Development Of A Rotary Three-axis Loading Hydraulic Servo System

Rock in the deep formation is in multi fields environment that couple pressure field,temperature field,magnetic field,groundwater dynamic field and so on.In order to combine with the scanning equipment to realize the observation of occurrence and development of the inner crack of rock specimen and migration of the high pressure water in the gap,further obtain microscopic characteristics of the rock being fractured in the simulated underground environment,using rotary triaxial loading test system to realize multi fields coupling and research comprehensive mechanical properties of the rock is an effective method.The core of the rotary triaxial loading test system is the hydraulic servo loading system,which is used to complete static and dynamic loading of the force,displacement or deformation,and its performance directly determines the overall performance of the test system.The purpose of this subject is to design a set of the hydraulic servo system of rotary triaxial loading,these are put forward in the process of development:the rotary supporting mode of "thrust roller bearings +hydraulic cylinder supporting" that can achieve high precision rotation under large load,greatly reduce the friction torque,and reduce the control difficulty of the rotation and axial support force;The LVDT axial and radial deformation measuring device of rock specimen thatcan overcome the shortcomings of the resistance strain gauge and the extensometer eliminates the deformation caused by the axial system and the contact surface gap,and the measurement errors caused by the end effect,and improves centering installation error of the traditional radial deformation measurement,making the installation of the measuring device convenient,without considering the installation error;using iterative learning control to solve the nonlinear,strong cross coupling,complex and difficult modeling,high parameter uncertainty and the tracking control of high precision trajectory in hydraulic servo system,effectively ensuring the system's tracking error requirement and its static and dynamic performance,making the system have good rigidity and robustness;using AMESim and Simulink Co-Simulation effectively verifys the effectiveness of iterative learning control in the hydraulic servo system,closer to the actual working state of the system,which can give full play to the advantages of the two software and help to analyze the performance of the system.Through Co-Simulation,the design of the hydraulic servo system of rotary triaxial loading achieves the expected technical requirements,has good reliability and practicability,can meet a variety of loading test conditions.The research results of this paper provide important basis for the development of rotary mechanical machine for rock triaxial testing,and it also has important reference value for the application of iterative learning control in hydraulic servo system.