Electro-hydraulic Servo Research Articles

Electro-Hydraulic System Monitoring and Control Using Multivariate Latent Methods

With the rapid development of technology of hydraulic automation systems is observed in our current era, an ongoing effort to introduce engineering technology, automated solutions in everyday life with an emphasis on the field of hydraulic automation systems. The systems sector develops increasingly their fields of application, whether simple or hydraulic circuits for modern hydraulic automation circuits. This paper outlines the use of a statistical multivariate technique called Principal Component Analysis (PCA) and applies it to the monitoring and control of electro-hydraulic servo systems. The experiments were conducted using on-off and PID approaches to control the position of a hydraulic cylinder under different speeds and different PID coefficients. This approach was implemented using data from position sensors with programmable logic controllers (PLC) with the aid of supervisory control and data acquisition system (SCADA) to control the system and make online monitoring for the behavior of the hydraulic cylinder. The SCADA concept was developed to be a universal means of remote access to a variety of local control modules, which could be from different manufacturers and allow access through standard automation protocols. in practice, large SCADA systems have grown to become very similar to distributed control systems in function while using multiple means of interfacing with the plant. They can control large-scale processes that can include multiple sites, and work over large distances as well as small distances. It is one of the most commonly used types of industrial control systems, both large and small systems can be built using the SCADA concept, these systems can range from just tens to thousands of control loops depending on the application. PCA was used to detect the best speed and coefficient of the process. The proposed technique can be used for electro-hydraulic servo system monitoring in a real-time environment.

Adaptive Terminal Sliding Mode Control of Uncertain Electro-Hydraulic Position Servo Systems

To solve the position tracking control problem of nonlinear and uncertain electrohydraulic servo systems, an adaptive terminal sliding mode control method based on the backstepping method was proposed. This method combines the adaptive control with the terminal sliding mode method. On the one hand, the proposed adaptive control law can effectively estimate and compensate the uncertain parameters of the electro-hydraulic servo system on line, on the other hand, with the variable coefficient reaching law obtained through introduction of the error attractor into the sliding mode reaching law, the designed terminal sliding mode control law can not only eliminate the non-singular term in the ordinary terminal sliding mode control law, but also greatly reduce the chattering of the sliding mode surface. Finally, according to the Lyapunov stability theory, the finite time stability of the position tracking error was proved strictly. The proposed method was compared with the integral backstepping sliding mode control and the linear sliding mode control. The simulation results show that, the proposed method has good robustness and tracking accuracy in position tracking control of electro-hydraulic servo systems.

Position Control of an Electro-hydraulic Servo System with Disturbance

Position Control of an Electro-hydraulic Servo System with Disturbance

Position Control of an Electro-hydraulic Servo System with Sliding Mode

Position Control of an Electro-hydraulic Servo System with Sliding Mode

Study on wave velocity characteristics and compressive strength of concrete under different water pressure

In order to study the internal damage and static compressive strength of concrete under different water pressures, the wave velocity test and compressive test were carried out by NN-4B non-metallic ultrasonic testing analyzer and electro-hydraulic servo testing machine. The test results show that the high water pressure of concrete has an adverse impact on the development of its internal structure, and with the increase of high water pressure level, the slower the longitudinal wave passes through the specimen, the more serious the damage and deterioration of concrete, and the compressive strength decreases gradually with the increase of water pressure.

Reliability Test Rig of the Motorized Spindle and Improvements on Its Ability for High‐Speed and Long‐Term Tests

To realize the accurate performance test under high‐speed operation and the long‐term stable reliability test of the motorized spindle, a reliability test rig (RTR) which can simulate the cutting force in the actual machining process is presented. Firstly, a reasonable prototype integrating dynamic force loading devices and torque loading devices is designed and established based on the load analysis of the spindle, and a complete and explicit control strategy of the reliability loading test is designed. Secondly, the effects of misalignment of the diaphragm coupling caused by assembling are analyzed, and experiments are conducted to test the axis orbit of the motorized spindle. The experimental results illustrate that the axis orbit can identify the occurrence of misalignment, which ensures timely adjustment of misalignment and the accurate performance test under high‐speed operation. Lastly, a damper is added in the mechanical structure of the electrohydraulic servo loading system (EHSLS), and the comparison of Bode maps before and after optimization is analyzed by the Nyquist criterion. After the optimization, the gain and phase margin of the Bode diagram are 12.9 dB and 57.2°, respectively, which are both within the stable range and validate the improvements on the ability of long‐term reliability tests of the motorized spindle. The presented RTR is able to simulate the actual cutting force and provides an efficient loading approach to guarantee the accuracy and stability of motorized spindle tests.

Design on electrohydraulic servo driving system with walking assisting control for lower limb exoskeleton robot

According to the characteristics of human gait and the requirements of power assistance, locomotive mechanisms and electrohydraulic servo driving are designed on a lower limb exoskeleton robot, in which the miniaturization and lightweight of driving system are realized. The kinematics of the robot is analyzed and verified via the typical movements of the exoskeleton. In this article, the simulation on the power of joints during level walking was analyzed in ADAMS 2016, which is a multibody simulation and motion analysis software. Motion ranges and driving strokes are then optimized. A proportional integral derivative (PID) control method with error estimation and pressure compensation is proposed to satisfy the requirements of joints power assistance and comply with the motion of human lower limb. The proposed method is implemented into the exoskeleton for assisted walking and is verified by experimental results. Finally, experiments show that the tracking accuracy and power-assisted performance of exoskeleton robot joints are improved.

Dynamic constitutive behavior investigation of a novel low alloy ultra-high strength steel

The goal of this work is to reveal the dynamic mechanical properties and constitutive relationship of a novel low alloy ultra-high strength DT506 steel under high strain rates. The quasi-static state and dynamic compression behavior of the material at the strain rates of 10−3–103 s−1 were examined using an MTS landmark electro-hydraulic servo universal tester and a Split-Hopkinson bar (SHPB). The results show that DT506 steel is a strain-rate-sensitive material that shows an increase in strength with increasing strain rate. Based on the quasi-static and dynamic compression data, the parameters in the Cowper-Symonds (C-S) and the Johnson-Cook (J-C) models are determined. Since the previously developed models are cannot accurately predict the effect of the strain rate. A new theoretical model is obtained through the optimization of the parameters in the standard J-C model. The optimized model greatly improves the prediction accuracy of the true stress-strain dynamic behavior of materials. This new model is helpful for the verification of the underlying mechanism of the dynamic behavior of the material. Test results may provide basic data for future research on dynamic mechanical properties and constitutive relationship of metal alloys.

Application and Effect of Loading Rates on Coal Sample Failure

In order to evaluate the coal pillar stability in recovery of residual room pillars under different mining rates, this paper studies the influence of loading rate on the mechanical properties of the coal body. The uniaxial compression tests of coal samples in Yangcheng area at different loading rates were carried out with the MTS815 electrohydraulic servo rock mechanics test system. The stress‐strain curves and the evolution characteristics of AE signals were analyzed. At same time, the mechanism of damage and failure of specimens are also discussed. The results show the following. (1) With the increase in loading rate, the ultimate stress and ultimate strain of specimens decrease first and then increase. (2) Loading rate has a significant effect on the stability adjustment of specimens. With the decrease in loading rate, the earlier the stress adjustment is, the larger the adjustment range is, and the failure mode changes from shear failure to tensile failure. (3) In addition, when the loading rate increases, the AE evolves from continuous dense to discrete catastrophe, which indicates that the failure of the sample at a larger loading rate is sudden, which is not conducive to the maintenance of the stability of the coal pillar. (4) Finally, the failure mechanism of the specimen structure under different loading rates is obtained, and the improvement measures for the effect of mining velocity of working face on the stability of coal pillar are put forward. The results reveal the loading rate effect of mechanical properties of coal and provide a reference for controlling the stability of the residual coal pillar.

GA-tuning of Multivariable PID Controller for Electrohydraulic Load-Sensing Servo System

The main purpose of this article is to present the design, optimal setting and experimental study of a multivariable PID controller supposed for electrohydraulic power steering system with load-sensing function. The set of the controller is performed through an optimization procedure based on a genetic algorithm. The PID controller is embedded into a microcontroller for mobile machinery used in laboratory test rig for investigation of an electrohydraulic servo steering system. Results obtained in conditions of physical experiment and numerical simulation with the optimally tuned PID controller are presented. An analysis of the control performance, as well as some features of the used method for setting the PID controller.

Developing the Mathematical Model of the Bipedal Walking Robot Executive Mechanism

The paper considers the accuracy of footstep control in the vicinity of the application object. The methodology of forming a simulation of the executive electro-hydraulic servomechanism is developed. The paper presents control algorithms in the dynamic walking mode. The issues of stabilization of the sensors installed in the soles are investigated. The description of the laboratory model and simulation of the main links of the exoskeleton, approximated to human parameters, allowing to insert the studied algorithms of motion of the executive mechanism into the program of automation of calculations of the links of motion are given. The authors for the first time simulated the bipedal walking robot using modern digital technologies, including the joint use of pneumatic electric drive. This paper proposes an automated control scheme for manipulators controlling immobilized human limbs. Considering the functions of the leg and the phases of movement, the structure scheme is chosen so that the same actuator performs several functions. This construction partially reduces the load on the person, because the drives of the various links due to their gravity can overturn a person. Using the kinematic structure of the model and the method of adaptive control of the manipulator, as well as replacing some movement parts with plastic material, the authors were successful in reducing the total weight by three times compared with foreign analogues, which is important for a sick person.

Analysis of a Novel Automatic Control Approach for the Free Forging Hammer

This paper proposes an electro-hydraulic servo control method and realizes the automatic control and remote control of free forging hammers for the first time. A configuration and control strategy for the program-control free forging hammer are constructed. Based on the configuration, a single-acting differential servo cylinder system is proposed to drive the follow-up spool valve and then control the motion state of the hammerhead. Furthermore, a non-contact measurement method is adopted to detect the real-time position of the hammerhead, and the installation position of the measuring sensor is isolated from the hammer body and foundation, thereby reducing the influence of vibration and impact on the accuracy of the feedback signal and ensuring the successive forming process of the forging hammer. In addition, a blow energy model of the forging hammer processing system is established, and a fuzzy-PID control scheme for the forging hammer is then adopted. Based on the control strategy, the striking accuracy of the proposed automatic forging hammer is significantly improved compared with the traditional forging hammer. Finally, the method is applied to an 8 MN forging hammer, and the results show its better processing performance than traditional hammers in terms of all indices.

RBF Neural Network Sliding Mode Control Method Based on Backstepping for an Electro-hydraulic Actuator

Aiming at the interference problem and the difficulty of model parameter determination caused by the nonlinearity of the valve-controlled hydraulic cylinder position servo system, this study proposes a radial basis function (RBF) neural network sliding mode control strategy based on a backstepping strategy for the electro-hydraulic actuator. First, the non-linear system model of the third-order position electro-hydraulic control servo system is established on the basis of the principle analysis. Second, the model function RBF adaptive law and backstepping control law are designed according to Lyapunov’s stability theorem to solve the problem of external load disturbance and modelling uncertainty, combined with sliding mode control strategy and virtual control law. Finally, simulation and experiment on MATLAB Simulink and semi-physical experimental platform are accomplished to show the effectiveness of the proposed method. Moreover, results show that the designed controller has high tracking accuracy to the given signal.

Fault Prediction of Electro-hydraulic Servo Valve Based on CNN+LSTM Neural Network

Fault Prediction of Electro-hydraulic Servo Valve Based on CNN+LSTM Neural Network

Research on improved active disturbance rejection control of continuous rotary motor electro-hydraulic servo system

In order to meet the precision requirements and tracking performance of the continuous rotary motor electro-hydraulic servo system under unknown strong non-linear and uncertain strong disturbance factors, such as dynamic uncertainty and parameter perturbation, an improved active disturbance rejection control (ADRC) strategy was proposed. The state space model of the fifth order closed-loop system was established based on the principle of valve-controlled hydraulic motor. Then the three parts of ADRC were improved by parameter perturbation and external disturbance; the fast tracking differentiator was introduced into linear and non-linear combinations; the nonlinear state error feedback was proposed using synovial control; the extended state observer was determined by nonlinear compensation. In addition, the grey wolf algorithm was used to set the parameters of the three parts. The simulation and experimental results show that the improved ADRC can realize the system frequency 12 Hz when the tracking accuracy and response speed meet the requirements of double ten indexes, which lay foundation for the motor application.

Pressure impact characteristic of vane type continuous rotary motor under different buffer structures

In order to solve the problem of pressure shock on the continuous rotary electro-hydraulic servo motor, the mathematical models of pressure gradient under the structure of pre-compressed chamber and U-shaped groove were established. The optimal structure dimensions of the pre-compressed chamber and the U-shaped groove were determined. The fluid models were established by Solidworks under the four structures of triangular groove, triangular groove with pre-compression chamber, U-shaped groove and U-shaped groove with pre-compression chamber. Simulation analysis of depressurization process of fluid models was performed based on FLUENT. The pressure nephograms of different buffer structures were compared and analyzed, and the pressure change curves and pressure gradient change curves in the process of depressurization were obtained. The results show that the optimal edge length of the pre-compressed chamber of continuous rotary electro-hydraulic servo motor is 20 mm in the process of decompression. The pressure reduction effect is the best when the width of the U-shaped groove is 1.5 mm and the depth is 1.65 mm. The U-shaped groove structure with pre-compression chamber is more conducive to alleviate the pressure shock phenomenon of the motor compared with different combine buffer structures.

Comparative Study on the Mechanical Strength of SAP Internally Cured Concrete

To investigate the relationships between the different mechanical strengths of internally cured concrete with Super Absorbent Polymer (SAP concrete), the uniaxial mechanical properties of SAP concrete with different internal curing water-cement ratios were studied. Various SAP concrete specimens were prepared, and the uniaxial compressive, splitting tensile, as well as four-point bending tests, were carried out using the electro-hydraulic servo testing machine. The cubic compressive strength, splitting tensile strength, and flexural strength of SAP concrete with different internal curing water-cement ratios was obtained. The converting relationships between the internal curing water-cement ratio and different mechanical strengths were analyzed extensively. Based on the conversion formulas of different strength indexes proposed by different national standards and other researchers, the equations among the splitting tensile strength, cubic compressive strength, and flexural strength of SAP concrete were proposed and verified using the experimental data. According to the comparative analysis results, the proposed equations in this study have significant applicability and can be conducted in the practical application of SAP concrete.

Gradient identification method of the model parameters for electrohydraulic servo drive of FESTO learning system

Gradient identification method of the model parameters for electrohydraulic servo drive is considered. The method is adapted to be implemented by an experimental complex consists from FESTO hydraulic learning system and Matlab/Simulink. The implementation of the considered identification algorithm in the Matlab/Simulink package is shown.

Hardware-in-the-loop modeling applied to FESTO hydraulic learning system

The issue of Hardware-in-the-loop modeling in Matlab/Simulink using a physical model of an electrohydraulic servo drive implemented on FESTO learning system is considered. As an example, the synthesis of state components feedback coefficients for the electrohydraulic servo drive control is discussed. The paper provides the block-diagrams for connecting FESTO physical model to Matlab software and algorithms that allow using Matlab for automatic optimization of the controller parameters directly during the operation of the electrohydraulic servo drive physical model. Thus, already at the stage of optimizing the parameters of the controller, its operation as part of a real hydraulic system is studied.

Method for increasing the damping of an electro-hydraulic drive system of anthropomorphic walking robots

Annotation. Due to the fact that anthropomorphic walking robots (AWR) are becoming one of the classes of extreme robotics tools, the task of creating drive systems that simultaneously have high indicators for a set of parameters arises. In particular, the problem arises of preventing the occurrence of self-oscillations in conditions where servo drives with high quality factor experience strong dynamic mutual influence through the actuator. According to the totality of indicators for AWR designed for operation in extreme conditions, electro-hydraulic servo drives are preferable. Features of the dynamics of the ASH actuators and the electro-hydraulic drives used on them force us to look for new ways to correct their dynamic properties. This article presents a method of reducing the propensity of a drive system to generate self-oscillations by correcting hydraulic drives using acceleration feedbacks. It uses an estimate of the relative accelerations of the robot links during movement using the signals from pressure sensors installed in the actuator hydraulic motor. The calculations are made using the equations of dynamics of the AWR actuator, taking into account the temporarily imposed external connections. The method allowed to significantly increase the dynamic accuracy of the drive system of the prototype AWR developed by MSTU N.E. Bauman.