Dept. Of Mechanical and Industrial Engineering University of Illinois at UrbanaChampaign

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Modeling of a ValvistorFundamental Performance
Limitations for a Class of Electronic Two-stage
Proportional Flow Valves

• Eko Prasetiawan, Rong Zhang, Andrew Alleyne
• University of Illinois at Urbana-Champaignprojec
  t sponsor Caterpillar Inc.
• WM01-6, June 27th, 2001
• ACC2001, Arlington, VA

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1. Introduction
Introduction Method Results
Discussions Conclusions

• System Description
• Pilot flow
• Variable orifice the slot
• Mission
• To model the valvistor
• To reveal a fundamental performance limitation
• To suggest cautions in control design and valve
  design

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System Description
Introduction Method Results
Discussions Conclusions
Control Force
BIGsolenoid
BULKY structure,No position feedback
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System Description
Introduction Method Results
Discussions Conclusions

• Major design features
• Main valve using hydraulic force (?P) instead of
  solenoid force
• Using a variable orifice (the slot) to give a
  position feedback
• The analogy
• Valvistor A hydraulic transistor

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System Description
Introduction Method Results
Discussions Conclusions
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2. Method
Introduction Method Results
Discussions Conclusions

• Detailed model
• Simplified model
• Experimental ID

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Detailed Model
Introduction Method Results
Discussions Conclusions

• Pilot valve dynamics
• Lumped volume between stages
• Main valve dynamics

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Detailed Model
Introduction Method Results
Discussions Conclusions
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Simplified Model
Introduction Method Results
Discussions Conclusions

• Block diagram of the linearized model

Main valve dynamics
Main orifice
Pilot flowcontribution
Position feedback
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System ID
Introduction Method Results
Discussions Conclusions
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System ID
Introduction Method Results
Discussions Conclusions

• Motor speed --gt Valve flow

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System ID
Introduction Method Results
Discussions Conclusions

• To separate the valve dynamics from that of the
  motor

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3. Results and Discussion
Introduction Method Results
Discussions Conclusions

• Frequency domain ID

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Model fitting
Introduction Method Results
Discussions Conclusions

• With the motor dynamics
• The final valve dynamics

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Time Domain Validation
Introduction Method Results
Discussions Conclusions
Motor Speed (rpm)
Downstream Pressure (psi)
Time(s)
Time(s)
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Discussions
Introduction Method Results
Discussions Conclusions
Root Locus of a Valvistor controlled gear motor
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Simplified Model
Introduction Method Results
Discussions Conclusions

• How to reduce the zero effect?

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4. Conclusions
Introduction Method Results
Discussions Conclusions

• A detailed valvistor model (5 states)
• A reduced 2nd order model (2 zeros)
• Model parameters identified and validated in
  experiments
• Suggestions to reduce the zero effect
• To bleed the pilot valve
• To increase the gain from the pilot flow to the
  main flow

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• Questions?
• Web http//mr-roboto.me.uiuc.edu/evps