Model-based condition monitoring of an actuator system driven by a brushless DC motor

Air pressure in passenger aircrafts is controlled by opening and closing an outflow valve, which serves to release air from the cabin. Early identification of potential malfunctions in the underlying actuator-driven system is important both from the point of view of cost-efficient maintenance as well as overall safety. This paper presents a system for diagnosing faults in a valve actuator driven by a brushless DC motor during off-line pre-flight tests. First, a simple mathematical model of the drive is developed. Based on this, parity relations are derived with the aim of fault detection. Fault isolation is realised by means of an approximate reasoning technique referred to as transferable belief model (TBM). The problem of distinguishing between faults with the same fault signatures is addressed. It is shown that additional improvements in terms of diagnostic resolution can be achieved by applying parameter estimation. The proposed FDI scheme is tested on the actual drive under various Faults. The achieved performance features high diagnostic resolution, diagnostic stability and accuracy. (C) 2001 Elsevier Science Ltd. All rights reserved.