Modeling of Automatic Sprinkler Irrigation Process Using Finite State Machine (FSM) and Proportional Integral Derivative (PID) Controller

In this paper, the real-time automatic irrigation system was designed to supply water to the root zone of plant only when soil moisture content goes below a certain level known as critical moisture content. Particularly, models for the DC motor driven centrifugal irrigation pump, sprinkler irrigation nozzle, plant water uptake process, a proportional-integral-derivative (PID) controller were obtained using analytical methods. Automatic control logic was designed using the finite state machine (FSM) concept to act as a supervisory controller for the real-time automatic irrigation system. The models for the different sections of the system were assembled on MATLAB workspace, and then simulated and tested to ascertain the workability of the system. Specifically, the model was simulated for 0.5 seconds and the step response and impulse response were also computed. The results showed that the system performance is quite suitable for the irrigation system because a response time of 2 seconds offer a 1.36 seconds rise time for the system to reach its peak unit amplitude of 1.06, although with a much longer settling time of 4.21seconds. The results also showed that 1.7145×105mm3H2O/mm3Soil was consumed by the plant within the simulation period. In all, the simulation results obtained showed that the irrigation system was able to supply the needed water to replenish the soil moisture deficit without frequent human intervention. The models presented in this research are useful for planning, designing and analysis of automatic irrigation system for mechanized farming.