Research On Fast Maneuver And Stabilization Control For Agile Satellite

With the development of aerospace technology, satellites are required to possessagility in numbers of aerospace missions, such as long-time staring-imaging of aspecific ground target and stereo-imaging with single-line-array CCD camera. Theagility of satellites means that satellites are provided with the ability to accomplish theattitude maneuver rapidly, stabilize the attitude quickly and keep high stability duringfast attitude maneuver. The flying missions differ in the demand to agility of satellites.According to the aforementioned features, this dissertation deeply studies time-optimaltrajectory planning problem, hybrid control strategy with mixed thruster-flywheel andmixed CMG-flywheel, and control method for a flexible agile satellite. The researchcontents of this dissertation are presented as follows:Design of time-optimal attitude maneuver trajectory for agile satellites. Thetime-optimal trajectory is calculated based on collocation method, and properties ofsequential control switching for time-optimal attitude trajectory are obtained. Byignoring gyro torques, conditions which terminal angular velocity being zero requiresare derived, followed by proposing of the quasi-time-optimal attitude maneuvertrajectoy with high computing efficiency. And then a fast end correction method forterminal maneuver errors as a result of calculation inaccuracy is proposed. Finally,Learning Automata is utilized to tune the parameters of particle swarm algorithmwithout increasing computational cost and the accurate switching time is calculaterd bythe proposed method.Hybrid thrusters and reaction wheels control strategy. In order to solve the fastlarge-angle attitude maneuver and high-accuracy control problem for earth observationagile satellite flying mission, a control strategy by combining thrusters and flywheels isproposed. So as to compensate initial states errors and control torques inaccuracy ofthrusters, two kinds of attitude tracking control laws by utilizing variable structurecontrol and adaptive control theory are designed. Without reducing accuracy of attitudemaneuver control, a revising approach dealing with the saturate problem of flywheel’srotation and torques in attitude maneuver is proposed.Hybrid CMGs and reaction wheels control strategy. In view of the overactuatedproblem of combing CMGs and reaction wheels control strategy, based on generaldynamic model of variable speed CMGs, an optimization objective function related toCMG singularity index and energy-like rotation rate is designed, and then a controltorques distribution method based on constrained optimization method is proposed. Byadjusting weight parameters properly, the flywheel rotation rate saturation and CMGsingularity problems during the control process are solved. Since the installation error of CMG and flywheel could affect the control accuracy, a tracking control law based onMIMO adaptive control theory is proposed, and the updating of parameters will notcause the singularity of the tracking control law by using smooth projector principle.Research on fast maneuver and stabilization control method for agile flexiblesatellite. For the problem of fast maneuver and stability control of uniaxial agile flexiblesatellite, the combination control strategy based on input shaping and feedback controlis proposed. Considering that the modal variables of flexible appendages are hard to bemeasured and there always exists external disturbance torques, the controller which onlyuses the attitude information is designed. Moreover, according to the vibrationfrequency and the damping ratio of the closed-loop system, a feed-forward robustmulti-mode input shaping control approach is designed. For the problem of the fastmaneuver control of triaxial agile flexible satellite, a variable control method whichonly uses the attitude angle and attitude angular velocity is proposed, and the stability ofthe controller is proved by strict mathematical proof. The proposed variable controllercan drive the attitude state tracking error (including attitude tracking error and attitudeangular velocity tracking error) and the modal variables of flexible appendages from anarbitrary initial state to a neighborhood including the origin.