NOMENCLATURE

A 2D servo valve designed with zero-overlap is proposed. First, the pilot leakage of the 2D servo valve with a zero-overlap of pilot stage is analyzed theoretically. Based on the analysis to the flow field of the clearance between two parallel plates, the overall pilot leakage is calculated through integration. Secondly, the mathematical model of the axial motion of the spool in respect to rotary motion is established and the dynamic response of 2D servo valve is investigated by simulation. Finally, to validate the analysis, the prototype of a 2D valve with flow capacity of 300L/min (at 7Mpa) is fabricated and the pilot leakage and the actual step response are measured. The results of the experiment show that the pilot leakage is about 0.6L/min at 21Mpa and the response time for the step input is 7ms. It is concluded from both theoretic analysis and simulation that the 2D servo valve with a zero-overlap of pilot stage has a fairly fast dynamic response, and its pilot leakage is very small, less than 0.2%