Research On The High-Precision And Agile Attitude Control System For Micro-nano Satellite With Complex Structure

Nowadays,with the development of technology,micro-nano satellite has gradually undertaken more and more important scientific test tasks,and is developing towards the direction of large-scale and clustered constellation network.In order to carry more loads and improve orbital maneuverability,the application of new lightweight materials and liquid fuels makes the micro-nano satellite structure more complex.On the other hand,to meet the requirements of payload missions,satellites need to be able to maneuver quickly and track continuously with high accuracy.In addition,in order to ensure the successful completion of the payload mission and improve the in-orbit service life of the satellite,higher requirements are put forward for the reliability and lifetime of the satellite attitude control system.However,due to the structure and energy constraints of micro-nano satellite,the performance of the actuator of attitude control system is difficult to reach that of ordinary large satellite,which brings a lot of difficulties to the design of the attitude controller.Based on the actual requirements of complex micro-nano satellites with flexible attachments and liquid fuels,on the premise that the current technology level can be realized,this paper conducts in-depth research on the related algorithms of the high-precision agile attitude control system of complex micro-nano satellites through theoretical analysis and numerical simulation.The main contents of this paper are as follows:(1)Taking the complex structure observation platform of the micro-nano satellite as the background,considering the complexity of the flexible attachment structure,the modal equation of the flexible attachment is analyzed by using the mixed coordinate method,and Lagrange equation is applied,and the dynamic equation of the flexible attachment carried by the satellite is analyzed by using the momentum and moment of momentum theorem.Considering the influence of liquid sloshing on satellite attitude,the equivalent simple pendulum model was used to establish the attitude dynamics model of liquid sloshing.Combined with finite element analysis software ANSYS and multi-body dynamics analysis software ADAMS,the influence of satellite flexible modal characteristics was studied and analyzed.Combined with Matlab/Simulink simulation module and ADAMS built-in simulation module,the joint simulation platform of attitude measurement and control system was built.Combined with the fluid dynamics analysis software STAR CCM+,the influence of the liquid fuel sloshing on the satellite's attitude in the process of applying torque is analyzed,and the effectiveness of the equivalent pendulum model is verified.Finally,the modeling and analysis of the attitude dynamics of the complex structure with liquid sloshing and flexible vibration are carried out.Considering the influence of the time-delay on the precision of attitude control system,the time-delay characteristics in the satellite attitude control system are modeled and analyzed.(2)A high-precision attitude controller based on the ADRC algorithm was designed for the complicated structure micro-nano satellite,which effectively reduced the vibration of the flexible attachment and liquid fuel sloshing during the attitude adjustment process.Finally,the designed control law is simulated and verified,and compared with PD controller commonly used in engineering,the advantages of the designed control algorithm is verified.(3)An adaptive attitude maneuver algorithm based on path planning is designed considering the requirements of fast maneuver and continuous observation of the earth observation micro-nano satellite.Considering the influence of inertia estimation error,flexible vibration,liquid sloshing,space disturbance torque and internal time-delay during satellite maneuvering,a new attitude tracking controller based on feedforward and adaptive backstepping method is designed.Numerical simulation verifies the effectiveness of the proposed control algorithm.Finally,the effectiveness of the proposed maneuver and tracking control algorithm and strategy is further verified by building a hard-interface-loop simulation platform.(4)Considering the absence of actuator redundancy on micro-nano satellite,in order to improve the reliability of attitude control system under multi-type actuator faults,at the same time considering the flexible structure vibration,the liquid sloshing,the influence of external disturbance,based on the fault diagnosis and fault identification,the fault-tolerant control strategy is studied.Simulation results show that the control stategy can solve the problem of complex structure micro-nano satellite attitude control system under multi-type actuator failures,and satisfy the high reliability requirements of the complex structure micro-nano satellite.To sum up,taking the practical engineering application demand of earth observation micro-nano satellite with complex structure as the background,this paper deeply analyzes and discusses the satellite attitude control system theoretically,and fully verifies the effectiveness of research through numerical simulation,ground hard-interface-loop simulation and other simulation results.