Servo Valve Research Articles

Enhanced robust control based on ESO for high-pressure electro-pneumatic servo valve with strong anti-disturbance performance

Enhanced robust control based on ESO for high-pressure electro-pneumatic servo valve with strong anti-disturbance performance

Analysis of contamination and jamming characteristics of fuel metering device based on OMEGA theory

In order to obtain the quantitative law of the influence of pollution particles in fuel on the working characteristics of fuel metering devices and explore an analytical method for the pollution sticking characteristics of non-standard fuel components, the effect of pollution particles on fuel components is converted into sticking force based on the OMEGA theory, and the dynamic model of fuel components and devices under fuel pollution conditions is established. The working characteristics of the fuel metering device when the solid contamination level is GJB450B-7/8/9 is simulated, and the influence of each grade of fuel on the performance of its key components is obtained. The results show that the load flow response obtained by the servo valve contamination sticking model is basically consistent with the results of the standard servo valve contamination sticking model. The maximum sticking force of the metering valve in the 9-grade fuel is about 140 N, the response time is more than twice that of the non-polluting state, and the maximum relative error of the metered fuel quantity increases by more than 4 times. The method proposed in this paper can provide a reference for the pollution sticking modeling of non-standard fuel components and systems.

Orifice erosion effect and variable gain control method for hydraulic servo spool valve

The hydraulic servo valve orifice becomes blunted due to erosion caused by solid particle contaminants in the oil, leading to a decline in the valve's static and dynamic performance. This study analyzes the working edge scanning model and proposes using a quarter-ellipse curve to fit the working edge contour for the precise calculation of the valve orifice area. Through AMESim simulation, this study investigates the relationship between valve orifice erosion and the static and dynamic characteristics of hydraulic servo slide valves and proposes a variable gain control method for addressing valve orifice erosion. Results show that the orifice area model based on the quarter elliptic curve is accurate. As erosion increases, the nonlinear area of the valve orifice curve expands, and the valve orifice degrades into a positive opening. The ratio of the long diameter to the short diameter of the ellipse is approximately linearly related to the pressure gain and leakage in the static characteristics of the hydraulic servo valve. After variable gain control, the static and dynamic characteristics of the servo valve closely resemble those of an ideal servo valve, with the maximum deviation between the flow characteristics and the ideal valve orifice approximately 1 %. Regarding pressure characteristics, the pressure drop before the zero position is below 0.2 MPa. This study establishes the internal relationship between orifice erosion and performance degradation and provides a novel approach to enhancing the erosion resistance of hydraulic servo valves.

Mathematical Modeling of an Armature Assembly in a Flapper–Nozzle Servo Valve Based on the Finite Element Method

Mathematical Modeling of an Armature Assembly in a Flapper–Nozzle Servo Valve Based on the Finite Element Method

Mathematical modeling and experimental investigation of pressure characteristics inside the pilot stage of the deflector jet servo valve considering secondary jet velocity distribution

Mathematical modeling and experimental investigation of pressure characteristics inside the pilot stage of the deflector jet servo valve considering secondary jet velocity distribution

Detecting Anomalies in Hydraulically Adjusted Servomotors Based on a Multi-Scale One-Dimensional Residual Neural Network and GA-SVDD

A high-pressure hydraulically adjusted servomotor is an electromechanical–hydraulic integrated system centered on a servo valve that plays a crucial role in ensuring the safe and stable operation of steam turbines. To address the issues of difficult fault diagnoses and the low maintenance efficiency of adjusted hydraulic servomotors, this study proposes a model for detecting abnormalities of hydraulically adjusted servomotors. This model uses a multi-scale one-dimensional residual neural network (M1D_ResNet) for feature extraction and a genetic algorithm (GA)-optimized support vector data description (SVDD). Firstly, the multi-scale features of the vibration signals of the hydraulically adjusted servomotor were extracted and fused using one-dimensional convolutional blocks with three different scales to construct a multi-scale one-dimensional residual neural network binary classification model capable of recognizing normal and abnormal states. Then, this model was used as a feature extractor to create a feature set of normal data. Finally, an abnormal detection model for the hydraulically adjusted servomotor was constructed by optimizing the support vector data domain based on this feature set using a genetic algorithm. The proposed method was experimentally validated on a hydraulically adjusted servomotor dataset. The results showed that, compared with the traditional single-scale one-dimensional residual neural network, the multi-scale feature vectors fused by the multi-scale one-dimensional convolutional neural network contained richer state-sensitive information, effectively improving the performance of detecting abnormalities in the hydraulically adjusted servomotor.

Characteristic Progress and New Solutions for Nozzle Baffle Type Electro-Hydraulic Servo Valve

Background: This article outlines the working principle of the nozzle baffle type electro- hydraulic servo valve and analyzes the progress of research on its characteristics more fully. Objective: Firstly, it summarizes the research progress on the characteristics of the cavitation phenomenon, which is a common failure of nozzle baffle type electro-hydraulic servo valves; secondly, it comprehensively discusses the structural characteristics of nozzle baffle type electrohydraulic servo valves: moving-iron torque motors and moving-coil torque motors, as well as the progress of the research on the characteristics of the power-stage valve spools and direct-injection valve spools. Method: It suggests to the readers other optimization methods that can be made for the cavitation phenomenon in the future, and brings innovative ideas for the readers in terms of moving-iron vs. moving-coil torque motors and other aspects that can be improved for the power-stage spools vs. direct-injection spools. Again, for the typical technical problems of nozzle baffle type electrohydraulic servo valves, we have searched and organized the related technical patents at home and abroad and clearly outlined the current improvements for nozzle baffle type electro-hydraulic servo valves. Results: Through the discussion of related articles and patents, it is found that although many methods have been proposed at home and abroad to address the shortcomings of the nozzle baffle type electro-hydraulic servo valve, it still has a high failure rate and has not been comprehensively solved, there is still a lot of room for optimization. Conclusion: Finally, the new solutions proposed for the performance deficiencies of nozzle baffle type electro-hydraulic servo valves are summarized, and the future development trend of nozzle baffle type electro-hydraulic servo valves is predicted and outlooked.

Research on thermodynamic modeling and temperature prediction of double flapper-nozzle servo valves

The thermal characteristic design of the aerospace servo valve is of significant importance due to the high temperature operating conditions. This paper aims to study the law of temperature variation of the internal chambers and shell of the servo valve while it is driven dynamically, in order to ensure that the components inside the servo valve work within an acceptable temperature range and avoid failure. This paper establishes thermodynamic models of the nozzle flapper assembly and the spool valve, as well as the whole servo valve, using the control volume method. The models consider the throttling heating generation of each throttling component in the servo valve and heat exchange between the shell and air. Based on these models, the temperature curves of the shell and oil in each chamber in the servo valve are simulated and analyzed, given a specified input signal. Finally, a test is conducted, and the results demonstrate that the temperature curve trend obtained through simulation and test is reasonable and more accurately reflects the internal temperature characteristics of servo valves. This research provides a reference for further studies on the internal heating mechanism of servo valves and the fault diagnosis of servo valves at high temperatures.

Mathematical modeling and time-frequency characterization of aero-engine actuators

The actuator is an essential part of the aero-engine control system, and its performance directly determines the efficiency of the whole system. The mathematical model of the aero-engine actuators, including electro-hydraulic servo valves, hydraulic cylinders, and actuators, is modeled and the time-frequency characteristics are analyzed using the Simulink module. Then, the system response is simulated and its time-frequency characteristics are analyzed. The simulation results show that the simulation error of the established actuator model is within the allowable range. The displacement response and the servo valve flow response fluctuate slightly near the steady state value, and the error value is only 0.857% at the maximum fluctuation value, and the system still works normally when a dynamic load is added to the system.

Research of closed loop characteristics of single and double chamber structure for fuel metering mechanism

There are two forms of engine fuel metering devices which are single and double chamber structures using electro-hydraulic servo valves as electro-hydraulic conversion devices to realize accurate fuel flow measurements and constant pressure differential valve is used to maintain the constant pressure difference of the metering valve. The main purpose of this article is to analyze the time domain and frequency domain characteristics of constant pressure differential valve assembly and compare the closed-loop characteristics of two metering mechanisms. Firstly, the mathematical model of constant pressure differential valve assembly (including the fuel pump and constant pressure differential valve) is established and its time and frequency domain characteristics are analyzed. The conclusion that the constant pressure differential of the metering valve can meet the practical requirements is obtained. Secondly, the mathematical models of single and double-chamber fuel metering mechanisms are established considering the specific working conditions. Finally, the characteristics of two kinds of metering mechanisms are compared and analyzed under the same control method in the time and frequency domain. The extension overshoot with a maximum value of 3.564% of the single chamber control metering valve mechanism is smaller than that of the double chamber control metering valve mechanism with a maximum extension overshoot of 6.04%. The negative overshoot with a maximum value of 1.391% of the single chamber control metering valve mechanism is bigger than the double chamber control metering valve mechanism with a maximum negative overshoot value of 1.17%. In terms of steady-state error, the steady-state error of a single chamber control metering valve mechanism with a maximum value of 0.194 mm and minimum value of 1.25e-6 mm is smaller than that maximum value of 0.302 mm and minimum value of 1.95e-6 mm of double chamber control metering valve mechanism under the same controller parameters. The bandwidth of the extension motion of the single and double chamber control metering valve is greater than that of the retraction motion. Under the same proportional control parameter, the bandwidth of the double chamber control metering valve extension motion system is greater than that of the single chamber extension motion system.

Model reference sliding mode control for two-degree-of-freedom electro-hydraulic shaking table

The multi-axis electro-hydraulic shaking table (EHST) is capable of simulating complex vibration environments to assess product reliability under vibrational excitation. The random vibration control method plays a crucial role in simulating these environments. However, the unmolded disturbances and the nonlinearity of the system have a significant impact on the control accuracy of the EHST. Sliding mode control (SMC) can be used in single-input single-output electro-hydraulic servo systems (EHSS) to attenuate the influence of disturbance forces. The conventional SMC is not suitable for acceleration random vibration control of the multi-axis EHST because the coupling between the axes and the actuators and the null bias of the servo valve are not taken into account. A model reference sliding mode control (MRSMC) is presented in this paper based on the nonlinear dynamic model of the EHST. The MRSMC designed based on the backstepping method and Lyapunov theory is used to compensate for the disturbance forces and the null bias of the servo valve. Experimental acceleration random vibration responses show that the MRSMC enhances the accuracy of tracking the acceleration random signal.

Research on Electro-hydraulic Servo Valve Structure and Control Algorithm of System with Servo Valve

Background: With the continuous progress of electronic information technology, people have begun to study the combination of electronic information technology and hydraulic technology to achieve more accurate and flexible control. Electro-hydraulic servo technology was thus developed. Much attanetion has been paid to electro-hydraulic servo valve,a key component of electrohydraulic servo technology. Objective: The number of stages of the electro-hydraulic servo valve, the structure form of the electro- hydraulic servo valve hydraulic front stage, the feedback form of the electro-hydraulic servo valve, the output form of electro-hydraulic servo valve, and the control algorithm based on the application of electro-hydraulic servo valve are analyzed and commented respectively. Combined with associated patents, the research direction and hot topics of electro-hydraulic servo valves are analyzed. Method: The electro-hydraulic servo valves were briefly classified; and then the problems of different types of valves were discussed in depth. Results: By analyzing the problems of electro-hydraulic servo valves, the problems of how to improve the control accuracy, response speed, anti-interference ability, service life and cost reduction of electro-hydraulic servo valves are analyzed comprehensively, and the future development prospect of electro-hydraulic servo valves is predicted and outlooked. Conclusion: Analyzing and discussing the existing hot issues of electro-hydraulic servo valves helps to update and change the electro-hydraulic servo valves, and makes corresponding references for the subsequent research of electro-hydraulic servo valves.

Chattering analysis of an electro-hydraulic backstepping velocity controller

This paper focuses on the chattering analysis in a backstepping controller used to drive an electro-hydraulic servo system. The chattering phenomenon, well known in sliding mode control, strongly reduces operating performance while causing premature wear of the system. Four cases are studied to highlight the factors influencing the chattering in the backstepping control. In the first case, the effect of the unmodeled fast servo valve dynamics is analysed by comparing a reduced-order backstepping controller with a full-order controller. The second case analyses the sensitivity to the tuning gains of the backstepping controller. The third case emphasises the influence of the parameter of sign function approximation. The last case analyses the sensitivity of the parameter of the time derivative of the virtual controls. The simulation results in the Matlab/Simulink show that the chattering is mitigated by an appropriate gains tuning but above all an appropriate calculation of the derivatives of the virtual controls, particularly for high-order systems.

Automated Digital Wind Instrument using Arduino UNO Microcontroller

Recently, Blackstar Amplification Ltd. has introduced a Compact Carry-On Digital Wind Instrument (CDWI), mirroring the design of traditional recorder instruments in their size and shape. This CDWI can be played as a traditional wind instrument by blowing into the mouthpiece and simultaneously manipulating finger holes, enabling the production of desired musical notes. The main aim of this research work is the development of a prototype model to automate the CDWI, by utilizing the Arduino UNO microcontroller board and introducing the Automated Digital Wind Instrument (ADWI). The CDWI has a mouthpiece, nine finger holes, and one thumb hole, and the blowing mechanism can be automated by using a 12 Volts DC air blower and a servo valve. The author ingeniously develops a new servo valve using a plastic syringe, a ball, and a 5 Volts DC micro servo motor to regulate the air pressure blown into the mouthpiece. The ADWI fingers are meticulously crafted using plastic pen barrels, thrust tubes, and metallic springs to simulate the actions of a human music player's fingers. Positioned to maintain all finger holes in an open state by default, the selective closing of specific holes is achieved by ten micro servo motors to produce a specific musical note. In a preliminary test, the ADWI prototype is programmed to perform the Nursery Rhyme "Twinkle, Twinkle, Little Star." While evaluating the sound output by hearing, it is evident that the proposed ADWI effectively generates all the necessary musical notes. However, the noise generated by the air blower and micro servo motors introduces interference, impacting the clarity of the produced musical notes. Consequently, it is planned to integrate a noise reduction mechanism as part of future work.

The modeling and analysis of operating characteristics and temperature drift of deflector jet servo valve under the wide temperature range

The Deflector Jet Servo Valve (DJSV) holds a crucial role within the electro-hydraulic servo system, as its performance directly influences the equipment reliability. DJSV operates within a wide temperature range, and the temperature fluctuations result in the magnetomotive force variations of the permanent magnets and changes in the working air gaps, which influence the operating characteristics of the torque motor and contribute to temperature drift. Consequently, a theoretical model is proposed to comprehensively analyze the impact of these factors on the operating characteristics and temperature drift of the DJSV. The results indicate that as the temperature increases, the magnetic flux of working air gap decreases, while the temperature drift increases. Additionally, among the five initial air gap errors discussed, a centrosymmetric error of less than 0.02 l can significantly reduce the temperature drift. The proposed modeling and analysis method of temperature drift can be used to guide the design and analysis of DJSV in wide temperature range.

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).

Active fault-tolerant control for the dual-valve hydraulic system with unknown dead-zone

This paper proposes a method for high-performance motion control of the dual-valve hydraulic system subject to parameter and model uncertainties, unknown proportional valve dead-zone, and servo valve fault. By constructing a detailed dual-valve fault system model (DFSM), a disturbance observer-based adaptive robust fault-tolerant controller is proposed via the backstepping method. This controller integrates a model-based fault detection algorithm for real-time fault monitoring and subsequent controller reconfiguration. Additionally, the DFSM-based adaptive robust control (ARC) technique is applied to handle the unknown dead-zone problem and other nonlinearities, ensuring precise control. Once the servo valve fault occurs, a nonlinear observer estimates the fault and collaborates with the ARC to establish a reconfigured controller, thereby maintaining motion control. The effectiveness of the proposed method has been experimentally verified.

Servo kontrollü maliyet etkin bir aktif kuvvet duyargası tasarımı ve denenmesi

In this work, the computerized control of a hydraulic system with analog characteristics is examined, and within this scope, a novel force sensor is designed. The system consists of two main structures: an analog subsystem comprising a four-way servo valve, hydraulic piston, servo amplifier, and the designed force sensor, and a digitizing subsystem responsible for comparison and control, composed of a desktop computer. Throughout this work, a cost-effective force sensor was designed by integrating a compression spring, guides, a support frame and a linear variable differential transformer (LVDT). In this integrated system, the force applied at a specific magnitude and frequency from an external force measurement and feedback unit is converted into electrical signals by horizontal motion of the LVDT core. These electrical signals from the force sensor are digitized and fed back to the computer and data acquisition card. The digitized data transferred to the software developed in this study continuously compare with the reference data, enabling position-dependent force control. Experiments conducted with the force sensor placed between two hydraulic pistons controlled by a servo valve revealed that it caused the pistons to move right and left, providing the desired control of the system with the reference force input. The system was observed to operate much more stably, especially for high-frequency signal inputs.

Vibration suppression of an armature assembly in hydraulic servo valve based on distributed parameters mathematical models

As a commonly used hydraulic control component, the nozzle-flapper servo valve has the advantages of small structure and sensitive dynamic response. Due to the small size and complex structure of the servo valve, the classical control methods based on various feedback information cannot effectively improve its performance. In order to effectively improve the performance of the servo valve, this paper implemented the feedforward control method to suppress the dynamic performance of the armature assembly of the servo valve. The distributed parameters mathematical models of the armature assembly are established and verified which can accurately predict the vibration of the armature assembly. With the mathematical model, the feedforward control signal is calculated based on the real-time velocity, acceleration, and deflection of the armature assembly, respectively. The applicability of different signals is analyzed and the signals calculated by velocity and deflection are verified which can effectively suppress the vibration amplitude of armature assembly. The numerical simulation and experimental methods are implemented to verify the performance of different control signals and the optimal feedforward control signal under different external loads is obtained.

Modeling and Fault Simulation of a New Double-Redundancy Electro-Hydraulic Servo Valve Based on AMESim

The feedback spring rod of the armature assembly was eliminated in the double-redundancy electro-hydraulic servo valve (DREHSV), which employed a redundant design in contrast to the typical double-nozzle flapper electro-hydraulic servo valve (DNFEHSV). The pilot stage was mainly composed of four torque motors, and the double-system spool was adopted in the power stage. Consequently, the difficulty of spool displacement control was increased. By artificially changing the structural parameters of the simulation model in accordance with the theoretical analysis through AMESim, this paper aimed to study the dynamics and static characteristics of the DREHSV. The advantage of redundant design was further demonstrated by disconnecting working coils and setting the different worn parts of the spool. On the test bench, the necessary experiments were performed. Through simulation, it was discovered that when the clogged degree of the nozzle is increased, the zero bias value increases, the pressure and flow gain remain unchanged, and the internal leakage decreases. The pressure gain changes very little, the flow gain close to the zero position grows, the zero leakage increases significantly, and the pilot stage leakage changes very little as a result of the wear of the spool throttling edge. The basic consistency between the simulation curves and the experimental findings serve to validate the accuracy of the AMESim model. The findings can serve as a theoretical guide for the design, debugging, and maintenance of the DREHSV. The simulation model is also capable of producing a large amount of sample data for DREHSV fault diagnosis using a neural network.