Projectile 3D attitude from 3-axis magnetometer and single-axis accelerometer
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
F42B-015/01
G06F-019/00
F42B-015/00
출원번호
US-0916936
(2010-11-01)
등록번호
US-8344303
(2013-01-01)
발명자
/ 주소
Elgersma, Michael R.
Bageshwar, Vibhor L.
출원인 / 주소
Honeywell International Inc.
대리인 / 주소
Fogg & Powers LLC
인용정보
피인용 횟수 :
3인용 특허 :
19
초록▼
A method to determine roll angle, pitch angle, and heading angle of a spinning projectile during a flight of the spinning projectile is provided. The method includes providing a magnetic unit vector in an inertial frame of the projectile at a projectile launch location prior to launch of the project
A method to determine roll angle, pitch angle, and heading angle of a spinning projectile during a flight of the spinning projectile is provided. The method includes providing a magnetic unit vector in an inertial frame of the projectile at a projectile launch location prior to launch of the projectile; determining a magnetic unit vector in a body frame and in an inertial frame of the spinning projectile during the flight of the spinning projectile; determining a velocity unit vector in the body frame and in the inertial frame of the spinning projectile during the flight of the spinning projectile; and calculating the roll angle, the pitch angle, and the heading angle of the spinning projectile during the flight of the spinning projectile, regardless of the spin rate of the projectile. The roll angle and the pitch angle of the spinning projectile form an attitude of the spinning projectile.
대표청구항▼
1. A method to determine roll angle, pitch angle, and heading angle of a spinning projectile during a flight of the spinning projectile, the method comprising: providing a magnetic unit vector in an inertial frame of the projectile at a projectile launch location prior to launch of the projectile;de
1. A method to determine roll angle, pitch angle, and heading angle of a spinning projectile during a flight of the spinning projectile, the method comprising: providing a magnetic unit vector in an inertial frame of the projectile at a projectile launch location prior to launch of the projectile;determining a magnetic unit vector in a body frame and in an inertial frame of the spinning projectile during the flight of the spinning projectile;determining a velocity unit vector in the body frame and in the inertial frame of the spinning projectile during the flight of the spinning projectile; andcalculating the roll angle, the pitch angle, and the heading angle of the spinning projectile during the flight of the spinning projectile, regardless of the spin rate of the projectile, wherein the roll angle and the pitch angle of the spinning projectile comprise an attitude of the spinning projectile. 2. The method of claim 1, wherein determining the magnetic unit vector in the body frame and in the inertial frame of the spinning projectile comprises: measuring a body-axis magnetic vector using a three-axis magnetometer during the flight of the projectile; andexecuting algorithms at a processor on board the projectile, wherein the algorithms use the magnetic unit vector in the inertial frame at the projectile launch location. 3. The method of claim 1, wherein determining the velocity unit vector in the body frame and in the inertial frame of the spinning projectile comprises: measuring a specific force using a single-axis accelerometer having a sense axis aligned with a spin axis of the spinning projectile; anddetermining a flight path angle as a function of time for the spinning projectile based on the measured specific force. 4. The method of claim 3, further comprising: applying a low-pass filter to an output of the single-axis accelerometer to estimate drag on the spinning projectile; anddetermining a magnitude of a velocity vector, wherein the determining the flight path angle is based on the determined magnitude of the velocity vector. 5. The method of claim 3, wherein the determining the velocity unit vector in the inertial frame is based on the determined flight path angle, the method further comprising: solving for the velocity unit vector as an intersection of a unit sphere and two planes, wherein a line formed from the two intersecting planes intersects the unit sphere in two points;selecting one of the two points based on a direction of launch of the projectile; andcalculating the parameters of the line intersecting the unit sphere. 6. The method of claim 5, further comprising: assuming the velocity unit vector in the inertial frame is parallel to the angular velocity unit vector in the body frame;applying a high-pass filter to an output of the single-axis accelerometer;calculating the time derivative of the local Earth magnetic field vector in the inertial frame and the body frame;generating the angular velocity unit vector in the body frame based on output from the high-pass filter and the time derivatives of the local Earth magnetic field vector; anddetermining a direction of the velocity unit vector in the body frame based on the generated angular velocity unit vector in the body frame. 7. The method of claim 1, wherein calculating the roll angle, the pitch angle, and the heading angle of the spinning projectile comprises: generating a direction cosine matrix by matching the magnetic unit vector and the velocity unit vector in the body frame with the magnetic unit vector and the velocity unit vector in the inertial frame;solving Wahba's problem for the direction cosine matrix; andcalculating the roll angle, the pitch angle, and the heading angle from the direction cosine matrix, wherein the correct solution to Wahba's problem is the roll angle, the pitch angle, and the heading angle of the spinning projectile. 8. The method of claim 1, further comprising: aligning a sense axis of a single-axis accelerometer with a spin axis of the spinning projectile;filtering output from the single-axis accelerometer to determine drag acting on the spinning projectile;determining a magnitude of the velocity unit vector of the spinning projectile; anddetermining an angular velocity unit vector of the spinning projectile. 9. The method of claim 8, wherein filtering output from the single-axis accelerometer includes filtering output from the single-axis accelerometer positioned on the spinning projectile spinning at a spin rate greater than 100 revolutions per second. 10. The method of claim 1, further comprising orienting a sense axis of a single-axis accelerometer parallel to a spin axis of the projectile prior to launch of the projectile. 11. The method of claim 1, wherein calculating the roll angle, the pitch angle, and the heading angle of the spinning projectile includes calculating the roll angle, the pitch angle, and the heading angle of the projectile spinning more than 100 revolutions per second. 12. An apparatus to measure a three-dimensional attitude of a spinning projectile during a flight of the spinning projectile, the apparatus including: a three-axis magnetometer to measure the magnetic field of earth;a single-axis accelerometer having a sense axis parallel to a spin axis of the spinning projectile during the flight of the spinning projectile; andan attitude estimator module;at least one processor to receive outputs from the three-axis magnetometer and the single-axis accelerometer and to execute at least one algorithm in the attitude estimator module to determine an attitude and heading angle of the spinning projectile during the flight of the spinning projectile, regardless of a spin rate of the projectile, based on outputs from the three-axis magnetometer and the single-axis accelerometer, wherein the attitude and the heading angle comprise the three-dimensional attitude. 13. The apparatus of claim 12, further comprising a Kalman filter to receive output from the attitude estimator module, wherein the Kalman filter computes estimates of the attitude and the heading angle of the spinning projectile. 14. The apparatus of claim 12, wherein the attitude estimator receives from the three-axis magnetometer information indicative of a local Earth magnetic field vector at the projectile launch site prior to launch, and wherein the attitude estimator module includes the at least one algorithm to: use a low-pass filter on accelerometer measurements to compute the drag acting on the projectile;estimate a velocity unit vector in the inertial frame;estimate a velocity unit vector in the body frame;generate two 3×3 unit vector matrices;invert one 3×3 unit vector matrix;multiply one 3×3 unit vector matrix with the inverted 3×3 unit vector matrix to solve for Wahba's problem; anduse a singular value decomposition to generate a direction cosine matrix from the direction cosine matrix calculated to solve Wahba's problem in order to enforce orthogonality constraints on the direction cosine matrix calculated to solve Wahba's problem. 15. The apparatus of claim 12, further comprising a Kalman filter communicatively coupled to receive output from the attitude estimator module. 16. A non-transitory computer readable medium embodying a program of instructions executable by a processor to perform a method comprising: determining a magnetic unit vector in a body frame and in an inertial frame of the spinning projectile during a flight of the spinning projectile;determining a velocity unit vector in the body frame and in the inertial frame of the spinning projectile during the flight of the spinning projectile; andcalculating a roll angle, a pitch angle, and a heading angle of the spinning projectile during the flight of the spinning projectile, regardless of a spin rate of the projectile, wherein the roll angle, the pitch angle, and the heading angle of the spinning projectile comprise a three-dimensional attitude of the spinning projectile. 17. The medium of claim 16, comprising the program of instructions executable by the processor to perform the method, which further comprises: solving for the velocity unit vector in the inertial frame as an intersection of a unit sphere and two planes, wherein a line formed from the two intersecting planes intersects the unit sphere in two points;selecting one of the two points based on a direction of launch of the projectile; andcalculating parameters of the line intersecting the unit sphere. 18. The medium of claim 17, comprising the program of instructions executable by the processor to perform the method, which further comprises: applying a high-pass filter to an output of the single-axis accelerometer;calculating the time derivative of the local Earth magnetic field vector in the inertial frame and the body framegenerating the angular velocity unit vector in the body frame based on output from the high-pass filter and the time derivatives of the local Earth magnetic field vector; anddetermining a direction of the velocity unit vector in the body frame based on the generated angular velocity unit vector in the body frame, wherein the velocity unit vector in the body frame is assumed to be parallel to the angular unit velocity in the body frame. 19. The medium of claim 17, comprising the program of instructions executable by the processor to perform the method, which further comprises: generating a direction cosine matrix by matching the magnetic unit vector and the velocity unit vector in the body frame with the magnetic unit vector and the velocity unit vector in the inertial frame;solving Wahba's problem for the direction cosine matrix; andcalculating the roll angle, the pitch angle, and the heading angle from the direction cosine matrix, wherein the correct solution to Wahba's problem is the roll angle, the pitch angle, and the heading angle of the spinning projectile. 20. The medium of claim 16, comprising the program of instructions executable by the processor to perform the method, which further comprises: using a low-pass filter on accelerometer measurements to compute the drag acting on the projectile;estimating a velocity unit vector in the inertial frame;estimating a velocity unit vector in the body frame;generating two 3×3 unit vector matrices;inverting one 3×3 unit vector matrix;multiplying one 3×3 unit vector matrix with the inverted 3×3 unit vector matrix to solve for Wahba's problem; andusing a singular value decomposition to generate a direction cosine matrix from the direction cosine matrix calculated to solve Wahba's problem in order to enforce orthogonality constraints on the direction cosine matrix calculated to solve Wahba's problem.
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이 특허에 인용된 특허 (19)
David J. Hepner ; Michael S. L. Hollis ; Peter C. Muller ; Thomas E. Harkins ; Gary Borgen ; William P. D'Amico ; Bradford S. Davis ; Lawrence W. Burke, Aeroballistic diagnostic system.
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