Semi-analytical modeling and dynamic improvement of a high-speed on/off valve considering nonlinear flux leakage of working air gaps

A high-speed on/off valve (HSV) is a core component of aerospace digital hydraulic systems, and its dynamic performance is crucial for system reliability. A multistage voltage control (MSVC) strategy that uses current-based feedback can improve dynamic characteristics. However, setting the critical feedback parameters, including the pre-opening and pre-closing currents, for the MSVC strategy depends on an accurate mathematical model of the HSV, particularly its magnetic model. Existing magnetic models typically ignore the changes in the magnetic flux leakage of the working air gaps (WAGs) to simplify the model, leading to deviations in the electromagnetic force calculations and limiting the potential of the MSVC strategy. This study presents a refined magnetic model using an equivalent magnetic circuit method that incorporates variations in the flux leakage of WAGs. Effective magnetic flux coefficients are introduced to quantify flux leakage. The relationship between the effective flux coefficients and the thickness of the WAGs is revealed by finite element simulation. A high-precision semi-analytical magnetic model for the HSV was established. Based on this, a current-based feedback MSVC strategy is proposed to improve the HSV dynamics. The simulation and experimental results validate the proposed model and control strategy. The results indicate that the effective flux coefficients decrease nonlinearly with the thickness of the WAGs, following a cubic relationship. The proposed model closely aligns with experimental data, exhibiting maximum deviations of only 6.0% (3.6 N) for electromagnetic force and 2.9% (0.39 ms) for total response time. Furthermore, compared with the previous model, utilizing the proposed model allows more accurate feedback parameter settings for the MSVC strategy, significantly reducing opening delay time by 70.7% (0.52 ms). This study offers a practical approach for fine modeling and dynamic performance improvement of HSVs.