Study On Synchronous Control Method For Electro-hydraulic Servovalve-controlled Cylinders With Uncertain Parameters

Electro-hydraulic servo systems have been widely used in military, industrial and civilianfields because they have many distinct advantages, such as high power-to-size ratios, highsystem stiffness and fast response speed. According to different combinations of controlcomponents and executive components, actuating units of electro-hydraulic servo systemscan be divided into several types in which valve-controlled cylinder (VCC) system is mostcommon. VCC system is typical highly nonlinear system. Precise control of VCC is verydifficult because there are lots of time-varying or hard-to-model uncertain parameters in themathematical model. Especially with the development of industry technology, peoplefrequently need to control more than one VCC synchronously. Consequently, study onsynchronous control method for electro-hydraulic servovalve-controlled cylinders withuncertain parameters is very important.Based on two sets of individual valve-controlled single-rod cylinder systems, this thesisfocuses on high-precision synchronous control when the system suffer from time-varyingparameters such as bulk modulus and internal leakage coefficient, frictions that can not bemodeled exactly, and uncertain load disturbances.High-precision control of single VCC is the basis of high-precision synchronous controlof double VCCs. After analyzing mathematical equations including all quantities fromcontrol signal to piston displacement, this thesis establish accurate mathematical model ofVCC first and then propose three control strategies of single VCC: nonlinearitycompensated PID control, feedforward control couple with PID control, adaptive robustcontrol with improved adaptation law. All control strategies are tested for a comparativeanalysis in simulation and experiment.This thesis chooses to study cross-couple control method by analyzing applicationoccasions of common synchronous control strategies when research of control strategy ofsingle VCC is done. A fuzzy control method considering position error, velocity error andvelocity of VCC is proposed as synchronous control method. Besides, conventional PIDcontrol method is designed for comparison. Two methods are combined with ARC andtested in simulation and experiments.