FR2525361A1 - DEVICE FOR CONTROLLING ATTITUDE OF AN ARTIFICIAL TERRESTRIAL SATELLITE PROVIDED WITH A MAGNETIC MOMENT GENERATOR - Google Patents

Abstract

IN ADDITION TO A MAGNETIC MOMENT GENERATOR WHICH INTERACTS WITH THE EARTH MAGNETIC FIELD TO EXERCISE A ROTATION MOMENT ON THE SATELLITE, THE LATTER INCLUDES A CONTROL SWITCH CIRCUIT OF THE MAGNETIC MOMENT GENERATOR TO WHICH ARE DRIVEN, TO FORM A CONTROL SIGNAL THE POLARITY FOR THIS MAGNETIC MOMENT GENERATOR, A MAGNETIC MOMENT REGULATION SIGNAL AND A POLARITY SIGNAL OF THE EARTH MAGNETIC FIELD DELIVERED BY A CLOCK. ACCORDING TO THE INVENTION, A SMOOTHING ORGAN 4 OF THE CONTROL SIGNAL OF THE MAGNETIC MOMENT 5 IS INSERTED BETWEEN THE LATTER AND THE SWITCH CIRCUIT 3. THE VARIATIONS, OTHERWISE ABRUPT, OF THE MAGNETIC MOMENT CREATED BY THE GENERATOR WHEN THE POLARITY SIGNAL CHANGES ARE SO SMOOTH SO THAT THE ATTITUDE OF THE SATELLITE ADJUSTS WITHOUT DISTURBANCE.

Description

Attitude control device of an artificial terrestrial satellite

  The subject of the present invention is an attitude control device of an artificial terrestrial satellite comprising a magnetic moment generator which enters into controlled interaction with the earth's magnetic field, exerting a moment of rotation. on the satellite for the attitude control of the latter, and a switching circuit controlling said magnetic moment generator, to which a control signal according to the polarity for the magnetic moment generator is fed a control signal magnetic moment for example an attitude error signal, and a polarity signal delivered by a time indicator and indicating the polarity of the field

Earthly magnetic.

  With such a device, the attitude of a terrestrial satellite is regulated magnetically, by exerting on the satellite a moment of rotation which originates from the interaction between the earth's magnetic field and the

  magnetic moment generator of said satellite.

  A moment of rotation T on the satellite can be expressed by the vector equation

T = M B, (1)

  in which AI designates the magnetic moment vector created by the magnetic moment generator and B the intensity vector, or magnetic field induction, of the terrestrial magnetic field. The attitude regulation of the satellite can be exerted by the magnetic moment determined. in a suitable logic control unit O A magnetic attitude control device is known in which the magnetic moment is continuously regulated as a function of an attitude regulation signal. The direction and intensity of the terrestrial magnetic field by a magnetic feeler aboard the satellite but

  the use of such a probe makes this complicated system.

  To eliminate this drawback, it has been proposed an attitude control system in which only the polarity known by the shape of the terrestrial mnagnetic field along the satellite orbit is used. This system has the drawback that the moment magnetic generated

  3 by this polarity signal and an attenuation control signal

  studied in the form of a rectangular wave or a stepped curve, resulting in sudden jumps or variations in the moment of rotation when passing through another step, so that during this time corlmutation,

  the satellite is disturbed in -on attitude.

  The subject of the invention is a device for regulating the attitude of a satellite by means of a miagneti: read of the kind in question which is improved so that abrupt variations in the moment of rotation during the first phase are avoided in a simple way.

  switching the magnetic moment to prevent disturbances

  on the satellite; this device must also be

  established in a simple way without complicated parts.

  The device according to the invention is characterized by the fact that a smoothing element of the control signal of the magnetic moment generator is inserted between the circuit

  switch and said magnetic moment generator.

  Consequently, in the regulating device of

  At the study of a satellite according to the invention, one combines in a

  switch circuit a magnetic moment control signal

  for example, an attitude error signal derived from attitude probes, and a polarity signal delivered by a time indicator, for example a clock, and indicating the polarity of the terrestrial magnet-iqque field. a satellite location The output signal of this switch circuit is

  a control signal depending on the polarity for the gen-

  magnetic moment generator, but a linking loop is inserted between said circuit and the generator of the element, this device of smoothing, for example, was a first-order absorber. During the transition from a step to a magnetic moment, the control signal of the magnetic moment generator present at the output of the switching circuit is not altered. not abruptly, but is gradually brought to the value corresponding to the new switching step of the magnetic moment The satellite is thus brought slowly to its new attitude The smoothing circuit can be used not only in a regulation of attitude where one does not switches the magnetic field along the satellite orbit that all 900, but also in a system o the moment

  magnetic is switched as on a stepped curve.

  The attitude control device according to the invention is not complicated because it does not require a magnetic field probe itself The information on the magnetic field is calculated beforehand according to the known distribution of the Earth's magnetic field and the magnetic field. After the known orbit in the satellite The magnetic moment switching times are then given by a time indicator. The invention will be better understood using the

  detailed description of an embodiment taken as

  non-limiting example and illustrated schematically in the accompanying drawing, in which: Figure 1 is a block diagram of a portion of an attitude control device of a terrestrial satellite according to said invention; FIGS. 2a to 2d are time diagrams

  several signals given for explanatory purposes.

  According to FIG. 1, a magnetic moment regulation signal 1, for example an attitude error signal, is fed to a switching circuit 3 in which it combines with a polarity signal which is provided on its side by a time indicator, for example a clock 2, according to a determined polarity of the earth magnetic field The output signal of the switch circuit 3 is brought, as

  control signal, through a smoothing member 4 comprising

  a timer of the first order, to a coil (1

  magnet 5 which generates a corresponding magnetic moment, the coil 5 is placed, along the axis of the satellite around which we must correct the attitude thereof, in planes that enclose the axis of roll, pitch or laceto Gn has shown in Figure 2 several waveforms. The shape has shown the variation of the Earth's magnetic field during the revolution of the satellite in a direction by ra / port to the earth, that is to say along the satellite yaw axis * This variation is approximately sinusoidal along

  of the yaw axis interacts with the magnetic moment

  generated by the solenoid coil 5 and in turn generates a moment of rotation around the pitch axis of the satellite. The signal of polarity of the time indicator 2 is reproduced in FIG. the phase is shifted by 450 with respect to the signal of FIG. 2a. This rectangular signal determines the dependence of the polarity of the control signal of the magnetic moment generator. If the block diagram according to FIG. 1 does not include the smoothing member 4 the magnetic moment generator 5 would be controlled by a signal according to FIG. 2b, so that the magnetic moment signal would also have this rectangular shape, but because of the smoothing member, the magnetic moment takes a wavy form such that 2 is represented by the effect of the first-order timer which encloses the smoothing member 4, and the rise of the momet, agnetic take place according to a steeply steep curve; n On the contrary, it is progressively carried out at the maximum or minimum end values. This magnetic moment leads, in interaction with the earth's magnetic field of the wave form according to FIG. 2a, a smoothed moment of rotation corresponding to the waveform according to FIG. By the progressive transfer to the maximum of the moment of rotation and the progressive fall of the torque at its minimum,

  abrupt disturbances on the satellite are avoided.

  A regulation around other axes q ue that the pitch axis is of course also possible if one arranges differently the electromagnet coils con-me has indiniéu above The smoothing member 4 can in addition, it is also a higher order timer than the first order In this case, the invention provides a simple possibility to adjust with minimal disturbance the attitude of a terrestrial satellite

by magnetic means.

Claims (2)

  1 o An attitude control device of a terrestrial satellite comprising a magnetic moment generator which enters into controlled interaction with the terrestrial magnetic field while simultaneously exerting a moment of rotation on the satellite with a view to regulating the attitude of the latter and a switch circuit which controls said magnetic moment generator and to which a magnetic moment control signal, for example, is fed to form a polarity-dependent control signal for the magnetic moment generator; an attitude error signal, and a polarity signal provided by a time indicator and indicating the polarity of the earth's magnetic field, characterized in that a smoothing member for the signal   of the magnetic moment generator (3) is   wedged between the latter and the switch circuit (3).   2 o Device according to claim 1 characterized in that the smoothing member (4) is a timer first order.