Damage propagation analysis methodology for electromechanical actuator prognostics

Historically in aviation safety, sensor technology intrusion has presented a barrier to enabling prognostic solutions into mission critical, on-board power systems. Without prognostics, catastrophic, intermittent, and damage propagation faults can compromise the integrity of even the best power systems over time. The problem posed by physical limitations, such as size, weight, and wiring, prevents the upgrade of in-flight power systems with prognostic equipment. The solution is development of a non-intrusive prognostic technologies suite designed for minimal impact on existing systems. Specifically, we explore a Hidden Markov Model (HMM) approach to prognosticate the servo loop of an EMA. Results of this study indicate that a fault-progression methodology overcomes some of the disadvantages of the more familiar FMEA approach, which does not account for the contribution of unobserved failure to a degradation trajectory. We show by example how the Ring-down methodology, often used in power systems, can be adapted to servo loop systems employed in aircraft actuator. Adoption of this approach to electronic prognostics improves monitoring of the behavior and health of key or critical components not only ensures safety and success, it makes dynamic switching to back-up systems, fault mitigation, load-shedding, and condition-based maintenance (CBM) technically and economically feasible.