Aeronautics and astronautics – Spacecraft – Attitude control
Patent
1989-07-14
1991-08-27
Focarino, Margaret A.
Aeronautics and astronautics
Spacecraft
Attitude control
244165, 244169, 244170, 244171, 364459, B64G 126, B64G 128/1/36, B64G 138
Patent
active
050427520
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the improvement of devices for the servo control and stabilization of bodies, which are free to move about axes of rotation, particularly aircraft and space vehicles which, due to rotation about one of their principal axes, the so-called spin axis or due to spin storage devices built in especially for this purpose, have an angular momentum or "spin" different from zero.
As is well known, the dynamic motion of bodies, which have a stored spin, follows the laws of gyroscopic theory. In bodies, which are free to move about their axes of rotation, such as aircraft and space vehicles, a stored spin causes, in particular, a strong coupling of the motion variables characterizing the rotary motion about the principal axes of the body orthogonal to the spin axis, such as torques, angular velocities and excursions.
If now such a freely movable body is to be oriented by means of a closed control loop from a starting attitude according to preset directions in space and is to be stabilized with respect to this angular position, the control laws, which are to accomplish this, must take these conditions more and more into consideration the smaller the control torque levels available for stabilization are in relation to the gyroscopic couplings. If discrete, for instance, pulse-shaped control actions are applied for reasons of saving energy, as is frequently the case if reaction jets are used in space vehicles, a frequently undesired nutation motion is excited instead of a processional motion as in the case of continuous control torques.
Additional problems arise with the reference or set value control and stabilization of such vehicles due to their large dimensions, their degree of slimness and/or their weight-saving construction due to the existence of weakly damped structure vibrations and the danger of exciting such vibrations by pulse-shaped control interventions.
Flexible bodies of the kind under consideration, which are free to move in space, especially satellites moving in orbits around the earth, consist in general of a spingenerating rotating part or a spin storage device with, in principle, an equivalent effect, such as a reaction flywheel, as well as a nonrotating part, such as a despun platform or the central body of the satellite itself. This nonrotating part is always to be oriented with one of its body axes, which is orthogonal to the spin axis, as accurately as possible towards the earth, because it is to maintain communications links, for instance, via transmitting and receiving devices, continuously between different points of the globe. If such a body moves on its orbit around the earth, the despun part carrying the payload must also rotate once per orbit about an axis pointing perpendicularly to the plane of the orbit. For this reason, such vehicles are also called "dual spinners".
It is seen from the conditions described that at least three different kinds of periodic, practically undamped oscillatory processes occur in such bodies. These processes must be controlled by the control system. They are the orbitinduced and earth orientation-induced motions of the vehicle's own angular momentum vector relative to a line normal to the orbit, the direction of which coincides with the angular momentum of the orbit and also determines the average orientation of the vehicle axis directed towards earth. This motion, period of oscillations (1/W.sub.o) of which is given by the orbit period is therefore also called orbit motion. Superimposed on the latter is the nutational motion, i.e., the motion of the body relative to its own spin axis direction, the period (1/W.sub.N) of which depends on the magnitude of the bias angular momentum and on the moments of inertia of the transverse axes of the body In addition, one or two groups of weakly damped vibrational processes occur, such as, for instance, structural vibrations, the influence and vibrational frequency of which depends on the geometric, mass and elasticity properties of the structural elements used, or motions of liquids, such as any
REFERENCES:
patent: 3624367 (1971-11-01), Hamilton
patent: 3866025 (1975-02-01), Cavanagh
patent: 4174819 (1979-11-01), Bruderle et al.
patent: 4272045 (1981-06-01), Phillips
patent: 4288051 (1981-09-01), Goschel
patent: 4294420 (1981-10-01), Broquet
patent: 4358076 (1982-11-01), Lange et al.
patent: 4424948 (1984-01-01), Muhlfelder et al.
patent: 4504912 (1985-03-01), Bruderle et al.
patent: 4521855 (1985-06-01), Lehner et al.
patent: 4537375 (1985-08-01), Chan
patent: 4567564 (1986-01-01), Bittner et al.
patent: 4591118 (1986-05-01), Chan
patent: 4599697 (1986-07-01), Chan et al.
patent: 4617634 (1986-10-01), Izumida et al.
patent: 4725024 (1988-02-01), Vorlicek
patent: 4758957 (1988-07-01), Hubert et al.
patent: 4848706 (1989-07-01), Garg et al.
Bittner, et al., "The attitude determination and Control Subsystem of the Intelsat V Spacecraft", 11/1977, Proceedings of AOCS Conference, 10/3-6/7 (ESA SP-128, 11/1977).
Bittner Helmut
Porte Francois
Surauer Michael
Focarino Margaret A.
Kannofsky James M.
Messerschmitt-Bolkow-Blohm GmbH
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