System and method for controlling the attitude of a flying object

• US 20040140401A1
• Filed: 08/29/2003
• Published: 07/22/2004
• Est. Priority Date: 08/30/2002
• Status: Abandoned Application

• Current Assignee: Nec Toshiba Space Systems, Ltd. (NEC Space Technologies, Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Yamashita, Toshiaki
• Application Number:
  US10/650,845
• Publication Number:
  US 20040140401A1
• Time in Patent Office: Days
• US Class Current: 244/165
• CPC Class Codes: B64G 1/283 using reaction wheels
• CPC Class Codes: B64G 1/286 using control momentum gyroscopes (CMGs)
• CPC Class Codes: B64G 1/361 using star sensors
• CPC Class Codes: B64G 1/369 using gyroscopes as attitude sensors

Abstract

The attitude of a satellite is controlled by at least three reaction wheels having mutually different rotation axes and at least two control moment gyroscopes having gimbal axes which extend in an equal direction. The reaction wheels and the control momentum gyros are controlled according to calculated values. When the rotors of the gyroscopes are given rotations in opposite directions to each other, angular momentum vectors are produced in respective directions normal to the directions of rotation of the rotors about their gimbal axes.

Claims

1. A system for controlling the attitude of a flying object, comprising:

at least three reaction wheels having mutually different rotation axes;

means for controlling rotation of said reaction wheels for controlling the attitude of said flying object;

at least two control moment gyroscopes having gimbal axes which extend in an equal direction, said gyroscopes including respective rotors; and

means for controlling rotation of said rotors in opposite directions to each other for controlling the attitude of said flying object so that angular momentum vectors of said rotors are produced in respective directions normal to the directions of rotation of said rotors about the respective gimbal axes.

2. The system of claim 1, wherein the number of said reaction wheels is four.

3. The system of claim 1, further comprising:

means for sensing an attitude angle and attitude angular velocity of said flying object;

means for calculating values of torque to be given to said reaction wheels and said control moment gyroscopes based on the sensed angle and angular velocity; and

means for driving said reaction wheels and said control moment gyroscopes according to the calculated values of torque.

4. The system of claim 3, wherein said sensing means detects said angle and angular velocity at unit intervals,

wherein said calculating means comprises:

means for setting a correction angle about an attitude correction rotation axis and correction angles respectively about the axes of a 3-axis coordinate system of said flying object with respect to a reference attitude of the flying object and a correction time;

means for calculating angular acceleration based on said correction angles and said correction time and producing therefrom an attitude angle profile;

means for successively calculating a reference attitude Euler parameter based on said attitude angle profile for indicating a reference attitude of said flying object at said unit intervals;

means for calculating a current attitude Euler parameter based on said angular velocity detected at said unit intervals for indicating a current attitude of said flying object;

means for detecting an attitude error Euler parameter representing a difference between said current attitude Euler parameter and said reference attitude Euler parameter;

means for calculating, for each axis of said coordinate system, an attitude error vector representing a rotation angle about the axis based on said attitude error Euler parameter;

means for calculating torque based on said attitude error vector for each of said reaction wheels; and

means for calculating torque based on said attitude error vector for each of said control moment gyroscopes.

5. The system of claim 3, wherein said sensing means detects said angle and angular velocity at unit intervals,

wherein said calculating means comprises:

means for setting a correction angle about an attitude correction rotation axis of said flying object with respect to a reference attitude of the flying object, a correction time and a reference attitude Euler parameter;

means for calculating a current attitude Euler parameter based on said angular velocity detected at said unit intervals for indicating a current attitude of said flying object;

means for detecting an attitude error Euler parameter representing a difference between said current attitude Euler parameter and said reference attitude Euler parameter;

means for detecting an attitude error angle about said attitude correction rotation axis which will be corrected during a subsequent time interval based on said attitude error Euler parameter;

means for calculating torque based on said attitude error angle; and

means for converting the calculated torque to 3-axis vectors corresponding to the three axes of said coordinate system for application to said reaction wheels and said control moment gyroscopes.

6. The system of claim 1, 2, 3, 4 or 5, wherein said flying object is a satellite.

7. A method of controlling the attitude of a flying object, comprising:

producing torque by controlling rotation of at least three reaction wheels whose rotation axes are mutually different from each other, and controlling rotation of respective rotors of at least two control moment gyroscopes whose gimbal axes extend in an equal direction, said rotation being such that said rotors are rotated in opposite directions to each other so that angular momentum vectors of said rotors are produced in respective directions normal to the directions of rotation of said rotors about the respective gimbal axes.

8. The method of claim 7, wherein said torque is produced by the step of producing torque for said reaction wheels and the step of producing torque for said control moment gyroscopes.

9. The method of claim 7, wherein said torque is produced by the step of simultaneously producing torque for said reaction wheels and said control moment gyroscopes.

10. The method of claim 7, 8 or 9, further comprising the steps of:

sensing an attitude angle and attitude angular velocity of said flying object;

calculating values of torque to be given to said reaction wheels and said control moment gyroscopes based on the sensed angle and angular velocity; and

driving said reaction wheels and said control moment gyroscopes according to the calculated values of torque.

11. The method of claim 10, wherein the sensing step comprises detecting said angle and angular velocity at unit intervals,

wherein the calculating step comprises the steps of:

setting a correction angle about an attitude correction rotation axis and correction angles respectively about the axes of a 3-axis coordinate system of said flying object with respect to a reference attitude of the flying object and a correction time;

calculating angular acceleration based on said correction angles and said correction time and producing therefrom an attitude angle profile;

successively calculating a reference attitude Euler parameter based on said attitude angle profile for indicating a reference attitude of said flying object at said unit intervals;

calculating a current attitude Euler parameter based on said angular velocity detected at said unit intervals for indicating a current attitude of said flying object;

detecting an attitude error Euler parameter representing a difference between said current attitude Euler parameter and said reference attitude Euler parameter;

calculating, for each axis of said coordinate system, an attitude error vector representing a rotation angle about the axis based on said attitude error Euler parameter;

calculating torque based on said attitude error vector for each of said reaction wheels; and

calculating torque based on said attitude error vector for each of said control moment gyroscopes.

12. The method of claim 10, wherein the sensing step comprises detecting said angle and angular velocity at unit intervals,

wherein said calculating step comprises:

setting a correction angle about an attitude correction rotation axis of said flying object with respect to a reference attitude of the flying object, a correction time and a reference attitude Euler parameter;

calculating a current attitude Euler parameter based on said angular velocity detected at said unit intervals for indicating a current attitude of said flying object;

detecting an attitude error Euler parameter representing a difference between said current attitude Euler parameter and said reference attitude Euler parameter;

detecting an attitude error angle about said attitude correction rotation axis which will be corrected during a subsequent time interval based on said attitude error Euler parameter;

calculating torque based on said attitude error angle; and

converting the calculated torque to 3-axis vectors corresponding to the three axes of said coordinate system for application to said reaction wheels and said control moment gyroscopes.