Development of High-flow Servovalve Overlap Value Hydraulic Measuring System

As servo valve is used as a central component which converts the weakcurrent into high power hydraulic control in the electric-hydraulic servo-systems,its current-fluid signal has a decisive effect on the control accuracy of the wholeelectric-hydraulic servo-system. Recently, because higher power and controlaccuracy requirement is raised to the performance of electric-hydraulic servo-system, the current-fluid conversion range and linearity of servo valve need to beimproved. And the size and symmetry of the overlap of spool valve exerts a vitalinfluence on the linear characteristic of servo valve. The overlaps need accuratemeasurement to achieve high accuracy.Firstly, this dissertation introduces the hydraulic measurement theory of thehigh-flow servo valve overlap, establishes the real spool valve model andanalyzes the theory error and repeatability error.Secondly, the dissertation gives the whole design scheme which consists ofhardware and software based on the measurement theory. Then the hardware isdesigned before the software is developed. The hardware platform is made up ofthe mechanical fixture part, the hydraulic part, the electro-circuit part and the IPCpart. Among them, the mechanical fixture part can not only locate and clamp thespool valve, but also make the spool axially movable; The hydraulic part whichprovides the system with measuring medium includes measuring circuit,hydraulic manifold block, pump unit and so on; The electro-circuit part whichaims at transmitting, adjusting and showing the signal from the transmitters andsensors; The IPC part is in charge of other equipments, which includes IPC，various data acquisition cards and control cards. This dissertation adopts VC++programming language in the VS2005programming environment and uses dataacquisition, multithreading and database technology etc.Finally, the dissertation not only debugs the measuring system including thedisplacement calibration and program debugging, but also measures the overlapof the sample. After collecting and analyzing the test outcomes, the dissertationconcludes that this test system can measure the overlap value automatically andrepeatability precision and measuring precision meet the design requirement.