JP3168802B2 - Steady-state attitude reacquisition method for satellites - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for re-acquiring a stationary attitude of an artificial satellite.

[0002]

2. Description of the Related Art An attitude control system having a wheel arrangement shown in FIG. 4 will be described below as an example. In FIG. 4, 1 is the first
, 2 is a second wheel, and 3, 4, and 5 are a roll axis, a pitch axis, and a yaw axis of the satellite, respectively. Here, the wheels 1 and 2 are arranged in a V-shape. When used at a bias speed, a bias angular momentum is given in the negative pitch axis direction, and the roll / yaw is determined by the speed difference between the wheels 1 and 2. In-plane angular momentum can also be generated.

FIG. 5 is a block diagram of a conventional attitude control system using the above-described wheel configuration. In FIG. 5, reference numeral 6 denotes an angle sensor for detecting the attitude angle of an artificial satellite, and reference numeral 7 denotes the output of the angle sensor 6. An attitude control processing circuit for generating a drive signal for the wheels so that the artificial satellite keeps the target attitude, respectively, is a wheel 1 / wheel drive circuit and a wheel 2 / wheel drive circuit. The attitude control processing circuit 7 includes a control law calculation processing unit 10, a command distribution law calculation processing unit 11, and a wheel speed command / speed loop calculation processing unit 12.

[0004] The control law calculation processing unit 10 calculates a torque command around each control axis, roll, pitch, and yaw axis such that the artificial satellite maintains the target attitude based on the angle signal output from the angle sensor 6. . Next, the command distribution rule calculation processing unit 11 distributes a torque command to each wheel based on the output of the control rule calculation processing unit 10. The wheel speed command / speed loop calculation processing unit 12 has an integrator for calculating the speed command to each wheel by integrating the torque command to each wheel output from the command distribution rule calculation processing unit 11. The tachometer signal from each wheel is fed back to form a speed loop so that each wheel follows the speed command, and the drive signal to each wheel is calculated.

[0005] By configuring the attitude control electronic circuit as described above, the sum of the torques of the respective wheels realizes the control law specified by the control law calculation processing unit, and the attitude of the artificial satellite is controlled normally. Is done.

[0006]

As described above, the conventional attitude control system has an integrator for calculating the wheel speed command. However, when the attitude control processing circuit is abnormal and switches to the redundant side, However, since the integrator on the redundant side cannot be properly initialized, there is a problem in that the system shifts to a safety mode typified by the sun directing mode or the like, and the mission must be interrupted for a long period of time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. Even when the attitude control processing circuit is abnormally switched to the redundant side during normal operation of the satellite, the normal attitude is immediately changed. The aim is to recapture and minimize mission interruption time.

[0008]

According to the present invention, there is provided a satellite attitude re-acquisition method according to the present invention, wherein a wheel speed command initialization processing unit for initializing an integrator for calculating a wheel speed command is provided.

[0009]

According to the steady attitude reacquisition method for an artificial satellite according to the present invention, since the integrator for calculating the wheel speed command is appropriately initialized by the wheel speed command initialization processing section, before and after switching of the attitude control processing circuit. Thus, the sudden change of the wheel speed command does not occur, and the steady attitude control can be continuously performed even after the switching of the attitude control processing circuit.

[0010]

【Example】

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of a method for re-acquiring a normal attitude of an artificial satellite according to the present invention. In the figure, reference numerals 6 to 12 correspond to a block diagram of a conventional attitude control system (FIG. 5). It is the same as the one. The present invention is different from the conventional attitude control system in that a wheel speed command initialization processing unit 13 for initializing an integrator for wheel speed command calculation in the wheel speed command / speed loop calculation processing unit 12 is provided. .

Hereinafter, the principle and function of the wheel speed command initialization processing unit 13 will be described. Generally, the wheel speed changes with motor torque, loss torque, etc.
Changes in wheel speed on the order of seconds are small. For this reason, when the failure determination processing of the attitude control processing circuit is executed in a short time and switches to the redundant side, the speed change of each wheel during that time may be considered to be small. On the other hand, as long as the attitude control processing circuit is normal due to the wheel speed loop, the speed of each wheel substantially matches the speed command.

From the above facts, the speed of each wheel immediately after the attitude control processing circuit is switched to the redundant side has a value close to each wheel speed command immediately before the occurrence of an abnormality in the attitude control processing circuit. Therefore, immediately after switching the attitude control processing circuit, the wheel speed command initialization processing unit 13 monitors the tachometer signal of each wheel to determine the wheel speed, and initializes the integrator for calculating the wheel speed command with the value. The wheel speed command does not change significantly between immediately before the occurrence of an abnormality in the attitude control processing circuit and immediately after switching to the redundant side, and the control is continued using the attitude control rule in a steady state even after the attitude control processing circuit is switched. be able to.

Embodiment 2 FIG. 2 is a block diagram showing Embodiment 2 using the method of re-capturing a satellite's steady attitude according to the present invention. The angular velocity sensor 14 is added to the attitude control system of FIG. This is a modification of the initial value calculation algorithm of the speed command initialization processing unit 13. In this embodiment, as an input signal of the wheel speed command initialization processing unit 13, an angular velocity signal output from the angular velocity sensor 14 is used in addition to the wheel tachometer signal.

Hereinafter, the principle employed in this embodiment and the function of the wheel speed command initialization processing unit 13 will be described. The inertia matrix of the satellite is [I],
Assuming that the angular velocity is ω and the angular momentum of the wheel is h _W , the angular momentum H _T of the entire artificial satellite is given by the following equation.

[0015]

(Equation 1)

Here, the angular momentum H _T of the entire satellite is constant according to the law of conservation of angular momentum when no external force torque is applied. Angular momentum H immediately before occurrence of an abnormality in the control processing circuit and immediately after switching to the redundant side attitude control processing circuit
_T can be considered almost equal. When a suffix B is added to a value immediately before the occurrence of an abnormality in the attitude control processing circuit and a suffix A is added to a value immediately after switching to the redundant side, the angular momentum H _TA ,
H _TB can be expressed by the following equation using the angular momentums h _WA and h _WB of the wheel and the angular velocities ω _A and ω _B of the satellite.

[0017]

(Equation 2)

Since H _TA and H _TB are substantially equal according to the above-mentioned law of conservation of angular momentum, the wheel angular momentum h _WB immediately before the occurrence of an abnormality is obtained.
Is given by the following equation.

[0019]

(Equation 3)

[0020] Here, omega _B is the angular velocity immediately before the abnormality of posture control processing circuit is generated, is a value after switching is not known to the redundant side attitude control processing circuit, the target rate omega _C in a steady state attitude control if the replace it with, it is possible to estimate the h _WB by the angular velocity signal of the wheel tachometer signal and the angular velocity sensor 14 immediately after the switching to the redundant side.
If h _WB is obtained in this way, the velocity command to each wheel can be calculated by the distribution rule so that the initial value h _WO of the wheel angular momentum command becomes equal to h _WB, and this value is used as the initial value. What should I do?

As described above, in this embodiment, by adding the angular velocity signal of the angular velocity sensor 14 to the wheel velocity command initialization processing, the angular momentum of the wheel is reduced by the influence of the motor torque, the loss torque and the like. Even if it changes to some extent before and after switching to, it is possible to cope with it. Therefore, in this embodiment, the algorithm of the wheel speed command initialization processing unit 13 is more complicated than in the first embodiment, but the time from the occurrence of an abnormality in the attitude control processing circuit to the switching to the redundant side is somewhat longer. It has the advantage of being able to handle long cases.

In the above example, the initial value h _WO of the wheel angular momentum command is set to be equal to h _WB . However, from the viewpoint of improving the transient response of the system, h is given by the following equation.
_WO can also be used.

[0023]

(Equation 4)

Here, the coefficient β is a coefficient for adjusting the transient response, and usually uses a value of 0 or more.

Third Embodiment FIG. 3 is a block diagram showing a third embodiment of the present invention. The components are basically the same as the block diagram of the first embodiment (FIG. 1). The difference from the first embodiment is that an angle signal output from the angle sensor 6 is used as an input to the wheel speed command initialization processing unit 13 in addition to the tachometer signal from the wheel.

The following describes how angle signals are used to initialize wheel speed commands. In the wheel arrangement of FIG. 4, it is assumed that the rotation axes of the wheels 1 and 2 are canted by η from the minus pitch axis to the plus yaw axis and minus yaw axis, respectively. The angular momentum components h _WY and h _WZ of the artificial satellite by the wheels in the pitch axis and yaw axis directions are given by the following equations using the angular momentums h _W1 and h _w2 of the wheels 1 and ₂ and the cant angle η.

[0027]

(Equation 5)

In the case of a bias momentum system in which a bias angular momentum is given around a minus pitch axis and the angular momentum is used, the angular momentum of an artificial satellite is expressed by a coordinate system called an orbital coordinate system based on a target attitude. , Are controlled so that their components become nominal values. When the angular velocity of the satellite is small, the components H _YO and H of the pitch axis and the yaw axis when the angular momentum of the satellite is viewed in the orbital coordinate system
_ZO can be approximated by the following equation.

[0029]

(Equation 6)

Here, φ indicates the roll attitude angle. H
_As can be seen from the _ZO equation, in the orbital coordinate system, the angular momentum of the yaw axis depends not only on the angular momentums h _W1 and h _{W2 of} each wheel but also on the attitude angle φ. The purpose of the attitude control system using wheels is to absorb all the _HZO by the wheels and reduce the attitude error to zero. Therefore, when the attitude control processing circuit switches to the redundant side, the initial value of the angular momentum is than h _WZ, it is better to use the H _ZO.

As described above, by adding the angle signal, which is the output of the angle sensor, in addition to the tachometer signal as an input to the wheel speed command initialization processing unit 13, a more desirable angle than in the case of only the tachometer signal is obtained. The initial value of the momentum can be obtained, and the transient response characteristics after switching on the redundant side can be improved.

In the second and third embodiments, the wheel speed command is initialized by taking in the output signal of the angular speed sensor or the angle sensor in addition to the tachometer signal of the wheel. You may take in.

[0033]

As described above, according to the present invention, the provision of the wheel speed command initialization processing unit enables the continuous execution of the steady attitude control even when the attitude control processing circuit is switched to the redundant side. And the mission interruption time can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing Embodiment 2 of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a wheel arrangement of the satellite attitude control system.

FIG. 5 is a block diagram showing a conventional satellite attitude control system.

[Explanation of symbols]

 Reference Signs List 6 Angle sensor 7 Attitude control processing circuit 8 Wheel 1 / wheel drive circuit 9 Wheel 2 / wheel drive circuit 10 Control law calculation processing unit 11 Command distribution law calculation processing unit 12 Wheel speed command / speed loop calculation processing unit 13 Wheel speed command initial Processing unit 14 angular velocity sensor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B64G 1/28 G05D 1/08

Claims (4)

(57) [Claims] An angle sensor for detecting an attitude angle of an artificial satellite, and an attitude control processing circuit for generating a drive signal for a wheel based on a signal from the angle sensor so that the artificial satellite maintains a target attitude. And a wheel drive circuit. The attitude control processing circuit includes a control law calculation processing unit, a command distribution law calculation processing unit, and a wheel speed command / speed loop calculation processing unit necessary for normal control. A command initialization processing unit is added, and when the attitude control processing circuit switches to the redundant side due to abnormality, the wheel speed command initialization processing unit initializes the wheel speed command based on the tachometer signal of the wheel. A normal attitude reacquisition method for an artificial satellite, wherein the method shifts to normal attitude control after execution. 2. An artificial satellite re-acquisition method according to claim 1, wherein an angular velocity signal of an angular velocity sensor is incorporated in addition to a tachometer signal of a wheel in initialization of a wheel velocity command. A method for re-acquiring the satellite's steady attitude. 3. A satellite attitude reacquisition method according to claim 1, wherein an angle signal of an angle sensor is incorporated in addition to a tachometer signal of a wheel in initialization of a wheel speed command. Steady posture recapture method. 4. The method of claim 1, wherein the angular velocity signal of the angular velocity sensor and the angle signal of the angle sensor are incorporated in addition to the tachometer signal of the wheel in the initialization of the wheel velocity command. A steady attitude reacquisition method for an artificial satellite, characterized in that: