The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator（LEHA）. Rather than the traditional statistical methods based on degradation d...The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator（LEHA）. Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics（CFD） method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves（EHSVs）, throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process.展开更多
With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling an...With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling and mode switching analysis of EHA used in the primary flight control actuation systems of large aircraft,addressing the challenges associated with mode switching.First,we analyze the functional architecture and operational characteristics of multi-mode EHA,and sumarize the operating modes and implementation methods.Based on the EHA system architecture,we then develop a theoretical mathematical model and a simulation model.Using the simulation model,we analyze the performance of the EHA during normal operation.Finally,the performance of the EHA during mode switching under various functional switching scenarios is investigated.The results indicate that the EHA meets the performance requirements in terms of accuracy,bandwidth,and load capacity.Additionally,the hydraulic cylinder operates smoothly during the EHA mode switching,and the response time for switching between different modes is less than the specified threshold.These findings validate the system performance of multi-mode EHA,which helps to improve the reliability of EHA and the safety of aircraft flight control systems.展开更多
The variable pump displacement and variable motor speed electro-hydrostatic actuator(EHA),one of the three types of EHAs,has advantages such as short response time,flexible speed regulation,and high efficiency.However...The variable pump displacement and variable motor speed electro-hydrostatic actuator(EHA),one of the three types of EHAs,has advantages such as short response time,flexible speed regulation,and high efficiency.However,the nonlinearity of its double-input single-output system poses a great challenge for system control.This study proposes a novel EHA with adaptive pump displacement and variable motor speed(EHA-APVM).A closed-loop position is realized using a servomotor.Moreover,the displacement varies with the system pressure;thus,the EHA-APVM is a single-input and single-output system.Firstly,the working principles of the EHA-APVM and the pump used in the system are introduced.Secondly,a nonlinear mathematical model of the proposed EHA-APVM control system is established,and a feedback back-stepping(FBBS)control algorithm is introduced to transform the complex nonlinear system into a linear system on the basis of the back-stepping control theory.Finally,simulation results prove that the EHA-APVM has a quick response and high robustness to variations of the load and the pump displacement.In this work,the size and weight of the motor are significantly reduced because the maximum power requirement is reduced,which is very beneficial for using the actuator in airborne equipment.展开更多
The speed of an Electro-Hydrostatic Actuator(EHA) pump can recently reach 20000 r/min, and its churning losses increase obviously with an increasing speed, which results in low efficiency and thus increasing heat in a...The speed of an Electro-Hydrostatic Actuator(EHA) pump can recently reach 20000 r/min, and its churning losses increase obviously with an increasing speed, which results in low efficiency and thus increasing heat in aircraft EHA systems. In order to reduce churning losses at high speeds, more attention should be given to the design of an insert. In this paper, the effect of an insert with different design parameters on churning losses is investigated through Computational Fluid Dynamics(CFD) simulation and experiments by calculating the difference between churning losses torques of the test pump with and without the insert based on a high-speed churning losses test rig.Analytical results show that the gap between the insert and the cylinder is critical for churning losses reduction. It is found that the churning losses of the test pump can be reduced with a decreasing gap between the cylinder block and the insert at high speeds. This is because the insert can decrease the turbulence occurrence at high speeds. The results can be used for flow field analysis and optimization of the high-speed EHA pump and provide a new method for improving efficiency of high-speed EHA pumps.展开更多
The electro-hydrostatic actuator （EHA） is a kind of power-by-wire （PBW） actuator that converts the electrical power into localized hydraulic power for flight control. By removing the central hydraulic power supply...The electro-hydrostatic actuator （EHA） is a kind of power-by-wire （PBW） actuator that converts the electrical power into localized hydraulic power for flight control. By removing the central hydraulic power supply together with hydraulic pipes, an EHA＇s reliability and efficiency are greatly improved but its frequency width and stiffness decreased. To overcome the drawback, this article proposes a novel structure of EHA associated with a power regulator. Composed of a high-pressure accumulator and a proportional valve, it can store and harness the hydraulic power flexibly according to the changing control requirements. The concept of transferred volume is put forward to estimate the capability of the power regulator. The actuator output position can be kept fixed with a hydraulic lock. The compounded control is specially developed to ensure the actuator system to operate in a correct manner. The simulation results indicate that the new-brand actuator results in efficient expanding of the system frequency width with an optimal power supply.展开更多
The integrated electro-hydrostatic actuator （EHA） with variable displacement and variable rotation speed is researched. In the system, the output of the actuator is changed by controlling the rotationspeed of the br...The integrated electro-hydrostatic actuator （EHA） with variable displacement and variable rotation speed is researched. In the system, the output of the actuator is changed by controlling the rotationspeed of the brushless DC servomotor and the displacement of the servopump. The mathematical model described in state-space model is created. The system characteristics are studied based on the point of multiplicative dual-variable. And the basic method of control of the system is presented.展开更多
This paper presents a novel transient lubrication model for the analysis of the variable load failure mechanism of high-speed pump used in Load Sensing Electro-Hydrostatic Actuator（LS-EHA）. Focusing on the slipper/s...This paper presents a novel transient lubrication model for the analysis of the variable load failure mechanism of high-speed pump used in Load Sensing Electro-Hydrostatic Actuator（LS-EHA）. Focusing on the slipper/swashplate pair partial abrasion, which is considered as the dominant failure mode in the high-speed condition, slipper dynamic models are established. A forth sliding motion of the slipper on the swashplate surface is presented under the fact that the slipper center of mass will rotate around the center of piston ball when the swashplate angle is dynamically adjusted. Besides, extra inertial tilting moments will be produced for the slipper based on the theorem on translation of force, which will increase rapidly when LS-EHA pump operates under highspeed condition. Then, a dynamic lubricating model coupling with fluid film thickness field, temperature field and pressure field is proposed. The deformation effects caused by thermal deflection and hydrostatic pressure are considered. A numerical simulation model is established to validate the effectiveness and accuracy of the proposed model. Finally, based on the load spectrum of aircraft flight profile, the variable load conditions and the oil film characteristics are analyzed, and series of variable load rules of oil film thickness with variable speed/variable pressure/variable displacement are concluded.展开更多
The electro-hydrostatic actuator(EHA)used in more electric aircraft(MEA)has been extensively studied due to its advantages of high reliability and high integration.However,this high integration results in a small heat...The electro-hydrostatic actuator(EHA)used in more electric aircraft(MEA)has been extensively studied due to its advantages of high reliability and high integration.However,this high integration results in a small heat dissipation area,leading to high-temperature problems.Generally,to reduce the temperature,a wet cooling method of using the pump leakage oil to cool the motor is adopted,which can also increase the difficulty of accurately predicting the system temperature in the early design stage.To solve this problem,a dynamic coupling thermal model of a wet EHA is proposed in this paper.In particular,the leakage oil of the pump is used as a coupling item between the electrical system and the hydraulic system.Then,an improved T-equivalent block model is proposed to address the uneven distribution of axial oil temperature inside the motor,and the control node method is applied to hydraulic system thermal modeling.Meanwhile,a dynamic coupling thermal model is developed that enables a dynamic evaluation of the wet EHA temperature.Then,experimental prototypes of wet motor and wet EHA are developed,while the temperature response of the wet motor at different rotation speeds and different loads and the temperature response of the wet EHA at no-load condition were verified experimentally at room temperature,respectively.The maximum temperature difference between the experimental and theoretical results of the wet motor as well as the experimental and theoretical results of the wet EHA is less than 8℃.These test results indicate that the dynamic coupling thermal model is valid and demonstrate that the thermal coupling modeling method proposed in this paper can provide a basis for the detailed thermal design of EHA.展开更多
To improve the power density and simplify the seal structure,the Wet-Type Permanent Magnet Synchronous Motor(WTPMSM)technique has been applied to aerospace Electro-Hydrostatic Actuators(EHA).In a WTPMSM,the stator and...To improve the power density and simplify the seal structure,the Wet-Type Permanent Magnet Synchronous Motor(WTPMSM)technique has been applied to aerospace Electro-Hydrostatic Actuators(EHA).In a WTPMSM,the stator and the rotor are both immersed in the aviation hydraulic oil.Although the heat dissipation performance of the WTPMSM can be enhanced,the aviation hydraulic oil will cost an extra oil frictional loss in the narrow airgap of the WTPMSM.This paper proposes an accurate oil frictional loss model for the WTPMSM,in which the wide speed range(0–20 kr/min)and the narrowness of the airgap(0.5–1.5 mm)are its features.Firstly,the mechanism of the oil frictional loss in the airgap of the WTPMSM is revealed.Then an accurate oil frictional loss model is proposed considering the nonlinear influence caused by the Taylor vortex.Furthermore,the influence of motor dimensions on oil frictional loss is analyzed.Finally,the proposed oil frictional loss model is verified by experiments,which provides a guideline for engineers to follow in the WTPMSM design.展开更多
This study proposes an accurate dead zone compensation control method for electro-hydrostatic actuators(EHAs)under low-speed conditions.Specifically,the nonlinear dead zone characteristics under low-speed conditions a...This study proposes an accurate dead zone compensation control method for electro-hydrostatic actuators(EHAs)under low-speed conditions.Specifically,the nonlinear dead zone characteristics under low-speed conditions are summarized based on numerous EHA experiments.An adaptive compensation function(ACF)is then constructed for the dead zone.Next,this study proposes an adaptive dead zone compensation control method for EHAs by integrating the ACF with a virtual decomposition controller(VDC)based on the established EHA model.The stability of the proposed control method is also proven.Finally,the proposed control method is verified using an EHA platform.The test results show that the dead zone trajectory tracking errors of EHAs are significantly reduced when combined with the ACF.Furthermore,since most EHAs are controlled by adjusting the motor speed,the method presented in this study is simpler and easier to use than methods that employ flow compensation.展开更多
The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the ...The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.展开更多
This paper studies the problem of designing adaptive fault-tolerant controllers for linear tirne-invariant systems with actuator saturation. New methods for designing indirect adaptive fault-tolerant controllers via s...This paper studies the problem of designing adaptive fault-tolerant controllers for linear tirne-invariant systems with actuator saturation. New methods for designing indirect adaptive fault-tolerant controllers via state feedback are presented for actuator fault compensations. Based on the on-line estimation of eventual faults, the adaptive fault-tolerant controller parameters are updating automatically to compensate the fault effects on systems. The designs are developed in the framework of linear matrix inequality （LMI） approach, which can enlarge the domain of attraction of closed-loop systems in the cases of actuator saturation and actuator failures. Two examples are given to illustrate the effectiveness of the design method.展开更多
In this paper,stability of discrete-time linear systems subject to actuator saturation is analyzed by combining the saturation-dependent Lyapunov function method with Finsler’s lemma.New stability test conditions are...In this paper,stability of discrete-time linear systems subject to actuator saturation is analyzed by combining the saturation-dependent Lyapunov function method with Finsler’s lemma.New stability test conditions are proposed in the enlarged space containing both the state and its time difference which allow extra degree of freedom and lead to less conservative estimation of the domain of attraction.Furthermore,based on this result,a useful lemma and an iterative LMI-based optimization algorithm are also developed to maximize an estimation of domain of attraction.A numerical example illustrates the effectiveness of the proposed methods.展开更多
This paper studies the problem of designing adaptive fault-tolerant H-infinity controllers for linear timeinvariant systems with actuator saturation. The disturbance tolerance ability of the closed-loop system is meas...This paper studies the problem of designing adaptive fault-tolerant H-infinity controllers for linear timeinvariant systems with actuator saturation. The disturbance tolerance ability of the closed-loop system is measured by an optimal index. The notion of an adaptive H-infinity performance index is proposed to describe the disturbance attenuation performances of closed-loop systems. New methods for designing indirect adaptive fault-tolerant controllers via state feedback are presented for actuator fault compensations. Based on the on-line estimation of eventual faults, the adaptive fault-tolerant controller parameters are updated automatically to compensate for the fault effects on systems. The designs are developed in the framework of the linear matrix inequality （LMI） approach, which can guarantee the disturbance tolerance ability and adaptive H-infinity performances of closed-loop systems in the cases of actuator saturation and actuator failures. An example is given to illustrate the efficiency of the design method.展开更多
A synthesis method for global stability and performance of input constrained linear systems, which uses a linear outputfeedback controller and a static anti-windup compensator is investigated. Different from the tradi...A synthesis method for global stability and performance of input constrained linear systems, which uses a linear outputfeedback controller and a static anti-windup compensator is investigated. Different from the traditional two-step anti-windup design procedure, the proposed method synthesizes all controller parameters simultaneously. Sufficient conditions for global stability and minimizing the induced L2 gain are formulated and solved as a linear matrix inequalities（LMIs） optimization problem, which also provides an opportunity to search for a better performance tradeoff between the linear controller and the anti-windup compensator.The well-posedness of the close-loop system is also guaranteed.Simulation results show the effectiveness of the proposed method.展开更多
This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite elem...This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite element method,taking into account the nonlinear characterization and the eddy current loss of the magnetic material. The experiment and simulation results agree well and show that the prototype actuator can produce a force of ±100 N with the maximum power being 7 W and has linear characteristics with a positive magnetic stiffness within a stroke of ±1 mm. Its non-linearity is less than 1.5% and the hysteresis less than 1.5%. The actuator's frequency response(-3 dB) of the displacement reaches about 15 Hz,and the most significant factor affecting the dynamic performance is identified as the eddy current loss of the magnetic material.展开更多
This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using...This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using gear rotary actuators. Starting with a rhombus linkage, with a linear actuator on the diagonal used for the elevation motion till 90°, a new performance solution is generated. This new linkage allows large angular strokes by using an asymmetric rhombus and an eccentrically positioned linear actuator. The paper can be divided in three main parts. Firstly the kinematical modeling of the new linkage is addressed, which permits the establishing of the linkage dimensions according to two adjustable parameters （k2, k5）. Using the resulted correlations, in the second part the linkage synthesis algorithm is developed; the steps followed in this algorithm are presented in a numerical application considering a tracked PV platform, where the azimuthal vertical movement is obtained with the new proposed rhomboidal linkage. In the last part of the paper an analysis is done with the aim of determining the PV platform tracking efficiency （which represents the ratio between the received and the available beam solar energy） using the new linkage, in the meteorological conditions of Brasov, Romania implementation site.展开更多
Linear electromagnetic actuators(LEAs) are widely used in tokamaks,but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field(SMF),which is usually a concomitant with tokamaks.In...Linear electromagnetic actuators(LEAs) are widely used in tokamaks,but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field(SMF),which is usually a concomitant with tokamaks.In this paper,a multi-physics coupling analysis model of LEA,including magnetic field,electric circuit and mechanical motion,is proposed,and the dynamic characteristics of LEAs in SMFs are studied in detail based on the proposed model.The failure mechanism of LEAs in SMFs is revealed,and the influence of SMFs on the dynamic performance of LEAs is studied and quantified.It is shown that the failure threshold of the LEA selected in this work under the rated condition is 27 mT and 14 mT in the positive and negative direction,respectively.Under a typical SMF of 10 mT in the negative direction,the closing time of the LEA will be extended by 40%,while its opening time will be shortened by about 10%.Experimental tests are also conducted,which verify the validity of the proposed model and the analysis results.This paper provides a basis for the diamagnetic optimization design of LEA,and it is of great significance to ensure the reliable operation of the tokamak.展开更多
Reluctance linear actuator, which has a unique property of small volume, low current and can produce great force, is a very promising actuator for the fine stage of the next-generation lithographic scanner. But the st...Reluctance linear actuator, which has a unique property of small volume, low current and can produce great force, is a very promising actuator for the fine stage of the next-generation lithographic scanner. But the strong nonlinearities including the hysteresis, between the current and output force limits the reluctance linear actuator applications in nanometer positioning. In this paper, a new nonlinear control method is proposed for the stage having paired reluctance linear actuator with hysteresis using the direct adaptive neural network, which is used as a learning machine of nonlinearity. The feature of this method lies in that the nonlinear compensator in conventional methods, which computed the current reference from that of the input and output force is not used. This naturally overcomes the robustness issue with respect to parameter uncertainty. Simulation results show that the proposed method is effective in overcoming the nonlinearity between the input current and output force and promising in precision stage control.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51620105010,51675019,51575019)the National Basic Research Program of China(No.2014CB046402)the Program 111 of China
文摘The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator（LEHA）. Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics（CFD） method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves（EHSVs）, throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process.
基金supported by the Chinese Civil Aircraft Project(No.MJ-2017-S49).
文摘With the advancement of more electric aircraft(MEA)technology,the application of electro-hydrostatic actuators(EHAs)in aircraft actuation systems has become increasingly prevalent.This paper focuses on the modeling and mode switching analysis of EHA used in the primary flight control actuation systems of large aircraft,addressing the challenges associated with mode switching.First,we analyze the functional architecture and operational characteristics of multi-mode EHA,and sumarize the operating modes and implementation methods.Based on the EHA system architecture,we then develop a theoretical mathematical model and a simulation model.Using the simulation model,we analyze the performance of the EHA during normal operation.Finally,the performance of the EHA during mode switching under various functional switching scenarios is investigated.The results indicate that the EHA meets the performance requirements in terms of accuracy,bandwidth,and load capacity.Additionally,the hydraulic cylinder operates smoothly during the EHA mode switching,and the response time for switching between different modes is less than the specified threshold.These findings validate the system performance of multi-mode EHA,which helps to improve the reliability of EHA and the safety of aircraft flight control systems.
基金financially supported by the National Natural Science Foundation of China(No’s.51375029 and 51775013).
文摘The variable pump displacement and variable motor speed electro-hydrostatic actuator(EHA),one of the three types of EHAs,has advantages such as short response time,flexible speed regulation,and high efficiency.However,the nonlinearity of its double-input single-output system poses a great challenge for system control.This study proposes a novel EHA with adaptive pump displacement and variable motor speed(EHA-APVM).A closed-loop position is realized using a servomotor.Moreover,the displacement varies with the system pressure;thus,the EHA-APVM is a single-input and single-output system.Firstly,the working principles of the EHA-APVM and the pump used in the system are introduced.Secondly,a nonlinear mathematical model of the proposed EHA-APVM control system is established,and a feedback back-stepping(FBBS)control algorithm is introduced to transform the complex nonlinear system into a linear system on the basis of the back-stepping control theory.Finally,simulation results prove that the EHA-APVM has a quick response and high robustness to variations of the load and the pump displacement.In this work,the size and weight of the motor are significantly reduced because the maximum power requirement is reduced,which is very beneficial for using the actuator in airborne equipment.
基金financial supports from the National Basic Research Program of China(973 Program)(No.2014CB046403)the National Natural Science Foundation of China(No.1737110)
文摘The speed of an Electro-Hydrostatic Actuator(EHA) pump can recently reach 20000 r/min, and its churning losses increase obviously with an increasing speed, which results in low efficiency and thus increasing heat in aircraft EHA systems. In order to reduce churning losses at high speeds, more attention should be given to the design of an insert. In this paper, the effect of an insert with different design parameters on churning losses is investigated through Computational Fluid Dynamics(CFD) simulation and experiments by calculating the difference between churning losses torques of the test pump with and without the insert based on a high-speed churning losses test rig.Analytical results show that the gap between the insert and the cylinder is critical for churning losses reduction. It is found that the churning losses of the test pump can be reduced with a decreasing gap between the cylinder block and the insert at high speeds. This is because the insert can decrease the turbulence occurrence at high speeds. The results can be used for flow field analysis and optimization of the high-speed EHA pump and provide a new method for improving efficiency of high-speed EHA pumps.
基金National Natural Science Foundation for Distinguished Young Scholars of China （50825502）
文摘The electro-hydrostatic actuator （EHA） is a kind of power-by-wire （PBW） actuator that converts the electrical power into localized hydraulic power for flight control. By removing the central hydraulic power supply together with hydraulic pipes, an EHA＇s reliability and efficiency are greatly improved but its frequency width and stiffness decreased. To overcome the drawback, this article proposes a novel structure of EHA associated with a power regulator. Composed of a high-pressure accumulator and a proportional valve, it can store and harness the hydraulic power flexibly according to the changing control requirements. The concept of transferred volume is put forward to estimate the capability of the power regulator. The actuator output position can be kept fixed with a hydraulic lock. The compounded control is specially developed to ensure the actuator system to operate in a correct manner. The simulation results indicate that the new-brand actuator results in efficient expanding of the system frequency width with an optimal power supply.
文摘The integrated electro-hydrostatic actuator （EHA） with variable displacement and variable rotation speed is researched. In the system, the output of the actuator is changed by controlling the rotationspeed of the brushless DC servomotor and the displacement of the servopump. The mathematical model described in state-space model is created. The system characteristics are studied based on the point of multiplicative dual-variable. And the basic method of control of the system is presented.
基金supported by the National Natural Science Foundation of China(Nos.51620105010,51675019 and 51575019)the National Basic Research Program of China(No.2014CB046402)+1 种基金the ‘‘111" Projectthe Excellence Foundation of BUAA for PhD Students
文摘This paper presents a novel transient lubrication model for the analysis of the variable load failure mechanism of high-speed pump used in Load Sensing Electro-Hydrostatic Actuator（LS-EHA）. Focusing on the slipper/swashplate pair partial abrasion, which is considered as the dominant failure mode in the high-speed condition, slipper dynamic models are established. A forth sliding motion of the slipper on the swashplate surface is presented under the fact that the slipper center of mass will rotate around the center of piston ball when the swashplate angle is dynamically adjusted. Besides, extra inertial tilting moments will be produced for the slipper based on the theorem on translation of force, which will increase rapidly when LS-EHA pump operates under highspeed condition. Then, a dynamic lubricating model coupling with fluid film thickness field, temperature field and pressure field is proposed. The deformation effects caused by thermal deflection and hydrostatic pressure are considered. A numerical simulation model is established to validate the effectiveness and accuracy of the proposed model. Finally, based on the load spectrum of aircraft flight profile, the variable load conditions and the oil film characteristics are analyzed, and series of variable load rules of oil film thickness with variable speed/variable pressure/variable displacement are concluded.
基金co-supported by the National Natural Science Foundation of China (No. 51890882)National Key Research and Development Program of China (No. 2018YFB2000702)
文摘The electro-hydrostatic actuator(EHA)used in more electric aircraft(MEA)has been extensively studied due to its advantages of high reliability and high integration.However,this high integration results in a small heat dissipation area,leading to high-temperature problems.Generally,to reduce the temperature,a wet cooling method of using the pump leakage oil to cool the motor is adopted,which can also increase the difficulty of accurately predicting the system temperature in the early design stage.To solve this problem,a dynamic coupling thermal model of a wet EHA is proposed in this paper.In particular,the leakage oil of the pump is used as a coupling item between the electrical system and the hydraulic system.Then,an improved T-equivalent block model is proposed to address the uneven distribution of axial oil temperature inside the motor,and the control node method is applied to hydraulic system thermal modeling.Meanwhile,a dynamic coupling thermal model is developed that enables a dynamic evaluation of the wet EHA temperature.Then,experimental prototypes of wet motor and wet EHA are developed,while the temperature response of the wet motor at different rotation speeds and different loads and the temperature response of the wet EHA at no-load condition were verified experimentally at room temperature,respectively.The maximum temperature difference between the experimental and theoretical results of the wet motor as well as the experimental and theoretical results of the wet EHA is less than 8℃.These test results indicate that the dynamic coupling thermal model is valid and demonstrate that the thermal coupling modeling method proposed in this paper can provide a basis for the detailed thermal design of EHA.
基金This work was supported in part by National Natural Science Foundation of China(Nos.52177028 and U2141226)in part by Major Program of the National Natural Science Foundation of China(No.51890882)in part by Aeronautical Science Foundation of China(No.201907051002).
文摘To improve the power density and simplify the seal structure,the Wet-Type Permanent Magnet Synchronous Motor(WTPMSM)technique has been applied to aerospace Electro-Hydrostatic Actuators(EHA).In a WTPMSM,the stator and the rotor are both immersed in the aviation hydraulic oil.Although the heat dissipation performance of the WTPMSM can be enhanced,the aviation hydraulic oil will cost an extra oil frictional loss in the narrow airgap of the WTPMSM.This paper proposes an accurate oil frictional loss model for the WTPMSM,in which the wide speed range(0–20 kr/min)and the narrowness of the airgap(0.5–1.5 mm)are its features.Firstly,the mechanism of the oil frictional loss in the airgap of the WTPMSM is revealed.Then an accurate oil frictional loss model is proposed considering the nonlinear influence caused by the Taylor vortex.Furthermore,the influence of motor dimensions on oil frictional loss is analyzed.Finally,the proposed oil frictional loss model is verified by experiments,which provides a guideline for engineers to follow in the WTPMSM design.
基金Supported by National Natural Science Foundation of China(Grant Nos.51890883,U2141209)1912 Project Foundation。
文摘This study proposes an accurate dead zone compensation control method for electro-hydrostatic actuators(EHAs)under low-speed conditions.Specifically,the nonlinear dead zone characteristics under low-speed conditions are summarized based on numerous EHA experiments.An adaptive compensation function(ACF)is then constructed for the dead zone.Next,this study proposes an adaptive dead zone compensation control method for EHAs by integrating the ACF with a virtual decomposition controller(VDC)based on the established EHA model.The stability of the proposed control method is also proven.Finally,the proposed control method is verified using an EHA platform.The test results show that the dead zone trajectory tracking errors of EHAs are significantly reduced when combined with the ACF.Furthermore,since most EHAs are controlled by adjusting the motor speed,the method presented in this study is simpler and easier to use than methods that employ flow compensation.
基金supported by the National Key R&D Program of China(No.2021YFB2011300)the National Natural Science Foundation of China(Nos.52275044,U2233212)。
文摘The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.
基金supported by National Natural Science Foundation of China(61403254,61374039,61203143)Shanghai Pujiang Program(13PJ1406300)+2 种基金Natural Science Foundation of Shanghai City(13ZR1428500)Innovation Program of Shanghai Municipal Education Commission(14YZ083)Hujiang Foundation of China(C14002,B1402/D1402)
基金supported by Program for New Century Excellent Talents in University (NCET-04-0283)the Funds for Creative Research Groups of China (No.60521003)+4 种基金Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0421)the State Key Program of National Natural Science of China (No.60534010)the Funds of National Science of China (No.60674021)the Funds of PhD program of MOE,China (No.20060145019)the 111 Project (B08015)
文摘This paper studies the problem of designing adaptive fault-tolerant controllers for linear tirne-invariant systems with actuator saturation. New methods for designing indirect adaptive fault-tolerant controllers via state feedback are presented for actuator fault compensations. Based on the on-line estimation of eventual faults, the adaptive fault-tolerant controller parameters are updating automatically to compensate the fault effects on systems. The designs are developed in the framework of linear matrix inequality （LMI） approach, which can enlarge the domain of attraction of closed-loop systems in the cases of actuator saturation and actuator failures. Two examples are given to illustrate the effectiveness of the design method.
基金supported by Program for New Century Excellent Talents in University(No.NCET-04-0283)the Funds for Creative Research Groups of China(No.60521003)+4 种基金Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0421)the State Key Programof National Natural Science of China(No.60534010)the Funds of National Science of China(No.60674021)the Funds of PhD program of MOE,China(No.20060145019)the 111 Project(No.B08015)
文摘In this paper,stability of discrete-time linear systems subject to actuator saturation is analyzed by combining the saturation-dependent Lyapunov function method with Finsler’s lemma.New stability test conditions are proposed in the enlarged space containing both the state and its time difference which allow extra degree of freedom and lead to less conservative estimation of the domain of attraction.Furthermore,based on this result,a useful lemma and an iterative LMI-based optimization algorithm are also developed to maximize an estimation of domain of attraction.A numerical example illustrates the effectiveness of the proposed methods.
基金partly supported by Program for New Century Excellent Talents in University (No.NCET-04-0283)the Funds for Creative Research Groups of China (No.60521003)+4 种基金Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0421)the State Key Program of National Natural Science of China (No.60534010)the Funds of National Science of China (No.60674021)the Funds of PhD program of MOE,China (No.20060145019)the 111 Project (No.B08015)
文摘This paper studies the problem of designing adaptive fault-tolerant H-infinity controllers for linear timeinvariant systems with actuator saturation. The disturbance tolerance ability of the closed-loop system is measured by an optimal index. The notion of an adaptive H-infinity performance index is proposed to describe the disturbance attenuation performances of closed-loop systems. New methods for designing indirect adaptive fault-tolerant controllers via state feedback are presented for actuator fault compensations. Based on the on-line estimation of eventual faults, the adaptive fault-tolerant controller parameters are updated automatically to compensate for the fault effects on systems. The designs are developed in the framework of the linear matrix inequality （LMI） approach, which can guarantee the disturbance tolerance ability and adaptive H-infinity performances of closed-loop systems in the cases of actuator saturation and actuator failures. An example is given to illustrate the efficiency of the design method.
基金supported by the National Natural Science Foundation of China(6107402761273083)
文摘A synthesis method for global stability and performance of input constrained linear systems, which uses a linear outputfeedback controller and a static anti-windup compensator is investigated. Different from the traditional two-step anti-windup design procedure, the proposed method synthesizes all controller parameters simultaneously. Sufficient conditions for global stability and minimizing the induced L2 gain are formulated and solved as a linear matrix inequalities（LMIs） optimization problem, which also provides an opportunity to search for a better performance tradeoff between the linear controller and the anti-windup compensator.The well-posedness of the close-loop system is also guaranteed.Simulation results show the effectiveness of the proposed method.
文摘This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite element method,taking into account the nonlinear characterization and the eddy current loss of the magnetic material. The experiment and simulation results agree well and show that the prototype actuator can produce a force of ±100 N with the maximum power being 7 W and has linear characteristics with a positive magnetic stiffness within a stroke of ±1 mm. Its non-linearity is less than 1.5% and the hysteresis less than 1.5%. The actuator's frequency response(-3 dB) of the displacement reaches about 15 Hz,and the most significant factor affecting the dynamic performance is identified as the eddy current loss of the magnetic material.
基金supported by the Sectoral Operational Programme Human Resources Development (SOP HRD)Post Doctoral School,financed from the European Social Fund and by the Romanian Government (Grant No. POSDRU/89/1.5/S/59323)
文摘This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using gear rotary actuators. Starting with a rhombus linkage, with a linear actuator on the diagonal used for the elevation motion till 90°, a new performance solution is generated. This new linkage allows large angular strokes by using an asymmetric rhombus and an eccentrically positioned linear actuator. The paper can be divided in three main parts. Firstly the kinematical modeling of the new linkage is addressed, which permits the establishing of the linkage dimensions according to two adjustable parameters （k2, k5）. Using the resulted correlations, in the second part the linkage synthesis algorithm is developed; the steps followed in this algorithm are presented in a numerical application considering a tracked PV platform, where the azimuthal vertical movement is obtained with the new proposed rhomboidal linkage. In the last part of the paper an analysis is done with the aim of determining the PV platform tracking efficiency （which represents the ratio between the received and the available beam solar energy） using the new linkage, in the meteorological conditions of Brasov, Romania implementation site.
基金supported in part by the National Key R&D Program of China (No.2017YFE0301800)in part by National Natural Science Foundation of China (No. 51821005)in part by the Comprehensive Research Facility for Fusion Technology Program of China (No.2018000052-73-01-001228)
文摘Linear electromagnetic actuators(LEAs) are widely used in tokamaks,but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field(SMF),which is usually a concomitant with tokamaks.In this paper,a multi-physics coupling analysis model of LEA,including magnetic field,electric circuit and mechanical motion,is proposed,and the dynamic characteristics of LEAs in SMFs are studied in detail based on the proposed model.The failure mechanism of LEAs in SMFs is revealed,and the influence of SMFs on the dynamic performance of LEAs is studied and quantified.It is shown that the failure threshold of the LEA selected in this work under the rated condition is 27 mT and 14 mT in the positive and negative direction,respectively.Under a typical SMF of 10 mT in the negative direction,the closing time of the LEA will be extended by 40%,while its opening time will be shortened by about 10%.Experimental tests are also conducted,which verify the validity of the proposed model and the analysis results.This paper provides a basis for the diamagnetic optimization design of LEA,and it is of great significance to ensure the reliable operation of the tokamak.
文摘Reluctance linear actuator, which has a unique property of small volume, low current and can produce great force, is a very promising actuator for the fine stage of the next-generation lithographic scanner. But the strong nonlinearities including the hysteresis, between the current and output force limits the reluctance linear actuator applications in nanometer positioning. In this paper, a new nonlinear control method is proposed for the stage having paired reluctance linear actuator with hysteresis using the direct adaptive neural network, which is used as a learning machine of nonlinearity. The feature of this method lies in that the nonlinear compensator in conventional methods, which computed the current reference from that of the input and output force is not used. This naturally overcomes the robustness issue with respect to parameter uncertainty. Simulation results show that the proposed method is effective in overcoming the nonlinearity between the input current and output force and promising in precision stage control.
