Satellite harmonic torque estimator
AssigneeSpace Systems/Loral, Inc.
InventorsLawrence McGovern, Xen Price
Life of this patent
Estimating the term…
Abstract
A spacecraft embedded in a reference frame rotating relative to inertial space. The spacecraft generally includes actuators for maneuvering the spacecraft with respect to the reference frame, an attitude measurement device that measures the pitch and roll attitude of the spacecraft with respect to the reference frame, a control device adapted to keep the roll and pitch angles of the spacecraft close to the commanded roll and pitch angles, and a harmonic torque estimator adapted to read the commanded angular velocity of the spacecraft relative to an inertial frame, read momentum wheel speeds, read known predicted external torques and combine angular velocity, measured wheel speed and known external torque to produce an estimated observable periodic torque.
Claims23
A spacecraft embedded in a reference frame rotating relative to inertial space comprising:
- actuators for maneuvering the spacecraft with respect to the reference frame;
- an attitude measurement device that measures the pitch and roll attitude of the spacecraft with respect to the reference frame;
- a control device adapted to keep the roll and pitch angles of the spacecraft close to the commanded roll and pitch angles;
- and
- a harmonic torque estimator adapted to read the commanded angular velocity of the spacecraft relative to an inertial frame, read momentum wheel speeds, read known predicted external torques and combine angular velocity, measured wheel speed and known external torque to produce an estimated observable periodic torque.
An attitude control system for a spacecraft comprising:
- a harmonic torque estimator adapted to estimate a periodic disturbance torque signal and a periodic momentum profile signal based on disturbances observable from the available spacecraft sensors;
- an attitude profile generator adapted to provide reference attitude command and a rate command for the spacecraft to follow;
- a feedback control device adapted to measure roll and pitch angles to the commanded roll and pitch angles issued by the attitude profile generator and output a torque that is combined with the periodic disturbance torque estimate to form an actuator torque command;
- and
- a momentum management device adapted to use the estimated periodic momentum profile to improve momentum management of the spacecraft.
A method of controlling a spacecraft comprising the steps of:
- measuring a pitch and roll attitude of the spacecraft;
- generating a control torque command designed to keep the roll and pitch angles close to desired roll and pitch angles;
- and
- estimating an observable periodic disturbance torque by combining a measured angular velocity, measured wheel speed and known external torques;
- and
- combining the generated control torque command and the estimated observable periodic torque to produce an actuator torque command.
A method of controlling a spacecraft comprising the steps of:
- measuring a pitch and roll attitude of the spacecraft;
- generating a control torque command designed to keep roll and pitch angles close to desired roll and pitch angles;
- estimating Fourier coefficients of a periodic disturbance torque and evaluating a Fourier series of the estimated Fourier coefficients to produce an estimated periodic torque;
- and
- combining the generated control torque command and the estimated periodic torque to produce an actuator torque command.
Dependencies are inferred from the claim text.