC Direct current DE Differential evolution DHBG Diagnostic hybrid bond graph EOL End of life FDI Fault detection and isolation FDV Fault discrimination vector FSM Fault signature matrix GA Genetic algorithm GARRs Global analytical redundancy relations HBG Hybrid bond graph HDE Hybrid differential evolution Manuscript MCSM Mode change signature matrix MD-FSM Mode-dependent fault signature matrix ODE Ordinary differential equation PCI Peripheral component interconnect PWM Pulse-width modulation RDE Real-valued differential evolution RUL Remaining useful life SCAPH Sequential causality assignment procedure for hybrid systems Ming Yu (M'12) received the B.E. and M.S. degrees