Control Characteristics Of D+A Combined Multi-pump Controlled System

Energy consumption in hydraulic industry has been attracting great concern due to the issue of energy crisis today.Especially for high power multi-pump hydraulic system,the flow and pressure of pumps source are not in full load condition,so the system efficiency is relatively low.Despite the fact that conventional pump controlled systems have reduced energy consumption significantly,multiple parallel fixed displacement pumps are still used in some large power hydraulic systems with the consideration of lower initial investment.However,for these discrete variable flow systems,the problem is still existing on matching the pump supply and actuator demand with respect to the flow rate and pressure.To increase system efficiency with lower overflow rate and lower overflow pressure,according to the concept of PCM(Pulse Code Modulation)digital pump,a novel configuration of multi-pump source,similar to a pump-controlled system,is proposed for a large power hydraulic system in this study.The main research of this study is as followings:(1)Research on Configuration rules and evaluation standard of D+A multi-pump combined control source hydraulic system.It takes into account flow deviation,switching impact,switching frequency and total cost of pumps in flow region-dependent segmentation method.(2)Model the D+A multi-pump combined control source,actuating unit and pump controlled asymmetric cylinder system.The flow state matrix and pressure build-up equations are get by means of theoretical solution.The main parameters,such as pump displacement,pipeline parameters,natural frequency of unloading valve and system pressure,were analyzed to optimizing the opening time of quantitative pump.(3)Test and simulate on the proposed system in the pump control mode and pump-valve compound control mode.Basic flow characteristics and factors influencing t he switching time of pump source are obtained via experiment and simulation.The experimental result indicated that response speed and control precision of cylinder achieved the expected control effect,which verifies the feasibility of the new system in control and energy saving.That is,the output flow rate of D+A pumps can be controlled in a demand output and system pressure is also can be regulated according to the working load in real time,achieving low energy losses even zero overflow and zero overflow pressure.