PERFORMANCE STUDIES ON WATER FLOW CONTROL USING P, PI AND PID CONTROLLERS

The main purpose of this study is to revitalize the concept of wise and controlled supply of water for domestic, industrial and agricultural applications which facilitate sustainable usage of fresh water resources. As Eritrea is striving to manage its water resources, attention paid primarily to enable water flow control mechanisms in municipal water distribution systems. A table top process control trainer (PCT) was tested through proportional(P), integral (I) and derivative (D) control mechanisms using Ziegler-Nichols second method to evaluate the tuning variables. Applying exclusively P control action, critical period of oscillation () was estimated as 1.4 sec at proportional band value of 9. P, PI and PID controller performance studies were conducted with tuned variables on the water flow control system at different step disturbances between 20 – 50 % and their corresponding responses were characterized. P controller exhibited faster responses with consistent increments in offset, PI controller recorded highest overshoot values with negligible offset and prolonged settling times. PID controller showed less overshoot values and faster response times than PI but it increased chatter on the control output signal. The study revealed that the system can be safely controlled between 0-80 LPH. If the offset is not a major concern, P controller would be reflected suitable with simple design and minimum expenditure, else PI controller makes offset to zero though it possesses higher settling times. In other words, PID controller is complex using more tuning parameters, need expensive maintenance, and has resulted an intermittent noise in the output signal.