JPS5822799A - Control system for mass characteristic of artificial satellite - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This invention is based on the gravitational gradient torque (non-uniformity of the gravitational field) that a three-axis attitude control satellite (hereinafter referred to as a three-axis satellite) receives from a celestial body when it flies. This invention relates to a control method for the mass characteristics of a three-axis satellite to remove attitude disturbances caused by

When an artificial satellite flies, the celestial body is treated as a mass point in terms of kinematics. However, the mass and characteristics of each celestial body, including the earth, are not homogeneous and uniform, but have various distribution characteristics, and their levels also vary, resulting in variations in gravitational force (gravitational force). Therefore, when an artificial satellite flies around a celestial body, the mass characteristics of the 9 artificial satellite as a single celestial body (the unevenness of the mass of each device mounted on the satellite).

Due to the difference in the gravitational force between the celestial body and the satellite (the position and mass of the parts), the effect of variations in the gravitational force between the celestial body and the satellite occurs, which is manifested as disturbance torque on the X-axis, Y-axis, and X-axis of the satellite, and is called gravitational force. Generates tilt torque. The mass properties of celestial bodies and artificial satellites are expressed in terms of kinematics as the inertia factor as a characteristic around each axis (X-axis, Y-axis, and generates various movements as disturbances acting on these mass characteristics, and in the case of a satellite that always maintains a three-axis attitude relative to the celestial body, such as a three-axis satellite, conventionally many controls are required for attitude control. This caused the load and the difficulty of its control.

In addition, not only in the case of an artificial satellite that orbits a single celestial body, but especially in the case of an artificial satellite that observes the orbit of multiple celestial bodies such as in deep space, the mass characteristics of each celestial body are different, so conventional satellites When designing gravitational gradient torque control for one celestial body, as in In addition to the fuel consumed for orbit correction, the weight of observation equipment mounted on a single satellite is limited, observation items are limited, observation costs are relatively high, and launch rockets are also large. This resulted in a disadvantage.

-This invention was made to improve these points, and the mass characteristics of a three-axis satellite can be changed by moving the mass in each direction of the ±X axis, ±Y axis, and ±2 axes. Instead of moving the equipment mounted on the three-axis satellite, a substitute mass as a balancer is mounted so that it can be moved in each axis direction, so that the mass characteristics of the three-axis satellite can be varied, and the mass characteristics of the three-axis satellite can be varied. The gravitational gradient torque, which is the attitude disturbance that occurs in By changing , it is possible to minimize the gravitational gradient torque that is generated as an integrated value each time the aircraft flies near each celestial body.

If the drive for moving the balancer's axes is performed manually, the rate of change in attitude is monitored on the ground and compared with the attitude of each axis that the three-axis satellite should maintain, and the gravitational tilt torque acting on each axis is determined. Calculate the amount of movement of the balancer in each axis direction to minimize the mass characteristics of the triaxial satellite and the mass characteristics of the celestial body, ffcN, so as to minimize (cancel out) the attitude disturbance caused by this gravitational gradient torque. A command is sent from the ground station to move the balancer and control the mass characteristics of the three-axis satellite.If the drive for moving the axis of the balancer is automatically performed on the satellite, the attitude sensor (optical It detects celestial bodies and detects the relative attitude with the celestial body.Also, by attaching a differential circuit to the attitude sensor, it detects the hourly differential, that is, the rate of change in attitude) or a gyro (X-axis, Y-axis of a three-axis satellite) , which is attached to the The attitude disturbance around each axis, that is, the gravitational inclination torque, is detected by comparing it with the attitude that the satellite should maintain.Since the mass characteristics of the three-axis satellite are known before launch, the previously detected gravitational inclination torque is used as the three-axis The quality of a three-axis satellite that detects the mass characteristics of a celestial object by dividing it by the mass characteristics of the satellite, and minimizes the integration with respect to the mass characteristics of the detected celestial object! The movement values of the balancer in each axis direction that give the characteristics are calculated backwards, and the balancer driving device is operated in accordance with the movement values.

In this way, when controlling the mass characteristics on a king-axis control star, the processing function of the attitude control device installed on a three-axis satellite becomes important, but when configuring the attitude control system with the current analog control circuit, However, the functions of comparison, subtraction, and division can be easily realized by a signal matrix circuit having functions such as comparators and inverters, which are generally used in three-axis satellites.

Moreover, if the on-board computers that are recently installed on three-axis satellites are used, it will be easier to realize this because they have the computing power. As a result, it becomes possible to cancel out the gravitational inclination torque as an attitude disturbance due to the non-uniformity of the mass properties of celestial bodies in orbit, and even when flying around two or more celestial bodies, the gravitational inclination torque exerted by the celestial bodies on the three-axis satellite can be canceled out. It provides a method that can offset the effects regardless of the level and type.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of the mass characteristics of a celestial body. In FIG. 1, (a) is a fan-like distribution, (b) is a band-like distribution, and (c) is a basal eye-like distribution. Celestial bodies have mass inconsistency in their composition, and this is the result.

The gravitational force acting on a satellite is also uneven, and this unevenness causes disturbances to its attitude and orbit. In the case of zonal distribution (a), the mass distribution differs depending on the zone in the meridian direction of the celestial body, so if the celestial body is, for example, an artificial satellite whose orbit and rotation period are synchronized, the orbit or rotation period of the celestial body is synchronized. Since the satellite flies over zones with different mass distributions every few orbits, the disturbances that affect the satellite's attitude change sinusoidally over one or several orbits. In the case of zonal distribution (b), the mass distribution of the celestial body differs depending on the zone on the latitude line, so when the satellite flies around the celestial body at a constant speed, the disturbance that affects the satellite's attitude will be equal to the amount per revolution. Among them, the fluctuations are sinusoidal on the order of several cycles, and in cases such as the base pattern distribution () and ), when the orbit-circulation and rotation periods are synchronized, the disturbance is less than 9 artificial satellites, and the disturbance is 4. A sinusoidal fluctuation that changes cyclically on the order of a fraction of a revolution is replaced by a cosine wave fluctuation in cycles every one or several revolutions. Therefore, fan-shaped distribution (a), zonal distribution (
(b), When flying a satellite around celestial bodies with different single or composite mass property distributions (c), the mass property distribution of the celestial bodies remains unchanged, so the mass properties of the satellite are The gravitational gradient torque generated as a product of the nonuniformity of the mass properties of the celestial body and the artificial satellite is minimized by adjusting the product with the mass property distribution of the celestial body and the artificial satellite.

FIG. 2 is a diagram showing an embodiment of the present invention.

In Figure 2, the older brother is the earth, (1) is the three-axis satellite, (2) is the observation equipment, (31 is the direction of orbit, (41ki Z-axis balancer 5) is the -2-axis balancer, and (6) is the -2-axis balancer. X-axis balancer.

(7) is a -X axis balancer, (8) is a Y axis balancer, (9
) is the −Y-axis balancer. In order to observe the Earth E, the three-axis satellite (1) points the observation instrument (2) toward the Earth E, and aligns the X-axis equipped with the X-axis balancer [6] with the direction of the orbit. z with 2-axis balancer (4) installed
It flies by rotating around its axis to prevent imaging pre-occurrence.

Here, the element that causes the triaxial satellite (1) to undergo attitude disturbance from the earth E is the mass characteristic of the triaxial satellite (1), and the mass characteristic is ±X
Since the change occurs when the mass is moved in each direction of the axis, ±Y axis, and ±2 axis, detect one, two, or three axes where the rate of change in posture is greater than the value that should be maintained, and adjust the movement around that axis. By moving the acting mass (mass on two other axes perpendicular to that axis), posture movement around that axis, that is, posture disturbance, can be suppressed.

Therefore, for example, when the posture disturbance around the When the disturbance is large, use the X-axis balancer (6).

-X-axis balancer (7), Z-axis balancer +41, -
When the Z-axis balancer (5) is moved, the attitude disturbances acting on the three-axis satellite (1) around the Y-axis and around the Y-axis are suppressed. Here, the amount of control of the movement of the balancer that moves on each axis is determined by the mass properties around one, two, or three axes that are to be changed, and the amount of mass property adjustment is the product of the balancer's mass and the amount of movement. . Since the mass of the balancer is known in advance, it can be obtained by dividing the mass characteristic adjustment amount by the mass of the balancer.

FIG. 3 is a diagram showing an embodiment of the apparatus of the present invention, and in FIG. 3, +41, (51, +61, (])
, (81 is a balancer mounted in the ±2-axis, ±X-axis, and ±Y-axis directions, aO is a communication device, u is a balancer drive device, a2 is an attitude sensor, 0 is a gyro, a4 is an attitude control device, When controlling the mass characteristics (mass distribution) of a three-axis satellite in orbit manually, the rate of attitude change of the three-axis satellite is monitored at a ground station and compared with the attitude that the three-axis satellite should maintain. Detect the gravitational gradient torque acting on the satellite, calculate the mass characteristic of the satellite that minimizes the integration with the independent mass characteristics of the celestial body (Earth), and calculate the difference between it and the mass characteristic of the satellite at the time of launch. Soil two axes corresponding to the difference in mass properties, ±
Balancers installed in the X-axis and ±Y-axis directions +4) , +
A command is sent from the ground station to find the movement amount of 5+, +6+, (7), +8), +91. The communication device a of the three-axis satellite transmits the received command to the balancer drive device 0υ, and on the balancer drive device side, the balancer (41, (51, +61, (71, (81)
, (91) is moved as much as possible to control the mass characteristics in orbit. When controlling the mass characteristics automatically on a three-axis satellite, the attitude sensor (1) mounted on the three-axis satellite
2 or the attitude change rate data detected by gyro a3 is input to the attitude control system a4 mounted on the three-axis satellite, and compared with the attitude that the three-axis satellite should maintain, the attitude disturbance around each axis, that is, the gravitational tilt torque is detected. , divide the detected gravitational tilt torque by the mass characteristic of the triaxial satellite at the time of launch, detect the mass characteristic of the celestial body, and find the mass characteristic of the triaxial satellite that minimizes the integration with respect to the mass characteristic of the detected celestial body. The difference from the mass characteristics of the three-axis satellite at the time of launch is determined for each axis of the three-axis satellite, and the ±2 axes, ±X axis, and ±Y corresponding to the difference in mass characteristics for each axis are calculated.
Axially mounted balancer +41, (51, +6
1, (71, +81, (91) When the expansion/contraction values in each axis direction are calculated backwards and the values are input to the balancer drive device aυ, the balancer drive device aυ becomes the balancer +41 in each axis direction.
, +51, +61, (7), (8)
, (by moving 91 by the amount of movement, the mass characteristics are controlled on the orbit.

As described above, according to the present invention, it is possible to control the mass characteristics of a triaxial satellite in orbit in order to remove the gravitational inclination torque in all directions of the triaxial satellite. This method also has the advantage of reducing the attitude control load on a three-axis satellite and saving fuel on board the three-axis satellite.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the mass characteristics of a celestial body, Fig. 2 is a diagram showing the arrangement of balancers attached to each axis of a three-axis satellite according to the present invention, and Fig. 3 is a diagram showing the arrangement of the balancer according to the present invention, which is extended and contracted. FIG. 2 is a diagram for explaining a case where mass is controlled by In the figure, E is the Earth, (1) is the three-axis satellite, (2) is the observation equipment, (3) is the direction of orbit, (4) is the two-axis balancer, and (5) is the -2-axis balancer. , (6) is the X-axis lancer, (
71) - X-axis balancer, (8) is Y-axis balancer, (
9) is a −Y-axis balancer, Q[l is a communication device, aυ is a balancer drive device, (16 is an attitude sensor, aj is a gyro, and Q41 is an attitude control device. Note that the same or equivalent parts in the figure are the same. They are indicated with symbols. Agent Shin Kuzuno - Figure 1 Figure 2

Claims (1)

[Claims] +11 A balancer is provided on each axis of an artificial satellite that controls the attitude of the X-axis, Y-axis, and X-axis, and a drive device is provided to move the balancer in each axis direction, A mass characteristic control method for an artificial satellite, characterized in that the mass characteristic of the artificial satellite is varied in orbit by moving it according to the gravitational inclination. (2) The satellite mass characteristic control system according to claim 1, wherein the amount of movement of the axis of the balancer is controlled by a command from a ground station. (3) An attitude sensor or a gyro is mounted on the satellite, and the attitude change rate data of each axis of the three-axis attitude control satellite detected by the attitude sensor or gyro is used to control the balancer to move in each axis direction. 2. A mass characteristic control method for an artificial satellite according to claim 1, characterized in that: