Research On Large Space Cable-net Structure’s Dynamic Response And Vibration Control Based On Piezoelectric Actuators

Large space cable-net structures,recently widely used in signal transmission, earth observation, deep space exploration and so on because of its small size after folding,light weight and giant diameter after unfolding, have become the focus of space research all over the world.But the orbiting precision will be influenced for a long time once the cable-net structures get the space disturbance due to its high flexibility,low stiffness and small damping,so it is very important to make active control of vibration effectively.First, this paper adopts the force density method is to make shape finding for three-dimensional parabolic cable-net which has a given geometrical morphology, and calculates the equally distributed pretension of the cable-net which established through reposition balance method.The finite element electromechanical coupling dynamics equations of the piezoelectric intelligent cables are established based on the stress tension stiffening effect of the pretension cables and the equivalent "piezoelectric stack- Spring" mechanical model of the piezoelectric actuators.The optimal placement of the actuators and sensors for the active control of vibration in large space cable-net structures is then investigated. Starting with modeling of the cable-net structure on the basis of its reduced modal coordinates, the numbers of actuators and sensors placed in the same position is optimally determined via the rank of the energy auto-correlation matrix of modal control force. Subsequently, a hybrid optimization strategy for the actuator and sensor placement is proposed based on the minimization of the integral of total stored energy and the maximization of the signal energy received by the sensors,which is used by genetic algorithm that based on dictionary order permutation encoding to search the global optimal locations of the actuators and sensors. The feasibility and effectiveness of the proposed method are illustrated through a parabolic cable-net structure.After that,the LQG controller is designed based on the state space description of the cable net’s dynamic equation.And the generalized controlled object of the cable net structure with uncertain stiffness is also obtained. By seeking the closed loop system’s global optimal parameters of the weighting function with the float encoded genetic algorithm,the robust stability of the mixed H? sensitivity controller is analysised. Furthermore,with the same uncertain stiffness, ? synthetical controller with smaller conservatism is designed to get better robust stability and robust performance of the system.Finally the paper compares the control effect of three kinds of controllers, choosing the ? synthetical controller. In addition,Hankle norm approximation method is used to reduce the controller’s orders in order to simplify the design of the controller.This paper identifies the pretension force and the finite element dynamic model of the large space cable-net strutures,and the parameters of the weighting functions are optimized based on the optimal number and placement of the actuators and sensors.Furthermore,the active controllers which ensure the closed-loop system’s robust stability and robust performance are designed.