Electro-hydraulic Control System Research Articles

Components of an innovative electro-control system for undeground mining – analysis

Abstract In the era of Industry 4.0, coal companies began to reach for new innovative technologies that increase work safety and their possible use affects the economic improvement of companies. One of them is to equip a powered roof support section with an electrohydraulic control system with a monitoring system that tracks operating parameters. The development of a monitoring system for a powered roof support is a key investment in new longwall complexes. It allows rapid diagnostics of status of the support. Currently used system designed to control the powered roof support are based on blocks of manually controlled distributors. The pilot control is currently the leading control that properly functions in all conditions, allowing to adapt to the requirements resulting from the construction of the section. A number of tests and analyses must be conducted prior to introducing the new control based on an innovative approach into operation. The basic research has focused on identifying the user interface that will potentially be the solution for the entire system. The user has defined how the driver should look like and how it will be operated and maintained. The results of the first series of tests on the elements of an innovative electronic control system of the powered roof support enabled to develop a prototype version. The assumptions for the system were verified during the conducted development studies. The article presents preliminary results of development research for devices included in the innovative control system of the powered roof support.

Optimized PID Controller Based on Beetle Antennae Search Algorithm for Electro-Hydraulic Position Servo Control System.

To improve the controllability of an electro-hydraulic position servo control system while simultaneously enhancing the anti-jamming ability of a PID controller, a compound PID controller that combines the beetle antennae search algorithm with PID strategy was proposed, and used to drive the position servo control system of the electro-hydraulic servo system. A BAS-PID controller was designed, and the beetle antennae search algorithm was used to tune PID parameters so that the disturbance signal of the system was effectively restrained. Initially, the basic mathematical model of the electro-hydraulic position servo control system was established through theoretical analysis. The transfer function model was obtained by identifying system parameters. Then, the PID parameter-tuning problem was converted into a class of three-dimensional parameter optimization problem, and gains of PID controllers were adjusted using the beetle antennae search algorithm. Finally, by comparing the effectiveness of different algorithms, simulation and experimental results revealed that the BAS-PID controller can greatly enhance the performance of the electro-hydraulic position servo control system and inhibit external disturbances when different interference signals are used to test the system’s robustness.

A Review of Electro-Hydraulic Servovalve Research and Development

This paper provides a review of the state of the art of electro-hydraulic servovalves, which are widely used valves in industrial applications and aerospace, being key components for closed loop electrohydraulic motion control systems. The paper discusses their operating principles and the analytical models used to study these valves. Commercially available units are also analysed in detail, reporting the performance levels achieved by current servovalves in addition to discussing their advantages and drawbacks. Adetailed analysis of research that investigates these valves via computational fluid dynamic analysis is also provided. Research studies on novel control systems and novel configurations based on the use of smart materials, wh

Uncertainty Modeling Using a Dimension Search and a Genetic Algorithm With Application to Robust Stability Analysis

This work uses a new method of determining a parameterization, resampling, and dimension search of an uncertainty model that can be used for efficient engineering models in control design. An algorithm using the Cayley–Menger determinant as a measure of the dimension test geometry (volume/area/length) of the parametric data points is presented to search for a reduced number of dimensions that can be used to represent the parameters of a model that captures the uncertainty in a dynamic system (uncertainty model). A genetic algorithm (GA) is utilized to solve the nonconvex problem of finding the coefficients of a parameterization of the uncertainty model. A resampling approach for the uncertainty model is also presented. The methods presented here are demonstrated on an electrohydraulic valve control system problem. This demonstration includes consideration of the dimensional search, data resampling, and parameterizing of an uncertainty class determined from test data for 30 replications of an electrohydraulic flow control valve which were experimentally modeled in the lab. The suggested resampling method and the parameterization of the uncertainty are used to analyze the robust stability of a control system for the class of valves using both frequency domain h-infinity methods and analysis of closed-loop poles for the resampled uncertainty model.

An energy-saving and velocity-tracking control design for the pipe isolation tool

The pipe isolation tool demonstrates remarkable advantages in safety and efficiency compared with traditional plugging devices. However, its utilization in plugging operations is limited by demand of operation duration and precise velocity trajectory. In this article, a pipe isolation tool control system is designed for energy-saving and plugging part’s velocity tracking of the pipe isolation tool. To achieve energy recovery and velocity-tracking control, a flywheel and an accumulator are used for energy transformation and storage. A fuzzy proportional integral derivative controller is proposed to improve the ability of the desired velocity trajectory. The proposed control strategy, compared with the conventional pipe isolation tool drive system, is more energy efficient and has more internally stable dynamics on the closed-loop system. The results verify that both energy-saving and velocity-tracking objectives are satisfied for the electrohydraulic control system of the pipe isolation tool.

Operating Experience with Fire Resistant Turbine Control Fluid at Ramin Power Plant

In the last 30 years, the phosphate ester fire resistant fluid, OMTI, has been used in the electrohydraulic control systems at Ramin power plant. Difficulties in obtaining supplies of the fluid led to efforts to extend its service life of the fluid by on-site conditioning and, eventually, to searching for a replacement. This paper surveys the operating experience obtained during the past ten years with the different forms of treatment and the replacement of OMTI by an alternative phosphate ester fluid. Different methods for conditioning of waste oil has been used from alkaline washing to ion exchange treatment. In alkaline washing process, an aqueous potassium hydroxide (KOH) solution was used to neutralise the acidity of the fluid. Any potassium soaps that are formed partition into the aqueous phase and can then be moved. Since it was done on a small-scale batch process, a static separation process was used. But in ion exchange treatment adsorption of acidic material of waste oil on ion exchange resins was used for reclamation of the oil. In view of concerns expressed over the conditioning of the used fluid and trade restrictions on purchasing the new fluid, the availability of a phosphate ester fire–resistant fluid from other sources was investigated and a different fluid, Turbex F46, was identified as potentially suitable.

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.

A Novel Composite Control Algorithm for Restraining Nonlinear Superfluous Forces

A novel composite control algorithm is proposed to restrain nonlinear superfluous forces of a dual-channel load simulator. The dual-channel load simulator is utilized to measure the dynamic characteristic of an integrated hydraulic driving unit. The superfluous force cannot be avoided almost certainly and show a strong nonlinearity. Based on the speed synchronizing control algorithm, the composite control algorithm considers the two non-linear time-varying parameters of the flow gain Kq and the flow pressure gain Kc of the servo valve, and further considers the non-linearity and time-varying of the position disturbance electro-hydraulic servo control system. The fuzzy self-tuning PID control is applied to automatically adjust the PID parameters so that the superfluous force of the system can achieve the desired control effect. The accurate simulation of the load force is realized.

Numerical Simulations on Flow Characteristics of a Nozzle-Flapper Servo Valve With Diamond Nozzles

Nozzle-flapper servo valves are widely used in modern electro-hydraulic control systems of many engineering applications. Flow cavitation in the nozzle-flapper pilot stage could produce noise and cavitation erosion, reducing the performance stability and reliability of the servo valves. In this paper, diamond nozzles are proposed to replace the traditional circular nozzles to reduce the flow cavitation in the nozzle-flapper stage. Numerical simulations using CFD software ANSYS/FLUENT were conducted to explore the flow characteristics of the nozzle-flapper pilot stage. Mass flow rate and image measurements were performed to verify the simulation results. Vapor fraction, lateral velocity, pressure distribution, and flow force are compared in detail between the pilot stage with the traditional nozzles and with the diamond nozzles. It is found that the vapor fraction is greatly reduced under the effect of the diamond nozzles. Finally, to explore the effect of the diamond nozzles on the performance of the nozzle-flapper servo valve, the pressure-flow characteristics and time step response of the load flow rate are examined using the software AMESim. The simulation results show that the pressure-flow characteristics and time step response of the load flow rate almost remain the same. This suggests that the diamond nozzles could suppress the cavitation in the nozzle-flapper servo valve without varying its performance.

A New Availability Assessment Method for Complex Control Systems With Multi-Characteristics

This paper proposes a new availability assessment method for complex control systems with multi-characteristics based on the goal-oriented (GO) method to evaluate the lower confidence limit of its system availability. First, the GO method for complex control systems with multi-characteristics is illustrated in terms of expounding GO operators and proposing a new exact algorithm with shared signals. Then, the new availability assessment method is expounded in detail, and its process is formulated. Finally, the new method is used to evaluate the lower confidence limit of the system stability of the electrohydraulic control system of a power-shift steering transmission as an example. To verify its advantages and rationality, the availability assessment results and evaluation efficiency are compared with those obtained by the regular Monte Carlo method and the regular exact GO algorithm with shared signals. Furthermore, the coverage rate of the lower confidence limit of the system availability obtained by the new method is compared with the nominal significance level. Overall, this availability assessment method not only improves the theory of the GO method and widens its application but also provides a new approach for the availability assessment of complex control systems that reduces costs and improves the estimation efficiency and accuracy.

A Pressure-Coordinated Control for Vehicle Electro-Hydraulic Braking Systems

The characteristics of electro-hydraulic braking systems have a direct influence on the fuel consumption, emissions, brake safety, and ride comfort of hybrid electric vehicles. In order to realize efficient energy recovery for ensuring braking safety and considering that the existing electro-hydraulic braking pressure control systems have control complexity disadvantages and functional limitations, this study considers the front and rear dual-motor-driven hybrid electric vehicle as the prototype and based on antilock brake system (ABS) hardware, proposes a new braking pressure coordinated control system with electro-hydraulic braking function and developed a corresponding control strategy in order to realize efficient energy recovery and ensure braking safety, while considering the disadvantages of control complexity and functional limitations of existing electro-hydraulic system. The system satisfies the pressure coordinated control requirements of conventional braking, regenerative braking, and ABS braking. The vehicle dynamics model based on braking control strategy and pressure coordinated control system is established, and thereafter, the performance simulation of the vehicle-based pressure coordinated control system under typical braking conditions is carried out to validate the performance of the proposed system and control strategy. The simulation results show that the braking energy recovery rates under three different conditions—variable braking intensity, constant braking intensity and integrated braking model—are 66%, 55% and 47%. The battery state of charge (SOC) recovery rates are 0.37%, 0.31% and 0.36%. This proves that the motor can recover the reduced energy of the vehicle during braking and provide an appropriate braking force. It realizes the ABS control function and has good dynamic response and braking pressure control accuracy. The simulation results illustrate the effectiveness and feasibility of the program which lays the foundation for further design and optimization of the new regenerative braking system.

Tests of an Innovative Controller Designed to Control the Powered Roof Support

Abstract The article presents the methodology and results of tests of a prototype controller designed for the electrohydraulic control system of a powered roof support. This controller is the basic part of the developed, innovative control system. The tests were carried out on a custom-designed testing station, equipped with one section of a roof support. The aim of the research was to check the functionality and speed of the controller's response while working with the actual support section. The tested controller and the control system has a modular structure, which greatly facilitates its operation and use. Measurements of control functions were carried out on the controller connected to the electrohydraulic control block. The research mainly focused on determining the period starting from the moment of providing the signal to the moment of switching on the basic functions performed by the support section. The obtained results confirm the assumptions made. The controller's operation is very stable, and its response times are very short. It can therefore be assumed that the tested controller is correctly designed and constructed. This creates great possibilities for its practical application in the built-in system for controlling the roof support. This may be particularly important in the case of high-efficiency longwall complexes, for which wireless control of the support is planned to be used. The presented research methodology and obtained results should therefore be an important source of information in the field of testing controllers for powered roof supports.

A heuristic fault diagnosis approach for electro-hydraulic control system based on hybrid particle swarm optimization and Levenberg–Marquardt algorithm

In this paper, a novel heuristic neural network model based on hybrid particle swarm optimization and Levenberg–Marquardt (HHPSOLM) algorithm was proposed for fault diagnosis in electro-hydraulic control system. In this algorithm, the characteristics of strong local searching capability in LM algorithm were adopted to increase the diversity of population. In the first stage, the proposed method searched ten steps with the Levenberg–Marquardt (LM) algorithm for a random particle, and replaced the worst particle with the search result to increase the diversity. In the second stage, the HHPSOLM algorithm employed an inspiration to search the optimal solution with the LM algorithm for 30% of the particles to improve diversity of the particles. In the last stage, the feed-forward neural networks were trained with HHPSOLM to achieve the optimization of its weights and thresholds, then the fault diagnosis model of an electro-hydraulic control system was established with the HHPSOLM neural network. Its application in electro-hydraulic control system fault diagnosis was simulated. Experiment results showed that the diagnostic accuracy of the proposed method was higher than those of the Particle Swarm Optimized BP neural network (PSO-BP) or BP algorithm, thus the HHPSOLM algorithm was an efficient algorithm for optimizing neural networks, and suitable for fault recognition of electro-hydraulic control system.

Method for combining valves with symmetric and asymmetric cylinders for hydraulic systems

Electro-hydraulic position control systems are widely applied in several fields. The valve and cylinder configuration and the dimensioning of these systems is dependent on the requested transient r...

Composite adaptive force tracking control for electro-hydraulic system without persistent excitation condition

In this article, a composite adaptive control method without persistent excitation condition is proposed to improve force tracking performance of an electro-hydraulic loading system. Due to structure restriction, the force sensor cannot be installed and associated force signals are unable to be obtained by the control hardware. Thus, a composite adaptive control method is designed to estimate the unknown spring stiffness and friction coefficient of the electro-hydraulic loading system. Simultaneously, a modified prediction error is designed to relax the stringent persistent excitation condition of the conventional adaptive method. Then the position trajectory of the cylinder could be optimized by using the estimated stiffness to achieve accuracy loading for the specimen. Furthermore, first-order filters are utilized to produce certain virtual controllers and their derivatives to avoid analytic calculation. At last, the stability analysis of the closed-loop system is given, and the comparative experimental results have verified the effectiveness of the proposed control method.

Decoupling Compensation for Damping Improvement of the Electrohydraulic Control System With Multiple Actuators

This paper proposes a decoupling compensation method for damping improvement of the electrohydraulic control system with multiple actuators. The low damping property of hydraulic systems has been a remarkably troublesome issue for a few decades. Previously, this issue with one actuator has been addressed effectively by state feedback and signal compensation, e.g., dynamic pressure feedback. However, the poor damping with multiple actuators is still intractable and pendent due to the complex coupling effect of different loads. A decoupling compensator based on pump/valve combined control is proposed for a typical electrohydraulic system with multiple actuators for mobile machinery. Using decoupling control of different load branches, the coupling hydraulic circuit with multiple cylinders is transformed into multiple separate single-cylinder circuits with dynamic compensation. The dynamic characteristics of different actuators are then improved synchronously without mutual interference, while the steady performance remains the same without loss of controllability. Compound motion tests on a 2-ton hydraulic excavator were carried out. The results showed that the proposed compensator reduced velocity and pressure oscillations under different working conditions, so the dynamic performance is improved for the multiactuator system.

Review on Inlet/Outlet Oil Coordinated Control for Electro-Hydraulic Power Mechanism under Sustained Negative Load

Speed control and smooth regulation in an electro-hydraulic motion control system under negative load (over-running load) are crucial to mobile machineries, vehicles, and motion simulation equipment. Problems, such as bad natural stability, bad dynamic performance for small adjusting signal, serious coupling, and difficulty to coordinate between speed smoothness and speed regulation, exist in traditional valve-controlled and pump-controlled electro-hydraulic power mechanism. The coordinated motion control scheme, which is based on independent regulation of inlet/outlet oil for electro-hydraulic power mechanism has attracted the attention of many scholars. In the last two decades, many progresses had been made in coordinated control technology, employing in inlet/outlet independent metering and pump/valves independent regulation. Moreover, the technology has been widely used in the electro-hydraulic operating system in hydraulic excavator and the speed smoothness control system in heavy transport vehicles. In this study, recent advancements and upcoming trends in coordinated control and inlet/outlet independent metering for electro-hydraulic power mechanism under sustained negative load are reviewed. Firstly, related research advancements are summarized, including flow rate regulation mechanism based on inlet/outlet coordinated control, coordinated control strategy and nonlinear control method of electro-hydraulic control system. Then, nonlinear modeling of inlet/outlet independent metering and pump/valves independent regulation in electro-hydraulic control system is presented. In addition, the electro-hydraulic speed smoothness control and energy recovery for heavy engineering vehicles under long down-slope is discussed and reviewed. Finally, existing problems and future trends of inlet/outlet coordinated control for an electro-hydraulic power mechanism under sustained negative load are presented.

Efficient pump and meter-out control for electrohydraulic system with time-varying negative load

In hydraulic systems under negative loads, counterbalance valves are widely employed, which introduce instability and sizable energy consumption. This article focuses on the electrohydraulic system with meter-out orifice and variable pump, which allows flexible control structure. The target is to reduce inlet pressure level as well as diminish oscillation caused by time-varying loads. An extended load observer is constructed to estimate the external load. Accordingly, a robust back-stepping controller with integral part and disturbance compensation is proposed to regulate the meter-out orifice, achieving velocity-oriented control. Also, a model-based pressure-oriented controller is developed to determine pump displacement. The target is set to 3 bar in this work, while the pressure losses in conventional systems are more than 12 bar. The stabilities of these two independent controllers are both proved by Lyapunov theory. Experiments focusing on energy consumption, load compensation, and velocity tracking are carried out verifying the controller effectiveness. Discussions of results illustrate that the whole proposed controller succeeds in velocity tracking and reducing energy consumption in the presence of time-varying negative load.

Pose and trajectory control of shield tunneling machine in complicated stratum

The present study is focused on developing a method for controlling the pose and trajectory of a shield tunneling machine (STM) applied in complicated stratum. Lacking method to determine target motions of thrust cylinders and suitable electro-hydraulic control system are major restrictions for the STM to realize automatic pose control. To overcome these bottlenecks, a mathematical method for determining the target motions of thrust cylinders is proposed based on kinematic analysis of the thrust mechanism. With this method, target motions of thrust cylinders when the STM excavates along any specific curves can be obtained and used as the input signal of the pose control system. A multi-cylinder control system is proposed based on master/slave control strategy to control the length of each kinematic chain in order to adjust the pose of the thrust mechanism. Experiments are carried out to evaluate the performances of this control system. The experimental results verify that the proposed pose control system is effective in controlling the pose and trajectory of the shield machine no matter it advances along a straight or a curved tunnel axis. Considering the complex loads during the experiments, the proposed system has great potential for applying in practical tunnel construction.

Simulation Studies of CMAC-PID Combined Control for Electro-hydraulic Position Servo System

An electro-hydraulic servo system is taken as control object, the control strategy combining CMAC network with the PID controller is discussed. The inverse dynamic control is realized using CMAC neutral network as feed-forward controller, the PID controller is acted as feedback controller to subdue the turbulence and guarantee its stabilization. Output signals from the CMAC network and from a conventional PID controller are integrated to constitute an overall output signal, which then acts on the controlled object. Thus, good regulating performance by itself is guaranteed. The AMESim model of the electro-hydraulic servo control system is established, and the collaborative simulation of hydraulic system model and control algorithm is implemented. Simulation results show that this control strategy is effective and practical.