The segmented leakage flow equation of positive overlap servo-proportional valve (POSPV) has been built by using Bernoulli equation and Momentum Theorem to describe its characteristics under various spool stroke conditions. The pressure gain equation of the POSPV is derived from the sectional leakage flow equation. The pressure gain diagram of the POSPV is simulated using the sectional equation and the traditional linearized sharp-edged orifice equation model. A type of direct-driven POSPV was tested under low-Reynolds-number conditions, and the sectional pressure gain equation was shown to accurately describe the POSPV’s characteristics. These findings were verified through simulations and experiments. Additionally, the sectional pressure gain equation under low-Reynolds-number conditions reveals the internal matching relationship between the spool and the sleeve or chamber. The idea in the current study has some benefit to guide a practical design and analysis of the POSPV.
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