Abstract: A new type of double nozzle-flapper water hydraulic servo bridge model is developed, in which the two tandem fixed dampers are adopted as prepositive dampers. The parameter sensitivity analysis for the hydraulic bridge is carried out. The relationship among the flapper displacement, the spool speed and the pressure at the two ends of the spool is investigated. The orthogonal design is employed to study the influence of the physics factors on the characteristics of the hydraulic bridge, such as the diameter of the nozzle, the diameters of the two tandem fixed dampers, the spool diameter and its sliding speed, the initial clearance between nozzle and flapper. The results reveal that (1) the smaller initial clearance between nozzle and flapper, the larger diameter of spool and the clearance between spool and valve body, the shorter overlap length of spool and valve body, and the higher system pressure, will lead to the better linearity of the control characteristics for the water hydraulic bridge; (2) for hydraulic bridge of water servo valve including the two-stage dampers, the smaller first damper diameter, the larger second damper diameter, the smaller pipe diameter before the nozzle, the larger diameter of spool and the clearance between spool and valve body, will bring the higher dynamic response in the water hydraulic bridge. These research results will lay the theoretical foundation for the development of water hydraulic servo valve.

Key words: Hydraulic bridge, Orthogonal design, Servo valve, Two-stage damper, Water hydraulics