The Design And Research Of Greenhouse Node And Control Strategy Based On Field Bus Technology

The idea that the field bus is introduced into the field of greenhouse climate control in facility agriculture is present in the dissertation ,and a node control system of greenhouse field based upon field bus technology is designed. The temperature dynamic model based on balance of heating exchange in greenhouse is set up ,and the dynamic model of pipe vapour temperature of heating system is set up. Based on this, the general fuzzy control method of heating system is improved, the dissertation present the strategy that fuzzy control combine with smith pre-estimate controller to compose fuzzy-smith pre-estimate control system. The content of the dissertation including:Based on discussing the present study of greenhouse climate control, the first chapter introduces the importance that the field bus technology is applied to greenhouse climate control ,and expatiates the significance, purpose and content of the paper.The second chapter discussed define, characteristic and virtue of field bus, analyzed constitution of field bus control system and difference with traditional DCS. The conclusion is that CAN is the field bus that adapts to greenhouse climate control after several popular field bus is analyzed, the characteristic and technical specification of CAN bus is discussed.In the third chapter, according the systemic general plan, the hardware circuit and the software program of node of field layer is designed. Hardware circuit include process channel module based upon 1-wire, communication module based upon CAN feus, data store module based on I2C bus, human-computer interaction module, I/O extended module and so on. Using C and Visual C-H- 6.0, the software of node's modules and communication of central monitor layer are programmed, respectively. CAN communication protocol use PeliCAN mode of CAN2.0B protocol, the format ofmessage is extended frames. At last node system is debugged.The forth chapter analyzes the physics processes of heating exchange in gfeenhouse ,uses the principium method to set up the dynamic model of greenhouse temperature based on heating balance. Based on this model ,the model of greenhouse temperature is set up when the heating system is using. Considering the vapour heating as the modeling object ,the dynamic formula between vapour temperature and vapour flux of the pipe is set up.The fifth chapter concerns on control algorithms of greenhouse heating system .The dissertation presents fuzzy control strategy because greenhouse has the characteristic of time-delay, time-varying, and uses general fuzzy control strategy, fuzzy-smith ppe-estimate control strategy respectively to simulate greenhouse heating system according to the temperature model set up in the forth chapter. It is proved that fuzzy smith pre-estimate method is better than general fuzzy control method in the capability of adaptation and the characteristic of dynamic and static state.The sixth chapter gives conclusion and expectation of the dissertation.