Study On Control Strategies Of Multi-Degree-of-Freedom Electro-Hydraulic Vibration And Loading Coupling System

Multi-degree-of-freedom electro-hydraulic vibration and loading coupling system combines multi-degree-of-freedom vibration system and multi-degree-of-freedom loading system to realize the coupling reappearance of vibration environment and loading environment,so as to adapt to the simulation requirements of the increasingly complex working environment of the controlled object.It is convenient to test the mechanical properties of the controlled object in the vibration and loading composite environment and has important research significance in the test of engineering key components and materials.As a kind of multi-degree-of-freedom redundant parallel driven system,the multi-degree-of-freedom electro-hydraulic vibration and loading coupling system has the strong coupling characteristic,where the mutual interference of various drive branch in the freedom space,the parameters uncertainty of electro-hydraulic servo system,dynamic characteristics inconsistencies of various electro-hydraulic servo drive system and coupling between vibration and loading all will affect the control accuracy of the coupling system.However,domestic and foreign researches on the related technologies of the system are not mature.Hence,supported by the National Natural Science Foundation of China “Research on coordination control of super-redundant electro-hydraulic system subject to vibration and force loading”,this dissertation conducts the theoretical and experimental researches on coupling control of the multi-degree-of-freedom electro-hydraulic vibration and loading coupling system.In order to provide important theoretical support and technical means for improving the coupling system control precision,the control strategy of the multi-degree-of-freedom electro-hydraulic vibration and loading coupling system is studied theoretically and experimentally,based on the theory of multi-degree-of-freedom parallel mechanism kinematics and dynamics modeling,decoupling of modal space and internal space,nonlinear control theory of electro-hydraulic servo system and so on.Firstly,the composition and working principle of the multi-degree-of-freedom electro-hydraulic vibration and loading coupling system are introduced,considering the characteristics of multi-degree-of-freedom redundant parallel mechanism and electro-hydraulic servo drive system,and the kinematics model of the coupling system and its electro-hydraulic drive system model are established.Then a degree-of-freedom control strategy suitable for multi-degree-of-freedom parallel drive mechanism and the classical control strategy suitable for vibration and loading control are introduced.Subsequently,a testbed for the multi-degree-of-freedom electrohydraulic vibration and loading coupling system is built to test and verify the kinematic control strategy,which provided a foundation for the subsequent research on the control strategy of the vibration and loading coupling system.Secondly,dynamic model of coupling system is established to research the coupling characteristics in the degrees-of-freedom space.Then the system modal space is constructed to convert a multi-input and multi-output system in the freedom space into a multi-group single-input and single-output system in the modal space.In order to reduce the internal force coupling by using the internal force feedback compensation controller,the internal force space equation of the multi-degreeof-freedom electro-hydraulic vibration loading coupling sytem is established to research the internal force coupling characteristics and its main influencing factors.A system decoupling control outer loop composed of modal decoupling and internal force compensation control is constructed,and a series of experiments are conducted on the testbed to validate the effectiveness of the proposed decoupling control strategies.Thirdly,on the basis of the decoupling control outer loop of the multi-degreeof-freedom electro-hydraulic vibration and loading testbed,a vibration control inner loop subjected to loading is constructed with consideration of the nonlinear characteristics of electro-hydraulic servo system and the influence of motion table subjected to loading in the process of vibration.An acceleration signal tracking differentiator,an extended state observer and a terminal sliding mode error feedback law are employed to construct an active disturbance rejection inner control loop.The experimental study of vibration control strategy is carried out with the multi-degree-of-freedom electro-hydraulic vibration and loading testbed,and the effectiveness of the vibration control strategy based on the active disturbance rejection control algorithm is verified by combining with the system decoupling control outer loop.Finally,a fuzzy adaptive terminal sliding mode loading controller is designed with consideration of the uncertain factors of electro-hydraulic servo drive system and the influence of vibration interference.And a variable gain state observer is established to observe the speed and pressure difference of the loading hydraulic cylinders in real time,so as to accurately reflect the real-time state of the loading subsystem.A loading control inner loop of the system is constructed by using the proposed loading control algorithm,and the loading control system of the multi-degree-of-freedom electro-hydraulic vibration and loading testbed is combined with the decoupling control outer loop of the system.The experimental study of loading control strategy is carried out with the electro-hydraulic vibration and loading testbed,and the effectiveness of the proposed loading control strategy is verified by combining with the system decoupling control outer loop.This dissertation has 68 figures,7 tables and 137 references.