# Coupled Tanks

See it in action

## Give Students Control of a Real World Application

The Coupled Tank, designed in association with Prof. Karl Åström and Prof. Karl Henrik Johansson, is a bench-scale model of two tanks with a pump, ideally suited to introduce control concepts and theories related to fluid dynamics, pressure and time delays, encountered in real world industrial applications, such as petro-chemical, paper making and water treatment plants. Students learn how to:

• mathematically model the Coupled Tanks plant from first principles in order to obtain the two open-loop transfer functions characterizing the system, in the Laplace domain
• linearize the obtained non-linear equation of motion about the quiescent point of operation
• design, through pole placement, a Proportional-plus-Integral-plus-Feedforward-based controller for the Coupled Tanks system in order for it to meet the required design specifications for various possible configurations
• implement controllers and evaluate their actual performance

In addition to teaching control concepts, the Coupled Tanks can be used for research in various areas, including optimal control and intelligent control.

## Configurations for Several Control Challenges

A single Coupled Tanks unit can be configured into three types of experiments:

• Single-Input-Single-Output (SISO) system, where the pump feeds into the upper tank and the lower tank is not used
• State-coupled SISO system, where the pump feeds into the upper tank, which feeds into the lower tank.
• State-coupled and input-coupled SISO system, where the pump feeds into both upper and lower tanks using a split flow, plus the upper tank also feeds into the lower tank.

Additionally, two or more Coupled Tanks units can be used simultaneously to obtain a more complex Multi-Input-Multi-Output (MIMO) experiment.

How It Works

The Coupled Tanks system consists of a single pump with two tanks, forming an autonomous closed and recirculating system. The pump drives the liquid from the bottom basin up to the top of the system. Depending on how the outflow valves are configured, the liquid then flows to the top tank, bottom tank, or both. The flow rate can also be changed using outflow orifices with different diameters. In order to introduce a disturbance flow, the upper tank is also equipped with a drain tap which, when opened, releases the liquid directly into the water basin.

Each tank is instrumented with a pressure sensor to measure the liquid level. The sensors are located at the bottom of the tanks. Both offset and gain potentiometers of pressure sensors are readily available for proper calibration. Additionally, a vertical scale (in centimeters) is placed beside each tank for visual feedback regarding the tank's liquid level.

## Quanser-developed ABET-aligned Courseware Included

The Coupled Tanks system comes with Quanser-developed courseware standardized for ABET evaluation criteria. The workbook with exercises, together with quick start resources, a comprehensive User Manual, pre-designed controllers and a system model allow you to get your lab running faster, saving months of time typically required to develop lab materials.

• Overall frame constructed from solid plexiglas
• Two tanks and single pump design
• Pressure / level sensors on each tank
• Re-configurable water flow from pump and tanks
• Drain tap allows water from top tank to pour directly into basin
• Three sizes for outflow orifices supplied (small, medium, and large)
• Pressure sensors can be calibrated (using gain and offset knobs)
• Easy-connect cable and connectors
• Fully compatible with MATLAB®/Simulink® and LabVIEW™
• Fully documented system models and parameters provided for MATLAB®, Simulink®, LabVIEW™ and Maple™
• Open architecture design, allowing users to design their own controller
 Device mass 6.6 kg Frame dimensions (H x W x L) 30.5 cm x  30.5 cm x  91.5 cm Pump flow constant 3.3 cm³/V.s Pressure sensor sensitivity 6.1 cm/V Pressure sensor range 0 to 6.89 kPa Tank height 30 cm Tank inside diameter 4.45 cm Small outflow orifice diameter 0.32 cm Medium outflow orifice diameter 0.48 cm Large outflow orifice diameter 0.56 cm

Topics included in the Quanser-developed courseware:

• Derivation of dynamic model from first-principles
• Transfer function representation
• Linearization
• Level control
• PID
• Feed-forward
• Control parameter tuning
##### The Coupled Tanks can be also used to teach other topics that are not included in the Quanser-developed courseware.

To set up your Coupled Tanks workstation, you need additional components. Quanser engineers recommend:

 for MATLAB®/Simulink® users for LabVIEW™ users 1x Q2-USB data acquisition device¹ 1x VoltPAQ-X1 linear voltage amplifier 1x VoltPAQ-X1 linear voltage amplifier Quanser Rapid Control Prototyping toolkit software QUARC real-time control software and one of the following options: - 1x NI myRIO with 1x Quanser Terminal Board for NI myRIO - 1x NI CompactRIO² controller with 2x Quanser Q1-CRIO module - 1x NI M- or X-series data acquisition device³ with 1x Quanser NI Terminal Board

¹ alternatively, you can use Q8-USB, QPIDe or any equivalent NI DAQ device supported by QUARC
² NI cRIO-9074, or NI cRIO-9024 with cRIO-9113 or cRIO-9114 chassis
³ NI DAQ device must be supported by Quanser RCP toolkit. Alternatively, you can use Quanser Q2-USBQ8-USB, or QPIDe

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