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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
THE PERFORMANCE ANALYSIS OF AN AKF BASED TIGHTLY-COUPLED INS/GPS
INTEGRATED POSITIONING AND ORIENTATION SCHEME WITH ODOMETER AND
NON-HOLONOMIC CONSTRAINTS
Kun-Yao Peng", Cheng-An Lin* *, Kai-Wei Chiang*
* Dept. of Geomatic, National Cheng Kun University, No.1, University Road, Tainan County 701, Taiwan —
p66004057@mail.ncku.edu.tw
Commission VIU/7, III/2, V/1, V/3, ICWG V/I: Low-cost UAVs (UVSs) and mobile mapping systems
KEY WORDS: INS, GPS, Tightly-coupled, AKF, non-holonomic constraints
ABSTRACT:
INS/GPS integration scheme can overcome the shortcoming of GPS or INS alone to provide superior performance, thus this study
implements a tightly-coupled INS/GPS integration scheme using AKF as the core estimator by tuning the measurement noise matrix
R adaptively. The AKF is based on the maximum likelihood criterion for choosing the most appropriate weight and thus the Kalman
gain factors. The conventional EKF implementation suffers uncertain results while the update measurement noise matrix R and/or the
process noise matrix Q does not meet the case. The primary advantage of AKF is that the filter has less relationship with the priori
statistical information because R and/or Q vary with time. The innovation sequence is used to derive the measurement weights
through the covariance matrices, innovation-based adaptive estimation (IAE) in this study. The covariance matrices R are adapted in
the study when measurements update with time. A window based approach is implemented to update the quality of GPS pseudo-
range measurements by adaptively replace the measurement weights through the latest estimated covariance matrices R.
The use of odometer is particularly recommended when a low cost and precise vehicle localization system has to be implemented and
there is the risk of GPS coverage failure, which is prone to happen when the vehicle enters a tunnel or cross deep valleys. Odometers
are applied in land-vehicle navigation to provide augmented host velocity observations for standalone INS system in this study.
There are two non-holonomic constraints (NHC) available for land vehicles. Land vehicles will not jump off the ground or slid on
the ground under normal condition. Using these constraints, the velocity of the vehicle in the plane perpendicular to the forward
direction is almost zero. EKF and AKF based tightly-coupled scheme with NHC is implemented in the study.
To validate the performance of AKF based tightly-coupled INS/GPS integration scheme with odometer and NHC, field scenarios
were conducted in the downtown area of Tainan city. The data fusion of INS/GPS/Odometer/NHC can be used as stand-alone
positioning tool during GPS outages of over 1 minute, and AKF based tightly-coupled INS/GPS integration scheme can be more
stable combined with odometer and NHC during GPS outages of over 1 minute likewise.
1. INTRODUCTION
Global Positioning System (GPS) receivers require direct line of
sight signals to the GPS satellite to provide navigation solutions with
long-term stability; consequently, it is capable of providing
continuous navigation solutions with uninterrupted signal reception.
However, GPS leaves two scenarios to be considered in the land
environment. The first one is intermittent signal reception, as for
instance in heavily forested areas or in urban canyons. The other
one is no signal reception at all, as for instance in buildings, tunnel
or underground. In the first case, GPS has to be integrated with other
sensors to bridge periods of no signal reception. In the second case,
GPS has to be replaced by another navigation system that can
provide continuous navigation solutions in above environments
during no GPS signal reception.
On the contrary, Inertial Navigation System (INS) is widely
used in many applications for navigating of moving platforms.
Low-cost INS can experience large position and attitude errors
over short term duration in comparison with high-grade systems.
It has been proved through numerous researches that the
INS/GPS integrated is the ideal technique for seamless
vehicular navigation.
* Corresponding author: C.A. Lin
The stand-alone INS is self-contained and independent of
external signals. Providing acceleration, angular rotation and
attitude data at high sampling rates is the primary advantage of
using INS in land vehicles. However, the disadvantage of using
INS is that its accuracy degrades rapidly with time because of
the accumulations of nonlinear errors and noises from
accelerometers and gyros, as shown in Figure 1. Therefore, INS
is used in the short-term case if no other navigation system or
navigational aids is available.
Position
Error
IMU-sensed
Final Position” +...
Actual Final
Position
Figure 1. The limitations of INS based navigation systems
The integrated system consisted of INS and GNSS takes
advantage of the complementary attributes of both systems and
