Spacecraft Attitude and Power Control Using Variable Speed Control Moment Gyros
A Variable Speed Control Moment Gyro (VSCMG) is a recently
introduced actuator for spacecraft attitude control.
As its name implies, a VSCMG is essentially a single-gimbal
control moment gyro (CMG) with a flywheel allowed to have variable spin
speed. Thanks to its extra degrees of freedom, a
VSCMGs cluster can be used to achieve additional objectives, such
as power tracking and/or singularity avoidance, as well as
In this thesis, control laws for an integrated power/attitude
control system (IPACS) for a satellite using VSCMGs are
The power tracking objective is achieved by storing or releasing the kinetic energy
in the wheels. The proposed control algorithms perform both the attitude
and power tracking goals simultaneously.
This thesis also provides a singularity analysis and avoidance method using
CMGs/VSCMGs. This issue is studied for both the cases of attitude tracking with and without a power
tracking requirement. A null motion method to avoid singularities is
presented, and a criterion is developed to determine the momentum region
over which this method will successfully avoid singularities.
The spacecraft angular velocity and attitude control problem using a single
VSCMG is also addressed.
A body-fixed axis is chosen to
be perpendicular to the gimbal axis, and it is controlled to aim at an arbitrarily given inertial direction,
while the spacecraft angular velocity is stabilized.
Finally, an adaptive control algorithm for the spacecraft attitude tracking in case
when the actuator parameters, for instance the spin axis directions, are uncertain is developed.
The equations of motion in this case
are fully nonlinear and represent a Multi-Input-Multi-Output (MIMO) system.
The smooth projection algorithm is applied to keep the parameter estimates inside
a singularity-free region.
The design procedure can also be easily applied to general MIMO dynamical systems.
Advisor:Tsiotras, Panagiotis; Taylor, David G.; Johnson, Eric N.; Braun, Robert; Prasad, J. V. R.
School:Georgia Institute of Technology
School Location:USA - Georgia
Source Type:Master's Thesis
Date of Publication:11/21/2004