Hydraulic Valve Research Articles

Research on Hydraulic Servo Valve Control Based on Fuzzy RBF

Aiming at the problems of low control precision and slow response speed of traditional control of actuators in hydraulic systems, the mathematical model of the valve-controlled cylinder is established as the research object, and the control strategy of fuzzy RBF neural network is proposed to control hydraulic servo valves On the basis of traditional fuzzy control, fuzzy control and RBF neural network control are integrated. According to the mathematical model of the system, a tracking controller is designed to realize precise control and real-time feedback of the valve-controlled cylinder system. The simulation results show that compared with traditional PID and fuzzy PID systems, the fuzzy RBF neural network strategy has high control precision, fast response speed, better robustness, and stability.

Particle erosion transient process visualization and influencing factors of the hydraulic servo spool valve orifice

The erosion of the valve orifice can easily lead to the performance degradation of the hydraulic servo spool valve, which seriously affects the service life and reliability of the hydraulic servo system. In this paper, the erosion micro-morphological characteristics, erosive transient process visualization of solid particles, and factors affecting the erosion rate of the spool working edges were investigated. The results showed that there was a significant “edge collapse” phenomenon on the working edges of the spool, which was mainly characterized by surface peeling, notches, grooves, chamfers, and the radius of the fillet which fluctuated violently in the circumferential direction. The “smoothing, slipping, and somersaulting” evolution process started when the incident angle increased and the particles hit the valve orifice by a new visualization experiment model composed of the nozzle-baffle submerged jet. The erosion rate of the working edges also showed continuous fluctuations and violent changes, with strong scatter-like distribution characteristics. The erosion rate of the working edge in the up-flow field was approximately one time higher than that in the back-flow field. The erosion rate of the working edges increased as the oil viscosity and particle concentration increased. Under small openings, the impact frequency of particles and the working edge increased significantly. The distribution law of the erosion rate of the working edge agreed with the distribution characteristics of the erosion fillet radius of the working edges. The erosion rate variance was defined, which can be used to quantify the circular distribution of erosion rate. This study provides further understanding of the mechanism and influencing factors of the hydraulic servo spool valve erosion.

TURBINE SPEED CONTROL

Provides analysis of hydraulic turbine control systems existing in the world and domestic practice. The design features of constructing circuits with discrete and discrete-analog control methods are considered. The schemes for controlling the speed of the turbine of the leading manufacturers of hydraulic turbine equipment are given: PO "LMZ" and ALSTOM POWER HYDRO (France, Grenoble). The given computer system of hydraulic turbine speed control guarantees trouble-free operation in case of load deviation and power failures. A fully automatic method of controlling the hydraulic unit is possible, in which the computer system controls the turbine independently, based on the parameters of the hydraulic unit operation taken into account by the sensors, in accordance with the program of the control computer. The control system constantly monitors the operation of the hydraulic turbine, adjusts its speed according to the load, performs adequate control operations. The analysis of the operation of the circuits is carried out, taking into account the specifics of the functioning of the regulation system. A mathematical model of the hydromechanical part of the regulator is considered for assessing the quality indicators of transient processes occurring in the process of starting, stopping and reversing a hydraulic turbine. It is shown that the development of theory and design methods using both approaches, mathematical models and control algorithms aimed at increasing the positioning accuracy and reliability of hydropneumatic systems with a possible simplification of circuit solutions is an important task aimed at obtaining a significant economic effect when solving this most important problem. The results obtained prove that the use of a positional hydraulicpneumatic drive for building a hydraulic turbine speed control system with discrete and discrete-analogue control makes it possible to synthesize a hydraulic pneumatic drive with high positioning accuracy, without the use of expensive hydraulic valves with proportional control.

Design of an additively manufactured hydraulic directional spool valve: an industrial case study

ABSTRACT An industrial case study of an additively manufactured hydraulic spool valve that was designed in close collaboration with our industrial partner Wandfluh AG is presented herein. An existing conventional valve design was redesigned for laser powder bed fusion while considering the current functional and technical requirements. The entire development process is described based on real world requirements, considering the manufacturing and post-processing constraints. The final design was manufactured, tested, and compared with the conventionally manufactured valve. The pressure drop was reduced by 60% through the valve redesign, and a weight reduction of 50% was achieved. This study is concluded by reflecting the development process and identifying potential, learnings, and challenges that can be transferred to other hydraulic components. The importance of generating a large variety of concepts in the divergent design generation phase and performing computational fluid dynamics simulations to assess the potential of these concepts are highlighted.

ARTER: a walking excavator robot for autonomous and remote operations

Abstract The Autonomous Rough Terrain Excavator Robot (ARTER) is a retrofitted walking excavator developed for remote and autonomous operations in environments hostile to humans. This work highlights the key developments related to this robot: system design, terrain adaption controller, and high-level process controller. The original walking excavator is retrofitted with sensors, hydraulic valves, computation devices, etc., to automate it. The terrain adaption controller, which adapts the wheels automatically to the underlying uneven terrain, is implemented using deep reinforcement learning. The tasks for the robot are complex and require switching between autonomy and remote operations. Hence, a custom high-level process controller, based on behavior trees, which helps the operator control complex tasks for the robot, is developed. The remote control and autonomous behaviors of the robot are evaluated for realistic scenarios performed in a test environment.

Research on Electrochemical Controllable Machining Technology of Small-Sized Inner Intersecting Hole Rounding

Small-sized inner intersecting holes are a common structure for large engine nozzles, hydraulic valves, and other parts. In order to ensure the uniform and stable fluid state in the intersecting hole, it is necessary to process the fillet at the intersecting line and accurately control the fillet radius. Limited by the structure and size, the rounding of the small-sized inner intersecting hole is a technical problem, and the traditional machining methods have problems, in terms of efficiency and accuracy. In order to solve this problem, electrochemical machining technology was applied to the rounding of small-sized inner intersecting holes. According to the structure of inner intersecting holes, an electrochemical rounding processing scheme with built-in fixed cathode was designed. The electric field distribution of different cathode shapes was analyzed using finite element method software. The influence of processing voltage and processing time on the current density distribution was studied for different cathode shapes, to determine the most reasonable cathode shape. Taking the inner intersecting hole with a diameter of 2 mm as the research object, and according to the analysis of the influence of processing voltage on the processing effect, a suitable control factor for controlling the rounding was processing time, and the optimal processing voltage was obtained. The formulas of fillet radius and processing time were obtained by regression analysis and verified using machining examples. The results provide a feasible method for the accurate and controllable machining of small-sized inner intersecting hole rounding.

An indirect flow measurement based high-precision slide valve grinding mechanism for hydraulic servo valve

As a crucial power amplifying component for electro-hydraulic servo valves, the servo-valve spool valve largely determines the overall performance of an electro-hydraulic servo system. Due to the machining errors during the servo-valve manufacturing process, however, it is extremely difficult to characterize such response characteristics in engineering practice, and thus, there may exist certain nonlinearity between the flow rate and valve spool displacement caused by the spool and valve sleeve overlap. To accurately characterize the relationship between the flow rate and spool displacement to facilitate servo-valve production, an indirect flow measurement-based servo-valve spool valve grinding (FM-SVG) scheme is proposed in this study. Specifically, a valve spool overlap measurement mechanism is presented first based on the valve spool grinding principle, and then a data processing method is devised to eliminate the errors introduced by the fluctuations of differential pressure at the valve ports. Meanwhile, a closed-loop control system is also devised to maintain a constant differential pressure at the servo-valve ports. Finally, the FM-SVG scheme is embedded onto a lab-customized electro-hydraulic servo valve platform, and experiments are conducted to verify the feasibility and effectiveness of the FM-SVG scheme. Results show that, by utilizing the devised control scheme to maintain a differential pressure around 2.00 MP, the proposed grinding scheme helps achieve a grinding accuracy of 2.0 μm. With only grinding process needed, such a grinding scheme helps improve both grinding accuracy and production efficiency in practice.

Data-Based Flow Rate Prediction Models for Independent Metering Hydraulic Valve

Accurate valve flow rate prediction is essential for the flow control process of independent metering (IM) hydraulic valve. Traditional estimation methods are difficult to meet the high-precision requirements under the restricted space of the valve. Thus data-based flow rate prediction method for IM valve has been proposed in this study. We took the four-spool IM valve as the research object, and carried out the IM valve experiments to generate labeled data. Picking up the post-valve pressure and valve opening as input, we developed and compared eight different data-based estimation models, including machine learning and deep learning. The results indicated that the SVR and DNN with three hidden layers performed better than others on the whole dataset in the trade-off of overfitting and precision. And MAPE of these two models was close to 4%. This study provides further guidelines on high-precision flow rate prediction of hydraulic valves, and has definite application value for development of digital and intelligent hydraulic systems in construction machinery.

A Piezo-Electric Valve Actuator for Hydraulic Exoskeleton Drives

In many exoskeleton applications where heavy lifting is involved (e.g. in military or industrial applications) hydraulic actuators are used because of their high power density. For such applications it is necessary to develop compact and light hydraulic components so that the exoskeleton’s mass and size are low and, therefore, wearing comfort is high and power consumption is reduced to a minimum. Crucial components of hydraulic exoskeletons concerning this weight aspect are hydraulic valves and particularly their actuators, since conventional solenoids contribute the lion share of valve size and weight. As one option to solve this weight and size problem the application of smart materials such as piezo-ceramics to electrically actuate hydraulic valves are seen. The contribution at hand deals with the systematic design of a piezo-actuator which shall be used to switch a hydraulic valve. To overcome the problem of very low strain of the piezo a mechanism for amplification via a bistable buckling beam is analyzed analytically and numerically and an actuator prototype is designed and manufactured. This paper intends to carve out crucial challenges such as the requirements for snapping through of the buckling beam, the bearings of the beam and the integration of the piezo stack.

DEVELOPMENT AND APPLICATION OF THE DIGITAL TWIN OF THE HYDRAULIC CONTROL VALVE

The paper is focused on the development of the digital twin of the hydraulic control valve for continuous control of the oil flow – servovalve or control valve – and their use by the testing of the control system of the test rig for the measurement and evaluation of the characteristics of the valve. The structure of the mathematical model of the control valve enables to do the parameterisation for different types and sizes of the control valves only using the catalogue data delivered by the valve producers. In the next step the created and parameterized model is implemented into the dSpace MicroLabBox for the real time realisation of the digital twin. The MicroLabBox is equipped with the analogue inputs and outputs and allows the connection of the digital twin to the control system in the same way as the real servovalve. Finally, the characteristics of the valve are measured and evaluated using the HiL simulation of the digital twin. The digital twin of the servovalve allows the testing of the developed control system and software for the hydraulic test rig for the measurement of the valve characteristics without the need of the real valves different types.

Development Status and Research Progress of a Tractor Electro-Hydraulic Hitch System

A tractor electro-hydraulic hitch system is considered one of the most important systems that play a strategic role in the power transmission and operation depth control of a tractor’s field operation. Its performance directly affects the operation quality of the whole work unit of the tractor. Furthermore, a tractor electro-hydraulic hitch system has gained the interest of many in the agricultural machinery sector because of its stable performance, high production efficiency, good operation quality and its low energy consumption. To fully benefit from the potential of the tractor electro-hydraulic hitch system, it is significant to understand and address the problems and challenges associated with it. This study, therefore, aims to contribute to the development of the tractor electro-hydraulic hitch system by investigating the research methods, technical characteristics and emerging trends in three key aspects that include the tillage depth adjustment method, the tillage depth control algorithm and the core components of the electro-hydraulic hitch system. The characteristics and applicable conditions of the different tillage depth adjustment methods of the electro-hydraulic hitch system were summarized. The realization methods and the control characteristics of the different algorithms were elaborated and discussed for both the PID control algorithm and the intelligent control algorithm. The working characteristics of the core components of the electro-hydraulic hitch system were analyzed based on the hydraulic control valves and sensing elements. The results have shown that the multi-parameter tillage depth adjustment method met the operation quality standard while taking the engine load stability and traction efficiency into account, and it has a greater research significance and value. The working quality can be improved effectively by introducing the intelligent algorithm. In addition, the study of smart valves with built-in sensing elements and how to improve the anti-interference ability of sensing elements, are the aspects that requires further consideration. Aiming to improve the working quality and reduce energy consumption, further research into the tractor electro-hydraulic hitch system is necessary. The results of this comprehensive review provide a reference for the intelligent operation of tractors under the precision agriculture.

Accounting for Dilution of SARS-CoV-2 in Wastewater Samples Using Physico-Chemical Markers

Most sewer networks collect domestic wastewater and a variable proportion of extraneous water, such as rainwater, through surface runoff and industrial discharges. Accounting for wastewater dilution is essential to properly quantify wastewater particle loads, whether these are molecular fragments of SARS-CoV-2, or other substances of interest such as illicit drugs or microplastics. This paper presents a novel method for obtaining real-time estimates of wastewater dilution and total daily volume through wastewater treatment works, namely when flow data is not available or unreliable. The approach considers the levels of several physico-chemical markers (ammonia, electrical conductivity, and orthophosphate) in the wastewater against their dry-weather levels. Using high-resolution data from the national Wastewater Surveillance Programme of Wales, we illustrate how the method is robust to spikes in markers and can recover peaks in wastewater flow measurements that may have been capped by hydraulic relief valves. We show the method proves effective in normalising SARS-CoV-2 viral loads in wastewater samples and discuss other applications for this method, looking at wastewater surveillance as a vital tool to monitor both human and environmental health.

Effect of the balanced piston on the stability of hydraulic pilot-operated relief valve

The stability of a pilot-operated relief valve is investigated through mathematical modeling and experimental measurement. A comprehensive mathematical model of a cartridge-type pilot-operated relief valve is developed, which is designed with a balanced piston at the front of the pilot poppet. The dynamic behavior of such a valve was then investigated using a frequency-domain analysis method. The balanced piston was found to have a marked effect on the stability of the relief valve. The local stability of the valve under various annular clearances was further discussed by the normalization method. The results indicate that an appropriately sized balanced piston can improve the stability of the relief valve’s subsystem. However, when the annular clearance is large, the subsystem’s dynamic characteristics do not change obviously, although it does raise the pilot poppet damping ratio to some extent. Furthermore, numerical simulations and experimental studies were produced to validate the above conclusions, and excellent agreement between the measurement and the model was obtained.

New Hydraulic ‘Building Blocks’ System

AT bauma, Wandfluh is launching a game-changing, fully modular hydraulic valve range that is flexible enough to allow units with different flow rates to be combined

ИССЛЕДОВАНИЕ ГИДРАВЛИЧЕСКОГО ПРИВОДА КЛАПАНОВ ГРМ

Improving the characteristics of the internal combustion engine of an agricultural vehicle is possible by using a hydraulic actuator of the electronically controlled gas distribution valves. The drive ensures the opening of the engine valves by the pistons of the hydraulic cylinders when oil is pumped into them, the valves are closed using valve springs when the oil is drained from the hydraulic cylinders. The advantages of the hydraulic drive are: the ability to turn off the engine cylinders, an increase in the speed of opening and closing the valves of the gas distribution mechanism, no need to adjust the thermal clearances, a constant speed of the valves landing on the saddles. The hydraulic drive is integrated into the engine lubrication system. The working body of the hydraulic drive is engine oil with a pressure of 8 MPa, created by a separate pump. The physical and mathematical model of a hydraulic valve drive in the Simulink environment takes into account hydraulic pressure losses, various inertial effects, elastic-deformation interaction between drive elements, and inductance of solenoid valve coils. The experimental setup includes: a KAMAZ 740 engine, a hydraulic drive for two valves of one cylinder head, measuring equipment. The results of the experiments were recorded using a high-speed movie camera. The determination of the kinematic characteristics of the valves of the gas distribution mechanism was carried out by processing the video frames of the shooting at a known frequency of their fixation. The results of experiments coincide with the results of calculations. The speed of movement of the engine valves, thanks to the use of a hydraulic actuator, is significantly increased compared to the use of a traditional mechanical actuator. The time delay between the supply of an electrical signal to the electromagnetic valves and the response of the hydraulic drive to it is determined. The results obtained make it possible to start creating a serial hydraulic valve drive that improves engine parameters by intensifying and controlling the gas exchange of the engine cylinder with the environment

Analysis and Compensation Control of Engine Valve Response Delay Based on the Electro-Hydraulic Variable Valve Actuator

The time delay of variable valve actuators has a significant influence on engine valve lift tracking performance. For camless hydraulic valve actuators, engine valve response is affected by many factors, such as friction and control valve response. In this paper, engine valve response delay is investigated in depth. Experiment results show that engine valve motion delay can be divided into valve open delay and valve close delay. They are different even in the same engine cycle. Complicated delay characteristics make it difficult to build an accurate delay model. In this paper, a data-based delay observer is developed. To compensate the nonlinear valve delay, the virtual desired valve lift is designed. By synthesizing the virtual valve lift into the backstepping procedure, an engine valve lift tracking controller with delay compensation is developed. Compared with the P controller, the backstepping controller with delay compensation improved the engine valve lift tracking performance significantly. The experiment results show that the valve open error can be reduced by 18.33% and the valve close error can be reduced by 4% at least both at stable conditions and transient conditions. At stable conditions, the valve open error is not more than 0.39 °CA, and the valve close error is not more than 0.44 °CA.

Performance-Matching Optimization Design of Loader-Hydraulic System Based on Hydrodynamics Analysis

The study of the performance of dynamic hydraulic throttling under the condition of stable fluid is of great significance. The effect of a step change in pressure differences on the throttling performance of a hydraulic valve is studied. This paper studies the dynamic and static performance of a hydraulic-valve-outlet throttling-speed regulation system, builds a more accurate mathematical model, considers the linear factors of the flow of hydraulic-valve throttling, analyzes the influence of the step-load change in pressure difference on the stability of the hydraulic-valve movement speed, and constructs a nonlinear mathematical model of the speed-regulation system of the outlet throttling. A pressure sensor is used to measure the change in pressure overshoot, and the effect of a pressure-difference step change on the throttling performance of the hydraulic valve is studied under steady-fluid conditions. The theory is analyzed and verified by experiment, and the parameters of hydraulic components are modified using the dynamic-change rule of the hydraulic valve’s two-chamber pressure.

A comparative performance assessment of hydrostatic thrust bearings operating with electrorheological lubricant

PurposeAn electrorheological (ER) fluid comprises dielectric particles suspended in an insulating viscous medium. ER lubricants are considered smart lubricants. They have been applied in hydraulic valves, power transmission devices and damping systems. The purpose of this study is to investigate the performance of hydrostatic thrust bearing operating with ER lubricant.Design/methodology/approachReynold’s equation was used to model the flow of the ER lubricant in the bearing. The continuous Bingham model was used to express the viscosity of the ER lubricant as a function of yielding stress, applied electric field and shear strain rate. The Reynolds equation is solved using the finite element method (weighted residual approach) to compute the film pressure as a primary variable and the lubricant flow rate, load-carrying capacity, stiffness and damping parameters as associated performance indices.FindingsThe effects of the pocket shape, compensating elements and ER lubricant on the bearing performance were investigated. The application of ER lubricant significantly enhanced the load-carrying capacity (48.2%), stiffness (49.8%) and damping (4.95%) of the bearings. Circular and triangular pocket bearings with constant-flow valves have been reported to provide better steady-state and rotor-dynamic performances, respectively.Originality/valueThis study presents the effect of an ER lubricant on the rotor-dynamic performance of hydrostatic thrust bearings with different pocket shapes.

Development of a novel two-dimensional(2D) three-way(3W) fuel flow control servo valve with constant pressure difference

To solve the problems of large volume, and low integration of traditional electro-hydraulic servo valve with constant pressure differential fuel metering device, a new two-dimensional three-way constant pressure differential fuel flow control servo valve (2D3WFFCSV) is developed. It innovatively adopts the advantages of lightweight of “two-dimensional hydraulic technology”, The constant differential pressure function and flow regulation function are integrated into a two-dimensional (2D) main spool with two degrees of freedom (rotational and axial degrees of freedom). The flow control process of 2D3WFFCSV is as follows: firstly, the armature of the torque motor and the two-dimensional piston are coaxially installed at the end of the two-dimensional piston, so the torque motor can directly drive the two-dimensional piston to rotate; secondly the “hydraulic servo screw mechanism”, which can amplify the power, is used to drive the two-dimensional piston to move in line; Finally, a pair of conversion mechanisms (roller group and spiral track conversion mechanism) are converted into the angular displacement of 2D main spool to control the area of flow valve port. The axial degree of freedom of 2D main spool realizes the function of constant differential pressure. To improve the flow control accuracy of the servo valve, the axial position of the 2D piston is detected by the linear displacement sensor (LVDT), and the signal is transmitted to the controller to realize the closed-loop control. To explore its open-loop characteristics, the mathematical models of torque motor, two-dimensional piston and main spool are established to obtain its open-loop transfer function. Then the AMESIM simulation model is built. To optimize the design of the system, through the dynamic simulation of the system, the influence of key parameters on the dynamic response of the system can be studied. An experimental study is carried out to verify the design feasibility of the servo valve. The experimental results show that under the condition of no-load and full-scale input, the closed-loop delay of the servo valve is 1.84%, the linearity is 2.14%, the step response time is 43 ms, and the dynamic frequency response is 38 Hz. The newly developed 2D3WFFCSV has the advantages of high integration, small size, light weight (801.5 g) and high response and control accuracy. It can replace the constant differential pressure, metering valve and hydraulic servo valve in the aeroengine fuel regulator.

ЗАСТОСУВАННЯ КОМБІНОВАНОЇ СХЕМИ ОДНОФАЗНОГО ВКЛЮЧЕННЯ АСИНХРОННОГО ДВИГУНА ЯК ЗАСІБ ПІДВИЩЕННЯ ЕНЕРГОЕФЕКТИВНОСТІ ГІДРОПРИВОДУ ПОСТУПАЛЬНОГО РУХУ

The peculiarities of the modes of operation of the hydraulic drive of translational motion with throttle speed control, in which the asynchronous motor with single-phase power supply is used as the primary actuator. A combined circuit of such an actuator with a phase-shifting capacitor is proposed, which allows to increase its energy efficiency in the forward and reverse modes of the hydraulic rod when changing the degree of opening of the hydraulic control valve by switching power circuits and using voltage regulation. References 10, figures 6, table 1.