Development Of Testing And Fuzzy Controlling On Temperature And Humidity

The system of testing and fuzzy controlling on temperature and humidity mainly includes two major parts: the testing -control and the data processing. The testing-control section takes MCS-51 series SCM (AT89C51) as a core. LTM8901 which is digital, can measure the temperature and humidity together, transmits the temperature and humidity data to the SCM through the monobus. And then the temperature and humidity data can be transmitted to the PC by 485 bus, meanwhile the data is treated by the PC. The system precision can not be influenced by transmission, because LTM8901 uses the digital monobus technology. LTM8901 do not need fussy circuit such as A/D, so the system has fewer fault and can maintain expediently. 485 bus compares with 232 bus and 422 bus, which not only extend the transmission distance, but also hang lots of nodes. That satisfies the request of the testing-control system. Therefore this system chose 485 bus, which is fine on the performance and the economical efficiency.This system may act according to the request of the environment which is examined. It may set the control range of the temperature and humidity, set the top and low limit of the temperature and humidity, automatically control the start and stop of the heating conduit, the spraying device, the rolling-screen device, the opening-window device and the fan. It can adjust the greenhouse environment to make the value of the temperature and humidity hold in a scope and establish the environment which suits the crops to grow. Because the greenhouse is a complex environment and the temperature and humidity can not exist independently, the simple control method hardly reach better control effect. Therefore the fuzzy control algorithm is used. It compares with the common control algorithm, which does not need to know the mathematical model of the controlled object (or process); it can easily control the object, which is probabilistic and very nonlinear; it has a stronger robustness to the change of natural parameter of the controlled object; it has the stronger suppression ability to the control system disturbance. The fuzzy control algorithm realization mainly is the fuzzy controller design. This system controller uses two-dimensional fuzzy controller form which has the double input and the lsingle output. The double input: the decination E (the difference between the temperature (humudity) and the setting value of the greenhouse) of the temperature (humudity) and the change rate of the decination EC of the temperature (humudity); the single output U: the controlled quantity of heating-up (humiditying) and coiling (dehumidification). Membership function uses triangle membership function, then fuzzy control rule is established according to the experience of the expert, meanwhile fuzzy control rule table is formed, thus the fuzzy control of the temperature (humudity) of the greenhouse is realized.Data processing software is compiled with the visual language, Visual Basic6.0. VB has quoted the Windows three big cores technology, such as visual technical, object-oriented method and event driver design. The interface design of the software is extremely convenient. The workload of programming is less. The development cycle is short. It definitely can satisfy the data acquisition speed which of the system function needs. In order to save the temperature(humudity) data and the testing-control information,, the database has established with Access took the backstage database, such as the user management database, the real-time gathering database, the historical data database, the parameter establishment database and the implementing agency condition database. The software includes six modules such as system function module, real-time data demonstration module, history data processing/inquiry module, report form output module, data acquisition establishment module, help document. These complete the communication inspection; establishment and revision user account; real-time display temperature(humudity) data and implementing agency condition; carries on the statistical analysis inquiry to the historical data; demonstrates the history trend curve; saving data by text or form; printing data by form or curve; printing report form of the day, the month and the year; establishment gathering time-gap, the top and low limit of the temperature(humudity) and the subsystem serial number; proofreading time; inquiring the system instructions.This system has lots of characteristics such as the strong versatility, the strong antjamming ability, and the low cost and so on, has the certain intellectualization, is suitable to each kind of the testing-control environment of the temperature and humidity.