Research On Modeling And Active Vibration Control Of A Rotating Two-connected Flexible Beam

Some flexible structures like large span solar panels and giant antenna are normallyinstalled in modern spacecraft. Vibration will be easily excited when spacecraft slewing,docking or external disturbance excitation. In space environment, the vibration especiallylow-amplitude vibration will last for a long time and affect the stability and the pointingaccuracy of the system, even cause catastrophic loss. To cope with the vibration problem ofthe rigid-flexible coupling system like rotating manipulator, a rotating two-connected flexiblebeam system with harmonic gear reducer was built up to conduct the research on dynamicsmodeling and active vibration control experiments.Firstly, the dynamics model of the system is built. Based on Hamilton variation principle,a zero-order approximate dynamics model of the rotating two-connected flexible beam isderived by utilizing the incorporation of Hybrid Coordinate Method(HCM) and FiniteElement Analysis(FEA). When the servo motor completely stops, the boundary condition ofthe two-connected flexible beam is regarded as the cantilever condition. Four-noderectangular plate elements are adopted to analyze the model of the two-connected flexiblebeam by using the Finite Element Method(FEM). The model equation is converted intostandard discrete state space equation form. Besides, modal analysis using MATLABprogramming and ANSYS software is conducted respectively and compared. A metod basedon Singular Value Decomposition(SVD) was used for the optimal position placement ofpiezoelectric sensors and actuators.Secondly, considering the hysteresis, nonlinear and resonance phenomena caused by theharmonic gear reducer in the rotating two-connected flexible beam system, three kinds ofnonlinear control algorithm are designed, namely Fast Terminal Sliding Mode(FTSM)controller, Fuzzy Fast Terminal Sliding Mode(FFTSM) controller and adaptive RBF fuzzyneuro network controller. The method for eliminating chattering phenomenon has beendesigend for the sliding mode controllers, and theoretical analyses and stability analyses werecarried out.Finally, the experimental platform of rotating two-connected flexible beam is set up,using the AC servo motor and piezoelectric actuators. The active vibration controlexperiments of set-point and rotating process were conducted. The experimental resultsdemonstrate that the PD control algorithm can suppress the vibration effectively, but it haslittle effect to the low-amplitude vibration. Three nonlinear control algorithms can damp outthe vibration to zero quickly. Besides, the FTSM and FFTSM control algorithms willeliminate chattering phenomenon effectively, under the condition of guaranteeing the controlperformance. The online learning of adaptive RBF fuzzy neuro network controller improvesthe reliability and robustness. Besides, a constant current drive circuit was designed and usedto conduct the driving experiments of the shape memoriy alloy(SMA) wire.