Most recent studies on adaptive hydraulic tracking control focus on the trajectory tracking performance while the parameter convergence property is often unsatisfying. This article proposes a ...composite learning adaptive position tracking controller with improved parameter convergence for electro-hydraulic servo systems. In the composite learning, a prediction error is formulated to exploit input-output memory data, and parameter estimates are driven simultaneously by tracking and prediction errors. Practical exponential stability of the closed-loop system, which implies the convergence of both the tracking and parameter estimation error, is established by a more realizable interval-excitation condition than the stringent persistent-excitation condition. Therefore, superior trajectory tracking is obtained compared with the classical adaptive hydraulic control. Besides, the initial fluid control volumes of hydraulic systems are assumed to be unknown a priori , which enhances the generality of the proposed control approach. The abovementioned two properties are generally not achievable in prevalent approaches to adaptive hydraulic control. Moreover, noisy acceleration signals and the time derivatives of pressure signals are not needed in the proposed approach, which improves its robustness against measurement noise. Extensive experimental results verify its superiority over currently available ones.
Journal of Hydraulic Research Closure to "On analytical formulae for navigation lock filling-emptying and overtravel" by LAURENT SCHINDFESSEL, TOM DE MULDER, STEPHAN CREELLE and GERALD A. SCHOHL, J. ...Hydraulic Res. 53(1), 2015, 134-148
Journal of Hydraulic Research Closure to "Experimental study on the flow characteristics of unstructured block ramps" by SIMONA TAMAGNI, VOLKER WEITBRECHT and ROBERT M. BOES, J. Hydraulic Res. 52(5), ...2014, 600-613
Journal of Hydraulic Research Closure to "Semi-analytical model for temporal clear-water scour at prototype piers" by JUNKE GUO, Journal of Hydraulic Research, 52(3), 366-374
Pump-controlled hydraulic cylinder drives may offer improved energy efficiency, compactness, and plug-and-play installation compared to conventional valve-controlled hydraulic systems and thus have ...the potential of replacing conventional hydraulic systems as well as electro-mechanical alternatives. Since the late 1980s, research into how to configure the hydraulic circuit of pump-controlled cylinder drives has been ongoing, especially in terms of compensating the uneven flow requirements required by a differential cylinder. Recently, research has also focused on other aspects such as replacing a vented oil tank with a small-volume pressurized accumulator including the consequences of this in terms of thermal behavior. Numerous references describe the advantages and shortcomings of pump-controlled cylinder drives compared to conventional hydraulic systems or electro-mechanical drives. This paper presents a throughout literature review starting from the earliest concepts based on variable-displacement hydraulic pumps and vented reservoirs to newer concepts based on variable-speed electric drives and sealed reservoirs. By classifying these drives into several proposed classes it is found that the architectures considered in the literature reduce to a few basic layouts. Finally, the paper compares the advantages and shortcomings of each drive class and seek to predict future research tasks related to pump-controlled cylinder drives.
•A layered fusion model characterized by three-layer structure is designed.•Personalized sample sets are structured to solve information redundancy.•DSmT is used to fuse the decision of multiple ...classifiers.•Multiple faults in different fault groups of hydraulic valves are detected.
Fault identification in hydraulic valves is essential in maintaining the reliability and security of hydraulic systems. Due to the nonlinear characteristics of hydraulic systems under noisy working conditions, it is difficult to extract fault features from vibration signals collected from the surface of the valve body. Therefore, a DSmT-based three-layer method using multi-classifier is proposed to detect multiple faults occurred in hydraulic valves. Firstly, the raw signals are personalized to construct the training samples and the unknown testing samples. Secondly, a three-layer structure of the hybrid model called the layered hybrid model is constructed, which is suitable for hydraulic valves to detect the faults of different fault groups (including coil fatigue in the actuator and the abrasion inside the valve) and improve the diagnosis accuracy obviously. Finally, classification methods are selected to classify fault groups in the first two layers, and then the fault types are identified in the third layer by the fusion results using the Dezert-Smarandache Theory (DSmT). Experimental investigations are performed to validate the performance of the present method using a hydraulic valve (solenoid controlled pilot operated directional valve) controlled the hydraulic test rig. The results show that the average accuracy of detecting twelve types of faults is about 98.1%, which are better than those using other methods. It is expected that the present DSmT-based three-layer method using multi-classifier can be applied to more complex hydraulic systems.
This paper concerns high-accuracy tracking control for hydraulic actuators with nonlinear friction compensation. Typically, LuGre model-based friction compensation has been widely employed in sundry ...industrial servomechanisms. However, due to the piecewise continuous property, it is difficult to be integrated with backstepping design, which needs the time derivation of the employed friction model. Hence, nonlinear model-based hydraulic control rarely sets foot in friction compensation with nondifferentiable friction models, such as LuGre model, Stribeck effects, although they can give excellent friction description and prediction. In this paper, a novel continuously differentiable nonlinear friction model is first derived by modifying the traditional piecewise continuous LuGre model, then an adaptive backstepping controller is proposed for precise tracking control of hydraulic systems to handle parametric uncertainties along with nonlinear friction compensation. In the formulated nonlinear hydraulic system model, friction parameters, servovalve null shift, and orifice-type internal leakage are all uniformly considered in the proposed controller. The controller theoretically guarantees asymptotic tracking performance in the presence of parametric uncertainties, and the robustness against unconsidered dynamics, as well as external disturbances, is also ensured via Lyapunov analysis. The effectiveness of the proposed controller is demonstrated via comparative experimental results.
Valve-controlled electro-hydraulic technology is widely used in heavy-duty linear actuator, but its energy efficiency is low. The electro-mechanical actuator (EMA) has high energy efficiency, but its ...output force is small. In order to achieve high efficiency, high power-to-weight ratio, and high performance linear drive, a hydraulic-electric hybrid linear drive principle integrating hydraulic cylinder and EMA is proposed, and a prototype of electromechanical hydraulic hybrid actuator (EMHA) is designed and developed. In the hybrid drive system, EMA is responsible for actuator motion control and hydraulic cylinder is used for force control. In the study, an extended state observer (ESO) was first designed to estimate the external load torque of the EMA permanent magnet synchronous motor (PMSM) in real time. Combining the detected pressures, the load force of the EMHA can be estimated. Then, according to the estimated load force, the hydraulic system is controlled to make the hydraulic cylinder balance most of the actuator load force, maintaining the PMSM within the required load range. A sliding-mode controller is further designed to compensate the external load torque acting on the PMSM to ensure that the system has good motion control characteristics. The results show that under the same driving force and velocity, the power density of the EMHA is 154% higher than that of the EMA. In this article, the proposed system can achieve equivalent control performance as the valve-controlled system, while reducing energy consumption by 58%.
Abstract
Many arachnids use internal hemolymph pressure to actuate extension in their leg joints. The inherent large foot displacement‐to‐body length ratio that arachnids can achieve through ...hydraulics relative to muscle‐based actuators is both energy and volumetrically efficient. Until recent advances in nano/microscale 3D printing with two‐photon polymerization (2PP), the physical realization of synthetic complex ‘soft’ joints would have been impossible to replicate and fill with a hydraulic fluid into a sealed sub‐millimeter system. Inspired by nature, the smallest scale 3D‐printed hydraulic actuator (4.9 × 10
−4
mm
3
) by more than an order of magnitude is demonstrated. The use of stiff 2PP polymers with micron‐scale dimensions enable compliant membranes similar to exoskeletons seen in nature without the requirement for low‐modulus materials. The bio‐inspired system is designed to mimic similar hydraulic pressure‐activated mechanisms in arachnid joints utilized for large displacement motions relative to body length. Using variations on this actuator design, the ability to transmit forces with relatively large magnitudes (milliNewtons) in 3D space is demonstrated, as well as the ability to direct motion that is useful towards microrobotics and medical applications. Microscale hydraulic actuation provides a promising approach toward the transmission of large forces and 3D motions at small scales, previously unattainable in wafer‐level 2D microelecromechanical systems (MEMS).
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