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Research Papers

Design, Modeling, and Validation of a High-Speed Rotary Pulse-Width-Modulation On/Off Hydraulic Valve

[+] Author and Article Information
Haink C. Tu

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455tuxxx021@umn.edu

Michael B. Rannow

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455rann0018@umn.edu

Meng Wang

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455wangx833@umn.edu

Perry Y. Li1

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455perry-li@umn.edu

Thomas R. Chase

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455trchase@umn.edu

James D. Van de Ven

Center for Compact and Efficient Fluid Power, Department of Mechanical Engineering,  University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455vandeven@umn.edu

Prelief and Pcheck are sized such that Prelief  = Pload  + Pcheck at the maximum load pressure tested (6.9 MPa). Pcheck  > Popen  + Pspool .

The test stand reservoir is unsealed, contains no baffling, and the return lines are not submerged and are located near the pump inlet. As a result, splashing occurs in the oil at the PWM frequency due to the tank line.

Efficiency is given on an absolute scale (0–1) rather than percentages.

1

Corresponding author.

J. Dyn. Sys., Meas., Control 134(6), 061002 (Sep 13, 2012) (13 pages) doi:10.1115/1.4006621 History: Received December 31, 2009; Revised April 11, 2012; Published September 13, 2012

Efficient high-speed on/off valves are an enabling technology for applying digital control techniques such as pulse-width-modulation (PWM) to hydraulic systems. Virtually variable displacement pumps (VVDPs) are one application where variable displacement functionality is attained using a fixed-displacement pump paired with an on/off valve and an accumulator. High-speed valves increase system bandwidth and reduce output pressure ripple by enabling higher switching frequencies. In addition to fast switching, on/off valves should also have small pressure drop and low actuation power to be effective in these applications. In this paper, a new unidirectional rotary valve designed for PWM is proposed. The valve is unique in utilizing the hydraulic fluid flowing through it as a power source for rotation. An unoptimized prototype capable of high flow rate (40 lpm), high speed (2.8 ms transition time at 100 Hz PWM frequency), and low pressure drop (0.62 MPa), while consuming little actuation power (<0.5% full power or 30 W, scavenged from fluid stream), has been constructed and experimentally validated. This paper describes the valve design, analyzes its performance and losses, and develops mathematical models that can be used for design and simulation. The models are validated using experimental data from a proof-of-concept prototype. The valve efficiency is quantified and suggestions for improving the efficiency in future valves are provided.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Bleed off circuit

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Figure 2

Two VVDP implementations. Qvol and Qacc represent the net flows into the inlet volume and accumulator.

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Figure 3

Rotary valve spool/sleeve assembly. The spool rotates and translates within the sleeve bore.

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Figure 4

Three-way helical spool concept. Internal passages connect the center section (responsible for PWM) to one of the two adjacent outlet turbines. The dark gray portions of the spool are hydraulically connected and permit flow from the inlet to the load. Similarly, the light gray sections connect the inlet to tank.

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Figure 5

2D representation of the rotary valve’s geometry including variable definitions used in Sec. 4

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Figure 6

Top: Inlet pressure (Pin ) profile over one PWM cycle (2πNrad spool rotation) for the two circuits in Fig. 2. Bottom: Corresponding profiles of the valve inlet nozzle open areas (A(θ)) to load or to tank.

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Figure 7

Comparison of transition losses for relief and check circuits

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Figure 8

Top: Yu pressure dependent bulk modulus for various fractions (r) of air entrainment and no dissolved air. Bottom: Unit compression energy required to compress fluid from Ptank to Pload .

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Figure 9

Inlet and outlet turbines with their control volumes

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Figure 10

Pocketed volume and corresponding CFD model

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Figure 11

Normalized pocket shear (K = −0.653)

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Figure 12

Power required to overcome viscous friction

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Figure 13

Prototype rotary valve hardware

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Figure 14

15 Hz pressure profiles: 50% travel

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Figure 15

15 Hz pressure profiles: Pload  = 2.8 MPa

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Figure 16

75 Hz pressure profiles: 50% travel

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Figure 17

PWM frequency versus Qin (loglog)

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Figure 18

Output flow versus axial position (15 Hz)

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Figure 19

Efficiency at 15 Hz: relief

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Figure 20

Efficiency at 15 Hz: check

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Figure 21

Efficiency at 75 Hz: relief

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Figure 22

Leakage across helical land

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