Research On Pump-valve Coordinated Electro-hydraulic Servo Control System For Snubbing Unit

Lifting system is the key part of the snubbing unit,which is usually drived by double hydraulic cylinders,and affects the performance of the unit by its stability and working precision.This paper focuses on the problems when pump-valve coordinated control system is applied on the snubbing unit.With the thought of pump-valve coordinated control,an electro-hydraulic servo system is designed to divide working mode into pump controlled mode and valve controlled mode.Pump controlled mode has high efficiency and occupy most time of the working process,while valve controlled mode has high precision and occupy a small part of the working time.According to the difference of system structure,different math models are established for pump controlled model and valve controlled mode.And the difference of transform functions is analyzed.In pump controlled model,only the single system is researched because the synchronization of the double system is determined by the flow divider-combiner.The PID controller and H-infinity controller are designed for the single system,according to the figures of fierce perturbation of key parameters.And the signal tracking performance of the controllers are simulated by Simulink.The simulation results show that compared to PID controller,H-infinity controller has great performance on single tracking and resisting parameters perturbation.In valve controlled model,the synchronization of the double system is determined by two servo valves.For single system,PID and H-infinity controllers are designed,and simulations are conducted to verify the validity of the controllers.For double system,three different synchronous circuits are designed to reduce the synchronous error.Then analyze and compare the advantages and disadvantages of the three control methods.Finally,based on xPC Target module of MATLAB and the available experiment equipment,a semi-physical simulation testbed is set up to test the real performance of the system in valve control model.According to the parameters of the testbed,new H-infinity and PID controllers are designed and the signal tracking performance is tested.Then testbed is used to get dynamic process and synchronous errors of three different synchronous circuits.The test results are mostly equal to the simulation results.