GLOBALLY STABILIZING SATURATED ATTITUDE CONTROL IN THE PRESENCE OF BOUNDED UNKNOWN DISTURBANCES

摘要

In this paper a smooth attitude-stabilizing control law is derived on which known limits on the control authority of the system are rigorously enforced. Unknown disturbance torques, assumed to be of lesser magnitude than the control limits, are included in the formulation. Lyapunov analysis is employed to ensure global stability. A smooth control signal containing hyperbolic tangent functions is derived that drives the angular velocity to zero and diminishes attitude errors, expressed as Euler parameters, whenever certain design parameters are selected appropriately. These new results can be viewed as a smooth analog to a variable-structure scheme, in which the degree of sharpness of the control is permitted to vary with time as an "adaptive" parameter. The derived control law is independent of the inertia matrix and therefore robust to arbitrarily large inertia parameter uncertainties.