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Controlling the Operational Conditions of a Greenhouse

Fallah Ramezani, Saeed | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53952 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Shahrokhi, Mohammad; Vafa, Ehsan
  7. Abstract:
  8. Researchers have paid more attention to greenhouse cultivation, due to the exacerbation of food and water crisis. Higher production with lower cost could be achieved through greenhouse climate control (temperature, humidity, carbon dioxide concentration). However, greenhouse climate control is a challenging task, because greenhouses have highly interactive nonlinear dynamics and model uncertainties and are subject to input saturation. In light of the fact that Iran is a country with a warm and arid climate, tunnel greenhouses equipped with evaporative cooling system are very common in Iran. Accordingly, this type of greenhouse is considered for modelling, simulation and control in this thesis. For this purpose, a validated model was further improved by converting static modelling to dynamic one and by including carbon dioxide variation and crop growth in the greenhouse model. Results from dynamic modelling and static one showed that static model has not a good prediction in case of sudden changes. In addition, the impact of air flow rate on mixing of greenhouse air was studied. The Adaptive Generalized Predictive Control (AGPC) was adopted to control air temperature, relative humidity and carbon dioxide concentration in the greenhouse. Performance of AGPC in a tunnel greenhouse was simulated by MATLAB R2018b and was compared with on/off and PI combines with a decoupler. The results showed that even by using a decoupler, PI controller became unstable. Therefore, performance index of AGPC is significantly better than that of PI. In addition to input saturation, output saturation was also studied. It was shown that, instead of fixing a set-point for relative humidity, it is possible to set a range
  9. Keywords:
  10. Predictive Control ; Adaptive Control ; Simulation ; Modeling ; Greenhouse ; Operating Condition

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