The Quanser Coupled Tanks, shown below, is a reconfigurable nonlinear process control experiment. It’s one of the best experiments to explore PID for process control applications. Before getting into the Simulink-based controller, new students can benefit from using a GUI. The MATLAB App Designer provides an easy way to develop GUIs based on existing Simulink models.
How Does it Work?
The pump drives the water from the bottom basin up to the top outflow orifices and into tank 1 and/or tank 2. The water level of the tanks is measured using pressure sensors. The system can be configured to control the top tank as a single input single output (SISO) system. In this setup, the input is the pump outflow, and the output is the water level of tank 1. The Coupled Tanks can also be configured as a cascade system (i.e., control tank 2 via tank 1), or a shared input system.
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The Coupled Tanks uses PID and feed-forward control to regulate the level of water in the top tank. The Simulink model used to do this is shown below.
Running the App Designer
The App Designer was used to develop an App for the following configurations:
- Simulation: Using the nonlinear model of the system.
- Virtual Twin: Quanser QLabs Virtual Coupled Tanks
- Hardware: Using the Quanser QUARC Real-Time Control Software, the controller can be run on the Coupled Tanks hardware.
Simulation
Here is a sample response when running the simulation of the Coupled Tanks with the App.
The Tank 1 Level scope shows the response of the top level control of the Coupled Tanks. The blue line is the setpoint, i.e., desired water level. It can be changed using the Level Setpoint and Frequency controls. The red line is the simulated water level from the nonlinear model. Enable Simulation Pacing is ON to run the simulation in “actual” time.
Virtual Twin
The App for running the QLabs Virtual Coupled Tanks is shown below.
Hardware
Here is a sample response when running the App with the Coupled Tanks hardware. This shows the control of the top water tank level as it is starting up.
Want to explore process control concepts with a flexible, hands-on platform? Learn more about the Quanser Coupled Tanks system and see how it can support teaching and research in PID, cascade control, and nonlinear systems.
