Hydraulic Control Research Articles

Research on stability of hydraulic system based on nonlinear PID control

Abstract In order to avoid the interference of the excavator hydraulic control system by external factors, the output stability of the hydraulic control system has to be improved. The method introduces a nonlinear Proportional integral differentiation (PID) controller with deviation correction parameters through the simulation verification of the control effect and the creation of excavator hydraulic drive diagram. PID, whose full English name is proportional integral derivative, is a mathematical and physical term. The controller is modeled in Matlab/Simulink. Finally, the whole hydraulic system is co-simulated by the interface of AMESim and Matlab. The simulation results show that the system model realizes the co-simulation through the interface combination of the two software, which is more accurate than the traditional PID control, and the pressure and flow fluctuation are smaller, which can suppress the interference of external load mutation, and improve the stability of the hydraulic drive output of the excavator. The validity of the experiment is verified.

DEVELOPMENT AND APPLICATION OF THE DIGITAL TWIN OF THE HYDRAULIC CONTROL VALVE

The paper is focused on the development of the digital twin of the hydraulic control valve for continuous control of the oil flow – servovalve or control valve – and their use by the testing of the control system of the test rig for the measurement and evaluation of the characteristics of the valve. The structure of the mathematical model of the control valve enables to do the parameterisation for different types and sizes of the control valves only using the catalogue data delivered by the valve producers. In the next step the created and parameterized model is implemented into the dSpace MicroLabBox for the real time realisation of the digital twin. The MicroLabBox is equipped with the analogue inputs and outputs and allows the connection of the digital twin to the control system in the same way as the real servovalve. Finally, the characteristics of the valve are measured and evaluated using the HiL simulation of the digital twin. The digital twin of the servovalve allows the testing of the developed control system and software for the hydraulic test rig for the measurement of the valve characteristics without the need of the real valves different types.

Development Status and Research Progress of a Tractor Electro-Hydraulic Hitch System

A tractor electro-hydraulic hitch system is considered one of the most important systems that play a strategic role in the power transmission and operation depth control of a tractor’s field operation. Its performance directly affects the operation quality of the whole work unit of the tractor. Furthermore, a tractor electro-hydraulic hitch system has gained the interest of many in the agricultural machinery sector because of its stable performance, high production efficiency, good operation quality and its low energy consumption. To fully benefit from the potential of the tractor electro-hydraulic hitch system, it is significant to understand and address the problems and challenges associated with it. This study, therefore, aims to contribute to the development of the tractor electro-hydraulic hitch system by investigating the research methods, technical characteristics and emerging trends in three key aspects that include the tillage depth adjustment method, the tillage depth control algorithm and the core components of the electro-hydraulic hitch system. The characteristics and applicable conditions of the different tillage depth adjustment methods of the electro-hydraulic hitch system were summarized. The realization methods and the control characteristics of the different algorithms were elaborated and discussed for both the PID control algorithm and the intelligent control algorithm. The working characteristics of the core components of the electro-hydraulic hitch system were analyzed based on the hydraulic control valves and sensing elements. The results have shown that the multi-parameter tillage depth adjustment method met the operation quality standard while taking the engine load stability and traction efficiency into account, and it has a greater research significance and value. The working quality can be improved effectively by introducing the intelligent algorithm. In addition, the study of smart valves with built-in sensing elements and how to improve the anti-interference ability of sensing elements, are the aspects that requires further consideration. Aiming to improve the working quality and reduce energy consumption, further research into the tractor electro-hydraulic hitch system is necessary. The results of this comprehensive review provide a reference for the intelligent operation of tractors under the precision agriculture.

Effects of thermophysical parameters of fracturing fluid on hot dry rock damage in hydraulic fracturing

Hydraulic fracturing plays a crucial role in the exploitation of hot dry rocks (HDR). However, the effects of the thermophysical parameter of hydraulic fracturing fluid on rock damage mechanism are still not well understood. The study aims at analyzing the influence of thermophysical parameters of fracturing fluid on the damage of HDR through numerical and analytical methods. It is found that the increase of density and specific heat capacity decrease rock damage volume, while the thermal conductivity rises rock damage volume. In addition, the impacts of volume compressions and viscosity on rock damage are not always promoted or inhibited, but change. Liquid permeability is defined in this study, which is found that low liquid permeability results in a larger volume of rock damage. The results would provide guidance for fracturing fluid configuration and hydraulic fracturing process control.

Economic Analysis of Flood Risk Applied to the Rehabilitation of Drainage Networks

Over time, cities have grown, developing various activities and accumulating important economic assets. Floods are a problem that worry city administrators who seek to make cities more resilient and safer. This increase in flood events is due to different causes: poor planning, population increase, aging of networks, etc. However, the two main causes for the increase in urban flooding are the increment in frequency of extreme rainfall, generated mainly by climate change, and the increase in urbanized areas in cities, which reduce green areas, decreasing the percentage of water that seeps naturally into the soil. As a contribution to solve these problems, the work presented shows a method to rehabilitate drainage networks that contemplates implementing different actions in the network: renovation of pipes, construction of storm tanks and installation of hydraulic controls. This work focuses on evaluating the flood risk in economic terms. To achieve this, the expected annual damage from floods and the annual investments in infrastructure to control floods are estimated. These two terms are used to form an objective function to be minimized. To evaluate this objective function, an optimization model is presented that incorporates a genetic algorithm to find the best solutions to the problem; the hydraulic analysis of the network is performed with the SWMM model. This work also presents a strategy to reduce computation times by reducing the search space focused mainly on large networks. This is intended to show a complete and robust methodology that can be used by managers and administrators of drainage networks in cities.

Evaluation of Select Velocity Measurement Techniques for Estimating Discharge in Small Streams across the United States

ABSTRACTMultiple instruments and methods exist for collecting discrete streamflow measurements in small streams with low flows, defined here as less than 5.7 m3/s (200 ft3/s). Included in the available methods are low‐cost approaches that are infrequently used, in part, because their uncertainty is not well known. In this work, we evaluated the accuracy and suitability of three low‐cost velocity measurement methods (surface float [SF], velocity head rod [VR], and rising body [RB]) and three conventional current meters (acoustic Doppler velocimeter, and mechanical Price type AA and Price Pygmy meters) relative to discharge calculated from stable artificial hydraulic controls. A total of 231 measurements were made by 20 individuals during 88 site visits to 24 sites in eight states. Accuracies were assessed for all methods and precision was evaluated for the low‐cost methods. The median percent error was below 5% for conventional methods, and below 20% for the low‐cost methods. The SF was the most accurate (median absolute percent error 14%) and precise (mean percent precision of 11%) low‐cost method. The RB and VR, respectively, had 15% and 20% median absolute percent error and 29% and 12% mean percent precision. Results suggest that low‐cost methods, when used appropriately, can be used to estimate discharge data under low flow conditions when measurements with conventional methods are not feasible and the associated accuracies meet end‐user measurement objectives.

Investigation on the sealing performance of polymers at ultra high pressures

Abstract In this paper, the parameters affecting the sealing life of UHMWPE and PTFE in ultra high pressure systems were investigated. A life test system was designed and manufactured in which different parameters can be tested in the sealing construction. The life test system consists of two hydraulic pressure intensifiers, and a hydraulic and electronic control unit. The effects of the extrusion gap, piston rod material and surface roughness, in addition to the material, geometry and number of the sealing elements, on the life of the sealing members were investigated. Two levels were determined for each parameter, and experiments were carried out at a pressure of 450 MPa according to a Taguchi L8 orthogonal experimental design. Pressure intensifiers were operated reciprocatively, thus allowing to perform two tests simultaneously, saving time. Working cycles of the pressure intensifiers were measured. Each experiment continued until the seals were damaged, and a critical leakage rate occurred at the pressure intensifiers. ANOVA was applied to the experimental results. According to the results, the most significant parameter affecting the sealing life is the extrusion gap with a rate of 77%, followed by the piston rod surface roughness with a rate of 13%, and the piston rod material with a rate of 4%. The effects of the remaining parameters on the sealing life are more limited. The results obtained will contribute to the industrial design of sealing structures for ultra-high pressures.

Numerical Analysis of Energy Recovery of Hybrid Loader Actuators Based on Parameters Optimization

The conventional loader actuator hydraulic system suffers from the potential energy waste problem of the boom arm. This study proposes a hydraulic control method and control strategy for the energy recovery and regeneration of a hybrid loader arm. When the boom arm drops, the piston side of the boom cylinder charges the accumulator, and the system achieves energy recovery. When the boom arm rises, the accumulator releases hydraulic energy to drive the energy regeneration hydraulic motor to provide energy for the system, and the system achieves energy regeneration. The system’s principle analysis and the mathematical model are completed based on Boyle’s, Newton’s second law, and the flow continuity principle. The simulation model is established using AMESim 2D mechanical library, HCD library, and signal library. Under the typical working condition, 50-type wheel loader numerical simulation research is conducted, and the system cylinder motion characteristics, accumulator charging and discharging performance, system energy recovery, and regeneration performance are obtained. On this basis, energy recovery and regeneration efficiency are selected as optimization objectives. The optimal designs of accumulator and energy regeneration hydraulic motor parameters are carried out to obtain the influence law of accumulator and hydraulic motor parameters on system energy recovery and regeneration, and the energy-saving effect of the system is analyzed. The results show that the optimized parameters effectively improve the system energy recovery and regeneration efficiency and reduce engine fuel consumption. The system provides a reference for designing an energy recovery system and researching the energy-saving technology of loaders.

Innovative tidal control successfully promotes saltmarsh restoration

The reduction of saltmarsh habitat at a global scale has seen a concomitant loss of associated ecosystem services. As such, there is a need and a push for habitat rehabilitation. This study examined an innovative saltmarsh restoration project in Australia which sought to address the threats of mangrove encroachment and sea level rise. The project was implemented in 2017, using automated hydraulic control gates, termed “SmartGates,” to lower the tidal regime over one site, effectively reversing sea level rise at a local level. Measured indicators of saltmarsh cover, number of species, seedling counts, and saltmarsh assemblages all showed significant positive development over time, with trends varying based on saltmarsh zone. The saltmarsh, predominantly Sarcocornia quinqueflora, developed from remnant supralittoral (previously high) marsh which remained at 45% cover to achieve over 15% coverage across the cleared habitat after 3 years. Slower development in the low marsh (<5%) compared to other zones contrasts with other saltmarsh restoration studies which may be due to the unique nature of the restoration method or the nature of Australian saltmarsh species which favor higher elevations and drier conditions. The development of saltmarsh at the treatment site was found to track toward that at comparison sites over time, becoming similar to some comparison sites by the studies end. This study highlights the usefulness of the novel restoration method used and of the measured indicators for assessing saltmarsh development. This innovative tidal control method could play an important role in the future of saltmarsh restoration worldwide.

Research on Direct Yaw Moment Control of Electric Vehicles Based on Electrohydraulic Joint Action

To solve the problem of lateral instability of the vehicle caused by insufficient lateral force of the tires due to the insufficient torque provided by the motor to the tire when the vehicle turns sharply or avoids obstacles in an emergency, a layered control method is used to design a lateral stability control system. The upper decision layer selects the yaw rate and the sideslip angle of the center of mass as the control variables and uses the joint state deviation of the yaw rate and the sideslip angle of the center of mass and the rate of change of the deviation as the input of the sliding mode variable structure controller to calculate the additional yaw moment required to maintain vehicle stability. The lower torque distribution layer realizes the distribution of torque through the electro-hydraulic coordinated control method: the torque distribution rule based on real-time load transfer calculates the torque corresponding to the control wheel and generates the torque through the hub motor and transmits it to the wheel. When the torque output from the motor cannot provide sufficient torque for the vehicle, hydraulic braking is used as a compensating control, and the difference between the required yaw torque and the motor-generated yaw torque is used as the required torque for hydraulic control to calculate the wheel cylinder pressure required to brake the wheels. Based on the joint simulation model of MATLAB/Simulink and Carsim, the sine and double shift line working condition are selected for stability simulation experiments. From the simulation results, it can be seen that the yaw rate and sideslip angle of the center of mass of the vehicle with sliding mode control and electro-hydraulic coordinated control almost coincide with the ideal value curve, which are both smaller than the output parameters of the uncontrolled vehicle. From the perspective of the motor output torque, compared with pure motor control, the effect of electro-hydraulic coordinated control is better, and the hydraulic system can compensate for the braking torque in time and enhance the lateral stability of the vehicle. The designed control strategy can make the yaw rate and the sideslip angle of the center of mass of the vehicle follow the reference value better, which can effectively avoid the vehicle sideslip and instability and improve the vehicle yaw stability and driving safety. However, due to the limitations of experimental equipment, the proposed method could not be applied to the real vehicle test. The real vehicle test can better test the control effect of the proposed method.

Design of Bi-directional Pump Servo System for Asymmetric Hydraulic Cylinder

In view of the shortcomings of the traditional overflow pressure regulating and throttling speed regulation system, such as large energy loss, high oil temperature and large reversing impact, a servo two-way pump control system for asymmetric hydraulic cylinder is proposed based on Siemens S120. TIA Portal And Starter software are used for the design of hardware configuration and program debugging. SimulationX is used to simulate the stroke process of the hydraulic cylinder, at the same time, experimental verification was carried out, which provides a new idea for the low energy consumption design of hydraulic cylinder servo control system, and has important practical significance.

刷辊式葡萄藤防寒土清土装置参数优化与试验研究

Aiming at the problems of low efficiency, and low degree of mechanization of artificial soil clearing and considering that grapevines are easy to be damaged in northern China, a brush roll grapevine cold-proof soil clearing device suitable for removing soil in northern grape planting areas is studied and designed. The machine is mainly composed of a suspension device, soil removing device, hydraulic control system, telescopic device, etc. In this paper, a brush roll grapevine cold-proof soil clearing device was fabricated to investigate critical parameters such as rotation rate of soil removing device, brush spacing, and brush wire length on the machine performance. The three-factor and three-level quadratic regression orthogonal tests were carried out with the rotation rate of soil removing device, brush spacing, and brush wire length were taken as experimental factors and the soil removal rate and soil clearing distance were used as the evaluation indexes of soil clearing effect. The results show that the influence order of three factors on the soil removal rate was: rotation rate of soil removing device > brush spacing > brush wire length. The order of influence on the soil clearing distance was: rotation rate of soil removing device > brush wire length > brush spacing. The results show that when the rotation rate of the soil removing device was 248.71 r/min, brush spacing was 18.84 mm and brush wire length was 329.3 mm, the soil removal rate was 91.62% and the soil clearing distance was 11.63 cm. The relative error between the experimental verification value and the theoretical optimization value is less than 4%. This study provides the theoretical basis for the development of other types of grapevine coldproof soil clearing devices.

A Variable Pressure Multi-Pressure Rail System Design for Agricultural Applications

This paper presents a solution for reducing energy loss in the hydraulic control system of agricultural tractors and their implements. The solution is referred to as a multi-pressure rail (MPR) and provides power to the hydraulic functions following a pressure control logic, as opposed to the traditional flow control logic typical of hydraulic systems used in off-road vehicles. The proposed hydraulic control system allows for elimination of redundant flow control valves in the state-of-the-art system, which cause excessive throttling losses leading to poor overall energy efficiency. Related work on MPR technology targets construction vehicles, where the MPR solution can allow energy recovery during overrunning loads and better engine management. This paper alternatively addresses the case of agricultural applications where functions mostly operate under resistive load conditions with slow dynamics, which offers an opportunity to target throttle losses. For this purpose, the paper introduces a variable pressure control strategy to handle the instantaneous pressure at each rail. To develop both the controller and the hydraulic system architecture, a stationary test rig is conceived and used to validate a numerical simulation model of the MPR system and its control strategy. Particular focus is given to the dynamic behavior of the system during the switches of a function between different pressure rails, which needs to ensure reduced oscillations of the flow provided to each hydraulic function. Once validated, the simulation model is used to predict the energy savings of the MPR solution in an actual application: a 435 hp hydraulic tractor powering a 16-row planter, for which operating features during typical drive cycles were available to the authors. The results show up to 59% total power reduction at the pump shaft, corresponding to 89.8% system efficiency gain.

Optimal analysis of VSL following-up performance considering hydraulic system SAD control strategy

Hydraulic system lubricating oil is subject to serialized Variable Static Loads (VSL) following-up performance. An improved Self-Turbulent Flow (STF) algorithm, based on the real-time acquisition and monitoring of Lubricating Oil Static Pressure (LOSP) in hydraulic system to simulate VSL, is proposed. In this topic, a mathematical model of the Electro-Hydraulic Servo (EHS) control system for LOSP acquisition is presented, and the STF controller is designed for numerical analysis. The Self-Anti-Disturbance (SAD) control strategy for LOSP of EHS system is discussed, which is used for quadratic optimization, pole placement, PID and STF control, and the LOSP simulation model of STF control is constructed by SIMULINK module. Numerical simulation results indicate that the overshoot is significantly reduced. The proposed SAD control algorithm is verified by experiments, and the LOSP acquisition followability and monitoring accuracy are greatly improved. Toward this goal, a variable hydraulic LOSP acquisition and monitoring can be effectively and stability adjusted by pre-designed EHS control system in the field of power hydraulic fluid lubrication.

A Novel Reference Governor for Disturbance Observer-Based Load Pressure Control in a Dual-Actuator-Driven Electrohydraulic Actuator

In real-world applications, hydraulic pressure control performance is influenced by model uncertainties, the control bandwidths of valves and pumps, and deviations from the linear working region. To overcome the aforementioned obstacles, a novel reference governor for disturbance observer (DOB)-based load pressure control is proposed in this paper for a dual-actuator-driven electrohydraulic cylinder. First, a control-oriented model for load pressure control was developed. On the basis of this, a nonlinear DOB-based feedback controller, as well as a mid-range control architecture for the variable displacement pump and proportional valve, was fabricated so that the performance degradation caused by the pump’s slow responses and imprecise system parameters is suppressed. Specifically, this controller is augmented by a novel smooth reference governor, which modifies the load pressure command in the pressure transition periods to guarantee that the actuator’s constraints are not violated. Another merit of the novel reference governor is that it ensures a smooth trajectory transition, and therefore, unmodeled high-frequency plant dynamics will not be invoked. Case studies were carried out to verify the effectiveness of the proposed control approach. The study results show that the approach can significantly enhance the hydraulic system’s pressure tracking performance.

Optimization of the Load Capacity System of Powered Roof Support: A Review

Powered roof support is equipped with a hydraulic control system to ensure its required load capacity. The main problem arising from powered roof support during exploitation is providing the necessary load capacity. A decrease in load capacity is mainly associated with internal and external leakage in the cylinders, mainly in the hydraulic props. The hydraulic prop’s role is to ensure stability for the powered roof support. A special double block with an additional pressure boost was developed to counter the props’ leakage phenomenon. Pressure loss is replenished based on the solution proposed here. For this purpose, bench tests were commenced, in which a prop with an internal leakage was used. The research included the analysis of the operation of a boosted double block. The results allowed us to assess whether the developed solution can be the subject of further research conducted in real conditions.

Research on Mechanical Properties and Damage Evolution of Pultruded Sheet for Wind Turbine Blades.

In order to explore the mechanical properties, failure mode, and damage evolution process of pultruded sheets for wind turbine blades, a tensile testing machine for pultruded sheets for wind turbine blades was built, and the hydraulic system, mechanical structure, and control scheme of the testing machine were designed. The feasibility of the mechanical structure was verified by numerical simulation, and the control system was simulated by MATLAB software. Then, based on the built testing machine, the static tensile test of the pultruded sheet was carried out to study the mechanical properties and failure mode of the pultruded sheet. Finally, an infrared thermal imager was used to monitor the temperature change on the surface of the test piece, and the temperature change law and damage evolution process of the test piece during the whole process were studied. The results show that the design scheme of the testing machine was accurate and feasible. The maximum stress occurred in the beam after loading the support, the maximum stress was 280.18 MPa, and the maximum displacement was 0.665 mm, which did not exceed its structural stress-strain limit. At the same time, the control system met the test requirements and had a good follow-up control effect. The failure load of the pultruded sheet was 800 kN. The failure deformation form included three stages of elasticity, yield, and fracture, and the finite element analysis data were in good agreement with the test results. The failure modes were fiber breakage, delamination, and interfacial debonding. The surface temperature of the specimen first decreased linearly, and then continued to increase. The strain and temperature trend were consistent with time.

Renovation of Crane Control System of Reach Stalker Ferari 178h1 Using Avr Atmega2560

Container rental service companies or container parking facilities providers need container transportation equipment such as Crane Reach Stalker to move and arrange containers. Several container services companies in Surabaya such as Citra Mandiri Sejati have a Crane Reach Stalker made by Ferari Italy which experienced damage to the electrical control. After observing the control unit, the damage was in the hardware comparison system and the relay control used. Dealing with these problems, planning and improvement of the total control system were carried out using the ATMega2560 AVR microcontroller. However, the problem becomes complex and requires cooperation with Hydraulic control partners when the entire system must be resolved. From the renovation work on the Ferari 178H1 Load Handling Crane system for a year, it was obtained that the Load Handling control input data in which it was a joystick and a 3 positions button with an output level of 0 and 9 volts. Hydraulic control uses a Solenoid Valve type 4/3 with 2 input control coils, and in overall system testing, the average length of time for the movement of the Piston Crane is 6 to 12 seconds. From the test results using a 40 tons container load, it was stated by the Crane driver that the time used to carry out Load Handling for the Hydraulic type and the Crane's age was suitable and appropriate.

Renovation of Crane Control System of Reach Stalker Ferari 178h1 Using Avr Atmega2560

Container rental service companies or container parking facilities providers need container transportation equipment such as Crane Reach Stalker to move and arrange containers. Several container services companies in Surabaya such as Citra Mandiri Sejati have a Crane Reach Stalker made by Ferari Italy which experienced damage to the electrical control. After observing the control unit, the damage was in the hardware comparison system and the relay control used. Dealing with these problems, planning and improvement of the total control system were carried out using the ATMega2560 AVR microcontroller. However, the problem becomes complex and requires cooperation with Hydraulic control partners when the entire system must be resolved. From the renovation work on the Ferari 178H1 Load Handling Crane system for a year, it was obtained that the Load Handling control input data in which it was a joystick and a 3 positions button with an output level of 0 and 9 volts. Hydraulic control uses a Solenoid Valve type 4/3 with 2 input control coils, and in overall system testing, the average length of time for the movement of the Piston Crane is 6 to 12 seconds. From the test results using a 40 tons container load, it was stated by the Crane driver that the time used to carry out Load Handling for the Hydraulic type and the Crane's age was suitable and appropriate. Â

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.