Space Telescope Distributed Piezoelectric Vibration Suppression Technology Research

As human accelerates the space exploration, image stabilization accuracy require-ments of space telescope are becoming higher and higher. Since space exists a variety of complex factors, it’s difficult to realize high accuracy image stabilization for space telescope. Among these factors, vibration has the largest influence on image stabiliza-tion accuracy. In order to improve image stabilization accuracy, it’s necessary to reduce vibration for space telescope. For the vibration of space telescope, vibration isolation is mainly used for Hubble telescope and JWST telescope abroad. However, due to the limited isolation performance of vibration isolator, it has almost no effect for low frequency vibration. Therefore, in order to improve the image stabilization accuracy, it’s necessary to take into account the active vibration technology. In addition, active vibration control technology has been used in the next generation space telescope AT-LAST for NASA. Thus, aiming at space telescope truss, this paper will use distributed piezoelectric active vibration control technology for it.Firstly this paper designs the structure of supporting frame for space telescope and gives the node and element numbers. According to the knowledge of finite element, overall stiffness matrix, mass matrix and force vector are listed. Moreover, in order to eliminate the singularity of stiffness matrix, it’s necessary to add boundary constraint conditions. In order to reduce the system’s order, modal truncation method is applied to establish the modal dynamic equation. This can lay the foundation for simulation analysis.For space telescope truss, study the time domain response characteristic with im-pulse excitation, step excitation and harmonic excitation and derive the time domain response expression and frequency response functions. At the same time, programmed in MATLAB to realize the time domain and frequency domain responses and the any position’s displacement between two nodes can be computed through shape function. The positions of piezoelectric patches surface mounted on the beam are optimized by modal strain energy and the maximum amplitude.In order to establish a simple and accurate model, according to the dynamic equa-tion of space telescope support frame, its characteristic model is derived. Because of the importance of characteristic parameters, study the characteristics of characteristic parameters which can determine the initial values of characteristic parameters. Af- ter studying several common parameter identification methods, improved more infor-mation extended filter stochastic gradient method is applied to estimate characteristic parameters. Simulation results illustrate the accuracy of characteristic model and the effectiveness of more information extended filter stochastic gradient method.On the basis of characteristic model, how to design a controller with simple struc-ture, good tracking performance and strong robustness is especially important. Firstly design characteristic model-based intelligent adaptive controller. In addition, in order to reduce the complexity of adjusting parameter, generalized minimum variance is ap-plied to optimize the control parameters. Secondly, considering uncertain disturbances in the space environment, it is necessary to design characteristic model based sliding mode adaptive controller. This paper designs two kinds of sliding mode control from reaching law. Besides, use Han function to replace sign function which can reduce the chattering. Control simulation results demonstrate the effectiveness of the three controllers and their difficulty of adjusting parameters and robustness.Lastly, distributed piezoelectric vibration control experiment will be done on the space supporting frame platform. Experiment results show that piezoelectric has good performance of suppressing vibration for the space supporting frame platform with large rigidity. Thus, a certain number of piezoelectric patches can be pasted on the surface of the area where space frame connects to the telescope sensing devices. In addition, this will realize the vibration reduction in the local area. Furthermore, image stabilization accuracy of space telescope will be improved.