Improved Inertial/Odometry/GPS Positioning of Wheeled Robots Even in GPS-Denied Environments - Global Navigation Satellite Systems: Signal,Theory and Applications - page 271

Crossbow IMU (IMU300CC)
Gyroscopes Accelerometers

Bias, ◦ /sec

< ±

2.000 Bias, mg

< ±

30.000

< Scale Factor, % 1.000 Scale Factor , % 1.000

Random Walk, ◦ / √ hr 2.250 Random Walk, m/(s √ hr )

0.150

Table 1. Bias, scale factor error and random walk for the Crossbow IMU300CC IMU.
Adapted from ( IMU300CC - 6DOF Inertial Measurement Unit , 2009).

Honeywell IMU (HG1700)
Gyroscopes Accelerometers
Bias, ◦ /hr 1.000 Bias, mg 1.000
Scale Factor, pp m 150.000 Scale Factor, ppm 300.000
Random Walk, ◦ / √ hr 0.125

Table 2. Bias, scale factor error and random walk for the Honeywell HG1700 IMU found in
Novatel GPS/INS. Adapted from SPAN Technology System User Manual OM-20000062 (2005)
and HG1700 Inertial Measurement Unit (2009).

using velocity updates from wheel encoders during GPS outages. Each of the four navigation
solutions are described as follows:

KF using RISS and velocity updates during GPS outages;
KF using RISS without updates during outages;
KF using full IMU with velocity updates during outages; and
KF using full IMU without updates during outages.

The errors in all the estimated solutions are calculated with respect to the NovAtel reference
solution. Results for two trajectories are shown in this work. The first trajectory is shown in
fig 4 and is located on-campus at RMC. It forms a loop with start and end at the same position
and contains two different sections with hills both at an incline and decline to the robot's
trajectory.

The second trajectory for this experiment is shown in fig 5 and is also located on-campus at
RMC. This trajectory forms a loop with start and end at the same position and is much longer
than the trajectory in fig 4. It contains several different sections which include hills both at an
incline and decline to the robot's trajectory.

4.1 Trajectory 1
The ultimate check for the proposed systems accuracy is during GPS signal blockage which
can be intentionally introduced in post-processing. Since the presented solution is loosely
coupled the outages represent complete blockages of GPS updates. Seven GPS outages are
simulated with durations of 60 seconds each. The simulated outages are chosen such that
they encompass straight portions, turns, and slopes.

Table 7 shows the root mean square (RMS) error in both the estimated 2-D horizontal position
and the estimated altitude during seven GPS outages for the four compared solutions. The