Aimed at discrete character of complex pneumatic control valve, the 120 emergency valve was taken as an example. Under the theory of power bond graph and model approximation and introduction of controllable node and virtual element, the mathematic model of 120 emergency valve was built with uniform causality in different working modes. The created bond graph was utilized to research the effects of two structural parameters (aperture size of hole Ⅲ and gap between piston rod and push rod) on stability and emergency sensitivity. Analysis results show that when the diameter is designed as 2.5 mm, the selection range of the gap will be 3–3.5 mm; when the gap is designed as 3 mm, the diameter will be 2.5–2.7 mm. The proposed method may be commonly applied to modelling and analysis of other complex pneumatic control valve.
120 emergency valve, bond graph, pneumatic control valve, railway, simulation model
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