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Need Help PTO Connect "PID_compact_1" to "AXIS_1" How?

Created by: laurits at: 4/26/2014 11:45 AM (9 Replies)

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4/26/2014 11:45 AM	Rate (0)
laurits Posts: 10 Rating: (0)	I can not figure out how to connect "PID_Compact_1" and "Axis_1" anyone knows this ?
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4/26/2014 1:00 PM	Rate (0)
William_B Posts: 5225 Rating: (1200)	laurits I can not figure out how to connect "PID_Compact_1" and "Axis_1" anyone knows this ? Hi-ya, Your description does not say much.. what do you want to do? (please select one) a) create a motion control axis b) create a PTO pulse that you use as a reference instead of using an analog c) do PID control using pulse width modulation d) create a PWM signal as reference (see b) e) something else.. (please explain more clearly) I think you a want to drive a stepper motor or servo motor. This falls under (a) or (b) where I personally use the PDF document entitled: "STEP 7 S7-1200 Motion Control V11 SP2" Let us know if this helps OR give more information.
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4/26/2014 2:10 PM	Rate (0)
laurits Posts: 10 Rating: (0)	Hi .. what i would like to do is, Use a PID to control a stepper motor drive .. if is possible at all . I have three outputs on the PID controller .. named "Output" "Output_PER" "Output_PWM" How do i connect the PID controller to my PTO axis ? Thank you Attachment pto.JPG (712 Downloads)
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4/26/2014 2:18 PM	Rate (0)
laurits Posts: 10 Rating: (0)	"Pegaia" is talking about this in this thread /tf/WW/en/Posts/91476 " The main point is: PWM and PTO are different things. PWM is used in the user program like a analog value and a PTO like a axis. You can use both with PID: PID output to PWM address or PID output as velocity referencis for PTO axis. "
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4/26/2014 4:12 PM	Rate (0)
William_B Posts: 5225 Rating: (1200)	laurits "Pegaia" is talking about this in this thread /tf/WW/en/Posts/91476 " The main point is: PWM and PTO are different things. PWM is used in the user program like a analog value and a PTO like a axis. You can use both with PID: PID output to PWM address or PID output as velocity referencis for PTO axis. " Friend, The PID example you speak is for adjusting the width of a pulse that has a preset (fixed) frequency. All the stepper motor amplifiers I know uses a variable frequency pulse to give commands on how to operate. I recommend you have a look at the document link that I gave earlier. Have you ever before used a micro-controller or PLC to drive a stepper motor? You have not.. please tell us, somebody will be more than happy to explain in more detail. I find the position control wizzard for the S7-200 a bit more friendly than the method used by the S7-1200. However.. the motion control available in the S7-1200 has much more abilities. At the very least you should do the following steps.. 1. create the hardware configuration to handle the PTO 2. execute the position control wizzard to set up the axis.. you do not have to use all aspects that is available to you.. but it might make complex movements much easier. 3. Ensure to execute the MC_POWER function to initiate position control. 4. Simple movement can be done using the MC_MoveJog command. Homing, Absolute Movement, Relative Movement and group movement (Table) is possible. I have used motion control on stepper motors and servo motors for complex movements. But if you follow the steps above (1 - 4) it is enough to get you started. Do you need more?.. if you do please tell us what is your experience level using S7-1200 and driving stepper motors. Give us also an idea of what type of stepper drive you are using. I however do strongly recommend you give the document a read of which I gave a link to. Also the system manual for the S7-1200 has a chapter that is of great help. Siemens did a great job with those documents. (I should know.. I taught myself how to use the motion control.) I hope this gives you enough encouragement to stick with it. Greetings. w
William_B Posts: 5225 Rating: (1200)
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4/26/2014 4:54 PM	Rate (0)
laurits Posts: 10 Rating: (0)	Thank you for your reply William I am new to PLCs .. so it's hard for me to explain sorry . and i will take some time to read the PDF file . .. The AXIS and MC_POWER has been setup and it's working, the stepper motor is turning . Also i tested "Command_Table_PTO" and "MC_MoveJog" is working perfectly The only thing i cannot figure out is how to connect the PID to my AXIS Thanks Laurits
laurits Posts: 10 Rating: (0)	Last edited by: laurits at: 4/26/2014 5:01 PM
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4/26/2014 5:13 PM	Rate (0)
William_B Posts: 5225 Rating: (1200)	Glad to hear the motion is working. --- Why do you want to connect the PID to the AXIS? There is no need for it. The standard motion control is an open loop, not closed loop. Do you WANT to create a closed loop? The PID you see in the example is for generating a pulse of which the percentage ON and OFF you can change. This could be used to control how bright a lamp shines, but this has no use for controlling off-the-shelf stepper drivers. So back to my question.. why do you wish to connect PID to the axis? --- We have plenty of students get information from this forum. We welcome them. I do not know if you are a student.. it does not matter.. you can feel free to ask what you need to know. If you however do study some material, the experts will be more willing to volunteer their private time. Feel free to tell us more of what you are trying to do. Work / study / hobby.. it does not matter. Friendly greetings. w
William_B Posts: 5225 Rating: (1200)
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4/26/2014 5:38 PM	Rate (0)
laurits Posts: 10 Rating: (0)	Thank you Here is one example of what i am trying to do . take a look at the first 20sec ...only! https://www.youtube.com/watch?feature=player_detailpage&v=wbsQxwiJC2o here is my setup : I have one distance sensor 0-5v input "IW64" connected to PID analog input. The set point is 3v for example hope this makes sense:)
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4/26/2014 5:55 PM	Rate (0)
laurits Posts: 10 Rating: (0)	BTW . my sensor is mounted on the actuators moving part. in the video it's mounted the actuators stationary part.
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4/26/2014 6:00 PM	Rate (0)
William_B Posts: 5225 Rating: (1200)	laurits I have one distance sensor 0-5v input "IW64" connected to PID analog input. The set point is 3v for example hope this makes sense:) okay.. that help a bit. I am pressed for time for a bit now.. but I am going to give some pointers. I do hope maths does not scare you. 1. IW64 is going to gives you a number. That number represents the distance. You will need to figure out how to convert that number into a distance. It is called "scaling an analog to an engineering unit". 2. You need to figure out how many PLC pulses give how much distance. Note all gear ratios and be careful of the amplifier that gives micro steps. The positioning wizzard needs this info. Set the wizzard so that the PLC knows how to give you distance. 3. Execute HOMING to your axis before starting your motion action. This brings the movement to a known position to start from. 4. To make things more simple (for now) put the sensor in a fixed position. When a movement is triggered, your PLC does the following.. * check your analog for the target's position * use absolute movement to get to your target. * if the sensor detects the target has moved.. execute a revised absolute motion. 5. If you want to mount the sensor on the moving car, you will need to do some maths on the go. You can get the position of the motion and compare that to your sensor. -- Delve a bit into these concepts. -- and know this is not the only solution. Feel free to publish your data (1 & 2) or ask questions. This is a good exercise to do. PID is not essencial. You can do some more simple maths to get it done. Good Luck!
William_B Posts: 5225 Rating: (1200)
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