Operating Manual HG G-98830YA | English, Revision 02 | Date: 21.06.2021
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Operating Principle – Chapter 5
Figure 6
Sketch: Position detection with transponders
As soon as a transponder begins to transmit within the antenna field, the antenna
reads the individual transponder code and interpolates the position of the transpon
-
der's electromagnetic field within the antenna field. It passes this information on to
the higher-level control system via its interfaces. The vehicle thus knows where a
transponder is located underneath the antenna and what code it has. In addition, the
antenna emits the so-called positioning pulse (PosiPulse) when the transponder
crosses the center of the antenna in the X direction (usually the direction of travel).
With this positioning pulse, the time of crossing the reference axis can be transmit
-
ted by telegrams without any time delay.
5.2 Track Guidance with Transponders
Automated guided vehicles (AGVs) follow a predefined course. For this purpose, the
vehicles are usually equipped with sensors for position estimation by means of dis
-
tance measurement, a so-called odometry. Incremental encoders count the revolu
-
tions of the wheels. From this, a downstream navigation system uses the circumfer
-
ence of the wheels and the steering angle to calculate the distance traveled and the
orientation of the vehicle. Odometry has the advantage that it is available without
interruption. However, the position calculated with odometry deteriorates – e.g. due
to slippage – the further the vehicle travels.
Figure 7
Sketch: Track guidance with odometry and transponders
This is where the transponder system comes into play. The transponders in the
ground are located at highly accurate positions and are used to determine the actual
position of the vehicle at specific points. The downstream navigation system or the
navigation controller (neither of which is part of the transponder antenna) resets its
estimated position at these points to the precisely determined value.
1
3
2
Transponder
Transponder
Local coordinate system
Antenna
Ground
X
Vehicle
Direction of travel
antenne
SIDE VIEW
Y
X
3
X
2
X
1
Y
2
Y
1
Y
3
Transponder
center
Y
Transponder
antenna
TOP VIEW
Center axis
PosiPulse
when crossed
X
Transponder antenna
Transponder
Navigation point
Virtual track
Wheels with incremental encoders
Rotating frame
Pivot point
Steering angle (from navigation controller)
Offset antenna center <—> navigation point in X and Y direction
Deviation odometry
compared to actual position
Vehicle
Direction of travel (X direction)
