Disturbance Suppression And Vibrationisolation For Spacecraft Attitude Control

Nowadays the tasks which the spacecraft facing are more and more various, then the structure of the spacecraft is more and more complicated. The disturbance acting on the spacecraft is difficult to describe. Spacecraft need to maneuver quickly and keep high pointing accuracy in some situations. In other situations spacecraft need to track expected trajectory accurately.So it is necessary to design more advanced and practical controller which can reject disturbance for the attitude control of spacecraft. In view of the above issues, we made the following research.We make some research on the disturbance suppression of the flexible spacecraft attitude tracking. Considering the attitude kinematics model described by Euler angles we adopt trajectory linear control based on nonlinear disturbance observer. TLC can solve nonlinear tracking problems well and is practical in engineering, but it is limited in disturbance rejection. So we use disturbance observer to compensate. As there is singularity in Euler angle rotation, the following attitude control algorithms are based on quarternion. In order to improve the robustness of spacecraft attitude tracking, the robust sliding- mode control based on HJI theory is proposed. We define sliding mode as the evaluation function and choose L2 gain as performance indictor to show the antidisturbance ability of the system. Both theoretical analysis and simulation show the effectiveness of the controller. The precrding two algorithms use the equivalent disturbance idea and ignore the parameter uncertainties of rotational inertia. So we use addaptive technique to estimate uncertainties and design adaptive sliding- mode controller. The flexible spacecraft can reach expected tarjectory in the limited time and at the same time reject disturbance through the three different control algorithms.In addition, now that the pointing accuracy of sensitive payloadon spacecraft is more and more high. It is hard to meet the requirement only to control the attitude of spacecraft. It is necessary to take certain measures for the sensitive payload. Therefore, this paper also do some reserch on the vibration isolation problem of sensitive payload. We take the cubic stewart platform which is driven by voice coil moter as controlled object. First, the PD active vibration controller combined with the e xtended state observer is proposed. It turns out that it can vib rate the Sinusoidal disturbance in broad band as well as random noise compared to the passive vibration isolation. In order to further improve the vibration isolation performance, then the back-stepping slidingmode controller is designed. Compared to the PD active vibration, it performs better. Especially for the sinusoidal signal with high frequency and random noise.