Showing papers on "Hydraulic machinery published in 2006"

Hydraulic Power System Analysis

Abstract: Introduction What Is Fluid Power? A Brief History of Fluid Power Fluid Power Applications, Present and Future Advantages of Using Fluid Power Systems A Probable Future Development Properties of Fluids and Their Units Basic Properties of Fluids Compressibility of Liquids Steady State Modeling Rationale for Model Development Source of Equations Conservation of Flow and Energy Friction Losses in Pipes and Fittings Basic Component Equations Worked Examples Discussion Dynamic Modeling Development of Analytical Methods Software Options Dynamic Effects Worked Examples Modeling Hints and Tips Discussion Linear Systems Analysis Introduction Linear Systems The Laplace Transform Inversion, the Heaviside Expansion Method Stability Block Diagrams Spring-Mass-Damper Time Response to Unit Step Force Time Constant Frequency Response and Feedback Introduction Mathematics of Frequency Response Frequency Response Diagrams Using Frequency Response to Find Controller Gain Summary Valves and Their Uses Introduction Directional Control Valves Special Directional Control Valves, Regeneration Flapper Nozzle Valve Flow Control Elements Relief Valves Unloading Valve Pressure Reducing Valve Pressure Sequencing Valve Counterbalance Valve Flow Regulator Valve Pumps and Motors Configuration of Pumps and Motors Pump and Motor Analysis Leakage Form of Characteristic Curves Axial Piston Pumps and Motors Pressure During a Transition Torque Affected by Pressure Transition - Axial Piston Pump Torque and Flow Variation with Angle for Multicylinder Pumps Hydrostatic Transmissions Introduction Performance Envelope Hydrostatic Transmission Physical Features Hydrostatic Transmission Dynamic Analysis Pressure Regulating Valve Purpose of Valve Operation of Valve Mathematical Model of Valve Effect of Damping Valve Model Expansion Basic Valve Model Model Expansion An Assessment of Modeling Flow Division Introduction The Hydraulic Ohm Method Brief Review of DC Electrical Circuit Analysis Fluid Power Circuit Basic Relationships Consolidation of Fluid Power Resistances Application to Unsteady State Flow Conclusions Noise Control Introduction Discussion of Method Mathematical Model Effect of Entrained Air in Fluid Further Discussion of the Mathematical Model Other Methods of Noise Control Damping Methods Index

Hydraulic regeneration system

Abstract: A hydraulic system for a work machine is provided. The hydraulic regeneration system has a tank, a primary source, a first actuator, an accumulator, and a first valve mechanism. The tank is configured to hold a supply of fluid. The primary source is configured to pressurize the fluid and has a suction inlet and a discharge outlet. The first actuator is configured to receive pressurized fluid from the discharge outlet of the primary source. The accumulator is in fluid communication with the tank, the suction inlet of the primary source, and the first actuator. The first valve mechanism is disposed between the suction inlet of the primary source and the accumulator, and is movable between a first position at which fluid returning from the first actuator is directed to the suction inlet of the primary source, and a second position at which fluid returning from the first actuator is directed to only the accumulator.

A Tubular-Generator Drive For Wave Energy Conversion

Abstract: This paper illustrates the operation of a tubular-machine drive as a linear generator for a heave-buoy wave energy conversion. Linear generators, which are adopted in marine power plants, offer the advantage of generating without introducing any conversion crank gear or hydraulic system. The use of a tubular-machine topology allows the electromagnetic thrust density to be improved. This paper briefly summarizes the principles of marine wave buoy interaction and reports the design analysis and control of a permanent-magnet (PM) synchronous tubular linear machine based on a scaled generator prototype and on a rotating simulation test bench

Unified modeling and analysis of a proportional valve

Abstract: Developments in nonlinear control theory have made it possible to design controllers for systems having non-smooth nonlinearities in their dynamics. Hydraulic systems that use inexpensive proportional valves are examples of such systems, where nonlinearities arise due to valve geometry and spool imperfections. Without a proper valve model, however, nonlinear analysis and control of these hydraulic systems is not possible. We have developed nonlinear equations for a generic proportional valve model and have used them to obtain simplified flow rate expressions under generally accepted assumptions. These equations relate a set of geometric spool properties and physical model parameters to the flow rate through the valve ports. The development focuses on obtaining a single set of flow rate equations applicable to critical center, overlapped, and underlapped proportional valves. These unified model equations are useful for simulation and nonlinear controller design. We have also demonstrated that the errors incurred when using the unified valve model are dependent on the damping coefficient alone and are less than 10% in the frequency range within which most valves are used.

Drive train for a compressor and a hydraulic pump

Abstract: The invention relates to a drive train (30) for a compressor (12) and a hydraulic pump (24) of a motor vehicle that, for assisting steering, has a hydraulic power steering (14) and an electric superimposed steering system (36). The compressor (12) and the hydraulic pump (24) are driven by a common output shaft (30) of a motor vehicle driving motor (16). According to the invention, means (10, 20) are provided that reduce the power delivered via the output shaft (30) to the compressor (12) and the hydraulic pump (24) when the demands upon the compressor (12) and upon the power steering system (36) allow this to occur. The invention also relates to a method for driving a compressor and a hydraulic pump of a motor vehicle that, for assisting steering, has a hydraulic power steering as well as an electric superimposed steering system.

Local backup hydraulic actuator for aircraft control systems

Abstract: A backup system is provided that has a local electric motor and pump for some or all of the hydraulic actuators on an aircraft. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

An installation comprising a wave power apparatus and a support structure therefor

Abstract: A wave power apparatus (302) includes a plurality of rotationally supported arms (322) , each of which carries a float (324) at its free end, so that a translational movement of the float caused by a wave results in rotation of the arm. The apparatus comprises power conversion means (128,130) for converting power transmitted from the wave to the arms into electric power, e.g. a hydraulic system. The plurality of apparatus is arranged in a row such that a wave passing the row of arms causes the arms to successively pivot with a mutual phase shift. Thereby, an even power output may be achieved, and the need for frequency converters may be reduced or eliminated. Preferably, each arm is connected to a hydraulic cylinder (328) of the hydraulic system, whereby a plurality of arms feed hydraulic medium into the hydraulic motor or motors through common hydraulic conduits (180).

Digital hydraulic system

Abstract: A digital hydraulic system including a hydraulic source, a housing and a transtatic bridge. The transtatic bridge being substantially contained within the housing; The transtatic bridge being in fluid communication with the hydraulic source. The transtatic bridge communicating a force to or from a shaft or a fluid.

Research on low cavitation in water hydraulic two-stage throttle poppet valve:

Abstract: Cavitation has important effects on the performances and lifespan of water hydraulic control valve, such as degrading efficiency, intense noise, and severe vibration. Two-stage throttle valve is a practicable configuration to mitigate cavitation, which is extensively used in water hydraulic pressure relief valves and throttle valves. The pressure distribution inside a medium chamber located between two throttles of a two-stage throttle valve is investigated through numerical simulations. The effects of the passage area ratio of the two throttles and the inlet and outlet pressures on the pressure inside the medium chamber are examined. The simulation results indicate that (a) the pressure inside the medium chamber is not constant, (b) the locations of maximum and minimum pressures inside the medium chamber are both fixed, which will not vary with the passage area ratio or the inlet and outlet pressures, and (c) the ratio of the pressure drop across the front throttle to the total pressure drop acro...

System and method for providing a launch assist system

Abstract: A system, method and computer readable media are disclosed for providing a hydraulic system for a vehicle The system includes at least one accumulator for storing hydraulic fluid and may also include a flywheel or other storage mechanism for storing energy Energy may be stored either in one of the accumulators or the flywheel A control system controls fluid flow to and from the at least one accumulator and, if included, the flow of energy to and from the flywheel such that: in a steady state mode, a first hydraulic pump/motor is energized by an engine to cause hydraulic fluid to flow and actuate a drive line attached to a second hydraulic pump/motor; in a deceleration mode, the second pump/motor is operates as a pump to transfer energy to the at least one flywheel and/or accumulator; and in an acceleration mode, energy is transferred from the at least one flywheel and/or accumulator to the second hydraulic pump/motor to actuate the driveline and accelerate the vehicle

Hydraulic system with energy recovery

Abstract: A hydraulic system (10) is disclosed. The hydraulic system includes an actuator (22) including a first (30), a second (32), and a third (34) fluid chamber. The hydraulic system also includes a high pressure source (12) of pressurized fluid in selective fluid communication with the first and second fluid chambers. The hydraulic system also includes a low pressure source (14) of pressurized fluid in selective fluid communication with the first and second fluid chambers. The hydraulic system further includes a hydraulic motor (40) in fluid communication with the third fluid chamber.

Motor vehicle hydraulic circuit, has hydraulic piston e.g. camshaft adjuster, where pressurization of hydraulic medium by hydraulic piston from negative portion of alternating external force is utilized by opening of check valves

Abstract: The hydraulic circuit has a hydraulic piston (3) e.g. oscillating motor-like camshaft adjuster (100), with two hydraulic chambers (A, B), where an external force acts on the hydraulic chambers either increasingly or alternatively. The pressurization of the hydraulic medium by the piston from a negative portion of the alternating external force is utilized by opening of check valves (12, 14) for changing the position of the hydraulic piston. The check valves are arranged such that the conduction from one of the chambers is facilitated only in the direction of a pressure side of a switch (10).

Vehicle hydraulic system

Abstract: A hydraulic system incorporated into a vehicle is provided. The system includes a plurality of actuators for providing a desired configuration of a vehicle. A valve system is operatively coupled to the plurality of actuators for controlling a flow of pressurized fluid to the plurality of actuators to energize the actuators to produce, responsive to the desired configuration of the vehicle, a first configuration of a plurality of first configurations of the vehicle corresponding to the desired configuration of the vehicle, or a second configuration of a plurality of second configurations of the vehicle corresponding to the desired configuration of the vehicle.

Motor grader and control system therefore

Abstract: A motor grader has a control system in which the manner of controlling the blade position differs depending upon whether the blade is to be moved vertically or is to be maintained at a generally constant level and cross slope. First and second hydraulic valves control the flow of hydraulic fluid to the first and second hydraulic cylinders which raise and lower respective ends of the blade. An inclinometer provides an inclinometer output indicating the inclination of the blade along its length with respect to horizontal. The control system includes a first hydraulic cylinder position sensor for determining the extension of the first hydraulic cylinder. The control system further includes a control that is responsive to a control input specifying the desired height and cross slope of the blade, to the first hydraulic cylinder position sensor, and to the inclinometer output. The control provides valve control signals to the first and second hydraulic valves. The control provides a first valve control signal to the first hydraulic valve in dependence upon a desired height specified by the control input, and the control provides a second valve control signal to the second hydraulic valve in dependence upon the inclinometer output and upon the cross slope specified by the control input. However, when the blade is to be moved upward or downward with the retraction or extension of the first cylinder, the control provides the second valve control signal to the second hydraulic valve in dependence upon the first hydraulic cylinder position sensor such that the second hydraulic cylinder retracts and extends with the first hydraulic cylinder, maintaining the cross slope angle of the blade as a constant.

Hydraulic fluid storing device for vehicle gear unit, has limiting device and/or housing device retained by retaining device in operating condition against resetting effort of housing and/or limiting devices based on operating condition

Abstract: The device has a storage area (9) connected with a hydraulic system (19) for changing a hydraulic fluid. Volume of the storage area is varied between maximum and minimum depending on an operating condition of a limiting device (8) and a housing device (7). The limiting device and/or the housing device is retained by a retaining device (12) in the operating condition against a resetting effort of the housing device and/or the limiting device based on the operating condition. The operating condition is equivalent to the maximum volume of the storage area. An independent claim is also included for a method for operating a device for storing a hydraulic fluid of a hydraulic system of a transmission device.

The Short-Term Hydrothermal Coordination via Genetic Algorithms

Abstract: This article presents a solution for the short-term hydrothermal generation scheduling problem (HGSP) by using a genetic algorithm. The hydrothermal coordination is solved using an equivalent cost function for the available thermal units, while the unit commitment and the economic dispatch are solved by considering the more capable individuals obtained from the hydrothermal coordination stage. Quadratic cost functions for the thermal units and a second grade equation depending on the volume and the flow for the active power calculation of the hydraulic generation are considered. The appropriateness of the proposition is proved in two power systems: The first system is composed of 4 hydraulic power stations and 10 thermal units, while the second system is composed of 16 hydraulic power stations and 30 thermal ones.

Development of hybrid hydraulic–electric power units for field and service robots

Abstract: Energetic autonomy of a hydraulic-based mobile robot requires a power source capable of both hydraulic and electrical power generation. The hydraulic power is used for locomotion, and the electric ...

Open Circuit Solution for Pump Controlled Actuators

Abstract: Mobile machines of today often contain hydraulic valve controlled actuator loads in an open loop circuit. For the purpose of saving energy, the constant pressure pumps have in the past often been replaced by load sensing pumps and valves. In mobile applications, they have significantly reduced the energy consumption. Stricter environmental demands and rapidly increased fuel cost require an even lower consumption. By analyzing a typical working cycle of a construction machine, the possibility of energy recovery has been identified. The analyse confirms the importance of minimizing the metering losses. In a load-sensing valve solution these losses arise as a result of the unequal drive pressure levels. By adopting a displacement controlled regenerative solution, a significantly higher level of efficiancy can be obtained.

Feedback Linearization Control of a Hydraulic Servo System

Abstract: This paper suggests a hydraulic servo system with a linear controller using feedback linearization. Feedback linearization technique is applied to overcome the non-linearities of the system. The authors pay attention to simpler realization of the controller for the object system and prepare a controller with an additional compensator to recover the response time due to using the reduced order model. The control object consists of a hydraulic servo-valve, a servo-cylinder with an inertia load. The control performances of the control system with the newly suggested controllers and a conventional controller (designed based on a system model linearized around a specific operation point) are compared, and the excellency of the controllers proposed in this study is confirmed

Hardware-in-the-loop simulator for research on fault tolerant control of electrohydraulic flight control systems

Abstract: This paper describes the development of a hardware-in-the-loop (HIL) simulator to support the design and testing of novel fault tolerant control and condition monitoring schemes for fluid power systems emphasizing flight control applications. The simulator uses a distributed architecture to share, in a synchronized manner, the demanding computational load associated with the real-time simulation amongst a number of desktop workstations connected by a dedicated Ethernet network. The simulator runs a high-fidelity model of the F-16 fighter aircraft that is augmented in this paper by the addition of realistic nonlinear models of the hydraulic flight control surface actuators and a model of the nonlinear control surface aerodynamic loads. A specially designed state-of-the-art hydraulic test rig, which has the capacity to experimentally simulate common failure modes of a typical fluid power circuit, is used to emulate a F-16 horizontal tail actuator. The experimental actuator can thus be exercised against the realtime simulation of a F-16 aircraft operating under a variety of normal or faulty conditions. To add further realism to the simulation, a second experimental hydraulic actuator is used to generate the aerodynamic disturbing load. Novel fault tolerant control and diagnosis algorithms can therefore be verified in a realistic application scenario. Pilot-in-the-loop simulations are supported by the inclusion of a graphical visualization of the aircraft motions. The results of a typical HIL experiment, for a normally functioning hydraulic system, are presented to illustrate the operation of the simulator.

Hybrid type construction machine for converting kinetic energy of inertia body into electric energy

Abstract: PROBLEM TO BE SOLVED: To provide a hybrid type construction machine capable of efficiently regenerating kinetic energy of an inertia body, without causing a shock in a hydraulic system and an electric system, when switching driving-regenerative control, when starting or stopping a hydraulic actuator. SOLUTION: Pressure oil from a variable displacement pump 200 is supplied to and discharged from a turning hydraulic motor 204 via lines A and B from a switching control valve 202. A rotary shaft of a power generation electric motor 206 and a rotary shaft of the hydraulic motor are mechanically joined, and are joined to a speed reduction gear mechanism 208, and are also joined to a swivel base 210 being a rotary inertia body. When decelerating and braking the swivel base, an opening-closing valve 204a is put in an opening state by a command signal Sd from a control means 100, and kinetic energy of the swivel base is stored in a capacitor 90 as electric energy generated by driving a motor-driven generator as a generator. The ratio of braking torque between the motor-driven generator and the hydraulic motor in braking, is determined by being associated to differential pressure between pressures PA and PB. COPYRIGHT: (C)2008,JPO&INPIT

Software enabled variable displacement pumps - experimental studies ∗

Abstract: The majority of hydraulic systems are controlled using a metering valve or the use of variable displacement pumps. Metering valve control is compact and has a high control bandwidth, but it is energy inefficient due to throttling losses. Variable displacement pumps are far more efficient as the pump only produces the required flow, but comes with the cost of additional bulk, sluggish response, and added cost. In a previous paper [1], a hydromechanical analog of an electronic switch-mode power supply was proposed to create the functional equivalent of a variable displacement pump. This approach combines a fixed displacement pump with a pulse-width-modulated (PWM) on/off valve, a check valve, and an accumulator. The effective pump displacement can be varied by adjusting the PWM duty ratio. Since on/off valves exhibit low loss when fully open or fully closed, the proposed system is potentially more energy efficient than metering valve control, while achieving this efficiency without many of the shortcomings of traditional variable displacement pumps. The system also allows for a host of programmable features that can be implemented via control of the PWM duty ratio. This paper presents initial experimental validation of the concept as well as an investigation of the system efficiency. The experimental apparatus was built using available off-the-shelf components and uses a linear proportional spindle valve as the PWM valve. Experimental results confirm that the proposed approach can achieve variable control function more efficiently than a valve controlled system, and that by increasing the PWM frequency and adding closed-loop control can decrease system response times and of the output ripple magnitude. Sources of inefficiency and their contributions are also investigated via modeling, simulation and are validated by experiments. These indicate design parameters for improving inefficiency.Copyright © 2006 by ASME

Earth drilling rig having electronically controlled air compressor

Abstract: In an earth drilling rig in which an air compressor and one or more hydraulic pumps are driven by the same engine, the intake throttle of the compressor is controlled by an electronic controller having a proportional integral derivative control. The controller minimizes unloading of the compressor, allowing the engine to operate more efficiently, the hydraulic system to provide more consistent power to drilling functions and the volume and pressure of compressed air to be optimized for the drilling conditions encountered. The electronic controller also operates a blowdown valve at the discharge side of an air receiver, and effects various overrides of the control system, for example when air discharge temperature approaches a critical level, or when an overpressure condition is detected.

Mathematical modeling of changing of dynamic viscosity, as a function of temperature and pressure, of mineral oils for hydraulic systems

Abstract: Viscosity is the most important characteristic of hydraulic fluid. The value and changing of viscosity have essential significance for all events in the hydraulic system. The viscosity of hydraulic fluid is changed with temperature, pressure and rate of shear. However, in analyzing the hydraulic system operation it is usual to use only temperature dependence of viscosity, while influence of pressure and shear rate are neglected. In this paper a mathematical model of changing the dynamic viscosity of mineral hydraulic oil (type HM and HV) with changing of temperature and pressure is given. It is proved that pressure dependence of viscosity cannot be neglected in an analysis of hydraulic system.