Showing papers on "Hydraulic machinery published in 2008"

Hydraulic integration and shrub growth form linked across continental aridity gradients.

Abstract: Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.

Hydraulic circuit for synchronized horizontal extension of cylinders

Abstract: A hydraulic system for synchronized movement of multiple cylinders in a horizontal plane includes a bidirectional pump, a shuttle valve cross-connected between pump outlets, flow-control check valves, and control valves which combine to reduce the number of valves in the hydraulic circuit and to reduce total cost of components for the system. The shuttle valve of the hydraulic system provides fluid for resynchronizing extension and retraction of multiple cylinder assemblies without disconnection of lines, provides air removal without disconnection of lines, allows easy addition/refill of hydraulic fluid, and allows excellent control of the extendable cylinder assemblies.

Development of a miniaturised hydraulic actuation system for artificial hands

Abstract: This article will present a powerful miniaturised hydraulic system of compact design that is used for the actuation of artificial hands. This system was developed as an alternative to today's commonly used electromechanical prosthetic actuation systems. System components and hand prototypes reflect many years of experience of our laboratory in rehabilitation medicine, CAD design and prototyping, mechanical engineering, electronic construction, and programming. Prototypes of hydraulically actuated hands were tested by patients under support of orthopaedic companies. The latest hydraulic prostheses have advantages in construction, design, and performance, including adaptivity during grasping and holding of objects. The newly developed miniaturised hydraulic system is competitive with standard mechanical systems of electrically driven prosthetic hands. The modular construction of the system developed allows for customising the mechanical construction of each prosthetic hand and its functional abilities. Contributions of patients concerning grasping activities of prostheses may be taken into account when choosing the hand components already. The components of the new hydraulic actuation system and their technical characteristics will be interesting for specialists in automation technology, actuator development, mechanics, prosthetics, and rehabilitation.

Mobile extraction-assist robot

Abstract: An all-terrain mobile robot comprising a mobile robotic platform, having either wheels or tank-treaded-like legs capable of navigating over rough terrain, wherein the robotic platform utilizes dynamic balancing behavior; a hydraulic powered anthropomorphic torso and articulated arms, wherein the hydraulic system possesses a pressure sensor for enabling the anthropomorphic torso and articulated arms to lift a payload using acute and delicate movements that reduce the chance of causing structural harm to the payload.

Electronic control for a hydraulically driven generator

Abstract: Electronic control for a hydraulic system driving an auxiliary power source is provided, with specific application as a system for controlling the operation of a hydraulically driven AC generator. The system may includes a hydraulic pump, a hydraulic motor drivably connected to the generator, a fluid circuit for circulating fluid from the pump to the motor and back. The fluid circuit may contain a bypass conduit to bypass the motor. The system also includes a proportional servo control valve assembly for controlling the fluid circuits and a control circuit for controlling the proportional control valve assembly. The control system can be capable of controlling the flow of hydraulic fluid to the motor powering the electrical or mechanical system. Sensors for measuring the operating parameters of the system and an operator interface module can influence the operation of the system.

Compact hydraulic accumulator

Abstract: A lightweight, optimally efficient, easily serviced, piston-in-sleeve high pressure accumulator is provided. The accumulator includes one or more cylindrical composite pressure vessel separate end cap manifolds. A piston slidably disposed in a thin impermeable internal sleeve in the accumulator separates two chambers, one adapted for containing a working fluid and the other adapted for containing gas under pressure. Gas is provided in a volume between the impermeable internal sleeve and the composite pressure vessel wall. Additional gas is optionally provided in gas cylinders. Further components are provided for withstanding harmful effects of radial flexing of the composite vessel wall under high pressures, and from stresses present in use in mobile applications such as with a hydraulic power system for a hydraulic hybrid motor vehicle.

Multistage hydraulic gas compression/expansion systems and methods

Abstract: Multistage hydraulic systems and methods for converting the potential energy of a pressurized gas, particularly air, into mechanical work operating in motor, and for producing compressed gas from the mechanical work of the rotating shaft (A1.1 ) when rotating when operating in compressor mode, by performing a successive expansion / compression of the said gas. Each of the systems comprises: a multistage Compression-Expansion Unit (1.3) made of several hydraulic Compression-Expansion Modules (A.3a to A.3d) having different capacity and integrating a gas / liquid separating heat exchanger (A.3.1.5) designed to convert pressure power into a hydraulic power and vice-versa, by performing an essentially isothermal compression / expansion of the gas, a single stage or multistage, direct or indirect, external forced-air Heat Exchanger (A.2) for maintaining the active liquid at ambient temperature; and a multi-circuit, multi-displacement Hydraulic Motor / Pump (A.1) for converting hydraulic power into mechanical power and vice-versa.

Online self-tuning fuzzy proportional–integral–derivative control for hydraulic load simulator

Abstract: Hydraulic systems play an important role in modern industry owing to the fact that hydraulic actuator systems have many advantages over other technologies with electric motors, high durability, and the ability to produce large force at high speeds. Therefore, the hydraulic actuator has a wide range of application fields such as hydraulic pressing machines, moulding technology, etc. where controlled forces or pressures with high accuracy and fast response are the most significant demands. Consequently, many hybrid actuator models have been developed for research on how to control forces or pressures with the best results. The current paper presents a new kind of hydraulic load simulator for conducting performance and stability tests for control forces of hydraulic hybrid systems. In the dynamic loading process, disturbance makes the control performance (such as stability, frequency response, loading sensitivity, etc.) decrease or turn bad. In order to improve the control performance of a loading system and to eliminate or reduce the disturbance, an online self-tuning fuzzy proportional– integral–derivative (PID) controller is designed. Experiments are carried out to evaluate the effectiveness of the proposed control method applied for hydraulic systems with varied external disturbance as in real working conditions

Hydraulic flow through a channel contraction: Multiple steady states

Abstract: We have investigated shallow water flows through a channel with a contraction by experimental and theoretical means. The horizontal channel consists of a sluice gate and an upstream channel of constant width $b_0$ ending in a linear contraction of minimum width $b_c$. Experimentally, we observe upstream steady and moving bores/shocks, and oblique waves in the contraction, as single and multiple steady states, as well as a steady reservoir with a complex hydraulic jump in the contraction occurring in a small section of the $b_c/b_0$ and Froude number parameter plane. One-dimensional hydraulic theory provides a comprehensive leading-order approximation, in which a turbulent frictional parametrization is used to achieve quantitative agreement. An analytical and numerical analysis is given for two-dimensional supercritical shallow water flows. It shows that the one-dimensional hydraulic analysis for inviscid flows away from hydraulic jumps holds surprisingly well, even though the two-dimensional oblique hydraulic jump patterns can show large variations across the contraction channel.

Three-Dimensional Modeling and Geometrical Influence on the Hydraulic Performance of a Control Valve

Abstract: The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier-Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase C υ and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower C υ with higher velocity magnitude within the valve, whereas after smoothing C υ increased and served to delay cavitation inception.

Hydraulic oil distribution controlling device for crane hydraulic system

Abstract: The invention relates to a hydraulic oil distributing and controlling device of a crane hydraulic system, which consists of a first oil inlet and a second oil inlet which are used for communicating with at least two duplex pumps, a first oil outlet and a second oil outlet which are used for supplying oil for a main hoisting motor and an auxiliary hoisting motor as well as a third oil outlet and a fourth oil outlet which are used for supplying oil for a derricking cylinder and a telescopic cylinder; the first oil inlet and the second oil inlet are communicated with the four oil outlets through an oil circuit; control valves are arranged at least on the communicating oil circuits of the first oil inlet and the second oil outlet as well as the third oil outlet and the fourth oil outlet; the control valves are arranged at least on the communicating oil circuits of the second oil inlet and the first oil outlet as well as the second oil outlet and the third oil outlet. The hydraulic oil distributing and controlling device can realize interfluent oil supply of the two duplex pumps so as to improve the operation speed of the corresponding operating condition and operation efficiency, and can use any duplex pump to supply oil respectively to realize a flexible and convenient flow distribution proposal combined by diversified operating conditions.

Hydraulic Circuit Design Rules to Remove the Dependence of the Injected Fuel Amount on Dwell Time in Multijet CR Systems

Abstract: In multijet common rail (CR) systems, the capability to manage multiple injections with full flexibility in the choice of the dwell time (DT) between consecutive solenoid current pulses is one of the most relevant design targets. Pressure oscillations triggered by the nozzle closure after each injection event induce disturbances in the amount of fuel injected during subsequent injections. This causes a remarkable dispersion in the mass of fuel injected when DT is varied. The effects of the hydraulic circuit layout of CR systems were investigated with the objective to provide design rules for reducing the dependence of the injected fuel amount on DT. A multijet CR of the latest solenoid-type generation was experimentally analyzed at different operating conditions on a high performance test bench. The considerable influence that the injector-supplying pipe dimensions can exert on the frequency and amplitude of the injection-induced pressure oscillations was widely investigated and a physical explanation of cause-effect relationships was found by energetics considerations, starting from experimental tests. A parametric study was performed to identify the best geometrical configurations of the injector-supplying pipe so as to minimize pressure oscillations. The analysis was carried out with the aid of a previously developed simple zero-dimensional model, allowing the evaluation of pressure-wave frequencies as functions of main system geometric data. Pipes of innovative aspect ratio and capable of halving the amplitude of injected-volume fluctuations versus DT were proposed. Purposely designed orifices were introduced into the rail-pipe connectors of a commercial automotive injection system, so as to damp pressure oscillations. Their effects on multiple-injection performance were experimentally determined as being sensible. The resulting reduction in the injector fueling capacity was quantified. It increased by lowering the orifice diameter. The application of the orifice to the injector inlet-pipe with innovative aspect ratio led to a hydraulic circuit solution, which coupled active and passive damping of the pressure waves and minimized the disturbances in injected fuel volumes. Finally, the influence of the rail capacity on pressure-wave dynamics was studied and the possibility of severely reducing the rail volume (up to one-fourth) was assessed. This can lead to a system not only with reduced overall sizes but also with a prompter dynamic response during engine transients.

Innovations in pump design-what are future directions?

Abstract: Displacement-controlled actuators, advanced continuously variable transmissions and hydraulic hybrid power trains represent new technologies for mobile hydraulic machines, off road and on road vehicles. These new technologies allow major fuel savings and reduced emissions, but they change the performance requirements of positive displacement pumps and motors. Additionally, the market demand for positive displacement machines will increase. This paper briefly discusses these technology trends and the impact on existing pump and motor designs. The three major challenges are efficiency improvements, noise reduction and advancements in pump and motor control. Examples from the author’s research team documenting the progress in computer modeling of piston pumps and motors will be given.

Micro hydraulic system using slim artificial muscles for a wearable haptic glove

Abstract: Over the past few decades, various haptic gloves have been developed for use in virtual environments. The actuating systems for most existing haptic gloves require lots of external auxiliary equipment. Because of this, the motion of the user is restricted by the length of the electric wires or pneumatic tubes attached to this equipment. A compact actuation system, including related equipment, is thus indispensable for a wearable haptic glove to be truly effective. To resolve the problem of hampered motion and reach, a micro hydraulic actuating system was developed in this research. It was composed of a slim, flexible artificial muscle, a compact hydraulic module for actuating the muscle, and a micro pressure sensor for measuring without flux loss. The characteristics of the muscle were investigated for their control capacity. The step and sinusoidal responses were analyzed to evaluate the performance of the micro hydraulic system. Once these analyses were completed, a lightweight and compact actuation system was built incorporating a wearable haptic glove. By virtue of the developed micro hydraulic system, the wearable haptic glove was able to operate independently of any external equipment, and movement was completely free of any restrictions from wires or tubes.

Analyses of the Long-Term Performance and Tribological Behavior of an Axial Piston Pump Using Diamondlike-Carbon-Coated Piston Shoes and Biodegradable Oil

Abstract: This work reports on the performance enhancement of a real-scale hydraulic system consisting of diamondlike-carbon (DLC)-coated components in combination with biodegradable oil in long-term experiments under conditions simulating those in an actual application. The performance of a hydraulic axial piston pump with DLC-coated piston shoes was evaluated in a newly designed, dedicated hydraulic test system using fully formulated biodegradable, synthetic ester oil. For comparison, an equal but separated hydraulic system with a conventional commercial pump and stainless-steel shoe surfaces was tested. The tests were run at 85% of the maximum pump load and an oil temperature of around 80°C for a period of 2000 h, which corresponds to more than 1 yr of continuous 8 h/day operation in an application. A major abrupt oxidation-induced degradation of the oil did not occur in either system; however, the oil from the system comprising the DLC-coated shoes showed noticeably and consistently better results. The wear of the DLC-coated shoes, especially during the running in, was much lower than that in the conventional steel system. Only minor polishing wear was observed on the DLC shoe's sliding surfaces during the test period, while on the steel shoe's surfaces, many scratches were found and some erosion of the edges was detected.

Windmill utilizing a fluid driven pump

Abstract: A windmill apparatus includes tower, a tower-mounted hydraulic pump driven by windmill blades, and hydraulic lines connected to a ground storage tank and to a number of separate generator units. Each generator unit includes a hydraulic pump and an electrical generator. In operation, upon startup, as the wind propels the propeller-driven pump the hydraulic fluid circulates freely until a pre-set pressure is achieved, upon which a diverter valve diverts all the fluid pressure to the first generator unit. When the first generator unit is powered sufficiently to achieve a stable output voltage, a subsequent one of the remaining generator units is powered up until its output voltage is stabilized, with this process continuing as long as there is a surplus of hydraulic power available to power up additional units to take full advantage of all of the available wind power.

Control of bulk modulus of oil in hydraulic systems

Abstract: In view of requirements for better position accuracy, response time and stability of hydraulic system, it is more important than ever to pay attention to bulk modulus of hydraulic oil. In this paper, the effects of the bulk modulus of hydraulic oil on system performance and the entrapped air on bulk modulus have been analyzed. A method of online vacuum degassing in a sealed system has been used to increase the effective bulk modulus of hydraulic oil, and a device has been developed to measure oil bulk modulus online. The experimental results show that the bulk modulus of hydraulic oil can be controlled in real system effectively by the method mentioned above.

Phase and amplitude control of a linear generator for wave energy conversion

Abstract: Direct drive power take-off for wave energy conversion has been proposed as a viable alternative to hydraulic and pneumatic based systems found in conventional wave energy converters. Allowing for further benefits to be realised, this paper presents a reaction force control scheme to maximise energy extraction, and investigates the modelling and simulation of a direct drive wave energy converter. The control scheme is applied to an experimental test rig with a prototype linear machine with results presented and analysed.

Current State, Problems and the Innovative Solution of Electro-hydraulic Technology of Pump Controlled Cylinder

Abstract: In order to reduce the energy consumption,the noise and the pollution caused by waste oil disposal in hydraulic system,the most direct method is adopting the pump controlled technology without throttle loss.In pump controlled system,through changing the speed or the displacement of the pump,the pressure and volume flow will be completely matched with the need of loads.First the technical characteristics,state of the art and the existing problems about pump controlled cylinder are discussed,then according to the construction features of the double-acting vane pump(motor)and the axlial piston pump,two innovative flow distribution principles are put forward to balance the asymmetrical volume flow produced by unequal areas of the differential cylinder.By using new methods the movement differential cylinder can be closed-loop controlled with only one pump without using any auxiliary elements.So the new system solution has the advantages of high energy efficiency,compact structure and low cost.The two new flow distribution principles and the system integration schemes used to control the differential cylinder with these two new principles are analyzed.The research work will be of great theoretical and practical significance to realizing the green hydraulic control technology.

Hydraulic energy-feeding type vibration damping suspension for vehicle

Abstract: A vehicle hydraulic power feeding type damping suspension, which is installed between the axle and the frame and absorbs the vibration energy between them to drive power consumption part of the vehicle and save the energy. An electromagnetism valve and its manual control variable resistance are installed on the power feeding pipeline to adjust the damping force manually. Hydraulic accumulator is of accumulating spring piston barrel type with decompression and leakage flow passage to prevent each hydraulic part from being damaged by instant ultra-big bumping force. Two sets of power input pulleys (18), (20) are installed in the power consumption parts. (18) is connected with a hydraulic motor pulley (19) and (20) are connected with an engine pulley (17), in which (19) and (20) are equipped with an electromagnetic clutch assembly. Connection lines of the magnetic coils of (19) and (20) are controlled by the vehicle carrying computer or the hydraulic pressure in the accumulator to control the power transfer. It will switch into the engine driving automatically when pressure of the damping fluid can not drive the power consumption part.

Remote control system of industrial field robot

Abstract: Hydraulic excavators are the representative of field robot and has been used in various fields of construction. Since the excavator operates in the hazardous working circumstance, operators of excavator exposed in harmful environment. Therefore, automation and remote control system have been investigated to protect from the hazardous working environment. In this paper, a hydraulic simulation program and a remote control system were developed based on 1.5 ton excavator which is a kind of field robot. The simulator was made by the AMESim, hydraulic modeling environment. And the method to construct the remote control system is proposed. The remote control system is consisted of a manual and automatic mode. Manual mode controls a hydraulic cylinder as open loop control and auto mode controls the end-effecter of excavator using tracking control system. The efficiency of remote control system was evaluated through the field test.

Implement/vehicle steering control system and method

Abstract: A control system controls steering of an implement which is coupled to an agricultural utility vehicle. The control system includes a control unit, a sensor, a hydraulic system on the utility vehicle, an electronically actuatable hydraulic valve, a hydraulic actuator on the implement and a steerable wheel on the implement. A status variable of the utility vehicle or of the implement can be detected with the sensor and transmitted to the control unit. A current operating state of the utility vehicle and/or of the implement is determined by the control unit. The hydraulic valve is connected to the hydraulic system and to the actuator. The hydraulic valve can be actuated as a function of the current operating state of the utility vehicle and/or of the implement in order to block the steering of the wheel with the actuator.

A study on energy saving potential of hydraulic control system using switching type closed loop constant pressure system

Abstract: Up to now, several types of hybrid systems have been developed to deduce energy consumption. Switching type closed loop constant pressure system (SCL-CPS) was proposed as one of feasible hybrid systems. SCL-CPS also uses flywheel, hydraulic accumulator and hydraulic power transmission as a traditional CPS but it has two alternatively high pressure lines. At a same time, one is used as the high pressure line and the other is the low one. Switching between them to overcome large hydraulic shock and noise considered as serious problems in traditional CPS. In this paper, energy saving potential of system is evaluated by considering effect of component efficiencies in system. Recovery efficiency during deceleration the wheel is estimated by simulation. The results indicate that proper determination of recovery time and operating pressure improves significantly energy recovery potential of the system.

Modeling and parameter estimation for hydraulic system of excavator’s arm

Abstract: A retrofitted electro-hydraulic proportional system for hydraulic excavator was introduced firstly. According to the principle and characteristic of load independent flow distribution(LUDV) system, taking boom hydraulic system as an example and ignoring the leakage of hydraulic cylinder and the mass of oil in it, a force equilibrium equation and a continuous equation of hydraulic cylinder were set up. Based on the flow equation of electro-hydraulic proportional valve, the pressure passing through the valve and the difference of pressure were tested and analyzed. The results show that the difference of pressure does not change with load, and it approximates to 2.0 MPa. And then, assume the flow across the valve is directly proportional to spool displacement and is not influenced by load, a simplified model of electro-hydraulic system was put forward. At the same time, by analyzing the structure and load-bearing of boom instrument, and combining moment equivalent equation of manipulator with rotating law, the estimation methods and equations for such parameters as equivalent mass and bearing force of hydraulic cylinder were set up. Finally, the step response of flow of boom cylinder was tested when the electro-hydraulic proportional valve was controlled by the step current. Based on the experiment curve, the flow gain coefficient of valve is identified as 2.825 × 10−4 m3/(s·A) and the model is verified.

Method and device for regulating a pressure in a hydraulic system

Abstract: The present invention relates to a method for regulating a pressure in a hydraulic system for operating at least one actuator in a subsea installation, having a fluid supply line ( 102 ) connected to a source of pressurized fluid ( 101 ) at a remote location delivering fluid at a constant pressure to the subsea installation, comprising first and second control valves ( 103, 105 ) controlled by an electronic control unit ( 107 ), and at least one pressure sensor ( 106 ) and an accumulator ( 104 ) arranged between the first and second control valve ( 103, 105 ), where the pressure in the fluid supply line ( 102 ′) to the actuator is regulated by regulating the pressure in the accumulator ( 104 ) by adding fluid from the source of pressurized fluid ( 101 ) through the first control valve ( 103 ) if the pressure is too low or releasing pressure through the second control valve ( 105 ) to a fluid return line ( 120 ) if the pressure is too high and thereby establishing the desired pressure for operating the actuator. The invention also relates to a device for performing the method.