Method for updating strapdown inertial navigation solutions based on launch-centered earth-fixed frame

Patent metadata

Field	Value
Publication number	US-11578992-B2
Application number	US-202016857132-A
Country	US
Kind code	B2
Filing date	Apr 23, 2020
Priority date	Apr 23, 2019
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

The present invention relates to a method for updating strapdown inertial navigation solutions based on a launch-centered earth-fixed (LCEF) frame (g frame). The present invention uses the g frame as a navigation reference frame of a medium-to-short-range surface-to-surface missile. This is beneficial to establish a relative relationship between the missile and the ground so as to keep the same missile parameters required by a missile control and guidance system. The calculation of a navigation algorithm in the g frame is moderate, which is suitable for an embedded system.

First claim

What is claimed is:

1. A method for updating strapdown inertial navigation solutions using a launch-centered earth-fixed (LCEF) frame (g frame), comprising the following steps:
step 1: using a surface-to-surface missile (SSM) as a body to establish a relative relationship between the SSM and a ground to keep identical missile parameters required by a missile control and guidance system, and establishing a body frame (b frame), which points front, top, and right;
step 2: expressing a navigation equation in the g frame as:

[

P
.

g

V
.

g

R
.

b
g

]

=

[

V
g

R
b
g

⁢

f
b

-

2
⁢

Ω
ag
g

⁢

V
g

+

g
g

R
b
g

(

Ω
ab
b

-

Ω
ag
b

)

]

wherein, P g , V g and R b g are position, velocity and attitude matrices of the body in the g frame, and corresponding equations are position, a velocity navigation equation and an attitude navigation equation; f b is a measured value of an accelerometer triad; g g is a gravity of the body in the g frame; Ω ab b is an anti-symmetric matrix corresponding to a measured value ω ab b of a gyroscope triad; Ω ag b is an anti-symmetric matrix corresponding to a rotational angular velocity ω ab b of the g frame relative to an a frame;
step 3: performing attitude update on the SSM, comprising the following sub-steps:
step 3-1: resolving the attitude navigation equation in step 2 by a quaternion method:
q b(m) g(m) =q g(m-1) g(m) q b(m-1) g(m-1)q b(m) g(m-1)

where, q b(m-1) g(m-1) is a transformation quaternion from the b frame to the g frame at a t m-1 moment, that is, an attitude quaternion at t m-1 ; q b(m) g(m) is an attitude quaternion at t m ; q g(m-1) g(m) is a transformation quaternion of the g frame from t m-1 to t m ; q b(m) b(m-1) is a transformation quaternion calculated from an angular increment from t m-1 to t m ;
step 3-2: calculating with an equivalent rotation vector method, wherein
an equivalent rotation vector ζ m of the g frame from t m-1 to t m is expressed as:

ϛ
m

=

∫

t

m
-
1

t
m

⁢

ω
ag
g

⁡

(
t
)

⁢
dt

≈

ω
ag
g

⁢
T

an equivalent rotation vector Φ m of the body frame relative to an inertial frame from t m-1 to t m is expressed as:

Φ
m

=

∫

t

m
-
1

t
m

⁢

ω
ab
b

⁡

(
t
)

⁢
d
⁢
t

step 3-3: applying the angular increment measured by the gyroscope triad to an actual project to calculate:

Φ
m

=

Δ
⁢

θ

Assignees

• Univ Northwestern Polytechnical

Inventors

• Chen Kai
• Sun Hanyan
• Zhang Hongyu
• Liu Mingxin

Classifications

• F41G7/36 Primary

  using inertial references · CPC title

• G01C21/16

  by integrating acceleration or speed, i.e. inertial navigation · CPC title

• G01C25/005 Primary

  initial alignment, calibration or starting-up of inertial devices · CPC title

• G06F17/16

  Matrix or vector computation {, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization (matrix transposition G06F7/78)} · CPC title

• G06F17/10

  Complex mathematical operations {(function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544)} · CPC title