Session: 07-08-03: Multibody Dynamic Systems and Applications III

Paper Number: 144880

144880 - Ball Screw Surface Faults Modeling and Detection for Electromechanical Flight Control Actuators 

Electro-mechanical actuators (EMAs) find diverse applications in aerospace, performing various functions of different degrees of criticality. A prevailing trend toward “more electric” aircraft and equipment has emerged in recent years, involving the gradual replacement of hydraulic actuators with the electromechanical solution (EMAs) for flight-critical operations, such as primary flight controls.

However, a significant challenge in integrating EMAs into primary flight control systems is their inherent risk of seizure or jamming, which is too high for such applications and has so far limited their widespread adoption, resulting in various attempts to address this challenge with complex and heavy actuators, often with limited practical application.

Therefore, the need for innovative solutions has sparked a growing interest in equipping EMAs with prognostics and health management (PHM). This strategy aims to enhance diagnostic, prognostic, and health management procedures, with early fault detection being paramount in flight-critical scenarios. This innovative approach seeks to prevent safety-critical situations by mitigating the risk of jamming in EMAs, thus enhancing their reliability and safety in primary flight control applications.

Nevertheless, developing a PHM system for EMAs is challenging due to their intricate nature, encompassing electronic, electrical, and mechanical subsystems. Moreover, EMAs are typically under-instrumented, making it challenging to detect and isolate faults, particularly when dealing with a limited set of signals.

In this framework, a high-fidelity model of an EMA represents a valuable tool supporting the exploration of various parameters and degradation effects on measurable signals under different operating conditions, serving as a virtual test bench to study various degradations on the different subcomponents in a fast and cost-effective way.

This paper focuses on the development of a multi-physics dynamic non-linear mathematical model of an EMA for secondary flight control actuators, built on a brushless electric motor, a reducer, and a ball screw to convert the rotational motion into a linear displacement. Particular attention was paid to the high-fidelity representation of the physical phenomena involved in the electric motor and ball screw subcomponents. The motor is modeled as a three-phase synchronous motor supplied by a six-legged inverter. Each component is physically represented to provide a robust and accurate representation of its expected behavior.

The single-nut not preloaded ball screw system has been represented with a multibody dynamic approach, taking into account the full dynamics of each subcomponent and their mutual interactions. The motion of each sphere uniquely depends on the instantaneous contact conditions, thoroughly described by a dedicated 3D contact model with the screw shaft and nut gothic arch grooves considering the presence of grease lubrication.

The combination of these two detailed models was exploited to investigate the effect of a nut groove surface superficial defect on easily measurable quantities available for EMAs, such as kinematic signals. The results confirmed the detectability of such a degradation with already available signals, by means of the analysis of the Hilbert spectrum and the variance of the Implicit Mode Functions obtained by the Empirical Mode Decomposition.

The proposed model allows a better understanding of the physics underlying the EMA and to investigate a wide range of operative scenarios and possible failures, while the outcomes of the proposed research demonstrated the feasibility of ball screw localized defect detection, fostering the applicability of PHM routines to support the EMAs integration onboard.

Presenting Author: Antonio Carlo Bertolino Politecnico di Torino

Presenting Author Biography: Antonio Carlo Bertolino, born in Cagliari (Italy) in 1992, earned his Mechanical Engineering degree from Politecnico di Torino in 2016, followed by a Ph.D. in Mechanical Engineering in 2020. Currently serving as an Assistant Professor in Applied Mechanics at Politecnico di Torino, his research specializes in high-fidelity PHM-oriented dynamic modeling of electro-hydraulic, electromechanical and hybrid actuators for flight control systems in both fixed and rotary-wing aircraft, with particular emphasis on ball screw dynamics. Antonio has collaborated on research and consulting projects with various industrial and aerospace companies.

Authors:

Antonio Carlo Bertolino Politecnico di Torino
Andrea De Martin Politecnico di Torino
Roberto Guida Politecnico di Torino
Gabriele Bencivinni Politecnico di Torino
Massimo Sorli Politecnico di Torino