Electro-hydrostatic Actuator Research Articles

Thermal Characteristic and Analysis of Electro-Hydrostatic Actuator

Thermal Characteristic and Analysis of Electro-Hydrostatic Actuator

BOEING 787 Model Daha Elektrikli Uçak Sistem Yenilikleri ve Araştırılan Sorunları

In recent years, MEA technology has brought about developments in the field of power electronics, fault-tolerant architecture, electro-hydrostatic actuators, flight control systems, high-density electric motors, power generation and conversion systems. Non-propulsive systems in traditional aircraft systems, ıt is powered by a combination of different secondary power sources such as hydraulic, pneumatic, mechanical and electrical while the more electric aircraft (MEA) concept ensures the use of optimum electrical power for all non-propellant systems. 
 The goal of future aircraft technology is to replace the majority of non-electrical power-using systems, such as environmental control and engine starting, with electrical systems to improve various aircraft characteristics such as efficiency, emissions, reliability and maintenance costs. B787 series aircraft, the first civil aircraft with more electric aircraft features of modern times, ıt features composite fuselage and wing profiles, fly-by-wire flight controls, advanced cockpit and General Electric or Rolls-Royce engines. Different from previous designs, Boeing has minimized the use of air from the engines in the B787 technology and makes extensive use of electrically powered systems instead of traditional pneumatically powered systems. B787 new generation passenger aircraft, ıt is anticipated that significant improvements such as aircraft weight, fuel consumption, total life cycle costs, carbon neutrality, ease of maintenance and aircraft reliability will reduce the effects of adverse environmental conditions.
 In this study, the system innovations of the B787 aircraft model, which is a more electric aircraft concept and introduces different testing and working methods throughout the design process, and the problems caused by the new systems were investigated.

Flow match and precision motion control of asymmetric electro-hydrostatic actuators with complex external force in four-quadrants

Asymmetric Electro-hydrostatic actuators (EHAs) have been widely applied in the aerospace and manufacturing industries owing to their small installation space. However, some challenges must be considered in precision control. First, a deficient or excess flow rate forms in the closed hydraulic circuit because of the different piston areas between the cap and rod sides of the asymmetric actuators. In addition, a complex external force, which is difficult to measure directly, always emerges and declines the control performance when EHAs are operated. In this study, a modified hydraulic circuit and an integrated flow-matching valve were developed to address the mismatched flow rate. Subsequently, a high-performance motion control scheme was proposed based on the extended state observer (ESO) and backstepping method. Within this controller, the forward dynamic compensation was designed in terms of the four-quadrant flow compensation model. Meanwhile, the nonlinear gain and updated law of compensations for observer error were synthesized to suppress tracking errors. Comparative experiments demonstrated the higher precision tracking performance of the proposed motion controller in all four quadrants.

Tolerance design guideline for piston/cylinder interface of electro-hydrostatic actuator (EHA) pumps based on a Thermal-Fluid-Structure model

Working under a wide range of conditions, especially extreme conditions, causes significant energy dissipation and thermal deformation that affect the micro-scale oil film clearances between the piston/cylinder interface of electro-hydrostatic actuator (EHA) pumps. This study aims to provide a tolerance design guideline for the piston/cylinder interface under a wide range of working conditions, including extreme speed, pressure, and temperature domains. The guideline is developed based on the comprehensive consideration of friction force and leakage and the constraint of sticking threshold through a Thermal-Fluid-Structure model. The optimized clearance is presented in the form of tolerance to account for realistic manufacturing precision. The accuracy of the optimal results is further validated through experiments.

Position control performance analysis of linear actuator in swashplate-controlled electro hydrostatic actuation system

The position control of an energy efficient electrohydraulic actuation system is a decisive characteristic of its performance. In position control applications, a servo valve and/or variable displacement pump are vital to control the position of the linear actuator. In this open-loop control experimental work, the position of a linear actuator having a stroke length of 0.2 m is controlled by a swashplate-controlled electro hydrostatic actuation system. LabVIEW is used to create the control algorithm, and the National Instrument compact-RIO controller is used to control the voltage supply. The National Instruments controller processes sinusoidal and square demand signals at frequencies of 1/16, 1/12, 1/8, and 1/4 Hz. Open-loop control performance is predominantly dependent on the appropriate tuning of the voltage supply. Control performance is evaluated using the parameters integrated absolute error, integrated square error, integrated time absolute error, and integrated time square error. In comparison to square demand, it has been found that sinusoidal demand offers better position control accuracy, and square demand also offers appropriate control accuracy only at lower frequencies (1/16 Hz).

Fault Mode Analysis and Convex Optimization-Based Fault-Tolerant Control for New Type Dissimilar Redundant Actuation System of Near Space Vehicle

A new type dissimilar redundant actuation system (NT-DRAS), which is composed of an electro-hydrostatic actuator (EHA) and an electro-mechanical actuator (EMA), is applied in high value unmanned aerial vehicles such as the future near space vehicles to improve their reliability and performance index simultaneously. Further improvement in the flight safety is achieved with the fault-tolerant control (FTC) technique which deals with system faults. This paper proposes a novel convex optimization-based fault-tolerant control (CO-FTC) strategy for the NT-DRAS subject to gradual faults which are included in the state space representation of the system. A convex analysis-based treatment for system uncertainty caused by gradual faults is applied to determine the control gain matrix. The existence condition of the control gain matrix is optimized in the linear matrix inequality (LMI) form. Finally, the determined subsystems based on the novel technique is used to solve the modeled robust FTC problem. Case studies of NT-DRAS subject to different gradual faults have been accomplished to illustrate the FTC necessity for NT-DRAS. Furthermore, the effectiveness of the proposed CO-FTC strategy is validated by comparative analysis of the simulation results.

Development of compact revolute electro-hydrostatic actuator module and evaluation of its backdrivability and internal leakage

Actuators of a robot that physically interacts with objects or human require backdrivability to obtain force controllability, impact resistance and compactness. An electro-hydrostatic actuator (EHA) is a servo pump type hydraulic system that has a potential to satisfy backdrivability. However, the previous mechanical design of a revolute EHA did not achieve compact design compared to the other actuators. The hydraulic pump and vane motor were separately located, which made the size of EHA system larger. To solve this problem, we propose a design methodology of a revolute EHA using a frameless motor. Commercially available frameless motor is suitable for actuating the hydraulic pump. Moreover, the pump can be built in the hollow space of the frameless motor, and this design makes the EHA downsized. We present a prototype design based on the formulation of the output power. Through the experimental validations, we show that developed EHA has higher backdrivability than the comparable harmonic drive, and obtain the knowledges on design factors that are crucial to the EHA with high power-to-weight ratio.

An Improved Robust Model Predictive Speed Control With Inertia Identification for PMSM Drives in the Electrohydrostatic Actuator

An Improved Robust Model Predictive Speed Control With Inertia Identification for PMSM Drives in the Electrohydrostatic Actuator

Optimal Design of Motor–Pump Parameters for Direct Load-Sensitive EHA Based on Multi-Objective Optimization Algorithm

The electro-hydrostatic actuator (EHA) is a highly integrated and reliable actuation system which has been widely used in aerospace and construction machinery. In addition, the direct load sensitive EHA (DLS–EHA) has been investigated by introducing load-sensitive techniques which can well match the system output and external loads. More importantly, the matching design of motor–pump parameters is an important stage in the pre-design phase of DLS–EHA. For this reason, a multi-objective optimization design method for DLS–EHA motor–pump parameters is proposed in this paper. Firstly, the motor–pump mass and energy loss models are constructed based on similarity criteria. Secondly, the multi-objective particle swarm optimization algorithm (MOPSO) is used to optimize the design of the motor-pump parameters, and the Pareto frontier solutions of the optimized parameters are obtained. Further, the optimal design parameters are selected on the basis of meeting the actual requirements. Finally, the DLS–EHA prototype is designed based on the optimized design parameters and experimental verification is completed. The results of the study show that the optimized design parameters can meet the design requirements. The design method proposed in this paper provides an important theoretical basis for the optimized design of DLS–EHA.

Extended Sliding Mode Observer-Based Output Feedback Control for Motion Tracking of Electro-Hydrostatic Actuators

This paper develops a novel output feedback control scheme for the motion-tracking problem of an electro-hydrostatic actuator (EHA) in the presence of model uncertainties and external disturbances. Firstly, a simplified third-order system model of the studied EHA is established using theoretical methods. For the first time, an extended sliding mode observer (ESMO) is introduced to simultaneously account for the shortage of unknown system states and modeling imperfections. Based on this, a robust nonlinear controller is developed using the backstepping control framework to stabilize the closed-loop system. This controller integrates estimates of immeasurable system states and lumped disturbances to deal with their adverse impacts. Moreover, the dynamic surface control (DSC) technique is employed to effectively mitigate the computational burden of the traditional backstepping framework. An ultimately uniformly bounded (UUB) performance is assured by using the recommended method. Furthermore, the stability of not only the observer but also the closed-loop system is concretely analyzed by using the Lyapunov theory. Finally, experiment results under various working scenarios are given to convincingly demonstrate the advantage of the suggested method in comparison with some reference control approaches.

A Robust Model-Based Strategy for Real-Time Fault Detection and Diagnosis in an Electro-Hydraulic Actuator Using Updated Interactive Multiple Model Smooth Variable Structure Filter

Abstract In industries where harsh environments and stringent safety requirements are prevalent, the widespread use of applications has made it essential to focus on fault detection and diagnosis (FDD) in hydraulic actuators. To achieve this, model-based FDD techniques are utilized, which employ estimation tools like observers and filters. However, for many applications, particularly in fluid power systems, observability, and parameter uncertainty pose constraints to extracting information and estimating parameters. To address these issues, an efficient form of interactive multiple model (IMM), called updated IMM (UIMM), is applied to an electro-hydraulic actuator (EHA) to detect and isolate persisting friction and leakage faults. UIMM method progresses through a series of models that correspond to the fault condition's progression instead of considering all models at once (as is done in IMM). This reduces the number of models running simultaneously, providing two significant benefits: enhanced computational efficiency and avoidance of the combinatorial explosion. The smooth variable structure filter with variable boundary layer (SVSF-VBL) is used for state and parameter estimation in conjunction with UIMM. SVSF-VBL is a reliable suboptimal estimation method that performs better than the Kalman filter regarding uncertainties related to the system and modeling. The performance of the UIMM method is validated by the simulation of fault conditions for a typical EHA. A fault tolerable control system (FTCS) has been designed to demonstrate the use of the proposed FDD strategy for fault management in a closed-loop system.

Mechanical efficiency of cartridge two-dimensional (2D) piston pump for electro-hydrostatic actuators

Mechanical efficiency of cartridge two-dimensional (2D) piston pump for electro-hydrostatic actuators

Design Optimization of Valve Plate of a Bi-directional Axial Piston Pump for Electro Hydrostatic Actuation Systems

Design Optimization of Valve Plate of a Bi-directional Axial Piston Pump for Electro Hydrostatic Actuation Systems

Dynamic Surface-Based Adaptive Active Disturbance Rejection Control of Electrohydrostatic Actuators

The control accuracy and stability of the electrohydrostatic actuator (EHA) are directly impacted by parameter uncertainty, disturbance uncertainty, and non-matching disturbance, which negatively impacts aircraft rudder maneuvering performance and even results in rudder chatter. A dynamic surface-based adaptive active disturbance rejection control (DSAADRC) is proposed as a solution for these issues. It does this by developing a novel parametric adaptive law driven by the combination of tracking error, parameter estimation error, and state estimation error to estimate the unknown parameters, using three low-order ESOs to estimate and compensate the uncertain disturbances online, and employing a dynamic surface method to obtain the differential values of virtual control signals in the backstepping method to deal with non-matching disturbances. In this research, a Lyapunov stability analysis demonstrates that the method can achieve the position tracking accuracy of the EHA under time-varying external disturbances after first establishing an EHA dynamics model with nonlinearity and uncertainty, followed by the design of an adaptive active disturbance rejection control method based on dynamic surfaces for the uncertainties and perturbations. In contrast to control strategies like Robust Control (RC) and Adaptive Robust Control (ARC), simulation and experiment comparison shows that the method has stronger anti-disturbance under time-varying external disturbances.

Multi-Objective Optimization of a Novel Ribbed Honeycomb Heat Sink for an Electro-Hydrostatic Actuator

The electro-hydrostatic actuator (EHA) is a new type of power-by-wire (PBW) actuation system, which is utilized to realize a more electric aircraft. However, EHA suffers from serious thermal problems, due to its high integration and high power density. Therefore, a reasonable heat dissipation structure is an essential method for solving this problem. In this paper, a novel ribbed honeycomb heat sink (RHCS) developed by combining a ribbed heat sink (RHS) with a honeycomb heat sink (HCS) is proposed. Moreover, the optimization of heat sink parameters was achieved by using a multi-objective particle swarm optimization algorithm (MOPSO). Initially, the thermal resistance and mass models of the HCS were constructed, based on which the optimal structural parameters of the honeycomb cell were obtained. In addition, the thermal resistance model of RHCS was constructed using the response surface method, and parameters such as rib spacing, height and width were obtained based on MOPSO. Finally, the heat dissipation capability of RHCS was verified using both a simulation and experimental methods, and the results show that the heat dissipation capability of RHCS is about 15%∼20% higher than that of RHS and 7.4%∼10.3% higher than that of HCS. The configuration and design method of RHCS proposed in this paper provide a solution for the thermal design of EHA.

Methodology for Preliminary Flight Control Actuator Design

In this paper, a methodology for the preliminary design of decentralized civil-use flight control actuators is presented that is able to perform the calculations with a very small amount of input data. This enables the user to achieve good actuator key characteristics regarding the weight, power, and volume in the preliminary aircraft design stage without the need for an empirical database. Optionally adjustable setting parameters of the individual components allow the component design to be customized in detail. Both electromechanical and electrohydrostatic actuators are considered. The methodology presented here aims at sizing each individual component of the actuators in terms of volume, mass, and power consumption. The components are broken down into simple geometric shapes where possible. The methodology is evaluated on several actuators of different performance and weight classes from 3.2 kg up to 66.9 kg and provides more accurate results than other common approaches, which is suitable in the preliminary aircraft design stage.

Tribological characteristics of hard-to-hard matching materials of cylinder block/valve plate interface in electro-hydrostatic actuator pumps

Axial piston pumps, serving as the essential power component in electro-hydrostatic actuators (EHA), play a crucial role in achieving advanced actuation by ensuring high efficiency and reliability. The cylinder block/valve plate interface, which is the greatest contact area inside the axial piston pump, significantly affects both leakage and energy dissipation. The interface experiences significant friction loss and severe wear in aerospace applications, primarily due to the rapidly changing mixed and boundary lubrication conditions under a wide range of speed and pressure. Therefore, to improve the efficiency and reliability of electro-hydrostatic actuators, strengthening the cylinder block/valve plate interface is a key problem to overcome. Previous studies have demonstrated that the utilization of soft-to-hard matching materials enhances the friction characteristics of the interface, but it also results in relatively severe wear on the soft material. Therefore, in this study, we propose the concept of employing hard-to-hard matching materials as a strategy to mitigate wear in axial piston pumps. An optimized friction simulation test apparatus is adopted, which contains a simulated piston structure to take the piston stirring effect into consideration. Experimental results show that the implementation of hard-to-hard materials leads to a substantial improvement in the wear resistance of the interface under a wide range of rotational speed (300–6000 rpm). The wear depths of the TiAlN/TiAlN (hard-to-hard) matching material are only 28.6%~34.7% of the tin bronze/TiAlN (soft-to-hard) matching material. Besides, compared with traditional tin bronze/nitrided (soft-to-hard) matching material, the hard-to-hard matching materials improve both friction and wear performance. The hard-to-hard matching materials provide a novel approach to reinforce the cylinder block/valve plate interface, and thus to promote volumetric efficiency and extend the service life of the axial piston pump.

A method to detect internal leakage of hydraulic cylinder by combining data augmentation and multiscale residual CNN

AbstractDeveloping a method to detect internal leakage in hydraulic cylinder, which is used for Electro‐Hydrostatic Actuators (EHA), is important to prevent serious malfunctions for aircrafts. At present, the internal leakage in an EHA cannot be accurately detected only using operational data. This paper proposed a convolutional neural networks (CNN) based method to detect internal leakage in hydraulic cylinder according to the relationship between operational state parameters of EHA and leakage in the hydraulic cylinder. A method was presented to align multi‐source signals with different forms by using the motor current as a benchmark. Because the number of monitoring signals are relatively small, a feedforward neural network (FFNN) based data augment method is proposed to increase parameters of input data set. A general method on how to detect internal leakage by combining signals alignment, data augmentation and multiscale residual CNN was proposed. The experimental results show that the proposed method can be used to accurately detect internal leakage in a hydraulic cylinder operating under non‐stationary load and velocity conditions, and the detection accuracy reached 99.8%.

An online data-driven approach for performance prediction of electro-hydrostatic actuator with thermal-hydraulic modeling

An online data-driven approach for performance prediction of electro-hydrostatic actuator with thermal-hydraulic modeling

MODERN AIRCRAFT BRAKING SYSTEMS

This paper presents some problems concerning the present trends in the field of aircraft braking systems. New solutions like electro-mechanical or electro-hydrostatic actuators are considered the future, but some big aircraft producers do not renounce yet to classical electro-hydraulic braking systems. New solutions are not generally accepted, they have to prove their reliability and that they bring considerable more advantages than penalties.