JPS5817080B2 - Attitude acquisition method for three-axis control satellite - Google Patents

Description

[Detailed Description of the Invention] This invention provides a novel method for directing a three-axis controlled artificial satellite in the roll axis and orbital velocity direction when the satellite is separated from a rocket and switched from a stable spin state to three-axis control. It is.

Conventionally, three-axis control satellites have short-life, high-cost rate-integrating gyros installed in three axes, and the yaw axis, which is one of the reference axes of three-axis control satellites, is separated by an earth sensor (optical) mounted on the three-axis control satellite. earth acquisition (detecting the earth)
The roll axis (orbital velocity direction is the attitude that the roll axis of the three-axis controlled satellite should take) is determined from the output of the rate integral gyro attached to the other reference axes, the roll axis and the pitch axis. The angle formed by the orbital velocity direction is detected, and the satellite is then controlled to rotate around the yaw axis until the output of a rate-integrating gyro (yaw sensor) attached to the yaw axis matches the angle formed by the roll axis and the orbital velocity direction. By doing so, the transition to three-axis attitude control was achieved.

However, this method has the disadvantage that unless the yaw axis captures the earth, the rate integrating gyro for the roll and pitch axes cannot detect the angle formed by the orbital velocity direction and the roll axis, and the gyro for the gyro does not detect the angle between the orbital velocity direction and the roll axis. Because they are used in airplanes and airplanes, they have a short lifespan of about one year because they are transshipped on the ground, and when they fly in orbit for several years like artificial satellites, this poses a major development problem. The drawback is that the manufacturing cost is several dozen times higher than that of a solar sensor.

Separately, in a method that uses a sun sensor mounted on the roll axis of a three-axis control satellite to align the roll axis with the orbital speed direction, the sun sensor is fixedly mounted, so If the Sun-Earth center direction is included (this case is called a noon orbit in orbital mechanics) and the Sun-
Satellite - position where the earth angle is 90° (solar latitude ±2 per year)
Since it moves 3.5 degrees, it was limited to positions that matched it.

However, since it is extremely rare for an artificial satellite to maintain a noon orbit, this method is a solar sensor, which is cheap, and its deterioration characteristics in space are only about 1% per year. It had major drawbacks.

The disadvantage of the above is that the sun sensor is fixed on the roll axis, and the orbital velocity direction and the sun-earth direction change depending on the type of launch orbit and the position of the sun.In the present invention, the sun sensor on the roll axis The solar sensor is equipped with a function that can bias the sun position signal detected by the sun toward the orbital velocity direction by the angle formed by the orbital velocity direction and the sun-Earth direction.
By controlling the satellite's roll axis in the biased direction, it is possible to direct the roll axis in the orbital speed direction independently of the orbit, attitude, position of the sun, etc.

Ta.

Since the angle formed by the orbital velocity direction of the artificial satellite and the sun-earth direction can be easily calculated by calculating the orbit of the artificial satellite and the sun, it is possible to give commands to the artificial satellite regardless of whether it is before or after the satellite's launch. Notes installed.

It is also possible to record values corresponding to changes in the launch time of the artificial satellite in a recording device and automatically select values corresponding to the launch time on the satellite.

The present invention is applicable not only to cases where a solar sensor is mounted on a three-axis control satellite that flies around the earth, but also to cases where, for example, an earth sensor is mounted as a celestial body sensor on a satellite that orbits the moon.

As shown in Figure 1, the orbit of an artificial satellite has an inclination angle of 3 measured from the equatorial plane 1, an eccentricity representing the degree of distortion of the orbit, and an average height of 5 degrees from the earth 4. ing.

When switching the satellite to three-axis control (capturing the attitude), as shown in Figure 2, the yaw axis 6 (one of the three axes of the satellite) is set in the direction of the earth center 7, and the roll axis 8 is set in the direction of the satellite. An operation is performed to direct the orbital velocity direction 9 and the pitch axis J10 in a direction perpendicular to the yaw axis 6 and the roll axis 8, and this operation is called attitude capture.

When the roll axis 8 is directed in the orbital velocity direction 9, for example, when the yaw axis 6 is directed in the earth center direction 7;
As shown in the figure, since the orbital velocity direction 9 is controlled using the solar sensor 11 installed on the roll axis 8, the sun-satellite direction 12 and the orbital velocity direction 9 coincide, and the yaw axis 6 and Since the roll axes 8 are orthogonal, it is required that the angle 13 formed by the sun, the artificial satellite, the earth, and the center of the sphere be a right angle.

Here, even if the yaw axis 6 is not oriented toward the earth's center direction 7, first of all, the roll axis 8 is adjusted using the sun sensor 11 at a place where the sun-satellite direction 12 and the orbital velocity direction 9 coincide. As shown in Fig. 4, if the earth sensor 30 mounted separately is used to capture the earth at a point where the angle 29 formed by the orbital velocity direction 9 and the earth direction 7 is a right angle, the yaw axis Since the yaw axis 6 and the pitch axis 10 rotate around the roll axis by the angle θ14 formed between the yaw axis 6 and the center of the earth, the yaw axis 6 points toward the center of the earth and the pitch axis 10 also points in a predetermined direction.

The orbital velocity direction 9 differs at each position on the orbit 2, as shown in FIGS. 5 and 6.

Sun position 16 is based on sun position 17 at the autumn/vernal equinox,
When expressed as a change δ18 in the latitude direction and a change γ19 in the longitude direction centering on the earth, it becomes as shown in FIG.

Here, the sun moves ±23.5 degrees in the latitude direction 18 and 15 degrees per hour in the longitude direction 19 during the year.

(In cases other than sun-synchronous orbits, the angle between the orbital plane and the Sun-Earth center is not constant.

) Therefore, the angle 13 formed by the sun, the satellite, and the center of the earth is a right angle, and the orbital velocity direction 9 and the satellite-solar direction 1
For example, as shown in FIG.
2 and the earth center-sun direction 20 are parallel (local time 6
hour and 18:00), and the satellite reaches the sky above 1 degree north and south latitudes.

(At this time, there is an artificial satellite at the intersection 24 of the plane 23 perpendicular to the earth-center-sun direction 20 and the orbital plane 21 of Hekuei Noboru, and the earth-center-sun direction 20 and the artificial satellite-sun direction 12 can be ignored. Since the difference is only moderate, the sun-satellite-earth angle 1
3 is a right angle, and the orbital velocity direction 9 of the satellite and the satellite-sun direction 12 coincide) However, this condition is not generally satisfied.

In this invention, when switching the above-mentioned artificial satellite to three-axis control, as shown in FIG. The satellite's orbital velocity direction 9 (i.e., the tangential vector of the satellite's orbital plane 21) and the sun-earth center 20
The solar sensor mounted on the roll shaft 8 (generally The viewing angle is approximately 80° to 1,200 degrees, and within that field of view, the direction of sun incidence gives the maximum gain, so the longitude and latitude positions of the sun can be detected).
Next, the longitude angle α31 and the latitude angle β32 formed by the satellite-sun direction 12 (the sun is at infinity, so it is the same as the earth-sun direction) and the orbital velocity direction are used to calculate the orbit of the sun and the artificial satellite. The result is easily calculated, so from the direction 12 of the sun 16 detected by the sun sensor mounted on the roll axis, the roll axis 8 of the satellite is α31 in the longitude direction and β3 in the latitude direction.
If you turn it twice, the roll axis 8 will automatically match the orbital speed direction 9, so this launch.

In the light, it is assumed that the sun detection output of the sun sensor can be biased according to the angle formed between the orbital velocity direction 9 and the sun-earth direction.

The relationship between the satellite's orbit and the sun's position during launch is determined by the satellite's observation purpose, heat balance, power balance, and other conditions.

It depends on the time and generally, as shown in Fig. 11, the raceway surface 2
1 and the equatorial plane 1 and the sun 16 are spaced apart by α31 in the longitude direction and β32 in the latitude direction.

Here, α31 and β32 can be easily calculated by calculating the satellite's orbit and the sun's orbit (or they are already known at the time of the satellite's launch).

In this 5, the direction of the intersection line 22 between the orbital plane 21 and the equatorial plane 1 of the artificial satellite is the same as the orbital velocity direction at the intersection 34 between the orbital plane 21 and a plane 33 perpendicular to the intersection line 22 between the orbital plane and the equatorial plane. It is.

Therefore, on the orbital plane 21. When the sun position 16 detected by the sun sensor on the roll axis is biased in the longitude direction α31 and the latitude direction β32 at the intersection 34 of the roll axis to point the roll axis, the roll axis will be in the same direction as the intersection line 22 of the orbital planes. Therefore, the roll axis automatically points in the orbital velocity direction at the intersection point 34° on the orbital plane, and the transition to three-axis control of the satellite is achieved.

Surface 2 is obtained by further rotating surface 33 in the latitudinal direction by angle β32.
At the intersection 27 of the orbital plane 21 and the plane 26 obtained by rotating 5 in the longitude direction by an angle α31, the Sun-4 satellite-Earth angle becomes a right angle, and since the velocity direction of the orbit is the tangential direction of the orbit, the Earth -The direction of the satellite and the direction of its orbital velocity are at right angles,
Therefore, in FIG. 10, the angle formed by the yaw axis 6 pointing toward the center of the earth and the sun 16-satellite direction 12 is a right angle.
In addition, since the yaw axis 6 and the orbital velocity direction are at right angles, the orbital velocity direction 9 and the sun-satellite direction 6 (the sun 16 direction detected by the sun sensor on the satellite's roll axis) form a longitude angle α31 and are in the same plane. In this case, the sun detection output of the sun sensor is biased in the longitude direction, and around 6 around the yaw axis (
The transition to three-axis control of the satellite is completed by rotating the satellite in the direction of the longitude angle α31 and aligning the roll axis with the biased sun detection output.

If you spin the satellite around the yaw axis 6 in this step (generally in the earth capture state where the yaw axis 6 of the satellite points toward the center of the earth, the satellite will spin slowly at about 0.7°/sec). (This prevents sunlight from entering only one side of the satellite and disrupting the thermal balance) The sun 16 automatically enters the center of the field of view of the sun sensor on the roll axis, so the field of view of the sun sensor is narrow. The position of the sun can be easily detected even if a device is used (and the cost is low).

According to this invention, by using a solar sensor and calculating the relative positional relationship of an artificial satellite with the earth and the sun from orbit conditions, a three-axis attitude acquisition operation can be performed at any position on the satellite orbit and from any attitude. It is possible to achieve this.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the orbit of the artificial satellite, and Fig. 2 is an explanatory diagram showing the orbit of the artificial satellite, and Fig. 2 is related to three-axis control, and the relative attitude of the reference axes of the artificial satellite, yaw axis 6, roll axis 8, and pitch axis 10, with respect to the earth is captured. Figure 3 is a diagram showing the principle of roll axis capture, and Figure 4 shows the yaw axis 6 pointing toward the center of the earth 7.
This is a diagram showing the acquisition method when the orbital velocity direction 9 and the earth center direction 7 are at right angles.
When the earth is captured using the earth sensor 30, the yaw axis 6 and the pitch axis 10 rotate around the roll axis on a plane 15 perpendicular to the roll axis 8 by an angle 14 formed by the yaw axis 6 and the earth direction 7. and face the required direction. Figures 5 and 6 show that the latitudinal change in the orbital velocity direction is different at each point on the orbit 2 when the earth 4 is viewed from the equator 1 and the north pole, respectively. Explanatory diagram, Figure 7 is an explanatory diagram showing changes in the sun's latitude and longitude direction, Figure 8 is a configuration diagram showing autumn and spring equinoxes and transition to three-axis control, and Figure 9 is a configuration diagram of a variable bias device. , 10th
This figure is a block diagram showing an attitude acquisition method for a three-axis controlled satellite according to the present invention using the apparatus shown in FIG. 9, and FIG. 11 is a block diagram showing transition to three-axis control at an arbitrary position. 1 is the equatorial plane, 2 is the orbit, 3 is the orbital inclination, 4 is the earth, 6
is the yaw axis, 8 is the roll axis, 10 is the pitch axis, 11 is the sun sensor, 14 is the angle θ between the yaw axis and the earth direction, 15 is the plane perpendicular to the roll axis, 16 is the position of the sun, 17 is the autumn... The position of the sun at the vernal equinox, 18 is the latitude direction, 19 is the longitude direction, 2
1 is an orbital surface, and 25 is an attitude detection output.

Claims (1)

[Claims] 1. In the attitude acquisition method in which the satellite is separated from the rocket after launch and then transferred to three-axis control, when the three axes of the satellite are in a controllable state, the solar sensor mounted on the roll axis of the satellite When the relative attitude of the roll axis to the sun is detected and the satellite is shifted to three-axis control based on the attitude detection result, the satellite is In order to shift to three-axis control, a device is installed that can variably bias the output of the sun sensor according to the direction of the satellite's orbital velocity and the angle formed by the Earth-sun direction, and by using the biased solar sensor output. , an attitude acquisition method for a three-axis control satellite that directs the roll axis in the direction of the orbital velocity and shifts the satellite to three-axis control.