Development Of Electronically Controlled System For Independent Metering Hydraulic Value

With the development of mobile machinery and digital hydraulics,the combination of intelligent control with digital hydraulic component will become the focus of research in the near future.Because of the complicated structure and no on-line feedback of the existing directional control valve for mobile machinery,it is difficult to implement digital control.The usage of a single spool to adjust inlet and outlet throttling area also leads to a high energy consumption.Independent Metering(IM)control technology(IMCT)separately control meter in and meter out orifice with two direction valves,and successively control the velocity of actuator,which has the advantages of increasing hydraulic control flexibility and reducing load back pressure,improve energy saving and control performance of excavator hydraulic system.This thesis firstly reviewed the state-of-the-art research of IMCT at home and abroad,then introduced the development of electro-hydraulic proportional system controller.Secondly it introduced the composition of electric control system of the IM valve,built the mathematical model of the pilot-main valve controlling of IM valve,solved the pilot-main valve transfer function,and studied the system stability and steady-state error,then build that IM valve controlled cylinder mathematical model.Based on the models,it researched the main spool displacement control,load port pressure control,main spool flow control and pressure flow composite control.With AMEsim,we built the controlled system model of IM valve,completed simulation experiments to verify the algorithm feasibility.Finally,we built and developed IM valve electric control system hardware platform and software system to carry out experimental research,which verified the effectiveness of control strategy,hardware platform and software systems.The layout of this thesis is described as follow:In Chapter 1,we pointed out the background and significance of this research,reviewed the state-of-art at home and abroad on IMCT.Based on this,the main research subjects are presented.In Chapter 2,we introduced the composition and control characteristics of IMCT.The mathematical model of IM valve's pilot-main valve and valve controlled cylinder system are researched.Firstly,we built the simulation model with MATLAB/Simulink studied the system stability and steady-state error.Then built IM valve controlled cylinder mathematical model,derived the flow gain factors Kqp1?Kqp2 and pressure gain factor Kcp based on the extend and retract conditions of rod,concluded the unified flow continuity equation of cylinder.With these we set the theoretical basis for the simulation of IM valve controlled cylinder.In Chapter 3,The strategy of IM valve on main spool displacement control,load port pressure control,main spool flow control and pressure-flow control are proposed.With AMEsim,we built hydraulic system and control model,completed the simulation experiment and verified the correctness of the control strategy on excavator boom cylinder.Then,we analyzed the performance of the compound flow control strategy on excavator boom cylinder against the load fluctuation of the compound ramp load.In Chapter 4,the paper built and developed IM valve electric control system hardware platform and software system which mainly included the hardware design of embedded controller,embedded software development and GUI development.Secondly we choose TI C2000 series TMS320F28335 as the main control chip of embedded system.According to the functional requirements we design the smallest system and peripheral circuits,carry out multi-task real-time software control system development based on functional requirements.Finally the GUI interface used LabVIEW as development environment,which included state monitoring,bus congestion self-notification,parameter changes sent,single-interface monitoring multiple charts and the upload data records.In Chapter 5,we carried out experimental research of IM valve,built the hydraulic system of IM valve control system which based on bridge circuit.Then we study the main spool displacement control,load port pressure control,main spool flow control and pressure flow composite control.we studied the influence of the control stability of inlet flow rate based on the back pressure fluctuation,which verified the effectiveness of control strategy,hardware platform and software systems.In Chapter 6,we summarized the main work of paper and maked the prospects for future research.