Guidance Control in Detail
English, Revision 07, Date: 07.03.2018
18
If the vehicle starts moving with this calculated steering angle, the point towards which
the vehicle aims moves on. In this way the vehicle returns to its intended track without
oscillating, provided the steering velocity is sufficiently fast and the vehicle speed ad-
justed.
To ensure a reduction of the oscillation for movements under worse conditions (higher
velocities or slower steering) different parameters can be adjusted. Thus the angle at
which the vehicle returns to the intended track can be limited dependent on the cur-
rent velocity. For more detailed information see chapter 4 on page 28.
If the vehicle drives around a curve, the intended track for the controller is calculated
by the tangent at the intersection of the rear axle. The needed angle to go around the
curve is computed by an algorithm and added to the angle of the feed back control.
If the vehicle travels backwards, it is mirrored at the rear axis. Subsequently the steer-
ing angle of the mirrored front wheel is calculated and inverted.
2.1.5
Velocity Calculation
The velocity is obtained from the information of the support points. Here the velocity of
the support point just passed and the upcoming support point is interpolated. Which
of the two support point velocities ("velocity endpoint" or "velocity connection") is se-
lected will depend on whether the vehicle shall stop at the segment's end or not. Once
the direction of travel is reverted from forward to backward or vice versa, the "velocity
endpoint" is selected. Also, if the course has a sharp bend at its end or terminates
completely, the "velocity endpoint" is selected.
For some vehicles various additional protective mechanisms are integrated. If signifi-
cant lateral deviations occur or if the difference between the set and actual steering
angle is too large, the vehicle decelerates to 0,2m/s. It will only accelerate to the orig-
inal velocity if the deviation was minimized.
If an error occurs or the vehicle drives beyond the end point, the velocity is set to 0.
2.1.6
Driving Modes
During normal operation of the vehicle, two different operation modes are used. The
idle mode (see section Abschnitt 2.1.6.1) and the automatic mode (see section
2.1.6.3). In idle mode the vehicle can be operated by a driver or the segment search
can be carried out. In the automatic mode, the steering controller controls the vehicle.
The parameter test mode (see section 2.1.6.2) will only be accessed during commis-
sioning.
NOTE!
All other modes are applied in test carriers / prototypes or are
applicable for demonstrations on exhibitions. They are not rele-
vant for productive systems.
2.1.6.1
Idle Mode
This mode allows to operate the vehicle manually or the vehicle control unit can initiate
a segment search.
