Hydraulic Control Research Articles

Optimization of Hydraulic Fine Blanking Press Control System Based on System Identification

Fine-blanking is a molding process based on the common blanking process, which obtains hydrostatic stress through blank holder reverse jacking, in order to increase material plasticity. It requires special equipment, namely a fine-blanking press, to complete the fine-blanking process. In this paper, the problem of the speed of the slide block fluctuation found in the actual use of a 12,000 kN hydraulic fine-blanking press after multi-stage pressure source optimization is studied. Firstly, the mathematical model of the motion of the slide block in the blanking stage of the hydraulic fine blanking press is established, and the accurate mathematical model in the blanking stage of the hydraulic fine-blanking press is obtained through the least square method system identification experiment. Aiming at the complex working situation of the fine-blanking press, a phased PID control strategy is creatively proposed. The optimal PID control parameters are obtained by a genetic algorithm, and established a fuzzy PID controller for the blanking stage to accurately control the movement speed of the slide block. The results show that the new control strategy is very effective in improving the movement accuracy of the slide block, effectively improving the machining accuracy and reducing the impact vibration of the hydraulic system.

A Gain Scheduling Design Method of the Aero-Engine Fuel Servo Constant Pressure Valve with High Accuracy and Fast Response Ability

Constant pressure valve, which has an axially symmetric structure, is an essential component to supply the servo reference pressure for aero-engine hydraulic mechanical control systems, and its performance directly impacts the performance of the control system. This paper constructs a closed-loop disturbance rejection system of the constant pressure valve based on the linear incremental description method, in which the controlled object is the controlled pressure, and the stabilization controller is constructed by the closed-loop feedback motion valve. Meanwhile, the linear models of the closed-loop system are calculated. Subsequently, based on the bode frequency domain characteristic analysis, the accurate influences of the stabilization control gain on the dynamic performance and stability of the system are given. On this basis, a gain scheduling design method of the system is proposed, and the geometry design and implementation method of the inlet orifice is proposed to complete the design work. The simulation results show that under bad conditions, which include the 1 MPa strong step disturbance of the inlet pressure and the step disturbance of the variable outlet flow area, the steady-state working range of the controlled pressure is 1.5 ± 0.01 MPa, the steady-state error is not more than 0.7%, and the regulation time is not more than 0.006 s.

Review on Solar Photovoltaic-Powered Pumping Systems

Water and energy are becoming more and more important in agriculture, urban areas and for the growing population worldwide, particularly in developing countries. To provide access to water it is necessary to use appropriate pumping systems and supply them with enough energy for operation. Pumps powered by solar photovoltaic energy are complex electromechanical systems that include hydraulic equipment, electrical machines, sensors, power converters, and control units. Therefore, solar photovoltaic pumping systems are associated with various fields of science and engineering. In remote, less-populated areas without electricity, where it is either challenging to connect to the grid or it is not possible, solar photovoltaic water pumping systems can play a significant role. To see whether solar photovoltaic pumping systems may be a practical, viable, and affordable method of pumping water it is necessary to study different aspects of their operation. The goal of this current article is to evaluate and outline recent research and advancement in the field of solar photovoltaic pumping systems. The major focus is on the standalone photovoltaic pumping system’s components, factors that affect system efficiency, performance evaluation, system optimization, and the potential for integration with modern control techniques. The main objective of this article is to give a broader overview of solar photovoltaic technologies for researchers, engineers, and decision-makers.

Learning-Based Nonlinear Model Predictive Controller for Hydraulic Cylinder Control of Ship Steering System

The steering mechanism of ship steering gear is generally driven by a hydraulic system. The precise control of the hydraulic cylinder in the steering mechanism can be achieved by the target rudder angle. However, hydraulic systems are often described as nonlinear systems with uncertainties. Since the system parameters are uncertain and system performances are influenced by disturbances and noises, the robustness cannot be satisfied by approximating the nonlinear theory by a linear theory. In this paper, a learning-based model predictive controller (LB-MPC) is designed for the position control of an electro-hydraulic cylinder system. In order to reduce the influence of uncertainty of the hydraulic system caused by the model mismatch, the Gaussian process (GP) is adopted, and also the real-time input and output data are used to improve the model. A comparative simulation of GP-MPC and MPC is performed assuming that the interference and uncertainty terms are bounded. Consequently, the proposed control strategy can effectively improve the piston position quickly and precisely with multiple constraint conditions.

Design and experiments of an automatic depth-adjusting double screw trencher and fertiliserning.

In response to the problems of low fertilizer application efficiency, poor operation quality, and uneven application of fertilizer by domestic tea garden trenching and fertilizing machines, an automatic depth-adjusting double screw trenching and fertilizing machine was designed. The machine uses a double spiral furrowing and fertilizer application method, which can complete the integrated operation of furrowing, fertilizer application, and mulching at one time. The key components of the machine such as the screw-type fertilizer discharger, trenching, and fertilizer application mechanism are designed using theoretical analysis, and the trenching depth is automatically adjusted through the hydraulic control system to maintain a consistent depth. A single-factor test and a quadratic regression rotary orthogonal test were conducted to select the diameter of the spiral fertilizer discharger, the rotational speed of the spiral fertilizer discharger, and the rotational speed of the trenching and fertilizer application mechanisms. Based on these tests, the fertilizer application performance of the fertilizer machine was evaluated, and a mathematical model of the fertilizer application volume and coefficient of variation was established. The influence of the test factors on the coefficient of variation was also analyzed. In the study, 58.36 and 480.35 r/min were found to be the optimal rotational speeds for spiral fertilizer discharge and trenching and fertilizer application, respectively, while 88.90 mm was found to be the optimal diameter for spiral fertilizer discharge. The coefficient of variation for the spiral fertilizer discharge was 3.95%, which meets the tea plantation's fertilizer application requirements.

Fuzzy adaptive trajectory tracking control of work-class ROVs considering thruster dynamics

Work-class remotely operated vehicles (ROVs) are widely used in oceanic observation and underwater operation, which are driven by hydraulic power. A fuzzy adaptive controller considering thruster dynamics is proposed to improve the trajectory tracking performance of work-class ROVs in this paper. The dynamics of the hydraulic motor driven thruster is much higher than the position and orientation tracking ability of work-class ROVs. Thus, the system is divided into two separate subsystems: out-loop position and orientation control system, and inner-loop hydraulic control system. A fuzzy adaptive algorithm is employed in the out-loop position and orientation controller, which estimates the system parameters and disturbances respectively. A disturbance observer is used in the inner-loop hydraulic controller to attenuate the uncertainties and disturbances. A second order filter is adopted to synthesize these two controllers, which generates a smooth hydraulic motor speed command with appropriate bandwidth and range. The stability of the whole control system is proved through Lyapunov theory. Simulation results demonstrate the effectiveness of the proposed trajectory tracking control strategy under parameter uncertainties and disturbances.

Simulation of energy recovery system of high speed transmission shaft dynamic torque test bench

A hydraulic energy recovery and control system is proposed to solve the energy loss problem of the current vehicle transmission shaft torque test bench. On the basis of the original system, power recovery is realized by parallel hydraulic compensation. PID module is used to control the displacement of piston variable pump and motor respectively to adjust the speed and torque to achieve the established working conditions. The feasibility of the hydraulic system and control scheme is verified by AMEsim-MATLAB software and experiments. The results show that the proposed system can not only adjust the set speed and torque dynamically, but also achieve high power recovery.

Design of hydraulic pneumatic control system for rail grinding car

This paper comprehensively uses the knowledge of mechatronics, mechanical structure, etc. The grinding wheel and cradle frame of the rail grinding car is studied and designed. The grinding wheel is controlled by a pneumatic servo, and the cradle frame is controlled by a hydraulic system. According to the accuracy requirements of the rail grinding car, the pneumatic servo schematic diagram of the grinding wheel to achieve precise grinding, the schematic diagram of the hydraulic control system in which the cradle frame can turn accurately, the AMESim software working interface model is established, the actual working parameters of the system components are set. After the hydraulic profiling system is designed, simulation, test, and analysis are carried out.

A review on the employment of the hydraulic cylinder for lifting purposes

The hydraulic elevator is both a cost-effective system and results in extremely clean building exterior lines since the usual penthouse-type machine room is eliminated. Without the need for wires, counterweights, or pulleys, this elevator can transfer people between levels. One of the most significant factors to consider when designing people's elevators is that they should not be disturbed when going between levels and that the elevators should stop accurately. As a consequence, innovative technologies such as the electro-hydraulic servo system (EHSS) may be employed with a traditional hydraulic elevator. This technology may employ speed and position input to provide the desired degrees of speed control, riding comfort, and leveling precision. The EHSS is a closed-loop control system that operates as a drive unit, raising and lowering the elevator cabin in response to a variable like position, velocity, or force. This paper examines various types of hydraulic systems for lifting purposes, as well as the application of servo system principles to hydraulic control valves, to credibly provide the traditional hydraulic elevator with a selectable diversity of precise and smooth transport characteristics across floors. This study also looks at how elevators employ telescopic hydraulic cylinders efficiently for lift purposes in the elevator.

Bypass Control strategy of a Pump as Turbine in a Water Distribution Network for energy recovery

Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water and pressure losses. These issues are solved by installing Pressure Reduction Valves (PRVs) to decrease the pressure in WDNs. Depending on the application, PRVs can waste large amount of energy, hence the substitution of PRVs with Pumps used as Turbines (PaTs) can be a good compromise in terms of economic and technical aspects to reduce leakages and recover energy. Currently the share of PaT is not yet fully developed due to the certain technical challenges yet to be addressed, as providing an affordable control strategy closer to the real working conditions in a WDN. Hence, more experimental activities are required. For these reasons, in this work an experimental campaign was carried with the aim to investigate the behavior of a PaT according to a possible layout that could be embedded into a WDN. Firstly, the machine was characterized both in pump and turbine modes. Moreover, the machine working conditions limits have been analysed in terms of runaway and blocked-rotor curves. Then, turbine tests were carried out at constant speed with a typical hydraulic control scheme by means of a PRV installed in series to the PaT and a second one installed on a bypass. As a result, this analysis highlighted the feasibility to recover a consistent amount of hydraulic energy otherwise wasted under typical WDN daily pressure and flow rate patterns, with promising results in terms of the operating point control of the machine.

Quasi-equilibrium channel metamorphosis in planform of a subtropical river in India in post-dam period

A basic fluvio-dynamics process in the sediment-energy fluxes is channel meandering and braiding. The construction of dams and barrages has primarily altered the meandering and braiding patterns of the world's large rivers. To this end, the present study aims to analyze post-dam planform characteristics of the Damodar River, a subtropical river in India, based on the analysis of meander geometry, Mueller’s sinuosity index, braiding index, channel count index, and channel length index during the last 50 years (1970–2020) using topographical maps and satellite images. The study also intends to forecast channel meandering and braiding characteristics for 2030 and 2050 using an Artificial Neural Network (ANN) model. The study results show that between 1970 and 2020, the standard sinuosity index (SSI) showed a larger tendency to meander in the middle of the river than the upper and lower courses owing to hydraulic control, while the lower and upper courses were controlled by topographic factors. Similarly, channel braiding indices (BI*, BI, and Pt) exhibit swelling in the upper and middle courses followed by a gradual fall in the lower stretch. The building of dams, the presence of lineaments, faults, and other anthropogenic controls primarily regulate the physical planform characteristics of the river. Regarding allometry, the river's upper segments exhibit both positive and negative allometry in certain combinations, whereas the lower segments primarily exhibit negative allometry. The study demonstrates that over the past 50 years, overall channel meandering has slightly decreased while braiding has slightly increased over time, indicating a quasi-equilibrium channel metamorphosis. However, the prediction with higher accuracy (80–95 %) shows that the river meandering and braiding (BI* and BI) will increase in the short run (2030), and decrease in the long (2050). The study findings may be helpful for the various planners and stakeholders involved in the development of the river basin.

TURBINE SPEED CONTROL

Provides analysis of hydraulic turbine control systems existing in the world and domestic practice. The design features of constructing circuits with discrete and discrete-analog control methods are considered. The schemes for controlling the speed of the turbine of the leading manufacturers of hydraulic turbine equipment are given: PO "LMZ" and ALSTOM POWER HYDRO (France, Grenoble). The given computer system of hydraulic turbine speed control guarantees trouble-free operation in case of load deviation and power failures. A fully automatic method of controlling the hydraulic unit is possible, in which the computer system controls the turbine independently, based on the parameters of the hydraulic unit operation taken into account by the sensors, in accordance with the program of the control computer. The control system constantly monitors the operation of the hydraulic turbine, adjusts its speed according to the load, performs adequate control operations. The analysis of the operation of the circuits is carried out, taking into account the specifics of the functioning of the regulation system. A mathematical model of the hydromechanical part of the regulator is considered for assessing the quality indicators of transient processes occurring in the process of starting, stopping and reversing a hydraulic turbine. It is shown that the development of theory and design methods using both approaches, mathematical models and control algorithms aimed at increasing the positioning accuracy and reliability of hydropneumatic systems with a possible simplification of circuit solutions is an important task aimed at obtaining a significant economic effect when solving this most important problem. The results obtained prove that the use of a positional hydraulicpneumatic drive for building a hydraulic turbine speed control system with discrete and discrete-analogue control makes it possible to synthesize a hydraulic pneumatic drive with high positioning accuracy, without the use of expensive hydraulic valves with proportional control.

An autonomous emergency braking strategy based on non‐linear model predictive deceleration control

AbstractSurrogate safety measures (SSM) are used to assess the risk for autonomous emergency braking system (AEBS). Developing appropriate SSM and accurately executing the braking request are the key issues. Time‐to‐collision (TTC) is a typical time‐based SSM with limitations. By analyzing the braking process, this paper proposes a new SSM based on deceleration rate to avoid collision (DRAC). As the brake actuator, vehicle electronic stability control (ESC) system has many problems, such as large overshoot and pressure fluctuation. Considering the model of hydraulic control unit (HCU) and vehicle, a deceleration controller based on non‐linear model predictive control (NMPC) is proposed. Based on this, a layered AEBS architecture is proposed. The upper‐layer AEBS controller calculates the expected deceleration based on modified DRAC (MDRAC), and transmits it to the lower‐layer NMPC deceleration controller. Finally, the simulation and experimental tests are carried out. The results show that the system has a fast and stable response. In addition, the performance of the proposed AEBS strategy is tested according to the Euro‐NCAP test protocol. Comparing the results with the TTC method, the proposed method can improve the stability of the distance margin by more than 0.55 m, which ensures the safety and improves the stability of the vehicle.

Random-walk-path solution of unsteady flow equations for general channel networks

The random walk path method (RWP) is a stochastic model that transforms the solution of the unsteady open channel flow equations into a probability problem. In this paper, this method is introduced to solve the discretized Saint-Venant equations, with probabilistic representation of the water levels at junctions. Different boundary conditions, which specify either water levels or discharge hydrographs, can be implemented by specifying how walkers react when arriving at the boundaries. The pointwise solution at river junctions can be obtained via random walk simulations. The efficacy of the model was verified against the following test cases: (1) a real-world looped channel example documented in the manual of the software Hec-Ras and (2) a hypothetical channel system consisting of dendritic and divergent networks. The number of random simulations is an important aspect of the RWP method and needs to be chosen by considering the trade-off between precision and computational efficiency. The impact of the boundary water level or discharge on the water levels at internal nodes can be quantitatively evaluated by adopting the terminal weights, which present a distinct advantage of the RWP method. This assessment of water levels can serve as a guide in the operation of hydraulic controls, such as dams, sluices and pumps, to effectively regulate the flow in mitigating flood risks.

New model for predicting terminal settling velocity and drag coefficient of the Oncomelania

This paper presents a study of the terminal settling velocity and drag coefficient of the Oncomelanias with highly irregular shape in the range of particle Reynolds number (10 < Rep < 600). The movement characteristics of the Oncomelanias with horizontal and slant postures are revealed using image analysis and wavelet analysis. The shape features of Oncomelanias with different dimensions are quantified and formulated. The authors propose a new model for predicting the drag coefficient of the dormant and active Oncomelanias, which is proven to be better than several widely-used formulas. Further, a simple settling velocity model that can predict the terminal velocity of the Oncomelanias fairly with several easy-to-measure parameters is developed. These findings provide a basis for the further improvement for the hydraulic schistosomiasis control project and supply reference for the settling characteristics and drag coefficient of cone-shaped particles.

Efficiency of a Twin-Two-Pump Hydraulic Power Pack with Pumps Equipped in Constant Pressure Regulators with Different Linear Performance Characteristics

The efficiency problem of hydraulic pump units with advanced double structures with constant pressure regulators with different linear characteristics in the case of work in an open supply system is presented in the paper. The main parts of the hydraulic power pack structure and pressure controller functions are described. The equation is given for the calculation of energy losses in particular pumps and the whole multi-pump power pack unit. The difference between the efficiency of particular pumps and the hydraulic pump unit was discussed.

Research on variable speed constant frequency energy generation based on deep learning for disordered ocean current energy

As one of the most promising new energy sources today, ocean current energy has become an important part of energy strategies. There are short-term disorderly fluctuations in the flow rate of ocean current energy. The uncontrolled input of kinetic energy from the ocean current can lead to poor quality of power generated by current energy generators. The existing technology of current energy generation uses mechanical rigid transmission, which is prone to fatigue damage and low reliability under variable load fluctuations. In this paper, a joint simulation platform based on AMESim and Simulink is constructed based on 50kW hydraulic transmission and control power generation equipment. This paper establishes a mathematical model of the hydraulic transmission control system and proposes a constant frequency control algorithm based on a deep learning prediction model to improve the steady-state accuracy of the hydraulic motor speed. This paper proposes a deep learning prediction model based on EWT (Empirical Wavelet Transform)-LSTM (Long Short-Term Memory)-CNN(Convolutional Neural Network), which improves the prediction accuracy by 12.26% compared to short-term memory neural network. The model improves the motor speed dynamic accuracy by 90%, the standard deviation index by 78.11%, and the maximum deviation by 86.10% compared to the feed-forward Proportional Integral Derivative (PID)control algorithm. Therefore, the model can effectively improve the quality of the system’s power generation. At the same time, the time cost of the model for a single prediction is less than the sampling time of other control algorithms. In this paper, the simulation results are verified by a 50kW hydraulic transmission control experimental bench. The constant frequency control algorithm based on the deep learning prediction model can effectively improve the constant frequency dynamic accuracy of the motor of the hydraulic transmission control power generation equipment, which in turn improves the system power generation quality.

The Elephant Marsh, Malawi – Part 2: two-dimensional hydrodynamic modelling in support of an eco-social assessment

The Elephant Marsh lies on the floodplain of the lower Shire River, in southern Malawi. It is both a cultivated, seasonal floodplain and a wetland, characterised by a complex mosaic of meandering channels, marshland and shallow lakes. In 2016, the Marsh was granted RAMSAR status based on a series of supporting studies, including the modelling of eco-social options for managing its ecological condition. This paper describes two-dimensional (2-D) hydrodynamic modelling using RMA2, in support of this eco-social assessment. The hydraulic model was parameterised using mostly existing data but augmented with bathymetric channel and lake surveys. Calibration and verification used water level data from the hydrometric network for the period 1999 to 2009. Generally, observed water level time-series are well replicated in the model, but there are large discrepancies prior to this period. These are due to temporal changes in hydraulic controls, mainly sedimentation, but also breaching of an embankment at the downstream end of the Marsh. Selected hydraulic-habitat variables (based on daily hydrological time-series 1976 to 2009) provide the indictors of hydrological and hydraulic change used to inform a DRIFT eco-social assessment. The Marsh displays moderate flood attenuation characteristics, but the importance of this will likely increase under continued sedimentation and predicted climate futures, which include more severe storms. The 2-D modelling contributes to an improved understanding of the Marsh’s hydraulic behaviour, particularly regarding anthropogenic influences since the early 1900s.

Bioinspired hydrogel jellyfish with mechanical flexibility and acoustic transparency

The uniqueness of soft materials such as hydrogels allows for great potential for new soft robots and actuators. Conventional underwater robots are generally crafted of rigid structures and materials with water-mismatched acoustic impedance, severely limiting their underwater operating capabilities. Therefore, flexible and acoustically transparent soft robots show great prospects for applications in marine exploration, biomedical engineering, etc. Inspired by the high water content of jellyfish, we report a hydraulically actuated bioinspired hydrogel jellyfish. The acoustic backscattered energy of the hydrogel jellyfish is reduced to about 1/270 compared with conventional underwater robots, achieving omnidirectional transparency under broadband acoustic detection from 10 kHz to 1 MHz. Moreover, the body length of hydrogel jellyfish can contract to about 1/3 of its original length under hydraulic control, exhibiting flexible motion to pass through narrow orifices. This design can potentially establish generic design principles for constructing next-generation mechanically flexible and acoustically transparent robots. • Jellyfish robot combines high water content of jellyfish and programmable hydrogel • Hydrogel jellyfish robot exhibits excellent acoustic transparency • High mechanical flexibility enables passing through narrow orifices Conventional underwater robots are generally crafted of rigid structures and materials with water-mismatched acoustic impedance. Inspired by jellyfish, Zhang et al. report a hydrogel jellyfish robot that achieves flexibility and near-water acoustic impedance. This work may establish design principles for constructing mechanically flexible and acoustic transparent robots.

Simulation studies around the steering system of the azimuthing propulsor

In this study, the steering load, the steering control and the gear failure of the steering system of the azimuthing propulsor are simulated and investigated respectively. In this research, CFD simulation was used to obtain the steering load moment for a azimuthing propulsor with different advance coefficients in the azimuthing range of 0∘ to 180∘. Then the simulation results were compared to the open water experiment results to analyze the reasons for the similarities and differences. Finally, the reason for the fluctuations and the fluctuations frequency calculation method were discussed. A co-simulation model of the gear transmission system and the hydraulic control system was built to simulate the steering control process. Due to the limited braking speed in small angle position feedback control, a speed feedback position control method was proposed. Taking into account the influence of fluctuating variable load on the hydraulic system pressure and the dynamic gear meshing force, the optimal control parameters were found, and the final control effect was significantly improved. In view of the pressure change of the hydraulic system contains a wealth of information on gear torsional vibration, the influence of gear failure on the hydraulic system pressure was discussed considering the two gear failure modes of broken teeth and uniform wear. The input load is divided into constant load and fluctuating load, and the test results was consistent which provides a basis for diagnosing azimuth gear faults.