Research On Stage-based Power Matching Control Of Hydraulic Excavator

Due to the complicated working conditions of hydraulic excavator and the time-varying load,there exists a mismatch between the output of the engine and the demand of load,causing higher fuel consumption and worse emission.The research status quo is summarized in four aspects:the optimization of power source efficiency,the power matching between hydraulic pumps and actuators,the power matching between actuators and load,and the identification of load.By analyzing the shortcomings of existing methods,a new solution is presented.According to different working-cycle stages and working objects,the working points of engine are set reasonably and controlled correspondingly.The major research findings are as follows:1.Research on intelligent identification for working-cycle stages of hydraulic excavator.An intelligent identification method using the pump pressure as the identifying object is proposed to automatically identify each stage of a working-cycle of hydraulic excavator.The segmentation of a working-cycle is achieved by choosing the pressure curves at the beginning or the end of each stage as the segmentation marks which are recognized by the DAGSVM.The structure of DAGSVM is optimized according to the divisibility between samples of each class.A distance threshold is set to ensure the identified curves are the segmentation marks.An intelligent verifying system is introduced to correct the identification errors caused by incorrect operation so that the recognition accuracy is raised from 65%to 95%.Experiment studies show that the proposed method can effectively identify the working-cycle stages,with high recognition accuracy and good real-time performance.2.Research on the stabilization of stage-based control of engine's working points.The principle for setting working points of the engine is determined according to the working conditions of excavator and the characteristics of engine.By analyzing the characteristics of each stage of a working-cycle,the engine's working points of each stage are set.The working points switching control strategy based on maximum acceleration is proposed to realize the fast switching between different working points of engine.The stability of the working points is ensured by employing the approach which combines the torque feedback control strategy and speed feedback control strategy.Finally,experiments are carried out.The results demonstrate that the engine can work stably on given working points in different stages of a working cycle,by using the stage-based control of working points.3.Research on energy saving during hydraulic excavator's rotary starting process.A flow-control energy-saving rotary system is conceived to reduce the energy consumption,which is caused by the mismatching between the output flow of the pump and the demand flow of the rotary motor during hydraulic excavator's rotary starting process.The overflow signal of the overload buffer valve is converted to a pressure signal using a flow control valve,and the pump displacement is adjusted according to the pressure signal.Simulation and experiment results show that the flow-control energy-saving rotary system can effectively reduce the energy consumption during the rotary starting process,and can save more than 20%energy compared with the traditional rotary system.Since the overflow has been long existent,which meets the torque demand during the rotation,the time of rotary process stays the same with that of the traditional rotary system.4.Construction of the test-bed of hydraulic excavator's power matching and related experiment studies.The test-bed of the hydraulic excavator's power matching,which uses proportional relief valves and proportional reduce valves to load the pumps,is built.The scheme of the test-bed is proposed and the function of each subsystem is described.Also,the components of the test-bed are chosen.The characteristics of the engine and the proportional relief valves,and the strategy of power matching are studied using the test-bed.Finally,experiments on actual excavator are carried out.The fuel consumption and working efficiency of stage-based power matching control and different operating mode control strategy are compared.The results show that the stage-based power matching control can reduce 6%fuel consumption per cycle and increase the working efficiency at the same time.