261:
374:. Consequently, the torques provided are very limited and only serve to accelerate or decelerate the change in a spacecraft's attitude by small amounts. Over time, active control can produce fast spinning even on Earth, but for accurate attitude control and stabilization the torques provided are often insufficient. To overcome this, magnetorquer are often combined with
274:
This is the most efficient solution. A conductive wire is wrapped around a ferromagnetic core which is magnetized when excited by the coil, thus generating a dipole considerably higher than the other solutions. However, the disadvantage is the presence of a residual magnetic dipole that remains even
229:
is based on the realization of a coil with a defined area and number of turns according to the required performances. However, there are different ways to obtain the coil; thus, depending on the construction strategy, it is possible to find three types of magnetorquer, apparently very different from
255:
of solar panels which generates the effect of the coil. This solution is the one with the least impact on the satellite as it is entirely contained within the solar panels. However, due to the physical limit in the board thickness and the presence of other circuits and electronic components, it is
296:
of the fields which can be generated; no matter how the external field and the craft are placed with respect to each other, approximately the same torque can always be generated simply by using different amounts of current on the three different coils.
407:
losses can also play a part. This means that the magnetorquer will have to be continuously operated, and at a power level which is enough to counter the resistive forces present. This is not always possible within the energy constraints of the vessel.
279:
in the magnetization curve of the core. It is therefore necessary to demagnetize the core with a proper demagnetizing procedure. Normally, the presence of the core (generally consisting of heavy metal) increases the mass of the
82:. The magnets themselves are mechanically anchored to the craft, so that any magnetic force they exert on the surrounding magnetic field will lead to a magnetic reverse force and result in mechanical torque about the vessel's
200:
426:, a second CubeSat released at the same time, via strong onboard magnets used for passive attitude control, after deploying on October 28, 2011. This is the first non-destructive latching of two satellites.
393:. It is also impossible to control attitude in all three axes even if the full three coils are used, because the torque can be generated only perpendicular to the Earth's magnetic field vector.
137:
284:
Typically three coils are used, although reduced configurations of two or even one magnet can suffice where full attitude control is not needed or external forces like asymmetric
304:
is passing through the coils and the spacecraft has not yet been stabilized in a fixed orientation with respect to the external field, the craft's spinning will continue.
381:
A broader disadvantage is the dependence on Earth's magnetic field strength, making this approach unsuitable for deep space missions, and also more suitable for
389:. The dependence on the highly variable intensity of Earth's magnetic field is problematic because then the attitude control problem becomes highly
164:
649:
517:
618:
540:
396:
Any spinning satellite made of a conductive material will lose rotational momentum in Earth's magnetic field due to generation of
659:
654:
435:
44:
474:
260:
103:
52:
292:. The three coil assembly usually takes the form of three perpendicular coils, because this setup equalizes the
347:
265:
613:
363:
252:
335:
load of the coils. In Earth orbit, sunlight is one such practically inexhaustible energy source, using
51:. The magnetorquer creates a magnetic dipole that interfaces with an ambient magnetic field, usually
48:
241:, a conductive wire wrapped around a non-conductive support anchored to the satellite. This kind of
571:
293:
276:
546:
554:
536:
83:
528:
423:
371:
308:
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72:
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375:
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are needed if large craft have to be turned quickly. This either necessitates a very high
499:
213:
the magnetic field vector (for a spacecraft it is the Earth magnetic field vector), and
386:
343:
328:
289:
285:
79:
268:
uses four 8 feet (2.4 m) iron torque rods as part of its pointing control system.
67:
Magnetorquers are sets of electromagnets arranged to yield a rotationally asymmetric (
643:
320:
550:
401:
397:
351:
336:
525:
Proceedings of the 1998 American
Control Conference. ACC (IEEE Cat. No.98CH36207)
245:
can provide a consistent magnetic dipole with an acceptable mass and encumbrance.
17:
155:
68:
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in its body and the corresponding braking force proportional to its spin rate.
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of the coil. The dipole interacts with the magnetic field generating a torque
324:
71:) magnetic field over an extended area. That field is controlled by switching
532:
390:
332:
40:
86:. This makes it possible to freely pivot the craft around in a known local
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in the coils, or much higher ambient flux densities than are available in
500:"Attitude and Determination Control Systems for the OUFTI nanosatellites"
404:
367:
87:
76:
415:
412:
319:
Magnetorquers are lightweight, reliable, and energy-efficient. Unlike
195:{\displaystyle {\boldsymbol {\tau }}=\mathbf {m} \times \mathbf {B} ,}
56:
456:
327:, so they could in theory work indefinitely as long as sufficient
259:
623:
419:
75:
flow through the coils on or off, usually under computerized
411:
The
Michigan Exploration Laboratory (MXL) suspects that the
256:
not possible to reach a high value of the magnetic dipole.
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The main disadvantage of magnetorquers is that very high
251:
This is constructed creating a spiral trace inside the
90:
of the magnetic field by only using electrical energy.
592:
518:"Satellite attitude control using only magnetorquers"
457:
Magnetic actuators for nanosatellite attitude control
167:
106:
55:, so that the counter-forces produced provide useful
194:
131:
595:. Michigan Exploration Laboratory. 2011-12-06
8:
132:{\displaystyle \mathbf {m} =nI\mathbf {A} ,}
275:when the coil is turned off because of the
230:each other but based on the same concept:
47:, detumbling, and stabilization built from
516:Ping Wang; et al. (21–26 June 1998).
354:, hence significantly higher reliability.
184:
176:
168:
166:
121:
107:
105:
447:
169:
498:Vincent Francois-Lavet (2010-05-31).
93:The magnetic dipole generated by the
7:
237:This comprises the basic concept of
146:is the number of turns of the wire,
438:, a passive stabilization technique
422:, became magnetically conjoined to
619:National Space Science Data Center
385:as opposed to higher ones such as
25:
593:"Michigan Exploration Laboratory"
527:. Vol. 1. pp. 222–226.
418:, a joint project run by MXL and
323:, they do not require expendable
475:"Observatory - Pointing Control"
217:is the generated torque vector.
185:
177:
122:
108:
209:is the magnetic dipole vector,
455:Niccolò Bellini (2014-09-10).
436:Gravity-gradient stabilization
307:Very small satellites may use
1:
150:is the current provided, and
97:is expressed by the formula
650:Spacecraft attitude control
676:
473:Garner, Rob (2017-12-19).
331:is available to match the
348:control moment gyroscopes
574:. Amsat.org. 2002-11-24
533:10.1109/ACC.1998.694663
364:magnetic flux densities
342:Another advantage over
269:
266:Hubble Space Telescope
225:The construction of a
196:
133:
660:Spacecraft components
655:Spacecraft propulsion
290:underactuated control
263:
234:Air-core magnetorquer
197:
134:
49:electromagnetic coils
165:
104:
63:Functional principle
311:instead of coils.
294:rotational symmetry
350:is the absence of
270:
192:
129:
309:permanent magnets
84:center of gravity
35:(also known as a
18:Magnetic torquers
16:(Redirected from
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604:
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553:. Archived from
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424:Explorer-1 Prime
383:low Earth orbits
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45:attitude control
33:magnetic torquer
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572:"Magnetorquers"
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376:reaction wheels
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344:momentum wheels
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11:
5:
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560:on 2011-08-21.
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387:geosynchronous
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398:eddy currents
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358:Disadvantages
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248:Embedded coil
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628:. Retrieved
626:. 2013-08-16
617:
608:
597:. Retrieved
587:
576:. Retrieved
566:
555:the original
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511:
493:
482:. Retrieved
478:
468:
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410:
395:
380:
361:
352:moving parts
341:
337:solar panels
318:
306:
299:
283:
243:magnetorquer
242:
239:magnetorquer
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227:magnetorquer
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221:Construction
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95:magnetorquer
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36:
32:
29:magnetorquer
28:
26:
402:Aerodynamic
372:Earth orbit
300:As long as
156:vector area
69:anisotropic
43:system for
644:Categories
630:2019-05-27
614:"MCubed-2"
599:2012-12-14
578:2010-02-08
484:2023-03-14
443:References
325:propellant
315:Advantages
277:hysteresis
271:Torque rod
37:torque rod
462:(Report).
391:nonlinear
333:resistive
321:thrusters
182:×
170:τ
41:satellite
551:64318808
430:See also
405:friction
88:gradient
77:feedback
416:CubeSat
413:M-Cubed
368:current
302:current
280:system.
154:is the
80:control
73:current
53:Earth's
39:) is a
549:
539:
288:allow
205:where
142:where
57:torque
558:(PDF)
547:S2CID
521:(PDF)
503:(PDF)
460:(pdf)
329:power
624:NASA
537:ISBN
479:NASA
346:and
286:drag
264:The
253:PCBs
529:doi
420:JPL
31:or
646::
622:.
616:.
545:.
535:.
523:.
477:.
378:.
339:.
59:.
27:A
633:.
602:.
581:.
531::
505:.
487:.
215:τ
211:B
207:m
190:,
186:B
178:m
174:=
152:A
148:I
144:n
127:,
123:A
119:I
116:n
113:=
109:m
20:)
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