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position control with CPU 313C

Created by: siuton at: 12/29/2014 7:28 PM (9 Replies)

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12/29/2014 7:28 PM	Rate (0)
siuton Posts: 4 Rating: (0)	Hi all, My CPU 313C has 3 technological function channels (CH0-2), and i've used all the channels for PWM mode with SFB49 very ok. As i know, we can only use 1 mode as the same time (counting, frequency measuring or PWM), and we have to config the channels in Hardware in Simatic. Now, my question is could we know how many pulses that were generated in 1 channel while using PWM mode without mechanical feed back (encoder or something like that). For example: - CH0: PWM - SFB 49 config PWM - Buffer or resiter that save the number of pulses that were generated. I'm using this manual: "S7-300 Automation System CPU 31xC Technological Functions" Thanks for help. Ton
siuton Posts: 4 Rating: (0)
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12/31/2014 9:41 AM	Rate (0)
IBN-Service Posts: 8946 Rating: (999)	Please try to explain more clear...
IBN-Service Posts: 8946 Rating: (999)
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1/1/2015 6:53 AM	Rate (0)
siuton Posts: 4 Rating: (0)	I am controling 3 step motors with PWM 50%. And I wanna count the pulses that were generated, but my CPU 313C just has 3 channels to count or PWM. Could you tell me the way to read it? Or the other way to control the position with step motor? I have no more experience with it. Thanks for your support.
siuton Posts: 4 Rating: (0)
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1/1/2015 12:04 PM	Rate (0)
IBN-Service Posts: 8946 Rating: (999)	siuton I am controling 3 step motors with PWM 50%. And I wanna count the pulses that were generated, but my CPU 313C just has 3 channels to count or PWM. Could you tell me the way to read it? Or the other way to control the position with step motor? I have no more experience with it. Thanks for your support. Oh, OK. Usually you will NOT count the pulses of stepmotor but you will calculate the amount of steps that you need and give out this amount of pulses! Or you need an encoder feedback. Also, my opinion is that it is NOT possible to energize a Stepmotor by PWM! You must adjust Speed with frequency but not with pulsewidth. So you need PTO not PWM, if I am not wrong...
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1/2/2015 5:21 AM	Rate (0)
siuton Posts: 4 Rating: (0)	Yeah. you are right. We control step by frequency, not with PWM. But CPU 313C doesn't have PTO moduleitself, I think PWM 50% is the same as PTO in S7-200, and we can control the period by using module SFB49. I just mean that I'll use the function block to generate pulses, but not by timer (on delay or sth like that) As you said, I got that we must calculate the amount of steps first to give out the amount of pulses.And when we have this amount of pulses, usually, we compare it with the recently number of pulses that were generated to disable the pulses. But, if I use the function block, I can not get that recently number of pulses. I do not know the way to get it, or we do not have like using embedded kit. Thanks for reminding me feedback with encoder. If have no choice, it will be the good way.
siuton Posts: 4 Rating: (0)
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1/3/2015 9:54 AM	Rate (1)
IBN-Service Posts: 8946 Rating: (999)	siuton Yeah. you are right. We control step by frequency, not with PWM. But CPU 313C doesn't have PTO moduleitself, I think PWM 50% is the same as PTO in S7-200, and we can control the period by using module SFB49. I just mean that I'll use the function block to generate pulses, but not by timer (on delay or sth like that) .... Ah, I see.... Your problem is, that you have no more technological function (like fast Counter) at CPU313C to count the Impulses of 3 axis. Possible solutions: a.) Usestep-motor module like 6ES7138-4DC01-0AB0 (ET200S) 6ES7353-1AH01-0AE0 6ES7357-4AH01-0AE0 b.) Use additional Counter modules like FM350 or FM351 You must consider the voltage (5V or 24V) that you need. c.) Try to generate the pulses with time Interrupt OB (OB35). Than you can use your tec. channels 0..2 for counting, But the problem here is, that it will beimpossible to generate frequency higher 500 Hz with OB35. d.) If needed accuracy is not very high, you can try to generate the amount of pulses by starting the PWM. Example: you need 1580 steps. You start PWM with 1000 Hz for 1.580 Sec. using the SFB4 for example. But this solution will by fuzzy and resulting in a chain error, so you will need a permanent reference setting.
IBN-Service Posts: 8946 Rating: (999)
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1/4/2015 2:45 PM	Rate (0)
siuton Posts: 4 Rating: (0)	Great! Thank you so much Mr. IBN. My problem seems to be easy from here. I've tried you D-solution, It's not exactly, but can calib to adapt with the length of my code. Of course, it's just for testing or small project. In the real, I think I will use a function module to control. Thanks again for your advice and help.
siuton Posts: 4 Rating: (0)
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1/4/2015 4:19 PM	Rate (0)
IBN-Service Posts: 8946 Rating: (999)	siuton ...Thanks again for your advice and help. You are welcome, dear friend.
IBN-Service Posts: 8946 Rating: (999)
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This contribution was helpful to 1 thankful Users siuton

1/27/2015 9:35 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published byjavad.automation is split to a separate thread with the subject control servo motor position with SFB44. Best regards Min_Moderator

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3/24/2017 2:49 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by Deep5310 is split to a separate thread with the subject CPU 314C 2PN/DP, stepper motor positioning control. Best regards Min_Moderator

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