Flatness-Based Single Tank Water Level Control Under Actuator Constraint

This paper addresses water level regulation in a single tank. The classical solution is to linearize the non-linear dynamic and regulate the water level with a classical PID controller. If the actuator's saturation, e.g., the pump, is taken into account, the PID controller should have the anti-windup mechanism. A normal PLC and SCADA system cannot solve radically the monitoring and control under the constraint problem. We propose a PC-based flat controller approach. The whole control system is written in Python which controls the variable frequency drive directly using Modbus RTU and permits to locally/remotely monitor the control system at the same time. Communication employs MQTT protocol to send operational data to a remote LAMP server. A prototype is built to verify the performance of our controller which used low-cost flow sensors and an Arduino-based signal conditioning circuit. Kalman filter is then used to enhance input and output measuring.