Showing papers on "Hydraulic machinery published in 2004"

Automatic steering system and method

Abstract: An automatic steering system and method are provided for a vehicle including an hydraulic primary steering system. The automatic steering system includes a guidance module with a GPS receiver and a microprocessor adapted to process and store GPS data defining travel paths, which can be associated with a cultivated field in an agricultural vehicle application. An automatic steering module is connected to the guidance module and to a steering valve control block, which provides pressurized hydraulic fluid in parallel with the vehicle's primary hydrostatic steering system. The automatic steering system utilizes a constant factor, such as steering rate, for predictability and simplicity in the operation of the automatic steering system. A feedback loop from the vehicle hydrostatic steering system uses the vehicle's actual turning rate for comparison with a desired turning rate. The system is adapted for original equipment installation and retrofitting on vehicles, such as farm tractors, with various primary hydrostatic steering system configurations. An automatic steering method includes the steps of: initializing the system; adjusting the steering with an hydraulic valve to provide a constant steering rate; providing feedback corresponding to the vehicle's actual turning rate and combining the feedback with other input signals to provide automatic steering.

Fluid delivery system and related methods of use

Abstract: An apparatus and method for ejecting fluid from a fluid delivery system. The fluid delivery system has a pneumatic assembly that when triggered injects gas into a hydraulic assembly, which in turn ejects fluid through an external interface. An electronic interface displays various measurements, for example, how much fluid has been ejected and if the hydraulic system is closed the pressure of the system. The pneumatic assembly can also be depressurized such that fluid can reenter the hydraulic assembly through the external interface.

Stomatal control and hydraulic conductance, with special reference to tall trees.

Abstract: A better understanding of the mechanistic basis of stomatal control is necessary to understand why modes of stomatal response differ among individual trees, and to improve the theoretical foundation for predictive models and manipulative experiments. Current understanding of the mechanistic basis of stomatal control is reviewed here and discussed in relation to the plant hydraulic system. Analysis focused on: (1) the relative role of hydraulic conductance in the vicinity of the stomatal apparatus versus whole-plant hydraulic conductance; (2) the influence of guard cell inflation characteristics and the mechanical interaction between guard cells and epidermal cells; and (3) the system requirements for moderate versus dramatic reductions in stomatal conductance with increasing evaporation potential. Special consideration was given to the potential effect of changes in hydraulic properties as trees grow taller. Stomatal control of leaf gas exchange is coupled to the entire plant hydraulic system and the basis of this coupling is the interdependence of guard cell water potential and transpiration rate. This hydraulic feedback loop is always present, but its dynamic properties may be altered by growth or cavitation-induced changes in hydraulic conductance, and may vary with genetically related differences in hydraulic conductances. Mechanistic models should include this feedback loop. Plants vary in their ability to control transpiration rate sufficiently to maintain constant leaf water potential. Limited control may be achieved through the hydraulic feedback loop alone, but for tighter control, an additional element linking transpiration rate to guard cell osmotic pressure may be needed.

Hybrid hydraulic drive system with engine integrated hydraulic machine

Abstract: A hybrid hydraulic drive system for a vehicle comprises a prime mover, a transmission connecting the prime mover to drive wheels, a fluid energy storage accumulator, and a reversible hydraulic machine in fluid communication with the energy storage accumulator and drivingly coupled to the prime mover upstream of the transmission. The hybrid hydraulic drive system is arranged such that in a retarding mode the reversible hydraulic machine retards the drive wheels of the vehicle by pumping fluid into the accumulator. In a driving mode the reversible hydraulic machine supplies a supplementary power to the drive wheels of the vehicle using the pressurized fluid from the accumulator to assist propulsion of the vehicle. In a neutral mode the reversible hydraulic machine is disconnected from the prime mover to render the reversible hydraulic machine substantially inoperative to exert any significant driving or retarding influence on the drive wheels.

Sand Erosion in Hydraulic Machinery

Abstract: The topic of this thesis is damage of hydraulic machinery due to sand erosion. This is a very broad topic in which all the aspects of design of hydraulic machinery namely material selection; mechan ...

Wave energy converter

Abstract: An improved wave energy converter for use in offshore and deep-sea locations. The wave energy converter is adapted for secure attachment to the bottom of a body of water (e.g., the ocean floor), preferably beyond the breaker zone. The wave energy converter is selectively adjustable in length. A hydraulic power generation system is used to convert the energy present in the waves into hydraulic power that can be use to generate electricity and for other purposes, such as desalinization. The system may include a hydraulic piston assembly, a floatation device that is connected to the piston assembly, high and low pressure hydraulic reservoirs, and a hydraulically driven power generator. The floatation device moves upward in response to rising waves, and downward under the force of gravity in response to falling waves. The system utilizes this downward gravitational force to discharge fluid from the piston assembly, which in turn, drives the power generator. A control system is used to detect water conditions and to selectively adjust the length of the support structure and the fluid flow characteristics to dynamically optimize power generation based on changing water conditions.

Introduction to Cavitation in Hydraulic Machinery

Abstract: Design, operation and refurbishment of hydraulic turbines, pumps or pump-turbine are strongly related to cavitation flow phenomena, which may occur in either the rotating runner-impeller or the stationary parts of the machine. The paper presents the cavitation phenomena featured by fluid machinery including type of cavity development related to the specific speed of machines in both pump and turbine mode, the influence of the operating conditions, such as load, head and submergence. Therefore, for each type of cavitation illustrated by flow visualization made at the EPFL testing facilities, the influence of cavitation development on machine efficiency, operation and integrity are discussed.

Comparative Analysis of Hydraulic Calculation Methods in Design of Microirrigation Laterals

Abstract: The hydraulic design of a lateral or a submain unit in a microirrigation system has been a problem tackled by many authors. In applications of previous analytical approaches for trickle lateral hyd...

Modeling and control of steering system of heavy vehicles for automated highway systems

Abstract: This work presents modeling, analysis, and controller design of the steering subsystem of heavy vehicles as a subsystem of vehicle lateral control system for the automated highway systems. A physical model of the steering subsystem is derived where the hydraulic power assist unit is modeled as a family of static nonlinear boost curves. Based on open-loop frequency tests and analysis of the physical model structure and its dynamical characteristics, a nominal second order linear model of the steering subsystem is obtained. Then, a linear robust loop-shaping controller is designed to provide a good tracking performance of the closed-loop dynamics of the steering subsystem for varying gain cross over frequencies which is a result of the nonlinear characteristics of the hydraulic power assist. The controller has been successfully incorporated as an inner-loop controller into the nested lateral control architecture for autonomous driving and its efficacy has been demonstrated experimentally.

Velocity based method for controlling a hydraulic system

Abstract: A hydraulic circuit branch includes a hydraulic actuator, such as a cylinder, and an assembly of one or more electrohydraulic proportional valves connected in series between a pressurized fluid supply line and a tank return line. The force acting on the hydraulic actuator is determined by sensing fluid pressures produced by the hydraulic actuator. Pressures in the supply and tank return lines also are sensed. The sensed pressures and a desired velocity for the hydraulic actuator are employed to determine an equivalent flow coefficient, which characterizes fluid flow through the hydraulic circuit branch, either a conduction or restriction coefficient may be derived. The equivalent flow coefficient is used to determine how to activate each electrohydraulic proportional valve to achieve the desired velocity of the hydraulic actuator. The equivalent flow coefficient also is employed to control the pressure levels in the supply and tank return lines.

An Overview about Active Oscillation Damping of Mobile Machine Structure

Abstract: One main current demand for mobile machinery development is the improvement of operator comfort and productivity in order to be competitive on the global market in the future. Actual trends towards cost effective actuator systems in offroad vehicles and thereby the use of electrohydraulic actuators reflects also the task of active oscillation damping of the machine structure. In the past several concepts, which differ in hydraulic system, control and sensor strategy, have been developed. However, the practical use is still minor as in most cases passive oscillation systems, which base upon high pressure hydro-pneumatic accumulators, are widely used although the component costs and frequent check intervals are problematic for this technology. This paper presents an overview of research work done in the area of active oscillation damping technologies for offroad vehicles.

Vehicle braking system

Abstract: A vehicle braking system includes: a hydraulic booster (13) which applies output hydraulic pressure of a hydraulic power source (12) to a boosted hydraulic pressure chamber (25) after regulating the output hydraulic pressure as a control piston (90) operates to balance reaction force generated by hydraulic pressure of the boosted hydraulic pressure chamber (25) with brake operating input; and a brake stroke simulator (14) installed between the brake operating member (11) and the control piston (90) in order for a driver to feel operating strokes of the brake operating member (11). The brake stroke simulator (14) has: an input member (166) axially slidably housed in the control piston (90) of a cylindrical shape and linked to the brake operating member (11); and an elastic body (167,167') interposed between the input member (11) and the control piston (90). The elastic body (167,167') is formed into a tubular shape so as to come into resilient contact with an inner circumference of the control piston (90) by expanding its diameter under the action of axial compressive force generatedby forward movement of the input member (166). Consequently, the brake stroke simulator (14) allows large hysteresis width in relationship between brake operating stroke and operating load.

Brake energy recovery system

Abstract: A brake energy recovery system is used on a vehicle including an auxiliary hydraulic system. The recovery system includes a fluid accumulator and normally open and normally closed switches coupled to be closed and opened, respectively, when the brake pedal is depressed. A hydraulic charging valve is coupled to the outlet of a hydraulic pump and moveable from a neutral to a charging position when the normally open switch is closed. A motor valve is coupled to the inlet of the pump and moveable from a neutral to a driving position when the normally closed switch is in a closed position. The charging valve couples the outlet of the pump to the accumulator in the charging position and the motor valve couples the accumulator to the inlet of the pump in the driving position.

Nonlinear control for a class of hydraulic servo system

Abstract: The dynamics of hydraulic systems are highly nonlinear and the system may be subjected to non-smooth and discontinuous nonlinearities due to directional change of valve opening, friction, etc. Aside from the nonlinear nature of hydraulic dynamics, hydraulic servo systems also have large extent of model uncertainties. To address these challenging issues, a robust state-feedback controller is designed by employing backstepping design technique such that the system output tracks a given signal arbitrarily well, and all signals in the closed-loop system remain bounded. Moreover, a relevant disturbance attenuation inequality is satisfied by the closed-loop signals. Compared with previously proposed robust controllers, this paper’s robust controller based on backstepping recursive design method is easier to design, and is more suitable for implementation.

Performance of a Magnetorheological Hydraulic Power Actuation System

Abstract: The performance of a magnetorheological (MR) hydraulic power system is analytically and experimentally assessed. Four MR valves are implemented as a Wheatstone bridge hydraulic power circuit to drive a hydraulic actuator using a gear pump. The compact hydraulic power actuation system is a Wheatstone bridge network driving a conventional hydraulic actuator. A key advantage of using MR valves in hydraulic actuation systems is that the valves have no moving parts. This reduces complexity and enhances durability compared to conventional mechanical valves. In such a system, an MR fluid is used as the hydraulic fluid. A constant volume pump is used to pressurize the MR fluid. If a change in direction is required, the flow through each of the valves in the Wheatstone bridge can be controlled smoothly via changing the applied magnetic field. A magnetic field analysis is conducted to design a high-efficiency compact MR valve. The behavior and performance of the MR valve is expressed in terms of nondimensional para...

Secrets hidden by two-dimensionality: the economy as a hydraulic machine

Abstract: A long-standing tradition presents economic activity in terms of the flow of fluids. This metaphor lies behind a small but influential practice of hydraulic modelling in economics. Yet turning the metaphor into a three-dimensional hydraulic model of the economic system entails making numerous and detailed commitments about the analogy between hydraulics and the economy. The most famous 3-D model in economics is probably the Phillips machine, the central object of this paper.

Hydrostatic drive apparatus for a road vehicle

Abstract: A road vehicle utilizes hydraulic machines for primary and accessory vehicle drive functions. An internal combustion engine directly drives a first variable capacity hydraulic machine selectively operable as pump or motor, an electric machine electrically coupled to a storage battery is selectively operable as motor or generator and is mechanically coupled to a second hydraulic machine operable as pump or motor, and at least one hydraulic drive motor is coupled to a vehicle drive wheel. A controller regulates the capacity of the first hydraulic machine, and controls the functionality of the first and second hydraulic machines to selectively crank the engine or charge the storage battery. The first hydraulic machine also supplies hydraulic fluid to accessory drive motors including a power steering drive motor, an air compressor drive motor and a supercharger drive motor.

Oil pressure circuit for working machines

Abstract: A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

BMW's dynamic drive: an active stabilizer bar system

Abstract: BMW has developed an active stabilizer bar system, called Dynamic Drive, which significantly reduces roll angle during cornering. For higher lateral accelerations, the roll angle increases gradually at the same rate as in conventional cars to alert the driver to the proximity of the stability limit. In addition, the self-steering properties of the vehicle, including understeering and oversteering, improve handling, agility, steering precision, and safety. The Dynamic Drive system consists of a hydraulic valve block with integrated sensors, a hydraulic pump coupled to the power steering pump, a lateral acceleration sensor, a control unit, several hydraulic lines, and two active stabilizer bars with rotating hydraulic actuators. The main control inputs for the Dynamic Drive system are steering angle and lateral acceleration. A dynamic observer implemented in the electronic control unit calculates the necessary vehicle stabilization torque based on a prediction derived from the steering angle signal and lateral acceleration.

Hydraulic Lifting of Manganese Nodules Through a Riser

Abstract: The calculation of the hydraulic gradient due to the upward flow of a large size particles—water mixture in a vertical pipe is a central problem in the design of systems for deep-sea mining of manganese nodules. Here, the problem is investigated experimentally and with a new calculation method. An experimental apparatus that mimics the deep-sea mining system was built to measure the hydraulic gradient due to the mixture upward flow, the settling velocity of a single manganese nodule, and to explore the relationship between the concentration of fluidized manganese nodules and the solid slip velocity. Experimental relations are found. Also, a formula to compute the total hydraulic gradient of the mixture flow under different flow and solid-loading conditions is developed; the formula accounts for the hydraulic gradients produced by the liquid phase, the solid phase, and the inter-particle collisions. The predictions obtained with the derived equation are compared with experimental data readily available and with the newly acquired laboratory data; these predictions agree very well with the empirical data and demonstrate the value of the model as a design tool.@DOI: 10.1115/1.1641385#

Linear Solution for Hydraulic Analysis of Tapered Microirrigation Laterals

Abstract: A simplified analytical solution that takes into account the effect of the emitter discharge exponent on the hydraulic computations of tapered microirrigation laterals, is presented. The hydraulic analysis is evaluated based on the spatially variable discharge function approach. A simple power equation was used to express distribution of the variable outflow delivered from the each emitter along the lateral. An analytical solution is developed for the case of a linear relationship between the emitter discharge and pressure head, namely, the emitter discharge exponent equals to unique, y = 1.0. In this procedure, the analytical derivations can be applied for uphill, downhill, and zero slope conditions. Results are comparable to those obtained from the literature.

A wave power apparatus having a float and means for locking the float in a position above the ocean surface

Abstract: A wave power apparatus includes at least one rotationally supported arm (122) which carries a float (124) at its free end, so that a translational movement of the float caused by a wave results in rotation of the arm (122). The apparatus comprises power conversion means for converting power transmitted from the wave to the arms into electric power, e.g. a hydraulic system, in which a hydraulic medium is displaced by the movement of the arm, the hydraulic system being coupled to an electric generator. The apparatus comprises a hydraulic lifting system for lifting the float out of the ocean and for locking the float in an upper position above the ocean surface, e.g. during extreme sea wave conditions, such as storm. The lifting system may comprise at least one pump for pumping hydraulic cylinders for lifting the arm out of the ocean.

Operation control method for wind power generator

Abstract: PROBLEM TO BE SOLVED: To provide an operation control method for a wind power generator, in which a generator G is installed on the ground, a flexible control of operation of the wind power generator, and rotation of a windmill 1 can be suppressed without losing wind power energy. SOLUTION: In the operation control method for a wind power generator employing a hydraulic system for transmission of rotational energy, at least one of a hydraulic pump 13, hydraulic motor 15, hydraulic motor 20 is a variable displacement type. A controller 10 is constituted of a revolution number detection means of the windmill 1 and a predetermined electronic control circuit. When receiving a revolution number detection signal of the windmill 1, the controller 10 outputs a control signal based on set operational specifications to perform a variable control of the capacity of a variable displacement hydraulic pump 13 or the hydraulic motor 20. COPYRIGHT: (C)2005,JPO&NCIPI

Closed circuit energy recovery system for a work implement

Abstract: A closed circuit hydraulic system includes a fluid reservoir, a hydraulic cylinder having a cylinder rod, a bidirectional variable displacement hydraulic pump that pumps fluid to either extend or retract the cylinder rod on demand, a flow control valve for relieving pressure between the variable displacement hydraulic pump and the cylinder, and a low pressure check valve between the variable displacement hydraulic pump and the fluid reservoir. Also included is a charge pump for charging the variable displacement hydraulic pump and an accumulator for saving extra energy and fluid from the hydraulic cylinder during the retraction of an extended cylinder rod and using that fluid and energy during the extension of the hydraulic cylinder to reduce a load on the charge pump. The flow control valve opens on demand to allow floating. The low pressure check valve opens when pressure at an inlet of the variable displacement hydraulic pump is low to provide additional fluid and pressure so as to avoid cavitation. A method for using the closed circuit hydraulic system is also provided.

Oil pressure control apparatus for an internal combustion engine

Abstract: An oil pressure control apparatus which includes a source of hydraulic pressure introducing the hydraulic pressure to a hydraulic actuator which is actuated by hydraulic pressure, a fluid passage which is connected between the source of hydraulic pressure and the hydraulic actuator for introducing and discharging hydraulic pressure from the source of hydraulic pressure to the actuator, a control valve which is disposed in the fluid passages for controlling the hydraulic pressure and a filter is disposed in a position that is between the actuator and the control valve. Thereby, the control valve is capable to be operated smoothly.

Werlé–Legendre Separation in a Hydraulic Machine Draft Tube

Abstract: The three-dimensional turbulent flow in a compact hydraulic machine elbow draft tube is numerically investigated for several operating conditions, covering an extended range around the best efficiency point. Comparisons with the experimental data are presented as validation. The interest is focused on the experimentally observed pressure recovery drop occurring near the best efficiency point. The flow is first analyzed locally by means of a topological analysis, then globally with an energetic approach. The study provides evidence for the role played by a Werle-Legendre separation originating in the bend. The separation is due to the contrasting flow angles imposed by the blades, and the angle resulting from the secondary flow

Intrusion within a Simulated Water Distribution System due to Hydraulic Transients. I: Description of Test Rig and Chemical Tracer Method

Abstract: A pilot-scale test rig was designed and constructed to simulate intrusion behavior associated with hydraulic transients initiated by sudden events such as rapid valve closure or uncontrolled change...