Handling description MPS PA Compact Workstation Closed loop control with Simatic PLC CPU 313C
Order no.: Description:
MPS PA Compact Workstation – Closed loop control with Simatic PLC CPU 313C
Designation:
Handling description
Status:
05/2008
Author:
Wolfgang Eckart, Festo Didactic GmbH & Co KG
Graphics:
Wolfgang Eckart, Festo Didactic GmbH & Co KG
Layout:
Festo Didactic GmbH & Co KG
© Festo Didactic GmbH & Co., D-73770 Denkendorf, 2008 Internet: www.festo.com/didactic http://www.festo.com/didactic/de/ProcessAutomation e-mail:
[email protected] All rights reserved, including translation rights. No part of this publication may be reproduced or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without the prior written permission of Festo.
Table of Contents
Table of Contents _____________________________________________________ 3 Introduction__________________________________________________________ 5 Introduction _______________________________________________________ 5 Training contents___________________________________________________ 6 Safety instructions__________________________________________________ 7 PLC control general information _______________________________________ 8 Software Installation___________________________________________________ 9 Workstation set-up ___________________________________________________ 13 1.
Installation of Step 7 _______________________________________ 9
2.
Preparation of the workstation ______________________________ 13
2.1
Connection of the PLC______________________________________ 13
2.2
Fill up the tank 101 ________________________________________ 14
2.3
Close of the manual hand valves _____________________________ 15
2.4
Delete the contents of the CPU ______________________________ 16
2.5
Hardware configuration of the PLC ___________________________ 23
2.6
Edit the Symbol Table______________________________________ 41
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Table of Contents
Definition of process variables __________________________________________ 51 3.
Normalisation and definition of the process variables factors______ 51
3.1
Adjustment of the ultrasonic sensor __________________________ 57
3.2
Definition of the normalisation factor _________________________ 68
3.2.1
Normalisation factor level control ____________________________ 68
3.2.2
Normalisation factor flow control ____________________________ 69
3.2.3
Normalisation factor pressure control_________________________ 97
3.2.4
Normalisation of the temperature factor______________________ 106
2-Step Control ______________________________________________________ 107 4.
Level control by a 2-step controller __________________________ 107
Continuous Control __________________________________________________ 121
4
5.
Continuous control _______________________________________ 121
5.1
Continuous pressure control _______________________________ 124
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Introduction
Introduction
The Festo Didactic learning system for process automation is designed to meet a number of different training and vocational requirements. The systems and stations of the learning system for process automation facilitate industry-orientated vocational and further training and the hardware consists of didactically suitable industrial components. The Compact Workstation of the learning system for process automation provides you with an appropriate system for practice-orientated tuition of the following key qualifications Social competence, Technical competence and Methodological competence Moreover, training can be provided to instill team spirit, willingness to cooperate and organisational skills. Actual project phases can be taught by means of training projects, such as: Planning, Assembly, Programming, Commissioning, Operation, Maintenance and Trouble Shooting
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Software installation
Training contents
Training contents covering the following subjects can be: Process Engineering – Reading and drawing of flow charts and technical documentation Electrical technology – Correct wiring of electrical components Sensors – Correct use of sensors – Measuring of non-electrical, process and control variables Closed-loop control technology – basics of closed-loop control technology – Extension of measuring chains into closed control loops – Analyze a closed-loop system – P, I, D-control – Optimize a closed-loop system Closed-loop controller – Configuration, assigning operation parameters and optimization of a closed-loop controller Commissioning – Commissioning of a closed-loop system – Commissioning of a process engineering system Trouble Shooting – Systematic trouble shooting on a process engineering system – Maintenance of a process engineering system – Operation and observation of a process
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Software installation
Safety instructions
General Participants must only work on the station under the supervision of an instructor. Observe the data in the data sheets for the individual components, in particular all notes on safety! Electrics Electrical connections and dis-connections are only allowed when when the power is disconnected! Use only low voltage of up to 24 V DC. Pneumatics If you use pneumatic components within your system, please do not exceed the permissible pressure of 8 bar (800 kPA). Do not switch on compressed air until you have established and secured all tubing connections. Do not disconnect air lines under pressure. Particular care is to be taken when switching on the compressed air. Cylinders may advance or retract as soon as the compressed air is switched on. Mechanics Securely mount all components on the plate. No manual intervention unless the system is in Stop mode. The pump can be mounted horizontally or vertically. If mounted, the output of the pump must point upwards. For further information please refer to the corresponding data sheet of the pump. Process engineering • Before filling the tanks with water, switch of the 24 VDC power supply and disconnect the 220 (230) VAC power from the socket • The use of tap water in quality of drinking water (recommended), ensures a prolonged maintenance-free operation of the system (proportional valve and pump). • The maximum operating temperature of the tanks must not exceed +40 °C. • Do not operate the heating unit unless the heating element is fully immersed in fluid. • Do not operate the piping system with a system pressure higher than 0,5 bar. • Do not operate the pump without fluid, running dry or used for sea water or contaminated fluids. • Please empty fluids from the system (tanks, piping, close valves) before you make changes at the piping system. • It is possible to drain the fluids inside the workstation by opening the manual hand valve V105
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Software installation
PLC control general information
The use of a PLC S7 (CPU 313C or CPU 314C or CPU 314C-2DP) with the software Step 7 offers you the possibility to measure, analyze and control all digital and analog signals of the workstation. With the Compact Workstation of the learning system for process automation you have the possibility to work with the following closed loop process: • • • •
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level controlled system flow rate controlled system pressure controlled system temperature controlled system
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Software Installation
1.
Installation of Step 7
Please insert the Step 7 CD into the drive and follow the screen to install the entire programs of Step 7. Mostly you don´t need to install Adobe Reader because it already exists in most cases. So please deactivate the installation of Adobe. If a message appears to install the Authorisation of the Step 7 software, please choose the menu No Transfer License key later After the installation of Step 7 is complete, please install the iMAP software and follow the screens. If a message appears to install the Authorisation of iMAP software, please choose the menu No Transfer License key later After the installation is complete, please insert the USB flash drive of Step 7 in an USB port and wait until Windows is ready to use it. Proceed like shown on the next page and ff:
Start Æ Simatic Æ License Management Æ Automation License Manager
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Software installation
(Click on the Removable drive) Æ (click on the SIMATIC Step 7 Professional Edition Floating licens) Æ License Key Æ Transfer (don´t get confused because the window is in german language, the command is Transfer in English)
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Software installation
(Choose your local drive )C:) Æ OK Æ (after the transfer is finished click on the local drive in the left window and check if the license has been transferred. To remove the license from the local drive C, please proceed accordingly)
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Software installation
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Workstation set-up
2.
Preparation of the workstation
After unpacking the Compact workstation, please proceed to set-up the system as follows:
2.1
Connection of the PLC
Required hardware: • PC (minimum: Pentium 200MHz, 32MB RAM, 600x800 graphics) with USB interface and a CD-ROM drive • 24V power supply unit for the PLC • PLC (CPU 313C or CPU 314C or CPU 314C-2DP Edutrainer) • Signal unit
1 2 3 4 5
Connection of the digital in- and outputs of the workstation with the PLC Connection of the signal unit digital in- and outputs with the PLC Connection of the analog in- and outputs of the workstation with the PLC PC/MPI data cable connection of the PLC with the PC Connection to the power supply
At the end, please switch the CPU to RUN.
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Workstation set-up
2.2
Fill up the tank 101 After all cable connections have deen done, please fill the tank 201 with water until the safety sensor B214 can detect water. Please switch off the 24 VDC power supply and disconnect the 220 (230 VAC) power line from the socket during the filling process.
Remark: The photo shows the old designation of mm instead of liter!!!
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Workstation set-up
2.3
Close of the manual Please close all manual hand valves within the system as shown within the picture. hand valves
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Workstation set-up
2.4
Delete the contents After the example project has been running perfectly, we are going to start with our of the CPU own projects. To do so, we have to delete the entire contents of the CPU memory first. Please follow the screen shots to do so. Before you delete the CPU memory make sure, that you have the example projects already saved on a data drive (CD or hard drive). Before we proceed, please close the last active project.
PLC Æ Display Accessible Nodes
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Workstation set-up
MPI = 2 (double click on MPI = 2) Æ Blocks Æ (mark the entire contents of the CPU) Æ (right mouse button) Æ Delete
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Workstation set-up
Yes
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Workstation set-up
Yes
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Workstation set-up
OK
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Workstation set-up
(The SFC and SFB modules can not be deleted, only the user programs have been deleted, by means of the CPU is empty now)
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Workstation set-up
X (close the Accessible Nodes window)
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Workstation set-up
2.5
Hardware Please define the PLC-hardware used within your station with the STEP 7 software. configuration of the After the configuration, please download it into the PLC. PLC To do so, please edit a new project and name it PCC_Hw Remark: Please check what kind of PLC and additional modules you use. Refer to the following page. We are going to show the hardware configuration for the Compact Workstation using a CPU 313C as an example for all other stations. Please use the following names of the Step 7 project for all other stations: Distribution station Testing station Buffer station Seperating station Pick&Place station Fluidic Muscle station Handling station Sorting station Storage station Filling station Packaging station In/Out station AFB ASRS MPS 500 ASRS Conveyor station MPS PA Compact Workstation MPS PA Pressure station MPS PA Temperature station MPS PA Flow station MPS PA Level station MPS PA Filtration station MPS PA Mixing station MPS PA Reactor station MPS PA Quality Probe station MPS Bulk Gravity Feeder station MPS Bulk Vibration Feeder station MPS Bulk Quality Control station MPS Bulk Dosage station
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= = = = = = = = = = = = = = = = = = = = = = = = = = = =
Dis_Hw Tes_Hw Buf_Hw Sep_Hw P_P_Hw FMS_Hw Han_Hw Sor_Hw Sto_Hw Fil_Hw Pac_Hw I_O_Hw AAS_Hw MAS_Hw Con_Hw PCC_Hw PCP_Hw PCT_Hw PCF_Hw PCL_Hw PAF_Hw PAM_Hw PAR_Hw PAQ_Hw BGF_Hw BVF_Hw BQC_Hw BDO_Hw
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Workstation set-up
As an example of how to find the name of the CPU and the corresponding order number, please refer to the following picture
1 2 3 4 5 6
= = = = = =
Name of the CPU – here CPU 313C-2DP Order number of the CPU Name of additional I/O module Order number of the additional I/O module Name of additional I/O module Order number of the additional I/O module
Remark: Please make a list of modules you use including the order number.
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Workstation set-up
Definition of a new project:
File Æ New
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Workstation set-up
PCC_Hw (type in the name of the project – here PCC_Hw for MPS PA Compact Workstation as an example for all other stations) Æ (please check the directory – it should be C:\Programs\Siemens\Step7\S7_Proj) Æ OK
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Workstation set-up
Insert Æ Station Æ 2 SIMATIC 300 Station
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Workstation set-up
+ PCC_Hw-Æ SIMATIC 300(1) (click onto the station) Æ Hardware (double click)
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Workstation set-up
+ SIMATIC 300 Æ + RACK-300 Æ Rail (double click)
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Workstation set-up
+ CPU 313C (Now you are going to need your list of what kind of CPU do you use. Please choose the correct CPU with the corresponding order number and place it onto slot number 2 – here CPU 313C with the order number of 6ES7 313-5BE010AB0as an example)
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Workstation set-up
(Now we are going to define some contents of the CPU itself) Æ CPU 313C (double click on your CPU you use – here CPU 313C-2DP) Æ Cycle/Clock Memory Æ (activate the Clock memory and type in the address of the clock memory – here 100, which is free defineable)
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Workstation set-up
Retentive Memory Æ (type in a 0 like shown in the screen shot, because we don´t want to use any memory resistant Memories, Timers or Counters)
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Workstation set-up
Cycle Interrupt Æ (type in a 50 like shown in the screen shot) Æ OK
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Workstation set-up
Station Æ Save and Compile
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Workstation set-up
PLC Æ Download
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Workstation set-up
(Choose your CPU you use – here CPU 313C) Æ OK
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Workstation set-up
OK
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Workstation set-up
OK
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Workstation set-up
Yes
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Workstation set-up
Station Æ Exit
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Workstation set-up
2.6
Edit the Symbol Table
Instead of using the real hardware addresses within the PLC programming, it´s much better to use so called symbols for the in- and outputs. To use the symbolic addressing, it´s much easier to understand and read the program. This is essential, because a lot of staff working in a company using the programs, but didn´t edit the programs by themselve. Please use the following list of all inputs and outputs used at your station.
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Workstation set-up
In the following exercises we are going to use only some of the in- and outputs listed below.
Inputs of the Control panel Symbol
Adress
Comment
START
I125.0
Start button Touch panel
STOP
I125.1
Stop button Touch panel
AUTOMAN
I125.2
Auto/Manu switch Touch panel
RESET
I125.3
Reset button Touch panel
Analog Inputs of the station Symbol
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Adress
Comment
AI_Level
PIW 752
Analog input channel 0 level sensor
AI_Flow
PIW 754
Analog input channel 1 flow sensor
AI_Pres
PIW 756
Analog input channel 2 pressure sensor
AI_Temp
PIW 758
Analog input channel 3 temperature sensor
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Workstation set-up
Binary Outputs of the station Symbol
Adress
Comment
Valve
Q124.0
Solenoid ball valve
Heating
Q124.1
Output = 0 Heating off, Output = 1 Heating on
PumpPres
Q124.2
Pump preset = 0=digital/1=analog
PumpDig
Q124.3
Pump digital, only when PumpPreset = 0
Propval
Q124.4
Activate proportional valve
Outputs of the Touch panel Symbol
Adress
Comment
L_START
Q125.0
Light inside Start button Touch panel
L_RESET
Q125.1
Light inside Reset button Touch panel
L_Q1
Q125.2
Light Q1 Touch panel
L_Q2
Q125.3
Light Q2 Touch panel
Analog Outputs of the station Symbol
Adress
Comment
AQPump
PQW 752
Analog output channel 0 pump
AQValve
PQW 754
Analog output channel 1 prop.valve
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Workstation set-up
+ SIMATIC 300(1) Æ + CPU 313C Æ S7 Program(1) Æ Symbols (double click)
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Workstation set-up
(Please edit all the inputs and outputs of your station)
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Workstation set-up
(After all in- and outputs have been edited, save the Symbol Table) Symbol Table Æ Save Æ Symbol Table Æ Exit
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Workstation set-up
Remark: To prepare for the project, we are going to save the existing project PCC_Hw with a new name of PCC_PrLe for project level control.
PCC_Hw (click onto the project)
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Workstation set-up
File Æ Save As…
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Workstation set-up
PCC_PrLe (type in the new name) Æ OK
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Workstation set-up
(Now we have a new project with the hardware configuration and the Symbol Table but with a new name)
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Definition of process variables
3.
Normalisation and definition of the process variables factors
All analog voltage signals are working in the range of 0 – 10 V without focussing on the real process value like mm of water for the level control, or l/min for the flow or mbar for the pressure or °C for the temperature. By loading the analog input signals inside the CPU, the relation of the voltage and the decimal value of the peripheral input word (PIW xxx) inside the CPU is as follows.
By means of, if the analog signal at the level sensor for example is 5 V, the value inside the CPU is 13824. The following screen shot shows that example. Remark: All of the following screen shots have been done using a CPU 313C and a standard Control panel. If you use another PLC specification, the handling is the same!!
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Definition of process variables
Example: The value of the flow sensor (AI_Flow) with 5 V signal at the sensor
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Definition of process variables
Example: The value of the flow sensor (AI_Flow) with 10 V signal at the sensor
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Definition of process variables
Of course it is quite difficult to work with the PIW analog input values inside the CPU, it would be much better, if we could normalise them to the real process value: • l/min flow control To do so, we have to calculate the relation between the analog voltage signals and the real process variable like:
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Definition of process variables
Example pressure sensor: W activated the pump digitally and checked the value of the analog input (pressure sensor). We found the following relation: Pressure sensor: AI PIW
Process variable [mbar]
0
0
19658
275
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Definition of process variables
So if you will see a value of the pressure sensor (AI_Pres) in Step 7 of for example 15872
means:
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Definition of process variables
3.1
Adjustment of the ultrasonic sensor
The ultrasonic sensor has to be adjusted to show the value of the level of the water in the tank. If the tank is empty, the ultrasonic sensor must give an analog signal of 0 V. Based on the below formula, we have to edit a program within the CPU which enables us to calculate the real process variable in mm height. This program will be written in the OB1 (Organisation Block 1) and is based on the relation below. Level sensor: AI PIW
Process variable [l]
0
0
27648
10
Please follow the screen shots step by step to edit, download and test the program. The value of the the level sensor comes as a Word in Integer. To be able to calculate with Real numbers, we have to transfer the Word into an Integer Double Word first, before we transfer that value to Real numbers.
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Definition of process variables
+S7-Program(1) Æ Blocks Æ OB1 (double click)
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Definition of process variables
(Choose STL in the field of Created in Language) Æ OK
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Definition of process variables
(Edit the program like shown within the screen shot) The real or Floating point numbers like 300 or 27648 can be edited simply by type 300.0 and 27648.0 and the numbers will change to Floating points automatically.
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Definition of process variables
File Æ Save
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Definition of process variables
PLC Æ Download Æ (follow the commands on the screen)
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Definition of process variables
Now please fill 4.5 liter of water into the tank 102
and watch online how the value of the level sensor changes. Remark: The photo shows the old tank designation of mm instead of liter!!! Remark: Because based on the tank construction, the value of the ultrasonic sensor and the liter of water in the tank is not 1:1, we have to fill only 4.5 liter into the tank = 5 V at the sensor.
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Definition of process variables
Debug Æ Monitor (to activate the online function)
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Definition of process variables
STANDARD (right mouse button) Æ Representation Æ Floating Point (to see the Real numbers)
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Definition of process variables
Now adjust the ultrasonic sensor by opening the screws and move the sensor up or down until you can see the value which is shown in the screen shot, by means of 5 liter of water. After the sensor is adjusted, please close the screws again.
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Definition of process variables
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Definition of process variables
3.2
Definition of the normalisation factor
To be able to see the real process variable later on within the online mode of the continuous control, we have to define a so called factor which is based on %, because the analog input variable of the Function Block which is used to control the process continuously is based on %.
3.2.1
Normalisation factor level control
Level sensor:
Level control
AI PIW [%]
AI PIW
Process variable [mm]
0
0
0
100
27648
10
Umax Process
Xmax Process
PIW max
Factor f
10,00 V
10 l
27648
0,1
Flow control with pump Pressure control Temperature control
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Definition of process variables
3.2.2
Normalisation factor flow control
For the flow control, we have to find out first, what is the maximum flow the pump can achive. To do so we are going to activate the pump digitally and pump water from tank 101 to tank 102 for exact 1 minute and then we switch off the pump. After switching off the pump, we have to measure the difference in water height reached in 1 minute. Please open the manual valve 101 to proceed. To activate the pump digitally, we we are going to use the project PCF_PrFl. Please follow the instructions on the screen shots below to do so step by step.
+PCC_PrFl Æ +SIMATIC 300(1) Æ +CPU 313C Æ +S7 Program(1) Æ Blocks
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Definition of process variables
(Double click on OB1 and change the language to FBD) Æ (Change the comment of the Network 1 like shown within the screen shot) Æ (click under the network to activate the programming frame)
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Definition of process variables
View Æ FBD (check if the programming language is FBD)
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Definition of process variables
View Æ Overviews (activates the catalog of available Function Block Modules if it is not active already)
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Definition of process variables
We are goint to edit a small program to activate the pump digitally by pressing the START button. As long as we press the START button, the pump shall be activated digitally. According to the list of in- and outputs, we have to activate the output of the pump by pressing the START button. This function “as long as” is called Assignment. Please follow the screen shots step by step to edit this project.
+Bit logic Æ Assign (double click or move the module into the frame by keeping the left mouse button pressed)
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Definition of process variables
(Click on the input) Æ (right mouse button) Æ Insert Symbol (to insert a symbol which we defined at the very beginning during the hardware configuration)
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Definition of process variables
START (double click. If you use the CPU 315F-2 PN/DP version with a Touch panel, the real hardware addresses will vary, but the symbols are all the – here Start)
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Definition of process variables
(Click on the output) Æ (right mouse button) Æ Insert Symbol Æ PumpDig (double click. If you use the CPU 315F-2 PN/DP version with a Touch panel, the real hardware addresses will vary, but the symbols are all the same – herePumpDig)
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Definition of process variables
Insert Æ Network
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Definition of process variables
(Edit the program like shown within the screen shot)
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Definition of process variables
File Æ Save
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Definition of process variables
PLC Æ Download (to download the program into the CPU. Follow the instructions on the screen to proceed until the download is complete)
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Definition of process variables
Debug Æ Monitor (to activate the online function)
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Definition of process variables
(If you press the START button you will here the pump is working and water is flowing from tank 201 to tank 102 of the Level control station. You also can see the function of that program online inside the CPU). It might happen, that the tank 102 is totally empty, so please fill the tank first with exactly 5 liter of water by pressing the START button. If you reach 5 liter of water, release the START button. Now we have a defined starting point of 5 liter water in tank 102. Now press and hold the START button again for exactly 1 minute. After exactly 1 minute, please reflease the START button and check the height of the water in the tank 102 of the Level control station.
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Definition of process variables
In our experiment, we found out, that the height of the water reaches the level of 9.95 liter, by means of 9.95 l – 5 l (starting point) = 4.95 l Xmax Process = 4.95 l / min The next is, to find out the maximum value of flow sensor AI_Flow if the pump is working digitally. To do so, we have to add another network to our program. Please follow the screen shots to do so:
Debug Æ Monitor (to deactivate the online function)
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Definition of process variables
Insert Æ Network (to insert a new network)
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Definition of process variables
(Define the network comment like shown within the screen shot)
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Definition of process variables
(Click under the Network to activate the programming frame) Æ -Bit logic (to close the menu of the Bit logic modules) + Move Æ Move (double click)
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Definition of process variables
IN (Click on IN) Æ (right mouse button) Æ Insert symbol Æ AI_Flow (double click to choose the flow sensor)
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Definition of process variables
(Negate the EN = enable input, because we want to permanently load the Flow sensor value to the Memory Double Word MD20)
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Definition of process variables
OUT (Click on OUT) Æ (type in the hardware address of the Memory Double Word we want to use – here MD20) Æ ENTER
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Definition of process variables
File Æ Save
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Definition of process variables
PLC Æ Download (follow the instructions on the screen until the download is finished)
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Definition of process variables
Debug ÆMonitor (to activate the online function)
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Definition of process variables
MD20 (right mouse button) Æ Representation Æ Decimal (to see the decimal value of the Flow sensor in MD20)
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Definition of process variables
(By pressing and holding of the START button you can see that the pump is working digitally and you can see the maximum value of AI_Flow which is 17750 in our experiment. After finish, please deactivate the monitor mode) Æ Debug Æ Monitor Æ File Æ Exit
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Definition of process variables
Flow sensor:
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Definition of process variables
Flow sensor: AI PIW [%]
AI PIW
Process variable [l/min]
0
0
0
64.2
17750
4.95
64.2 % of maximum flow rate equals a maximum voltage of the process of: 17750 / 27648 * 10 V = 6.42 V Umax Process
Xmax Process
PIW max
Factor f
Level control
10,00 V
10 l
27648
0,1
Flow control with pump
6,42 V
4,95 l/min
17750
0,077
Pressure control Temperature control
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Definition of process variables
3.2.3
Normalisation factor pressure control
For the pressure control, we have to find out first, what is the maximum pressure the pump can achive. To do so we are going to activate the pump digitally and pump water from tank 101 to tank 101. Please open the manual valves 103 and 108 to proceed. To activate the pump digitally, we have to save the project PCC_PrFl as a new project named PCC_PrPr. After saving is finished, please open OB1 of PCC_PrPr.
(Change the network comment and change the Network 2 like shown within the screen shot)
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Definition of process variables
File Æ Save
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Definition of process variables
PLC Æ Download (to download the program into the CPU)
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Definition of process variables
Debug Æ Monitor (to activate the online function)
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Definition of process variables
MD30 (right mouse button) Æ Representation Æ Decimal
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Definition of process variables
(By pressing and holding of the START button you can see that the pump is working digitally and you can see the maximum value of the pressure is approx. 275 mbar in our experiment)
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Definition of process variables
(By pressing and holding of the START button you can see that the pump is working digitally and you can see the maximum value of PIW 756 which is 19658 in our experiment. After finish, please deactivate the monitor mode) Æ Debug Æ Monitor Æ File Æ Exit
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Definition of process variables
Pressure sensor:
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Definition of process variables
Pressure sensor: AI PIW [%]
AI PIW
Process variable [mbar]
0
0
0
71,1
19658
275
71,1 % of maximum flow rate equals a maximum voltage of the process of: 19658 / 27648 * 10 V = 7,11 V Umax Process
Xmax Process
PIW max
Factor f
Level control
10,00 V
10 l
27648
0,1
Flow control with pump
6,42 V
4,95 l/min
17750
0,077
Pressure control
7,11 V
275 mbar
19658
3,87
Temperature control
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Definition of process variables
3.2.4
Normalisation of the temperature factor
The easiest way to define the factor is the temperature process, because we are using a PT 100 sensor, normalized to 0 – 10 V which means 0 – 100 ° C. The calculation of the factor is according to the definition, that the temperature inside the tank should not be higher than 40 °C:
40 °C = 4 V = 40% = 4 V / 10 V * 27648 = 11059 Temperatur sensor: AI PIW [%]
AI PIW
Process variable [°C]
0
0
0
40
11059
40
Umax Process
Xmax Process
PIW max
Factor f
Level control
10,00 V
10 l
27648
0,1
Flow control with pump
6,42 V
4,95 l/min
17750
0,077
Pressure control
7,11 V
275 mbar
19658
3,87
4V
40 °C
11059
1
Temperature control
* The temperature inside the tank should not exceed 40 ° C which means 4,0 V or PIW of 11059. The values above can vary from workstation to workstation a little bit.
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2-Step Control
4.
Level control by a 2-step controller
The 2-step controller represents the easiest way to control a process variable simply by digitally switching on the manipulated value when a minimum level is reached and switching it off when a maximum level is reached. For this exercise, we are going to activate the pump digitally and open the manual valve 101 totally and the valve 112 by 2/3 to realise a disturbance value. Please save the existing project PCC_PrPr as a new project named PCC_Pr2S: The definition of the exercise shall be: • Activate the pump by switching the Auto/Manu switch on • Switching off the digitally pump at a level of 5,2 liter • Switching on the digitally pump at a level of 4,8 liter mm
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2-Step Control
We want to use the real process values of liter, so that we have to normalise the level sensor input signal like we did it in the first project. So we are going to open the first project PCC_PrLe and copy the OB1 to the new project PCC_Pr2S. Please follow the screen shots how to proceed:
File Æ Open
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2-Step Control
PCC_PrLe (choose the first project) Æ OK
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2-Step Control
(Move the windows like shown within the screen shot. Choose Blocks of PCC_PrLe) Æ (click onto OB1 of PCC_PrLe) Æ (right mouse button) Æ Copy
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2-Step Control
(Choose Blocks of PCC_Pr2S) Æ (right mouse button) Æ Paste
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2-Step Control
(After the copy procedure is finished, close the window of PCC_PrLe) Æ X
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2-Step Control
OB1 (double click on OB1 of PCL_Pr2S) Æ View Æ FBD (change the programming language to Function Block Diagram – FBD)
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2-Step Control
Insert Æ Network
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2-Step Control
(Edit the first comparator to switch on the pump digitally if the Auto/Manu switch is on and the level of water is less than 4,8 liter)
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2-Step Control
(Edit the second comparator to switch off the pump digitally if the level of water is higher than 5,2 liter. We want to switch off the pump in any case, even the Auto/Manu switch is off – safety. After finish the editing) Æ File Æ Save Æ PLC Æ Download
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2-Step Control
(After downloading the program, open the online function) Æ Debug Æ Monitor
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2-Step Control
(Change the representation to Floating point)
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2-Step Control
What you can see is the situation that the level in the tank 102 is approx. 4,65 liter of water and that’s why the pump switches on if the Auto/Man switch is on as well.
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2-Step Control
Now the level of the water in the tank reaches 5,22 liter the pump will be switched off. The pump can also be switched off by switch off the Auto/Man switch – safety!!! (After finishing the test, please close the monitor mode and close the programming window) Æ Debug Æ Monitor Æ File Æ Exit
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Continuous Control
5.
Continuous control
In the following project we are going to reaIise a continuous flow control by using different controller types.
Normal so called open loop programs will be edited within Functions (FCx) numbered with 1, 2, 3, 4, a.s.o. These programs will be called (started) from the Organisation Block 1 on specific conditions. The cycle time max. is 150 ms, the real cycle time depends on the length of the single program. The OB1 starts automatically after switching the CPU to RUN, all FC´s have to be called up from OB1. In the closed loop control (continuous control) it is different as you can see within the graphics. OB35 as well as OB1 start automatically after switching the CPU to RUN.
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Continuous control
So in most cases, a continuous control solution is a combination of both – OB1 and FC´s for the digital periphery like sensors, control panel functions (START, RESET etc.) and OB35 with FB41, DB41 for the continuous control of the closed loop process.
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Continuous control
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Continuous control
5.1
Continuous pressure control
Please proceed to prepare the continuous pressure control by switching the manual valves to the correct position and save the existing project PCC_Pr2S as a new project PCC_PrCP. As we found out in the project before, the data of the different process variables are: Umax Process
Xmax Process
PIW max
Factor f
Level control
10,00 V
300 mm
27648
30
Flow control with pump
6,42 V
4,95 l/min
17750
0,077
Pressure control
7,11 V
275 mbar
19658
3,87
4V
40 °C
11059
1
Temperature control
The following project solution (Proj_05) is defined by: • • • • • • •
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The Auto/Manu switch pre-selects the pump analog By pressing the START button, we will pre-select 200 mbar to MD30 By pressing the RESET button, we will pre-select 250 mbar to MD30 Each pre-selection will be indicated by the corresponding light inside the button All the above mentioned functions have to be programmed in FC3 FC3 shall be called without any condition (uncondition call) For the continuous control, we are going to try different controller types
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Continuous control
(Open Blocks at the new project PCC_PrCP) Æ Insert Æ S7-Block Æ Function
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Continuous control
FC3 (change the name of the Function) Æ (make sure the programming language is FBD) Æ OK
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Continuous control
Blocks Æ Insert Æ Organisation Block
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Continuous control
OB35 (change the name of the Organisation Block) Æ (make sure the programming language is FBD) Æ OK
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Continuous control
OB1 (double click) Æ Edit Æ Select All
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Continuous control
Edit Æ Delete
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Continuous control
Insert Æ Network
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Continuous control
(Type in the network comment and edit the uncondition call like shown within the screen shot. After finish the editing) Æ File Æ Save Æ File Æ Exit
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Continuous control
1. Screen shot Network 1 - 3
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Continuous control
2. Screen shot Network 4 - 5
FC3 (double click) Æ (edit the program like shown within the screen shot. After finish the editing) Æ File Æ Save Æ File Æ Exit
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Continuous control
OB35 (double click) Æ (edit the network comment) ÆFB41 CONT_C_ICONT (double click)
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Continuous control
(Define the corresponding DB, which is free defineable – here we use DB41) Æ ENTER Æ Yes
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Continuous control
(Edit the corresponding in-and outputs of the FB41 as shown within the screen shot. After finish editing) Æ File Æ Save Æ File Æ Exit
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Continuous control
(Activate the PID Control parametising) Æ Start Æ Simatic Æ Step 7 Æ PID Control parametising
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Continuous control
(Maximize the window) Æ File Æ Open
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Continuous control
(Choose the correct project – PCC_PrCPby pressing on Browse and move to Blocks and make sure, that Offline is activated) Æ DB41 Æ OK
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Continuous control
(Edit DB41 like shown within the screen shot. The factor of 3.87 we defined during the project 3. After finish the editing) Æ File Æ Save Æ File Æ Exit
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Continuous control
(Download the entire Blocks to the PLC) Æ Blocks Æ PLC Æ Download (follow the instructions on the screen to complete the entire download)
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Continuous control
All
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Continuous control
Yes
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Continuous control
Yes
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Continuous control
OK
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© Festo Didactic GmbH & Co. • MPS PA – PLC control
Continuous control
Yes
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Continuous control
(Activate the PID Control parametising again) Æ Start Æ Simatic Æ Step 7 Æ PID Control parametising
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Continuous control
File Æ Open Æ (choose the project PCC_PrCP by pressing the Browse button and switch to Blocks) Æ Blocks Æ DB41 Æ Online (to activate the online function) Æ OK
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Continuous control
(Change the Manipulated Variable to Automatic Operation) Æ (Activate the curve recorder) Æ Debug Æ Curve Recorder
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Continuous control
(Move the window of the Curve Recorder like shown within the screen shot) Æ Settings
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Continuous control
(Change the settings like shown within the screen shot. Because we calculated the factor for pressure control by 3.87, we can change the setpoint and process variable to mbar, by means of from 0 – 300 mbar. The pump is still working in %, by means of from 0 – 100 %) Æ OK
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Continuous control
Before we start the control process, please switch on the Auto/Manu switch to activate the pump analog and by pressing the START button and the Start at the Curve recorder the process starts.
Start
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Continuous control
Now you can optimize the controller by changing the parameters for Proportional Gain and/or Reset Time
Stop (stop the curve recorder)Æ(change the parameters – here Proportional Gain = 4 and Reset Time = 4 s) Æ PLC Æ Download Æ Start (re-start the curve recorder) Æ (you can also change the setpoint during the process simply by pressing the RESET button and back to the START button on the signal unit to see how the controller reacts on changing setpoints) Æ (after finishing the optimization, please close the window) Æ File Æ Exit Æ OK (to save the changes) All other continuous controls are quite similar.
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