JPS6055360B2 - Satellite attitude control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an artificial satellite attitude control device for a bias momentum type Ξ-axis artificial satellite equipped with a beam action wheel.

A three-axis satellite is one in which the three orthogonal axes fixed to the satellite are controlled to point in the direction of travel of the satellite, in the direction perpendicular to the orbital plane, and in the direction of the center of the Earth. are called the roll axis, pitch axis, and yaw axis, respectively.

A bias-momentum type three-axis satellite is a type of satellite that gives a large angular momentum in the pitch axis direction by rotation of a momentum wheel to reduce the influence of disturbance torque on attitude changes by stabilizing the top. It is called. FIG. 1 is an explanatory diagram showing an example of a conventional artificial satellite attitude control device.
The axes indicate the roll axis, pitch axis, and yaw axis, respectively. 1 is a momentum wheel whose rotation axis is parallel to the y-axis, and 2 is a momentum wheel that detects attitude changes around the roll axis and pitch axis of the satellite. In the earth sensor, 3 is a roll reaction wheel whose rotation axis is parallel to the x-axis, and 4 is a yaw reaction wheel whose rotation axis is parallel to the z-axis.

The inclination of the pitch axis with respect to the pitch axis is actively controlled by changing the rotation speed of the momentum wheel 1 in accordance with the output of the earth sensor 2.

However, due to the influence of disturbance torque, the satellite's attitude changes around the roll axis (this rotation angle is called the roll angle) and around the yaw axis (this rotation angle is called the yaw angle) change over time. However, if high precision is required, as shown in Figure 1, it is possible to have a rotation axis parallel to the roll axis and yaw axis, or to attach action wheels 3 and 4 to absorb the disturbance torque. Therefore, the roll angle and yaw angle of posture change can be controlled.

Generally, bias momentum three-axis satellites often do not have a sensor to detect the yaw angle. Furthermore, the motion around the pitch axis has no relation to the motion around the roll axis or the yaw axis. Therefore, control of the roll angle and yaw angle must be performed based only on the roll angle signal obtained from the earth sensor 2. A bias momentum type three-axis artificial satellite has a vibration mode called nutation, and simply feeding back the roll angle signal to the action wheels 3 and 4 makes this mode unstable.

For this purpose, in conventional satellites, the roll angle signal is fed back to the yaw reaction wheel 4 to control the static roll angle, and the roll angular velocity signal (obtained by differentiating the roll angle signal) is fed back to the roll reaction wheel. It is a system that suppresses dynamic posture changes (nutation movements) by backing up.

FIG. 2 is a block diagram showing the control system of a conventional artificial satellite attitude control device. In the figure, 2, 3, 4 indicate the same parts as the same symbols in FIG. 1, 11 is a differentiator, 12a ,12
b is an amplifier, φ is a roll angle signal, and φ is a differential value of the roll angle signal value.

However, as mentioned above, the two action wheels in this system have completely different functions. Furthermore, if only one of the wheels were to fail, the control systems for the roll and yaw reaction wheels would no longer be able to function as they were. In other words, if only the roll reaction wheel fails, it is possible to control it only with the yaw reaction wheel by changing the electronics circuit.
If the yaw reaction wheel fails, the entire system will stop functioning. This invention was made in order to eliminate the drawbacks of the conventional wheels as described above.
Installed at an angle of 5 degrees, each glue action wheel has the functions of roll angle control and nutrition movement control, and when normal, it can be controlled to have exactly the same functions as conventional ones, and either one of the glue action wheels The purpose of the present invention is to provide an artificial satellite attitude control device that can shift to a backup mode even if the satellite fails, without changing any circuits or the like.

FIG. 3 is an explanatory diagram showing an embodiment of the present invention. In the figure, 1 and 2 indicate parts that are the same as or correspond to the same reference numerals in FIG. 6 is a first glue action wheel having an offset of 4 degrees from the yaw axis, and 6 is a second glue action wheel having a rotation axis perpendicular to the rotation axis of the first glue action wheel 5 in a plane perpendicular to the pitch axis. be. FIG. 4 is a block diagram showing an embodiment of the control system according to the present invention, and in the figure, 2, 5, 6, 11, 12a, and 12b are the same as or correspond to the same reference numerals in FIGS. 2 and 3. 13 is a subtracter and 14 is an adder.

In this embodiment, the posture control by the glide action wheel is performed by applying a torque proportional to (φ+φ) to the first glide action wheel 5, and applying a torque proportional to (−φ+φ) to the second glide action wheel 6, as shown in FIG. This is achieved by feeding back a torque proportional to φ).

Here, φ is a roll angle signal, and φ is a differential value of φ. In the above control, it is clear that the torque in the x-axis direction is proportional only to φ, and the torque in the z-axis direction is proportional only to φ, so under normal conditions, the control performance is exactly the same as the conventional one. This means that you have .

The advantage of arranging the action wheels as described above and controlling as shown in FIG. 4 becomes noticeable when either one of the action wheels breaks down.

In this device, each of the two rolling action wheels has two functions: roll angle control and nutrition motion control.

Therefore, if only one of the action wheels stops functioning, the performance will be somewhat inferior to the case where both wheels are normal, but sufficient performance can be expected as a backup mode. The important point here is that the transition from normal mode to backup mode does not require any change in the control mechanism, so no additional equipment is required. In the above embodiment, the offset angle was set to 45 degrees in order to give the same load to the two sliding action wheels, but there is no particular need to limit it to 45 degrees, and even if it is set to 30 degrees, the offset angle is 60 degrees. At any given time, as long as the axis of rotation of either of the two action wheels is not perpendicular to the roll axis or the yaw axis, it is possible to achieve some effect in the backup mode. The size should be left to the designer's choice. As described above, according to the present invention, the attitude control performance when either one of the action wheels fails is greatly improved compared to conventional devices.

It should be noted that the cost increases due to changes in the mounting state of the action wheel and changes in the control mechanism are so small that they hardly pose a problem.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a conventional artificial satellite attitude control device, FIG. 2 is a block diagram showing a control system of a conventional artificial satellite attitude control device, and FIG. 3 is an explanatory diagram showing an example of the present invention. 4 are block diagrams showing one embodiment of a control system according to the present invention.

Claims (1)

[Claims] 1 When the attitude of the artificial satellite is normal, the axis pointing in the direction of movement is the roll axis, the axis pointing perpendicular to the orbital plane is the pitch axis, the axis pointing from the satellite toward the center of the earth is the yaw axis, and the momentum In an artificial satellite attitude control device that controls the attitude of a bias momentum type three-axis artificial satellite that increases the angular momentum in the pitch axis direction by rotating a wheel, by observing the deviation in the direction of the earth's center with respect to the yaw axis, an earth sensor that detects a roll angle that is an error angle of the satellite around the roll axis; a first reaction wheel having a rotation axis tilted at 45 degrees with respect to the yaw axis in a plane perpendicular to the pitch axis; ,
a second reaction wheel having a rotation axis in a direction perpendicular to the rotation axis of the first reaction wheel in a plane perpendicular to the pitch axis; the first reaction wheel is controlled by the sum of the output signal of the differentiator and the signal proportional to the roll angle, and the difference between the output signal of the differentiator and the signal proportional to the roll angle Therefore, an artificial satellite attitude control device is characterized in that it controls the second reaction wheel.