Research On Vibration Control Of The Large Flexible Space Truss Based On Fuzzy Logic

With the development of astronautics, Large Flexible Space Trusses (LFST) have been widely used in space structures. When these trusses are disturbed, low frequency, wide range and persistent vibration will happen. In order to ensure the spacecrafts working naturally, the vibration of these trusses must be well controlled. Thus, research on the vibration control of LFST is an important subject. Unfortunately, because of the complex structure, the space trusses have many characters such as non-linear and time variable peculiarities. Thus, it is difficult to build the accurate model. Also the conventional control theory based on accurate model is faced with challenge. However, fuzzy control theory doesn't depend on the accurate mathematical model and it is suitable to the vibration control of the space truss. From this point of view, the dynamics of LFST was studied in this thesis and two schemes of active fuzzy vibration control for LFST were brought forward. The main studies included in this thesis are as follows:1. In view of the mast truss structures, two simplified models were given. Then the dynamic models for two simplified models were set up and the dynamic parameters were obtained via the linear and non-linear finite element methods.2. Based on the modeling of the piezoelectric actuators and sensors, the theoretical vibration equations of space intelligent truss were presented. The best location of the piezoelectric actuators and sensors were determined with the efficiency of actuating and the observation precision of mode displacement. On the basis of these rules, the location of piezoelectric actuators and sensors were optimized using genetic algorithms.3. The local vibration control method based on simple fuzzy controller was presented. Firstly, a standard fuzzy logic controller was designed to avoid the complexity in designing a MIMO fuzzy logic controller. It can be used for every actuator/sensor pairs by selecting appropriate scaling factors. Every controller works independently. Finally, the simulation of fuzzy control to a space intelligent truss was performed. The simulation results show us that the fuzzy logic controller designed in this thesis can successfully suppress the vibration of the truss. The controller is also of many advantages such as simple structure, strong robustness.4. The independent modal space control (IMSC) method based on adaptive fuzzy controller was presented. Firstly, the vibration control equations of space intelligent truss were given in modal space. The effect of remnant modes has been considered in the equations. Then an adaptive fuzzy controller was improved and the proof of its stabilization was also been given. Finally, the simulation of vibration control of a space intelligent truss based on adaptive fuzzy controller was studied. Results show that the controller designed in this thesis works better in suppressing the vibration of the truss than oher simple fuzzy controllers. The controller designed here can suppress the control spillover and observation spillover effectively.