Research On New Steeing Laws Of Single Gimbal Control Moment Gvros

With the development of aerospace technology, high-resolution is the maintrend for earth imaging satellites, which could offer more information of the target.However, it often means much narrower view field when the resolution isheightened. On this condition, the earth imaging satellite must have the capability torotate quickly from one orientation to another, which requires the rapid rotationalmaneuverability of the satellite. The rapid rotational maneuverability will help thesatellite to increase the operational envelope, and collect more earth and spacescience data than before. This in practice means a direct increase in the commercialand scientific value of these satellites.The rapid rotational maneuverability often requires the attitude control system(ACS) to offer large enough torque for the satellite. Single Gimbal Control MomentGyros (SGCMG) is a kind of momentum exchange device for attitude control,which is of the torque amplification capability and could offer a higher level torquethan reaction wheels at the same size. Despite of the above advantages, SGCMGfaces serious singularity problem. The singularity refers to the gimbal anglescombination where the output torques form a plane, and thus the total SGCMGsystem loses the capability of3-axis attitude control, no matter how does theSGCMG system rotate. The existence of singularity poses a large obstacle for thedesign of steering law and the astronautical application of SGCMG. The task of SGCMG steering law is to compute the gimbal angle rates which could produce therequired attitude control torque at the same time avoid singular states.As a result, the priority of the ACS design for those space vehicles takingSGCMG as their attitude actuator is the design of the steering law which couldproduces precise required torque at the same time avoid singular states. Under thiscircumstance, this paper focuses on the design of the satisfactory steering law, andcompletes mainly the following work:Firstly, this paper has discussed the singularity principle, the classification anddistribution of the SGCMG singular surfaces. The torque-producing principle andtorque amplification principle are illustrated respectively in this paper. And also,angular momentum singular surfaces of pyramid configuration are given, and thegeometric characteristic of the singular surfaces are studied.Secondly, a kind of new singularity escape algorithm is developed. According tothe geometric relations of SGCMGs' output torque, an index is put forward toevaluate the capability of outputting required torque, and thus the optimal capabilityprinciple of output torque is done. And then, a new steering law, which couldn't onlyproduce the smallest torque error but also drive the SGCMGs to the bestconfiguration, is design based on the above principle. The gimbal lock phenomenonand the output torque error are analyzed respectively in singularity valuedecomposition theory. It suggests that the designed steering law exists no gimballock phenomenon, and that the torque error could be reduced obviously by properlyselecting the parameter of the steering law. The mathematic simulations based onMatlab/Simulink are conducted also, which suggests that the designed steering lawis of the smaller torque error and of the capability to avoid elliptic singular surfacein comparison with other classic steering law, and that the designed steering couldaccomplish well the3-axis large angle attitude maneuver mission.Finally, a method for quick non-singularity trajectory optimization of SGCMGsystem is brought forward. Taking into consideration the condition that the satellitesequipped with SGCMGs tend to fall into singularity states during large angle maneuvers, this paper puts forward a kind of trajectory optimization method basedon adaptive Gauss pseudospectral method. The method takes the large anglemaneuver problem as an optimization problem, which takes all constrains in practiceinto consideration, inclusive of SGCMG gimbal angles constrain, gimbal ratesconstrain, singularity index constrain, satellite attitude rates constrain, the initial andfinal state constrain and so on. And then, the optimal trajectory could be producedby virtual of adaptive Gauss pseudospectral method and sequential quadraticprogramming. In GPOPS environment, the method could produce the optimalsystem trajectory of a single large angle maneuver in25s, which is satisfied with allconstrains, and the precision is above10-3. And the method could produce theoptimal trajectory of four sequential large angle maneuver in143s. In comparisonwith the global steering law, the method in this paper is of speediness, high precisionand easy implementation.In the end, this paper summarizes the accomplished work and gives some advicefor the future study of SGCMG steering law.