Documentation HG G-73650ZD | English, Revision 05 | Date: 09.03.2017 | www.goetting-agv.com
13
Chapter 2: Basic Principles of Track Guidance
The transponder antenna is able to determine the transponder position underneath the an-
tenna, however the direction of the antenna with regards to the transponder cannot be de-
termined. (
exception:
The transponder – a start transponder – can only be approached in
one direction, e.g. at a transfer station). Thus it is necessary to cross two transponders in or-
der to define the position of the vehicle. The odometry additionally measures the track be-
tween these two transponders. The transponder table enables associating absolute posi-
tions with the individually measured points (transponders). With the reading of two
transponders it is then also possible to determine the direction of the vehicle.
A fundamental disadvantage of the single antenna is that the calculated orientation of the
vehicle depends on the distance covered between the transponders. However, the determi-
nation of this distance can only be as precise as the vehicle's odometry. Thus the accuracy
of the calculation not only depends on the antenna and the transponders but also on the
odometry. Subsequently this calculation is not as accurate as the measurement accuracy
guaranteed if two antennas read two transponders simultaneously.
For non-omnidirectional vehicles make sure that the antenna is always mounted as close as
possible to the fixed axle. If this installation proves to be difficult or isn't feasible at all, the
antenna has to be located as close as possible to the fixed axle in the main direction of trav-
el. The further away the antenna is from the fixed axle the less accurate the measurement
will be. (Lever arm, high transversal speed of the transponders in curves and reduced effec-
tive detection range in curves).
Example
Figure 6
Properties of a single antenna set-up
Antenna properties:
The orange area of the antenna represents the range where max. one transponder
may be located. This area lies within a distance of approx. 50 mm around the antenna
casing.
The blue area is the antenna casing (here HG98820 180 mm x 360 mm)
The green area is the reception area of the transponder antenna (here approx. ±50
mm x ±125 mm)
If the thicker red line in the center of the antenna is crossed by a transponder, a posi
pulse will be triggered.
78,84
244,85
50
0
100
1500
4°
4°
3,
19
52
,0
4
