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Energy regeneration and reutilization comprise an important energy-saving technology for mobile machinery. The diversity of mobile machinery applications has stimulated the need for a model-based optimization approach, which helps manufacturers assess the market feasibility of various energy-saving architectures, and determine the best trade-off solution for specific applications. In this paper, a model-based comprehensive optimization approach (COA), involving control, sizing, efficiency, and economic performance, is proposed for an electro-hydraulic energy-saving system (EHESS). Compared with a conventional system, EHESS with optimal design parameters (control and sizing) obtains a maximum fuel-saving rate of 15.6% and an annualized investment income rate of 125.7%. The COA is a useful procedure for assessing the system efficiency and market competitiveness of new energy-saving products.

A new joining process, named Electro-Hydraulic Clinching (EHC) is presented. In this process, electrical energy stored in a pulse generator is suddenly discharged between the electrodes submerged in a fluid and initiate a shock wave in the fluid. The shock wave propagates through the fluid and forms the sheets to the clinching die cavity and creates a joint between them. To investigate the capabilities of the presented method, the EHC process was applied for hole clinching of AA3105/Ck67 sheets with 0.5 mm thicknesses. The influence of process parameters on the quality of the joint was determined. Also, single lap shear and peel tests were performed on the specimens to investigate the joint strength and the mechanical behavior of the joints. According to the accomplished results, the utilization of this joining process increases the strength of the joint and the joint efficiency of the present method is about two times of other clinching methods.

The aim of this study is to improve the reasonability of electro-hydraulic servo loading controlling design and enhance motor performance. Therefore, the electro-hydraulic servo loading controlling and multiple-objective optimisation design method for the intelligent water drop algorithm (IWD), which is based on a two-phase weight balance and multiple-objective, is proposed. First, research is conducted on the electro-hydraulic servo loading controlling design by selecting two indexes to carry out the object design. Second, the two-phase multiple-objective IWD algorithm is designed; in the first phase, two knowledge bases are adopted for the IWD swarm position initialisation, namely, IWD flying direction designation and reference point storage. In the second phase, the weighted equalisation method is adopted to reform the optimised intensive search process, to ensure the diversity of IWD algorithm swarm and reference point position to enhance the search performance. Finally, the effectiveness of the proposed method is validated through a simulation experiment.

For accurate force tracking of an electro-hydraulic servo system (EHSS), this paper presents a state-space representation of model predictive control (MPC). EHSS is highly nonlinear because of the transmission nonlinearities, variations of the trapped fluid volume, internal friction, and nonlinear load-based nonlinearities. A nonlinear mathematical model is built, and model parameters are identified using a grey-box system identification method. Then MPC is firstly designed, and to improve the robustness, a nominal mathematical model with proportional integral control (PIC) is constructed for MPC design. Three implementation scenarios are investigated in MATLAB/Simulink and real-time LabVIEW-based experimental rig. The control performance is compared between and among PIC, MPC, and hybrid MPC–PIC controller.

An adaptive-gain super-twisting sliding mode observer is proposed for fault reconstruction in electro-hydraulic servo systems (EHSS) receiving bounded perturbations with unknown bounds. The objective is to address challenging problems in classic sliding mode observers: chattering effect, conservatism of observer gains, strong condition on the distribution of faults and uncertainties. In this paper, the proposed super-twisting sliding mode observer relaxes the condition on the distribution of uncertainties and faults, and the gain adaptation law leads to eliminate observer gain overestimation and attenuate chattering effects. After using the equivalent output-error-injection feature of sliding mode techniques, a fault reconstruction strategy is proposed. The experimental results are presented, confirming the effectiveness of the proposed adaptive super-twisting observer for precise fault reconstruction in electro-hydraulic servo systems., Comment: Final version

The formability of electro-hydraulically formed AA5182-O aluminium sheet was investigated by means of experimental testing and numerical modelling. The experimental results were compared with quasi-static, as-received forming limit curve (FLC) and were used to calibrate a finite element model of EHF. It is found that the formability improvement of AA5182-O sheets was insignificant when electro-hydraulically formed without a die. However, when specimens were electro-hydraulically formed with sufficient energy into 34 or 40° conical dies, the effective strain measured in safe grids increased by 40 and 70% respectively when compared with a conservative quasi-static FLC. Finite element simulation results suggested that a combination of different mechanical parameters contributed to the formability improvement. The increased strain rate in areas close to the apex of the speimen, the negative stress triaxiality just before specimens contact the die, and significant compressive through-thickness stress generated by high-velocity impact all contributed to the improvement of formability in electro-hydraulic die forming.

An electro-hydraulic actuation system with critically lapped servovalve and pressurized return line is exposited. The dynamic equations governing the behavior of various components are explained; using these nonlinear equations, a simulation model is developed in Simulink® software for the purpose of controller design and verification. Model requires very small integration step size as the equations involved are stiff. A relationship between the various pressures in the system is derived, and a simplified method for the nonlinear modeling of electro hydraulic actuating system is developed using these relationships. The simplified model is computationally efficient as the integration step-size is large compared to the original model. The computationally efficient model finds application in real-time hardware-in-loop simulation (HILS).

Electro-hydraulic servo-valves, which are considered as the crucial core element of digital electric hydraulic control system, are widely applied in thermal power plants. In this paper, motivated by the long stable operation of thermal power plant, an abnormal blockage failure of the electro-hydraulic servo valve in digital electric hydraulic control system of 125 MW thermal power plant was investigated systematically. Three body abrasive wear was identified as the main failure mechanism. Comprehensive analysis results finally revealed that the unqualified material of the valve spool with abnormal coarse carbides caused by improper preparation process was ascribed to be the root cause of the failure. During the operation, the abnormal coarse carbides acted as stress concentration source and were peeled off from the valve spool under the effect of the friction between the feedback wire and the valve spool. After that, the exfoliated carbides served as third bodies, resulting in three body abrasive wear. In this process, some of the carbides with size exceeding 5 μm driven by fire-resistant oil entered the clearance between the valve spool and the valve sleeve, leading to the abnormal blockage failure since the maximum allowable clearance was 5 μm. Countermeasures were then proposed to address corresponding problems. Considering that practical failure of the electro-hydraulic servo-valves is seldom reported before, the finding of the paper could be helpful for better understanding the failure mechanisms of the electro-hydraulic servo-valves under actual service conditions.

The objectives of this paper are to quantify the increase in formability of DP600 steel sheets in electrohydraulic die forming (EHDF). The conventional (quasi-static) and high strain rate forming limits of this sheet material were experimentally obtained from specimens deformed using Marciniak tests and EHDF tests, respectively. A numerical model of EHDF was developed in order to determine the strain path of sheet metal experiencing large strains. Forming limits obtained from EHDF specimens formed in plane strain into a V-shaped die indicated that, locally near the top edge of the specimen, more than 120% formability improvement was achieved. Moreover, a formability enhancement of more than 60% was achieved in EHDF in biaxial tension using a conical die, provided sufficient discharge energy was applied. It was found that the significant increases in formability in EHDF are associated with the high-velocity impact against the die wall and the consequent high effective strain rate.

Hierarchical control architectures are a common approach when hydraulic systems are under study; provided their multi-domain nature, the control scheme is commonly split into different hierarchical levels each one associated with a particular physical domain. This paper presents the application of a model-based control structure called Embedded Model Control (EMC) when a hierarchical scheme is implemented on an electro-hydraulic proportional valve. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed loop bandwidth close to 1 kHz. The outer loop is a position tracking control, in charge of the accurate positioning of the spool with respect to valve openings. The paper addresses the outer loop, i.e., the tracking of mechanical spool position by using the EMC. Analysis and synthesis are presented as well as experimental results obtained from a test rig provided by an industrial manufacturer.

Electro hydraulic servo valves, which are used to transform weak electric signals into high power hydraulic energy, are the crucial part of digital electric hydraulic control system. In this paper, inspired by the safety operation of the digital electric hydraulic control system, an unexpected leakage failure of the electro-hydraulic servo valve in the digital electric hydraulic control system of 300 MW thermal power plant was studied in depth. Systematical analysis results finally revealed that this unexpected failure was caused by pitting corrosion induced by chloride ions, which are initiated from improper cleaning agent containing trichloroethane. It reacted with the phenolic compounds came from the degradation of the fire-resistant oil, giving rise to the production of the chloride ions. Passive film on the contacting surface was then destroyed by the chloride ions, leading to the formation of naked areas where the pitting corrosion occurred. After that, the coarse carbides with size exceeding 5 μm in the naked areas were peeled off from the contacting surface under the effect of the pitting corrosion, resulting in the blockage of the servo valve since the maximum allowable clearance between valve spool and valve sleeve was 5 μm. This eventually hindered the movement of the valve spool and caused the unexpected leakage failure. Considering that the failure of the electro-hydraulic servo-valves caused by corrosion is seldom reported before, the achievement of the paper could enhance the understanding of the failed mechanism of the electro hydraulic servo valves under actual service condition.

The traditional efficiency analysis method of hydraulic system generally neglects the influence of mechanical nonlinearity, which causes great difference between theoretical efficiency optimization and actual application. This will reduce the energy-saving effect. In this paper, the electro-hydraulic servo steering system (EHSSS) of heavy vehicles is taken as the research object. Considering both mechanical nonlinearity and hydraulic nonlinearity of the steering system, this paper establishes the efficiency model of the EHSSS. In order to achieve the efficiency analysis of this nonlinear model, an efficiency analysis method in quasi-steady state condition is proposed. The theoretical analysis is consistent with the experimental results in four different single-side loading conditions, so the validity of the model and method is verified. Then, based on the above model and method, the system efficiency spectrums are obtained in different operating conditions. The efficiency of the EHSSS with strong nonlinearity is not only related to the equivalent load but also the steering angle. The results show that the efficiency is the highest in the maximum equivalent load conditions and at left or right end points. In addition, this paper obtains the efficiency curves of steering system in different speeds, hydraulic parameters and structural parameters. The method presented in this paper takes into account the effect of mechanical nonlinearity on the efficiency, which provides theoretical guidance for further efficiency improvement of electro-hydraulic steering system.

Many studies focused on casing collapse strength under uniform load have been done, and the API 5C3 and ISO standards have been formed. However, only a limited number of researches on collapse failure mechanism of casing have been done under non-uniform load, especially experimental study, although the non-uniform load has a great impact on casing collapse strength. Hence, the collapse experiment is conducted for P110SS casing under opposed line load by using electro hydraulic servo pressure testing machine. The displacement variation rules of P110SS casing have been obtained under opposed line load. The strain of casing is measured in the process of collapse testing by the method of gluing strain-gauge on the outside surface of P110SS casing. The initial yield load of casing, instability load of casing and the yield load, stress-hardening rate, strain-hardening rate of casing after hardening are obtained. The stress-strain rules of casing after hardening are analyzed. The hardening characteristic and collapse failure mechanism of P110SS casing have been clarified under non-uniform load (under opposed line load). Experimental results can provide important references for the theoretical study on failure mechanism and collapse strength of casing under non-uniform load.

The scavenging system in two stroke engine is very important, therefore an electro-hydraulic camless variable valves actuation is developed and the effect of the exhaust valve character change on HFPE engine performance is investigated. Firstly the HFPE working principle and the control strategy are analyzed, and then a 3D CFD model is built by AVL_FIRE software, the piston displacement is obtained by 0D simulation. The simulation results are verified by the ideal scavenging model. The specific distributions of flow field are by plane cut. Further the scavenging parameters, such as trapping ratio, delivery ratio and scavenging efficiency, are analyzed with different intake pressure. In order to optimize the scavenging performance, the scavenging efficiency is affected by intake port height and the exhaust valve timing. Therefore the laws of higher scavenging efficiency are obtained. Experiment is necessary for validating the electro-hydraulic camless variable valves actuation system design. The specific prototype test bench is introduced for experimental study. In addition, the factors that affect variable valves actuation system are tested. Finally, the engine operation results are obtained and the engine performance is analyzed further.

This paper presents robust control of Electro-Hydraulic Servo System. Higher order sliding mode controllers are examined using standard Super-Twisting Algorithm (STA) and Generalized Super-Twisting Algorithm (GSTA). A novel sliding surface is considered. The control is synthesized using STA and GSTA. Methods are demonstrated in simulations. A comprehensive comparison is presented.

The proportional-integral-derivative (PID) controller are widely applied with the electro-hydraulic servo system since it is easily to implement and highly efficient. The optimal tuning PID parameter that can increase the performance of the control system. Thus, this paper is considered the optimization technique of Genetic Algorithm (GA) for tuning PID controller parameter for electro-hydraulic servo system. The other techniques are compared, that is the obtained results are shown the genetic algorithm optimized PID controller provide an improved closed-loop are performed than the Ziegler- Nichols, tuning method automatic tuning method and particle swarm optimization (PSO).

Electro-hydraulic pumps (EHP) possess the advantages of integrated structure and high working efficiency, which thereby attract widespread attention. For the purpose of airborne deployment, an axial piston pump based EHP is established in this work. The modeling of the EHP is carried out in detail considering its structure and working principle via AMESim. Specifically, the model is performed on the basis of three aspects, which are electromagnetic driving, mechanical transmission and fluid dynamic. The computational simulation is conducted based on the modeling. Further, the prototype is designed and machined for working performance evaluation. The properties under different configurations of the EHP are investigated by experiments. Experimental results indicate that the proposed EHP provides a decent working performance in line with the modeling and simulating. The effectiveness of the EHP is verified and the scheme for further improvement is presented.

This paper presents a coordinated control strategy of electro-hydraulic braking for distributed electric vehicles. To meet braking regulations requirements in conjunction with the characteristic of the in-wheel motor and power battery, the feasible region of the maximum regenerative braking torque and the evaluation indexes of the electro-hydraulic braking are proposed. In order to realize the optimal objective of energy regeneration and braking stability, the coordinated control of electro-hydraulic braking can be taken as a global distribution problem of two braking torques — hydraulic and regenerative. The optimal distribution coefficients are achieved by the genetic algorithm (GA) under different braking conditions. Moreover, the braking intention of the driver is integrated into the weight coefficients to achieve a dynamic distribution. The results of simulation show that the proposed strategy not only has better performance of energy regeneration and braking stability than I curve distribution, but also satisfies the characteristics of the driver’s braking behavior under corresponding situations.

This paper proposes an almost disturbance decoupling (ADD) control strategy for solving the force control problem of an electro-hydraulic load simulator containing mechanical backlash. This method can enhance the force tracking performance of the load simulator by decoupling position disturbance and mitigating the backlash effect. Based on a proposed disturbance coupled model of the load simulator, the necessity of adopting the ADD control is explained by the mechanical oscillation analysis with a simple controller under different disturbance situations. Then, the design method and tuning parameters of the ADD controller are discussed. With the ADD controller, the system’s input-to-state stability with respect to disturbance signals is guaranteed, and moreover, the boundary and the convergence speed of the force tracking error are adjustable by tuning the controller parameters. Both simulation results and experimental results demonstrate that the proposed ADD control can achieve much higher force tracking performance than a controller commonly used in industry.

In order to enhance the anti-jamming ability of electro-hydraulic position servo control system at the same time improve the control precision of the system, a compound control strategy that combines velocity compensation with Active Disturbance Rejection Controller (ADRC) is proposed, and the working principle of the compound control strategy is given. ADRC controller is designed, and the extended state observer is used for observing internal parameters uncertainties and external disturbances, so that the disturbances of the system are suppressed effectively. Velocity compensation controller is designed and the compensation model is derived to further improve the positioning accuracy of the system and to achieve the velocity compensation without disturbance. The compound control strategy is verified by the simulation and experiment respectively, and the simulation and experimental results show that the electro-hydraulic position servo control system with ADRC controller can effectively inhibit the external disturbances, the precise positioning control is realized after introducing the velocity compensation controller, and verify that the compound control strategy is effective.

In this paper, a special composite hydraulic cylinder, which includes two pistons and three working chambers, is proposed for driving the insulator fatigue test device. In this force loading system, a servo valve and a proportional pressure valve are used to control the composite hydraulic cylinder to generate alternating force and fixed force respectively. Furthermore, the models of the electro-hydraulic system are built and its dynamic characteristic is analyzed based on the models. Considering the uncertainty of the model parameters, the fractional order proportional-integral-derivative controller is adopted to control the two valves. The Oustaloup method is used to discrete the fractional order controller and the iteration feedback tuning method is presented to tune the controller parameters. The tuning process which is independent on the system model can be done on the close loop system. Simulation and experimental results have shown that the fractional order controller is effective.

This paper presents an observer-based sliding mode control concept with chattering reduction, generally applicable for position tracking control of electro-hydraulic valve-cylinder drives (VCD's). The proposed control concept requires only common data sheet information and no knowledge on load characteristics. Furthermore the proposed scheme only employ ***piston-and valve spool positions- and pressure feedback, commonly available in industry. The main target is to overcome problems with linear controllers deteriorating performance due to the inherent nonlinear nature of such systems, without requiring extensive knowledge on system parameters nor advanced control theory. In order to accomplish this task, an integral sliding mode controller designed for the control derivative employing state observation is proposed, based on a generalized reduced order model structure of a VCD with unmatched valve flow- and cylinder asymmetries. It is shown that limited attention can be given to bounds on parameter estimates, that chattering is reduced and the number of tuning parameters is reduced to the level seen in conventional PID schemes. Furthermore, simulation results demonstrate a high level of robustness when subjected to strong perturbations in supply pressure and coulomb friction force, and that tracking accuracy may be reduced to the level of noise. Furthermore, the proposed controller tolerates significant noise levels, while still remaining stable and accurate.

The paper focuses on developing a microcontroller-based automated system to replace the conventional PLC. The operation of the proposed system is similar to PLC with better performances in reducing time delay using fast switching transistors. The system was tested in controlling the electro pneumatic and electro hydraulic devices and resulting in the faster time response and stable duty cycle.

The working principle, failure modes and failure causes of the jet pipe servo valve has been analyzed. Get the main failure modes of the servo valve, which is caused by wear. The influences of the arris edge geometric error on the performance of the servo valve been analyzed. Get the wearing capacity equal to the edge arris geometric error. It provides an estimation method of the arris edge geometric error, which could be use to analysis the wearing capacity of the servo valve.

Automotive engineers are continuously exploring various transmission technologies to increase vehicle performance, fuel economy and safety. The most common control devices inside the transmission are hydraulic actuated clutches. In this paper a state-space model for a wet clutch actuated by an electro-hydraulic valve used by Volkswagen for automatic transmission is presented. The developed model was implemented in Matlab-Simulink and was validated against the data obtained from a test bench provided by Continental Automotive Romania. The simulations are very similar to the experimental data proving that the modeling approach is suitable to this kind of clutch actuated by an electro-hydraulic pressure reducing valve.

This article, in order to precisely impose friction on aircraft and weapon actuation systems, presents a new friction loading method characteristic of “torque-zero velocity” switching control with an electro-hydraulic load simulator. As the general Stribeck friction model has little related to static friction, it proposes a “torque-zero velocity” switcher, in which a zero-velocity controller is developed to load the static friction and a torque controller the kinetic friction. With the help of mathematical modeling, this article designs a “torque-zero velocity” switching controller and, correspondingly, provides a “dual-threshold judgment” algorithm. Simulation results indicate that the proposed method can be successfully used to carry out the static and kinetic friction simulation with an electro-hydraulic load simulator.

Objective: Flexible ureteroscopy is nowadays an alternative effective option for treatment of upper urinary tract stones, especially in the lower renal pole. Access in this case is often limited by active deflection capabilities of the instrument which is always deteriorated by the passage of different tools through the working channel. Insertion of them limits also the irrigation flow and so that the visibility. These deteriorations vary largely following the tool inserted. We performed an in vitro evaluation of deterioration of active deflection, possibility of tool insertion in maximal active deflection and irrigation flow in 6 different flexible ureteroscopes with almost all of tools available. Methods: A total of 546 measures of maximal deflection, test of passage of tools in maximal deflection and measures of irrigation flow passage through the working channel were made on 6 different ureteroscopes, the ACMI DUR-8, the ACMI DUR-8 "Elite", the Karl Storz 11274 AA, the Karl Storz 11278 AU1 "Flex-X", the Wolf 7325.172 and the Olympus URF/P-3 without any tool inserted and with 22 different tools (14 extraction devices and 8 lithotripsy probes). Results: Larger caliber tools resulted in more deflection degradation than smaller ones but it is more evident in case of use of non-nitinol tools instead of the nitinol ones. Generally lithotripsy probes affected active deflection more than nitinol extractions tools but different brand laser fibres present different results. Usually 1.6 and 1.9F electro hydraulic probes offer a slightly better deflection than does the 200μ laser fibre. Ballistic shock probes are so stiff that can not be used for treating lower renal pole stones. Conclusions: An array of different instruments are nowadays available for upper renal endoscopic treatment but they differ largely on stiffness and on obstruction to irrigation flow. Laser probes are very problematic to insert in the already deflected instruments, something that is less evident with the EHL probes and the smaller nitinol extraction tools. Irrigation flow is inversely proportional to the diameter of the tool inserted. Tools with a diameter of 3 French or more block totally the flow.

The large size of the cab of an electro-hydraulic elevator necessitates the arrangement of two cylinders located symmetrically on both sides of the cab. This paper reports the design of an electro-hydraulic system which consists of three flow-control proportional valves. Speed regulation of the cab and synchronization control of the two cylinders are also presented. A pseudo-derivative feedback (PDF) controller is applied to obtain a velocity pattern of the cab that proves to be close to the given one. The non-synchronous error of the two cylinders is kept within ±2 mm with a constrained step proportional-derivative (PD) controller. A solenoid-actuated non-return valve, i.e. a hydraulic lock, is also developed to prevent cab sinking and allow easy inverse-fluid flow.

Lighter railway vehicles are going to become the norm in the future as the operator pushes towards a more economical operation. This paper looks into ways of applying classical control methods using “skyhook damping” to minimise the flexibility effects that arise as a consequence of having lighter vehicles, and in particular includes the effects of real actuator dynamics. Two and three actuators schemes are considered: two of them are located at the front and rear secondary suspension pivot points, with a third actuator at the centre of the vehicle primarily targeted at reducing the effects of the main bending mode of the vehicle body. Hydraulic actuators are used at the front and rear while an electro-magnetic actuator is connected to the centre of the vehicle.

A multivariable controller, applicable to coupled multi-channel servosystems, is described. The controller is designed from an estimated matrix fraction description plant model, and allows the channels to be decoupled with individually specified pole positions. The controller is applied to a two-channel electro-hydraulic servosystem, and demonstrates a significant reduction in interaction compared to non-decoupling controllers.

Three methods are proposed by which nonlinear dynamic technical systems may be approximated by state quadratic systems. The quadratic approximation can be a considerable improvement over the linear and bilinear approximation for some nonlinear dynamic systems. The practical application involves a parameter identification method to identify continuous quadratic models in observer normal form for a real plant, am electro-hydraulic drive.

The paper reviews some specific aspects encountered in the design and optimisation of the particular software required by the automatic digital control of an electro-hydraulic system, which is used in an industrial robot. A direct digital control structure based upon a microprocessor hardware organisation of the control unit is found to be most profitable. The influence of certain time-delays, of inevitable approximation errors, and of the sampling rate on the overall system performance is then investigated by means of a computer-aided simulation method ; this one also offers the necessary background for the control software optimization. Also briefly discussed is the manner in which the microprocessor handles the potentially dangerous or damaging situations.

The paper describes the preparation of a dynamic model required for simulation of a 30 kW electro-hydraulic system used to induce controlled vibration of a wide range of components, machines or structures. The vibrator system is associated with a 28 tonne seismic block. The model is highly detailed to allow study of the system to its dynamic performance limits of around 300 Hz. The model consists of nearly eighty equations some of them nonlinear and discontinuous. The paper describes the orderly development of the model emanating from the bond graph approach. Some simulation results, with limited experimental correlation, are included.

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.