Modeling and Predictive Control of a Variable-Rate Spraying System

In this paper, a mathematical model for a variable-rate spraying system is developed. The spraying system uses direct injection technology which allow the of different chemicals in a single application, reducing the waste of chemicals and thereby minimizing the toxicology and environmental risks associated with carrier-chemical mix preparation and discharge. In addiction, a predictive control strategy to adjust the carrier-chemical mix and chemical flow rates is proposed. To obtain the model and analyse the control strategy, a facility for site-specific application of chemicals which includes a laboratory scale sprayer test bench was designed and built. The automation of this system was based on a programmable automation controller suitable for control, acquisition and timing applications. With the predictive control approach, the errors of the carrier-chemical mix and chemical flow rates were lower than the admissible level of 5%. Practical results are presented to validate the models and show the efficiency of the control strategy proposed.