Development of a novel mechatronic system for mechanical weed ...

Results and discussion
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5.2.1 Optimisation of the arm length
The maximum and minimum arm lengths was calculated considering the
required hoeing depth d and the necessary confidence that duckfoot knives
need to achieve a cut under the soil surface cultivating the specified hoeing
width. It was estimated that an arm length in the range of 350 - 550 mm,
measured from the rotational axis to the cutting edge of the duckfoot knife,
offers enough freedom for positioning the trajectory between plants and
provides a hoeing width that is wide enough to cultivate the whole area which
cannot be reached with inter-row equipment.
Depending on the soil surface cultivation quality and roughness, a minimum
hoeing depth hdmin needs to be defined, providing the optimal impact and
necessary hoeing width on the root system of the weeds with a high level of
confidence (see Figure 5.10). On the other hand a maximum hoeing depth
hdmax needs to be defined because it influences the soil resistance to hoeing
and on that way it also affects the torque on the shaft of the motor.
hdmin = hdmax – surface roughness
Figure 5.10 Trajectory of the duckfoot knife under the soil surface
with minimum and maximum hoeing depth