Pseudo gyro

• US 6,020,956 A
• Filed: 02/04/1999
• Issued: 02/01/2000
• Est. Priority Date: 02/04/1999
• Status: Expired due to Term

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: McCain, Ian M., Heatwole, Craig M., Herman, Louis K., Manke, Girard M., Hamada, Brian T.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/243,978
• Time in Patent Office: 362 Days
• Field of Search: 244/166, 244/171, 73/178 R, 701/13, 702/150, 702/151, 356/139.01, 250/559.37
• US Class Current: 356/139.01
• CPC Class Codes: B64G 1/244 Spacecraft control systems
• CPC Class Codes: B64G 1/245 Attitude control algorithms for spacecraft attitude control
• CPC Class Codes: B64G 1/283 using reaction wheels
• CPC Class Codes: B64G 1/32 using earth's magnetic field
• CPC Class Codes: B64G 1/34 using gravity gradient
• CPC Class Codes: B64G 1/361 using star sensors
• CPC Class Codes: B64G 1/369 using gyroscopes as attitude sensors
• CPC Class Codes: G01C 19/00 Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects

Abstract

A pseudo gyro emulates mechanical gyros by software processes by processing space system appendage measurement data and reaction wheel tachometer data within reference and control systems of a satellite using principals of conservation of momentum to compute the vehicular bus angular velocity rate data by accounting for the momentum transfer between the satellite, the bus, and the appendages for providing accurate relative vehicular position and angular velocity rate data as an integral part of attitude reference and control systems now having higher reliability, longer life times, lower power consumption, and more accurate vehicular angular velocity rate data generated within high bandwidth operations.

Claims

1. A pseudo gyro for generating vehicular angular velocity rate data for an attitude reference of a vehicular system providing momentum data, the pseudo gyro comprising,

an internal momentum generator for receiving the momentum data and for generating total internal momentum,

an inertia diadic generator for receiving the momentum data and for generating an inertia diadic,

a total system momentum propagator for receiving the velocity rate data and for propagating a total system momentum in body axes of the vehicular system, and

a bus rate generator for receiving the total system momentum, the inertia diadic and the total internal momentum and for computing the vehicular angular velocity rate data.

2. The pseudo gyro of claim 1 wherein the total system momentum propagator repetitively computes the total system momentum, and wherein the bus rate generator repetitively computes the vehicular angular velocity rate data.

3. The pseudo gyro of the claim 1 further comprising,

a total system momentum updater for receiving rate bias update data and for repetitively computing an updated system momentum, and

wherein the total system momentum propagator receives the updated system momentum for repetitively computing the total system momentum.

4. The pseudo gyro of claim 1 wherein the vehicular system further comprises attached appendages and a set of reaction wheels, all of which are for providing the momentum data.

5. The pseudo gyro of claim 1 wherein the vehicular system further provides torque data, the pseudo gyro further comprising,

a disturbance torque model representing an external torque source, and

a disturbance torque estimator for generating an external torque estimate from the disturbance torque model and from the torque data, wherein the total system momentum propagator receives the external torque estimate to propagate the total system momentum and repetitively computes the total system momentum.

6. The pseudo gyro of claim 1 wherein the vehicular system comprises a torque rod means for providing magnetic torque data for indicating a torque reaction of the vehicular system with external earth magnetic fields, the pseudo gyro further comprising,

a magnetic field model representing earth magnetic fields as an external torque source, and

a magnetic torque estimator for generating an external torque estimate from the magnetic torque model and from the magnetic torque data, wherein the total system momentum propagator receives the external torque estimate to update the total system momentum and repetitively computes the total system momentum, and wherein the external torque estimator computes external torques of earth magnetic fields as the external torque estimate.

7. A pseudo gyro for generating vehicular angular velocity rate data for an attitude reference of a vehicular system providing momentum data, the pseudo gyro comprising,

an internal momentum generator for receiving momentum data and for generating total internal momentum,

an inertia diadic generator for receiving the momentum data and for generating an inertia diadic,

a total system momentum propagator for receiving the velocity rate data and for generating a total system momentum in body axes of the vehicular system,

a bus rate generator for receiving the total system momentum, the inertia diadic, and the total internal momentum and for computing the vehicular angular velocity rate data,

a system momentum updater for receiving rate bias update data and for computing updated system momentum, wherein the total system momentum propagator receives the updated system momentum and repetitively computes the total system momentum, and wherein the bus rate generator repetitively computes the vehicular angular velocity rate data,

a magnetic field model for representing an earth magnetic field as a magnetic field external torque source,

an ephemeris model for calculating earth gravity gradients as a gravity gradient external torque source, and

a disturbance torque estimator for receiving torque rod data indicating an interaction of the vehicular system with the earth magnetic fields, for receiving the inertia diadic and for generating external torque estimates by applying the torque rod data to the magnetic field model and applying the inertia diadic to the ephemeris model, wherein the total system momentum propagator receives the external torque estimates for repetitively computing the total system momentum.

8. The pseudo gyro of claim 7 wherein,

the vehicular system has a plurality of attached appendages and a plurality of momentum storage devices,

the momentum data comprises a plurality of component momentum data respectively for the plurality of attached appendages and the plurality of momentum storage devices, and

the internal momentum generator computes the total internal momentum as a sum of the plurality of component momentum data.

9. The pseudo gyro of claim 7 wherein,

the updated system momentum from the total system momentum updater is the sum of the total system momentum from the total system momentum propagator plus the product of the inertia diadic and the rate bias update data, and

the total system momentum is repetitively recomputed after a predetermined time period by the total system momentum propagator, and the total system momentum is equal to the sum of a product of an attitude transformation matrix multiplied by the updated system momentum plus an integral of the external torque estimates from the disturbance torque estimator where the attitude transformation matrix is equal to an identity matrix minus a skew operator that is a function of the vehicular angular velocity rate data over the predetermined time period.

10. An attitude reference system for receiving momentum data and for repetitively computing vehicular attitude data referenced to star positions for estimating an attitude reference of a vehicular system having an attitude reference, the attitude reference system comprising,

a low frequency filter for receiving attitude measurement error data indicating the attitude reference of the vehicular system referenced to the star positions, and for generating rate bias update data and attitude update data within a high bandwidth of operation of the attitude reference system,

an attitude propagator for receiving vehicular angular velocity rate data and the attitude update data and for repetitively computing the vehicular attitude data, and

a pseudo gyro for receiving the momentum data, the rate bias update data and the attitude update data and for repetitively computing the vehicular angular velocity rate data, the pseudo gyro comprising:

a) an internal momentum generator for receiving momentum data and for generating total internal momentum;

b) an inertia diadic generator for receiving the momentum data and generating an inertia diadic;

c) a momentum propagator for receiving the vehicular angular velocity rate data and for generating a total system momentum in body axes of the vehicular system; and

d) a bus rate generator for receiving the total system momentum, the inertia diadic and the total internal momentum and for computing the vehicular angular velocity rate data.

11. The attitude reference system of claim 10 further comprising,

a star tracker for tracking stars within a sensory field of view for generating measured star vectors referencing the star positions of tracked stars to the attitude reference of the vehicular system,

a star identification processor for receiving the measured star vectors and for generating identified star data indicating identified stars within a star catalog, and

a star tracking processor for tracking the identified stars and generating the star measurement error indicating the difference between the attitude reference of the vehicular system and the computed vehicular attitude data.

12. The attitude reference system of claim 10 wherein the pseudo gyro further comprises,

a system momentum updater for receiving the rate bias update data and for computing updated total system momentum, wherein the total system momentum propagator receives the updated total system momentum and repetitively computes the total system momentum, and wherein the bus rate generator repetitively computes the vehicular angular velocity rate data.

13. The attitude reference system of claim 10 wherein the vehicular system has a plurality of attached appendages and a plurality of momentum storage devices for providing the momentum data, the pseudo gyro further comprising,

a system momentum updater for receiving the rate bias update data and for computing updated total system momentum, wherein the total system momentum propagator receives the updated total system momentum and repetitively computes the total system momentum, wherein the bus rate generator repetitively computes the vehicular angular velocity rate data, wherein the momentum data comprises a plurality of component momentum data respectively for the plurality of attached appendages and the plurality of momentum storage devices, wherein the internal momentum generator computes the total internal momentum as a sum of the plurality of component momentum data, wherein the updated system momentum from the total system momentum updater is the sum of the total system momentum from the total system momentum propagator plus the product of the inertia diadic and the rate bias update data, and wherein the total system momentum is repetitively recomputed after a predetermined time period by the total system momentum propagator and is equal to the sum of a product of an attitude transformation matrix multiplied by the updated system momentum plus an integral of the external torque estimates from the disturbance torque estimator where the attitude transformation matrix is equal to an identity matrix minus a skew operator that is a function of the vehicular angular velocity rate data over the predetermined time period.

14. The attitude reference system of claim 10 wherein the vehicular system has a plurality of attached appendages and a plurality of reaction wheels for storing momentum and the attached appendages and the plurality of reaction wheels provide the momentum data, the pseudo gyro further comprising,

a system momentum updater for receiving the rate bias update data and for computing updated total system momentum, wherein the total system momentum propagator receives the update total system momentum and repetitively computes the total system momentum, wherein the bus rate generator repetitively computes the vehicular angular velocity rate data, wherein the momentum data comprises a plurality of component momentum data respectively for the plurality of attached appendages and the plurality of reaction wheels, wherein the internal momentum generator computes the total internal momentum as a sum of the plurality of component momentum data, wherein the updated system momentum from the total system momentum updater is the sum of the total system momentum from the total system momentum propagator plus the product of the inertia diadic and the rate bias update data, and wherein the total system momentum is repetitively recomputed after a predetermined time period by the total system momentum propagator and is equal to the sum of a product of an attitude transformation matrix multiplied by the updated system momentum plus an integral of the external torque estimates from the disturbance torque estimator where the attitude transformation matrix is equal to an identity matrix minus a skew operator that is as a function of the vehicular angular velocity rate data over the predetermined time period.

15. The attitude reference system of claim 10 wherein the vehicular system has a plurality of attached appendages comprising a solar cell panel and a communication gimballed assembly and a plurality of reaction wheels, wherein the attached appendages and the plurality of reaction wheels are for providing the momentum data, the pseudo gyro further comprising,

a system momentum updater for receiving the rate bias update data and for computing updated total system momentum, wherein the total system momentum propagator receives the update total system momentum and repetitively computes the total system momentum, wherein the bus rate generator repetitively computes the vehicular angular velocity rate data, wherein the momentum data comprises a plurality of component momentum data respectively for the plurality of attached appendages and the plurality of reaction wheels, wherein the internal momentum generator computes the total internal momentum as a sum of the plurality of component momentum data, wherein the updated system momentum from the total system momentum updater is the sum of the total system momentum from the total system momentum propagator plus the product of the inertia diadic and the rate bias update data, and wherein the total system momentum is repetitively recomputed after a predetermined time period by the total system momentum propagator and is equal to the sum of a product of an attitude transformation matrix multiplied by the updated system momentum plus an integral of the external torque estimates from the disturbance torque estimator where the attitude transformation matrix is equal to an identity matrix minus a skew operator that is a function of the vehicular angular velocity rate data over the predetermined time period.

16. The attitude reference system of claim 15 wherein,

the attitude transformation matrix indicates an angle of rotation since the last computation of the vehicular attitude data, and

the identity matrix plus the skew operator transforms the system total momentum through the angle of rotation.

17. The attitude reference system of claim 10 wherein the vehicular system further provides torque data, the pseudo gyro further comprises,

a disturbance torque model representing an external torque source, and

a torque estimator for receiving the torque data and for generating an external torque estimate from the disturbance torque model and from the torque data, wherein the total system momentum propagator receives the estimated external torque for updating the total system momentum and for repetitively computing the total system momentum.

18. The attitude reference system of claim 10 wherein the vehicular system comprises a torque rod means for providing magnetic torque data for indicating a torque reaction of the vehicular system with external earth magnetic fields, the pseudo gyro further comprising,

a magnetic field model representing an earth magnetic fields as a magnetic field external torque source,

an ephemeris model representing earth gravity gradients as a gravity gradient external torque source, and

a disturbance torque estimator for receiving torque rod data indicating an interaction of the vehicular system with the earth magnetic fields, for receiving the inertia diadic and for generating external torque estimates by applying the torque rod data to the magnetic field model and applying the inertia diadic to the ephemeris model, wherein the total system momentum propagator receives the external torque estimates for updating the total system momentum and for repetitively computing the total system momentum.

19. The attitude reference system of claim 10 wherein the low frequency filter is a Kalman filter.