Control Systems in LabVIEW

Transcription

1 Control Systems in LabVIEW with Self-paced Step-by-Step Exercises Hans-Petter Halvorsen, M.Sc.

2 Download the software here: LabVIEW Installation These are the main modules we use in the different courses at Telemark University College: LabVIEW (LabVIEW Professional Development System 32-Bit: English) NI-DAQmx (Hardware Driver for NI USB-6008, NI TC-01, etc.) LabVIEW Control Design and Simulation Module LabVIEW MathScript RT Module Note! These packages are separate downloads! Note! You get the Serial Number from your Teacher, but the software can be used for 30 days before you need to enter a valid Serial Number. All LabVIEW Software can be downloaded here:

3 LabVIEW Training Here you will find lots of Videos, Tutorials and Exercises LabVIEW Training for Students (National Instruments): LabVIEW Course: Learning by Doing! It is recommended that you watch some of the videos before you read furter

4 National Instruments is the vendor of LabVIEW National Instruments creates both Hardware and Software

5 Graphical Programming: LabVIEW = Fun! Very different from traditional programming like VB, C#, Maple, MATLAB, MathScript, etc. It is more like a drawing program than a Programming Language This makes it easy to use for those who are not programmers (or dont like programming J) Excellent tool when using Hardware, when you need to take Measurements (DAQ), etc. It is fun and makes you very creative!

6 LabVIEW Example LabVIEW has the same things as other programming languages, but in a graphical way! Sequence Structure Comment While Loop Sub VI (Function/Method) Local Variable Arrays Case Structure Stop Button Property Nodes Constants (if-else) Condition Note! To do something with an object Right-click on it (When shall the loop end?)

7 Hardware Air Heater Wi-Fi DAQ Water Tank Pt-100 USB-6008 TC-01 Arduino ZigBee Vision System crio NOx Sensor

8 LabVIEW This is the core LabVIEW installation that installs the LabVIEW Programming Environment. LabVIEW MathScript RT Module This module is a text-based tool that is very similar to MATLAB. The syntax is similar to MATLAB, you can create and run so-called m files, etc. The module is available from the Tools menu inside LabVIEW. LabVIEW Control Design and Simulation Module This module is used for creating Control and Simulation applications with LabVIEW. Here you will find PID controllers, etc. The module is available as a palette on your block diagram. NI-DAQmx DAQmx is the Hardware Driver needed in order to use hardware devices like NI USB-6008, NI TC-01, etc. inside LabVIEW. The module is available as a palette on your block diagram.

9 Students: Try some of these Shortcuts and Tools

10 Control Systems Hans-Petter Halvorsen, M.Sc.

11 DAQ Data Acquisition Sensors, etc. Your App created with LabVIEW A DAQ System consists of 4 parts: NI TC-01 Thermocouple Device, 1. Physical input/output signals, sensors NI USB 6008 DAQ Device, etc. 2. DAQ device/hardware 3. Driver software 4. Your software application (Application software) NI DAQmx Driver

12 Implementing a Control System While the real process is continuous, normally the Controller and the Filter is implemented in a computer.

13 Types of Industrial Control Systems PLC DCS SCADA

14 Industrial Control Systems (ICS) Industrial Control Systems are computer controlled systems that monitor and control industrial processes that exist in the physical world crio LabVIEW Programmable Automation Controller (PAC) Industrial PID Controller Distributed Control Systems (DCS) Controller PC based Control System/SCADA System (Supervisory Control And Data Acquisition) I/O Module PLC (Programmable Logic Controller) I/O Modules DeltaV Siemens PLC

15 PC-based Control System Industrial PID Controller PID Control using LabVIEW and I/O Module

16 PC-based Control System Process Examples 0-5V/1-5V 0-5V Analog In Measurement(s) - Analog Out + - Control Signal + Controller (PID) and Lowpass Filter Implementation I/O Module AD Converter USB-6008 DA Converter USB

17 PC-based Control System

18 PC-based Control System LabVIEW Example (Simulation) Mathematical Model of the Process Feedback Loop Feedback Node

19 PC-based Control System LabVIEW Example (Real process) SubVI that handles the I/O between LabVIEW and the Real Process included Filter and Scaling

20 PC-based Control System LabVIEW Example (HMI/GUI)

21 PID Control in LabVIEW Hans-Petter Halvorsen, M.Sc.

22 PID Control using LabVIEW Built-in PID Controllers: Discrete PI created from Scratch

23 Control System Controller v r e u y - K p T i T d PID Process Sensor

24 Control System implementation with Pen & Paper v K p T i T d r e u y PID Process - Sensor Control System implementation in LabVIEW A Simulation Loop is used in this Example

25 Controller Control System implementation with Pen & Paper v K p T i T d r e u y PID Process - Sensor Control System implementation in LabVIEW A While Loop is used in this Example

26 Alternative 1: PID Palette in LabVIEW (PID Toolkit) PID Control in LabVIEW Alternative 2: This alternative uses seconds! Note! The functions PID.vi and PID Advanced.vi requires that Ti and Td is in minutes, while it s normal to use seconds as the unit for these parameters. You can use the following piece of code in order to transform them: This means we enter values for Ti and Td in secons on the Front Panel and the values are converted to minutes in the code.

27 Help -> Find Examples... PID Control Demo Students: Try the General PID Simulator example that is included with LabVIEW

28 PID Controller Alternative 1a PID Advanced VI + While Loop

29 PID Controller Alternative 1b Right-click and select SubVI Node Setup PID Advanced VI + Simulation Loop

30 PID Controller Alternative 2a PID block + While Loop

31 PID Controller Alternative 2b PID block + Simulation Loop

32 Discretization Hans-Petter Halvorsen, M.Sc.

33 AD & DA Converters Measurement Signal AD Converter Control Signal DA Converter USB AD Analog to Digital DA Digital to Analog

34 Continuous Signal Note! Different books use different notations Discrete Signal A computer can only deal with discrete signals Ts = Sampling Time When Ts -> 0, we have a continuous signal, but in a computer that is not possible. k = 0, 1, 2, 3, 4,...

35 Discretization Methods Euler forward method: Euler backward method: Other methods are Zero Order Hold (ZOH), Tustin s method, etc.

36 Given the following continuous system: Discretization Example We will use the Euler forward method :

37 Discrete Syntax Note The following:

38 Discretization in LabVIEW using the Formula Node Implementing discrete equations in LabVIEW using C syntax Example:

39 Discrete Lowpass Filter Hans-Petter Halvorsen, M.Sc.

40 Discrete Lowpass Filter Lowpass Filter Transfer function: We define: Inverse Laplace the differential Equation: We use the Euler Backward method: This gives: Filter output Noisy input signal This gives: This algorithm can be easily implemented in a Programming language

41 Discrete Lowpass Filter - LabVIEW

42 Testing the Discrete Lowpass Filter We see the Filter removes the noise

43 Discrete PI Controller Hans-Petter Halvorsen, M.Sc.

44 Discrete PI Controller Continuous PI Controller: We may set: This gives the following discrete PI algorithm: We use the Euler Backward method: This algorithm can be easily implemented in a Programming language

45 Discrete PI Controller LabVIEW

46 Test of Discrete PI Controller in LabVIEW PID Controller created from scratch in LabVIEW Mathematical Model of the Process Feedback Loop Feedback Node

47 PC-based Control System LabVIEW Example (HMI/GUI)

48 Do you need more Practice? - Select a Challenge Hans-Petter Halvorsen, M.Sc.

49 Create a PC based Control System as illustrated below:

50 Hans-Petter Halvorsen, M.Sc. University College of Southeast Norway Blog: