Method of command of magneto-torquers of an attitude control system of a space vehicle

Patent metadata

Field	Value
Publication number	US-9365301-B2
Application number	US-201314404588-A
Country	US
Kind code	B2
Filing date	Oct 25, 2013
Priority date	Oct 30, 2012
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A method of command of magneto-torquers of an attitude control system of a space vehicle subjected to an external magnetic field of variable direction. The magneto-torquers are configured to desaturate an angular momentum storage device by transferring angular momentum and configured to form, in cooperation with the local external magnetic field, magnetic couples in a plane orthogonal to the direction of the local external magnetic field or a local control plane. The magnetic couple to be formed in the local control plane is determined as a function of the component of a desired attitude control couple which is orthogonal to the local control plane or a locally uncontrollable component. The contribution of the locally uncontrollable component to the magnetic couple to be formed is non-zero when the locally uncontrollable component is non-zero.

First claim

The invention claimed is:

1. A method of commanding magneto-torquers of an attitude control system of a space vehicle subjected to an external magnetic field of variable direction, comprising the steps of:
controlling an attitude of the space vehicle by said magneto-torquers;
forming, in cooperation with a local external magnetic field, magnetic torques in a local control plane orthogonal to a direction of the local external magnetic field;
measuring the local external magnetic field;
determining a magnetic torque to be formed in the local control plane as a function of a desired three-axes attitude control torque;
commanding the magneto-torquers to form, in cooperation with the local external magnetic field, the determined magnetic torque; and
wherein the magnetic torque to be formed in the local control plane is determined as a function of a locally uncontrollable component of the desired attitude control torque which is orthogonal to the local control plane, the contribution of the locally uncontrollable component to the magnetic torque to be formed being non-zero when the locally uncontrollable component is non-zero.

2. The method as claimed in claim 1 , further comprising the step of determining the contribution of the locally uncontrollable component to the magnetic torque to be formed in the local control plane as a function of a model of temporal variation of the direction of the external magnetic field.

3. The method as claimed in claim 1 , further comprising the step of determining the magnetic torque to be formed, the space vehicle progressing in an orbital plane, by expressing a desired variation of angular momentum in a magnetic reference frame centered on the space vehicle and defined by three axes X, Y, Z: an axis X parallel to the direction of the local external magnetic field, an axis Y orthogonal to the axis X and situated in a plane orthogonal to the orbital plane, and an axis Z orthogonal to the axes X and Y.

4. The method as claimed in claim 3 , further comprising the step of determining the magnetic torque to be formed, the space vehicle progressing in a low orbit, in the magnetic reference frame according to a control law expressed in the form:

Tmag
=

-

[

0

0

0

0

Ky

0

Kzx

0

Kz

]

·

Tcmd
Kn

in which expression:
Tmag corresponds to the magnetic torque to be formed,
Tcmd corresponds to the desired attitude control torque,
Kn is a non-zero scalar parameter dimensionally equivalent to a frequency, and
Kzx, Ky and Kz are non-zero scalar parameters or non-zero transfer functions dimensionally equivalent to frequencies.

5. The method as claimed in claim 4 , further comprising the step of expressing, the space vehicle in a polar orbit around the Earth, the scalar parameter Kzx in the form:

Kzx
=

2
·

ω
0

·

(

(

ω
CL

2
·

ω
0

)

2

-
1

)

in which expression:
ω 0 corresponds to the orbital frequency of the space vehicle,
ω CL corresponds to the desired desaturation bandwidth.

6. The method as claimed in claim 1 , wherein the attitude control system comprises an angular momentum storage device; and further comprising the step of desaturating the angular momentum storage system by transfer of angular momentum by the magneto-torquers.

7. The method as claimed in claim 6 , further comprising the step of expressing the desired attitude control torque in the form:
Tcmd=Kn·ΔH

in which expression:
Tcmd corresponds to the desired attitude control torque,
Kn is a non-zero scalar parameter dimensionally equivalent to a frequency,
ΔH corresponds to a desired variation of the angular momentum of the storage device.

8. An attitude control system of a space vehicle subjected to an external magnetic field of variable direction, comprising:
a measurement device to measure a local external magnetic field;
magneto-torquers to form, in cooperation with the local external magnetic field, magnetic torques in a local control plane orthogonal to the direction of said local external magnetic field;
a command unit to determine a magnetic torque to be formed in the local control plane as a function of a desired three-axes attitude control torque, and to command the magneto-torquers to form the determined magnetic torque, wherein the command unit determines the magnetic torque to be formed in the local control plane as a function of a locally uncontrollable component of the desired attitude control torque which is orthogonal to the local control plane, the contribution of the locally uncontrollable component to the magnetic torque to be formed being non-zero when the locally uncontrollable component is non-zero.

9. The attitude control system as claimed in claim 8 , wherein the measurement device is configured to measure the local external magnetic field in relation to three axes.

10. The attitude control system as claimed in claim 8 , wherein the magneto-torquers are configured to form magnetic moments in relation to three axes.

Assignees

• Airbus Defence & Space Sas

Inventors

• Moro Valerio

Classifications

• G05D1/0883

  Physics · mapped topic

• B64G1/32 Primary

  using earth's magnetic field · CPC title

• G01L5/22

  for measuring the force applied to control members, e.g. control members of vehicles, triggers · CPC title

• B64G2001/245

  Operations & Transport · mapped topic

• B64G1/366

  using magnetometers · CPC title