Session: 01-03: Modeling and Simulation

Paper Number: 140246

140246 - Development of Boundary/Mixed Friction Models for Cylinder Block/Valve Plate Interface in a Novel Aerospace Electro-Hydrostatic Module 

Abstract: 

The growing trend towards electrification in the aerospace domain has significantly elevated the prominence and preference of Electro-Hydrostatic Actuation (EHA) systems over conventional Hydraulic Actuation Systems (HSA), particularly evident in applications such as aircraft flight control systems and thrust vector control (TVC) systems. The pivotal power component influencing EHA output performance is the Electro-Hydrostatic Module (EHM), typically composed of a servo motor unit, a hydraulic pump unit, and a Power Drive Electronics (PDE) module. Traditional EHM structures feature independent pumps and motors connected through a coupling, introducing misalignment errors between the motor and pump rotors, and increasing the overall axial dimensions. This research focuses on a novel EHM design, where the motor and pump are integrated into a single housing, sharing a common rotor and removing the couplers and dynamic seals. This integration significantly improves dynamic response characteristics, reliability, and power ratio.

However, research on this novel Electro-Hydrostatic Actuator (EHM) is still in the exploratory phase, with its dynamic and static characteristics unclear, and a lack of established theoretical modeling methods. Investigating its operational mechanisms is a challenging yet intriguing task. As the largest contact friction pair, the cylinder block/valve plate interface significantly determine the performance of the EHM. In this innovative EHM, the flow field characteristics under the shared casing condition are more intricate compared to a single hydraulic pump. Additionally, compared to a separate rotor, the integrated rotor in this novel EHM exhibits significant changes in its dynamic characteristics. These factors collectively have a substantial impact on the working characteristics of the friction interface, necessitating the development of a model considering the boundary/mixed friction characteristics to investigate its operational behavior. Previous modeling approaches have primarily focused on the internal conditions of hydraulic pump itself, which are not directly applicable to this shared casing structure. Therefore, it is necessary to develop a friction characteristics model specific to this novel EHM by comprehensively considering variations in operating conditions.

The simplification inherent in traditional Hertz theory regarding the microstructures (particles, grooves, pores, etc.) at the contact surface makes it challenging to accurately characterize the frictional state at the interface. To enhance the model's accuracy, this study applies Persson contact mechanics theory to the theoretical modeling process of the friction characteristics. Leveraging measurements from a 3D laser microscope, the microstructures in the contact region of the friction pair are characterized and modeled. Parameters related to the microstructures on the cylinder/valve plate pair surfaces (thickness, roughness, hardness, elastic modulus, etc.) are incorporated into the contact mechanics model. Furthermore, based on Reynolds lubrication theory, the viscous friction characteristics in the non-contact region are characterized, thereby constructing a boundary/mixed friction model for the working surface. Subsequently, through the development of a fluid model under shared housing conditions and a dynamic model for the integrated rotor, the churning effects of the motor rotor and cylinder block, as well as the transient response of the rotor under high-frequency reversing conditions, are introduced as boundary conditions to the friction characteristics model of the cylinder/valve plate pair. This aims to simulate the actual operating conditions inside the novel structure. Through simulation analysis, the impact patterns of various operating parameters on friction characteristics are examined, providing data support for subsequent experimental comparative studies and theoretical guidance for the structural optimization design of the new EHM.

Presenting Author: Dingchong Lyu Beihang University

Presenting Author Biography: Lyu Dingchong is a current doctoral student at Beihang University. His primary research focuses on the structural design, the theory of multi-field fine modeling, and the friction/lubrication characteristics of critical friction pairs of the power components of electro-hydrostatic actuation system (EHA). He has published some achievements in his research field, with his most recent article titled "Experimental Research on Friction Characteristics of DLC Coated Cylinder Block/Valve Plate Interface in Aerospace Integrated Motor Pumps," presented at the APISAT 2023 conference.

Authors:

Dingchong Lyu Beihang University
Jian Fu Beihang University
Shoujun Zhao Beijing Research Institute of Precise Mechatronic Controls
Siyuan Chen Beihang University