AAS 98-140

FEEDBACK CONTROL LAW FOR VARIABLE SPEED CONTROL MOMENT GYROS

H. Schaub, S. R. Vadali, J. L. Junkins - Texas A&M University

Abstract

Variable speed control moment gyroscopes are currently being considered to control spacecraft attitude. They combine the features of the classical reaction wheels and control moment gyroscopes. They can also be thought of as reaction wheels on single-axis gimbals. We present the equations of motion of a generic rigid body with several such gimbaled reaction wheels attached. The formulation is such that it can easily accommodate the classical cases of having either control moment gyros or reaction wheels to control spacecraft attitude. A globally asymptotically stabilizing nonlinear feedback control law is presented. For a redundant control system, a weighted minimum norm inverse will be used to determine the actual control vector. This weighted approach allows the variable speed control moment gyroscopes to behave more like classical reaction wheels or control moment gyroscopes depending on what the systems calls for.

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