Spacecraft
spatial attitude control, II M.V.Levsky Research In this paper within of the
statement, that is accepted and discussed early in chapters 1, 2
(M.V.Levsky. Spacecraft
spatial attitude control. Int. J. "APAAS", No.2(25),
v.12, 2007, 141-151), it is presented the subsequent solving of reorientation
problem. In the work it is obtained, that optimal control is determined in a
class of two-impulse controls and realizes motion of spacecraft consisting of three phases: a short-term increase of
angular rate with the maximal control moment, free motion with the zero control
moment and short-term braking with the maximal control moment. Requirements of
an optimality are responded for all three phases of control: the stage of free
rotation satisfies to a condition of an optimality since the propellant expense at him is absent; phases of acceleration
and braking also satisfy to criterion of an optimality since the minimal expenses of propellant
for acceleration and braking is determined only by size
of the added kinetic moment (which is determined by inertial characteristics of
a spacecraft, initial and final conditions and time of turn Т). Mathematical modeling has shown that the given
control with account the external disturbing moments is optimum also. Effective ways of
reorientation control of a spacecraft, invariant both to external disturbances and to parametrical indeterminacies
of motion model are submitted. Essential lack of known analytical solutions is
absence of numerical estimates of fuel economy at their realization in relation
to ways of control of spacecraft's spatial position used now. Mathematical simulation has allowed to receive values of propellant
economy at realization of the submitted laws of control of a spacecraft turn
such as orbital station. Quantitative ratings of profitability of the offered
ways of spacecraft reorientation have been received by statistical methods after numerical experiments using personal computer. The simulation model of spacecraft motion around
the center of mass, accepted for the research, differs
by the account of the significant gravitational and aerodynamic moments which
operate to a spacecraft. For practical application, important it is not so much
that the turn was optimal under the propellant expense, how much that new control allowed to receive
essential economy of propellant in comparison
with known types of control and besides could be simply enough realized by
existing onboard systems. The developed
control laws of spatial reorientation allow to decrease
an expense of fuel for a turn of existing spacecrafts from 25 to 40 percents. |
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