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Motor Movement controling

Created by: S R R at: 3/17/2009 12:00 PM (9 Replies)

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3/17/2009 12:00 PM	Rate (0)
S R R Posts: 8 Rating: (2)	Hi everybody, I am new user an d new in LOGO! I found this great forum today!!! I searched in topics but I can't find proper answer for my question. My project: Wehave a roller for rotatinghuge pipe. It has 4 gearmotors. I wanna check the movement ofeach gearbox so ifone of them work wrongly (under normal speed) or stop, then another motors stop too. 1. I use 4 Shaft encoder for each gear box. 2. gear box speed range is : 0.07 - 0.2 rpm 3. Shaft encoder : 5000ppr, 12 VDC , NPN 4. motors : AC motor 1.5 kW, 380V, 50 Hz ActuallyI wanna read the speeds, compare them to specified speedif one of them is reduced then stop all motors.Thespecified speed should be read from AC Drive (and also Idon't know how?). The operator can change speed via AC Drive. I hope you can help me for that two questions. Thank you in advance for your help!
S R R Posts: 8 Rating: (2)
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3/20/2009 6:14 PM	Rate (0)
Tim Jackson Posts: 8 Rating: (0)	I guess I can answer that, I just did something similar. I assume you can get the "desired" speed as an analogue signal, either as a remote pot or computer input to the motor inverter or else as an analogue remote speed-indicator output from the inverter (may need parameters setting to enable it). The trick I found was to use an analogue input to drive a PI controller with only the integral term non-zero, so that it makes a variable-slope ramp generator, then use an analogue comparator to reset it when it reaches the top. Just like a 555 timer really. This gives you a periodic event at a rate proportional to the analogue input value, ie your inverter speed setting. Now decode your encoder phases into a counter, or even just use a raw phase, it's not exactly critical, (but to get a rapid response you might want a full 4-edge directional decoder - edge gates, lots of ANDs and some head scratching) and use the event generated above to capture the output and reset the counter. Set some suitable upper threshold on the counter. Then alarm (ie turn on and latch an output) if the counter hasn't passed the threshold by the time the event comes along. As to how and when to reset the latch, that's your problem, maybe you can detect plant-stop condition on a spare input, or maybe the analogue goes to zero. Tim Jackson
Tim Jackson Posts: 8 Rating: (0)
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4/5/2009 5:35 AM	Rate (0)
S R R Posts: 8 Rating: (2)	Hi Tim, As I am beginner in LOGO!, would you please send a sample program about that ? I think it can useful for me. I remain,
S R R Posts: 8 Rating: (2)
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4/8/2009 7:55 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Hello SRR, Have you seen Tips and Tricks LOGO! Hope this will helps. Best regards

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4/9/2009 6:40 AM	Rate (0)
S R R Posts: 8 Rating: (2)	Thank you UMENCHO. No I didn't see Tips. At first oportunity I study them. Does any type of LOGO! have "hardware high speed counter and timer" ? If not which type of Siemens's PLC does?
S R R Posts: 8 Rating: (2)
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4/15/2009 8:13 AM	Rate (0)
Darren_T3 Posts: 95 Rating: (10)	Hi S R R, I have full confidence that what Tim described will work with a LOGO but for your application have you looked into the SIMATIC S7-200? I certainly don’t want to take away from the power of the LOGO but when I read you wanted to do all of this monitoring and comparing etc especially with analog values, the math and compare functions in the 200 are a little easier to implement. Here is a link for your consideration. https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&objid=24104802&caller=view Cheers, Darren
Darren_T3 Posts: 95 Rating: (10)
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4/15/2009 9:29 PM	Rate (0)
Tim Jackson Posts: 8 Rating: (0)	OK, here's my simple example (as a zipped .lsc Logo file). It's for detecting thread breaks on sewing machines. During normal operation the sensor sends about 20 impulses/sec. The output is wired to the machine stop button. On a break, the impulses stop and (on this model) the input goes solid on. The PI ramp runs up and the comparator turns the output off, stopping the machine. The second input is "machine running", machine stopped resets the output and the PI, allowing the machine to be started again. For use with an encoder put an edge detecting gate on the input: on this particular machine the operator has a switch to overide detector operation by opening the sensor circuit, so I can't do that. This version is set up for a fixed timeout interval (long time so I can test it by hand in simulation): for variable speed you attach an analogue input to the PI setpoint, to vary the ramp rate (speed control), or to the comparator to vary the trip point (time control). Tim Attachment us.ZIP (660 Downloads)
Tim Jackson Posts: 8 Rating: (0)
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4/16/2009 9:59 AM	Rate (0)
S R R Posts: 8 Rating: (2)	Hi Tim, I have studied your program. There is some points that I couldn't understand them. 1. It works but I can't enough sense about the value why do use 400 or 465? How can I set them or KC? 2. I get set point of speed via potentiometer and send it to AC drive anduser can change speed during the machine operation. So in this time (changing speed) Whatis going on? Please check the attach file. 3. I didn't getduty of I2? Attachment underspeed.zip (621 Downloads)
S R R Posts: 8 Rating: (2)
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5/8/2009 11:14 PM	Rate (0)
Tim Jackson Posts: 8 Rating: (0)	I2 is the signal that tells the unit that the machine is running. If the unit trips, this signal going low means the machine has acknowledged its stop command, and so the trip can get reset. The delay prevents nuisance tripping while the machine is accelerating. Without this the unit would keep tripping w2hile the machine was stopped. The setpoint 0f 400 was just an arbitrary figure. It has to be some positive value if I do not use a speed control, as process variable is then always zero. The ramp rate obviously is proportional to the difference between the SP and the PV. The threshold of 465 on the comparator was how I tuned it to match the speed of the actual machine it was fastened to. It needs to be somewhere in the output range of the PI controller, you can use it as a range adjustment to set the maximum speed (full scale on your pot) to suit your machine, you could even use the "reference" button to connect it to an external adjusting pot. You can also set the range by changing the integrator time constant, but that only goes in steps of 1s. (you've set it to 1hr, that's awful slow, it should ideally be something like the time-out period (between encoder pulses) at full speed. It's neater to use PV rather than SP as your input, then the track shows on the drawing. If you connect your speed pot signal to the PV input, set the SP to zero and the direction to downwards; then the time to reach any specified level would be inversely proportional to the pot setting, so should track the inverter. Try this version in simulation. Set the two inputs to about 500, monitor the graph of the PI, and close I2. It's set up to need you to click I1 every few seconds to prevent tripping. Tim Attachment us2.ZIP (683 Downloads)
Tim Jackson Posts: 8 Rating: (0)
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5/11/2009 10:29 PM	Rate (0)
Betel Platinum Expert Joined: 1/5/2007 Last visit: 4/7/2023 Posts: 1690 Rating: (580)	Hi SRR, please, look at the attachment for my digital solution. The idea is a direct solution and measure the number of pulses per time, make a comparison with the given speed (as analoge input), and as option display the aktual measured speed in rpm. But to do that, it is impossible to use the block (digital) threshold trigger. An own circuit must programed...look my answers at "motor control" and at "Display of scaled High Speed Input Values" for more infos about this.... OK, the attachment contains a minimum version with circuit parameters witch are calculated in relation of your given values at your question. If you need more Infos to this program, then ask me here again.... Best regards Betel Attachment Demo_Threshold_trigger_V3 (as under speed detector).zip (651 Downloads)
	==> Meine TAG-Listen: "deut." ==> "Sammlung von Hinweisen und Schaltungen" ==> "PD-3-Punkt-Schritt-Regelung (z.B. für Mischer)" ==> "Zeiterfassung, ASTRO-Uhr,..." ==> "Meine EXCEL-Tools" + "Tool zur Linearisierung" ==> "Komplexes Rechnen mit der LOGO"
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