scholarly journals Dynamic and efficiency characteristics of an inlet metering valve controlled fixed displacement pump

2016 ◽  
Author(s):  
◽  
Julie Kay Wisch
Keyword(s):  
Significant Loss ◽  
Hydraulic Systems ◽  
Hydraulic Pump ◽  
Pump Design ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Spool Valve ◽  
Complex Parts ◽  
Pressure Controlled ◽  
Variable Displacement Pumps

This project developed the inlet metering system. An inlet metering system represents a new option in hydraulic pump design. Traditional pressure controlled hydraulic pumps rely on either swashplate displacement (for variable displacement pumps) or bleed off valves (for fixed displacement pumps). Variable displacement pumps require mechanically complex parts which are expensive to machine and prone to break down. Bleed off valves represent a significant loss in system efficiency. In contrast, the inlet metering system is able to make use of a fixed displacement pump (which is relatively inexpensive and mechanically robust) and a two-way spool valve. This dissertation goes through the process of designing the valve and pump dimensions, presents a theoretical dynamic analysis, studies the control law associated with this pump, and examines the energy requirements associated with inlet metering system operation. A prototype of the design was constructed and experimental data was used to validate the efficiency analysis. The major finding associated with this work was that the inlet metering system can be designed to display a first order pressure response. This means that when the inlet metering system is operated, the actual pressure in the system will never exceed the desired pressure. In contrast, traditional hydraulic systems will display up to 60% pressure overshoot, meaning the systems must be designed to handle pressures significantly greater than operating pressures. Additionally it was found that the inlet metering system is more efficient than using a bleed off valve, but less efficient than using a variable displacement pump.

Software Enabled Variable Displacement Pumps

2005 ◽  
Author(s):  
Perry Y. Li ◽  
Cassie Y. Li ◽  
Thomas R. Chase
Keyword(s):  
Feedback Control ◽  
Response Time ◽  
Low Cost ◽  
Hydraulic Systems ◽  
Ongoing Research ◽  
Throttle Valve ◽  
System Pressure ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Variable Displacement Pumps

Direct pump control of hydraulic systems is more energy efficient than throttle valve based methods to control hydraulic systems. This requires variable displacement pumps that are responsive and capable of electronic control. Such Electronic Displacement Controlled (EDC) pumps tend to be significantly larger, heavier and more expensive than fixed displacement counterparts. In addition, achievable control bandwidths are typically lower than throttle valve based control approaches. We have recently begun a project to achieve the functionality of a variable displacement pump by combining a fixed displacement pump, a pulse width modulated (PWM) on/off valve under closed loop feedback control, and an accumulator. The proposed topology is the hydro-mechanical analog of the DC-DC boost converter in power electronics. Since on/off valves have little loss in either the on or the off state, this approach is potentially more efficient than throttle valve based control approaches. It has the small size/weight and low cost advantages of a fixed displacement pump. Faster response can be expected by eliminating the intervening inertias of the swash plate control system. The pump’s functionalities can also be easily programmed by controlling the PWM on/off valve in different manners. This paper presents some preliminary results from this ongoing research program. While the PWM valve based approach provides desirable features, it also introduces undesirable ripples to the system pressure and flow rate. It is shown that increasing the accumulator pre-charge pressure and the accumulator volume can decrease ripple size at the expense of response time. This apparent trade-off can be alleviated by feedback control to achieve fast response time while keeping ripple small. Feedback control using PWM control must be implemented with care since the conventional “state-space” model may not be valid when the PWM frequency is low. On the other hand, increasing PWM frequency reduces ripple size and enables the system to achieve high control bandwidths.

scholarly journals A Single Stage Spool Valve for the Pressure Compensator of a Variable Displacement Pump – Design, Dynamic Simulation and Comparative Study With A Real Pump

2021 ◽  
Author(s):  
Nitesh Mondal ◽  
Rana Saha ◽  
Dipankar Sanyal
Keyword(s):  
Comparative Study ◽  
Design Sensitivity ◽  
Single Stage ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Pump Design ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Spool Valve ◽  
Axial Piston

Abstract The study is focused on the design of a simplified spool valve to be incorporated in the pressure compensator of a variable displacement axial piston pump in order to perform a comparative study with a commercial pump having a two stage spool valve in its compensator. The design involves evaluation of the spool size and selection of spring from static equilibrium condition to satisfy cut-in and cut-off pressure. Following the development of dynamic model of the system, a design sensitivity analysis of the spool valve has been carried out through simulation to identify the critical sizes of the parameters, which affect the pump performance. By systematic design, it is possible to have a single stage spool valve controlled pressure compensator that can produce performance of the variable displacement axial piston pump at par with the similar commercially available pump.

High-Speed 4-Way Rotary On/Off Valve for Virtually Variable Displacement Pump/Motor Applications

2011 ◽  
Author(s):  
Haink C. Tu ◽  
Michael B. Rannow ◽  
Meng Wang ◽  
Perry Y. Li ◽  
Thomas R. Chase ◽  
...  
Keyword(s):  
High Speed ◽  
Hydraulic Systems ◽  
Rotary Valve ◽  
Hydraulic Pump ◽  
Hydraulic Hybrid ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Pump Valve ◽  
Cycle Efficiency ◽  
Physical Displacement

The application of switched mode control to hydraulic systems has the potential of decreasing component complexity, size, and cost. This is accomplished by enabling variable pump or motor functionality using a single on/off valve paired with a compact, inexpensive fixed displacement machine. A 4-way tandem rotary on/off valve is presented in this paper that extends a novel rotary valve concept (experimentally validated for pump applications) to hydraulic pump/motors. The pump/valve system is referred to as a Virtually Variable Displacement Pump/Motor (VVDPM) since the effective displacement of the system is variable and not the physical displacement of the pump itself. This paper investigates the design and efficiency of the proposed rotary valve when utilizing the VVDPM on a light weight power-split hydraulic hybrid passenger vehicle that is driven over a standard federal drive cycle. Simulated VVDPM efficiency maps are presented for motoring and pumping and the cycle efficiency of an optimized VVDPM is compared to that of a typical bent axis unit. Vehicle fuel economy is also explored through simulation.

Simulation and Field Experiments With an Agricultural Tractor of a Robust Control for a Complete Fluid Power Circuit Using a New Electro-Hydraulic Pump: Part II—Control

2010 ◽  
Author(s):  
Pandeli Borodani ◽  
Davide Colombo ◽  
Marco Forestello ◽  
Patrizio Turco ◽  
Riccardo Morselli
Keyword(s):  
Field Experiments ◽  
Optimization Techniques ◽  
Point Of View ◽  
Hydraulic Pump ◽  
Power Circuit ◽  
Control Approach ◽  
New Device ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Energetic Point

The plant under control is the hydraulic circuit arranged by CNH in a prototype agriculture tractor of medium segment, where instead of the conventional main hydraulic pump, a new device electronically piloted, is installed. The main purpose is basically to obtain some advantages according to the energetic point of view, by means of an appropriate control structure, managing the electronic variable displacement pump. The frontier of the new systems requires the employment of the advanced control techniques, in order to assure the levels of precision, reliability, robustness demanded from systems. The control design methodology employed in the present case is based on robust H∞ optimization techniques, where robust stability properties are guaranteed in presence of unaccountable dynamics and other destabilizing factors. The effectiveness of the proposed control approach is tested on the demonstrative tractor realized from the CNH Agriculture at Modena plants, in all real conditions.

Design and Testing of an Adjustable Linkage for a Variable Displacement Pump

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Shawn R. Wilhelm ◽  
James D. Van de Ven
Keyword(s):  
High Efficiency ◽  
Operating Conditions ◽  
The Novel ◽  
Hydraulic Pump ◽  
Low Friction ◽  
Transmission Angle ◽  
Displacement Pump ◽  
Order Of Magnitude ◽  
Variable Displacement ◽  
Design And Testing

A variable displacement hydraulic pump/motor with high efficiency at all operating conditions, including low displacement, is beneficial to multiple applications. Two major energy loss terms in conventional pumps are the friction and lubrication leakage in the kinematic joints. This paper presents the synthesis, analysis, and experimental validation of a variable displacement sixbar crank-rocker-slider mechanism that uses low friction pin joints instead of planar joints as seen in conventional variable pump/motor architectures. The novel linkage reaches true zero displacement with a constant top dead center position, further minimizing compressibility energy losses. The synthesis technique develops the range of motion for the base fourbar crank-rocker and creates a method of synthesizing the output slider dyad. It is shown that the mechanism can be optimized for minimum footprint and maximum stroke with a minimum base fourbar transmission angle of 30 deg and a resultant slider transmission angle of 52 deg. The synthesized linkage has a dimensionless stroke of 2.1 crank lengths with a variable timing ratio and velocity and acceleration profiles in the same order of magnitude as a comparable crank-slider mechanism. The kinematic and kinetic results from an experimental prototype linkage agree well with the model predictions.

Software Enabled Variable Displacement Pumps: Experimental Studies

2006 ◽  
Author(s):  
Michael B. Rannow ◽  
Haink C. Tu ◽  
Perry Y. Li ◽  
Thomas R. Chase
Keyword(s):  
Experimental Studies ◽  
Check Valve ◽  
Design Parameters ◽  
Duty Ratio ◽  
System Response ◽  
Experimental Apparatus ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Valve Control ◽  
Variable Displacement Pumps

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.

Design and Testing of Novel Hydraulic Pump/Motors to Improve the Efficiency of Agricultural Equipment

2017 ◽  
Vol 60 (6) ◽  
pp. 1809-1817
Author(s):  
Farid Breidi ◽  
Jordan Garrity ◽  
John Lumkes
Keyword(s):  
Agricultural Sector ◽  
Energy Savings ◽  
Fluid Power ◽  
System Level ◽  
Hydraulic Systems ◽  
Hydraulic Pump ◽  
Agricultural Equipment ◽  
Load Height ◽  
Variable Displacement ◽  
The Impact

Abstract. Hydraulic systems are prevalent in agricultural machinery and equipment and can be found transmitting power for vehicle drive wheels, powering attachments, and controlling motion (booms, steering, load height, etc.). Agricultural applications of fluid power have advanced in terms of capability and efficiency, but opportunities remain for significant improvements in efficiency, noise reduction, and reliability. The average system-level hydraulic efficiency of current mobile agricultural machines is only 21.1%. Because nearly all hydraulic systems use pumps to convert engine power to fluid power, improving the efficiency of the pumps (and motors when used as actuators) significantly impacts the system efficiency. This work examines the impact of using more efficient digital pump/motors to improve the overall efficiency of agricultural equipment, such as tractors, harvesters, planters, fertilizers, sprayers, and attachments. Maintaining higher pump/motor efficiency throughout the operating range is the central principal for the energy savings. Currently used variable-displacement pumps have low efficiencies at low displacement levels due to constant losses that do not scale with the power produced. Digital pump/motors minimize these inefficiencies because energy losses scale more closely with the power produced. Experimental results indicate an average efficiency of 85% when operating at 20% to 100% displacement. This efficiency is 15% to 20% higher on average than with current variable-displacement axial piston pumps. This study demonstrates that achieving this improvement in the efficiency of the pump/motors used in tractors and harvesters alone would conservatively save $61.7 million worth of energy annually for end users in the U.S. agricultural sector. Keywords: Agricultural equipment, Digital hydraulics, Efficiency improvement, Hydraulic pump/motor.

The Swashplate Angle Control of a Variable Displacement Pump with an Electro-Hydraulic Proportional Valve

2008 ◽  
Vol 594 ◽  
pp. 389-400 ◽  
Author(s):  
Ming Hwei Chu ◽  
Yuan Kang ◽  
Yi Wei Chen ◽  
Yeon Pun Chang
Keyword(s):  
Angular Displacement ◽  
Mathematic Model ◽  
Hydraulic Systems ◽  
Displacement Pump ◽  
Type Variable ◽  
Hydraulic Servo ◽  
Simulation And Experiment ◽  
Variable Displacement ◽  
Servo Controller ◽  
The Stability

In this paper, the mathematic model of the swashplate type variable displacement axial piston pump (VDAPP) is established. The VDAPP applied to an electro-hydraulic servo control system usually induces unstable performance, so that a servo controller is designed and analyzed to control the swashplate angular displacement and improve the stability and transient response of pump performance. The flow and pressure variations of pump with the proposed controller are investigated and analyzed by mathematic simulations and experiments. The simulation and experiment results show that the proposed controller can improve the stability of swashplate angular displacement, and easily applied to the energy saving hydraulic systems.

Pressure Compensator Design for a Swash Plate Axial Piston Pump

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
N. P. Mandal ◽  
R. Saha ◽  
S. Mookherjee ◽  
D. Sanyal
Keyword(s):  
Critical Role ◽  
Design Procedure ◽  
Swash Plate ◽  
Simulation Based Design ◽  
Displacement Pump ◽  
Popular Pressure ◽  
Variable Displacement ◽  
And Control ◽  
Spool Valve ◽  
Axial Piston

An in-line axial-piston swash-plate pump with pressure compensator is widely used for its fast speed of response and power economy. Although several simulation based design approaches exist to minimize issues like fluid-born noises, ample scope exists for more exhaustive design analysis. The most popular pressure compensator for a variable displacement pump with a spool valve actuating the control and bias cylinders has been taken up here. With an existing comprehensive flow dynamics model, an updated model for swiveling dynamics has been coupled. The dynamics also includes the force containment and friction effects on the swash plate. A design optimization has been accomplished for the pressure compensator. The target of the optimal design has been set as minimizing the transient oscillations of the swash plate, the compensator spool, pressures in the bias and control cylinders along with avoidance of both over-pressurization and cavitation in the bias cylinder. It has been found that the orifice diameters in the spring-side and at the metering port of the spool valve and in the backside of the bias cylinder have critical role in arriving at an optimum design. The study has led to a useful design procedure for a pressure compensated variable displacement pump.

Dynamic Modeling of an Indexing Valve Plate Pump

1999 ◽  
Author(s):  
J. Cho ◽  
X. Zhang ◽  
S. S. Nair ◽  
N. D. Manring
Keyword(s):  
Nonlinear Modeling ◽  
Open Loop ◽  
Valve Plate ◽  
Governing Equations ◽  
Pump Design ◽  
Pressure Port ◽  
Swash Plate ◽  
Plate Design ◽  
Displacement Pump ◽  
Variable Displacement

Abstract The swash-plate in a variable displacement pump experiences very large forces and moments that try to dislocate its position and therefore a large device is required for adequate control. In this paper, the dynamics of an alternative pump design using an indexing valve plate to position the swash-plate are reported. The indexing valve plate design is aimed at controlling the pressure transition for a piston, which is moving from a high-pressure port to a low-pressure port and back. In this paper, the governing equations for the pump are derived and the detailed open-loop, which is necessary for understanding the overall dynamic characteristics of the pump, is reported. Also, linear and nonlinear modeling approaches for the system are compared.

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