Lumped parameters modelling of the EMAs’ ball screw drive with special consideration to ball/grooves interactions to support model-based health monitoring

Building a high-fidelity model to identify a connection between a measurable signal variation and the onset and growth of a fault, which can then evolve in a failure, is a method to develop a prognostic and health management system. With this goal, this paper is focused on the development of a high-fidelity dynamic model of the ball screw component of flight control electro-mechanical actuators. This model can represent the roll/slip transition in the spheres/grooves contact points depending on dynamic operative conditions. It is suitable for various defects injection, such as friction increase, preload variation or mechanical backlash. The effect of such defects on the mechanical direct efficiency is investigated since it is a parameter which can be easily measured experimentally, and which may be a suitable candidate as health feature or as an indicator of faults onset and progression within the mechanism. This approach is intended to track the health status of the component and consequently avoid unexpected in-service failure, which may have a high cost, especially in the aerospace sector.