SPACECRAFT ADAPTIVE ATTITUDE CONTROL AND POWER TRACKING WITH SINGLE-GIMBALLED
VSCMGs AND WHEEL SPEED EQUALIZATION
A control law for an integrated power/attitude control system (IPACS) for
a satellite using variable speed single-gimbal control moment gyros (VSCMG)
is introduced. While the wheel spin rates of the conventional CMGs are
controlled to be constant, the rates of VSCMGs are allowed to have variable
speeds. Therefore, VSCMGs have extra degrees of freedom and can be used for
additional objectives such as energy storage as well as attitude control. In
this paper VSCMGs are used for an IPACS. The gimbal rates are used to
provide the reference-tracking torques, while the wheel accelerations are
used both for attitude reference tracking and power tracking. The latter
objective is achieved by storing or releasing the kinetic energy in the
wheels. The control algorithm performs both attitude and power tracking
goals simultaneously. A model-based control and an indirect adaptive control for a
spacecraft with uncertain inertia properties are developed. Moreover,
control laws for equalization of the wheel speeds are also proposed. Wheel
speed equalization minimizes the possibility of wheel speed saturation and avoids
zero-speed singularities.
Finally, a numerical example for a satellite in a low
Earth near-polar orbit is provided to test the proposed IPACS algorithm
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