Research On Characteristics Of Hydraulic System Of Construction Machinery Controlled Independently By Fuzzy PID At Inlet And Outlet

Loader is an important type of construction machinery.The research on its energysaving characteristics can provide certain reference value for other construction machinery energy-saving methods.Therefore,this paper takes loader as the main research object and extends the energy-saving mode of loader rocker arm hydraulic system to traditional construction machinery with similar working conditions and carries out experimental research.Traditional loaders often use four-sided linkage multi-way valves to control the piston movement of hydraulic cylinder.In the process of controlling the flow of hydraulic system,the inlet and outlet oil ports throttle simultaneously due to mechanical coupling,resulting in unavoidable throttling pressure loss.Especially for the rocker hydraulic cylinder of loader,its external load changes frequently,operating conditions are complicated and energy loss is more serious.At the same time,the pump source of traditional loader is constant flow system.When the rocker piston of loader is positioned,the change of external load will affect the pressure behind the valve,resulting in inaccurate positioning and poor position control effect.In order to solve the above problems,by combining the advantages of low energy consumption of pump control system,high precision of valve-controlled position system and fast response of load-sensitive technology to pressure control,a variable speed load-sensitive import and export independent control system is proposed.At the same time,a fuzzy PID control method with variable speed load-sensitive import and export parameters can be selected to adjust parameters in real time according to external load disturbance of the system.A load-sensitive hydraulic system with independent control of inlet and outlet of fuzzy PID for loader rocker arm hydraulic system is proposed.This paper takes the hydraulic control system of Xiamen XG916 II loader as the research object,and with the support of the national key R&D plan "High Pressure Multiplex Valve for Construction Machinery","Pump Valve Cooperative Pressure Flow Composite Control Crane Multiplex Valve"(2018YFB2001203),proposes an independent control loader rocker arm hydraulic system based on fuzzy PID.Firstly,the control model,hydraulic model and mechanical model of the loader used in the test are established by MATLAB,AMEsim and LMS-motion respectively,and then the hydraulic system of the original machine is simulated jointly.Then,the established simulation model is verified and corrected according to the test results of the original machine to obtain a loader virtual prototype which is more consistent with the actual situation.Then,the pump source and valve block are replaced on the basis of the original model,and the rocker arm hydraulic system of independent load-sensitive loader with fuzzy PID import and export based on mode switching is built.By combining the advantages of traditional pump-controlled flow system and variable speed load-sensitive pressure control system,the rocker arm hydraulic cylinder can work with low energy consumption and achieve high-precision position control effect.Then the model is simulated according to the actual operating conditions and control requirements of loader rocker arm,and compared with the original machine system.The result shows that the energy consumption of the new system is lower than that of the hydraulic control system of the original machine rocker arm,and the positioning of the piston also obtains good control effect.Finally,according to the control principle of independent load-sensitive import and export system,the test platform of independent import and export control hydraulic system with variable speed and load-sensitive import and export is established and tested.At the same time,the AMESim-MATLAB joint simulation model of the new system is built according to the test parameters,and random load and sinusoidal load signals are introduced as changing loads.In the controller,the energy consumption control mode is combined with position control mode by mode switching.Finally,the results of the test and simulation are compared and concluded.The results show that the designed load-sensitive pressure controller with variable speed has good control effect on system pressure.The position control performance and energysaving effect of load-sensitive inlet and outlet independent control system driven by servo motor with double-acting vane pump as power source are higher than that of traditional pump control and valve control system,and energy-saving is 10.11% higher than that of traditional pump control system.The main research work of this paper is as follows:(1)First put forward the research background and significance of this subject,then analyze the research status of energy-saving for loaders,then analyze the general measures of energy-saving in traditional loaders,introduce the energy-saving status of loader hydraulic control system at home and abroad,and elaborate the development history of multi-way valves and typical hydraulic control system.For the unavoidable throttle pressure loss caused by mechanical coupling of traditional four-sided sliding valve,an independent control system for inlet and outlet is introduced to improve this defect.The research status of import and export independent control system at home and abroad is elaborated.Through these studies,we can know that import and export independent control can not only avoid throttle loss by optimizing control strategy,but also obtain independent control of flow pressure because the system itself breaks mechanical coupling,increasing control freedom and flexibility.At last,the research method and content of this subject are determined for the problems of energy consumption loss existing in the hydraulic system of loader rocker arm.(2)Establish the simulation model of loader-fluid combination used in the test.The three-dimensional model of each part of loader is established by one-to-one mapping of each part with CATIA,then the complete loader model is obtained by assembling according to the position constraints between the parts,and then the dynamic simulation software LMS integrated in CATIA is used.Virtual.Lab Motion constrains the motion pairs of each part and completes the establishment of mechanical dynamic model of loader.The working principle of hydraulic system of loader working device is analyzed and the hydraulic system model of loader is established.According to the multi-way change-over valve used in actual loader,the HCD Library in AMESim is applied to establish its simulation model,and the flow characteristics of the built change-over valve are analyzed.Finally,the mechanical dynamic model and hydraulic system model of the loader working device are simulated jointly by connecting LMS motion and AMESim special interface.During the simulation process,according to the actual working conditions of the loader,the pressure,displacement,speed and other characteristic curves of the loader working device,especially the rocker-arm hydraulic cylinder,are obtained by adjusting the opening of the valve.Finally,the exact loader load curve and virtual prototype are obtained by establishing the original loader hydraulic system test platform,carrying out test verification and modifying simulation model.(3)Analyzing the test and simulation results of loader working device in the working process,analyzing the typical load principle of loader rocker arm hydraulic system,obtaining the load curve of loader rocker arm working process and the four quadrant operating conditions,combining with the research foundation of independent control and fuzzy control of import and export by experts and scholars at home and abroad,According to the working characteristics and actual conditions of rocker arm,an independent rocker arm hydraulic system with variable speed load-sensitive inlet and outlet is proposed.At the same time,the established control model is built in the mathematical simulation software MATLAB by combining the fuzzy PID control method and the control strategy of mode switching of energy consumption and position control method.Finally,the MATLABAMESim simulation model of independent load-sensitive control rocker arm hydraulic system with fuzzy PID is established.The result of joint simulation shows that the rocker arm hydraulic cylinder control system combined with variable speed load sensitive inlet and outlet independent control technology and fuzzy PID control method has better control effect and energy saving effect than the rocker arm hydraulic system controlled by traditional four-sided sliding valve.(4)Aiming at the impedance condition of large energy consumption in the actual working process of rocker-arm cylinder,the test platform of load-sensitive inlet and outlet independent control hydraulic system with variable speed is designed and built and its working principle is introduced.According to the control principle and control strategy,servo motor and double-acting vane pump are used as power source to realize flow matching and load-sensitive functions.Cylinder action is controlled by two proportional valves to achieve independent control of inlet and outlet.According to the actual control method and control strategy,BODAS controller is selected to control the pump and valve at the same time and collect the system feedback signal.The control program in the controller is carried out by the programming software according to the test control requirements.Then build the simulation model of the system according to the test parameters and carry out simulation analysis.Finally,based on the energy-saving advantages and high-precision characteristics of variable speed load-sensitive import and export independent control system,the conclusion is drawn by comparing energy consumption with traditional pump control system and valve control system.