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

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Materials and methods<br />

34<br />

� Since detection is based on RGB components, it is less affected by<br />

target position and vibration.<br />

Several sensors were tested, and the CZ – H35S optical sensor head and the<br />

CZ – V21P digital fibre optic amplifier from Keyence Company have been<br />

chosen as most appropriate according to the requirements. The CZ – V21P<br />

digital fibre optic amplifier supports three different detection modes based on<br />

the combination <strong>of</strong> colour component detection and light intensity. The control<br />

interface built in to the amplifier allows the user to choose the optimal detection<br />

mode and to set up a matching rate corresponding between the calibrated<br />

target colour, as a reference, and the target colour currently being detected.<br />

The amplifier consists <strong>of</strong> four digital physical channels which can be separately<br />

calibrated with ad-hock autocalibration in few steps.<br />

Depending on the intensity and position <strong>of</strong> the illumination, some parts <strong>of</strong> the<br />

target objects can appear white as a consequence <strong>of</strong> lustre. The CZ-H35S<br />

sensor head incorporates a polarizing filter which cancels the reflection from the<br />

glossy section and only recognises targets by their colour components. Thus<br />

the CZ-H35S sensor head maintains accurate detection despite changing target<br />

conditions.<br />

Detecting range <strong>of</strong> the CZ-H35S sensor head is between 28 mm and 52 mm,<br />

with a spot diameter <strong>of</strong> 4.5 mm. The response time <strong>of</strong> the amplifier depending<br />

on the chosen detection mode lies between 200 µs and 8 ms. The sensor head<br />

and amplifier are illustrated in Figure 4.1.

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