New Dead-zone Compensation Approach for Proportional Flow Valve

To solve the dead-zone in the output flow curve of the proportional flow valve without displacement sensor, a dead-zone compensation approach is proposed in this paper. Instead of detection and feedback of the valve spool position, the proposed approach adopted the pressure drop across the valve metering orifice to accomplish the dead-zone compensation. The first step was to test and get the maximum output flow, Qmax , at a preset reference pressure drop, such asΔP0 . The next step was to construct the target compensation flow curve, which is a line through (0, 0) and (ΔP0, Qmax ). Then a compensation law was designed to approach the target curve. However, the research results show that the above strategy caused over-compensation once the actual pressure drop deviated from ΔP0 . Thus a correction coefficient,β, was presented to correct the initial compensation law as the pressure drop deviated fromΔP0 . For example, the test results indicate that the corrected compensation approach could reduce the dead-zone from 53.9％ to 3.5％ at a pressure drop of 1 MPa;as the pressure drop was increased to 5 MPa, the dead-zone was reduced from 51.7％ to 3.5％. Therefore, the following conclusions can be drawn:the proposed compensation approach is feasible, which can effectively reduce the dead-zone and improve the output flow static performance of the proportional flow valve without spool displacement feedback.