A compensator is a form of controller designed to alter certain characteristics (such as gain/phase) of the open-loop system. A compensator is a component in the control system and it is used to regulate another system. ... In order to make the system behave as desired, it is necessary to redesign the system and add a compensator, a device which compensates for the deficient performance of the original system. Control system compensation is the strategy used by the control system designed to improve system dynamic performance through the addition of dynamic elements in order to mitigate some of the undesirable features of the control elements present in the system.

1. Department of Avionics Engineering
AE-3452
Modern Control Systems
Experiment No.6
Design Compensator Using Automated PID Tuning for a water tank
Prepared for
By:
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Section:
Semester:
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Obtained Marks: _____________
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2. Design Compensator Using Automated PID Tuning for a water tank
Objective:
To design a compensator for a Simulink model using automated PID tuning in the Control System
Designer app. It then shows how to fine tune the compensator design using the open-loop Bode editor.
Theory:
A compensator is a form of controller designed to alter certain characteristics (such as gain/phase) of the
open-loop system. A compensator is a component in the control system and it is used to regulate another
system. ... In order to make the system behave as desired, it is necessary to redesign the system and add
a compensator, a device which compensates for the deficient performance of the original system.
Control system compensation is the strategy used by the control system designed to improve system
dynamic performance through the addition of dynamic elements in order to mitigate some of the
undesirable features of the control elements present in the system.
Lab Task:
Perform the Following case as per the steps defined in the manual and compensate the response of the
system with different controllers.
System Model:
Here we have assumed a model of water tank case in order to control water tank input according to the
output as well as the other parameters:
• H is the height of water in the tank.
• Vol is the volume of water in the tank.
• V is the voltage applied to the pump.
• A is the cross-sectional area of the tank.
• b is a constant related to the flow rate into the tank.
• a is a constant related to the flow rate out of the tank.
Water enters the tank from the top at a rate proportional to the voltage applied to the pump. The water
leaves through an opening in the tank base at a rate that is proportional to the square root of the water
height in the tank. The presence of the square root in the water flow rate results in a nonlinear plant. Based
on these flow rates, the rate of change of the tank volume is:
Design Requirements
Tune the PID controller to meet the following closed-loop step response design requirements:
• Overshoot less than 5%
• Rise time less than five seconds

3. System Model:
This model contains a Water-Tank System plant model and a PID controller in a single-loop feedback
system. To view the water tank model, open the Water-Tank System subsystem.
Open Control System Designer
To open Control System Designer, in the Simulink model window, in the Apps gallery, click Control
System Designer.
Control System Designer opens and automatically opens the Edit Architecture dialog box.
Specify Blocks to Tune:

4. To specify the compensator to tune, in the Edit Architecture dialog box, click Add Blocks. In the Select
Blocks to Tune dialog box, in the left pane, click the Controller subsystem. In the Tune column, check the
box for the PID Controller.
Click OK.
In the Edit Architecture dialog box, the app adds the selected controller block to the list of blocks to tune
on the Blocks tab. On the Signals tab, the app also adds the output of the PID Controller block to the list
of analysis point Locations.
When Control System Designer opens, it adds any analysis points previously defined in the Simulink
model to the Locations list:
• Desired Water Level block output — Reference signal for the closed-loop step response

5. • Water-Tank System block output — Output signal for the closed-loop step response
To linearize the Simulink model and set the control architecture, click OK.
By default, Control System Designer linearizes the plant model at the model initial conditions.
The app adds the PID controller to the Data Browser, in the Controllers and Fixed Blocks section.
The app also computes the open-loop transfer function at the output of the PID Controller block and adds
this response to the Data Browser.
Plot Closed-Loop Step Response
To analyze the controller design, create a closed-loop transfer function of the system and plot its step
response.
On the Control System tab, click New Plot, and select New Step.
In the New Step to plot dialog box, in the Select Response to Plot drop-down list, select New Input-
Output Transfer Response.
To add an input signal, in the Specify input signals area, click +. In the drop-down list, select the output of
the Desired Water Level block.

6. To add an output signal, in the Specify output signals area, click +. In the drop-down list, select the output
of the Water-Tank System block.
To create the closed-loop transfer function and plot the step response, click Plot.
Tune Compensator Using Automated PID Tuning
To tune the compensator using automated PID tuning,
click Tuning Methods, and select PID Tuning.
In the PID Tuning dialog box, in
the Specifications section, select the following
options:
• Tuning method — Robust response time
• Controller Type — PI

7. Click Update Compensator. The app updates the closed-loop response for the new compensator settings
and updates the step response plot.
Fine Tune Controller Using Compensator Editor:
To tune the parameters of your compensator directly, use the compensator editor. In the Bode Editor,
right-click the plot area, and select Edit Compensator.
In the Compensator Editor dialog box, on the Parameter tab, tune the PID controller gains. For more
information on editing compensator parameters, see Tune Simulink Blocks Using Compensator Editor.
Why we use Compensator?
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What parameters should be change to stable a system?
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