Research Papers

Model-Based Condition Monitoring of an Electro-Hydraulic Valve

[+] Author and Article Information
Andreas Steinboeck

Postdoctoral Research Assistant
e-mail: andreas.steinboeck@tuwien.ac.at

Wolfgang Kemmetmüller

Assistant Professor
e-mail: kemmetmueller@acin.tuwien.ac.at

Andreas Kugi

e-mail: kugi@acin.tuwien.ac.at
Automation and Control Institute,
Vienna University of Technology,
Gußhausstraße 27-29/376,
Vienna 1040, Austria

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the Journal of Dynamic Systems, Measurement, and Control. Manuscript received March 7, 2012; final manuscript received April 19, 2013; published online August 23, 2013. Assoc. Editor: Warren E. Dixon.

J. Dyn. Sys., Meas., Control 135(6), 061010 (Aug 23, 2013) (9 pages) Paper No: DS-12-1077; doi: 10.1115/1.4024800 History: Received March 07, 2012; Revised April 19, 2013

In many hydraulic systems, it is difficult for human operators to detect faults or to monitor the condition of valves. Based on dynamical models of an electro-hydraulic servo valve and a hydraulic positioning unit, we develop a parametric fault detection and condition monitoring system for the valve. Our approach exploits the nexus between the spool position, the geometric orifice area, the flow conditions at wearing control edges, and the velocity of the controlled cylinder. The effective orifice area of each control edge is estimated based on measurement data and described by aggregate wear parameters. Their development is monitored during the service life of the valve, which allows consistent tracking of the condition of the valve. The method is suitable for permanent in situ condition monitoring. Flow measurements are not required. Computer simulations and measurement results from an industrial plant demonstrate the feasibility of the method.

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Fig. 1

Third stage of a four-way servo valve with underlap (not to scale)

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Fig. 2

Hydraulic positioning unit

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Fig. 3

Condition monitoring algorithm

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Fig. 4

Opening area characteristic (simulated data)

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Fig. 5

Simulated change of opening area characteristic due to wear (distorted, αA(x) constant along dotted lines)

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Fig. 6

Estimated parameters indicating wear of the valve (simulated data), (a) relative change of contraction coefficient, (b) normalized change of underlap, (c) normalized error

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Fig. 7

Measurements from two comparable hydraulic positioning units, (a) cylinder positions, (b) normalized spool displacements, and (c) pressure values at control ports

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Fig. 8

Opening area characteristic of a normal and a faulty valve (measured data)

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Fig. 9

Long-term changes of opening area characteristic (measured data, distorted, αA(x) constant along dotted lines)




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