Attitude determination and control system based on a quaternion kalman filter and method thereof

Abstract

This patent presents an attitude determination and control system based on a Quaternion Kalman Filter (QKF) with an extendable number of sensors and actuators. Furthermore, it is compatible with the spherical motor as its attitude actuator. The system includes a processor with a QKF, at least one direct attitude actuator, and at least two environmental sensors. Firstly, system dynamics calculates a first propagation attitude determination result. Next, update the first propagation with the attitude sensor measurements. Then, control the satellite's attitude via the attitude actuator closer to the attitude command provided by the user. The proposed system dynamic model could adjust the number of actuators and sensors freely without reprogramming the algorithms for new missions with new configurations on the actuators and sensors. Moreover, if some components fail, the algorithm can automatically remove those related sequences to avoid the overall failure of the system.

What is claimed is: 
     
         1 . An attitude control system based on a Quaternion Kalman Filter (QKF) for controlling the attitude of a satellite, including:
 a controller for receiving an attitude command from a user to generate a torque-input command for the attitude actuator;   an attitude actuator for outputting torque according to a torque-control command from the controller to change the attitude of the satellite, wherein the attitude actuator may be capable of measuring its output torque via sensors;   a 1 st  to N th  environmental sensor for measuring a 1 st  to M th  target to obtain a 1 st  to N th  measured value of environmental sensor (measured value) at time t, wherein both N and M are integers greater than or equal to 2, and M is a positive integer less than or equal to N; and   a processor having a QKF, wherein the processor connects to the controller, the attitude actuator, and the 1 st  to the N th  environmental sensor, wherein the processor is for:
 obtaining a first propagation attitude determination result by performing a calculation according to at least one selected from the group consisting of the torque-input command from the controller and the measured output torque; and 
 obtaining a second propagation result by performing a calculation according to the 1 st  to the N th  measured value and updating the first propagation result. 
   
     
     
         2 . The attitude control system, according to  claim 1 , further including at least one selected from the group consisting of an inertia measurement unit and an attitude measurement unit, wherein the inertia measurement unit is for measuring the inertia status, and the attitude measurement unit is for directly measuring the attitude to obtain attitude information;
 wherein in a condition that the satellite attitude control system includes the inertia measurement unit, the processor furtherly connects to the inertia measurement unit, and the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the “torque-input command from the controller and the measured output torque,” and according to the inertia information;   wherein in a condition that the attitude control system includes the attitude measurement unit, the processor furtherly connects to the attitude measurement unit, and the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the “torque-input command from the controller and the measured of output torque,” and the attitude information.   
     
     
         3 . An attitude determination method based on a Quaternion Kalman Filter (QKF) for determining an attitude of a satellite, including:
 a propagate stage including:
 obtaining a first propagation result, by using a processor having a QKF, to perform a calculation according to at least one selected from the group consisting of the torque-input command from the controller and a measured output torque on the attitude actuator”; and 
   an update stage including:
 measuring a 1 st  to M th  target to obtain a 1 st  to N th  measured value by using a 1 st  to an N th  environmental sensor, wherein both N and M are integers greater than or equal to 2, and M is a positive integer less than or equal to N; and 
 obtaining a second propagation result by using the processor to perform a calculation according to the 1 st  to the N th  measured value and updating the first propagation result. 
   
     
     
         4 . The attitude determination method according to  claim 3 , wherein the propagate stage further includes at least one step selected from the group consisting of measuring inertia of the satellite to obtain inertia information by using an inertia measurement unit and measuring the attitude of the satellite to obtain an attitude information by using an attitude measurement unit;
 wherein in a condition that the propagate stage further includes a step of measuring the inertia of the satellite to obtain the inertia information by using the inertia measurement unit, the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the “torque-input command from the controller, and the measured output torque” and the inertia information;   wherein in a condition that the propagate stage further includes a step of measuring the attitude of the satellite to obtain the attitude information by using the attitude measurement unit, the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the torque-input command from the controller and the measured output torque” and the attitude information.   
     
     
         5 . An attitude control method based on a Quaternion Kalman Filter (QKF) for controlling an attitude of a satellite, including:
 a propagate stage including:
 receiving an attitude command from a user; and 
 obtaining a first propagation result, by using a processor having a QKF, to perform a calculation according to at least one selected from the group consisting of torque-input command from the controller and the measured output torque; 
   an update stage including:
 measuring a 1 st  to M th  target to obtain a 1 st  to N th  measured value by using a 1 st  to N th  environmental sensor, wherein both N and M are integers greater than or equal to 2, and M is a positive integer less than or equal to N; and 
   obtaining a second propagation result by using the processor to perform a calculation according to the 1 st  to the N th  measured value and updating the first propagation result; and   a control stage including:
 obtaining a torque-control command by using the processor to perform a calculation for compensation purposes according to the attitude command and the second propagation result; and 
 altering the satellite's attitude using the attitude actuator to output torque to the satellite according to the torque-control command. 
   
     
     
         6 . The satellite attitude control method according to  claim 5 , wherein the propagate stage further includes at least one step selected from the group consisting of measuring inertia of the satellite to obtain inertia information by using an inertia measurement unit, and measuring the attitude of the satellite to obtain attitude information by using an attitude measurement unit;
 wherein in a condition that the propagate stage further includes a step of measuring the inertia of the satellite to obtain the inertia information by using the inertia measurement unit, the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the “torque-input command from the controller and the measured output torque,” and the inertia information;   wherein in a condition that the propagate stage further includes a step of measuring the attitude of the satellite to obtain the attitude information by using the attitude measurement unit, the processor is for obtaining the first propagation result by performing a calculation according to at least one selected from the group consisting of the “torque-input command from the controller and the measured value of output torque” and the attitude information.   
     
     
         7 . The attitude control system according to  claim 1 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         8 . The attitude control system according to  claim 2 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         9 . The attitude determination method according to  claim 3 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         10 . The attitude determination method according to  claim 4 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         11 . The attitude control method according to  claim 5 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         12 . The attitude control method according to  claim 6 , wherein the attitude actuator further includes: at least one direct attitude actuator and at least one indirect attitude actuator. 
     
     
         13 . The attitude control system according to  claim 1 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode. 
     
     
         14 . The attitude control system according to  claim 2 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode. 
     
     
         15 . The attitude determination method according to  claim 3 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode. 
     
     
         16 . The attitude determination method according to  claim 4 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode. 
     
     
         17 . The attitude control method according to  claim 5 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode. 
     
     
         18 . The attitude control method according to  claim 6 , wherein the attitude actuator includes an indirect attitude actuator, and the indirect attitude actuator could be a spherical motor, and the controller of the control system has at least three control modes: a de-tumbling mode, a de-saturation mode, and a fine-pointing mode.