4/13/2015 6:52 AM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
Hello,
To describe the differences, data fed into PID rgulator (PV_PER) need to be scaled merely in the function itself.In this case, you rely to internal computation of CONT_C for data conversion. In case that you need more checks on analog input like validity of analog input and react to interrupts (if AI modules is capable), I suggest using PV_IN as real variable .It is result of SCALE function and some condition monitoring for a safe value.Binary signals (for errors)can be used for putting loop in manual or other safe actions needed. I hope this helps, Hamid Hosseini |
4/26/2015 1:56 AM | |
Posts: 16 Rating: (0) |
I need to test my PLC (CPU: 314C-2 PN/DP Simatic S7-300) with my PWM to make sure it actually communicates with it. What is a simple way for me to do that? I was thinking about building 1 network with a CONT_C block, keep it in Manual mode. I've heard in class that if you keep all of the tuning parameters at 0, it's the same as open loop? Thanks again, Adam |
4/26/2015 4:22 AM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
It is possible to call PULSEGEN without PID controller independently. In this case, just call it in a cyclic interrupt and change INV via watch table and check the result by an oscilloscope .Alternative would be using CONT_C-->PULSEGEN and the PID regulator in manual and change the values from a watch-table. |
4/28/2015 11:28 PM | |
Posts: 16 Rating: (0) |
What is a watch table? Thanks |
4/28/2015 11:57 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
Watch-Table is a tool for monitoring and modifying values.The counterpart in STEP 7 would be Variable Table. |
5/1/2015 6:55 AM | |
Posts: 16 Rating: (0) |
I've noticed on the PID_CP (the block we're using for the master controller) has a "Cascade On/Off" type input; I believe it's QCAS. Am I going to need to create a new separate network for turning cascade off while tuning the inner loop, and then turn cascade on when tuning the outer loop? Thanks again,
Adam
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5/1/2015 3:08 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
The reason and exact connections are explained in the attached file.As far as I remember, tuning the secondary regulator is easily possibly but for the primary controller, I think with doubt about it. AttachmentREG_ST.pdf (202 Downloads) |
5/2/2015 5:37 AM | |
Posts: 16 Rating: (0) |
I have another question: Let's say my Tank 1 (closest to the pump) reaches a max level of 12 inches, and my Tank 2 reaches a max of 6 inches. Tank 1 is my inner loop plant and Tank 2 is my outer loop plant. Controlled variable is Tank 2 level. I understand that the primary controller determines the setpoint of the secondary controller. Let's say I enter in a max setpoint for 6 inches in Tank 2. How will the the secondary controller know to put out the max 5-6 V to the PWM for the pump? How will the master controller input a setpoint of 12 inches in Tank 1? How will my cascaded loops know these relationships? Do I need to have a converter / scaler between the output of the primary controller and the input of the secondary controller? Thanks again, Adam |
5/2/2015 10:15 AM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
Hello again, The master controller transfer the "Demand" to reach the set-point in form of LMN and the secondary controller should adjust the command on actuator to supply the demand in master.So, the secondary controller should be fast and please convert all values to percent for a better function. Note:Please, provide a schematic of your overall designed system for checking the feasibility (even in a test environment). Best regards, hdhosseini |
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