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Description of our
work:
Our group is responsible for the sensor
fusion system on TerraMax, which can be divided into two different
subgroups according to the function of the sensors: high level
sensor fusion and low level sensor fusion. The function of high
level sensors is to perceive the surrounding environments near the
vehicle, to describe it with a suitable data structure based on
which path planner can find a suitable way to the destination. Low
level sensor fusion provides the necessary positioning information
in conjunction with the description of the dynamic states of the
vehicle to the system. On TerraMax, the high level sensors
include: two mono-vision, two stereo vision, four laser rang
finder (LADAR), two radar and 12 ultrasonic sensors while low
level sensors are compose of two GPS, one INS, one compass, brake
and steering sensors and odometers, etc.
Features of our
sensor fusion system:
High
level sensor fusion:
1.
A grid-based map is set up to describe the environments
around the vehicle. The map can move with the vehicle, fusing new
information from the sensors into the old map automatically. It is
flexible and easy to integrate any new sensors;
2.
Based on the different information from the sensors, the
grid of the map can be classified as road, vegetation, positive
obstacle, negative obstacle, moving obstacle or unknown area, with
a confidence representing the certainty of the classification;
3.
Mono-vision can detect the road boundaries;
4.
Two forward looking LADAR and the stereo vision system can
detect the positive obstacles ahead of the vehicle;
5.
With the vertical LARAR, the system can tell the negative
obstacle or up/down slopes ahead;
6.
The rear LADAR and radar can tell the obstacles behind the
vehicle when backing up;
7.
Ultrasonic sensors around the vehicle are used to detect
nearby obstacles when narrow passage is met.
Low
level sensor fusion:
1.
With the OmniStar’s High Performance (HP) service, a
positioning accuracy of 20cm CEP with up to 20 Hz output rate can
be obtained;
2.
Fusing INS, GPS and Compass by Extended Kalman Filter (EKF),
higher data rate (up to 100 Hz) and stable positioning output can
be obtained even when GPS outage happens;
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