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.

scholarly journals The Dynamic Response of Tuned Impact Absorbers for Rotating Flexible Structures

2005 ◽  
Vol 1 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Steven W. Shaw ◽  
Christophe Pierre
Keyword(s):  
Dynamic Response ◽  
Flexible Structures ◽  
Experimental Studies ◽  
Analytical Investigation ◽  
Design Parameters ◽  
System Response ◽  
Rotor Speed ◽  
Flexible System ◽  
Restoring Forces ◽  
And Performance

This paper describes an analytical investigation of the dynamic response and performance of impact vibration absorbers fitted to flexible structures that are attached to a rotating hub. This work was motivated by experimental studies at NASA, which demonstrated the effectiveness of these types of absorbers for reducing resonant transverse vibrations in periodically excited rotating plates. Here we show how an idealized model can be used to describe the essential dynamics of these systems, and used to predict absorber performance. The absorbers use centrifugally induced restoring forces so that their nonimpacting dynamics are tuned to a given order of rotation, whereas their large amplitude dynamics involve impacts with the primary flexible system. The linearized, nonimpacting dynamics are first explored in detail, and it is shown that the response of the system has some rather unique features as the hub rotor speed is varied. A class of symmetric impacting motions is also analyzed and used to predict the effectiveness of the absorber when operating in its impacting mode. It is observed that two different types of grazing bifurcations take place as the rotor speed is varied through resonance, and their influence on absorber performance is described. The analytical results for the symmetric impacting motions are also used to generate curves that show how important absorber design parameters—including mass, coefficient of restitution, and tuning—affect the system response. These results provide a method for quickly evaluating and comparing proposed absorber designs.

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.

Theoretical and experimental studies of the steady-state performance of a primary and secondary-controlled closed-circuit hydrostatic drive

2019 ◽  
Vol 233 (5) ◽  
pp. 1024-1035
Author(s):  
Ajit Kumar Pandey ◽  
Alok Vardhan ◽  
K Dasgupta
Keyword(s):  
Steady State ◽  
System Modeling ◽  
Experimental Studies ◽  
Simulation Method ◽  
Closed Circuit ◽  
Displacement Pump ◽  
Torque Loss ◽  
Variable Displacement ◽  
Graph Simulation ◽  
Steady State Performance

In this article, performance of a closed-circuit hydrostatic drive in primary and secondary mode of operations has been studied through theory and experiment. This drive consists of a variable displacement pump that supplies pressurized fluid to a variable displacement hydro-motor of bent axis design. Bond graph simulation method is adopted for system modeling. In the model, the losses of the drive are accounted by suitable resistive elements, and their characteristics are identified through experiments. The predicted drive’s performances are studied with respect to the overall efficiency, torque loss (%), and slip at different torque levels which are also validated experimentally. The investigation made in the article identifies the efficient zone of operation of the drive which will be useful to the practicing engineers to select such a drive used in heavy constructional equipment. From the steady-state performance of the pump and the motor, their critical control parameters are identified. The studies may be useful for the design of the suitable control strategy to obtain the optimum performance of the drives.

Modeling and Control Design of a Powertrain Simulation Testbed for Earthmoving Vehicles

1999 ◽  
Author(s):  
Eko A. Prasetiawan ◽  
Rong Zhang ◽  
Andrew G. Alleyne ◽  
Tsu-Chin Tsao
Keyword(s):  
First Principles ◽  
Control Design ◽  
System Response ◽  
Prime Mover ◽  
Linear Quadratic ◽  
Modeling And Control ◽  
Initial Control ◽  
Displacement Pump ◽  
Variable Displacement ◽  
And Control

Abstract A nonlinear model of an Earthmoving Vehicle Powertrain Simulator is developed using both first principles as well as I/O data. The model is an interconnection of subsystem models, which consist of a prime mover, a variable-displacement pump, proportional flow valves, and fixed-displacement motor models. In addition, a typical drive or tractive load of an earthmoving vehicle is also presented and implemented in the system as one of the loads. Efforts have been directed to develop a simple model in order to cater to developing and testing powertrain controllers as well as studying the dynamic behavior of such systems. An initial control design approach utilizing the Linear Quadratic technique is also presented. The controller is aimed at regulating load speeds in presence of a step load disturbance. The simulation results of the compensated system response are presented.

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.

On/Off Valve Based Position Control of a Hydraulic Cylinder

2007 ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Position Control ◽  
Hydraulic Cylinder ◽  
Conventional Technique ◽  
Hydraulic Systems ◽  
Hydraulic Actuator ◽  
Nonlinear Controller ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Averaged Model ◽  
Valve Control

A method of precisely controlling the position of a hydraulic actuator using an on/off valve is developed. Since valves exhibit little power loss when they are fully open or fully closed, the proposed system is more efficient than throttling valve control and can achieve flow variation without the expense or bulk of a variable displacement pump. Mating a pulse-width-modulated (PWMed) on/off valve with a fixed displacement pump and a smoothing accumulator creates a software enabled variable displacement pump. A drawback of using digital valve control for hydraulic systems is that the relatively low speed of the currently available switching valves results in a significant ripple in the pressure and flow rate. We propose a solution to this problem by using a throttling valve to shield the actuator from the ripple in the output. This creates an effective load sensing system with the throttling valve used only to provide a small known pressure drop between the supply and the load. This approach is significantly more efficient than the conventional technique of using throttling to vary the full flow. This paper presents an averaged model of the system, a nonlinear controller to achieve position control of an actuator and a simulation based study of the effectiveness of the controller.

Experimental Studies of a Novel Alternating Flow (AF) Hydraulic Pump

2017 ◽  
Author(s):  
Ryan J. Foss ◽  
Mengtang Li ◽  
Eric J. Barth ◽  
Kim A. Stelson ◽  
James D. Van de Ven
Keyword(s):  
Phase Angle ◽  
Experimental Studies ◽  
Companion Paper ◽  
Pump Efficiency ◽  
Operating Pressure ◽  
Displacement Control ◽  
Displacement Pump ◽  
Pressure Dynamics ◽  
Variable Displacement ◽  
Control Circuits

The ideal variable displacement pump for a displacement control circuit is efficient across a wide operating range and readily mounted on a common shaft with multiple pumps. This paper presents a novel variable displacement pump architecture for displacement control circuits that uses the concept of alternating flow (AF) between piston pairs that share a common cylinder. The displacement is adjusted by varying the phase angle between the piston pairs. When the pistons are in phase, the pump displacement is at a maximum and when the pairs of pistons are out of phase, fluid is shuttled between the pistons and the pump produces no net flow. A prototype of the AF pump was constructed from two inline triplex pumps that were modified so that three piston pairs were created. The crankshafts of the two pumps were connected via a sprocket-and-chain transmission. The sprockets allow for accurate measurement of the phase angle, which is adjusted, in this early phase prototype, by disassembling the chain and shifting the sprockets. The prototype AF pump was then mounted to the test stand and experiments were conducted to map the AF pump efficiency and cylinder pressure dynamics across a range of operating pressure, speed, and displacement. The AF pump’s efficiency was measured for 8 diferent phase angles with an efficiency of near 90% at full flow and 65% at 36% displacement. The experimental results were compared to simulation results, presented in a companion paper at this conference.

An Adaptive Pressure Servo-Control Design for Variable Displacement Pumps

2000 ◽  
Author(s):  
Hongliu Du ◽  
Noah D. Manring
Keyword(s):  
Adaptive Learning ◽  
Control Design ◽  
Time History ◽  
Order System ◽  
Loop Control ◽  
Control Approach ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Discharge Pressure ◽  
Variable Displacement Pumps

Abstract In this paper, a new pressure control scheme for a variable displacement pump is proposed under the consideration of various system uncertainties. The control design reported in this paper provides an effective approach for controlling the discharge pressure of variable displacement pumps to asymptotically track the desired pressure time history. With the provided nonlinear control design, the output pressure error dynamics are presented in a first order system with which the system performance is restricted by the limitations on control actuation, unmodeled dynamics, and parametric uncertainties. The discharge pressure overshoot is eliminated for the compensated closed-loop control system. On-line adaptive learning is introduced to compensate for the uncertainty in the pressure carry-over angle, which induces the most significant torque on the swashplate in a variable displacement pump. Experimental results are provided to validate the effectiveness of the proposed control approach.

EXPERIMENTAL STUDIES OF REINFORCED CONCRETE STRUCTURES WITH CROSS-SHAPED SPATIAL CRACK UNDER TORSION WITH BENDING

2020 ◽  
Vol 92 (6) ◽  
pp. 13-25
Author(s):  
Vl.I. KOLCHUNOV ◽  
◽  
A.I. DEMYANOV ◽  
M.M. MIHAILOV ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Determination ◽  
Calculation Method ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Design Parameters ◽  
Reinforced Concrete Structures ◽  
Experimental Scheme

The article offers a method and program for experimental studies of reinforced concrete structures with cross-shaped spatial crack under torsion with bending, the main purpose of which is to check the design assumptions and experimental determination of the design parameters of the proposed calculation method. The conducted experimental studies provide an opportunity to test the proposed calculation apparatus and clarify the regularities for determining deflections, angles of rotation of extreme sections, and stresses in the compressed zone of concrete. For analysis, the article presents a typical experimental scheme for the formation and development of cracks in the form of a sweep, as well as characteristic graphs of the dependence of the angles of rotation of end sections.

Sign in / Sign up

Export Citation Format

Share Document