Nonlinear model predictive control of coupled celestial system

Patent metadata

Field	Value
Publication number	US-11292618-B2
Application number	US-201916502186-A
Country	US
Kind code	B2
Filing date	Jul 3, 2019
Priority date	Jul 3, 2019
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

A controller controls a spacecraft to rendezvous a non-center-of-mass point of the controlled spacecraft with a non-center-of-mass point of an uncontrolled celestial body. The controlled spacecraft and the uncontrolled celestial body form a multi-object celestial system, and the controller produces control commands to thrusters of the controlled spacecraft using a non-linear model predictive control (NMPC) optimizing a cost function over a receding horizon that minimizes an error between coordinates of the non-center-of-mass point of the spacecraft and the non-center-of-mass point of the celestial body subject to joint dynamics of the multi-object celestial system coupled with joint kinematics of the multi-object celestial system.

First claim

What is claimed is:

1. A controller to control a spacecraft to rendezvous a non-center-of-mass point of the controlled spacecraft with a non-center-of-mass point of an uncontrolled celestial body, wherein the controlled spacecraft and the uncontrolled celestial body form a multi-object celestial system, the controller comprising:
an input interface configured to accept data indicative of current values of states of the controlled spacecraft and the uncontrolled celestial body in the multi-object celestial system, wherein the states includes one or combination of positions, orientations, and translational and angular velocities of the controlled spacecraft and the uncontrolled celestial body, and perturbations acting on the multi-object celestial system;
a processor configured to produce control commands to thrusters of the controlled spacecraft using a non-linear model predictive control (NMPC) optimizing a cost function over a receding horizon that minimizes an error between coordinates of the non-center-of-mass point of the spacecraft and the non-center-of-mass point of the celestial body subject to joint dynamics of the multi-object celestial system coupled with joint kinematics of the multi-object celestial system; and
an output interface configured to submit the control commands to the thrusters of the spacecraft.

2. The controller of claim 1 , wherein the cost function is optimized subject to input constraints to enforce gimbal angle limits and magnitude limits on the thrusters and subject to output constraints to enforce a line-of-sight (LOS) regulation of the non-center-of-mass points.

3. The controller of claim 1 , wherein the cost function includes a stage cost integrated along a prediction horizon and a terminal cost expressed on the state of the controlled spacecraft at the end of the prediction horizon to encode control objectives of the controlled spacecraft to have zero position and attitude errors of the non-center-of-mass point of the controlled spacecraft with respect to the non-center-of-mass point of the uncontrolled celestial body with the translational and angular velocities of the controlled spacecraft matching the translational and angular velocities of the uncontrolled celestial body.

4. The controller of claim 1 , wherein the dynamics and kinematics of the uncontrolled celestial body are embedded into the dynamics and kinematics of the controlled spacecraft to form the joint multi-object celestial system controllable via the NMPC as a closed-loop regulation problem of the error coordinates between the non-center-of-mass point on the controlled spacecraft and the non-center-of-mass point on the celestial body.

5. The controller of claim 4 , wherein embedding of the dynamics and kinematics of the uncontrolled celestial body into the dynamics and kinematics of the controlled spacecraft represents joint dynamics and kinematics of a relative attitude-error and a relative translational-error between the controlled spacecraft and the uncontrolled celestial body.

6. The controller of claim 1 , wherein a spatial distance between the non-center-of-mass points of the controlled spacecraft and the uncontrolled celestial body is a function of a spatial distance between centers of mass of the uncontrolled celestial body and the controlled spacecraft, an orientation of the uncontrolled celestial body, and an orientation of the controlled spacecraft.

7. The controller of claim 1 , wherein the controlled spacecraft is a rectangular satellite equipped with eight thrusters mounted on corners of two faces of the satellite.

8. A spacecraft comprising:
a set of thrusters for changing a pose of the spacecraft; and
the controller of claim 1 configured to produce the control commands for controlling the thrusters.

9. The spacecraft of claim 8 , wherein the spacecraft has a rectangular shape and equipped with eight thrusters mounted on corners of two faces of the satellite, wherein the constraints on the inputs to the thrusters define a range of rotations of the thrusters forcing thrusts of the thrusters to lie within an interior of a pyramid.

10. A method for controlling a spacecraft to rendezvous a non-center-of-mass point of the controlled spacecraft with a non-center-of-mass point of an uncontrolled celestial body, wherein the controlled spacecraft and the uncontrolled celestial body form a multi-object celestial system, wherein the method uses a processor coupled with stored instructions implementing the method, wherein the instructions, when executed by the processor carry out steps of the method, comprising:
accepting data indicative of current values of states of the controlled spacecraft and the uncontrolled celestial body in the multi-object celestial system, wherein the states includes one or combination of positions, orientations, and translational and angular velocities of the controlled spacecraft and the uncontrolled celestial body, and perturbations acting on the multi-object celestial system;
producing control commands to thrusters of the controlled spacecraft using a non-linear model predictive control (NMPC) optimizing a cost function over a receding horizon that minimizes an error between coordinates of the non-center-of-mass point of the spacecraft and the non-center-of-mass point of the celestial body subject to joint dynamics of the multi-object celestial system coupled with joint kinematics of the multi-object celestial system; and
submitting the control commands to the thrusters of the spacecraft.

11. The method of claim 10 , wherein the cost function is optimized subject to input constraints to enforce gimbal angle limits and magnitude limits on the thrusters and subject to output constraints to enforce a line-of-sight (LOS) regulation of the non-center-of-mass points.

12. The method of claim 10 , wherein the cost function includes a stage cost integrated along a prediction horizon and a terminal cost expressed on the state of the controlled spacecraft at the end of the prediction horizon to encode control objectives of the controlled spacecraft to have zero position and attitude errors of the non-center-of-mass point of the controlled spacecraft with respect to the non-center-of-mass point of the uncontrolled celestial body with the translational and angular velocities of the controlled spacecraft matching the translational and angular velocities of the uncontrolled celestial body.

13. The method of claim 10 , wherein the dynamics and kinematics of the uncontrolled celestial body are embedded into the dynamics and kinematics of the controlled spacecraft to form the joint multi-object celestial system controllable via the NMPC as a closed-loop regulation problem of the error coordinates between the non-center-of-mass point on the controlled spacecraft and the non-center-of-mass point on the celestial body.

14. The method of claim 13 , wherein embedding of the dynamics and kinematics of the uncontrolled celestial body into the dynamics and kinematics of the controlled spacecraft represents joint dynamics and kinematics of a relative attitude-error and a relative translational-error between the controlled spacecraft and the uncontrolled celestial body.

15. The method of claim 10 , wherein a spatial distance between the non-center-of-mass points of the controlled spacecraft and the uncontrolled celestial body is a function of a spatial distance between centers of mass of the uncontrolled celestial body and the controlled spacecraft, an orientation of the uncontrolled celestial body, and an orientation of the controlled spacecraft.

Assignees

• Mitsubishi Electric Res Laboratories Inc

Inventors

• Weiss Avishai
• Di Cairano Stefano
• Malladi Bharaniprabha

Classifications

• B64G1/242 Primary

  Orbits and trajectories · CPC title

• B64G1/262

  having adjustable angles, e.g. gimbaled thrusters · CPC title

• B64G1/646

  Docking or rendezvous systems (refuelling in space B64G1/4024) · CPC title

• B64G1/1081

  for debris removal · CPC title

• B64G1/36

  using sensors, e.g. sun-sensors, horizon sensors · CPC title