Guidance Control in Detail
English, Revision 07, Date: 07.03.2018
20
2.2.1
Odometric System
The odometric system determines the change in the vehicle position and vehicle
heading using the wheel rotations and/or steering angle and/or gyro. There are differ-
ent odometric systems available:
All odometric systems have the advantage to be highly accurate over short distances
and are prepared to supply the vehicle position and heading at any time. At start-up
first of all the position must be initialized. The accuracy of odometry is affected over
long distances and results in an accumulation of errors of the sensors and calcula-
tions. This may possibly cause considerable deviations.
Sensor failure detection is possible by comparing two different odometric systems.
Example
The position of a truck is determined by odometry 2 (
primary
odometry
). Additionally odometry 0 will be calculated also
(
secondary odometry
). Subsequently the measured values will be
compared. The tolerances of the angle, as well as X and Y posi-
tion can be parameterized. Odometry 0 will slightly differ in dis-
tance travelled from odometry 2 (the inaccuracy amounts to
about 1% of the distance travelled). At the next transponder / Sky
Number
Description
Advantages / Disadvantages
0
There are 2 monitored wheels on 1 fixed axle.
Encoder 1 measures the rotations of the left
wheel. Encoder 2 measures the rotations of
the right wheel.
-
Advantage: simple structure
-
Disadvantage: load dependent if the
vehicle has airfillled rubber tires
1
There are 2 monitored wheels on 1 fixed axle.
The alteration in heading angle is determined
by the steering angle.
-
Advantage: less load dependent
-
Disadvantage: inaccuracies in tight
turns may occur
2
There are 2 monitored wheels on 1 fixed axle.
The distance travelled by the vehicle is the
average distance travelled by both wheels.
The alteration in heading is determined by a
gyro.
-
Advantage: less load dependent
-
Disadvantage: additional gyro
required
3
There are 2 monitored wheels on 1 steered
axle. The alteration in heading angle is deter-
mined by the steering angle.
-
Disadvantage: inaccuracies in tight
turns may occur
-
Load dependent if the vehicle has
airfilled rubber tires
4
There are 2 monitored wheels on 1 steered
axle. The distance travelled by the vehicle is
the average distance travelled by both
wheels. The alteration in heading is measured
by a gyro.
-
Advantage: less load dependent
-
Disadvantage: additional gyro
required
Table 4
List of the different odometric systems available, including advantages
and disadvantages
