Tutorial 06

Tutorial 6 - On-Off Control System (JEE344 Applied Control Engineering) Aim • •

To design and simulate an On-Off control system To use simulation as a diagnostic tool to improve control system performance

Learning Outcomes • Simulate a Level Level Transmitter, an I/P converter and a Pneumatic Control Control Valve • Program the On-Off control algorithm with an Auto/Man model switch • Enhance Simulator • Create a project and build applications (executable files) On-Off Control Algorithm – Design and Simulation with LabVIEW

Block diagram algorithm for On/Off Control with Auto/Man mode switch: ON/OFF SP

Subtract

Auto/Man

Greater?

Select

ON

PV 0

Select Auto

OFF

OP (Control signal)

4 To Actuator Figure 1 On-Off control block diagram algorithm

The following shows the level control system with all components: pc Cross-sectional A

qi

Liquid supply 20-100 kPa Pneumatic supply 140 kPa

hm I/P

LC

4-20mA

PC

LT

4-20mA

Tank  h qo Resistance R

Figure 2 Liquid level control system

1

Ps [kPa] [V]

[mm] Hsp Km

H sp

+_

[V]

[V]

[V] > [mA]

[kPa]

E

U

Pc

C

A/M

KIP

[kPa] Kv

Qin

[mm] H G

On/Off  [V] < [mA] Hm

Km

Figure 3 Block diagram of the level control system Hands-on Exercise 1 On-Off Control System (Simulation Module)

Open “TankLevelSysSim04.vi” (or an appropriate file name) you created at the end of  Tutorial 5a and save as “OnOffTankLevelSysSim01.vi” 1. Add a Level Transmitter (converts level in mm to mA, then V)

Figure 4 Level transmitter simulator

2. Add a Current-to-Pressure Converter (convert mA to kPa with a pneumatic supply pressure of 140 kPa and an output of 20-100 kPa)

Figure 5 I/P converter

Save the VI. 3

3

3. Add a Pneumatic Control Valve (input: 20-100 kPa, output: qin: 0-0.0071 m  /s > m  /s)

2

Figure 6 Pneumatic control valve

Save the VI. 4. Add an Auto/Man mode switch (using a Select function)

Figure 7 An Auto/Man mode switch using a Select function

Save the VI 5. Add an On-Off Controller (SP [mm] > [V], comparator, On-Off controller)

Figure 8 ON-OFF Controller

Save the VI. 6. Add setpoint level signal and measured signal to the level-chart 7. Add a chart for control signal, setpoint, and measured level [V]. The resulting simulation program looks like... (see Fig. 9 and Fig. 10). Save the VI. Run the VI and test its functionality.

3

Figure 9 Simulation program – Block Diagram Windows

Figure 10 Simulation program – Front Panel

4

Hands-on Exercise 2 Create a Project

Close the VI. Open an Empty Project. Save as “MyFirstProject01”. The project looks like:

Figure 11 An empty project

To create a New VI in project, Right click My Computer > New VI:

Figure 11 New VI in a project However we are not going to create a new VI, we add a VI (On-Off Level Control System Simulator) we have created. 5

Figure 12 Add a file into a project

Information Source File > Build

Figure 13 Source file

6

Figure 14 Build status

When the Build Application is done, test the EXE file that has been created. If it works properly, the build application is successful. This EXE file requires LabVIEW Run-Time Engine 8.6 that can be downloaded from the NI website when it is run in a computer without LabVIEW: http://joule.ni.com/nidu/cds/view/p/id/1101/lang/en Conclusions

At this point, the following LOs have been met: Simulate a Level Transmitter, an I/P converter and a Pneumatic Control Valve • Program the On-Off control algorithm with an Auto/Man model switch • • Enhance Simulator • Create a project and build applications (executable files) Follow-up Exercise

Create a new project for simulation of the drying oven system in Example 15 (Lecture Notes) and build an executable file for the dying oven system.

7