Investigation on the ball screws no-load drag torque in presence of lubrication through MBD simulations

Born from environmental and cost saving concerns, the recent trend toward more electric aircraft has touched most of the more important on-board systems and equipment [1?3] . For flight control devices, this tendency translated into several and still concurring effort s to replace the traditional electro-hydraulic configuration (EHSAs) with electro-mechanical actuators (EMAs) for primary and secondary aerodynamic surfaces [4?7] , a technology already widely spread in several fields, such as the manufacturing industry [8] . EMAs theoretically provide several advantages over the hydraulic solution in terms of envelope, weight, environment The no-load drag torque is a crucial factor in the design phase to estimate the power required by the electric motor in electro-mechanical actuators (EMA). This paper focuses on the analysis of the drag torque contribution generated in preloaded double nut ball screws of EMAs. In literature its value is commonly estimated with a linear relationship with respect to the preload level. However, many other parameters play a role in determining the friction torque, such as operating speed, temperature and geometry. A sensitivity analysis on these parameters is presented by means of simulation results obtained from a highfidelity multibody dynamic (MBD) model, capable of describing the full three-dimensional dynamics of each subcomponent and the presence of full film, mixed or boundary lubrication between mating elements. The results have been interpreted with a physics-based approach highlighting a strong dependency of the drag torque on temperature basing on the lubricant?s viscosity. This parameter also influences the drag torque speed dependence, which resulted to be more pronounced for low operating temperatures. An experimental test bench is being constructed to validate the model results. ? 2021 Elsevier Ltd. All rights reserved.

Automated summary

The trend towards more electric aircraft, mainly driven by environmental and cost saving concerns, has led to increased efforts to replace traditional electro-hydraulic configurations with electro-mechanical actuators for flight control. This shift has theoretical advantages in terms of weight and environmental impact. The paper focuses on analyzing drag torque contributions in preloaded double nut ball screws of EMAs, highlighting the strong dependency of drag torque on temperature and lubricant viscosity.