## 2 Materials and Methods
### System's Design and Construction
#### 2.1.1 Hardware: Stable and Moving Parts  
The RoboPlantDect system was designed to monitor lettuce plants growing in a greenhouse inside plastic pots and further arranged in 3 m long rows. A prerequisite design definition was that the whole construction should be lightweight and that it could be placed above any row of plants inside the greenhouse, by a person or two, without disassembling the whole device each time. Following this requirement, the main structure of the system was assembled mainly by combining high quality, lightweight linear aluminum extrusions. For this purpose, three V-Slot 2060 (20 mm \(\times\) 60 mm) aluminum beams [42] (Figure 3c) were connected in series, one 1.5 m and two 1 m long, since the desired 3.5 m long single beam could not be found at the time of device's construction at the local market. By placing the 60 mm side vertically, no bending was observed along the whole run of the 3.5 m long rail. V-Slot's aluminum profile construction characteristics feature the internal V-shaped channels and V-grooves that further permit the linear V-Slot wheels' smooth movement (Figure 3c,d). For firmly connecting the V-slot 2060 in series, tee nuts were placed in the top and bottom ends of the V-Slot connections at both sides (Figure 3d). Moreover, at both edges of the 3.5 m long beam, two camera tripods (Figure 3a) [43] capable of extending up to 210 cm height were attached to support the whole structure. These tripods are very lightweight, and they significantly facilitate height adjustments. They also have the added benefit of being able to be positioned in any uneven area, which is a typical sight in greenhouses. Finally, at the top of each tripod, a mounting plate 4 was placed (Figure 3b) to ensure that both tripods were fitted to the aluminum beams securely. Figure 2: Simplified schematic showing the proposed computer vision-based system’s pipeline. A cable drag chain 10 mm \(\times\) 10 mm organizer (Figure 4a) was placed on top of the beams to ensure the proper grip and smooth movement of the power cable. Made from nylon, with a bend radius of 18 mm and external dimensions of 17 mm \(\times\) 14 mm, it proved to be an ideal choice for cable management. To ensure that the cable organizer always stayed on top of the V-slot beams and did not fall on either side (during system movement), two pieces of a 1 mm \(\times\) 40 mm aluminum beam were cut, drilled, and further used as both protective sidewalls and as a guide (Figure 4b). The latter aluminum supports were secured with spring-loaded ball nuts (Figure 4c). This prevents unwanted movement of the nut in the slot and allows the nuts to be inserted in a vertical position, as they will not slip due to gravity. As a carriage for the main construction platform, a V-slot Gantry Plate set of 20-80 mm (Figure 4d) [44] was used and under it, a piece of marine plywood (dimensions \((W\times L\times H):250\) mm \(\times\) 150 mm \(\times\) 6 mm) was secured. Finally, another small piece of plywood beam (dimensions \((W\times L\times H):35\) mm \(\times\) 115 mm \(\times\) 20 mm) was fixed to the carriage to link the carriage with the drag chain and the cables. The system's power switch was attached to this beam. To protect the carriage (and all the electronic components mounted on it) from the accidental use of the greenhouse's mist irrigation system, a water-resistant plywood box was designed, constructed, and used as the system's protection cover (Figure 1c,d). The final construction turned out to be robust, adaptable, and dependable. Figure 4: In (**a**), the cable drag chain used for cable management is shown; in (**b**), side views show the custom-made aluminum beams that were used as the cable drag chain’s guide/sidewall protection; (**c**) spring-loaded ball tee nuts used for aluminum beam fixation; (**d**) the carriage platform. Figure 3: Main hardware frames and support parts.