Full text: Technical Commission VII (B7)

   
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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 
     
  
  
    
  
  
  
  
    
    
  
  
  
  
  
  
    
   
   
     
   
   
   
  
  
  
    
  
   
   
   
   
    
     
    
      
    
   
    
   
    
  
   
   
       
   
    
   
 
	        
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