Hydraulic Oil Pressure Research Articles

自动驾驶拖拉机电液耦合转向特性研究

To solve the problem of poor steering performance of existing self-driving tractors based on electro-hydraulic coupled steering systems (E-HCSS) under multiple influencing factors, the research on electro-hydraulic coupled steering characteristics of self-driving tractors was carried out in this paper. Taking the electro-hydraulic coupled steering system as the research object, the E-HCSS test bench of the tractor was built, and the influencing factors affecting the responsiveness of the steering process were obtained through theoretical analysis: hydraulic fluid temperature, oil supply pressure and driving speed. The hydraulic fluid temperature, oil supply pressure and driving speed were taken as the test factors, and the steering system response time and response error were taken as the performance indexes for the single-factor steering test and orthogonal test. By establishing the regression mathematical model between the influencing factors and the indexes, the interactive influence of the factors on the indexes was analyzed, the optimal parameter combination was obtained, and the optimization results were verified. The test results indicated that the tractor electro-hydraulic coupling steering system could achieve good steering performance under the optimal parameter combination, and the optimal parameter combination was: hydraulic oil temperature 60°C, hydraulic oil pressure 15 MPa and driving speed 8 km/h. The study's results were as follows: hydraulic oil temperature 60°C, hydraulic oil pressure 15 MPa and driving speed 8 km/h. The study's results could provide a reference for the steering control of the self-driving tractor, the design of the self-driving steering system and the optimization of the parameters.

A Laboratory Machine Verifying the Operation of a Hydraulic Rope Equalizer with Tensometric Sensors.

In mining machines with friction discs, but also in multi-rope traction elevators, it is necessary to distribute the applied tensile load, generated by the weight of the cage and counterweight, evenly in all cross-sections of the load-bearing ropes. Hydraulic devices used for this purpose can operate on the principle of Pascal's law. This article presents a structural design, a 3D model and an implemented solution of a laboratory device capable of simulating a practical method of evenly distributing the total weight of the load into partial tensile forces of the same size acting on a selected number of load-bearing ropes. The laboratory equipment uses two pairs of three steel cables of finite length for the simulations. During the experimental measurements, tensile forces derived from the tractive force of the piston rods, pushed into the bodies of the hydraulic cylinders by the pressure of the hydraulic oil supplied through the pipeline under the pistons of the hydraulic cylinders, were detected. The resulting amount of hydraulic oil pressure in the hydraulic circuit influenced by different values of the hydraulic oil pressures in the hydraulic cylinders and by the pressure in the supply pipe was experimentally studied on the laboratory equipment. Simulations were also carried out in order to detect the hydraulic oil pressure in the hydraulic circuit caused by the change in the different magnitudes of the tensile forces in the ropes. From the experiments carried out, it follows that with the appropriate choice of hydraulic elements and the design of the hydraulic circuit, the weight of the load, acting as the total pulling force in the ropes, can be evenly distributed (with a deviation of up to 5%) to all cross-sections of the load-bearing ropes. If the exact values of the hydraulic oil volumes under the pistons of all hydraulic cylinders are not known, it is not possible to calculate the pressure values in the hydraulic circuit when the valves of the hydraulic pipes are gradually opened.

Influences of abrasive particles on tribological behaviours of rotary vane steering gear seals under oil

The wear particles often cause the abnormal wear processes to the rotary vane seals, which lead to seals failure and dropping hydraulic oil pressure, and eventually result in losing of the function of rotary vane steering gear. Clarifying the friction and wear mechanisms between the vane seals and the cylinders and extracting their key wear characteristics are the keys to extend the service life and realize intelligent fault diagnosis of the rotary vane steering gears. Different kinds of hydraulic oils mixed up with different sizes of iron particles were chosen to investigate the abrasive particles on the wear behaviours between the polyurethane polymer and carbon steel specimens. The wear characteristics such as coefficients of friction (COF), wear morphologies, frictional-induced vibration signals were examined and analyzed synthetically. The results showed that the coefficients of friction, wear morphologies, surface roughnesses and vibration signals increased as a function of the iron particle sizes, which indicated that the wear state was gradually worsening. The three-body friction and wear mechanisms were disclosed clearly. There was a certain mapping relationship between the wear characteristics and wear states, and sensing the tribological information between the rubbing pairs, including coefficient of friction, abrasive particle size in hydraulic oil, wear morphology, vibration signal and other characteristics, was a potential and effective way for evaluating or predicting the wear states or failure modes of rotary vane steering gear seals. This study provides a theoretical basis for revealing the friction and wear mechanisms of ship rotary vane steering gear seals, and is useful for accomplishing their intelligent monitoring and fault diagnosis.

A novel approach to improve quality of delivered concrete using slump estimations of the ready-mixed concrete (RMC) truck mixer

Slump is an effective parameter in concrete quality control. It does affect the ease with which concrete can be transported, placed, and screeded, and is a relatively reliable indicator of batch-to-batch variability. Accordingly, monitoring the concrete Slump and fluidity while transporting is a proper response to many concerns in the concrete industry. Despite the aging of the existing concrete trucks, determining the relationship between the data obtained from the truck mixer and the slump, requires careful study of the components of the truck's drum. However, an advanced model for determining the slump of fresh concrete in a transporting truck, has not been presented. In this study, the relationship between a concrete Slump and hydraulic oil pressure at different drum rotation speeds and different weights has been investigated through a suitable regression model (linear or power) regarding its trendline. Moreover, using the Computational Fluid Dynamics (CFD), numerical slump model, and drum rotation, and the output power was investigated. The results clarified that by increasing the concrete weight from 6608 to 16500 kg, the hydraulic oil pressure increases 10 bar approximately. Also, changing the drum's rotation speed from 5 to 20 rpm increases the hydraulic oil pressure by 22%, while the changes in the mix design do not have much effect on the hydraulic oil pressure. Based on the results obtained for the relationship between slump value and measurable parameters in the truck mixer, a new approach to improving the quality the ready-mixed concrete (RMC) in construction projects is presented.

Modelica-based simulation and optimization of design parameters of RAT actuator

The actuator is the key to ensure the normal startup and operation of the ram air turbine (RAT) system. In order to improve the reliability of the actuator of the RAT system, we propose a RAT actuator simulation modeling and design parameter optimization method based on the multi domain unified modeling language Modelica. Firstly, a fault tree is established to identify the components that cause the main failure modes of the actuator based on the actual cases of the RAT. Secondly, the model of RAT actuator is built by using Modelica language. The correctness of the model is verified by comparing with the actual use, with the error of about 3.78%. Finally, in order to avoid oil leakage caused by excessive hydraulic oil pressure, under the premise of meeting the constraints of the actuator deployment time and the end deployment speed, the optimal design parameters are determined by simulation when the peak pressure of the hydraulic oil is minimized. The research results can provide reference for the forward design of RAT in China and have good engineering application value.

Damage and fracture of gun barrel under wear-fatigue interaction

Gun, projectile and propellant are three fundamental components of a launching system. Generally, a barrel has to be condemned after a number of rounds have been fired. During the total useful life of gun barrel, it bears severe damage induced from erosion by high pressure and high temperature propellant combustion gas, and wear due to high speed friction between projectile and gun bore. Meanwhile, the gun barrel undergoes a dynamic loading of gas pressure, mechanical stress and thermal stress when firing a round. Thousands of firing cycles lead to gun barrel fatigue. Interaction of wear, including erosion, and fatigue damages the gun barrel and eventually the gun will become inaccurate because of wearing away gun bore materials. However, a gun barrel will fracture in a sudden manner because of fatigue. It is found that microcracks form on the bore surface after only a few rounds have been fired, which lays the foundation for growth and propagation of cracks under fatigue loading. In this paper, laboratory hydraulic fatigue tests were carried out on a tube with pre-machined crack on its inner surface by using an MTS 809. Strain gauges were adhered to the outer surface of the tube to monitor strain during testing process. The hydraulic oil pressure was measured by a pressure sensor. The experimental results show that there are three stages of outer surface strain variation, namely stable increase, fast increase and abrupt increase, which corresponds to the history of crack evolution. Crack grew stably in the initial stage under cycle of loading and a major crack is gradually formed. When the major crack size reaches a certain value, the propagation velocity of crack is accelerated fast and the critical size is reached in a short time. Eventually the tube fractured suddenly. The experimental findings will help us to gain new insight into the physical mechanism of fatigue and fracture of gun barrel and provide a possible method to evaluate health of gun barrel in service.

Development of the Hydro Static Wind Turbine Powered RO System for Maximum Power Point and Maximum Permeate Flow Tracking

Wind energy is one of the cheapest sources of energy that may solve the Climate change problem and fresh water scarcity challenges. This article introduces a novel Desalination Wind Turbine that is cheaper and more efficient than the common wind turbine, especially offshore wind turbines. In this system, the wind energy transmitted to the water pump by a hydraulic transmission line. The RO module is used for fresh water production. The pressure recovery module is added to RO system, to increase the permeated flow. It can be increased the permeate flow up to 45%, which is significant. The Maximum Power Point Tracking (MPPT) based on the hydraulic oil pressure measurement is implemented. In addition, the Maximum Permeate Flow Tracking control loop, similar to MPPT, is introduced to optimized the pressure of the RO system. It is increased the annual permeate production up to 8%. The long term performance of the system, such as annual water production is calculated and the ability of the system to MPPT and the wind turbulence and gust is analyzed. The rotor speed overshoot of the closed loop system is less than 16%, which is acceptable.

Control and data acquisition system for rotary compressor

The rotary compressor (crimping machine) is a machine designed for making hollow forgings. The rotary compressor is a prototype device designed and built at the Technical University of Lublin. The compressor is dedicated to perform laboratory tests related to the hollow forgings of various shapes using different materials. Since the rotary compressor is an experimental device, there is no control and acquisition data system available. The article presents the concept and the capabilities of the computer control and data acquisition system supporting rotary compressing process. The main task of software system is acquisition of force and kinetic parameters related to the analysed process of the rotary forging compression. The software allows the user to declare the course of the forming forgings. This system allows current recording and analysis of four physical values: feed rate (speed of working head movement), hydraulic oil pressure at inlet and outlet of hydraulic cylinder and the torque of engine. Application functions can be divided into three groups: the configuration of the pressing process, the acquisition and analysis of data from the pressing process and the recording and presentation of stored results. The article contains a detailed description about hardware and software implementation of mentioned functions.

Analysis of the Hydraulic Impact of the Wind Turbine Hydraulic Yaw Brake System

When the wind turbine hydraulic yaw system brake and pressure relief, hydraulic oil pressure in the hydraulic system is rapidly reduced, and its direction of flow has also undergone dramatic change. Hydraulic impact generated easily make equipment failure by mutations pressure in pipeline. For there is the larger hydraulic impact problem when hydraulic yaw brake system change direction, this paper has analyzed the reasons resulting hydraulic impact, and has established the mathematical model of the yaw brake system pressure relief oil passage, and then has proposed to the methods of reducing the hydraulic impact in the commutation process. The simulation results show that the methods of extend the hydraulic cylinder commutation time may well reduce the hydraulic impact when the wind turbine hydraulic yaw system brake and pressure relief. It has significantly changed its pressure curve. It can reduce the hydraulic impact damage to the equipment. Then it verify the feasibility of this method.

Dynamic performance of suction valve in stepless capacity regulation system for large-scale reciprocating compressor

Regulating capacity by controlling suction valve has a good application value for the large-scale reciprocating compressor used in the petrochemical industries. A mathematical model coupled with compressor, actuator and hydraulic system is built in this paper, and some performances of the system are tested by the experiment. The results show that the maximum displacement of actuator increases with the oil pressure until it is limited by the lift limiter. The low hydraulic oil pressure leads to the partially opened condition of suction valve, and the valve plate impacts on the actuator at the same time, which influences the accuracy of indicated powers and mass flow rate. The reset response time of valve plate cannot be improved by increasing oil pressure after the actuator is completely opened. The mass flow rate decreases with the hold time after the closing process of suction valve is delayed until nothing is discharged. The reset response time can be improved by increasing the reset spring stiffness and the path diameter of solenoid valve, or decreasing diameter of hydraulic cylinder. All the power consumption and mass flow rate decrease apparently caused by the delayed compression process. The power consumption decreases 21% when the capacity is 70% of the full load based on the experiment.

The Application of HPWM in Improving Vehicle Lateral Stability

The application of the High-frequency pulse width modulation (HPWM) for improving vehicle lateral stability is investigated in the paper. Firstly, a hydraulic control unit (HCU) combined with a high-speed switching valve (HSV) for controlling hydraulic oil pressure by adjusting duty cycle is presented. Then, a typical control strategy is described based on the application of HPWM. Finally, by using a 15dofs vehicle model, a simulation is carried out to investigate the role of HPWM on improving vehicle lateral stability. The results show that HPWM is capable to control the output pressure of HSV accurately and improve vehicle lateral stability effectively.

The Performance of the Hydraulic Expansion Toolholder in High-Speed Rotation

On the basis of finite element analysis, the static transmitted torque of Hydraulic Expansion Toolholder is validated. At the same time fluid analysis software is used to investigate the oil pressure changes in oil chamber wall because of different rotation speed. Then through the fluid-solid coupling, the article analyzes the chuck clamping performance on the factors of expansion chuck and tool clearance, rotation speed, and hydraulic oil pressure when toolholder on the state of high rotation speed.

IDENTIFY SUITABLE HYDRAULIC FACTORS FOR CONTROL RAISE AND LOWER LASER SCRAPERS

The present work was carried out in private farm at Hoash Essa – Behera governorate during agriculture season of 2008 in clay soil. The aim of this experiment is to study the relation between the tractor hydraulics, hydro-electric valves, scraper cylinder, raise and lower scraper paled, scraper load and their effects on the laser land leveling efficiency. An area of (6 feddans) was divided into 2 plots; each plot was leveled with different scraper. Two scrapers were used 3 and 3.6 m width (10 and 12 feet). Each plot was surveyed and calculated the volume of cut (m3). The hydraulic of oil pressure (bar) and hydraulic of oil flow rate (l/min) were measured with the scraper raise (every 0.5 cm) and computed the volume of soil fill (m3). Also, the actual capacity of scrapers volume m3, amount of earth moving m3/h and laser efficiency were calculated. The results showed that, actual scrapers loaded were 69 and 70.50 % (from theoretical loaded) with 3 and 3.6m scraper width, respectively. Maximum pressure needed to raise scraper was 52 and 110 bar with 3 and 3.6m scraper width, respectively. Maximum oil flow rate was 18.5 and 38.00 l/min. with 3 and 3.6m scraper width respectively. Scrapers field capacities were 10.88 and 16.96 m3/h with 3 and 3.6m scraper width, respectively. Every cubic meter of soil needed to 52 bars and 18.5 l/min. oil flow rate to fill area 25 m2 with 4 cm depth. The scraper capacity efficiency increased by increasing cutting depth, it was increased from 6.94 to 69.44% by increasing cutting depth from 0.5 to 4 cm for 3 meter scrapers width also it was increased from 4.63 to 70.73% by increasing cutting depth from 0.5 to 4 cm for 3.6 meter scrapers width. The predicted equations help engineering computer designers to make decision easily and determine the actual hydraulic oil pressure and oil flow rate to move the amount of earth.

油圧駆動電子制御システムによるエンジン性能の向上

During the past several years we have been intereseted in and have conducted research and development on the electronic control technology of marine diesel engines.In the electronically controlled engine, the inlet valve, the exhaust valve and the fuel injection valve are driven by a hydraulically powered system. We decided to use a solenoid valve, which is superb in reliability, for the electro-hydrauslic conversion part which converts the electric signal into hydraulic oil pressure in the hydraulically powered system. We successfully developed a high-speed solenoid valve which operates in 1 msec. Then, a micro-computer based digital control system was chosen for the control equipment which plays a major role in the hydraulically powered electronic control system. An engine simulator was also developed to confirm the operation and checked the functions of the electronic control equipment. After fully confirming its relibability, the electronic control equipment was connected to an actual engine, which produced favorable operation results.This paper describes the fruit of The Technological Research Association of Highly Reliable Marine Propulsion Plant.

平面研削における油圧の脈動に起因するびびりマークの抑制

平面研削における油圧の脈動に起因するびびりマークの抑制

Minute vibrations in precision surface grinding —Their causes and suppression

This paper deals with various minute vibrations in surface grinding, which produce various undesirable chatter marks on the ground surfaces. From the frequency analysis of the minute vibrations during grinding, it has been found that the vibration due to the unbalance of the grinding wheel spindle, the tuning-fork mode vibration of the machine excited by the intermittent contacts of the grinding wheel and the workpiece, the rocking mode vibration of the machine excited by the shock of the work table reversals and the hydraulic oil pressure pulsation produced by the vane pump are the main causes of the minute vibrations. It has been also found that the In-Situ wheel balancing, the wheel cover type dynamic dampers, the steady installation of the machine and the inline type hydraulic accumulators are effective in suppressing these minute vibrations and also the chatter marks produced by these vibrations.

横軸角テーブル形平面研削盤を用いて研削する場合のびびりマークの発生機構

In order to clarify the mechanism of chatter mark generation in surface grinding by using horizontal spindle-reciprocating table type machines, experiments are conducted to measure the relative displacements between a grinding wheel head and a work table during various grinding operations, the dynamic characteristics of the surface grinding machines and the undulations of the finished surfaces. It is found that the dominant causes of the chatter marks are the rocking mode vibration of machines, the vibration having the period of the wheel rotation, the tuningfork mode vibration excited by grinding forces during rough grinding operations and the pulsation of hydraulic oil pressure. It is also found that the chatter marks due to the wheel rotation often change their appearances according to the variation of the speed and stroke of the work table, in spite of constant machine settings.