Active Vibration Control Of Space Truss Structures Driven By Piezoelectric Stack Actuators

Large flexible space trusses have been widely used in aerospace engineering because of its high mission adaptability and reliability. With the development of science and technology, the spacecrafts and equipments demand more and more strict vibration environment. Space trusses have the characteristics of large size, light weight and small damping, and when they are disturbed in out space, low-frequency and large-amplitude vibration will easily be excited which is difficult to decay, and disturb the work of the spacecraft if not be controlled. The widespread use of piezoelectric materials in vibration control field and the development of modern control theory provide the theoretical basis for the active control of space trusses. In this thesis, the active vibration control of large flexible space trusses is investigated. Firstly, diagonal rectangle space trusses are taken as the research object which is the typical structure of space trusses. And a simple physical model is set up. On this basis, the electromechanical coupling dynamic model of space trusses which uses piezoelectric actuators is established by using finite element method. The natural frequency and modal vibration mode of space trusses is calculated by adopting the modal superposition method and mode truncation and is analyzed and compared with the results calculated by using ANSYS software. Secondly, an optimization guideline of the location of actuators and sensors based on the controllable and observable Gramian matrix is raised in consideration of the controllability and observability criterion, the energy criterion and the control efficiency. The location of actuators and sensors are optimized using genetic algorithm as the optimization algorithm. The difference of the dynamic characteristics of space truss is analyzed after applying the piezoelectric active bar. Finally, one feedback controller is designed based on linear quadratic optimal control theory, and simulations in transient excitation conditions are carried out by Simulink. Another vibration controller is designed base on mixed sensitivity H∞ robust control theory, and simulations in transient excitation, steady excitation and basic excitation conditions are also carried out by Simulink. Comparing and analyzing the vibration control effects of the two controlers, a conclusion is made on the advantages and disadvantages of the two control theory.