Step-by-step Loading Of Hydraulic Cylinders And Their Synchronous Control Research

The rocks in deep strata are in a complex and multiple-field coupling environment,and the permeability and mechanical properties of rocks are unknown under the action of temperature,pressure,magnetic field,gas-liquid and many other factors.Therefore,rock mechanics test machine is a main experimental equipment for studying the mechanical properties of rock in the universities and institutes.Only by simulating the state of underground environment more realistically can we understand the microscopic movement rules of rock underground.The true triaxial testing machine is a rock mechanics test machine which can carry out loading test in three directions of rock specimen.Its core part is the hydraulic servo loading system,which is used to test the stress,displacement and deformation of rock specimen.The hydraulic loading system is the key to determine the rock mechanics test directly.Based on the hydraulic loading system of the true triaxial rock mechanics test machine,a new hydraulic loading system is developed.In order to achieve the desired load control requirements,this paper presents a new design type of step by step loading hydraulic cylinder group model,which can provide more loading force under the condition of limited space and specimen size,and analyzes the influence of oil film thickness on the sealing of piston rod and guide belt based on hydrostatic support cylinder.According to the technical requirements of the new type of hydraulic cylinder,the selection and calculation of related hydraulic components are completed.By analyzing the model of position and force control of hydraulic servo loading system and the problems of nonlinearity,modeling difficulty,strong cross coupling,parameter uncertainty and high accuracy synchronous tracking of hydraulic servo system,the iterative learning control method is chosen.It can effectively solve the system's synchronous tracking error problem,and can maintain good stability and robustness.By using the powerful simulation modeling ability of AMESim and Simulink software,the whole physical model of hydraulic servo loading system and the Simulink control model based on iterative learning are constructed,and the working state of the system is simulated more realistically.Through the combined simulation and verification of two software,the hydraulic loading system can meet the predetermined technical requirements under the control of iterative learning,the algorithm is simple and has good reliability and practicability.For the hydraulic servo loading system,a variety of loading waveform test,it can achieve a good synchronization tracking error requirements.By comparing and analyzing the test results of the prototype,the good control effect of the hydraulic loading system is validated.The research results of this paper provide an important design foundation for the development of the true triaxial rock mechanics test machine,and also have certain reference value for the application of iterative learning control in hydraulic servo system.