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Author Topic: CSMIO/IP-S Closed Loop?  (Read 6146 times)

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Offline cv580

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CSMIO/IP-S Closed Loop?
« on: June 15, 2013, 12:26:40 AM »
Will the CSMIO/IP-S operate in closed loop mode? The CS website sort of leads one on to think it is a closed loop control, but I do not see how it can be by looking the user manual, I don't see any connection for encoder feedback on the control in the user manual.

Offline Hood

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Re: CSMIO/IP-S Closed Loop?
« Reply #1 on: June 15, 2013, 02:53:18 AM »
At this time a machine using the IP-S will only be closed loop if using step/dir command servo drives and  the loop will be closed between the servo drives and the motors but not the IP-S/Mach.
 If wanting closed loop to the control you would need analogue command servo drives and you would use the CSMIO/IP-A.

Hood

Offline cv580

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Re: CSMIO/IP-S Closed Loop?
« Reply #2 on: June 15, 2013, 11:05:13 AM »
Thanks Hood,
Starting to make some sense now, I see in the user manual for the CSMIO/IP-A there are connectors for encoder input.
Please bear with me for the dumb questions I am about to ask, I am new to the servo world, I have always worked with steppers up till now.

Do you have any suggestions where to look for analog command servo drives? In all the searches I have done all that come up are step and direction command drives.

Is a CW and CCW command drive the same as a -10v/+10V command drive?
I see some drives are able to take step/dir input or CW/CCW input, but the data on these drives is not clear on the input voltage.

Offline Hood

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Re: CSMIO/IP-S Closed Loop?
« Reply #3 on: June 15, 2013, 03:49:20 PM »
No, CW/CCW is different, it is more like Step/Dir in that it is a series of pulses however the pulses are on both channels and go one way for fwd and the other for reverse.

Most of the usual servo drives you see mentioned when talking about Mach are Step/Dir, that is because until recently that was all you could use.
 Nearly all AC Servo drives can be used with analogue command and often also Step/Dir. If wanting DC servo drives then you have to look at people like AMC or similar, ie the more Industrial rated end of the market.

Hood

Offline mmoe

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Re: CSMIO/IP-S Closed Loop?
« Reply #4 on: June 17, 2013, 03:43:36 AM »
It depends on application, which you haven't specified really. Is this a smaller hobby machine or a larger commercial machine? If the latter, there is no way around the fact that the drives and motors are going to cost a lot unless you find a deal on some used equipment. If it's hobby, then they are available but still a bit of a premium. However, if you are buying an IP-A, then you probably aren't an average hobbyist in that case anyways. I can't speak to how good they are, etc. but here's a servo drive that works with DC servos and operates on analog inputs. It also provides encoder feedback to the controller via the DB-9 connector, so both the drive and the controller/Mach are getting encoder information. This is a smaller drive, but if you don't need a lot of power then I believe they would work with the IP-A and don't cost quite a fortune at around $500/ea (though if you are comparing to Geckos or other drives along those lines, it does seem like a lot more).  

http://www.applied-motion.com/products/servo-drives/sv7-q-af

From what I've read in the manuals, the "AF" version is the one with encoder feedback specifically for analog applications, though others also work on analog signals without the more convenient encoder integration. I suppose that one advantage of these drives is the motors would be relatively inexpensive as well, but I suspect that you'd be in for around $2200-2500 for a complete 3 axis system including power supply, servo drives, servo motors and encoders. I also found at least a half a dozen other vendors of similar drives, though these were some of the better priced models and are sold/backed through a U.S. based company (though made in China by the looks of the markings). There are cheaper from likely less reliable distributors, and also more expensive. I just googled "DC Servo Drive Analog Inputs" and found the best way to find what is available to look at the "Images" results in google instead of the web results.

A couple other results (again, mostly hobby sized since there is no problem finding expensive commercial products with analog inputs):

http://www.motioncontrolproducts.com/drives/DSD806-digital-servo-drive.php
http://www.zappautomation.co.uk/en/jd-range/518-jd430-aa-000-ac-servo-driver.html  (this one is getting to the more commercial/industrial side)
http://www.midwestmotion.com/amplifiers.htm

Offline cv580

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Re: CSMIO/IP-S Closed Loop?
« Reply #5 on: June 17, 2013, 10:14:41 PM »
Thanks mmoe for the info and links which I have found very helpful.

The application that I am working with is a deep hole drill with rotary axis that use for cut rifling. The linear stroke is 35 inches and the rotary is anywhere between 1500 to 1800 degrees of rotation per 35 in stroke depending on rate of twist I require. I have been trying to work with a stepper setup but it is very slow, have to keep the speed down due to mach starts to miss step after about 12 plus hrs of non stop operation. I have witnessed the same type of machine as mine running with servos that can do the same job in about 4hrs. It also has miss stepping issues if the speed is increased (he is running with Gecko's), this is the reason I have started looking at a closed loop control with more of a industrial type of servo motors and drives. I have been told that a commercial rifling machine can do this job in about 30 to 45 min, I would be very content to do it in a couple of hrs!

Offline RICH

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Re: CSMIO/IP-S Closed Loop?
« Reply #6 on: June 17, 2013, 10:28:58 PM »
CV580,
I know this is off topic, but you haven't lived until you have hand drilled and rifled a 50 cal 48" long barrel.
BTW, it was the best shooting muzzle loader my friend ever had!  ::)

RICH

Offline mmoe

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Re: CSMIO/IP-S Closed Loop?
« Reply #7 on: June 18, 2013, 01:00:36 AM »
Thanks mmoe for the info and links which I have found very helpful.

The application that I am working with is a deep hole drill with rotary axis that use for cut rifling. The linear stroke is 35 inches and the rotary is anywhere between 1500 to 1800 degrees of rotation per 35 in stroke depending on rate of twist I require. I have been trying to work with a stepper setup but it is very slow, have to keep the speed down due to mach starts to miss step after about 12 plus hrs of non stop operation. I have witnessed the same type of machine as mine running with servos that can do the same job in about 4hrs. It also has miss stepping issues if the speed is increased (he is running with Gecko's), this is the reason I have started looking at a closed loop control with more of a industrial type of servo motors and drives. I have been told that a commercial rifling machine can do this job in about 30 to 45 min, I would be very content to do it in a couple of hrs!
Sounds like a closed loop is ideal. I've never had a machine without closed loop, so I'm curious how you know it misses a step and what the problems created by that are? I imagine one step should be negligible, but is it that it misses a whole pile of steps all at once or do they miss one here and there which add up to large errors? How do steps get lost in the process? Is it from interference or miscalculations?

Offline cv580

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Re: CSMIO/IP-S Closed Loop?
« Reply #8 on: June 18, 2013, 04:25:33 AM »
I am not 100% sure when the miss stepping occurs, but the final results are a lands that are too  narrow and basically canted at the top from the cutter being out of sync somewhere in the process of multiple passes. I have the code setup so that when it has finished cutting all the grooves the rotary axis should be at zero on the machine dial and in the dro in mach.
When I have everything slowed down the lands in the barrel are perfect and the machine has returned to zero on both axis and in mach, when I try to increase the velocity of both axis I end up with skinny canted lands and the machine has not returned to zero when the job is finished but the dros in mach are indicating zero at this point. So somewhere there has been small accumulated miss stepping at higher speed, my thought is with a closed loop control the miss stepping should be picked up and the machine would stop before creating another piece of scrap.