Concurrent station keeping, attitude control, and momentum management of spacecraft

Patent metadata

Field	Value
Publication number	US-10180686-B2
Application number	US-201615072861-A
Country	US
Kind code	B2
Filing date	Mar 17, 2016
Priority date	Mar 17, 2016
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

An operation of a spacecraft is controlled using an inner-loop control determining first control inputs for momentum exchange devices to control an orientation of the spacecraft and an outer-loop control determining second control inputs for thrusters of the spacecraft to concurrently control a pose of the spacecraft and a momentum stored by the momentum exchange devices of the spacecraft. The outer-loop control determines the second control inputs using a model of dynamics of the spacecraft including dynamics of the inner-loop control, such that the outer-loop control accounts for effects of actuation of the momentum exchange devices according to the first control inputs determined by the inner-loop control. The thrusters and the momentum exchange devices are controlled according to at least a portion of the first and the second control inputs.

First claim

The invention claimed is:

1. A method for controlling an operation of a spacecraft, comprising:
determining, using an inner-loop control, first control inputs for momentum exchange devices to control an orientation of the spacecraft;
determining, using an outer-loop control, second control inputs for thrusters of the spacecraft to concurrently control a pose of the spacecraft and a momentum stored by the momentum exchange devices of the spacecraft, wherein the outer-loop control determines the second control inputs using a model of dynamics of the spacecraft, wherein the model includes dynamics of the inner-loop control, such that the outer-loop control accounts for effects of actuation of the momentum exchange devices according to the first control inputs determined by the inner-loop control; and
controlling the thrusters and the momentum exchange devices according to at least a portion of the first and the second control inputs, wherein steps of the method are performed by a processor.

2. The method of claim 1 , wherein the outer-loop control is a model predictive control (MPC) that optimizes a cost function over a receding horizon subject to constraints on the pose of the spacecraft and constraints on inputs to the thrusters, wherein the cost function includes components for controlling the pose of the spacecraft and the momentum stored by the momentum exchange devices.

3. The method of claim 2 , wherein the constraints on the inputs to the thrusters define a range of rotations of the thrusters located on a single face of the spacecraft.

4. The method of claim 3 , wherein the range of rotations forces thrusts of the thrusters to lie within an interior of a pyramid formed by gimbal angles of the thrusters.

5. The method of claim 2 , wherein the constraints on the pose of the spacecraft include a position constraint maintaining a position of the spacecraft within a predetermined window and an orientation constraint maintaining Euler Angles of the spacecraft within a predetermined limit, and wherein the constraints on the inputs to the thrusters guarantees an ability of the thrusters to jointly generate a force for controlling the pose of the spacecraft and a torque for unloading the momentum stored by the momentum exchange devices of the spacecraft.

6. The method of claim 2 , further comprising:
determining the cost function as a combination of multiple components including a component for a position of the spacecraft penalizing a displacement of the spacecraft from a desired position, a component for an attitude of the spacecraft penalizing larger values of Euler Angles of the spacecraft, a component for the stored momentum penalizing a larger value of a magnitude of the stored momentum, a component for an objective of the operation of the spacecraft, and a component ensuring a stability of the operation of the spacecraft.

7. The method of claim 6 , further comprising:
weighting each of the components of the cost function, such that the optimization of the cost function produces control inputs that achieve goals of each individual component with priority corresponding to their relative weight.

8. The method of claim 7 , wherein the control inputs are determined iteratively, and wherein at least one iteration comprises:
updating one or combination of the components of the cost function and weights of the components of the cost function based on a change of a desired operation of the spacecraft.

9. The method of claim 2 , wherein model of dynamics of the spacecraft includes a nominal model defining relationships among parameters of the model and a disturbance model defining disturbance forces acting on the spacecraft, further comprising:
performing a linearization of the nominal model as if the spacecraft is located at a target position for the entire period of the receding horizon; and
determining the disturbance forces as if the spacecraft is located at the target position for the entire period of the receding horizon.

10. The method of claim 1 , wherein the controlling includes commanding the momentum exchange devices to unload the stored momentum and commanding to the thrusters to generate a force and a torque to maintain or change the pose of the spacecraft and compensate for a torque generated by the momentum exchange devices unloading the stored momentum.

11. The method of claim 10 , wherein the second control inputs determined by the outer-loop control specify gimbal angles and propulsion thrusts of the thrusters, and wherein the first control inputs determined by the inner-loop control specify control inputs to unload the momentum exchange devices.

12. The method of claim 1 , wherein the inner-loop control reduces an error between the orientation of the spacecraft and a target orientation of the spacecraft.

13. The method of claim 1 , the second control inputs force the inner loop control to reduce speed of the momentum exchange devices.

14. A control system for controlling an operation of a spacecraft according to a model of the spacecraft, comprising at least one processor for executing modules of the control system, the modules comprising:
an inner-loop controller for determining first control inputs to momentum exchange devices for controlling an orientation of the spacecraft;
an outer-loop controller for determining second control inputs to thrusters of the spacecraft for concurrently controlling a pose of the spacecraft and a momentum stored by the momentum exchange devices of the spacecraft, wherein the outer-loop controller determines the second control inputs using a model of dynamics of the spacecraft, wherein the model includes dynamics of the inner-loop control, such that the outer-loop controller accounts for effects of actuation of the momentum exchange devices according to the first control inputs determined by the inner-loop controller; and
a mapper for controlling the thrusters and the momentum exchange devices according to at least a portion of the first and the second control inputs, wherein the controlling includes commanding to the momentum exchange devices to unload the stored momentum and commanding to the thrusters to generate a force and a torque to maintain or change the pose of the spacecraft and to compensate for a torque generated by the momentum exchange devices unloading the stored momentum.

15. The control system of claim 14 , wherein the outer-loop controller uses a model predictive control (MPC) that optimizes a cost function over a receding horizon subject to constraints on the pose of the spacecraft and constraints on inputs to the thrusters, wherein the cost function includes components for controlling the pose of the spacecraft and the momentum stored by the momentum exchange devices, and wherein the inner-loop controller reduces an error between the orientation of the spacecraft and a target orientation of the spacecraft.

16. The control system of claim 15 , wherein the cost function includes a weighted combination of multiple components including a component for a position of the spacecraft penalizing a displacement of the spacecraft from a desired position, a component for an attitude of the spacecraft penalizing larger values of Euler Angles of the spacecraft, a component for the stored momentum penalizing a larger value of a magnitude of the stored momentum, a component for an objective of the operation of the spacecraft, and a component ensuring a stability of the operation of the spacecraft.

17. The control system of claim 14 , wherein the control inputs are determined iteratively, and wherein for at least one iteration, the

Assignees

• Mitsubishi Electric Res Laboratories Inc

Inventors

• Weiss Avishai
• Di Cairano Stefano
• Walsh Alex

Classifications

• B64G1/28 Primary

  using inertia or gyro effect · CPC title

• B64G1/285

  using momentum wheels · CPC title

• B64G1/283

  using reaction wheels · CPC title

• B64G1/286

  using control momentum gyroscopes (CMGs) · CPC title

• G05D1/0883 Primary

  Physics · mapped topic