scispace - formally typeset
Search or ask a question

Showing papers on "Hydraulic machinery published in 2003"


Journal ArticleDOI
TL;DR: In this article, the scaling between whole-plant hydraulic conductance and leaf area, the relationship between gas exchange at the leaf level and leaf-specific xylem hydraulic conductances, and the short-term physiological regulation of plant hydraulics under conditions of ample soil water, and long-term structural acclimation of xylems to changes in environmental conditions are reviewed.
Abstract: Plant hydraulic conductance, namely the rate of water flow inside plants per unit time and unit pressure difference, varies largely from plant to plant and under different environmental conditions. Herein the main factors affecting: (a) the scaling between whole-plant hydraulic conductance and leaf area; (b) the relationship between gas exchange at the leaf level and leaf-specific xylem hydraulic conductance; (c) the short-term physiological regulation of plant hydraulic conductance under conditions of ample soil water, and (d) the long-term structural acclimation of xylem hydraulic conductance to changes in environmental conditions are reviewed. It is shown that plant hydraulic conductance is a highly plastic character that varies as a result of multiple processes acting at several time scales. Across species ranging from coniferous and broad-leaved trees to shrubs, crop and herbaceous species, and desert subshrubs, hydraulic conductance scaled linearly with leaf area, as expected from first principles. Despite considerable convergence in the scaling of hydraulic properties, significant differences were apparent across life forms that underlie their different abilities to conduct gas exchange at the leaf level. A simple model of carbon allocation between leaves and support tissues explained the observed patterns and correctly predicted the inverse relationships with plant height. Therefore, stature appears as a fundamental factor affecting gas exchange across plant life forms. Both short-term physiological regulation and long-term structural acclimation can change the levels of hydraulic conductance significantly. Based on a meta-analysis of the existing literature, any change in environmental parameters that increases the availability of resources (either above- or below-ground) results in the long-term acclimation of a less efficient (per unit leaf area) hydraulic system.

314 citations


Journal ArticleDOI
TL;DR: A piezoelectrically driven hydraulic amplification microvalve for use in compact high-performance hydraulic pumping systems was designed, fabricated, and experimentally characterized in this article, which enabled the valve to meet simultaneously a set of high frequency (1 kHz), high pressure (/spl ges/300 kPa) requirements not previously satisfied by other hydraulic flow regulation microvalves.
Abstract: A piezoelectrically driven hydraulic amplification microvalve for use in compact high-performance hydraulic pumping systems was designed, fabricated, and experimentally characterized. High-frequency, high-force actuation capabilities were enabled through the incorporation of bulk piezoelectric material elements beneath a micromachined annular tethered-piston structure. Large valve stroke at the microscale was achieved with an hydraulic amplification mechanism that amplified (40/spl times/-50/spl times/) the limited stroke of the piezoelectric material into a significantly larger motion of a micromachined valve membrane with attached valve cap. These design features enabled the valve to meet simultaneously a set of high frequency (/spl ges/1 kHz), high pressure(/spl ges/300 kPa), and large stroke (20-30 /spl mu/m) requirements not previously satisfied by other hydraulic flow regulation microvalves. This paper details the design, modeling, fabrication, assembly, and experimental characterization of this valve device. Fabrication challenges are detailed.

124 citations



Patent
23 Dec 2003
TL;DR: In this article, a wireless sensor and control transmitter subsystem is provided for operating irrigation or other hydraulic systems. The system includes a master module unit and a field module unit that is hardwired to and in communication with field electromechanical control devices such as valves, solenoids and servo motors, and field sensors indicating atmospheric conditions.
Abstract: A passive wireless sensor and control transmitter subsystem is provided for operating irrigation or other hydraulic system. The system includes a master module unit hardwired to and in communication with an existing hydraulic system controller, and a field module unit that is hardwired to and in communication with field electromechanical control devices such as valves, solenoids and servo motors, and field sensors indicating, for example, atmospheric conditions. The master module unit and field module unit communicate with digital wireless communication and can act as a simple wireless bridge providing pass through data connectivity. The master module and field module units are capable of digitizing input signals from the devices to which they are hardwired and transmitting them to the opposite module; they are further capable of recreating the digitized signals received back into the analog form to reproduce the original input signal and communicating it to the device to which it is hardwired. Full duplex communication enables remote sensors to be hardwired to the field modules unit rather than directly to existing control apparatus, as well as being able to transfer valve, pump and relay status back to existing control apparatus. One embodiment enables the subsystem to receive sensor inputs and process them accordingly even though the hydraulic control system may not be capable of utilizing them. Supplemental functionality may be added to an existing hydraulic control system by including the WSCX and its system features of sensor functionality and control.

70 citations


Journal ArticleDOI
TL;DR: Results obtained verified that the wavelet analysis method can improve the capability of diagnosing the health conditions of piston pumps, and more importantly can identify the types of pump defects based on the patterns and the amplitudes of obtained wavelet coefficients.
Abstract: The diagnosis of hydraulic pump health in real-time is important for increasing hydraulic system reliability and performance. Because of high noise levels in the pump pulsation pressure signal, many existing health diagnosis methods, such as limit checking, spectrum analysis, and logic reasoning, cannot effectively perform a reliable on-line health diagnosis for hydraulic pumps. Wavelet analysis, a waveform signal analysis method performed by breaking up an evaluating signal into shifted and scaled versions of a standard wavelet, can identify feature signals in multiple decomposed band windows of the original signal. The methodology for applying this wavelet analysis in real-time health diagnosis for hydraulic pumps was investigated in this study. Results obtained from both simulation analysis and on-line experimental validation verified that the wavelet analysis method can improve the capability of diagnosing the health conditions of piston pumps, and more importantly can identify the types of pump defects based on the patterns and the amplitudes of obtained wavelet coefficients.

61 citations



Proceedings ArticleDOI
04 Jun 2003
TL;DR: Experiments show that the EKF estimator has the ability to promptly and reliably respond to the changes in the pump pressure as little as 10% of the normal operating pressure.
Abstract: This paper presents the application of extended Kalman filter (EKF) to closely estimate the states of hydraulic systems. The EKF, working concurrently with the actual system, accepts the input voltage signal to the servovalve and the measurements of the cylinder chamber pressures, and then rebuilds the system states. The spool displacement of the servovalve, the chamber pressures of the actuator and the velocity of the ram are accurately estimated. By comparing the estimated states and the actual measurements, residual signals are generated and then analyzed to report the occurrence of faults. Experiments show that the EKF estimator has the ability to promptly and reliably respond to the changes in the pump pressure as little as 10% of the normal operating pressure.

60 citations


Patent
15 Oct 2003
TL;DR: In this paper, an excavator that is operable in manual and automatic modes and uses state machines to effect unit operations, rotationally offset swing actuators to rotate boom and cutter head, a fail safe hydraulic system to maintain gripper pressure in the event of a malfunction of the hydraulic system, differing position and pressure control functions in the hydraulic actuators, a kinematic module to effect pitch and roll adjustments, a cutting face profile generator to generate a profile of the excavation face, and an optimization module to realize a high degree of optimization of excavator operation.
Abstract: The present invention is directed to an excavator that is operable in manual and automatic modes and uses state machines to effect unit operations, rotationally offset swing actuators to rotate boom and cutter head, a fail safe hydraulic system to maintain gripper pressure in the event of a malfunction of the hydraulic system, differing position and pressure control functions in the hydraulic actuators, a kinematic module to effect pitch and roll adjustments, a cutting face profile generator to generate a profile of the excavation face, and an optimization module to realize a high degree of optimization of excavator operation.

52 citations


Patent
14 Nov 2003
TL;DR: In this article, a variable displacement hydraulic motor that is fluidly connected to at least the first fluid volume is used to produce electrical power that is stored in a power storage system.
Abstract: Engineers are constantly seeking methods to reduce undesirable emissions, noise, and vibrations created by power systems. In the present invention, a power system includes at least one hydraulic cylinder that defines a first fluid volume and a second fluid volume separated from one another via a moveable plunger. Hydraulic power created within the hydraulic cylinder is converted to mechanical energy by a variable displacement hydraulic motor that is fluidly connected to at least the first fluid volume. A generator is attached to the variable displacement hydraulic motor, and produces electrical power that is stored in a power storage system. The stored power can be supplied to an electric motor that is operable to power a hydraulic pump. The hydraulic pump supplies hydraulic fluid to the hydraulic cylinder. The power system of the present invention is a relatively efficient alternative to a power system including a diesel engine that can be a source of undesirable emissions, noise and vibrations.

52 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigate the control of excavation processes by applying load-independent hydraulic valves, which allows avoiding closed loop control system with sensors and transducers mounted on the excavator attachment.

51 citations


Book
01 Jan 2003
TL;DR: In this article, the basic thermodynamics and fluid mechanics of hydraulic machinery are discussed, as well as the cavitation in hydraulic machinery, including pumps, compressors, fans, axial flow and radial flow.
Abstract: Dimensional analysis - basic thermodynamics and fluid mechanics hydraulic pumps hydraulic turbines centrifugal compressors and fans axial flow compressors and fans steam turbines axial flow and radial flow gas turbine cavitation in hydraulic machinery.

01 Jan 2003
TL;DR: In this paper, three different versions of latching-controlled, axisymmetric, wave-power buoys, intended to operate in the heave mode, and to force-react against anchors on the sea bed, were investigated.
Abstract: Results are presented from previous investigations of three different versions of latching-cont rolled, axisymmetric, wave-power buoys, intended to operate in the heave mode, and to force-react against anchors on the sea bed. One of them had hydraulic machinery for control and power take-off, while the two others had a latching mechanism for control and pneumatic power take-off. One of the three versions utilised an oscillating water column contained in a heaving structure. Hulls of various shapes were examined: cylindrical with hemispherical base, conical with the widest part up, and, finally, spherical. Model tests were performed that indicate reasonable agreement with theory. Technical assessments of full-scale power buoys indicated the necessity for further development work on some of the components. Economic assessments showed that these power buoys, in their present state of development, could not yet compete commercially with hydroelectric power plants in Norway.

Journal ArticleDOI
TL;DR: In this article, an objective methodology is proposed for evaluating the hydraulic performance for possible rehabilitation of sewer systems, which involves assigning a hydraulic performance index to each pipe section and taking into account the vulnerability and the retention capacity of each pipe sections.
Abstract: An objective methodology is proposed for evaluating the hydraulic performance for possible rehabilitation of sewer systems. It involves assigning a hydraulic performance index to each pipe section. This hydraulic index reflects both the local surcharge in a pipe and the surcharge induced at upstream sections of the same branch in a sewer network. The hydraulic index also takes into account the vulnerability and the retention capacity of each pipe section. This index may be used directly to establish the rehabilitation priority of different sections to maximize hydraulic performance for the entire network. This methodology was successfully applied to the sewer system of the city of Laval in Canada. The results show how pipe dimensions and locations have the effect of surcharging or relieving a pipe network and how the hydraulic performance index adequately rates the contributions of sewer network components.

Patent
16 Dec 2003
TL;DR: In this article, a hydraulic regenerative braking system for a vehicle is described, which includes two hydraulic machines, each of which is disposed proximate to a corresponding vehicle wheel, and a transformer is in communication with each of the hydraulic machines and with a pair of accumulators.
Abstract: A hydraulic regenerative braking system for a vehicle is provided. The system includes two hydraulic machines, each of which is disposed proximate a corresponding vehicle wheel. A transformer is in communication with each of the hydraulic machines, and with a pair of accumulators. Each of the hydraulic machines is operable as a pump, pumping fluid to at least one of the accumulators when the vehicle is braking. Each of the hydraulic machines is also operable as a motor, receiving pressurized fluid and transferring torque to the vehicle wheels. The transformer is operable to vary the pressure of the fluid received by the hydraulic machines.

Proceedings ArticleDOI
08 Mar 2003
TL;DR: In this article, a prototype in-line, intelligent pump monitor for critical hydraulic pumps and motors is presented, which includes performance modeling, signal processing and feature extraction, feature level fusion, automated classification, and knowledge fusion for estimating degradation through the collection of inline pump sensor data and onboard processing.
Abstract: Abshact Aircraft hydraulic systems are used to actuate flight control surfaces (flaps, spoilers, ailerons, elevators, and rudder), thrust vectoring and reversing mechanisms, landing gear, cargo doors, and in some cases, weapon systems. Within these flight and mission critical hydraulic systems, the hydraulic pump is widely recognized to be the most critical component. The current paper discusses methods to fulfill the need for on-line pump diagnostics through the development of a prototype in-line, intelligent pump monitor for critical hydraulic pumps and motors. The approach includes performance modeling, signal processing and feature extraction, feature level fusion, automated classification, and knowledge fusion for estimating degradation through the collection of inline pump sensor data and onboard processing. The methods employed and an initial hardware and software realization are reviewed. The effects and tracking of pump wear and fatigue damage as witnessed from a series of endurance tests conducted at the Air Force Research Laboratory (AFRL) will be shown from the successful results of stimulating the in-line pump with digitized test data.

Patent
23 Sep 2003
TL;DR: In this paper, the authors present a control system for operating a hydraulic system, which includes a user input device (47) which generates an input signal indicating desired movement of a hydraulic actuator (16), a mapping routine (50) converts the input signal into a velocity command indicating a desired actuator velocity.
Abstract: A control system for operating a hydraulic system (10) includes a user input device (47) which generates an input signal indicating desired movement of a hydraulic actuator (16). A mapping routine (50) converts the input signal into a velocity command indicating a desired actuator velocity. A valve opening routine (56) transforms the velocity command into a flow coefficient which characterizes fluid flow through the valve assembly (25) and from the flow coefficient produces a set of control signals designating levels of electric current to apply to valves (21-24) within the valve assembly. A pressure controller (64) regulates pressure in the supply line (14) in response to the velocity command. When the hydraulic system (10) has a plurality of functions (11,20), the control system adjusts each velocity command to equitably apportion fluid to each function, when the aggregate flow being demanded by the functions exceeds the total flow available from a source.

Patent
10 Jul 2003
TL;DR: In this article, a valve mechanism is installed inside the accumulator to restrict the supply of hydraulic fluid from the hydraulic fluid chamber to the hydraulic actuator when the pressure in the fluid chamber is less than a set pressure.
Abstract: A hydraulic circuit includes an accumulator having an inflow passage which introduces a hydraulic fluid which is discharged from a hydraulic pump into a hydraulic fluid chamber and a discharge passage which discharges the hydraulic fluid from the hydraulic fluid chamber to a hydraulic actuator. The hydraulic circuit includes a valve mechanism which restricts the supply of hydraulic fluid from the hydraulic fluid chamber to the hydraulic actuator when the pressure in the hydraulic fluid chamber is less than a set pressure and which releases the restriction of the supply of hydraulic fluid to the hydraulic actuator when the pressure in the hydraulic fluid chamber is at least the set pressure. The valve mechanism may be installed inside the accumulator.

Journal ArticleDOI
TL;DR: In this paper, a non-hydrostatic model for solving fluid flows for hydraulic applications is proposed, which employs unstructured grid technology with arbitrarily shaped cells, offering the potential to unify many grid topologies into a single formulation.
Abstract: A three-dimensional computational method, without the use of hydrostatic assumption, is developed to solve fluid flows for hydraulic applications. Numerical algorithms and verification of the nonhydrostatic model are described in our companion paper. The model employs unstructured grid technology with arbitrarily shaped cells, offering the potential to unify many grid topologies into a single formulation. Herein, the model is applied to two practical steady hydraulic flows to provide further validation of the model and demonstrate its use in practical flows. The flows in a hydroturbine draft tube and in the forebay of Rocky Reach Dam for the fish passage facility design are simulated. Comparisons with experimental data in the former and physical and field measurements in the latter establish the scope of the model.

Journal ArticleDOI
TL;DR: In this article, a two-fluid solver for hydraulic flow problems was developed. The authors used Cartesian cut cell technique to provide a boundary fitted mesh without the need for traditional mesh generation techniques.
Abstract: A two-fluid solver which can be applied to a variety of hydraulic flow problems has been developed. The scheme is based on the solution of the incompressible Euler equations for a variable density fluid system using the artificial compressibility method. The computational domain encompasses both water and air regions and the interface between the two fluids is treated as a contact discontinuity in the density field which is captured automatically as part of the solution using a high resolution Godunov-type scheme. A time-accurate solution has been achieved by using an implicit dual-time iteration technique. The complex geometry of the solid boundary arising in the real flow problems is represented using a novel Cartesian cut cell technique, which provides a boundary fitted mesh without the need for traditional mesh generation techniques. A number of test cases including the classical low amplitude sloshing tank and dam-break problems, as well as a collapsing water column hitting a downstream obstacle have been calculated using the present approach and the results compare very well with other theoretical and experimental results. Finally, a test case involving regular waves interacting with a sloping beach is also calculated to demonstrate the applicability of the method to real hydraulic problems.


Patent
11 Jun 2003
TL;DR: In this paper, an electronic controlled coupling with an electric motor, an electric control unit, and a supply passage for supplying hydraulic pressure is presented. But the coupling case accommodates the wet-type multiple disc clutches and contains oil.
Abstract: An electronic controlled coupling according to the present invention includes a wet-type multiple disc clutch, a coupling case, a hydraulic chamber, and an oil pump. The electronic controlled coupling also includes an electric motor, an electric control unit, and a supply passage for supplying hydraulic pressure. The coupling case accommodates the wet-type multiple disc clutch and contains oil. The oil pump driven by the electric motor is connected to the coupling case. The outlet of the oil pump is connected to the hydraulic chamber of the wet-type multiple disc clutch with the supply passage therebetween. The electric control unit controls the speed of rotation of the electric motor through a motor driver so that the pump discharge pressure is equal to an operating pressure required for the wet-type multiple disc clutch. Even if the electronic controlled coupling does not provide with own hydraulic power source, the electronic controlled coupling performs a complete coupling mechanism increasing the durability as a coupling and a compact and simple structure enhancing the flexibility in designing.

Patent
20 Oct 2003
TL;DR: In this paper, the problem of providing a device which can be used in a fuel system having a variable supply pressure and has a small structure and a long lifetime is addressed. But, it is difficult to find a suitable device that can be installed in the fuel system.
Abstract: PROBLEM TO BE SOLVED: To provide a device which can be used in a fuel system having a variable supply pressure and has a small structure and a long lifetime. SOLUTION: There are provided with a housing 38 and 40, and a working chamber 66. The working chamber 66 is communicated with a hydraulic system. At least one gas capacity 58, which is tightly closed with a diaphragm 54, is formed in the working chamber 66. COPYRIGHT: (C)2004,JPO

Patent
Hongliu Du1
28 Jul 2003
TL;DR: In this article, a method and apparatus for determining the operating health of a hydraulic system is presented, which may include the steps of determining a plurality of operating parameters of the hydraulic system during operation of the system, determining an estimated working condition value of the hydraulics system, modifying the estimated working conditions as a function of the operating parameters, and determining the operational health of the Hydraulics System as a result of the working condition values.
Abstract: A method and apparatus for determining the operating health of a hydraulic system are provided. The method may include the steps of determining a plurality of operating parameters of the hydraulic system during operation of the hydraulic system, determining an estimated working condition value of the hydraulic system, modifying the estimated working condition value as a function of the operating parameters, and determining the operating health of the hydraulic system as a function of the working condition value. In one method, the working condition value may be indicative of an effective bulk modulus value of an operating fluid within at least part of the hydraulic system.

Patent
13 Feb 2003
TL;DR: In this paper, a method for regulating a predetermined modifiable brake pressure in the wheel brakes of a brake system, according to which input variables that determine the brake pressure are evaluated and control variables of hydraulic valves are defined in a control and/or data processing system.
Abstract: The invention relates to a method for regulating a predetermined modifiable brake pressure in the wheel brakes of a brake system, according to which input variables that determine the brake pressure in the individual wheel brakes are evaluated and control variables of hydraulic valves are defined in a control and/or data processing system. The aim of the invention is to obviate the need for additional pressure sensors, which register the pressure of the wheel brakes. To achieve this a characteristic curve is stored in the control or data processing system, said curve correlating the valve characteristics of the hydraulic valve with a pressure differential of the hydraulic valve and the control variable of the hydraulic valve, in particular the valve flow, is defined according to said characteristic curve.


Patent
10 Apr 2003
TL;DR: In this paper, a valve arrangement is provided for switching between individual pump flows and/or for interconnecting the individual pumps flows, by which a volume flow is supplied to a consumer.
Abstract: The invention relates to a hydraulic system comprising a multi-flow, especially dual-flow, hydraulic pressure supply unit, such as a pump, by which means a volume flow is supplied to a consumer. The invention is characterised in that a valve arrangement is provided for switching between the individual pump flows and/or for interconnecting the individual pump flows.

Patent
28 Oct 2003
TL;DR: The integrated and self contained diesel hydraulic thruster system integral has a dynamic positioning control system for dynamic positioning of any waterborne vessel having a hull with at least two sides and a deck connecting the sides as mentioned in this paper.
Abstract: The integrated and self contained diesel hydraulic thruster system integral has a dynamic positioning control system for dynamic positioning of any waterborne vessel having a hull with at least two sides and a deck connecting the sides, at least two removably mounted azimuthing thrusters, at least two self-contained diesel hydraulic power units removably secured to the deck, one for each thruster, at least one dynamic positioning computer connected to each of the self contained diesel hydraulic power units, at least one motion reference sensor connected to the dynamic positioning computer to correct reference position signals for motion of the vessel, at least one heading sensor, and at least one sensor that is either a position reference sensor connected to the dynamic positioning computer, an environmental sensor connected to the dynamic positioning computer, or a combination thereof.

Patent
17 Jan 2003
TL;DR: In this paper, a hydrostatic hi-rail system for use with a railway maintenance vehicle to allow travel along railway rails by raising the vehicle off of roadengaging tires onto rail-engaging flanged rail wheels is presented.
Abstract: A hydrostatic hi-rail system for use with a railway maintenance vehicle to allow travel along railway rails by raising the vehicle off of road-engaging tires onto rail-engaging flanged rail wheels. The operator controlled system includes front and rear lift assemblies, which are mounted to the front and rear of the vehicle. The assemblies include hydraulic motors, couplers and fail-safe brakes. The system is powered by the vehicle's power source such as an engine and a hydraulic power source such as the vehicle's hydraulic pump.

Patent
17 Feb 2003
TL;DR: In this paper, a hydraulic power assisted steering system comprising a steering gear and a hydraulic actuator for supporting a steering wheel actuation carried out by the driver of a vehicle, especially a motor vehicle is described.
Abstract: The invention relates to a hydraulic power assisted steering system comprising a steering gear (6) and a hydraulic actuator (20) for supporting a steering-wheel actuation carried out by the driver of a vehicle, especially a motor vehicle. Means (22) for actively applying additional steering-wheel torque are associated with said steering system, said means (22) comprising at least one additional torque actuator (23) and a detection means (25) for the steering-wheel torque, which are arranged as a module on a steering wheel shaft (5) connecting the steering wheel (1) to the steering gear (6).

Patent
17 Nov 2003
TL;DR: A hydraulic system includes an actuator, a hydraulic coupler that includes substantially incompressible hydraulic liquid, and a container as mentioned in this paper, which when moved forces the target fluid out of the container.
Abstract: Systems and methods for hydraulically and volumetrically dispensing target fluid. A hydraulic system includes an actuator, a hydraulic coupler that includes substantially incompressible hydraulic liquid, and a container. The container may include a slidable or movable plunger or wall that when moved forces the target fluid out of the container. The actuator includes a motor or driver, such as a step motor, linear actuator, servomotor, pneumatic motor, or other similar device, to drive a plunger or piston of the hydraulic coupler. The coupler includes a conduit, column, shaft or other leak proof assembly that acts as a conduit for the substantially incompressible hydraulic liquid and includes a plunger or piston that is selectively pushed by the incompressible hydraulic liquid, thereby driving a head of the plunger or piston to press against the wall or plunger of the container or syringe that contains the target fluid or against the target fluid, causing the target fluid to be dispensed therefrom. Furthermore, the system may include a controller that is configured to control the target fluid dispensed and to receive input from a user.