Research On Attitude Control And Solar Array Vibration Suppression Of A Flexible Satellite

With the increasing complexity and diversity of modern space missions, higher per-formance is expected in attitude maneuver, tracking, and earth observation of the flexiblesatellite. This paper represents a research on large-angle attitude control and solar arrayvibration suppression of a flexible satellite.The kinematical equation in quaternion representation, combined with the dynam-ical equations, backs up the design of the entire system. Regarding the highly-coupleddynamical equations, the system is decoupled into two independent systems: the satel-lite attitude control system and the solar array vibration system. Then the controllers arecompleted for the two systems, respectively.The basic idea of variable structure control is adopted in the decouple procedure,in which the coupling components are treated as disturbance. A variable structure slid-ing mode controller is designed under the disturbance and external disturbance torques.However, the controller will induce chattering. Therefore, a modified controller with con-tinuous output is presented based on the former one. With the modified controller, thesystem will enter the quasi-sliding mode and finally converge within a layer. The relationbetween the thickness of the layer and the parameters of the controller is formulated inthe paper. By properly choosing the parameters, the performance index can be achievedwithout inducing chattering.The former two attitude controllers are designed under the assumption that the rota-tional inertia is exactly known and the external disturbance is bounded with a pre-knownupper bound. However, in practical flexible satellite systems, the accurate rotational iner-tia can’t be acquired, and the external disturbance is uncertain. Considering this, adaptivecontrol is integrated into the variable structure sliding mode controller to estimate the dis-turbance. Also, this controller doesn’t need the information of the satellite’s rotationalinertia. Furthermore, the actuator saturation and actuator fault are also taken into con-sideration: by modelling the saturation and fault, a fault-tolerant adaptive sliding modecontroller is designed to guarantee the system stability in emergence of actuator saturationand fault.For the vibration induced during and after attitude maneuver, a vibration suppressioncompensator is designed based on the decoupled solar array vibration system. By using PZT materials as sensors/acuators, a Positive Position Feedback (PPF) compensator iscompeted to increase dump ratio of the the solar array’s first four vibration modes.