Hydraulic Power System Research Articles

Calculations of Performance Characteristics of Submerged Cargo Pumps with Hydraulic Drive and Constant Torque Controllers, Taking into Account the Energy Efficiency of the Drive Motor

Submerged cargo pumps installed on board tankers are one of the most important components of their cargo system. As they are installed directly in the cargo tanks, they are usually equipped with a hydraulic drive whose power and capacity are controlled by constant-torque controllers. These have a significant impact on the technical and performance characteristics of the cargo pumps. This paper presents a methodology for calculating the performance characteristics of submerged cargo pumps, taking into account the energy efficiency of their hydraulic drive motors. Due to their number and power, the cargo pumps are powered from the ship’s hydraulic central loading system. This paper describes the main parts of the hydraulic power system structure and the functions of the constant torque controller of the STC type. A mathematical model has been developed to use the basic characteristics of submerged cargo pumps made for the base cargo (water) sent by the pump manufacturer for the case of handling liquid cargo with different parameters. The model considers the characteristics of the hydraulic drive, including a Bosch Rexroth A2FM type hydraulic drive motor and a constant torque controller. The results of simulation calculations of the performance characteristics of an example cargo pump are presented and compared with measurements of the characteristics of this pump on a product tanker. The mathematical model presented in this paper is of utilitarian value, enabling calculations to be carried out without the need for time-consuming CFD numerical methods, making it useful for port and fuel terminal logistics services, ship crews and services managing the operation of product tanker fleets.

Active Disturbance Rejection Control of Engine Speed in Series Hydraulic Hybrid Power System

Abstract: In this paper, a novel series hydraulic hybrid powertrain is proposed for a three-axis all-terrain vehicle. The engine drives two variable displacement pumps responsible for driving and steering, respectively. A variable displacement motor is connected to the ring gear of the planetary coupling mechanism to drive the vehicle and a fixed-displacement motor is connected to the sun gear to steer the vehicle. The active disturbance rejection control with feedforward control is employed to control the engine speed. The engine speed is controlled in a close-looped manner by adjusting the engine throttle. The controller parameters are decided by analyzing the influence of each parameter on the controller performance by means of the control variable method. The simulation results indicate that the proposed control strategy enables the vehicle to obtain better engine speed following and anti-disturbance performance. An all-terrain prototype is established and field tests are carried out to verify the effectiveness of the design and control strategy of the series hydraulic hybrid powertrain for the all-terrain vehicle.

Shipboard crane digital twin: An empirical study on R/V Gunnerus

The maritime industry is constantly facing new challenges and technological advancements, making the adaptation of innovative solutions like digital twins a bridge enhancing safety and efficiency between theoretical models and real-world maritime applications. Digital twin simulators for complex dynamic operation systems such as shipboard cranes, allow the operators to practice demanding operations in a risk-free immersive environment with various scenarios. This paper presents the process of developing a digital twin-based simulation tool designed for shipboard crane operations. It is based on co-simulation using the Functional Mock-up Interface (FMI) standard. This allows for the integration of the operation scenarios with different physical domain models, including such as the ship, environmental forces, hydraulic power systems, and controllers. In addition, the digital twin has opened up new opportunities for the optimization of maritime systems. It can be used to identify the optimal operating conditions, predict potential risks, and provide onboard support to the operator. A demo crane digital twin is implemented for the Palfinger crane on the Gunnerus research vessel with system validation via a series of marine operations being real-time monitored by the Remote Control Center (RCC).

Sensor Technologies for Hydraulic Valve and System Performance Monitoring: Challenges and Perspectives

AbstractHydraulic fluid power systems are essential for a range of engineering applications such as transportation, heavy industry, and robotics. The scale of the industry is such that hydraulic pumps are estimated to account for 15% of all the energy consumption in the European Union and yet the average efficiency of fluid power systems is only 22%. The digitalization of hydraulic systems offers significant advantages in terms of energy efficiency, performance, reduced maintenance, and automation. However, this requires advances in the integration of smart sensing technologies to provide real‐time feedback on the operation and health of hydraulic components. This review details developing trends in hydraulic fluid power research and provides an overview of progress related to the digitalization of these systems and their integration within an Industry 4.0 framework. The fundamentals of relevant sensor technologies and innovative approaches for integrating sensors into hydraulics systems are discussed. Methods to deliver power to the sensors and associated electronics through harvested pressure ripples are also reviewed. An outlook with respect to future directions in this field is given, including an assessment of the potential for exploiting advanced manufacturing technologies, in particular additive manufacturing, to facilitate successful sensor integration into hydraulic fluid power systems.

Development of a mathematical model for analyzing the perturbed state of a thermal power hydraulic system

Development of a mathematical model for analyzing the perturbed state of a thermal power hydraulic system

Analysis of the thermal power hydraulic system in undisturbed state

Analysis of the thermal power hydraulic system in undisturbed state

Математическое моделирование потокораспределения возмущенного состояния теплоэнергетической системы

The results of the development of a model for the analysis of the disturbed state of a thermal power hydraulic system on the example of a heat supply system are presented. The parameters of the operating mode of the thermal power hydraulic system after the influence of disturbing factors on it were evaluated. It is shown that the classification of stationary states of the studied fragment of the system with steady flow distribution is oriented to boundary conditions. The boundary conditions classified into four types are considered. It is noted that the choice of boundary conditions must be carried out taking into account the use of energy equivalence in the analysis of the perturbed state of the studied fragment of the hydraulic system. The developed model of steady-state flow distribution with a non-isothermal flow of a viscous medium is presented. It is concluded that the developed mathematical model represents a qualitatively new approach to formalizing the problems of flow distribution analysis in systems with adjustable parameters. The model can be considered as a generalized form of representation of particular flow distribution models when describing the object under study, which can be considered as a hydraulic circuit with adjustable parameters with a non-isothermal flow of a viscous medium. It is shown that this model can be used to analyze and describe the flows and properties of a viscous medium in such systems where it is possible to regulate the parameters, and non-isothermal flow is taken into account.

Research on the complete vehicle control strategy of the composite accumulator hydraulic hybrid power system

The compound accumulator is an energy storage device consisting of a large accumulator and a small accumulator. Compared with the traditional single accumulator hydraulic hybrid vehicle, it has the characteristics and advantages of fast braking response for the small accumulator and more energy recovery for the large accumulator, combining braking characteristics and energy recovery rate. This paper proposes the control strategy for parallel hydraulic hybrid vehicle based on compound accumulator, which can determine the working timing for large and small accumulators according to the specific driving conditions, thereby improving the braking performance and fuel economy for the vehicle. Under NEDC conditions, this paper uses dynamic programming algorithm to find the optimal control sequence for torque distribution and energy management of the hydraulic hybrid vehicle with composite accumulator, obtains the control rules and logic thresholds of the logic threshold control strategy, and obtains the switching rule of the working timing of the composite accumulator. The simulation of specific cycle conditions is carried out to verify the rationality of vehicle control strategy and to explore the energy-saving mechanism of parallel hydraulic hybrid power system based on composite accumulator. The NEDC urban cycle test was carried out, and the comparison between the test and simulation results showed that the hydraulic hybrid operation mode, large and small accumulator pressure, and engine fuel consumption during the test were basically consistent with the simulation results and verified the control effect of the vehicle control strategy and the energy-saving mechanism of the parallel hydraulic hybrid system based on the composite accumulator.

Разработка математической модели анализа невозмущенного состояния теплоэнергетической гидравлической системы

The sequence of development of a model for analyzing the undisturbed state of a thermal power hydraulic system - a heat supply system, which is an important stage in the design and optimization of the system, is considered. The main parameters of the system are analyzed, such as thermal loads, heat flows, heat transfer through pipes and heat exchangers, location and characteristics of equipment (boilers, pumps, etc.). A mathematical model of the system has been developed, which should take into account all the main factors affecting heat transfer and the efficiency of the system. The model is presented in the form of a system of equations and includes parameters such as temperature, pressure, coolant flow, etc. Based on this model, it is possible to analyze various operating modes of the system, optimize parameters and make decisions to improve it. When developing the model, the possibility of various disturbances was taken into account. To analyze the unperturbed state of the system, the influence of such disturbances is excluded and its basic operation is considered. When developing a flow distribution analysis model for a heat and power system, energy equivalence was used. The developed model for analyzing the undisturbed state of a thermal power system will make it possible to more accurately design and control such a hydraulic system, improve its efficiency and reliability.

Inverse transient analysis based calibration of surrogate pipeline model for fault simulation of axial piston pumps

Axial piston pumps are the key component in power hydraulic systems. Flow and pressure ripple signals, which can reflect the flow dynamics of the axial piston pump, are important information sources for condition monitoring. Therefore, the characteristics of flow and pressure ripple signals should be investigated for further condition monitoring and fault analysis. However, measuring high-frequency flow ripple directly can be difficult, and the pressure ripple is not only affected by pump dynamics but also affected by the transient pressure wave propagation. However, in practical applications, the hydraulic pipeline system is complex due to the space constraint of the equipment, and the influence of the pipeline system cannot be ignored when modeling pressure ripple. This paper proposes a novel two-stage method for fault simulation of the pumps that considers the influence of the pipeline system on the pressure ripple. Firstly, the surrogate pipeline model with free parameters is calibrated using ITA to capture the characteristics of the complex practical pipeline system. Secondly, the calibrated model is applied to the fault simulation of axial piston pumps. A detailed 3D CFD model of the pump is built up, and the flow ripple at the pump outlet from the numerical model is used as an approximation of the real flow ripple of the pump, which serves as one of the boundary conditions of the surrogate pipeline model. After calibrating the model, the CFD model of the pump is used to simulate internal failures in the pump. Two failure cases are studied: a faulty slipper and a faulty cylinder. The simulated signal of the proposed model matches the experimental signal well under the healthy and faulty conditions, which confirms the effectiveness of the proposed method.

Hydraulic Power System Control using State Feedback Controller (SFC)

In an electrical network, generators work and provide power to the loads. When the load on the generator increases, the speed of the generator decreases then resulting in a reduction in the frequency of the network. This paper was designed within the state feedback controller (SFC) to improve the hydraulic power system performance. The performance of the proposed controller is compared with simple feedback controller (FC) in the simulation environment. The load variation was tested which is 5%, 10%, and 20% variation. The testing results show that in terms of steady state error (SSE) and overshoot, the SFC is superior. In terms of settling time, the FC method is faster. Since it quickly reaches steady event not getting into set-point. The overall, it can be concluded that SFC can give better performance than FC in the frequency control of a hydraulic power system.

Achieving a high efficiency on stationary gas turbine

Energy is an essential resource every population relies on. In recent years, the importance of thermal energy has stood out due to the performance decrement of both hydraulic and wind power systems, resulting from severe climate changes. Considering thermal power plants like gas turbine systems, thermal efficiency is always the element that engineers aim to improve on. The efficiency of a stationary gas turbine determines how much useful energy can be produced in a given amount of resources, and that is vital to any power plant economically and environmentally. In this paper, through research from various dissertations, journals, and websites, technologies developed for efficiency improvement for gas turbines are summarized and discussed with specific examples and comparisons, focusing on complex cycles, combined cycles, and maintenance procedures. In the end, the paper concluded that there are many factors affecting the thermal efficiency of a stationary gas turbine. Every gas turbine station varies due to its specific applications, locations, the material available, and project budget, and far more new topics are waiting to be explored.

Classification of Wear State for a Positive Displacement Pump Using Deep Machine Learning

Hydraulic power systems are commonly used in heavy industry (usually highly energy-intensive) and are often associated with high power losses. Designing a suitable system to allow an early assessment of the wear conditions of components in a hydraulic system (e.g., an axial piston pump) can effectively contribute to reducing energy losses during use. This paper presents the application of a deep machine learning system to determine the efficiency state of a multi-piston positive displacement pump. Such pumps are significant in high-power hydraulic systems. The correct operation of the entire hydraulic system often depends on its proper functioning. The wear and tear of individual pump components usually leads to a decrease in the pump’s operating pressure and volumetric losses, subsequently resulting in a decrease in overall pump efficiency and increases in vibration and pump noise. This in turn leads to an increase in energy losses throughout the hydraulic system, which releases excess heat. Typical failures of the discussed pumps and their causes are described after reviewing current research work using deep machine learning. Next, the test bench on which the diagnostic experiment was conducted and the selected operating signals that were recorded are described. The measured signals were subjected to a time–frequency analysis, and their features, calculated in terms of the time and frequency domains, underwent a significance ranking using the minimum redundancy maximum relevance (MRMR) algorithm. The next step was to design a neural network structure to classify the wear state of the pump and to test and evaluate the effectiveness of the network’s recognition of the pump’s condition. The whole study was summarized with conclusions.

Stability Study of Time Lag Disturbance in an Automatic Tractor Steering System Based on Sliding Mode Predictive Control

To improve the working accuracy and anti-interference capability of the steering operation of an automatic tractor, this paper investigates the tractor steering system. In response to the current problems of high steering resistance during tractor field operations and the low service life of the drive shaft of conventional electric steering wheel solutions, an electro-hydraulic coupled power-assisted solution combining EPS and HPS is proposed. The combination of the EPS system’s high control accuracy and sensitive steering operation and the hydraulic power system’s large steering torque greatly reduces the power of the power motor and battery performance requirements, optimizing the power transmission scheme to achieve green and energy-saving purposes. Secondly, the research is focused on the influence of external disturbances on the stability of the steering system during tractor operation, and a combination of model predictive control and sliding mode control is used to study the steering system control strategy. It is finally demonstrated through simulations and experiments that it can compensate for the disturbance of the system control parameters by external disturbances, has the ability of MPC to handle input constraints and maintains the advantages of SMC robustness.

Lightweight Electrohydrostatic Actuator Drive Solution for Exoskeleton Robots

The practical long-term application of power-assisted exoskeleton robots requires lightweight, high-efficient, and high-control precision actuators. Based on the improvement of hardware design and control method, this article proposes a complete drive solution for the joint drive of exoskeleton robots and promotes the research of robot joint drive based on the pump-controlled hydraulic system. Specifically, a compact, backdrivable, and energy-efficient drive unit, lightweight electrohydrostatic actuator (LEHA) with a weight of 2.5 kg and a rated power of 340 W is designed first. Then, by combining the fifth-order high-precision dynamics model of LEHA and virtual decomposition control method, a high-performance controller with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_{2}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_{\infty }$</tex-math></inline-formula> stability is developed to realize the precise position trajectory tracking control of LEHA. Experimental results based on actual exoskeleton robot knee joints show that the proposed solution has high trajectory tracking performance over the frequency range of human body swing phase motion (0.5–1.5 Hz) and different loads (0–20 kg). Moreover, compared with the valve-controlled hydraulic power system with the same exoskeleton robot knee joint and wearer, test results show that the average efficiency increased by 18.13% after using LEHA under the swing phase test.

Research on Hydraulic Power System Operation Status Diagnosis Technology Based on Hybrid CNN Model

Aiming at the problems that the features extracted from the traditional system operation state are not adaptive and the specific system operation state is difficult to match, a gearbox system operation state diagnosis method based on continuous wavelet transform (CWT) and two-dimensional convolutional neural network (CNN) is proposed. The method uses the continuous wavelet transform to construct the time-frequency map of the hydrodynamic system operating state signal, and uses it as the input to construct a convolutional neural network model, and forms a deep distributed system operating state feature expression through a multilayer convolutional pool. The structural parameters of each layer of the network are adjusted by the back propagation algorithm to establish an accurate mapping from the signal characteristics to the system operating state. In the experiments under different working conditions and different system operation states, the accuracy of system operation state recognition reaches 99.2%, which verifies the effectiveness of the method. Using this method of adaptively learning rich information in the signal can provide a basis for intelligent system operation state diagnosis.

Rectification of a Slanted Box-Girder Bridge Caused by Unbalanced Soil Load

Aims: Rectification of a slanted continuous concrete box-girder bridge is presented in this paper. Background: Several bridge piers slanted due to uneven ground settlement, inducing excessive width of some expansion joints and oversize sliding displacement of some bridge bearings. The uneven ground settlement occured due to the unbalanced soil load on the ground. Methods: In this project, reverse ground loading was first applied to produce opposite-direction deformation of the bending bridge piles, thereby rectifying the slanted bridge piers rigidly connected to the piles. The procedure was accelerated by constructing several stress release holes on the opposite side of the reverse ground loading. Results: To stabilize foundation and prevent landsides of riverbank, combimationn of jet grouting piles and deep mixed piles was apliied to reinforce foundation soil, providing lateral restraint on the bridge piles as well. Finally, a hydraulic power system was used to reset the bridge piers, girders, and expansion joints. A similar system and additional equipment were used to replace the damaged bridge bearings. Conclusion: The recommended rectification techniques are suitable for rectifying bridges with similar geotechnical conditions and structure types and for replacing damaged bridge bearings.

Research on Safety Interlock System Design and Control Experiment of Combined Support and Anchor Equipment.

In view of the risk of collision with humans or equipment arising from a lack of protection in the operation process of combined support and anchor equipment on the heading face, this paper designs a safety interlock system for combined support and anchor equipment. Firstly, a mathematical model of hydraulic power system control and a valve control system based on feedforward–feedback optimization were established according to the power demand of the combined support and anchor equipment. Secondly, according to the reliability indexes of the safety interlock system, corresponding sensor, logic control and execution modules were designed. Ultrasonic sensor groups were arranged at the key positions of the combined support and anchor equipment to capture the position information in real time when the equipment was moving. Thus, the pump-valve hydraulic system was controlled through closed-loop feedback. The experimental results show that the safety interlock system of the combined support and anchor equipment can adjust the revolving speed of the permanent magnet synchronous motor (PMSM) in real time according to the distance from the obstacle, so as to control the pump outlet flow, and then perform interlocking safety control of the hydraulic cylinder’s movement speed. The system can effectively prevent damage to the surrounding equipment or personnel arising from equipment malfunction.

Experimental investigation on cavitation and cavitation detection of axial piston pump based on MLP-Mixer

Hydraulic pump constitutes the key component in hydraulic power system and its fault diagnosis is of great importance. Among all types of pumps, the axial piston pump is widely used, but due to its high speed and high pressure working condition, its cavitation characteristics are not so good as those of other hydraulic pumps. Therefore, in this article, a new cavitation detection framework that contains both experimental investigations and numerical signal processing is proposed to detect cavitation intensity of the axial piston pump. Cavitation intensity of the axial piston pump has been divided into three stages: normal state, cavitation development state and cavitation severe state. The cavitation detection model based on MLP-Mixer is introduced to recognize cavitation intensity of the axial piston pump with given working conditions. The testing accuracy of optimized cavitation detection model is quite high with above 99% for all given working conditions.

Mathematical model and PID control of a hydraulic motor using on/off solenoid valve

Hydraulic motors have a high power capacity that makes them commonly used in different applications. These applications require precise control of hydraulic motors’ position, velocity, and force. Digital hydraulic valves are commonly used in hydraulic power systems. The high-speed on/off valves (HSVs) are digital valves usually used in flow or pressure control where high dynamic performance is required to improve the control accuracy. This paper aims to present an accurate method of controlling a hydraulic motor using HSV and PID control. A mathematical model of the whole system is presented. This model allows predicting the system response and refining the control gains to reach the desired response. The model parameters are obtained by experimental measurement, or typical values are used. The model is implemented using MATLAB and SIMULINK. Then it is validated experimentally using some tests. The designed control method is implemented on the motor using NI myRIO as a controller, which is coded by LabVIEW software