Attitude Maneuver Control Of Spacecraft Using Angular Momentum Exchange

With the development of the aerospace industry, space exploration mission hasbecome increasingly diverse, and higher request on the agility and stability of thespacecraft has been proposed. Various benefits can be achieved if the spacecraft canaccomplish attitude maneuver mission fast and precisely by adopting efficientattitude control scheme and control allocation algorithm. Specifically, it cansignificantly extend the observation scope of the spacecraft and realize tracking orrevisit mission of important target. Besides, it can also increase the return rate ofvaluable mission data by avoiding undesirable or unnecessary orientation. However,the existing studies usually design attitude control scheme and the controlallocation algorithm separately, and signify the stability, robustness or optimality inattitude control law design, whereas ignore the characteristics of the actuator. Onthe other hand, most of the literatures focus on the energy consumption or responsespeed in control allocation algorithm design without consideration of the controlmission requirements. Therefore, consider the spacecraft actuated by controlmoment gyroscopes (CMG) or flywheels, a serial of problems have beensystematically and deeply studied to achieve desirable attitude maneuverperformance. These problems include physical characteristics of the actuator,control allocation algorithms for fast attitude maneuver, attitude control strategy forspacecraft maneuver subject to various constraints. The main contents include thefollowing aspects:The torque amplification characteristics, singularity mechanism, singular pointtype and singular measure of the CMG are analyzed firstly. Then based on theinvestigation on the angular momentum envelope and singular points distribution ofthe pyramid CMG cluster, it is demonstrated that the major challenge of thesteering law design should be avoiding the internal impassable singular points.Besides, the torque allocation strategy for redundant flywheel array is alsodiscussed, and torque envelopes for some typical flywheel configurations usingenergy-optimal allocation strategy are generated.Control allocation algorithms for CMG cluster and flywheel array areproposed respectively to maximize the control capacity, so that to transfer itsangular momentum rapidly. On the one hand, aiming at reducing the angle betweenthe direction of desired torque and angular momentum of all CMGs, a novelsteering law, which has fast angular momentum exchange performance, is presented.Different from traditional steering law, this newly designed steering law does not rely on the singular measure of the CMG cluster and always consider the angularmomentum envelope as its goal, thus it can effectively avoid internal impassablesingularities. On the other hand, based on static optimization theory and geometricfeatures of flywheel torque envelope, two torque-optimal allocation strategies aredeveloped respectively for a four-flywheel and a multi-flywheel array, both of themcan output the maximum control torque along desired direction.Two attitude control strategies for spacecraft eigenaixs rotation maneuver arepresented. The first one is inspired by the time optimal solution of single-axisrotation. Its control torque is mainly determined by monitoring the rotation angleand angular rate of the spacecraft about eigenaxis, a compensation torque is addedto constrain the rotation axis to be the eigenaxis, so that to reduce the effect ofvarious uncertainties. The second one is a revised PID cascade-saturationquaternion feedback controller, in which a limit vector on attitude error is designedto guarantee eigenaixs rotation. Both of these two controllers are based on feedbacklinearized dynamic equation and can accommodate the limits from spacecraftangular rate, control torque as well as angular momentum of the actuators, and neartime optimal performance are expected.An autonomous attitude controller for spacecraft maneuver in the presence offorbidden attitude set is proposed by means of potential function method andbackstepping technique. In order to avoid the forbidden attitude set, the existenceconditions for the repulsive potential function (RPF) are exploited through theincorporation of the spacecraft motions, and a novel RPF is proposed according tothe distance with the forbidden attitude, then an autonomous attitude controller isderived. Meanwhile, solutions dealing with control saturation and local minima ofthe potential function are also provided.Control schemes for spacecraft actuated by actuators with physical orquantitative limits are proposed for attitude maneuver. First, a composite controlsteering logic, which switches between null motion and robust inverse steering law,is proposed for CMG with gimbal angle constraints, and a transform domain is alsodevised to eliminate chattering caused by switch. Both the direction of the nullmotion and the switch logic are determined based on the relationship between thecurrent gimbal angles and desired ones. Next, using potential function method, anunderactuated attitude controller for spacecraft actuated only by two arbitrarilyinstalled flywheels is proposed, and an arc tangent function is adopted to restrictthe magnitude of control torque. Accordingly, a control parameter adaptive methodis then developed to ensure the stability of the system. Finally, by theoreticallyanalyzing the characteristic of output torque, it is illustrated that two CMGs can produce continuous control torque along two directions related to their gimbal axes.Inspired by the Euler angles representation, a control strategy to fulfill attitudemaneuver mission by three successive rotations about these two axes is developed,and the computation methods and performance index for several feasible rotationangles are presented in what follows.The validity and practical application value are all verified through welldesigned numerical simulations.