茶园高架风扇防霜效果试验与控制系统设计

Frost Protection Effects and Control of Wind Machine for Tea Garden under Temperature Inversion during Early Spring

为防止早春晚霜对茶叶的危害,提高茶叶的品质和产量,进行茶园高架风扇防霜效果试验及风扇防霜控制系统设计。高架风扇防霜效果试验表明:逆温条件下,风扇防霜效果好;风扇轴线方向25m范围内温度均有不同幅度的提高,20m范围效果尤为明显;随着作用距离的增加,温升幅度减小;试验中最高升幅达3.6℃。根据试验结果设计了以PC机为主控单元、各终端节点以MSP430单片机为核心的控制系统,采用RS-485总线实现通信。各终端节点作为一个独立的控制单元,监测各节点温度并根据冠层温度和逆温条件控制风扇的开启和关闭。假定茶园上空3m高处温度为TA,茶树冠层温度为TB,则开机条件为:TA>TB,TB<0;关机条件为:(TA≥TB,TB>0)U(TA≤TB)。

Late frost damage in early spring sometimes happens with temperature inversion. Tea prnduction has severely suffered from radiation frost damage in earlv spring because of inversion temperature. Conventional methods of frost protection, such as covering, smoking or irrigation are ineffective; the method of disturbing air in the thermal inversion layer has proved applicable for frost protection in Europe, Japan and the USA. which is implemented by wind machines. However, research and development of the method in China is just at the beginning stage. The experiment was conducted to make clear the protection effect with wind machine under temperature inversion, the results show that the operation of wind maehine could remarkably increase the temperature at tea plant canopy, especially when thermal inversion was strong. Within 25 m in front of the wind machine, tea canopy could be completely prevented from frost. And at 20 m in front of the wind machine the increased temperature reached the maximum of 3.6 ℃. Through the experiment and analysis on the protect affection with wind machine, A automatic control system of wind machine for frost protection was designed ,The eontrol system was designed which was relied on PC machine as the master control unit, and the MSP430 single chip was the hard-core of the various terminal unit,RS-485BUS was adapted to realize communication. Each terminal unit was a independent control part, it was de- veloped to start or close the wind machine automatically according to the temperature inversion condition and the temperature of the tea canopy measured by the terminal unit, consequently reached the effect of centralized control and dispersed supervision.