Abstract—This article aims at im proving positioning
precision and stability of the SINS/Doppler/Platform Compass
integrated navigation system. Firstly, based on considering of
the characteristic and performance of the integrated system, the
system model is established. And the discrete state and
measurement equations are achieved. Secondly, traditional
Kalman filter for this system is usuall y unstable, and easy to
divergent. So reasons for divergence of integrated navigation
with traditional Kalm an filter is analyzed. Thirdly, Sage-Husa
Kalman filter based on UD decomposition is designed. And
some improvements have been made according to the analysis
results. Finally, several simulation experiments were made to
test the effect of the improved algorithms. The simulation
results indicate that improved Sage-Husa Kalman filter based
on UD decomposition can guarantee the precision and stability
of the SINS/Doppler/Platform Compass integrated navigation
system.
I. INTRODUCTION
Strapdown inertial navigation system(SINS) has many
advantages. Such as independence of external information,
good concealment, strong radio resistance, all-weather work,
etc. However,it’s positioning error is accumulated over time.
So it cannot be used for long time and long distance navigation.
In order to improve precision and stability of the navigation
system, SINS is integrated with Doppler and platform
compass. And Kalman filtering technology is currently the
most widely used algorithm in integrated navigation system.
In order to obtain the optimal estimation,traditional
Kalman filter heavily relays on accurate error model and on
that the calculation error is as small as possible. However, the
running environment of navigation system is time-variant
system which is more complex. So it is difficult to obtain the
error model of the navigation system. On the other hand,
rounding error and interception error of the computer can
cause the error co-variance loss of positive definiteness. These
factors are likely lead Kalman filter to divergent and even fail,
which affects the accuracy of integrated navigation system.
Based on analysis of reasons for divergence of integrated
navigation with traditional Kalman filter, Sage-Husa adaptive
Kalman filter algorithm is introduced. According to
*
This work was sponsored by China’s National Science Foundation
(No.61304259), Youth Backbone Teacher Training Project in Henan
University of Technology, Major Scientific Research Project in Henan
Province (No.122102210044).
Jianjuan Liu is with School of Electrical Engineering, Henan University
of Technology, Zhengzhou, 450001 China (corresponding author:
86-18623718257; fax: 86-371-6775-8827; e-mail: ljjhaut@gmail.com).
Hongmei Chen is with School of Electrical Engineering, Henan
University of Technology, Zhengzhou, 450001 China (e-mail:
chenhongmei_seu@163.com).
Nanbo Liu is with School of Electrical Engineering, Henan University of
Technology, Zhengzhou, 450001 China (e-mail: lnb@haut.edu.cn).
characteristic of the SINS/Doppler/Platform Compass
navigation system, this algorithm is improved. And the
improved algorithm is called improved Sage-Husa adaptive
Kalman filter based on UD Decomposition. Finally, the
effective Sage-Husa Kalman filter is used in the
SINS/Doppler/ Platform Compass navigation system. The
simulation results indicate that the effective Sage-Husa
Kalman filter is better than traditional Kalman filter when
model parameter error or noise characteristic error exist.
II. SINS/DOPPLER/P
LATFORM COMPASS INTEGRATED
NAVIGATION SYSTEM FILTER MODEL
The strapdown inertial navigation system is to provide
local reference attitude for other devices. So other navigation
equipment can be used as the external information. The speed
information comes from Doppler log is selected as the external
information. Due to speed information has no obvious effect to
the heading angle, the error of heading angle between
strapdown navigation system and platform compass is also
selected as the observation quantity. State equation and
measurement equation of this linear discrete system are as
followings.
kkkk
kkkkkk
VXHZ
WXX
,11
(1)
Where,
T
bzbybxbybxUNENE
LVVX ][
.
E
V
,
N
V
are the east and north error of velocity respectively.
E
,
N
,
U
are the east, north and sky error of the attitude angle
respectively.
,
L
are the latitude and longitude error
respectively.
bx
、
by
are the east and north zero bias of the
accelerometer respectively.
bx
,
by
,
bz
are the east, north and
sky drift of gyroscope respectively.
T
UNE
VVZ ][
,
E
V
,
N
V
are the east and north error of speed between
strapdown navigation system and Doppler log.
U
is the
heading angle error between strapdown navigation and
platform compass .
k
W
,
k
V
are system noise and observation
noise respectively. And they are uncorrelated white noise.
III. ANALYSIS OF RESONS FOR DIVERGENCE OF
INTEGRATED NAVIGATION WITH TRDTITIONAL
KALMAN FILTER
In the process of using Kalman filter, actual error of state
estimation is many times larger than theoretically predicted
error, and it increases with the data increasing despite of
decreasing of the error covariance matrix
k
P
.This
phenomenon is called divergence. Divergence will affect the
Effective Sage-Husa Kalman Filter for SINS/Doppler/Platform
Compass Integrated Navigation System*
Jianjuan Liu, Hongmei Chen, Nanbo Liu