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Research Papers

Discrete Linear Time Invariant Analysis of Digital Fluid Power Pump Flow Control

[+] Author and Article Information
Per Johansen

Fluid Power and Mechatronic Systems,
Department of Energy Technology,
Aalborg University,
Aalborg 9220, Denmark
e-mail: pjo@et.aau.dk

Daniel B. Roemer

Fluid Power and Mechatronic Systems,
Department of Energy Technology,
Aalborg University,
Aalborg 9220, Denmark
e-mail: dbr@et.aau.dk

Torben O. Andersen

Fluid Power and Mechatronic Systems,
Department of Energy Technology,
Aalborg University,
Aalborg 9220, Denmark
e-mail: toa@et.aau.dk

Henrik C. Pedersen

Fluid Power and Mechatronic Systems,
Department of Energy Technology,
Aalborg University,
Aalborg 9220, Denmark
e-mail: hcp@et.aau.dk

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received January 4, 2016; final manuscript received March 30, 2017; published online June 28, 2017. Assoc. Editor: Kevin Fite.

J. Dyn. Sys., Meas., Control 139(10), 101007 (Jun 28, 2017) (8 pages) Paper No: DS-16-1005; doi: 10.1115/1.4036554 History: Received January 04, 2016; Revised March 30, 2017

A fundamental part of a digital fluid power (DFP) pump is the actively controlled valves, whereby successful application of these pumps entails a need for control methods. The focus of the current paper is on a flow control method for a DFP pump. The method separates the control task concerning timing of the valve activation and the task concerning the overall flow output control. This enables application of linear control theory in the design process of the DFP pump flow controller. The linearization method is presented in a general framework and an application with a DFP pump model exemplifies the use of the method. The implementation of a discrete time linear controller and comparisons between the nonlinear model and the discrete time linear approximation shows the applicability of the control method.

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References

Figures

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Fig. 1

Displacement chamber with a check valve connection to the high-pressure manifold and an electrically controlled valve connection to the low-pressure manifold [22]

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Fig. 2

Fluid power system used as basis for simulation study of the proposed method

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Fig. 3

DFP pump flow control system overview

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Fig. 4

LPV plunger position and displacement chamber volume as function of rotational angle at partial pumping operation

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Fig. 5

Model-based valve timing control overview

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Fig. 6

Relation between closing angle, load pressure, and displacement fraction. The gray plane indicates a limit, where later closing angles produce zero or negative displacement fraction.

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Fig. 7

Comparison between discrete LTI model and the nonlinear model, where the displacement fraction sampling angle deg and angular velocity of the pump θ˙=1500 rpm. ξ=0.1.

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Fig. 8

Comparison between discrete LTI model and the nonlinear model, where the displacement fraction sampling angle θdfs=120 deg and angular velocity of the pump θ˙=1500 rpm. ξ=0.3.

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Fig. 9

Comparison between discrete LTI model and the nonlinear model, where the displacement fraction sampling angle θdfs=120 deg and angular velocity of the pump θ˙=1500 rpm. ξ=0.5.

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Fig. 10

Comparison between discrete LTI model and the nonlinear model, where the displacement fraction sampling angle θdfs=120 deg and angular velocity of the pump θ˙=1500 rpm. ξ=0.7.

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Fig. 11

Discrete LTI flow control system overview

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Fig. 12

Root-locus of PID-compensated DFP pump, with Kgain = 0.25 at black markers and Kgain = 0.5 at gray markers

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Fig. 13

Comparison between simulation results from discrete LTI model and nonlinear model of PID-compensated DFP pump. Kgain = 0.25.

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Fig. 14

Comparison between simulation results from discrete LTI model and nonlinear model of PID-compensated DFP pump. Kgain = 0.5.

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Fig. 15

Comparison between simulation results from discrete LTI model and nonlinear model of PID-compensated DFP pump. Kgain = 0.25.

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Fig. 16

Comparison between simulation results from discrete LTI model and nonlinear model of PID-compensated DFP pump. Kgain = 0.5.

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