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

Results and discussion
After the measurement is completed the software generates a report-file,
containing general information such as: date and time, sampling distance,
distance between plants, additional information about the measurement,
distance from the soil surface, and settings for both sensors. The data set is a
two dimensional array in which every row contains the value sampled with the
position sensors, the values sampled with the RGB and laser sensor, time
stamp, and centre position of the last detected plant. The time stamp is used for
calculation of the carrier’s average forward speed in every sampling loop.
5.1.1 Evaluation of the algorithm for detection of the
plant centre position
For detection of the plant centre position according to the algorithm described in
chapter 5.1, VI-s were written. The calculation mechanism of the pattern’s
centre position, as one of the key functions built-in the algorithm for detection of
the plant centre position, needs to be described. After the array building was
completed the data acquired from the RGB and laser sensor are extracted and
transformed to a 1-dimensional row vector. The search_1D_array function
searches for the first element which has a TRUE value, and returns its index. In
one loop starting from the obtained index a nested subroutine checks the array
until the number of FALSE values does not reach the maximal error inside plant
area or the last element of the array is reached. In case the length of counted
TRUE values and allowed FALSE values remain smaller than the imputed
minimum plant size feature, the checking subroutine starts again from the next
detected TRUE value. When the plant size corresponds to the expectation, it is
bigger than the minimum plant size feature, another nested subroutine
calculates the arithmetic mean of the last and first index subtract. The VI returns
the linear position and time stamp corresponding to the calculated arithmetic
mean element. Sometimes, a plant is smaller than the minimum plant size
feature or it is missing because of suboptimal conditions. When that happens
the VI returns the expected centre position of the plant which is a simple sum of
the previous centre position and average distance between the plants.
Statistically, this position will be the most probable, and the displacement of the
following plant will be low enough to stay inside the searching area. The block
diagram of the VI is illustrated on the Figure 5.3.
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