Electro-hydraulic Control System Research Articles

Characteristics study of electro-hydraulic load-sensing control system for mobile machines

The hydro-mechanical load-sensing control is an efficient system solution to working function of mobile machines since the system pressure always adapts to the highest load pressure. The main issue of this system is its instability problem caused by hydro-mechanical feedback control. Moreover the pressure margin between system and load pressure set by the load-sensing compensator is usually fixed and has less control flexibility. Therefore, an electro-hydraulic load-sensing control system occurs, where the load pressure is sensed by pressure transducer and load-sensing control is achieved electronically. It eliminates the hydro-mechanical feedback control loop and has more control flexibility. The previous studies mainly focus on the system function, controller design and system efficiency. However the quantitative analysis of system characteristics has not yet been studied. Therefore, in this paper a method is provided to investigate the influences of pump displacement dynamics and preset pressure margin on system control performance. A hydraulic load-sensing control test rig is developed. Results show a good agreement between simulation and test results. The pressure margin fluctuation is reduced by using a pump with faster displacement dynamics and a larger cut-off frequency of load velocity control is obtained with a larger preset pressure margin however this results in lower system efficiency.

Modernization and Ways to Improve Reliability of Oil Supply to Steam Turbine Units for DPM-2

Russia has announced a DPM-2 programme to modernize old power plant equipment. One of the main areas of modernization is the replacement of some of the equipment while maintaining the foundations, building structures, most of the equipment and piping of the turbine unit. It is common practice to introduce additional equipment, such as control and protection units for electro-hydraulic control systems, as well as new pipework, which leads to problems in the layout of the steam turbine unit.The oil system is an integral part of the turbine unit. It accounts for a significant proportion of the cell volume of the steam turbine unit layout. This property of the system can be used to solve problems associated with the layout of a steam turbine unit in modernizations. A solution is proposed for redesigned layout of the oil system in the cell by introducing an oil supply module (station) into the structure of the steam turbine unit. As of now, there are no commercially available offers of an oil station with the required oil tank capacity. The oil station module is arranged at places free from equipment of the cell, for example, at the 0.000 elevation or under the upper operating mark near the generator and below the level of turbine unit bearings to enable oil drainage by gravity. The main differences are outlined between the proposed oil station and the existing oil system.The oil system determines the reliable and trouble-free operation of the steam turbine unit. In order to be able to introduce an oil supply module into operation it is necessary to design the system based on the requirement of maximum reliability. Reliability analysis of oil supply unit has been carried out. The regularities between the designer's decisions and the reliability of the resulting system are revealed. The influence is considered of the oil station components on individual reliability constituents: survivability, durability, fail-safety, maintainability, fire safety.

Research on control strategy of asymmetric electro-hydraulic servo system based on improved PSO algorithm

In the electro-hydraulic servo control system, there are some problems, such as low position control accuracy, uncontrollable speed, speed impact, and asymmetric control due to the asymmetry of hydraulic cylinder. To solve the above problems, this paper proposes a Fuzzy PID control algorithm with load force compensation based on improved PSO optimization. This improved particle swarm optimization algorithm introduces crossover and mutation operations in genetic algorithm to improve the optimization performance of traditional particle swarm optimization algorithm. The mathematical model of valve controlled asymmetric cylinder is established, and the Amesim linearization analysis function is used to identify the system, establish the transfer function, and build the control system. The joint simulation and test results of Amesim and MATLAB show that the proposed control strategy can realize the simultaneous control of speed and position. Under different loads, different speeds, and different input follow signals, it does not need to adjust any parameters. Regardless of forward or reverse operation, the optimal dynamic performance and minimum steady-state error are obtained, which greatly improves the response speed of the system. The effectiveness and superiority of the improved PSO compound control strategy are verified.

Research on Fault Diagnosis of PST Electro-Hydraulic Control System of Heavy Tractor Based on Support Vector Machine

Due to the harsh working environment of the tractor, the transmission can often be faulty. In order to ensure the reliability of its operation, it must be monitored and the fault discovered. In this paper, the support vector machine (SVM) method is used. The eigenvector conversion of the original data uses the following eigenvectors: Three fault modes (leakage fault of shift clutch hydraulic cylinder, blockage fault of oil passage, and blockage fault of proportional valve spool) are identified in matrix and laboratory (MATLAB) with the help of the library for support vector machines (LibSVM) toolkit, and the classification accuracy of test samples is 90%. The normal mode of the PST electro-hydraulic system and the three kinds of fault modes mentioned above are discriminated against, and the correct rate of fault diagnosis reaches 95%, which meets the needs of practical engineering. Analysis of the fault recording data of the power shifting transmission shift solenoid valve shows that the difference between fault pressure data and normal data is small, and the value of traffic data is greater. This method can realize the fault mode online recognition based on controller area network (CAN) communication, and the research results provide a theoretical basis for the fault diagnosis of the PST electro-hydraulic control system.

Exploring the Essence of Servo Pump Control

The electrohydraulic servo variable speed volume pump control system (hereinafter referred to as ESPCS) is integrated with a permanent magnet synchronous motor (hereinafter referred to as servo motor), a fixed-displacement pump, and a hydraulic cylinder. By controlling the servo motor speed, the output flow of the system can be controlled, as can the displacement, force, and speed of the hydraulic cylinder. Compared with the traditional electro-hydraulic servo valve control system, the ESPCS has the advantages of high power-to-weight ratio, energy saving, and environmental friendliness. However, due to the extremely nonlinear flow output of the ESPCS, further improvement of system control performance is greatly hindered. This paper focuses on the nonlinear characteristics of servo motor, fixed-displacement pump, hydraulic cylinder, and other key components in the system. A compensation method based on nonlinear characteristic mapping is proposed. Compared with the traditional PID control method (pressure control accuracy ± 0.12 MPa), the pressure control accuracy of the system is greatly improved (pressure control accuracy ± 0.037 MPa), which opens up a new way to improve the pressure control accuracy of the ESPCS.

Fuzzy Compensation and Load Disturbance Adaptive Control Strategy for Electro-Hydraulic Servo Pump Control System

Aiming at the high-precision position control of electro-hydraulic servo pump control system, a compensation control algorithm based on fuzzy control theory is proposed based on the classical PID control algorithm for the control of factors such as oil compression and system leakage. Firstly, a mathematical model of the system was established, and online identification of load disturbance was carried out. Then, oil compression and system leakage compensation controllers were established, and the position error caused by the load disturbance was compensated based on fuzzy control rules. Finally, the position control effect was verified using an experimental platform. The results show that the load disturbance compensation control strategy can significantly reduce the influence of load disturbance of the system. The steady-state accuracy of the system reached ±0.01 mm, which significantly enhanced the anti-disturbance ability of the system.

Development of Electro-Hydraulic Hitch Control System through Lower Link Draft Sensing of a Tractor

Three-point linkage plays an important role in controlling tillage implements with the hydraulic system of the tractor which includes draft control too. With increase in the usage of electronics and instrumentation in agriculture, the need was to upgrade the present mechanical hydraulic system of the tractor with electrohydraulic hitch control system (EHH) for better performance. The selection of draft sensing media was at the lower links for better sensitivity. The EHH control system through lower link draft sensing was developed using draft sensors, a control panel for user input and a controller with usage of MATLAB Simulink as an application software. Developed system was tested infield using duck foot cultivator and instrumentation like angle sensor, data acquisition and data logger were used for data capturing. The test results showed that for a change in set draft of 1500N, the system response time and change in depth of operation were 1.3s and 5 cm respectively. Whereas, for change in set draft of 500N the system response time was 0.9 s and change in depth of operation was 4 cm. For the conducted test, the variation in depth of operation was limiting to ±3.1 cm. The results concluded a direct relationship of change in set draft with system response time and change in operating depth. This study provides an overview of developing an EHH system through lower link draft sensing, as well as details of system architecture, control algorithm, MATLAB Simulink code, components used and the methodology and instrumentation technique for testing the same.

Classical and Metaheuristic Optimizations Performance in an Electro-Hydraulic Control System

Classical and Metaheuristic Optimizations Performance in an Electro-Hydraulic Control System

Development and Testing of an Electro-Hydraulic System for Height Control of Sugarcane Harvester Basecutter

HighlightsThis article focuses on an automatic control system for basecutter height.The influence of three factors on the performance indexes was studied.The best parameter combination for working performance was obtained.Abstract. Precision control of the basecutter height of sugarcane harvesters is an effective method to reduce stubble damage and sugar loss. Due to uneven ground, it is difficult to maintain the desired basecutter height. Therefore, an electro-hydraulic control system for controlling the basecutter height was developed to address these issues. In this control system, an angle sensor was used to detect the basecutter height by measuring the swing angle of a profiling device. To evaluate the performance of the control system, a series of tests was conducted with a mobile cutting platform. Forward speed (1, 2, or 3 km h-1), ground wavelength (1, 2, or 3 m), and ground amplitude (4, 8, or 12 cm) were selected as influencing factors. ANOVA of the orthogonal experiment results showed that forward speed and ground amplitude had significant effects on the coefficient of variation (CV) of cutting depth, while ground wavelength had a non-significant effect. The influence order of the factors on the CV of cutting depth was forward speed > ground amplitude > ground wavelength. The best combination was determined as a forward speed of 1 km h-1, ground wavelength of 2 m, and ground amplitude of 4 cm. A single-factor test indicated that a forward speed of less than 2 km h-1 can meet the requirement that the CV is less than 10%. This study provides a reference for future design and development of automatic adjustment systems for basecutter height. Keywords: Automatic adjustment of basecutter height, Electro-hydraulic control system, Sugarcane, Sugarcane harvester.

An Electrohydraulic Force Control System for Large-Scale Force Calibration

An Electrohydraulic Force Control System for Large-Scale Force Calibration

Development and performance evaluation of the electric-hydraulic concave clearance control system based on maize feed rate monitoring

Complex field environments, diverse crop conditions, and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters. In order to overcome these problems, an electric-hydraulic concave clearance automatic control system for the threshing unit was developed based on the maize feed rate monitoring, which can automatically realize the best match between the concave clearance and diverse feed rates during harvesting. The threshing performance of the electric-hydraulic control system was evaluated for varying and uneven maize feed rate fluctuations, such as the feed rate increased (6-8-10 kg/s), the feed rate decreased after an increase (6-10-8 kg/s, 8-10-6 kg/s), the feed rate increased after a decrease (8-6-10 kg/s, 10-6-8 kg/s), and the feed rate decreased (10-8-6 kg/s). In particular, the threshing rotor shaft peak torque, the range of threshing rotor shaft torque, the rate of broken grains (BGR), and the rate of unthreshed grains (UGR) with and without the electric-hydraulic control system were tested. Treatments with the electric-hydraulic control system were adjustable concave clearance with the value of 45 mm, 50 mm, and 55 mm. Treatments without the electric-hydraulic control system were constant concave clearance (50 mm). Results demonstrate that the threshing unit with the electric-hydraulic control system outperformed the one without the electric-hydraulic control system, with threshing rotor peak torque, the range of threshing rotor axis torque, the BGR, and the UGR decreasing by 18.38%, 38.27%, 2.08%, and 0.10%, respectively. Moreover, the rate of broken grains was lower than 5.00%, better than the national standard. Thus, the feed rate fluctuations and timely adjustment of the concave clearance were able to avoid blocking the rotor and improve the threshing performance compared to the constant concave clearance. Keywords: maize harvester, threshing cylinder, feed rate, concave clearance, electro-hydraulic control system DOI: 10.25165/j.ijabe.20221502.6369 Citation: Fan C L, Zhang D X, Yang L, Cui T, He X T, Zhao H H. Development and performance evaluation of the electric-hydraulic concave clearance control system based on maize feed rate monitoring. Int J Agric & Biol Eng, 2022; 15(2): 156–164.

Power Equipment Defects Prediction Based on the Joint Solution of Classification and Regression Problems Using Machine Learning Methods

Our paper proposes a method for constructing a system for predicting defects and failures of power equipment and the time of their occurrence based on the joint solution of regression and classification problems using machine learning methods. A distinctive feature of this method is the use of the equipment’s technical condition index as an informative parameter. The results of calculating and visualizing the technical condition index in relation to the electro-hydraulic automatic control system of hydropower turbine when predicting the defect “clogging of drainage channels” showed that its determination both for an equipment and for a group of its functional units allows one to quickly and with the required accuracy assess the arising technological disturbances in the operation of power equipment. In order to predict the behavior of the technical condition index of the automatic control system of the turbine, the optimal tuning of the LSTM model of the recurrent neural network was developed and carried out. The result of the application of the model was the forecast of the technical condition index achievement and the limiting characteristic according to the current time data on its values. The developed model accurately predicted the behavior of the technical condition index at time intervals of 3 and 10 h, which made it possible to draw a conclusion about its applicability for early identification of the investigated defect in the automatic control system of the turbine. Thus, we can conclude that the joint solution of regression and classification problems using an information parameter in the form of a technical condition index allows one to develop systems for predicting defects, one significant advantage of which is the ability to early determine the development of degradation phenomena in power equipment.

Position Output Adaptive Backstepping Control of Electro-Hydraulic Servo Closed-Pump Control System

A nonlinear adaptive backstepping control method was proposed to address the system parameter uncertainty problem in the position control process of an electro-hydraulic servo closed-pump control system. This control strategy fully considers the parameter uncertainty of the nonlinear system and establishes the adaptive rate of the uncertain parameter to adjust the parameter disturbance online in real time, thereby improving the accuracy and robustness of the control system. A pump control system experiment platform was used to verify the feasibility of the controller. The experimental results showed that the proposed control strategy provided a good control effect. The pump control system can be controlled with high precision, with a steady-state control accuracy of ±0.02 mm, which serves as a good foundation for the engineering application and promotion of the pump control system.

Control efficiency improvement of an electro-hydraulic winch

The paper presents a study regarding electro-hydraulic control systems for drive winches, a structural part of LARS (Launch and Recovery Systems). In the Introduction section of the paper, the authors present the domains of the research vessel. Furthermore, there is presented the importance of launch and recovery systems (LARS) and drive winches on the deck of a research vessel. The launch and recovery systems (LARS) using drive winches are installed on the stern of the research vessel. Further in the paper, the authors present the results of studying three simplified systems that use electric, hydraulic and electro-hydraulic driving solutions. Furthermore, there are presented comparative advantages of using this three types of drive winches. At the end of the paper, the authors perform an analysis of the electro-hydraulic systems for the drive winch, using a modelling and simulation software. Each schematic is presented along with its components. Moreover, the authors mention that all the schematics presented in this paper are modelled using FluidSim software from FESTO. In this case, only three mathematic relations are used in the paper: the Cauchy momentum (convective form), the incompressible Euler relations and the pressure losses in the hydraulic and electro-hydraulic drive winch.

Robust Nonlinear Control Scheme for Electro-Hydraulic Force Tracking Control with Time-Varying Output Constraint

This paper presents a robust nonlinear control scheme with time-varying output constraint for the electro-hydraulic force control system (EHFCS). Two typical double-rod symmetrical hydraulic cylinders are employed to simulate force environments in the EHFCS. Therefore, in order to improve the performance of the EHFCS, firstly, the model of the EHFCS is established with taking external disturbances, parameter uncertainties as well as structural vibrations into consideration. Secondly, in order to estimate external disturbances, parameter uncertainties and structural vibrations in the EHFCS and compensate them in the following robust controller design, two disturbance observers (DOs) are designed according to the nonlinear system model. Thirdly, with two estimation values from two DOs, a time-varying constraint-based robust controller (TVCRC) is presented in detail. Moreover, the stability of the proposed controller is analyzed by defining a proper Lyapunov functions. Finally, in order to validate the performance of the proposed controller, a series of simulation studies are conducted using the MATLAB/Simulink software. These simulation results give a fine proof of the efficiency of the proposed controller. What’s more, an experimental setup of the EHFCS is established to further validate the performance. Comparative experimental results show that the proposed controller exhibits better performance than the TVCRC without two DOs and a conventional proportional integral (PI) controller.

Modeling, simulation and experimental validation of flow rate of electro-hydraulic hitch control valve of agricultural tractor

Advances in non-linear control theory have made it possible to develop controllers for non-linear dynamic systems in their nature. The low-cost proportional control valves of the hydraulic control system are examples of such a system where there is no linearity due to the structure of the valves and the flaws in the spool. However, the non-linear analysis and regulation of these hydraulic systems cannot be done without a proper valve model. This paper presents a methodology for the development of an efficient unified model of a three-point hitch (TPH) electro-hydraulic proportional control valve control system for agricultural tractors by means of a parameter estimation technique. Modeling and simulation of the proportional control valve was performed using MATLAB Simulink software. Parameter estimation methodology was used to optimize the effective orifice opening of the solenoid valve to meet the flow characteristics available in the manufacturer's technical data sheet for the proportional control valve model parameters. Such unified Simulink models are useful for simulation, practical capability testing, and non-linear control design. Modeling and simulation of electro-hydraulic hitch (EHH) control valve were made and simulation results were compared with actual experimental results. The simulation results of the TPH lifting and lowering time were found to vary 4 and 12.5 %, respectively with the experimental results. This type of parameterized valve models facilitates their implementation in dynamic simulation models of complex hydraulic systems.

Design, simulation, and experiment research on fast control system of steam turbine inlet valve

In this paper, a new fast control system of steam turbine inlet valve is designed, which is composed of the fast closing system and the fast opening system. For the first time, this paper proposes that the fast closing system is designed by means of the special structure of the slide valve in an oil servo motor on the basis of the transformation of the hydraulic control system of steam turbine inlet valve. For the first time, a differential oil discharge fast opening system is designed by use of two cartridge valves. The mathematical model of electro-hydraulic fast control system is presented. With the use of simulation software Advanced Modeling Environment for Simulation of engineering systems , the curves of parameters such as piston displacement, piston velocity, oil pressure of upper and nether cavities of oil servo motor, and flow flux of upper and nether cavities of oil servo motor are obtained. The fast closing time of the piston for whole journey from the simulation results is 0.36 s. The fast opening time of the piston for whole journey from the simulation results is 1.55 s. According to the designed structure of the fast control system, the fast control experiment system is built. The fast closing time of the piston for whole journey from the experiment results is 0.22 s. The fast opening time of the piston for the whole journey from the experiment results is 1.97 s. The simulation and experimental results show that the designed fast control system can realize the fast closing and fast opening of the inlet valve. The fast closing time of the fast control system is <0.5 s, and the fast opening time of the fast control system is <3 s, which meets the fast control time requirement of the steam turbine inlet valve. Compared with the existing fast control system products, the fast control system and the inlet valve servo regulation system share a set of oil sources. And the fast control system has the advantages of low cost, simple structure, easy implementation, etc.

Introduction of degradation modeling in qualification of the novel subsea technology

All-electric systems are the novel subsea technology that is an upgrade of widely deployed electro-hydraulic control systems. They promised more reliable equipment and a safer environment. An all-electric production system performs several functions related to hydrocarbon production control. It also performs safety functions by isolating the reservoir from the environment. Safety functions are performed by activation of safety valves. These safety valves include electric springs in their design instead of mechanical springs. Failure modes and effects analysis of these valves show that interruptions in the power supply appear as random demands to the safety valves, and experiencing such demands may deteriorate their performance. However, the current reliability assessment of safety valves does not consider any degradation phenomena. This paper’s main objective is to investigate the degradation modes caused by demands and their influence on the all-electric actuation system’s performance under different maintenance strategies. A degradation modeling framework based on the multiphase Markov process is proposed. The impact of demand is modeled by changing the initial condition or by increasing the transition rates between two degraded states. The amplitude of the increment depends on the condition at the time of the demand. Analytical formulae are developed for the time-dependent reliability assessment.

High-accuracy electrohydraulic control system for the position and orientation of the primary mirror for a large telescope

High-accuracy electrohydraulic control system for the position and orientation of the primary mirror for a large telescope

Parametric Vibration Analysis of a Six-Degree-of-Freedom Electro-Hydraulic Stewart Platform

Electro-hydraulic Stewart 6-DOF platform is a 6-DOF parallel mechanism combined with the electro-hydraulic servo control system, which is widely used in the field of construction machinery. In actual working conditions, the flow and pressure pulsation of the hydraulic oil output from the hydraulic leg of the electro-hydraulic Stewart platform are inevitable, so the equivalent stiffness of the platform leg will change, and the stiffness parameters of the transmission system will change, resulting in vibration, which will affect the accuracy of the platform. This paper considering the fluid unit equivalent stiffness cyclical fluctuations and leg, on the basis of the relationship between hydraulic stiffness, constructs the electric hydraulic Stewart platform machine vibration dynamics equation, fluid coupling parameters of vibration parameters using the method of the multiscale approximate analytic formula of the main resonance and combination resonance are derived, and the system parameters vibration time-domain response and frequency response under two different poses are discussed. Results show that the system first to six order natural frequency and the first to the sixth order natural frequency and frequency of hydraulic oil equivalent stiffness of the combination of frequency will have an effect on the parameters of the system vibration. In the main resonance, the dominant frequency is mainly the first to sixth order natural frequency of the system; in the combined resonance, the dominant frequency is the combined frequency. Through the parameter vibration analysis of two different positions of the platform, it is concluded that when the platform is in an asymmetric position, each leg of the system is more involved in vibration. This study can provide the reference for the subsequent dynamic optimization and reliability analysis of the electro-hydraulic Stewart platform.