Greenhouse Environmental Control Systems

Greenhouses are extremely complex and nonlinear living systems whose behaviors change in time depending on numerous disturbances, generally weather-related. It is therefore difficult to control greenhouse environments with classical controllers; hence, complex and smarter approaches are required in order to bring the indoor and outdoor stakeholders such as whether, the cost of energy, water, CO₂, and others all together and make proper adjustments in greenhouse environment instantly for healthy crop development and therefore a profitable operation. Smart digital greenhouse environmental control systems are available today, and they control every single parameter in an integrated fashion in modern commercial greenhouses providing smart decision-making processes for optimum growth conditions. Further precision controls and therefore savings can be achieved via incorporating smarter strategies with artificial intelligence (AI) algorithms into the environmental control systems. The consequence of every management step and strategy needs to be evaluated and dynamically optimized in an integrated fashion with continuous environmental monitoring before it is actuated. Today, the remote monitoring and control systems are on duty day and night continuously; and with the help of AI, computer vision, and enhanced sensor integration, our greenhouses will soon become more flexible and autonomous operations, and therefore more universal and sustainable. However, before something is controlled, its position needs to be sensed first somehow, so that proper adjustments can be made in its position. And these sensing devices are called as sensors, which are essential components of any greenhouse monitoring and control systems. These sensors measure conditions of different environmental variables such as temperature, relative humidity, light intensity, CO₂ concentration, and wind speed. Today, both hardwired and wireless monitoring and control systems are available, and commercial greenhouse operations have either one of these types or sometimes the combination of both. Sensor accuracy and reliability under greenhouse conditions are particularly important due to the unfavorable environmental conditions in greenhouses.

This chapter briefly covers control theory and classification first, then moves to classical and modern control theories and system classifications, and concludes with future evolution of control systems.