Research On The Sun-pointing Attitude Control Of The Satellite With An Architecture Of Disturbance-free Payload

With the space observation missions more and more multiple and complicated and the development of space observation technique,solar observation has attracted widespread attention.The high precision solar observation is the basis of solar research for the mankind.So,the high precision satellite platform is needed.Although traditional isolation devices can isolate vibration to some extent,they can hardly eliminate the impact of vibration on payload because of the connection between the platform and the payload.Satellites with the architecture of Disturbance-free Payload(DFP)can insulate the payloads from the vibration of the platform,which lays the foundation of space observation with high precision and high stability.This paper mainly researches the sun-pointing maneuver based on the DFP satellite.The main research contents are as follows.To realize sun-pointing control,the reference coordinate system is established firstly.Both of the structure characteristics and work mechanism of DFP satellite are analyzed.Based on the different work modes of platform and payload,the active maneuver attitude model of payload and the attitude tracking model of platform are established.Then,the dynamic model of relative position is established according to orbital dynamics model.Besides,the mathematic model of relative motion between magnet steels and coils of maglev actuators is derived.Combined with payload attitude model,the six-DOF model is established.Three attitude control strategies and collision avoidance control mechanism for DFP satellite are proposed.The first one is based on the PD controller which realizes the high precision and high stability control and the collision can be avoided at the same time.To improve the dynamic properties of platform,the backstepping adaptive control strategy is proposed to compensate for the response lag of flywheels and the attitude tracking speed is increased effectively.The third one is inspired by the variable coefficient control method.A variable coefficient controller is proposed for the payload attitude maneuver which can improve the cooperative performance with platform.The system stability is analyzed through Lyapunov theory and the simulation is conducted.The direction deviation and amplitude saturation of maglev actuator output are considered.First,the real output force is discussed and the backstepping control strategy for payload is proposed.An adaptive method is developed to compensate for unknown actuator misalignment.To avoid maglev actuator saturation,an anti-windup controller and a disturbance observer is proposed based on the six-DOF model using hyperbolic tangent function.To improve the effect of control allocation,a new allocation strategy based on null space technique is presented.The control method is proved to be valid through mathematical simulation.