Husqvarna Automower 420 Technical Manual page 10

1. FUNCTION
1.5.3 Irregular mowing pattern
The robotic lawnmower mows the lawn in an irregular
pattern. This gives a very even mowing result. In ad-
dition, there are no distinctive tracks left in the lawn,
which is often the case when using a conventional lawn
mower.
Spiral cutting
Sometimes the robotic lawnmower can change the
mowing pattern and start to mow in a spiral pattern in-
stead. This is called spiral cutting. The purpose of spiral
cutting is to quickly get the same length of grass over
the entire working area.
When the robotic lawnmower starts spiral cutting this
means it has perceived the lawn in an area to be longer
and/or thicker than before. The length/thickness of the
lawn in this area does not need to differ that much from
the other areas for the robotic lawnmower to start spiral
cutting. Sometimes the difference is hardly visible.
The robotic lawnmower always attempts to keep the
blade disc at an even speed. Different degrees of pow-
er are used for this depending on the length/thickness
of the grass. Automower® compares the instantane-
ous power with an average power value from the latest
hours of mowing. This means that, when the robotic
lawnmower enters an area where the lawn is longer/
thicker than before, the instantaneous power will differ
from the average power and the Automower® will then
start spiral cutting.
The factory setting for Intensity is Medium for the
Automower® to begin spiral cutting. Intensity can be
set between Low/Mid/High using the Settings - Spiral
cutting menu. It is also possible to entirely shut down
the spiral cutting function in this menu. The Low setting
means that the robotic lawnmower begins spiral cutting
less often.
Spiral cutting is only activated in the automatic operat-
ing position, i.e. the Main area mode. Mowing in the
Secondary area mode does not allow the robotic lawn-
mower to begin spiral cutting.
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