Search Results (78)

The internal curve hydraulic motor valve plate has a clearance self-compensation performance that can effectively improve the working efficiency of the valve plate. However, the dynamic characteristics of the valve plates require further investigation. This study considers the self-compensating ‘floating’ valve plate as the research object, proposes a dynamic characteristic analysis method for the internal curve hydraulic motor valve plate, and explores the changing rule of oil film thickness and surplus pressing force of the valve plate. The results showed that an increase in the inlet pressure and oil temperature led to an increase in the thickness of the oil film, and the amplitude of the oil film thickness was larger, whereas the rotational speed of the oil film thickness of the valve plate pair was not obvious. When the inlet pressure is lower than 8 MPa, and the oil temperature is in the range of 20–30 °C, the oil film is mainly subjected to the squeezing effect of the valve plate, and the displacement of the valve plate decreased with increasing rotational speed. The inlet pressure is the main factor affecting the displacement of the ‘floating’ valve plate, and when the inlet pressure reaches 8.7 MPa, the valve plate is in hydrostatic balance support. In addition, the surplus pressing force coefficient of the valve plate decreased with increasing inlet pressures. This study provides theoretical support for the design of variable pressing force valve plates for internal curve hydraulic motors by investigating the dynamic characteristics of “floating” valve plates. Full article

The aim of this study was to evaluate machine learning algorithms’ capacity to improve prescriptive maintenance. A pumping system consisting of two hydraulic pumps with an electric motor from a Spanish petrochemical company was used as a case study. Sensors were used to record data on the variables, with the target variable being the bearing temperature of the electric motor. Several regression models and a neural network time series model were tested to model the system variables. A bearing temperature sensitivity analysis was conducted based on the coefficients obtained from the optimization of the regression model. To fully exploit the capabilities of these techniques for application in this field, we designed a reference framework intended to foster model deployment in an industrial context by promoting the self-monitoring and updating of the models when required. The impact on decision-making processes is explored using reinforcement learning in the context of this framework. Full article

This paper presents a comparison of some different configurations of electro-hydrostatic actuators (EHA). The gear pump EHA has a simpler mechanical configuration, but the electronic power command circuits and the electric motor are in high demand due to the very frequent speed variations. The variable piston pump EHA has a more complicated mechanical configuration, but the electronic power command circuits and the main electric motor are less loaded due to the constant speed of the electric motor. The variable displacement pump control can be made either using an electric motor and mechanical transmission, or an additional hydraulic circuit, to modify the swash plate angle. In total, four EHA configurations are studied in this paper (one with a gear pump and three with variable axial piston pumps). The paper aims to advantages and disadvantages of each type of EHA, using numerical simulations. Full article

Hydrostatic transmissions are essential in applications demanding variable torque and speed, such as mining and agricultural machinery, due to their compact design, high power-to-weight ratio, and efficient variable speed control. Despite these advantages, their inherent nonlinearities and susceptibility to parametric uncertainties pose significant challenges for precise motion control. This study presents a comparative analysis of classical PID and robust H-infinity controllers for regulating the speed of hydraulic motors under varying torsional loads. A linearized uncertain system model is developed using upper Linear Fractional Transformations (LFTs) to capture key parametric uncertainties. A simplified H-infinity controller is designed to robustly manage system dynamics, particularly addressing phase lags induced by uncertain loads. Simulation results demonstrate that the H-infinity controller offers superior performance over the PID controller in terms of stability, disturbance rejection, and robustness to load fluctuations. This work contributes a practically viable robust control solution for improving the reliability and precision of electro-hydraulic systems, particularly in demanding, real-world environments. Full article

A model-based control scheme for state transitions of a variable recruitment fluidic artificial muscle (FAM) bundle is developed and experimentally validated. FAMs can be bundled together in parallel to exhibit variable recruitment functionality, which is an activation strategy inspired by how motor units (MUs) in skeletal muscle are recruited. By adapting variable recruitment, an FAM bundle is able to operate efficiently over its entire force-contraction space while increasing control authority and bandwidth at low recruitment states. A variable recruitment bundle poses a hybrid control problem as it operates by controlling pressure as a continuous variable while simultaneously shifting between discrete recruitment states. During such state transitions, the bundle may experience a lag in strain if the shift timing is not properly anticipated. In this study, a model that captures the interaction effects between FAMs and a hydraulic system model is used to inform the controller of when a state transition should be made. The proposed control scheme is compared to a baseline control scheme that uses a percentage of the source pressure as the threshold for when a shift is made. The controller performance is evaluated by tracking a sinusoidal strain trajectory, and the average and maximum strain errors are compared between the baseline and proposed controller. The applied FAM pressures are presented to show that the model-based compensation is able to determine when a transition needs to be made. As a result, the tracking performance of the proposed control scheme is shown to significantly decrease the integrated absolute and maximum errors. Full article

Over the past few years, reducing energy consumption in hydraulic excavators has gained increasing attention, driving significant research in this field. One effective strategy involves integrating hydrostatic transmission (HST) and hydraulic pump/motor (HPM) systems into hydraulic excavators. However, challenges like disturbances, throttling-induced pressure drops, and fluid leakage often hinder both positional accuracy and energy efficiency. To tackle these issues, our study proposes a sophisticated dynamic forecasting model for positional control, integrating beluga whale optimization (BWO), long short-term memory (LSTM), and random forest (RF) techniques. The approach begins with dynamic data evaluation using Pearson’s correlation analysis to identify tuning parameters that have moderate to strong correlations with control variables, which are then used as inputs for predictive modeling. Initially, a standalone LSTM framework is developed to estimate the system’s positional output, with BWO optimizing four key tuning parameters. Subsequently, a hybrid BWO-enhanced LSTM-RF system is deployed to capture complex nonlinear patterns, improving the accuracy of motion trajectory predictions. Simulations and experiments confirm that our approach achieves a positional error below 3 mm, ensuring precise tracking and providing reliable data for operators. Compared to conventional proportional–integral–derivative (PID) controllers, standalone LSTM-RF, and a hybrid controller combining particle swarm optimization (PSO), LSTM, a gated recurrent unit (GRU), and PID (PSO-LSTM-GRU-PID), our method achieves superior tracking precision and energy savings of 12.46%, 8.98%, and 3.97%, respectively. Full article

An enhanced chaotic particle swarm optimization fuzzy PID is introduced to address the hydraulic wind turbine grid-connected speed control conditions. In the enhanced algorithm, a Circle chaotic mapping is combined with particle swarm optimization (PSO) to prevent PSO from becoming trapped in local optima. Moreover, a linear inertia weight reduction strategy is integrated to harmonize the algorithm’s capacity for expansive exploration and meticulous exploitation. Then, the enhanced algorithm is utilized to adjust and perfect the configuration variables within the fuzzy PID system. Based on the optimization, speed characteristics of the variable motor are analyzed. Simulation results show that when the swash plate angle factor varies within a specific range, the variable motor speed is only related to the quantitative pump speed. When the input speed of the quantitative pump changes in a step from 400 to 500 r/min, the enhanced CPSO fuzzy PID control approach reduces ascension time by 40% and 76%, and settling time by 80% and 76%, compared to the fuzzy PID and PSO fuzzy PID control approaches, respectively. When the input speed changes in a step from 500 to 600 r/min, the approach reduces ascension time by 25% and 72%, and settling time by 80% and 72%, respectively. When the input speed varies within a range of 400–500 r/min, the approach reduces ascension time by 37.5% and 80%, and settling time by 83% and 80%, respectively. And the enhanced CPSO fuzzy PID speed-control system exhibits no overshoot. Therefore, the enhanced CPSO fuzzy PID algorithm enhances the quantitative pump-motor system’s stability and rapidity, meeting hydraulic wind turbine grid-connected speed-control needs. Full article

Crawler cranes are mobile lifting equipment used in the process of hoisting goods. After the initial lifting, the crane may need a secondary lift due to adjustments in the position or height of the load. Addressing the common issue of load slipping during the secondary lift caused by hydraulic motor reversal, this study proposes a control strategy applicable to crawler crane secondary lifting. Initially establishing the dynamic characteristics of the secondary lift system, incorporating a delay coefficient, and matching motor pressure build-up with memory pressure, the strategy considers a variable pump input current control to identify the relationship between motor pressure build-up and brake release. Analyzing the dynamic characteristics of secondary lifting under different conditions, this study resolves the issue of hydraulic motor reversal during the second lift caused by heavy loads. The results of this study on crawler crane secondary lifting indicate that, when using a delay coefficient of 0.70 and releasing the brake, no slip phenomenon occurred during the secondary lift process under different load conditions, categorized as 200 tons, 600 tons, and 1000 tons. This ensures the stability and transition quality of the secondary lift, providing theoretical guidance for the control of the crawler crane secondary lifting. Full article

This paper investigates an adaptive disturbance rejection control (ADRC) strategy for dual-variable power smoothing for hydraulic wind turbine systems deployed in marine environments. Initially, fluctuations in wind speed induce variations in the output torque and rotational speed of the wind turbine; this study examines the interaction between these two variables and subsequently decouples them. An innovative dual-variable anti-disturbance control strategy is proposed, which independently regulates the pitch angle of the rotor and the swing angle of the variable motor to mitigate fluctuations in both speed and torque, thereby achieving a smoother system output power. The simulation results obtained through MATLAB/Simulink (Version R2022a) indicate that employing the proposed control strategy leads to an 8.31% reduction in power generation compared to optimal power tracking strategies while enhancing output power stability by 56.67%. Furthermore, the effective smoothing of power fluctuations is accomplished without necessitating energy storage devices. Finally, the effectiveness of the power smooth output control strategy proposed in this paper was verified based on a semi-physical simulation experimental platform for a 30 kW hydraulic wind turbine. The control method proposed in this paper provides a theoretical basis for the promotion and application of hydraulic wind turbines with stable power output. Full article

The swivel system of a hydraulic excavator is susceptible to pressure impact during start and stop, which significantly impacts the service life of the excavator. In this investigation into how varying speeds affect the dynamic characteristics of a swing motor’s buffer relief valve (BRV), the AMESim simulation model of the whole swing motor was established, and its validity was confirmed through experimental testing. The pressure overshoot rate and start–stop impact time of the BRV of a swing motor at 1000 rpm, 1500 rpm, and 2000 rpm, under different spring stiffnesses, were analyzed. Based on the mathematical model of the BRV, the influence of the main structural parameters of the BRV on its dynamic characteristics were analyzed using an AMESim simulation model of the whole swing motor. The results show that an increase in the rotational speed of the electric motor, while maintaining a constant spring stiffness, affects the pressure overshoot rates of both the buffer relief valve of the swing motor inlet (BRVSMI) and the buffer relief valve of the swing motor outlet (BRVSMO); specifically, when the set pressure is established at 20 MPa, the pressure overshoot rate is observed to be higher, and the start–stop impact time exceeds 25 MPa. During the start phase of the swing motor, the start impact time for the BRVSMI remains relatively constant at approximately 2.5 s, with the pressure overshoot rate stabilizing at around 0.8. Conversely, in the stop phase of swing motor, both the stop impact time and the pressure overshoot rate of the BRVSMO exhibit variability in their response to the structural parameters of the BRV. Under conditions of comparatively high pressure, it is recommended to increase the diameter of the spool damping hole, the mass of the valve core, and the viscous damping coefficient, while simultaneously reducing the guide rod diameter of the buffer plunger, as these modifications can effectively enhance the start–stop impact time and mitigate the pressure overshoot rate. Full article

The conventional hydraulic system of excavators suffers from significant valve throttling losses and inadequate matching between the hydraulic power source and the load, which substantially impact the system’s overall energy consumption and severely impede the trend toward electrification and energy efficiency in construction machinery. To address this issue, a pump-controlled hydraulic cylinder system has been implemented to replace the original valve-controlled hydraulic system that utilizes a single pump with multiple actuators. The influence of energy conversion efficiency and the speed between the motor and the hydraulic pump under varying load-power conditions has been determined through experimental investigations. Based on these findings, a compound-control strategy is proposed that adjusts the displacement of the hydraulic pump to achieve precise control over the position of the hydraulic cylinder and facilitates both the speed and displacement coordination while ensuring optimal motor speed matching with the load power. This strategy is implemented in the boom pump’s hydraulic cylinder control system. The research findings indicate that this combined-control approach enhances efficiency by approximately 18.9% compared with traditional variable-speed pump-controlled hydraulic cylinder systems. Furthermore, energy consumption is reduced by about 39% compared with the conventional valve-controlled hydraulic system. Full article

In order to solve the problems of frequent pressure fluctuations caused by frequent action of the unloading valve of the pump station and serious hydraulic shock due to the variable amount of fluid used in the hydraulic support system of the coal mining face and the irregularity of the load suffered by the system, a pump–valve cooperative multi-mode stabilizing control method based on a digital unloading valve was proposed. Firstly, a prototype of a digital unloading valve under high-pressure and high water-based conditions was developed, and a digital control scheme was proposed to control the pilot valve by a servo motor to adjust the system pressure in real time. Then, an experimental platform for simulating the hydraulic bracket and a co-simulation model was constructed, and the validity of the co-simulation model was verified through experiments. Secondly, a collaborative multi-mode pressure stabilization control method for the pump valve based on a GRNN (General Regression Neural Network) was established to control the flow and pressure output of the emulsion pumping station according to the actual working conditions. Finally, numerical research and experimental verification were carried out for different working conditions to prove the effectiveness of this method. The results showed that the proposed pressure stabilization control method could adaptively adjust the working state of the digital unloading valve and the liquid supply flow of the emulsion pump station according to the working condition of the hydraulic support, effectively reducing the frequency and amplitude of the system pressure fluctuations and making the system pressure more stable. Full article

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. Full article

The rapid development of industrial and information technology is driving the demand to improve the applicability and hydraulic performance of centrifugal pumps in various applications. Enhancing the rotational speed of pumps can simultaneously increase the head and reduce the impeller diameter, thereby reducing the pump size and weight and also improving pump efficiency. This paper reviews the current application status of high-speed pumps using low-temperature thermosensitive fluids, which have been applied in fields such as novel energy-saving cooling technologies, aerospace, chemical industries, and cryogenic engineering. Due to operational constraints and thermal effects, there are inherent challenges that still need to be addressed for high-speed pumps. Based on numerical simulation and experimental research for different working fluids, the results regarding cavitation within the inducer have been categorized and summarized. Improvements to cavitation models, the mechanism of unsteady cavity shedding, vortex generation and cavitation suppression, and the impact of cavitation on pump performance were examined. Subsequently, the thermal properties and cavitation thermal effects of low-temperature thermosensitive fluids were analyzed. In response to the application requirements of pump-driven two-phase cooling systems in data centers, a high-speed refrigerant pump employing hydrodynamic bearings has been proposed. Experimental results indicate that the prototype achieves a head of 56.5 m and an efficiency of 36.1% at design conditions (n = 7000 rpm, Q = 1.5 m³/h). The prototype features a variable frequency motor, allowing for a wider operational range, and has successfully passed both on/off and continuous operation tests. These findings provide valuable insights for improving the performance of high-speed refrigerant pumps in relevant applications. Full article

The aim of this research is to devise a continuous simulation model for predicting ship crane failures to increase their reliability and reduce unplanned downtime during cargo loading and unloading operations. To predict the condition of the hydraulic system, a database from the GALIOT software package was used for carrying out maintenance on cranes at m/v “O” over a period of 120,000 working hours. In the research, fault tree analysis (FTA) was used to identify causal relationships between system failures and basic events, while the Markov mathematical model was used to model the system state and predict transitions between different failure states. A system dynamics simulation model was developed to simulate the behavior of a system using POWERSIM PowerSim Constructor 2.5.d (4002), and regression analysis was performed to analyze the simulation results and understand the relationships between dependent and independent variables. The results show that a model for predicting failures in the hydraulic motors and pumps of ship cranes was developed, and the Markov model makes it possible to estimate the frequency of transitions between states under the condition that the sum of reliability equals one. The simulation model shows high reliability of the cranes and a constant frequency of failures throughout the 120,000 operating hours, while the regression analysis confirms the validity of the simulation model and shows a strong correlation between the analyzed variables. These models are used to improve the planning of ship crane maintenance, reduce unplanned downtime, and predict and promptly detect failures, which overall minimizes maintenance costs and failures. Full article