Smart Steppers - Page 1
Forum section: electronics / projects

author: trampas
author_rank: Regular Contributor
timestamp: August 07, 2017, 06:44:23 pm
content: I have been working on making stepper motors smart. That is adding a rotary encoder and then setting up the stepper motor as a closed loop servo. The design is such that you can retro fit your existing stepper motors and upgrade your machine.Many people are using the NEMA 17 units to fix their 3D printers from missing steps on long prints. Others are using the NEMA 23 on CNC projects and industrial applications.The way the system works is a magnet is glued (epoxy) to the back of the stepper motor shaft, then the PCB is bolted to the back of the stepper motor which senses the rotation angle of the magnet. The Smart Stepper PCB has a motor driver, and a 48Mhz 32bit processor allowing full closed loop control. Once the PCB is attached you disconnect motor from machine and run through a calibration process. Then you interface the Smart Stepper to your existing controller using the step and direction pins (if you use step stick you can remove them from your controller). At this point you select what microstepping you want and you are off and running. The motor should run quieter and will faster (if you increase speed on controller).The software allows you to select multiple modes of operation, from a simple PID mode which works for most people out of the box, or a positional PID which requires more tuning but gives better performance. For other applications you can select velocity operational modes too. Of course the software is all open source and you can change it as you like.I have setup a website where you can get your smart stepper kit to upgrade your stepper motors here:http://misfittech.net/smart-steppers/ThanksTrampas

author: thm_w
author_rank: Super Contributor
timestamp: August 09, 2017, 12:15:25 am
content: Its a great project, being able to see and adjust settings on the unit is so much better than traditional method (hooking up a PC, recompiling, etc.).I started on re-laying out the board, mostly for my own preferences (jst connectors, less wiring, etc.):https://github.com/thmjpr/nano_stepperWill definitely donate once I get it working.

author: trampas
author_rank: Regular Contributor
timestamp: August 09, 2017, 12:18:38 pm
content: Great it good to hear that others like the project, keep me updated on your progress.On my list is to find a accurate optical encoder to connect to steppers and measure the magnetic encoder's performance. If anyone has a suggestion for an encoder with around 0.01 degree or better accuracy/precision, please let me know.ThanksTrampaswww.misfittech.net

author: mikerj
author_rank: Super Contributor
timestamp: August 09, 2017, 12:43:27 pm
content: Quote from: trampas on August 09, 2017, 12:18:38 pmhttp://www.renishaw.com/en/resolute-absolute-encoder-system-with-rexa-rotary-angle-ring--10852I suspect you might need deep pockets!http://www.gurley.com/Encoders/rotinc.htmThey list encoders that provide up to 250k quadrature cycles per rev.

author: trampas
author_rank: Regular Contributor
timestamp: August 09, 2017, 02:52:00 pm
content: thm_w,I have newer design of the board, which has not been pushed to github yet. The new design has a buck regulator on board such that the board can be powered from the motor voltage.Trampaswww.misfittech.net

author: trampas
author_rank: Regular Contributor
timestamp: August 09, 2017, 02:54:28 pm
content: I had found this encoder:https://www.digikey.com/product-detail/en/broadcom-limited/AS38-H39E-B13S/516-3356-ND/6150753It has 39 bits, but the accuracy is specified at +/- 80 arc/seconds (+/- 0.022 degrees). I would like something a little better.Trampaswww.misfittech.net

author: thm_w
author_rank: Super Contributor
timestamp: August 09, 2017, 08:21:54 pm
content: Quote from: mikerj on August 09, 2017, 12:43:27 pmLooking at R112 (http://www.gpi-encoders.com/PDF/R112.pdf), +/-5 arcmin = 0.08 degrees. Then they have quadrature and interpolation error on top of that.R158 (http://www.gpi-encoders.com/R158.pdf) is 30 arc seconds so that would do it (0.008 degrees).I would be scared to ask the cost though.Oddly BEI sensors encoders don't list any accuracy specifications at all, I wonder if the interpolated resolution is useful or just a marketing number.

author: trampas
author_rank: Regular Contributor
timestamp: August 09, 2017, 10:31:24 pm
content: If it this hard to find and encoder that is better than +/- 0.022, it might be the type of thing where if the Smart Steppers meet this spec it would be exceptional for the price point.Trampaswww.misfittech.net

author: H.O
author_rank: Frequent Contributor
timestamp: August 10, 2017, 06:47:52 am
content: USDigitalEM2is available with up to 10000CPR. The "readhead" costs $40 and the disc another $30, not too bad I don't think.

author: trampas
author_rank: Regular Contributor
timestamp: August 10, 2017, 10:56:56 am
content: The Smart Steppers include a AS5047D magnetic encoder. The magnet is glued to back of motor and the AS5047D senses the rotation of the magnet with 14 bits. Since the magnet is not perfectly placed on axis the firmware calibrates the encoder by using 200 full steps of the stepper motor and assuming that each step is 1.8 degrees. Between steps the firmware linearly interpolates the finer angle resolution. see here for installation instructions:http://misfittech.net/blog/installing-the-nano-zero-stepper/Typically in feedback mode the system can maintain the same position using this setup to better than +/-0.05 degrees, I usually recommend people planning on 0.1 degree repeatablity. If you tune PID you can often get better results. The boards current work great and are $49.95 for each board including the magnetic encoder. So yes for 4 units it would be $200 to retro fit your existing steppers to become closed loop servos, so it is not for everyone. However if you have lost days of a print and created spaghetti mess a few times or if use your printer for production it might be worth it. However the applications as not limited to printers.Additionally for most people the missed step on printers is usually only the X and Y axis (depending on printer design) so many only put on X/Y motors. Also most people tune down the speed of their printers to try and keep from missing steps, so after installing the smart steppers you can often turn up the speed of printing.Here is an example of use:https://www.nanodlp.com/forum/viewtopic.php?id=441The question on the optical encoder, is that I would like to make the product better, that is currently the assumption in calibration is that each full step is 1.8 degrees. If I can get a good optical encoder then I could at production time connect a stepper motor to the optical encoder calibrate the magnetic encoder more accurately. This of course would mean selling the controller mounted to a stepper motor. So the optical encoder is not for each unit sold, but rather for production use, so price is less of a concern.Trampaswww.misfittech.net

author: alexo
author_rank: Contributor
timestamp: August 10, 2017, 10:34:45 pm
content: The cheapest option for an accurate encoder is to purchase a small Mitsubishi servo motor off eBay. Some come with a 1 million line encoder. Cheap as chips compared with buying the encoder by itself and already nicely mounted in a precision enclosure. Works a charm.

author: thm_w
author_rank: Super Contributor
timestamp: August 11, 2017, 01:07:33 am
content: Quote from: alexo on August 10, 2017, 10:34:45 pmGood idea.I see some HC-KFS which are 17-bit (131,072 pulses per rev) for $80:http://www.ebay.ca/itm/Used-1Pcs-Mitsubishi-Plc-Servo-Motor-Hc-Kfs13b-Plc-Module-K-/262953091749http://164.54.212.3/control_systems_manuals/SH_NA_3181-F.pdfHF-KP053 or HF-MP053 is 18-bit, for $1-200:http://www.ebay.ca/itm/MITSUBISHI-HF-MP053-50W-0-05kW-HFMP053-AC-MOTOR-/292064638198HG-KR053/HG-MR053 is 22-bit (4mil pulse per rev!) for only $2-300.

author: H.O
author_rank: Frequent Contributor
timestamp: August 11, 2017, 09:03:53 am
content: That IS a good idea if you know how to read the data out (it's usually not your normal A/B quadrature signals but some serial protocol like SSI or ENDAT).Also, I'm fairly certain the native resolution of the encoder is much less than for example 22bits and that it does interpolation between actual lines on the disc so you can't neccessarily rely on each "count" being 360/4M (or whatever).Still a very good idea!

author: donotdespisethesnake
author_rank: Super Contributor
timestamp: August 11, 2017, 11:06:57 am
content: Seems like there were no cheap closed loop steppers then several arrive at once... I am wondering how this product differs tohttp://tropical-labs.com/index.php/mechaduinoorhttp://www.ustepper.com/index/?I'm not sure adding $100 to a cheap 3d printer is very cost effective, but I have a skipping Y axis so I want to try a closed loop stepper.

author: senso
author_rank: Frequent Contributor
timestamp: August 11, 2017, 01:28:46 pm
content: I know that steppers have some strong magnetic fields, but could you try a Magnetic encoder from AMS, they use radial magnets, and with some calibration you might get some 10-11 bits out of the 12 bits units, they have a couple compensation registers, you might be able to use them if the axle is not flush with the stepper case.

author: trampas
author_rank: Regular Contributor
timestamp: August 11, 2017, 03:04:36 pm
content: The Smart Steppers use the AMS AS5047D with 14bit resolution.The Smart Steppers and Mechaduino are very similar in design with a few exceptions:Smart Stepper exposes an error pinSmart Steppers includes a buck converter to power board off the motor voltageSmart Steppers have an LCD option, such that they can be configured without use of PCSmart Steppers do not require recompiling source code to calibrate motors or change parameters.Smart Steppers firmware has a lot more features an options.Smart Steppers hardware has diodes and TVS for ESD issues.Smart Steppers come with screw cage connectors for easier connection to machine.Smart Steppers parameters are easy to change through USB serial port using a command line interface.The ustepper does not control the current to motor like the Smart Steppers and Mechaduino. The ustepper basically uses a step stick to step forward or back to correct errors. The Smart Steppers and Mechaduino will change the current to the motor based on the error, this reduces noise and heat on motor.With the Smart Stepper when you connect to machine and try to move the head out of position the current control on the motor makes it feel like strong springs are attached to the head pulling it back into position. Since you have control over the current you can change the "stiffness" of these virtual springs.I have ported my firmware to the Mechaduino in case people want to upgrade their Mechaduino.Trampaswww.misfittech.net

author: alexo
author_rank: Contributor
timestamp: August 11, 2017, 09:03:51 pm
content: Quote from: H.O on August 11, 2017, 09:03:53 amData out for that particular series is A/B, no interpolation for 1 mill counts. The 400W pops up on eBay from time to time pretty cheap. There is an excellent magnetic alternative from Renishaw but then mounting becomes if not a chore at least a "project".

author: raptor1956
author_rank: Frequent Contributor
timestamp: August 12, 2017, 03:17:33 am
content: Quote from: alexo on August 10, 2017, 10:34:45 pmYeah, for the most part stepper are open loop units and if you're going to need closed loop servo's are a better choice for a number of reasons. Servos do not need the holding torque as they have the encoder to know if it moved -- a stepper needs to have a fairly high holding torque so it knows it hasn't moved else it loses counts. Holding torque requires more power and produces more heat. Servo's are much smoother and quieter as well.For position critical applications you might have two encoders: one on the motor to close the velocity loop and one on the load to close the position loop.Brian

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 12, 2017, 11:12:25 am
content: You can easily put a flywheel on the stepper and give it a wank.Not good for absolute position measurements, but you can use it for lineairity measurments and such.Have you considered potentiometers?These have "infinite" resolution.https://www.aliexpress.com/wholesale?SearchText=conductive+plastic+potentiometer

author: alexo
author_rank: Contributor
timestamp: August 12, 2017, 01:23:12 pm
content: Actually not. The resolution of pots is pretty poor.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 12, 2017, 01:33:47 pm
content: not the pot, the adc... 1024 steps per revolution only (maximum with hard work tuning), and its slow. plus contact mechanism wears out..

author: alexo
author_rank: Contributor
timestamp: August 12, 2017, 01:44:05 pm
content: Quote from: raptor1956 on August 12, 2017, 03:17:33 amStepper systems are superior to servos but for the case of highly variable heavy loads.

author: alexo
author_rank: Contributor
timestamp: August 12, 2017, 01:45:40 pm
content: Quote from: Mechatrommer on August 12, 2017, 01:33:47 pmCould you please re-phrase ? I do not understand.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 12, 2017, 03:29:32 pm
content: Quote from: alexo on August 12, 2017, 01:45:40 pmlets try again, non-native to non-native... potentiometer has infinite (analog) resolution, but the problem with the method is how to detect the resolution when converted to digital ie using adc of the mcu, most jelly bean mcu has 10 bits of resolution, that is 1024 steps maximum for one revolution, and adc conversion is alot slower than digital input quadrature state pooling/interrupt detection, can be problematic in high speed rev application. and in high durable (expensive) application, the brushed potentiometer will wear out in time, so brushless or contact-less system is more favourable, hope it helps... what i havent mentioned is the potentiometer need to be circularly contiguous because the motor in infinitely rotating, the adc/mcu/system wont like a discontinuous resistance at both the extreme end of the potentiometer... its ok for limited angle servos, but not in this case... fwiw...

author: raptor1956
author_rank: Frequent Contributor
timestamp: August 12, 2017, 07:11:51 pm
content: Quote from: alexo on August 12, 2017, 01:44:05 pmYeah, no..Show me any commercial robot that uses steppers versus AC or DC servos. Steppers require more power on average and produce more heat and are noisier. It what ways do you view steppers as superior?Brian

author: alexo
author_rank: Contributor
timestamp: August 12, 2017, 07:54:46 pm
content: Quote from: raptor1956 on August 12, 2017, 07:11:51 pmWell, there are MANY. Too many to bother mentioning.Now, factor into your post my "but for the case of highly variable heavy loads".

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 13, 2017, 01:58:30 am
content: with closed loop, holding torque current for stepper motor can be released, only engaged when motor position is changed, just like normal servo/dc motor. the superiority of stepper is it can be used as position control in open loop, given miss step can be prohibited... long story short... it can be googled...

author: raptor1956
author_rank: Frequent Contributor
timestamp: August 13, 2017, 04:00:29 am
content: Quote from: alexo on August 12, 2017, 07:54:46 pmI posted a number of factors favoring servos so perhaps you could be so kind as to offer a few examples where steppers are superior? Yes, if positioning is not as critical steppers are the way to go and I've designed a number of systems using steppers so I'm not biased against them. If the op is looking to add an encoder it would suggest to me a concern that a stepper alone might lose position. Again, in a positioning critical application servos smoke steppers!I await your list is reasons why steppers are superior...Brian

author: alexo
author_rank: Contributor
timestamp: August 13, 2017, 09:07:41 am
content: Quote from: trampas on August 07, 2017, 06:44:23 pmHave you looked at things like these :http://www.ebay.com/itm/Hybrid-NEMA23-Integrate-Closed-Loop-Stepper-Motor-Drive-2NM-Position-Encoder-36V-/121792648966?hash=item1c5b685706:g:aEoAAOSwqVBZYfN~http://www.ebay.com/itm/NEMA23-3N-m-3phase-easy-servo-Closed-loop-stepper-motor-drive-kit-CNC-DC20-50V-/172690310642?epid=905996634&hash=item28352505f2:g:HAAAAOSwGJlZI9rxThey work very well.

author: CM800
author_rank: Frequent Contributor
timestamp: August 13, 2017, 11:03:23 am
content: Quote from: raptor1956 on August 13, 2017, 04:00:29 amI'll offer a bit of insight. I work as an engineer for a motion control distributor, selling, amongst other things, steppers and servos.Steppers offer the advantage of being lower cost. They also have a higher torque-to-size ratio. If you need low speed, high torque, the cost saving is significant, considering a harmonic drive or planetary gearbox can cost several £££ for a decent quality one.Naturally, steppers do have their downsides. They have huge issues with resonance. They are far from the most efficient motors and can often have bad documentation for speed / torque curve.however, as said, they are -very- low cost compared to a good servo system. e.g.Motor:- 440mNm- NEMA 17- £22Quality Drive:- DMD556- DSP anti-resonance auto-tuning- 256 Microstepping- £115Vs:Servo motor:- £55-150Drive:- £200-400Gearbox:- 50-200As you can see, the stepper will come out reasonably cheaper, expecially in volume.Steppers are also plug and play, Servos can need some fine tuning.I personally favour brushless servos where possible, They are noiseless, much smoother motion and you can get incredible accuracy.I'm playing around with the concept of building myself a brushless linear motor X-Y-Z gantry for machining. I have my eyes on some nice linear motors and micron encoders sitting in a corner of the warehouse...

author: alexo
author_rank: Contributor
timestamp: August 13, 2017, 06:55:53 pm
content: I'm not familiar with servos similar to a NEMA17. My usual suspectsare between 1 and 4 Kw. Steppers when well matched to the application have very predictable performance, eliminate the need for gearboxes which are high wear items and with proper construction ( Kolmorgen ) and high performances drives are smoother than most servos. Expensive servo systems running pulse and direction will better steppers when used in the right applications. If you get going with your linear servos project I hope you'll keep us informed. I tried those a couple of times and I was never happy. Too much trouble for little performance gain.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 13, 2017, 07:32:00 pm
content: i wonder if any dc/ac motor servo is capable of this speed and accuracy of stepper servo...

author: CM800
author_rank: Frequent Contributor
timestamp: August 13, 2017, 07:55:38 pm
content: Quote from: Mechatrommer on August 13, 2017, 07:32:00 pmI'm sorry, I had to take a 5 minute break from reading that just to laugh.How exposed have you been to modern day motion control?Here is a good application:Die inspection machine in the semiconductor industry.They had an encoder tracking at max 6,500,000 counts per second. Throughout all movements, it was within +/- 1 count.High-end servo drives, such as ones from Elmo Motion Control you get PI current loop tuning with auto-tuning to kick you off.You can tune position and veloicty with a sine-sweep through the entire operating bandwidth, then tune it live realtime, it even gives you a nichols plot to work with.Check out this:https://www.slideshare.net/elmomc2012/elmomc-servo-drive-for-top-performanceNow, mind telling me how a stepper system compares?

author: alexo
author_rank: Contributor
timestamp: August 13, 2017, 08:25:12 pm
content: Quote from: CM800 on August 13, 2017, 07:55:38 pmNever exemplify with an exception.How many industrial milling machines / lathes have you retrofitted ?

author: CM800
author_rank: Frequent Contributor
timestamp: August 13, 2017, 08:48:02 pm
content: Quote from: alexo on August 13, 2017, 08:25:12 pmNot sure what you are talking about there.I responded to this:QuoteTo which I can definitely reply that Brushless AC Servos (Linear or Rotary) are superior in both speed and accuracy to stepper servos.Cost and size benefit is something entirely different, it depends on the machine.I also guarantee with the correct servo drive and brushless motor you can beat the performance of any stepper servo solution.However I don't dispute that there can be gains in cost and size with stepper solutions. Though there are big drawbacks with resonant spots.

author: alexo
author_rank: Contributor
timestamp: August 13, 2017, 09:13:03 pm
content: Quote from: CM800 on August 13, 2017, 08:48:02 pmYou gave an example which involved a resolution of 4.8nm. That's not relevant. It's also pretty irrelevant to compare high performance servos like say, the Mitsubishi/Omron I commonly use with low cost steppers, the kind eBay is packed with. High performance steppers and drives have very low cogging, almost no resonance issues and have built in holding torque. Next time you retrofit a boring mill you'll see how handy holding torque is and how irritating is to convince a servo system to pretend to have it. In my experience servos cost 2-3 times more in parts only. The dynamic improvement is rarely taken advantage of. I better spend the money on decent ballscrews - those are making a big and very real difference.

author: CM800
author_rank: Frequent Contributor
timestamp: August 13, 2017, 09:58:04 pm
content: Quote from: alexo on August 13, 2017, 09:13:03 pmYou bring up some good points however you can't seem to take note of WHAT I was responding to, even when I pointed it out once.I was responding specifically to Speed and Accuracy as related to someone else's post.You will find some servo drives much better then others. Yes, they are expensive, but with a good understanding of how to set them up, you can get incredible performance.Don't forget that holding torque only guarantees within a step.A high resolution encoder on a brushless motor allows it to provide less error with holding torque then a stepper motor.Elmo drives for example allow gain scheduling for In motion, steady-state and stepping, to allow you to refine motion characteristics.While I can't argue on cost. I can grantee a better performance using servo motors and drives. (Even better, linear servos)There is a good reason why virtually all high end machines use brushless rather then stepper.You can argue cost all day, but brushless servos simply cannot be beaten in performance.And FYI, Omeron and Mitsubishi barely hold a candle to Elmo in performance. It blows my mind just what their drives can achieve.You'll find them used in many high end pick and place machines for example.check out some of the stuff they can do with gantry https://www.youtube.com/watch?v=Kjl0iyUCeJ8Also, they arn't even that much more expensive then competitor drives.

author: alexo
author_rank: Contributor
timestamp: August 14, 2017, 03:00:09 am
content: All I can say is that you shouldn't rush to guarantee anything. When it comes to machine tools, retrofits in particular, a single scraped part as a result of improper servo algorithm can ( and often ) costs more than the entire motion system. For 30 years I keep seeing manufacturers advertising and pushing the latest, only to see them a couple of years down the line reverting to the old and trusted. A quick visit to practicalmachinist.com will inform you as to the amount of trouble people have with servos. They're great for certain applications and a pain in others. I know nothing about Elmo and their products. The YT video is cute CGI but there is absolutely nothing new there. Stuff Parker had 25 years ago. In particular when it comes to machine tools one quickly discovers how important is to keep away from the latest fad and stick with the old and trusted. And know. I wouldn't touch Elmo products with a barge pole.That's because I can not afford to give them a try and discover they're busy that particular week.Bottom line is this : for "light duty" applications like a 3d printer or the ubiquitous router steppers are 2-3 times cheaper and twice as good. And spending the money on good quality mechanicals for outweighs fancy motors. And another thing : the price of top performance machine tools has become so high that one can sometimes purchase 2-3 lesser units for the price of a single high perf one. Lots of people wised up to this one.Deep down dynamic performance is hard limited by the motors and I don't see anything new here for some ( many ) years by now. Quite the contrary, some of the fancy stuff has been dumbed down or downright disappeared. 20 years ago it seemed that linear motors will eat up anything else. Guess what ?

author: alexo
author_rank: Contributor
timestamp: August 14, 2017, 03:20:05 am
content: Here's an example :http://www.ebay.com/itm/200W-servo-motor-drive-MSMJ022G1V-MADKT1507E-with-3m-cable-0-64Nm-3000rpm-brake-/201336979447?hash=item2ee09e7ff7:g:~aAAAOSweW5VOlwBThis is a fairly good system I used quite a few times. For common applications I can match it's abilities with a stepper for 1/5 of the price. I then use the leftover monies for proper ballscrews and you WILL see the difference in the quality of your circles.There is NO WAY to sort that out just by using servos as we don't know what and how much you are going to cut one day.

author: CM800
author_rank: Frequent Contributor
timestamp: August 14, 2017, 07:26:05 am
content: Linear motors never took off as far as they could as they were too expensive due to production methods. The cost is coming down dramatically these days.They are nearly at the point where cost is equivalent to a well made ballscrew + motor.You spend a lot of time talking about how you have problems with servos, but you keep talking about units that are so terrible I would clean my browser history after looking at.Elmo have been manufacturing for a very long time, They have supplied over 3 million servo drives, a good number of them into military applications (anti-missile targeting systems, etc.)I've seen first hand what you can actually do with a well made drive, and daaamn.Most of the problems people have with servos really are with the cheap, shitty units like those from china or badly developed units from large manufacturers who's development team has been shrivelled up.The cost isn't even that bad, especially for how much of an improvement they make to a system (heck, some of the clever uses of filters can be to help dampen vibration from bad mechanical design)you're looking at around £500-£700 for the drive and £100-£200 for the motor, however that price drops down significantly for volume.If you are scrapping parts with a servo system, that's a cock-up on your side.

author: alexo
author_rank: Contributor
timestamp: August 14, 2017, 09:32:27 pm
content: Well, I'll have to move on as it doesn't seem we have similar requirements from servos or steppers. I'm talking factory floor equipment - 200GPB won't buy me the cables between the motor and the drive. In real life, most equipment can't take advantage of the performance of high end servos for too many reasons to mention here. I've no idea where your experience exactly rests but my some 80 or so retrofits taught me I must be very careful before jumping into the latest fad. And linear motors were WAY cheaper than servo+C3 ball screw 20 years ago. It was the horrible cogging and the holding torque issues which switched me off.Bottom line is that the R&D teams of large machine tool manufacturers are surely cleverer than you and I put together and squared and they still manage to blunder grievously like EIGHTY percent of the time.

author: CM800
author_rank: Frequent Contributor
timestamp: August 14, 2017, 10:01:02 pm
content: Quote from: alexo on August 14, 2017, 09:32:27 pmI'm getting tired of this, but one more reply to your ill-thought out responses.This is far from a 'latest fad' it's tried and tested units, there are over 3 million axis out there using these drives from this manufacturer alone.Cogging is not an issue anymore these days, modern drives have anti-cogging calibration that is impressively functional.I'd strongly suggest you try it before you knock it. Why not contact the Elmo representative in South Africa, they could give you a good rundown of just how much of a benefit these modern servos can add to application.I only speak so highly of Elmo because I haven't seen a damn servo-drive better then what they have shown off.You can't claim experience with apples and the ability to judge them simply because you have tried a lot of pares and oranges.

author: thm_w
author_rank: Super Contributor
timestamp: August 14, 2017, 11:29:09 pm
content: Quote from: donotdespisethesnake on August 11, 2017, 11:06:57 amWhat has been done to try to solve the problem though.Have you tried: checking motor current, swapping motor drives, motor, checking for binding, etc.?You might want to create a thread here or somewhere else to further investigate the issue first. Not that I would discourage getting a smart stepper to play with.

author: alexo
author_rank: Contributor
timestamp: August 15, 2017, 09:49:38 am
content: Quote from: CM800 on August 14, 2017, 10:01:02 pmWell, it's clear to me now that you haven't seen many drives or actually used any. I looked over their site, couldn't find any documentation and even the installation manuals were password protected. There is practically NO technical information available - it's all vague talk about "performance". The general look of the drives / motors and CONNECTORS ( !) indicates a CHEAP product.Take a look at the capabilities of amid rangedrive like Omron/Mits/Panasonic R88D-KT series and then talk.Notice the 2Khz speed response. Looking over their marketing spiel I see absolutely no extra capability from Elmo drives/motors but I see aHUGEamount of stuff they don't do.But in order to make you happy I'll get an Elmo drive and motor and test it against a Panasonic R88 drive and post the results here. That way we'll see what's the apples and what's the pears. Please PM me your contact details - if the Elmo loses, I'll send you the Invoice.

author: rs20
author_rank: Super Contributor
timestamp: August 15, 2017, 10:04:33 am
content: To the OP, just to be aware of some vaguely comparable things already in the market:-Mechaduino-Teknic ClearpathAnd probably many more; above are just listed things that I actually personally have!

author: CM800
author_rank: Frequent Contributor
timestamp: August 15, 2017, 12:42:27 pm
content: Quote from: alexo on August 15, 2017, 09:49:38 amAmusing you say I haven't seen many drives or 'actually used any' considering my actual job is configuring, setting up and testing Servo drives. Selecting, installing and providing technical support for servo drives is there about half my job.Also I'm pretty confused by you saying you see a 'huge' amount of things that the Elmo drives don't do. Mind pointing out some?A lot of the information is locked up with an account as it is propriatory information and they like to have some level of control as to who has access to it.I'm more then happy to share with you some of the specs:QuoteI think that exceeds anything else you can suggest from other products.Far from cheap, I've seen inside these drives, they are damn beautifully made, the power stage is on a custom ceramic substrate for some of the higher power ones.they have developed their own ASIC gate-driver that allows extremely efficient switchingI can't disagree there are some things that sound like 'marketing wank' but I'll be damned it's all true.Check out this drive, 4kW and only 22 grams...http://www.elmomc.com/products/gold-twitter-servo-drive.htmAnd yes, I called bullshit with them when I first saw it, but they actually show it running at full power on their stand at some exhabitions.If you were in the UK, I'd be happy to organize sending you one of the servo drives and a motor to test it with, but South Africa doesn't have the best reptuation. Why not ask the local Elmo Sales office there if they could offer a demo kit to play with or something similar?EDIT:Here, I've uploaded this just for you:It's not continuous, but it's the best demo you can do without a significantly large load, even then, it's quite a nice show considering the inertia of that huge motor and the size of the drive.Another impressive feature I forgot to mention is that you can put drives in parallel for the same motor (you use a special cable between 2 of the output / input ports and use a duel wound motor) that way you can have a seriously small drive form factor. For example, one of the customers uses their HV Drums, 2x 65kW units running a 120kW duel wound motor.

author: alexo
author_rank: Contributor
timestamp: August 15, 2017, 11:36:25 pm
content: Well, now that I find you work for themthings are different. I won't compare with specific products anymore and I was getting ready to do just that. I think you have some idea how much people like me are being pestered by sales people trying to push product. Nothing wrong with that but for the fact they almost never seem to know what the product is used forby me. Most of my interest is 1 to 4Kw metal cutting machine tools. Wood chopping sometimes. That means most of the claimed features of new products are absolutely irrelevant. A CNC machine can work for many hours on an expensive mold and a single error could translate into a large loss. And errors happen all the time because the toolpath software is not foolproof. If you machine a mold for a say a car door then how fast the machine moves while cutting air or between tool changes is irrelevant. Reliability is everything. Dynamic performance is a big issue with lasers where forces and speeds are perfectly well known.Elmo's idea to call their drives "Clarinet" , "Bassoon", Accordion and so on was stupid. My clients tend to fork out money for Yaskawa or Mitsubishi and at a push might be ok with products from a TV making company.Like Panasonic. This is reality. For me is counterproductive to push product from lesser known manufacturers and it'd take me a page to explain why in detail. One example : check how much 2nd hand stuff from Elmo is available "out there". Now compare with Panasonic or Yaskawa. That matters big time for me and many like me.I couldn't discover Elmo's sales office in SA but anyhow, I would definitely not have the time to test their products. Nor would I be prepared to put up with the expense. The couple of figures you kindly supplied and some others I was forwarded by somebody in the US do not warrant the trouble. The fact they do not have product manuals freely available and sufficiently detailed is an alarm signal for me. Seen that before once or twice... It's a very bad policy - I'm not going to "discuss my needs" with their almost incompetent sales rep. It'll be a waste of time and I don't want to have my clients shortcircuited.The 22g and 4Kw drive is an impressive piece of engineering but what would I need it forThe demo you kindly uploaded shows it works somehow. Not knowing what the peak power and duty cycle are there that might as well be a 400W drive. Might be 50W...Powering one motor from two drives is interesting but again, nothing I could use it for. Never had an issue with the available space for a drive. This is a real niche application and given that a specially wound motor is needed I'd be hard pushed to even start imagining where this could be useful. And anything over 10Kw is completely out of my league.

author: CM800
author_rank: Frequent Contributor
timestamp: August 16, 2017, 07:30:34 am
content: Quote from: alexo on August 15, 2017, 11:36:25 pmHaha, no. I don't work for them...Frankly they supply a lot to military applications and don't cater to small volume applications like retrofitting due to support requirements. Don't flatter yourself in thinking I'm some kind of salesman targeting you.I provide technical support and do setup / integration work across 4-5 different servo drive manufacturers.I'm not trying to sell it here, I think you got me wrong. I admit it sounds like I'm pushing the product a bit, but this entire conversation is more about -servo drives- then anything else. I'm only pointing out Elmo as they are damn impressive in performance and reliability.For your information, we do see a lot of business in the twitters. They are used often in drones, robot arms and other compact machines.Again, most of this stuff isn't even targeted at you, because there isn't much business in that area, but it is still useful when other drives simply don't give the performance available.That said, I do agree they should put more of the information out on the public.Drones and electric vehicles are a good example for a specially wound motor and need for extreme compactness. You want as much space as possible for extra batteries and want to drop weight a lot too.If I actually was trying to push this product, I'd be going about it a very different way. Its amusing how hostile you seem to new technology. I take it you still use exclusively analogue scopes and resolvers?

author: Assafl
author_rank: Frequent Contributor
timestamp: August 16, 2017, 10:01:07 am
content: There is an entirely underserved market for people with some experience with motor controllers: car parking systems.In the building next to ours they installed a parking robot. 6 months it stood barren since a turnstile (on the robot) would not stop within the allowed angle. In discussing this with their support team they insisted that cars were "heavy" and therefore the servo was "unable" to position the cars correctly. They insisted the motor/drive pair was good and well specified and configured (yeah right).They ended up welding a spring (and I assume some form of damping) that the turnstile would stop against.Crappy systems.

author: CM800
author_rank: Frequent Contributor
timestamp: August 16, 2017, 10:07:11 am
content: Quote from: Assafl on August 16, 2017, 10:01:07 amThat is rediculous... Someone can't design a system properly...Interestingly enough, that was one of the examples the Elmo Sales guy showed us, they were using 2 65kW servos to run a large motor, it was for going under cars, picking them up and putting them into their parking spots. Battery powered, it goes back to it's place and recharges when finished.

author: alexo
author_rank: Contributor
timestamp: August 16, 2017, 01:22:37 pm
content: Quote from: CM800 on August 16, 2017, 07:30:34 amWell, I'm surely glad you're not working for them. But I won't tell you why.I'm not at all hostile to knew technology BUT if you've been long into this ( since the '80s ... ) you must've seen the deluge of "New Technology" we were inundated with. Where is most of it ? Nowhere. In the early 2000s we saw a lot of new and often very exciting products just to watch them disappearing within a couple of years. Big manufacturer does not like competition. How do you think Fanuc survives ?And then, there is something else : a lot of the new technology did not pan out on the factory floor. Just not enough performance gain for the trouble/cost and VERY often associated with other poorly researched new technologies. On paper, some 5 axes milling machines looked wondrous. In practice however agile their drive systems were the spindles lasting only a couple of hours was a downer. Couple of years ago client of mine bought two laser machines from a very reputable Germanmanufacturer. One had linear motors and was substantially more expensive. Which machine do you think worked flawlessly 24/7 and which one broke down all the time ? Which machine do you think could be repaired with non OEM parts for cheap and for sure ? Specialized application can benefit a lot from the latest. Machining is a different game - down time costs real money. My impression is that a lot of times new technology is purely sales driven - there is no real, quantifiable need but we need our product to seem different in the market.

author: alexo
author_rank: Contributor
timestamp: August 16, 2017, 01:26:28 pm
content: Quote from: Assafl on August 16, 2017, 10:01:07 amYES. Welcome to the game : most time and money are spent fixing the design. Most designs are crap. Look at cars : one would've thought that in 120 years they have it figured out.

author: CM800
author_rank: Frequent Contributor
timestamp: August 16, 2017, 02:29:34 pm
content: Quote from: alexo on August 16, 2017, 01:22:37 pmHaha, yes. It's hard to argue that.The marketing wank is indeed strong these days.How long until we get our first Bluetooth & wifi enabled wireless IoT servodrive?It scares me that some people thing wireless controlled servo drives would be a good idea... Nothing like someone hiding a cigerette packet sized jammer in a warehouse to stop production for a month....That said. I would personally rather like a drive that can be configured via bluetooth from a phone app as an option (switch on side of drive) Though with the advent of fieldbus being so common, it doesn't hold as much appeal these days.One of the big things I like with elmo is that -it just fucking works-I wire the drive up, I connect to it, go through the setup wizard, spend half-hour turning it and you get damn impressive performance for the average application. You don't even need to enter the motor specs, it runs some 'experiments' on the motor to work everything out - which actually works.That said I'm seeing a lot of new companies coming out with these features.Elmo's Gold range is pretty reliable from all I've seen, rarely get any back from the ones I've helped install, and when I do it's almost certainly a user error (Elmo burn the drives in for 24 hours before sending them out, heck, their 'Extreme Environment' range, they do full vibrational testing under full load too.I've done a good bit of work for military applications, one thing they absolutely hate is change. So many still use VME64, Resolvers etc. Yet, I'm seeing a lot of them begin to use Elmo. I think that says something.I really do agree with your point on how many products out there are badly designed these days and 'look the shit' yet turn out so bad. It's a symptom of modern business operation where the management don't care what they ship out, as long as it makes them money. Career CEOs and Managing directors Etc. Ones who just hop between completely different industries with no expertese in the actual product they are in charge of.

author: Assafl
author_rank: Frequent Contributor
timestamp: August 16, 2017, 03:01:27 pm
content: Resolvers? Aka Singer / Kearfott / Selsyn?Are those still around? Talk about infinite resolution.

author: CM800
author_rank: Frequent Contributor
timestamp: August 16, 2017, 03:06:22 pm
content: Quote from: Assafl on August 16, 2017, 03:01:27 pmTo be honest, Resolvers are very common in Military and Nuclear, great way of getting feedback if silicon can't be trusted in the environment (Ionizing radiation)

author: 691175002
author_rank: Regular Contributor
timestamp: August 16, 2017, 03:52:39 pm
content: Every "Closed Loop Stepper" system I have seen is just a rebranding of a brushless servo. Most of them have skewed windings, and more than half actually use three phase brushless motors!They borrow the stepper name purely as a marketing label. A "stepper" system is generally viewed as being easier to use, providing higher torque per dollar, and operating at lower speeds than the average servo. Closed loop "steppers" use high pole count motors and more forgiving control algorithms to achieve those objectives.The defining characteristic of a stepper motor is that position is controlled by energizing the windings in order. If you are commutating with position feedback its a servo. (And if you are going to go through the trouble and cost of commutating with position feedback you might as well use a motor appropriate for the job, which is why "closed loop stepper" never actually use stepper motors.)

author: CM800
author_rank: Frequent Contributor
timestamp: August 16, 2017, 07:52:57 pm
content: Quote from: 691175002 on August 16, 2017, 03:52:39 pmI know a few closed loop steppers that -do- use stepper motors in them, operating with FOC,Schneider Electric's Lexium MDrives are one. Evodrives (lesser known, it's owned by a friend of mine but he has put the company on hold for the moment due to other engagements)I believe there to be a few others too.