Device for controlling attitude of spacecraft and method for calculating CMG gimbal angle

Patent metadata

Field	Value
Publication number	US-10407187-B2
Application number	US-201615735653-A
Country	US
Kind code	B2
Filing date	Jun 17, 2016
Priority date	Jun 22, 2015
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

When the number of CMGs is represented by n (n is an integer of 4 or more), (n−3) gimbal angles out of n gimbal angles corresponding to the n CMGs are set as free parameters, and an algebraic equation representing a relationship among three gimbal angles out of the n gimbal angles, the free parameters, and an angular momentum of all the CMGs is used to solve the algebraic equation while changing the free parameters within set ranges, to thereby obtain solutions of the gimbal angles of the plurality of CMGs required for achieving a given angular momentum.

First claim

The invention claimed is:

1. An attitude control device for a spacecraft, which is configured to control an attitude of a spacecraft through use of a plurality of CMGs, the plurality of CMGs being installed in the spacecraft and each comprising a wheel configured to rotate about a spin axis, and a gimbal configured to support the wheel and to rotate about a gimbal axis orthogonal to the spin axis,
the attitude control device comprising a processor,
wherein the processor:
obtains solutions of gimbal angles of the plurality of CMGs required for achieving a given angular momentum of all the plurality of CMGs;
feeds back observed values of an attitude angle and an attitude angular velocity of the spacecraft, and observed values of the gimbal angles and gimbal angular velocities of the respective plurality of CMGs, to thereby calculate gimbal control torques of the respective plurality of CMGs required for achieving a desired attitude change in the spacecraft; and
calculates the gimbal control torques of the plurality of CMGs through use of the solutions of the gimbal angles of the plurality of CMGs obtained from the angular momentum of all the plurality of CMGs; and
when a number of the plurality of CMGs is represented by n, wherein n is an integer of 4 or more, sets (n−3) gimbal angles out of n gimbal angles corresponding to the n CMGs as free parameters, and uses an algebraic equation representing a relationship among three gimbal angles out of the n gimbal angles, the free parameters, and the angular momentum of all the plurality of CMGs to solve the algebraic equation while changing values of the free parameters within set ranges, to thereby obtain the solutions of the gimbal angles of the plurality of CMGs for achieving the given angular momentum of all the plurality of CMGs.

2. The attitude control device for a spacecraft according to claim 1 , wherein the processor further:
calculates gimbal angle planned values and gimbal angular velocity planned values of the respective plurality of CMGs;
calculates an attitude angle target value and an attitude angular velocity target value of the spacecraft from the gimbal angle planned values and the gimbal angular velocity planned values of the respective plurality of CMGs;
calculates an attitude control torque for controlling the attitude of the spacecraft from the attitude angle target value and the attitude angular velocity target value of the spacecraft and the observed values of the attitude angle and the attitude angular velocity of the spacecraft;
calculates gimbal angle correction values and gimbal angular velocity correction values of the respective plurality of CMGs from the attitude control torque;
adds the gimbal angle planned values and the gimbal angular velocity planned values of the respective plurality of CMGs and the gimbal angle correction values and the gimbal angular velocity correction values of the respective plurality of CMGs to one another, respectively, to thereby calculate gimbal angle target values and gimbal angular velocity target values of the respective plurality of CMGs; and
calculates the gimbal control torques of the respective plurality of CMGs from the gimbal angle target values and the gimbal angular velocity target values of the respective plurality of CMGs and the observed values of the gimbal angles and the gimbal angular velocities of the respective plurality of CMGs.

3. The attitude control device for a spacecraft according to claim 2 , wherein the processor further:
sets a candidate value of a maximum angular momentum that all the plurality of CMGs are able to generate, as the given angular momentum of all the plurality of CMGs;
obtains solutions of the gimbal angles of the respective plurality of CMGs for achieving the candidate value; and
successively updates the candidate value in accordance with absence or presence of the solutions of the gimbal angles of the respective plurality of CMGs for achieving the candidate value, to thereby calculate the maximum angular momentum.

4. The attitude control device for a spacecraft according to claim 3 , wherein the processor further:
calculates a first angular momentum target value less than the maximum angular momentum that all the plurality of CMGs are able to generate, and sets the calculated first angular momentum target value as the given angular momentum of all the plurality of CMGs; and
obtains solutions of the gimbal angles of the respective plurality of CMGs for achieving the first angular momentum target value, selects solutions that minimize a first evaluation function as first optimal solutions out of the obtained solutions of the gimbal angles of the respective plurality of CMGs for achieving the first angular momentum target value, and sets the selected first optimal solutions as intermediate gimbal angles of the respective plurality of CMGs.

5. The attitude control device for a spacecraft according to claim 4 , wherein the processor further:
calculates a minute change amount of the angular momentum of all the plurality of CMGs from the attitude control torque, adds the minute change amount to a current value of the angular momentum of all the plurality of CMGs to calculate a second angular momentum target value, and sets the calculated second angular momentum target value as the given angular momentum of all the plurality of CMGs;
obtains solutions of the gimbal angles of the respective plurality of CMGs for achieving the second angular momentum target value, selects solutions that minimize a second evaluation function as second optimal solutions out of the obtained solutions of the gimbal angles of the respective plurality of CMGs for achieving the second angular momentum target value; and
calculates the gimbal angular velocity correction values of the respective plurality of CMGs in accordance with the second optimal solutions.

6. The attitude control device for a spacecraft according to claim 3 , wherein the processor further:
calculates a minute change amount of the angular momentum of all the plurality of CMGs from the attitude control torque, adds the minute change amount to a current value of the angular momentum of all the plurality of CMGs to calculate a second angular momentum target value, and sets the calculated second angular momentum target value as the given angular momentum of all the plurality of CMGs;
obtains solutions of the gimbal angles of the respective plurality of CMGs for achieving the second angular momentum target value, selects solutions that minimize a second evaluation function as second optimal solutions out of the obtained solutions of the gimbal angles of the respective plurality of CMGs for achieving the second angular momentum target value; and
calculates the gimbal angular velocity correction values of the respective plurality of CMGs in accordance with the second optimal solutions.

7. The attitude control device for a spacecraft according to claim 2 , wherein the processor further:
calculates a first angular momentum target value less than the maximum angular momentum that all the plurality of CMGs are able to generate, and sets the calculated first angular momentum target value as the given angular momentum of all the plurality of CMGs; and
obtains solutions of the gimbal angles of the respective plurality of CMGs for achieving the first angular momentum target value, selects solutions that minimize a first evaluation function as first optimal solutions out of the obtained solutions of the gimbal angles of the respective plurality of CMGs for achieving the first angular momentum target value, and sets the selected first optimal solutions as intermediate gimbal angles of the respective plurality of CMGs.

8. The attitude control device for a spacecraft acco

Assignees

• Mitsubishi Electric Corp

Inventors

• Kitamura Kenji
• Yamada Katsuhiko
• Shima Takeya

Classifications

• G05D1/08

  Control of attitude, i.e. control of roll, pitch, or yaw · CPC title

• G01C19/02

  Rotary gyroscopes · CPC title

• B64G1/28

  using inertia or gyro effect · CPC title

• B64G1/244

  Spacecraft control systems · CPC title

• B64G1/286 Primary

  using control momentum gyroscopes (CMGs) · CPC title