Method and device for controlling satellite attitude and steering using a gyrodyne cluster

• US 20040167683A1
• Filed: 12/29/2003
• Published: 08/26/2004
• Est. Priority Date: 06/26/2001
• Status: Active Grant

• Current Assignee: EADS Astrium SAS (Airbus SE), Splashpower Limited
• Original Assignee: Splashpower Limited
• Inventors: Lagadec, Kristen, Defendini, Ange
• Granted Patent: US 7,171,290 B2
• Time in Patent Office: Days
• US Class Current: 701/13
• CPC Class Codes: B64G 1/244 Spacecraft control systems

Abstract

In order to control the attitude of a satellite having at least four gyroscopic actuators with respective spinners mounted on gimbals steerable about axes parallel to one or the other of only two different directions that are fixed relative to the satellite, the attitude of the satellite is measured using sensors on board the satellite, the control torque required to perform an attitude-changing maneuver is calculated, local linearization calculation is performed based on pseudo-inversion of the Jacobean matrix of the function associating the orientations of the actuator gimbals with the total kinetic moment of the cluster in order to determine a new gimbal orientation, and precession speeds of at least one of the gimbals of the actuators is controlled to deliver the control torque for reaching the desired configuration. The calculation is performed while applying a constraint of seeking a cluster configuration that is remote from singular configurations by sharing between the two groups of actuators that component of the total kinetic moment of the cluster which is perpendicular to both of the two directions.

Claims

1. A method of controlling the attitude of a satellite having a cluster of at least four gyroscopic actuators with respective spinners mounted on gimbals steerable about axes parallel to one or the other of only two different directions that are fixed relative to the satellite, the method comprising the steps of:

measuring the attitude of the satellite by means of sensors on board the satellite;

calculating the control torque required to perform an attitude-changing maneuver;

calculating local linearization based on pseudo-inversion of the Jacobean matrix of the function associating the orientations of the actuator gimbals with the total kinetic moment of the cluster in order to determine new orientations for the gimbals; and

controlling precession speeds of at least one of the actuator gimbals so as to deliver the control torque for reaching the desired configuration;

the method being characterized by the step of performing the calculation by applying a constraint of seeking a cluster configuration remote from singular configurations by sharing between the two groups of actuators that component of the total kinetic moment of the cluster which is perpendicular to both of said two directions.

2. A method according to claim 1, characterized by the step of adopting, as a criterion for the remoteness of a configuration of the angles of the gimbals in the cluster from a singular configuration, the product of two simpler criteria that apply separately to each of the two groups of actuators.

3. A method according to claim 2, characterized in that, for a group constituted by two actuators each carrying a non-dimensional kinetic moment of unity norm, the criterion for remoteness between a configuration of gimbal angles and a singular configuration is selected as:

being zero when the angle between the two kinetic moment vectors carried by the two actuators is zero or flat; and

reaching a maximum when the angle between the two kinetic moment vectors carried by the two actuators is close to 90°

.

4. A method according to claim 3, characterized in that the criterion for remoteness of a configuration of gimbal angles from a singular configuration is determined by using one of the following parameters:

the norm of the vector product of two kinetic moment vectors carried by the two actuators;

the absolute value of the sine of the angle formed between the two kinetic moment vectors carried by the two actuators;

the area of a triangle having two sides constituted by the kinetic moment vectors carried by the two actuators, their origins coinciding; and

the difference between unity and the absolute value of the scalar product of the two kinetic moment vectors carried by the two actuators.

5. A method according to claim 2, characterized in that the group under consideration being constituted by three actuators each carrying a non-dimensional kinetic moment of unity norm, the criterion for remoteness between a configuration of gimbal angles and a singular configuration is defined in such a manner as to cancel when one of the angles formed between any two of the three kinetic moment vectors carried by the three actuators is zero and so as to reach its maximum when said angles are close to 120°

.

6. A method according to claim 5, characterized in that the remoteness between a configuration of gimbal angles and a singular configuration is determined by using one of the following parameters:

the sum of the three vector products between pairs of the kinetic moment vectors carried by the three actuators; and

the area of the triangle whose vertices coincide with the vertices of the kinetic moment vectors carried by the three actuators, their origins coinciding.

7. A method according to any preceding claim for controlling the satellite in application of a relationship that is determined over time, the method being characterized in that a final configuration remote from singularities is sought continuously by permanently deflecting the cluster configuration so as to occupy the local maximum of the distance-from-singularity criterion.

8. A method according to any one of claims 1 to 6, characterized in that a final configuration remote from singularities is sought when it is detected that the remoteness between the current configuration and the associated singularity has dropped below a predetermined threshold.

9. A method according to any one of claims 1 to 6, characterized in that in order to perform a determined attitude maneuver reaching a final configuration that is remote from singularities, attitude is controlled by associating open loop control with closed loop control.

10. A method according to claim 9, characterized in that prior calculation is used to establish a correspondence table between the various cluster kinetic moments needed for the various satellite maneuvers and respective associated optimum cluster configurations so as to reach a final configuration that is remote from singularities.

11. A method according to claim 9, characterized in that the search for a final configuration remote from singularities provides directly and in analytic manner an optimum cluster configuration delivering the requested cluster kinetic moment needed for maneuvering the satellite.

12. A method according to claim 7, characterized in that it is implemented in advance on the basis of prior knowledge of the maneuver that is to be performed, and the satellite attitude maneuver is performed by using the resulting trajectory in an open loop in attitude control associating an open loop control with a closed loop control for bringing the satellite into the desired final attitude.