Andres Marcos

Damage detection and identification are important for many aerospace and aeronautical structures. Vibration-based methods check changes in modal parameters, such as natural frequencies and mode shapes, usually indicating damage. For large structures, comparing each mode and parameter separately is impractical. This study proposes the modified total modal assurance criterion (MTMAC) as a single index for damage detection. To provide localisation, MTMAC is paired with the coordinate modal assurance criterion (COMAC), a standard tool for locating damage using mode shapes. Accurate modal identification is required to support structural health monitoring (SHM). For this purpose, the recently introduced improved Loewner Framework (iLF) is used. Noting that this is its first application to SHM, its performance on an undamaged BAE Systems Hawk T1A jet trainer wing is compared with literature results. Then, the iLF is applied to damaged states of the same airframe. In all cases, the aircraft vibration testing is carried out under multiple-input, multiple-output conditions. The identified modal sets are used to compute the MTMAC for detection and severity, and COMAC for localisation. Results show that the iLF provides robust modal identification for SHM and that the MTMAC effectively detects damage.

This article presents fault-tolerant dynamic allocation strategies designed to mitigate propulsion and actuation failures in launch vehicles using a clustered engine configuration. In particular, it addresses engine thrust loss and thrust vector control (TVC) jamming faults during the atmospheric ascent flight of a five-engine launch vehicle. Three different strategies are introduced: a fault-tolerant pseudo-inverse solution, a convex optimization-based approach, and a constrained nonlinear optimization one. These approaches are analyzed and compared at a linear design point and further evaluated using a nonlinear simulator of the launcher. The results demonstrate that these three dynamic allocation techniques are able to provide successful recovery from engine thrust loss failures (up to a certain level depending on the engine throttling capability), TVC actuator jamming failures, and simultaneous engine and actuator failures.