| This paper first summarizes the research background, the present development trend andwide application in industry of the hydraulic motion control experiment station, which is thenecessary equipment used for teaching, science and research in the major engineering collegesand universities. Moreover, this paper describes development status of the hydraulic servocontrol technology, and the composition and characteristics of the hydraulic servo system.A hydraulic motion control bench, which is being used in our hydraulic laboratory hasbeen introduced; its completed test functions, the system components and working principle ofthe experimental bench have been described in detail. Aiming at the closed loop force controlsystem of servo proportional valve control asymmetric hydraulic cylinder, the hydraulicbench’s existing principle diagram is simplified.The computer control method adopted in this hydraulic bench is also described; in viewof design requirements for the bench, the method of selecting IPC (industrial PC), sensors anddata acquisition card is introduced. Meanwhile, the industrial programming software used forthis hydraulic bench is presented.Focuses are given to describe the closed loop force control system of the servoproportional valve control asymmetric hydraulic cylinder. It concludes the servo proportionalvalve is a second-order oscillation link by calculating the natural frequency of the hydrauliccylinder, and comparing with bandwidth of the servo proportional valve. AMEsim elementmodel has been set to the practical applied servo proportional valve on the basis. Through thesimulation calculation to the setup servo proportional valve model, as well as comparing theobtained data and curves and those of the actual servo proportional valve samples, the valvemodel is accurate. A hydraulic cylinder AMEsim component model is set up according to theactual sample parameters. AMEsim model of the closed loop force control system is given onelastic and inelastic load conditions, based on the basis of the valve and cylinder models beingbuilt.The closed loop force control system is a discrete one because the computer is a discretecontrol system. This paper focuses on the description of working principle, characteristics, theselection of sampling frequency of the discrete control system. Aiming at this computerdiscrete force control system, the influence of difference sampling time to the system is analyzed, parameters of the system components are set, system simulation is done; thesystem’s dynamic response curve is analyzed in two different load conditions, namely elasticand non-elastic load. In the actual working condition, the force sensors used in this bench havesome interference errors, the random signal model in the AMEsim software is used to simulateinterference signal, and analyze the impact of the signal on the two loading systems.The principle and composition of PID control is described; the system is added a PIDcontroller for correction; functions of the proportional link, integral link and differential linkhave been researched. More reasonable PID control parameters are obtained through severaltests, so that performances of the system have been greatly improved.The system’s mathematical model is established, and its transfer function is derived,open-loop Bode diagram is drawn through simulation, to analyze the stable performance of thesystem. By combing theory with practice, this paper provides a theoretical basis and referencefor the valve-controlled hydraulic cylinder vertical force loading system used in industry. |
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