Dust, algae, mold, lichen, and moss accumulation on the greenhouse cover materials could hinder sun lights and decrease the internal light intensity in greenhouses. Moreover, the traditional way of cleaning greenhouse roofs using ladders is laborious and time-consuming, requires a lot of water, and puts too much pressure on the roof. It could cause damage and risky labor. Consequently, many farmers leave greenhouse roofs dirty, which decreases plant photosynthesis due to the low light intensity. Therefore, this study aimed to design and fabricate a device for cleaning greenhouse roofs. The device parts were a telescopic arm with three concentric and adjustable cylindrical pipes with a rough brush mounted on a frame and connected to a motorized knapsack sprayer. The cleaning part of the 3D model was investigated using Computational Fluid Dynamics (CFD) software. The simulation outcomes informed that the system could supply a uniform nozzle speed. Meanwhile, it could control the water pressure and water flow rate. The analysis of the intensity disorder and the dissipation rate showed positive results for the system and valuable insights for efficient and safe system design. The average transmittances of the greenhouse roof before and after cleaning were 48.7 % and 68.5 %, respectively. Results also showed that the nozzle overlaps increased as the height of the mattress arm increased. There was no interference in all nozzle spray angles, and the first interference was recorded at a nozzle spray angle of 65° and a height of up to 19 cm. The overlap was ranged from 3 cm to 5 cm at a nozzle height of 21.5 cm. The ideal nozzle spacing was 27 cm at a nozzle spray angle of 65°. In conclusion, an efficient greenhouse roof-cleaning device has been developed for small and medium farms. However, further research is needed to enhance its power source, extend its lifespan, and improve its overall efficiency.

The ripeness of tomatoes is crucial to determining their shelf life and quality. Most of the current methods for picking and sorting tomatoes take a long time, so this paper aims to design a device for sorting tomatoes based on force and bioelectrical impedance measurement. A force sensor installed on each of its four fingers may be used as an impedance measurement electrode. When picking tomatoes, the electrical impedance analysis circuit is first connected for pre-grasping. By applying a certain pre-tightening force, the FSR sensor on the end effector finger can be tightly attached to the tomato and establish an electric current pathway. Then, the electrical parameters of the tomato are measured to determine its maturity, and some of the electrical parameters are used for force monitoring compensation. Then, a force analysis is conducted to consider the resistance of the FSR under current stress. According to the principle of complex impedance circuit voltage division, the voltage signal on the tomato is determined. At the same time, the specific value of the grasping force at this time is determined based on the calibration of the pre-experiment and the compensation during the detection process, achieving real-time detection of the grasping force. The bioelectricity parameters of tomatoes can not only judge the ripeness of tomatoes, but also compensate for the force measurement stage to achieve more accurate non-destructive sorting. The experimental results showed that within 0.6 s of stable grasping, this system could complete tomato ripeness detection, improve the overall tomato sorting efficiency, and achieve 95% accuracy in identifying ripeness through impedance.