On using unstable electrohydraulic valves for control

Kailash Krishnaswamy, Perry Y. Li

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


High bandwidth, high flow rate electrohydraulic valves typically have two or more stages. Most multi-stage valves are expensive, require meticulously clean fluid, and introduce higher order dynamics. On the other hand, single-stage spool valves are cheaper and more reliable. However, a majority of them are not suitable for high bandwidth, high flow rate applications due to limitations of the electromechanical/solenoid spool-stroking actuators. In this paper, we investigate the feasibility ofreducing this limitation by exploiting the transient flow forces in the valve so as to achieve spool dynamics that are intrinsically open-loop unstable. While conventional valves are designed to be open-loop stable, the unstable valve design has to be stabilized via closed-loop feedback. Simulation case studies are conducted to examine the potential dynamic and energetic advantages that an unstable valve may offer. These studies indicate that unstable valves provide faster response than the stable counterparts when stroking forces are limited. Moreover, unstable valves tend to require less positive power and energy to operate.

Original languageEnglish (US)
Pages (from-to)183-190
Number of pages8
JournalJournal of Dynamic Systems, Measurement and Control, Transactions of the ASME
Issue number1
StatePublished - Mar 2002


  • Electrohydraulic valves
  • Flow instability
  • Solenoid actuator
  • Transient forces
  • Unstable flow forces
  • Unstable valves

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