Design And Research Of Cleaning Machine For Plastic Greenhouse Roofs

Facility agriculture develops later in China than that in developed countries, containing mainly the glass greenhouse and the plastic greenhouse. There are some characteristics of facility agriculture in China, such as rapid development, widely gross area and diversification. The market share of the plastic greenhouse which has dominant economy is increasing gradually. With using of plastic greenhouses, the roof surface is polluted easily by the dust and some mosses, which makes light transmittance drop significantly, so it is necessary to clean the greenhouse roof regularly for increasing light transmittance of the greenhouse roof which is vital to the photo-synthesis of the plant and enhancing production efficiency of the greenhouse.Because the cleaning work of greenhouse roofs is artificial completely recently, it is low efficiency and exists safety problems. In recent years, some researchers from many countries have proposed various design schemes of the cleaning machine for greenhouse roofs, but the results are not satisfactory after doing experiments and researches. As the air pollution increases accumulation of the dust, the cleaning frequency increases, which leads to increasing labor cost, and it is necessary to develop a kind of roof cleaning machine with high automation and high efficiency. There is a kind of cleaning machine, high work efficiency and fine cleaning effect, for greenhouse roofs abroad, but it can only be used for cleaning the greenhouse without sunshades.This paper presents a kind of cleaning machine for plastic greenhouse roofs, and this machine can be used for the plastic greenhouse, regardless of sunshades. The cleaning machine consists of multi-section cleaning units which are composed of the walking mechanism and the cleaning mechanism, and these units link each other by hinge joint for adapting the arc of roofs.The control system has a main controller communicating with other sub controllers by CAN bus, and PIC18F248 is used as the MCU of all controllers. In order to reduce power dissipation on the wire and keep supply voltage for each cleaning device consistent,12V which is converted from 36V by the DC/DC convertor is used as supply power for the whole control system. The system sets a module for detecting extreme position, and the cleaning machine can automatically stop when it moves at the end of the shed to prevent the cleaner from falling down from the roofs. The control system increases a function of synchronized walk to keep each cleaning device walking synchronously, and this design increases the system reliability. The system uses CAN bus for communication, which has the advantages of strong anti-interference, convenience and low cost etc.The preliminary experiment of the cleaning machine on the experiment platform showed that the walking mechanism can drive reciprocating motion of the cleaning mechanism smoothly on the plastic greenhouse roof in accordance with the design requirements. Meanwhile, the articulated design for linking the whole cleaning machine had the expected effect which can imitate the arc shape of the roof. The further tests for the cleaning effect and the motion drive verified the rationality of this design. The orthogonal experiment was conducted for the film of 35% transmittance, and the results showed that the maximum transmittance was 78.37% reaching the remarkable cleaning effect after cleaning. After making further analysis for the data, this paper gained the order of the factors for cleaning effect, and first is brush speed; next is walking speed; last is water flow. The 120r/min speed of the brush on the cleaning machine is reasonable. Walking speed and water flow can be adjusted according to the pollution degree of the cleaning target. The 0-3m/min speed conforms to the realistic applications.The total weight of the cleaning machine is borne by the crossbar bracket of the plastic greenhouse roof and the film. It solves the main problem how the cleaning machine adapts the top arc of the greenhouse for cleaning the rough surface of the film adaptively to link each cleaning device by hinges. This cleaning machine has some advantages of high automation, simple operation, dominant cleaning effect and high efficiency.