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| 12/22/2009 5:15 PM | |
Joined: 9/27/2006 Last visit: 9/12/2025 Posts: 12407 Rating:
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Hello Wayne; Ammy's post does tell you how to setup a cascade control using Siemens FB41. However you have to decide whether your application requires cascade control in the first place. Do you have 2 different, coupled variables that need to be controlled at the same time (flow and temperature in a furnace control, level and temperature in a mixing tank application, for example)? Do you have loops that have distinct and very different loop updatetimes (generally one fast, the inner loop, and the other slower, the outer loop)? In the foolowing link you will find a discussion of the merits and the requirements for cascadr PID control: http://www.learncontrol.com/pid/cascade.html You could also have a look at controlguru.com for more discussions on the subject. Hope this helps, Daniel Chartier |
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| 8/22/2010 9:40 AM | |
Joined: 1/28/2009 Last visit: 8/31/2025 Posts: 6874 Rating:
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Hi please check the manual of modular PID control with reference numberA5E00275589-01, section 3.8 example about cascade control. While installingThe package the examples would be available in SIMATIC Manager. Also checkSection 7.4 Control with SIMATIC for more practical details. Check the attachmentFor CFC representation of cascade configuration.Best regardshdhosseini Attachmentcascade.zip (998 Downloads) |
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| 8/23/2010 7:22 PM | |
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Joined: 9/27/2006 Last visit: 9/12/2025 Posts: 12407 Rating:
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Hello Ruku; If the output of the FB 41 is not changing, in the master loop, then it is very probable that it has not been initiated properly. Have a look at jklm's answer in this thread, he offers links to a FAQ and dowloads for FB 41 that you might find useful: /tf/WW/en/Posts/37927 Also, you should make sure that: -FB 41 and instance DBs are downloaded to the CPU -the Parameter COM_RST is set in OB100 and reset after your FB41 call (this will initialize the block calculations); -Call FB41 in a cyclic OB (OB 35 for S7-300 CPUs) and use the cycle time of OB 35 as the parameter value CYCLE in FB41; -Check what value the parameter MAN_ON has been selected: if it is on manual, you will never start calculations in FB 41. -Once started, make sure that you tune the master loop properly before you set the output as SP for the slave loop; only then tune the slave loop. This will simplify your life tremendously. Hope this helps, Daniel Chartier |
| 3/26/2011 2:37 PM | |
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Posts: 2 Rating:
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Thank you for yourpost greatly. |
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