The use of pseudo-inverse methods in reconstructing loads on a missile structure

Abstract

A missile during air carriage is subjected to high vibratory forces. These forces consequently impose high levels of stress on the attachment points to the aircraft. A repetitive application of stress causes fatigue. However, since the vibratory forces cannot be measured directly at the interface, an inverse method utilising missile accelerometer data has been used to determine the forces. This paper presents two frequency domain techniques of reconstructing loads. Both techniques utilise the Moore-Penrose pseudo-inverse method, although the second procedure incorporating a normal modes analysis is perhaps better suited for embedding within a health and usage monitoring system (HUMS). Both techniques enable discrete dynamic loads, which are applied to a finite element model in the time domain, to be successfully reconstructed. Consequently, by identifying forces on a missile structure successfully, the presented techniques enable a better structural integrity assessment to be undertaken.