Electro-hydraulic Proportional Control Research Articles

Recent advances in control strategies and algorithms for pilot-operated electro-hydraulic proportional directional valves

Pilot-operated electro-hydraulic proportional directional valve is a key hydraulic component to control the motion of large power equipment such as construction machinery and agricultural equipment. The control accuracy and response speed of the valve control element are very important to the performance of the hydraulic system. In this paper, control strategies for dead-zone control and valve control systems are reviewed. In order to eliminate the dead-zone of pilot-operated proportional valve control, the current control schemes for dead-zone detection and dead-zone compensation are summarized, and the control schemes are evaluated. The proportional–integral–derivative-related control, nonlinear control, and robust control of the pilot-operated electro-hydraulic proportional directional valve control system are reviewed, the relationship between the control strategies is analyzed, and the different control algorithms are evaluated. The shortcomings of the research program are analyzed, and the corresponding solutions are proposed. Based on the current research, future research progresses for eliminating the control dead-zone and optimizing control strategies are presented.

Electrohydraulic proportional position and pressure loading control utilizing a state perception and processing method

A new multifunctional proportional control triaxial stress loading apparatus is presented in this study, which can apply an output force on coal rock to simulate the conditions of triaxial stress loading, aiming at solving the problems of excessive consideration of static indices in the design and the incompleteness of the simulation and test verification system for the test parts at the performance analysis stage. This apparatus mainly combines the configuration of a triaxial stress loading system which can meet the stress loading requirements under different operating conditions, with the effective integration of multiple pressure loading operations based on the electrohydraulic proportional control method. In this context, a pressure and position combined control strategy based on the sliding mode is proposed to control the vertical and longitudinal loading hydraulic cylinders. Then, a co-simulation mode including the triaxial stress loading hydraulic system is established to verify the control strategy, system response characteristics and selection of the controller parameters. Furthermore, a multifunctional stress loading experimental platform is developed, and the stress loading characteristics with the proposed strategy are tested and analyzed. The results show that the triaxial stress loading hydraulic system can meet the response characteristics, the fluctuating deviation of the constant loading test can be restricted to 8.5%, the tracking error of the variable loading test is small, the minimum response time of instantaneous loading can reach 2.8 s, and the stress loading effect is noticeable. The experimental platform fully indicates that the stress loading system with the state perception and processing method as the core can meet a variety of verification indices of constant, variable and instantaneous loading tests. This research provides technical support for the smooth, synchronous control and intelligent operation of various types of hydraulic actuator machines.

Articulated vehicle rollover detection and active control based on center of gravity position metric

In this study, the adaptive adjustment technology, based on an Attitude and Heading Reference System, is applied to loaders, aiming to improve the rollover protection performance of articulated engineering vehicles. A dynamic rollover stability index for loaders is developed, coupling the roll angular velocity and the slope and height of the center of gravity. A nonlinear predictive model of the material weight is built, in order to attain the height of the center of gravity. An adaptive attitude adjustment system is proposed, totally based on electro-hydraulic proportional control technology, to adjust the attitude of the working system, so as to achieve a higher threshold value of the vehicle’s anti-tip performance. Finally, the rollover stability index and control methods, as proposed in this article, are validated using experiments. The boundary values that trigger the system’s operation are reduced to ensure safety, while the validation results prove that the proposed method is effective.

Design and Optimization of Hydropneumatic Suspension Simulation Test Bench with Electro-Hydraulic Proportional Control

Available hydropneumatic suspension simulation test benches have insufficient loading accuracy and limited functionality rendering them unsuitable for performance testing of heavy vehicles with this type of suspension. Therefore, a multi-functional compound simulation test bench was designed that used an electro-hydraulic proportional control technique. A mathematical model was established to describe the hydraulic loading system, and the transfer function of the system was derived. The gain and phase margins confirmed the stability of the system. A simulation model was established in the Simulink environment and step and sine signals of different frequencies were applied separately to analyze the dynamic characteristics of the system. The results showed that the system responded slowly and exhibited phase lag and signal distortion. The dynamic characteristics of the system were improved by incorporating an adaptive fuzzy PID controller. Simulation results showed that the response of the system to the step signal stabilized at the preset value within 0.3 s with no oscillation or overshoot. The improved system performed well in replicating the random vibrations of heavy vehicles operating on Class B and C roads. This confirmed that the system can satisfy the loading requirements of heavy vehicle hydropneumatic suspensions and can be used as a simulation test bench for such suspensions.

Evaluation of Hydraulic Characteristics of Electrohydraulic Proportional Valve (EHPV) for an Auto-Steering Tractor Application

The performance of the electrohydraulic proportional control valve (EHPV) employed in a tractor’s automatic steering system directly influences the steering performance. To develop a highly reliable EHPV, it is essential to analyze the hydraulic characteristics of the EHPV for several working conditions of tractors. This study aimed to measure and analyze the hydraulic characteristics of the EHPV according to tractor working conditions. The flow rate and pressure data of the EHPV were computed through the valve measuring system, and the required power was computed. The experimental conditions were selected based on engine rotational speed and tractor steering angle. As a result, it was discovered that the flow rate, pressure, and power all increased when the engine rotation speed and steering angle conditions increased. Furthermore, the rates of increase in flow rate, pressure, and power based on the increase in the steering angle were higher than when the engine rotation speed increased. In the regression analysis results between the two variables and the hydraulic characteristics of EHPVs, the steering angle demonstrated a higher correlation than the engine rotation speed. In conclusion, the steering angle and engine rotational speed are the major variables in the hydraulic characteristics of EHPVs, and the influence of the steering angle is greater.

Research on Hydro-pneumatic Suspension Test Bench Based on Electro-hydraulic Proportional Control

Compared with the traditional automotive suspension, hydro-pneumatic suspension has the characteristics of large energy storage ratio, nonlinear stiffness and can change the ground clearance of the vehicle body, which makes the vehicle have good ride comfort and handling stability during driving. In order to improve the performance of hydro-pneumatic suspension, it is necessary to design hydro-pneumatic suspension test bench for performance test. Aiming at the problem that the output signal of the mechanical test bench used in China is single and has large error, which is difficult to meet the performance test requirements of hydro-pneumatic suspension, a hydro-pneumatic suspension test bench based on electro-hydraulic proportional control is designed. Through AMESim/MATLAB joint system modeling and simulation, in the tracking comparison of sinusoidal signal, compared with the traditional PID control method, the fuzzy PID control method reduces the error by 56.8% and the lag time by 70%; Through the experimental analysis of hydro-pneumatic suspension elastic force characteristic diagram, indicator diagram and damping force velocity characteristic diagram, the error rate of the test bench in sinusoidal signal tracking experiment is less than 15%, which meets the test requirements of hydro-pneumatic suspension.

Design and Implementation of W-shaped Steel Band Hole Image Recognition System Based on OpenCV-Python

The mine Roofbolter is widely used in drilling and supporting of underground roof and side wall, which greatly alleviates the imbalance of driving anchor. However, with the progress of sensor technology, electrical and electronic technology, electro-hydraulic proportional control technology and the continuous improvement of users’ requirements for the safety and efficiency of bolt support, domestic and foreign mining equipment manufacturers have carried out the development of automatic bolt and anchor cable support equipment, especially to improve the performance requirements of control system and develop intelligent visualization technology. At present, the hole location in the process of drilling still needs to be identified and located by human eyes, which is inefficient and the working environment is a great threat to the physical and mental health of personnel, so it is urgent to introduce computer technology and artificial intelligence technology. In this paper, with the help of image recognition technology, machine vision recognition replaces human eye recognition of hole location, and puts forward an image recognition technology of W-shaped steel belt hole recognition system based on OpenCV to assist the scheme, so as to ensure the safety and efficiency of roadway support. This system uses pychar, opencv and python language to realize the recognition and positioning of W-shaped steel strip hole. The scheme has the advantages of small amount of calculation, high accuracy and fast recognition speed. This research conclusion provides a reference for the further spatial positioning analysis of W-shaped steel belt hole, and improves the efficiency of underground support operation and personnel safety.

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.

Research on Double Hanging Point Hydraulic Synchronous Control System Based on Fuzzy PID

Hydraulic hoist is required to open and close the gate. In recent years, scholars have studied a lot of different types of hydraulic hoist, in which the double point hydraulic hoist is one of them. Double point crane hydraulic hoist mainly uses the hydraulic synchronous system. In this paper, the hydraulic synchronous system as the research object, through the electrohydraulic proportional speed control valve research, analysis of its working principle. Then, the traditional PID control method and the fuzzy PID control method are compared and analyzed. It is found that the fuzzy PID control ability is better than the traditional PID control method. Fuzzy PID realizes hydraulic synchronization by adjusting the electro-hydraulic ratio of speed control valve.

Electro-Hydraulic Proportional Position Control Using Auto Disturbance Rejection Based on RBF Neural Network

Large friction force and large dead zone are two typical nonlinear characteristics of electro-hydraulic proportional valve controlled hydraulic cylinder position control system. Aiming at those characteristics, a dead zone dynamic compensation algorithm is researched in order to reduce the lag time and control error. At the same time, a control strategy of radial basis function (RBF) neural network combined with auto disturbance rejection control (ADRC) is researched according to the impact of different conditions. The experimental result shows that the proposed algorithm improves performance of the electro-hydraulic proportional valve controlled hydraulic cylinder position control system. In positioning control experiment, the overshoot is 0 and the stability error is 0. In tracking control experiment, the lag time is reduced from the original 1.5 s to 0.2 s with no flat top phenomenon and the maximum error was reduced from 20 mm to 3 mm.

Research on the performance of a novel electro-hydraulic proportional directional valve with position-feedback groove

Accurate posture control of hydraulic roof supports, which use pressurized water as their fluid power source, is an important part and research direction of intelligent fully mechanized mining face. At present, the large flow on/off directional valve used on the hydraulic roof support cannot meet the requirement of precise posture control of the roof support. To overcome the conundrum, a novel two-position three-way electro-hydraulic proportional directional flow valve for hydraulic roof support is proposed. The new valve contains two pilot stages and two main spools. The two pilot stages cooperate with each other to control the movement of the two main valve spools, which are the inlet valve spool and the outlet valve spool. The inlet valve spool adopts the Valvistor principle. The valve can realize manual pilot control and electro-hydraulic proportional flow control of the passage P-A, which has been verified by a simulation model. In this paper, the static and dynamic mathematical models of the new proportional valve are established, and the key parameters affecting the valve performances are analyzed and verified by the simulation model. An optimization control scheme is proposed to overcome the influence of supply pressure, P-A pressure difference, and nonlinear interference force on steady-state displacement and response speed of the valve. The results show that this optimization method can significantly improve the response speed of the spool and promote the linearity of spool displacement under a slope signal. In addition, the fluctuation of chamber pressure and spool displacement caused by the discontinuous flow of a fast switching valve is systematically analyzed. The analysis shows that increasing pulse-width modulation carrier frequency is an effective way to reduce fluctuation amplitude. The research provides a new design idea and control method for an electro-hydraulic proportional directional valve of hydraulic roof support.

Active Disturbance Rejection Position Synchronous Control of Dual-Hydraulic Actuators with Unknown Dead-Zones.

In this paper, an integrated control strategy of position synchronization control for dual-electro-hydraulic actuators with unknown dead-zones is proposed. The unified control scheme consists of two parts: One is adaptive dead-zone inverse controllers of each hydraulic actuator to offset the unknown dead-zones. The other is the linear active disturbance rejection controller (LADRC) for position synchronization error. First, the model of the electro-hydraulic proportional position control system (EPPS) was identified by the forgetting factor recursive least square (FFRLS) algorithm. Next, the model reference dead-zone inverse adaptive controller (MRDIAC) was developed to compensate for the delay of actuator response caused by unknown proportional valve dead-zones. Meanwhile, the validity of the adaptive law was proven by the Lyapunov theory. Therefore, the position control accuracy of each hydraulic actuator is guaranteed. Besides, to improve the precision of position synchronization control of dual-hydraulic actuators, a simple and elegant synchronous error-based LADRC was adopted, which applies the total disturbances design concept to eliminate and compensate for motion coupling rather than cross-coupling technology. The performance of the proposed control solution was investigated through extensive comparative experiments based on a hydraulic test platform. The experimental results successfully demonstrate the effectiveness and practicality of the proposed method.

Analysis and Experimental Research on Shifting Impact of Loader Transmission

The evaluation index of loader shift quality was analysed, and the model of the evaluation index was established. The main causes of the shift impact of the transmission were analysed, and it was concluded that the disturbance caused by the torque of the transmission output shaft had a direct relationship with the oil filling and discharging rule in the clutch and the change in oil pressure. Based on theoretical analysis, an accurate control strategy of a proportional solenoid valve to realize electro-hydraulic proportional closed-loop buffering control was proposed. The buffer control of the transmission shift is performed by using this method. The effectiveness of the control strategy was verified by the experiment of the shift oil pressure. The shift impact of the transmission was reduced, and the loader shift quality was improved.

Regulation Method for Torque\u2013Angle Characteristics of Rotary Electric\u2013Mechanical Converter Based on Hybrid Air Gap

The torque–angle characteristics of electric–mechanical converters are important determinants of the quality of electrohydraulic proportional control systems. It is far more difficult for a rotary electric–mechanical converter (REMC) to obtain flat torque–angle characteristics than traditional proportional solenoid, greatly influencing the promotion and application of rotary valves for electrohydraulic proportional control systems. A simple and feasible regulation method for the torque–angle characteristics of REMCs based on a hybrid air gap is proposed. The regulation is performed by paralleling an additional axial air gap with the original radial air gap to obtain a flat torque–angle characteristic and increase output torque. For comparison, prototypes of REMCs based on hybrid and radial air gaps were manufactured, and a special test rig was built. The torque–angle characteristics under different excitation currents and step responses were studied by magnetic circuit analysis, finite element simulation, and experimental research. The experimental results were consistent with the theoretical analysis. It was shown that REMCs based on a hybrid air gap can obtain a flat torque–angle characteristic with further optimizing of key structural parameters and also increase output torque. This regulation method provides a new approach for the design of proportional rotary electromechanical converters.

Intelligent Operation of Wheel Loader Based on Electrohydraulic Proportional Control

In this paper, the wheel loader with electrohydraulic proportional control technology is used as the carrier. For the first time, the dual-angle sensor is used for intelligent operation, which allows the wheel loader working device to be precisely controlled. First, the theoretical analysis of the electrohydraulic proportional control technology on the wheel loader studied in this paper is carried out. Next, according to the feedback of the boom and bucket angle sensor signals, the electrohydraulic proportional control technology is used to initially realize the boom memory and bucket automatic levelling function of the wheel loader working device. Finally, the data acquisition equipment is connected to provide experimental verification, although the test results did not achieve precise control of the working device. After analysis, the detected problems were solved by constructing a neural network algorithm model, which successfully realizes the intelligent and precise operation of the wheel loader, reducing unnecessary energy loss.

Skid-Proof Operation of Wheel Loader Based on Model Prediction and Electro-Hydraulic Proportional Control Technology

Wheel loader shovel loading operation tests showed that when the tire slips, it not only causes waste of the engine power, but also increases the tire wear. In this paper, the regression prediction model is combined with the electro-hydraulic proportional control technology. For the first time, the method of adjusting the posture of the working device is proposed to realize the skid-proof shovel control strategy of the wheel loader. In this control strategy: (1) The electro-hydraulic proportional control technology applied to this wheel loader is introduced. (2) The load spectrum of the wheel loader is analyzed during the shovel loading operation. Moreover, combined with the drive shaft torque, pilot pressure and boom cylinder displacement, the particle swarm optimization-support vector machine (PSO-SVM) algorithm is used to complete the construction of the regression prediction model of the boom cylinder displacement. (3) A controller is designed based on the fractional-order PID control algorithm. The skid-proof control strategy is simulated and verified by constructing the joint simulation model. The corresponding program is prepared in the hydraulic system controller and the effectiveness of the control strategy and algorithm are verified by the wheel loader shovel loading operation.

Electro-hydraulic proportional control based pressurization and energy recovery integrated system in seawater desalination system

Electro-hydraulic proportional control based pressurization and energy recovery integrated system in seawater desalination system

Simulation and Analysis on Flow Rate of Electro-Hydraulic Proportional Control Piston Pump

In this paper, the flow rate model of an electro-hydraulic proportional variable piston pump is set up through mathematical modeling, and the simulation analysis is carried out through the MATLAB. The result provides some reference for the study of the electro-hydraulic proportional variable piston pump.

Parameters identification and trajectory control for a hydraulic system

In order to improve the tracking accuracy of a hydraulic system, an improved ant colony optimization algorithm (IACO) is proposed to optimize the values of proportional–integral–derivative (PID) controller. In addition, this paper presents an experimental study on the parameters identification to deduce accurate numerical values of the hydraulic system, which also determines the relationship between control signal and output displacement. Firstly, the basic principle of the hydraulic system and the mathematical model of the electro-hydraulic proportional control system are analyzed. Based on the theoretical models, the transfer function of the control system is obtained by recursive least square identification method (RLS). Then, the key parameters of the control system model are obtained. Some improvements are proposed to avoid premature convergence and slow convergence rate of ACO: the transition probability is revised based adjacent search mechanism, dynamic pheromone evaporation coefficient adjustment strategy is adopted, pheromone update rule and parameters optimization range are also improved. Then the proposed IACO tuning based PID controller and the identification parameters are modeled and simulated using MATLAB/Simulink and AMESim co-simulation platform. Comparisons of IACO, standard ACO and Ziegler–Nichols (Z–N)PID controllers are carried out with different references as step signal and sinusoidal wave using the co-simulation platform. The simulation results of the bucket system using the proposed controller demonstrates improved settling time, rise time and the convergence speed with a new objective function J. Finally, experiments with leveling operations are performed on a 23 ton robotic excavator. The experimental results show that the proposed controller improves the trajectory accuracy of the leveling operation by 28% in comparison to the standard ACO-PID controller.

Study on speed characteristics of hydraulic top drive under fluctuating load

A hydraulic top drive is a high-power gyrator used in oil or scientific drilling rigs, whose shaft is connected to drill pipe when it drives drilling tools to excavate well. The output speed of top drive determines the speed of drill bit directly. Load acting on the top drive shaft fluctuates randomly, which will cause top drive output speed hard to be in consistent with the setting value. This paper presents a main transmission system of a hydraulic top drive designed for deep continental scientific drilling, which was built with a multi-stage mechanical structure and a closed circuit hydraulic system with variable displacement pumps and motors. Electro-hydraulic proportional control was applied to vary the speed of the hydraulic top drive. A theoretical model is detailed for the hydraulic top drive main transmission system. Among the new techniques proposed in this paper is a simulation model for studying the performance of hydraulic top drive and capturing speed characteristics under fluctuant load. A drilling experiment of the hydraulic top drive was performed on the CRUST-I drilling rig in CCSD-SK-II well site. This paper concludes by comparing the results of the simulation model with theoretical results and drilling experimental data gathered in the hydraulic top drive possessing the same architecture, components, and control methods used within the simulation model. The drilling experiment and the analysis result showed that the hydraulic top drive could meet the requirements of deep continental scientific drilling and that the speed could be output according to the setting speed with very small oscillation. The simulation model can be used for several applications such as hydraulic top drive design and performance analysis of various drilling conditions.