Electro-hydraulic Loading System Research Articles

Neural adaptive dynamic surface control of an electro-hydraulic loading system for rail grinders

Neural adaptive dynamic surface control of an electro-hydraulic loading system for rail grinders

Passivity-based adaptive robust super-twisting nonlinear control for electro-hydraulic system with uncertainties and disturbances

In this paper, a passive-based adaptive robust super-twisting nonlinear controller (PBARSNC) is proposed for high accuracy torque tracking control of the novel electro-hydraulic loading system with disturbances and uncertainties. The construction of the stability of this electro-hydraulic control system is given using passivity theory that results in a passivity-based controller (PBC). Considering parameter uncertainties and constant or slowly varying disturbances, adaptive law is adopted in the passivity-based controller. Furthermore, super-twisting second-order sliding mode control is used to reject modeling uncertainties and matched disturbances. Passivity theory, adaptive method and super-twisting algorithm are synthesized via the recursive design method. The proposed passive-based adaptive robust super-twisting nonlinear control can guarantee the torque tracking performance in the presence of various uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems. Extensive simulations are carried out to verify the high-accuracy tracking performance of the proposed control strategy.

The Crack Analysis of Fatigue Tested Steel Construction

Laboratory fatigue testing is an important part of the fatigue design of machine components that are supposed to work under cyclic loading. These tests are used to confirm whether the tested component matches the required fatigue life and they also serve as a verification of the numerical calculations. This paper describes a fatigue life testing of a welded steel construction. The testing was carried out in the Regional Technological Institute (RTI) using an electro-hydraulic loading system, which allows realization of the tests simulating a real service. An integral part of the fatigue tests is a pre-scheduled inspection of the crack initiation and propagation. The tested construction was checked using non-destructive magnetic particle testing before the fatigue test and also during and after the performed test. Some cracks were observed, especially in the weld area. The biggest crack had the length of approximately 40 cm. This crack was cut out and underwent detailed metallographic and fractographic analysis to estimate the effect of material purity and quality of the weld on the fracture.

A novel kind of electrohydraulic loading system based on friction for actuator test

Conventional electric or electrohydraulic load simulator is disturbed by the motion of the tested system. To eliminate the strong motion disturbance and improve loading performance, a novel kind of friction electrohydraulic loading system is proposed. The mechanism of friction electrohydraulic loading system is described in detail. The math model for the loading torque and the input signal has been deduced, which indicates that this proposed friction electrohydraulic loading system has no disturbances resulting from tested actuators under ideal conditions. However, friction coefficient is time-varying and uncertain. The friction device increases the load inertia of the actuator. The additional inertia may affect the loading performance. The structure mechanism has been optimised to reduce the rotary inertia. To verify the loading performance of friction electrohydraulic loading system, simulations and experiments are carried out. Compared with conventional electrohydraulic load simulator, the theoretical analysis and experimental results validate the feasibility of the friction electrohydraulic loading method. The novel friction electrohydraulic load simulator, with a simple control principle and easy engineering constructability, can provide accurate torque simulation for actuator test.

A novel kind of electrohydraulic loading system based on friction for actuator test

Conventional electric or electrohydraulic load simulator is disturbed by the motion of the tested system. To eliminate the strong motion disturbance and improve loading performance, a novel kind of friction electrohydraulic loading system is proposed. The mechanism of friction electrohydraulic loading system is described in detail. The math model for the loading torque and the input signal has been deduced, which indicates that this proposed friction electrohydraulic loading system has no disturbances resulting from tested actuators under ideal conditions. However, friction coefficient is time-varying and uncertain. The friction device increases the load inertia of the actuator. The additional inertia may affect the loading performance. The structure mechanism has been optimised to reduce the rotary inertia. To verify the loading performance of friction electrohydraulic loading system, simulations and experiments are carried out. Compared with conventional electrohydraulic load simulator, the theoretical analysis and experimental results validate the feasibility of the friction electrohydraulic loading method. The novel friction electrohydraulic load simulator, with a simple control principle and easy engineering constructability, can provide accurate torque simulation for actuator test.

Iterative learning based output feedback control for electro-hydraulic loading system of a gait simulator

In this paper, a novel gait simulator is developed for in vitro studies of the normal kinematics and kinetics of the human foot during the stance phase of the gait. In order to make the ground reaction force of the gait simulation in a manner similar to in vivo, an electro-hydraulic loading system (EHLS) is utilized for tibia loading. Since only the position and loading force signals are available, a high-gain observer is designed to estimate the unmeasured states of the EHLS, and the dynamic surface control is implemented for position tracking of the EHLS. The desired position trajectory of the EHLS could be optimized by an iterative learning mechanism such that the tibia loading force could be as close as possible to the target curve in the complex gait simulation process. The experimental results have verified the effectiveness of the proposed control method, and the average tibia loading error can be maintained within 1.5% of the total loading range.

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.

Optimisation of Engineering Systems With the Bees Algorithm

This article describes the Bees Algorithm in standard formulation and presents two applications to real-world continuous optimisation engineering problems. In the first case, the Bees Algorithm is employed to train three artificial neural networks (ANNs) to model the inverse kinematics of the joints of a three-link manipulator. In the second case, the Bees Algorithm is used to optimise the parameters of a linear model used to approximate the torque output for an electro-hydraulic load system. In both cases, the Bees Algorithm outperformed the state-of-the-art in the literature, proving to be an effective optimisation technique for engineering systems.

Adaptive extended state observer-based flatness nonlinear output control for torque tracking of electrohydraulic loading system

Electrohydraulic loading system is a torque servo system with high-accuracy and high-frequency response. In this paper, an adaptive extended state observer-based flatness nonlinear output control is proposed to improve the torque tracking performance of electrohydraulic loading system. This method combines a flatness concept, expected state, adaptive extended state observer and system output to develop a stable control system. Expected input feedforward based on the flatness property is designed to provide model compensation for bandwidth enhancement. An adaptive extended state observer is proposed to estimate the unmeasured states and the unmodeled dynamics. Based on estimated states and disturbances, state feedback control is developed to ensure the stability of closed-loop system, and to improve torque tracking accuracy and system robustness. The stability of the closed-loop system is proved by the Lyapunov stability theory. Extensive experiments were carried out to verify the performance of high-accuracy tracking of the proposed control strategy.

Fuzzy PID Control and SIMULINK Simulation of Electro Hydraulic Proportional Relief Valve Loading System

This paper mainly studys the open valve control hydraulic motor loading system.For the electro hydraulic proportional relief valve loading system, the electro hydraulic proportional relief valve and the quadratic component DS1 are modeled, then the mathematical model of the electro hydraulic proportional relief valve loading system is obtained. The dynamic and steady state characteristics of the loading system are stabilized by fuzzy PID control technique. Finally modeling and Simulating the electro-hydraulic proportional relief valve loading fuzzy PID control system by SIMULINK.

Hybrid Robust Control Law with Disturbance Observer for High-Frequency Response Electro-Hydraulic Servo Loading System

Addressing the simulating issue of the helicopter-manipulating booster aerodynamic load with high-frequency dynamic load superimposed on a large static load, this paper studies the design of the robust controller for the electro-hydraulic loading system to realize the simulation of this kind of load. Firstly, the equivalent linear model of the electro-hydraulic loading system under assumed parameter uncertainty is established. Then, a hybrid control scheme is proposed for the loading system. This control scheme consists of a constant velocity feed-forward compensator, a robust inner loop compensator based on disturbance observer and a robust outer loop feedback controller. The constant velocity compensator eliminates most of the extraneous force at first, and then the double-loop cascade composition control strategy is employed to design the compensated system. The disturbance observer–based inner loop compensator further restrains the disturbances including the remaining extraneous force, and makes the actual plant tracking a nominal model approximately in a certain frequency range. The robust outer loop controller achieves the desired force-tracking performance, and guarantees system robustness in the high frequency region. The optimized low-pass filter Q(s) is designed by using the H∞ mixed sensitivity optimization method. The simulation results show that the proposed hybrid control scheme and controller can effectively suppress the extraneous force and improve the robustness of the electro-hydraulic loading system.

Nonlinear adaptive torque control of electro-hydraulic load system with external active motion disturbance

This paper develops a high performance nonlinear adaptive control method for electro-hydraulic load simulator (EHLS). The tracking performance of EHLS is mainly affected by the following factors: actuator’s active motion disturbance, flow nonlinear and parametric uncertainties, etc. Most previous studies on EHLS pay too much attention on actuator’s active motion disturbance, while deemphasize the other two factors. This paper concerns EHLS as a motion loading system. Besides actuator’s motion disturbance, both the nonlinear characteristics and parametric uncertainties of the loading system are addressed by the present controller. First, the nonlinear model of EHLS is developed, and then a Lyapunov-based control algorithm augmented with parameters update law is developed using back-stepping design method. The stability of the developed control algorithm is proven via Lyapunov analysis. Both the co-simulation and experiment are performed to validate the effectiveness of the developed algorithm.

A case study of electro-hydraulic loading and testing technology for composite insulators based on iterative learning control

In order to simulate the vibrating condition of composite insulators in breeze, and carry out its fatigue test under loading and vibrating conditions, the electro-hydraulic loading and testing technology for the composite insulators is researched in this study. A compound electro-hydraulic loading system is first designed, including two subsystems, the static proportional loading system and the dynamic servo loading system. Then, the working principle based on this system is analyzed, and the mathematic model of electro-hydraulic servo system is also built, proved to be an inertial element with high gain. The control method based on proportional–derivative-type iterative learning control has been applied to such a dynamic servo loading system, to achieve the high-precision control for dynamic load force with repetitive regularity. Both mathematic simulation and actual experiments have been designed and carried out, and their results proved that the load principle and the control method are feasible and applicable and have the ability of achieving high-precision control effects. Based on this discussed electro-hydraulic technology, an actual electro-hydraulic loading and testing system for different kinds of composite insulators has been researched and developed, with the advanced technology indices of six loading channels, 20 kN maximum dynamic force, 0.3 kN force control precision and 100 Hz maximum vibrating frequency.

Application of Direct Actuated Digital Servo Valve in Electrohydraulic Static Loading System

Structure static testing is an important means to study the static characteristic of complex engineering structure. Electrohydraulic stactic loading system is the singnificant equipment of the testing. With its function of transfering low-power electrical singal to large-power hydraulic output quickly and precisely, the servo valve plays a key role in an electrohydraulic servo control system and dominates to a large extent the performance of the whole control system. Conventional electrohydraulic servo or proportional control is subject to the nonlinearites of their electro-mechanical interface, such as hysteresis, saturation and finite resolution. In this paper, a direct actuated digital servo valve was applied in electrohydraulic static loading system. It can be driven directly by computer needn’t D/A and has the advantages of simple structure, high tolerance to contamination and high reliability. Practical load-experiment results show that the static loading system with a direct actuated digital servo valve can work steadily and reliably and possess high accuracy and fast response.

The Application of Electrohydraulic Proportional Technology in Mill Loading System

The paper designs electrohydraulic proportional loading system which meets the adaptive requirements of variable loading for the system by analyzing the structure and the theory of mill loading system. After being reformed, the adaptive control ability to the changes of coal’s quality and quantity is improved which guarantees the fineness of coal, strengthens remote control ability, increases the degree of automation, the efficiency and the production of the system and saves energy.

Experimental Equipment Research on Uniaxial Compression Stress-Strain Curve of Concrete

The constitutive relation of concrete under uniaxial compression is the essential theoretical basis for structural analysis of concrete. Because of lack of sufficient stiffness for ordinarily tester, stable falling branch of stress-strain curve cannot be obtained. The common methods to increase rigidity of loading system include direct and indirect method. The condition of realizing the stress-strain complete curve for concrete uniaxial compression is derived. A set of stiffness experimental equipment is designed by using the indirect method, which has the advantages of simple, dependable and strong adaptability. Experiment shows that stress-strain complete curve of uniaxial compression under different strain rate could be achieved by using this equipment and electro-hydraulic loading system of MTS co. ltd. It will lay foundation for putting forward the stress-strain curve equation of uniaxial tension and compression under considering the effect of strain rate. It can provide theoretical basis for structural analysis of concrete.

Sand Liquefaction Due to Irregular Excitation

ABSTRACT An electro hydraulic servo type loading system was incorporated into the conventional triaxial shear test apparatus so that any desired form of load pattern can be applied to soil specimens. In applying this system to the study of liquefaction of saturated sands, a difficulty was encountered in keeping the applied stress perfectly controlled even after the rigidity of the sample falls considerably due to the onset of liquefaction. The use of an elastic joint in the loading ram proved very useful to overcome this defect. The acceleration records obtained at the time of the Niigata earthquake of 1964 were used as input load patterns to be applied to saturated specimens of a Niigata sand. The investigation disclosed several features of interest concerning the behaviors of the sand when subjected to irregular exitation.

An automated test facility for rock mechanics research

This paper describes the design, development and operation of a newly completed test facility in the Department of Mining Rock Mechanics Laboratory at The Pennsylvania State University. The facility contains an electronically programmed electro-hydraulic loading system capable of developing compressive and tensile loads of up to 200,000 and 120,000 lb respectively. Programming facilities available make it possible to carry out creep, stress relaxation and fatigue studies as well as experiments under controlled rates of loads strain and deformation. Two hydraulic power supplies are included for developing confining and pore (internal) pressures during triaxial loading experiments. Facilities are available for monitoring strains, loads, pressures and temperatures; these include a digital data acquisition system capable of monitoring up to 200 channels of experimental data at a rate of 20 channels/sec, and three dual-channel strip chart recorders and an X-Y plotter which allow continuous recording of selected variables. The overall facility has been developed for routine use by faculty and graduate students. Although considerable time and effort have been expended in designing the facility, it is expected that the convenience and reliability inherent in such a facility will accelerate rock mechanics research many fold. Research projects presently utilizing the new facilities include studies of incremental creep, and fatigue in geologic materials.