| As the key component for Heavy NC horizontal boring lathe, hydrostatic pressure center frame has much important effect on the machining quality and operation efficiency of Heavy NC horizontal boring lathe. The oil film stiffness of hydrostatic pressure center frame is also a key factor for the property of hydrostatic pressure center frame; it depends on the property of oil supply system of oil chamber, so the study on high-performance electro-hydraulic servo oil supply system is important to the study on high-performance hydrostatic pressure center frame. In this thesis, on the engineering background of new-type hydrostatic pressure center frame, control strategy of oil film stiffness is lucubrated, a suitable and high efficient controller is designed, and oil film active control system is developed. The main contents are as follows:Based on the analysis of different oil supply means of hydrostatic bearing, a new-type hydrostatic pressure center frame of constant oil flow supply is designed, mathematical model of the relationship between oil film thickness and oil film stiffness of oil chamber is built. Based on hydrostatic pressure center frame of heavy NC horizontal boring lathe HT630×200/350-NC, influencing factors of oil film stiffness on hydrostatic pressure center frame are analyzed.According to influencing factors analysis of oil film character, first the active control scheme of oil chamber flow controllable is proposed. Electro-hydraulic position servo control system is selected as flow adjustment mechanism for controllable oil chamber. Four groups’controllable oil chambers adjust and control oil film thickness, and realize desire posture of work piece. Then the model of electro-hydraulic servo oil supply system and controlled oil chamber flow is built, the impact of model parameter on system performance is analyzed. Finally pseudo random signal is adopted as actuating signal source, and the identification experiments are performed using two channel oil film control system. These researches lay foundation for the oil film active control and experimental analysis of hydrostatic pressure center frame.Aiming to control strategy requirements of the oil film electro-hydraulic servo system of hydrostatic pressure center frame, two-stage self-tuning fuzzy-PID compound control strategy is proposed. Two-stage self-tuning fuzzy-PID compound controller is designed. Based on simulation model of the oil film control strategy, the oil film control is analyzed and simulated. The simulation results show that the controller has high speed responsibility and robust capability, and can improve system control performance.Fuzzy-sliding-mode control strategy of the oil film electro-hydraulic servo system of hydrostatic pressure center frame is proposed. Fuzzy control system is used to approximate equivalent control, so this can solve the problem of difficulty in directly obtaining the equivalent controller due to external disturbance and parameters uncertainties. The way is adopted to solve the chattering reduction problem commonly found in the sliding mode variable structure control: the switching controller is designed based on the control gain being adjusted online by a fuzzy system. The simulation results show that the controller can reduce chattering effectively, decrease steady-state error, and have good robust capability for parameters uncertainties.Hardware-in-loop simulation platform of oil film on hydrostatic pressure center frame is designed and set up. Based on rapid-prototyping and MATLAB RTWT technology, hardware-in-loop simulation model is built, and closed loop control of oil film thickness is realized. At hardware-in-loop simulation environment, hardware-in-loop simulation experiment of single channel oil film control strategy is performed. The experimental results show that two-level self-tuning fuzzy-PID compound controller and fuzzy-sliding-mode controller can improve system interference rejection, have the better speediness and stability and are satisfy with the design requirements. |
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