Research On Attitude Control Of Agile Satellite Non-tracking Pushbroom Maneuvering

With the development of satellite remote sensing technology,the application in various fields has been very extensive,but in the specific working mode,because of the limitation on satellite attitude maneuver ability,there are only a few of options to complete the observation on the certain target.The target for emergency needs,such as disaster prevention,assessment and observation,has a very strong demand,these tasks are not to cover the area regularly according to the satellite orbit,but to cover the specific ground area.For certain objects,such as the need for highway,railway,river,the border,coastline,the image obtained by passively pushbroom along the satellite trace can not meet the requirement,it needs to adjust the direction of the payload optical axis,positively pushbroom image to complete the imaging task,namely non-tracking and positive pushbroom imaging,with the strong maneuvering ability of rapid response and non-tracking positive pushbroom imaging satellite was called agility satellite.Agile satellite has strong maneuvering ability,can improve the efficiency of the key observation observation area,improve mapping efficiency in the survey and detailed application,and It can also achieve rapid response to emergency,disaster and other applications.In order to achieve,it requires satellite maneuver control attitude with high precision in the process of imaging.This paper focuses on the research of novel high precision attitude pointing control for non-tracking and positive pushbroom imaging,the research is mainly divided into the following parts:Modeling for the agility satellite with positive pushbroom imaging.First of all,geocentric coordinate system,orbital coordinate system and satellite body coordinate system are described,euler angle,quaternion and the number of MRP and satellite attitude representation method is given.Then,based on the difficulty of modeling and controller,a satellite model based on quaternion is proposed.During the modeling process,various internal and external disturbances and uncertainties are taken into account,which makes the model more accurate in the dynamics of the actual satellite,and lays the foundation for the design of the controller in the next step.Research on attitude pointing maneuver technology of non-tracking and positive pushbroom imaging for agile satellite.This paper analyzes and studies the non-tracking and positive pushbroom imaging,and designs the attitude adjustment scheme for satellite imaging.First,an imaging mode is designed based on the analysis of the imaging process and mission mode.Then the effect of the drift angle is analyzed thoroughly,and the solution plan for the designed angular velocity is also presented.The effectiveness of the attitude adjustment technology of the smart satellite is proved by booth theoretical analysis and simulation results.The simulation results also demonstrate that the attitude adjustment plan presented in this section has good performance in the applications.Design of adaptive fuzzy variable structure controller.In positive pushbroom imaging mode,the satellite body needs strong attitude control capability.In this context,the variable structure finite time controller is designed when the satellite meets various uncertainties both inside and outside of the satellite,which can make the system reach the equilibrium point in a finite time.Meanwhile,the fuzzy algorithm is introduced to approximate the discontinuous terms in the variable structure controller,so as to reduce the intrinsic chattering of the controller.Designed of the finite time variable structure controller based on the Legendre neural network.In the finite time,the Legendre neural network is introduced into the variable structure controller to estimate the total disturbance of the system,so as to reduce the control gain and reduce the chattering.At the same time,in order to improve the stability of the system,the switching mechanism can be switched between the robust controller and main controller is designed,ensure the effect of the initial control system when the neural network estimation error is large,and the estimation error of Legendre neural network make effective correction.Through theoretical deduction and numerical simulation,it is shown that the finite time variable structure controller based on Legendre neural network can achieve finite time stability and basically eliminate chattering.In addition,by Legendre neural network is a single layer neural network,so the calculation efficiency of the controller is also guaranteed.Design of finite time control of satellite attitude based on hybrid actuators.Considering the disturbance of the output torque of an agile satellite attitude control system with external disturbances,a control strategy of the flywheel joint thrustor based on terminal sliding mode control theory is proposed.According to the singularity of terminal sliding mode control,a nonsingular controller is designed.By means of Lyapunov stability theorem,it is proved that the two controllers are all finite time convergent to zero,and the simulation experiment is done to prove the validity of the controllers.