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IndustryArena Forum > CNC Electronics > UHU Servo Controllers > The UHU parts list, questions and improvement.
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  1. #21
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    Re: The UHU parts list, questions and improvement.

    Hi,

    I sent a PM to Rasta, I will look into my old backups for the information required to make the board and email it to him. I don't have a website to post it anymore. If there is more interest I can upload it to Mega.

    Regards,

    kreutz

  2. #22
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    Re: UHU Parts

    Here are the latest Schematics including modifications

    Attachment 483080

  3. #23
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    Re: The UHU parts list, questions and improvement.

    Here is the compressed Gerber folder. The HP-UHU pcb is marked Rev 1.0b, it requires modifications as per posted in the HP UHU thread.

  4. #24
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    Re: The UHU parts list, questions and improvement.

    Hello

    Make sure to review the LATEST parts list and be sure you can get all the components listed, before ordering pcbs from your fab. I don't work with Altium software anymore and it will be time consuming doing further modifications to this design.

    Regards

    kreutz

  5. #25
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    Re: The UHU parts list, questions and improvement.

    Out of curiosity what are you using now for schematic and PCB layout
    Cheers
    John

  6. #26
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    Re: The UHU parts list, questions and improvement.

    The company, I was lately part time designing for, use Cadence Orcad. My own PC has crashed so many times without backups that I don't own a copy of either of them (Altium or Orcad), for personal use, anymore.

    Regards,

    kreutz

  7. #27
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    Re: The UHU parts list, questions and improvement.

    Up until mid June my Windows Home Server was reliably backing up WIN-XP, WIN-7, VISTA and WIN-10. Now it still does those but something in one of the microsoft databases for WIN-7 has been corrupted and I've not been able to fix that. And there's been too much new development not saved in that system.

    It's a pity that WHS was dropped. If the hard drive on the your system failed it was a simple matter to install a new one, insert a CD and boot from it. Tell it to find the WHS and then select which system you want to restore. After X hours you'd be at the last back up point including all secret license codes unique to that machine. Something much harder to do with simple file backups.

    At this point I don't know what to do with the WIN-7 system. Once option is to get a new hard drive, restore it from the point before it became cranky. Then pull in copies of any of the important data files. Of which there are a number of Protel-99SE and Altium.

  8. #28
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    Re: The UHU parts list, questions and improvement.

    I lost track of how many crashes I had when using win 7, actually not always the O.S. fault, the hard drives failed or got corrupted suddenly. I was confident on using a NAS as a backup for the files and the whole disks but the NAS also suddenly lost 2 drives and everything went out the drain. Then I've upgraded to to Win 10,, since I lost the licenses for many old applications during the crashes, and they recently went for the "pay annually" theme, I decided to stop personal development at home. The only info I successfully rescued was the old designs from the early 2000's which I backed up using USB drives.
    I don't trust the cloud for backup because my internet connection is really slow over a DSL line, I live in the countryside and there is no interest from my provider to upgrade the lines.

  9. #29
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    Re: The UHU parts list, questions and improvement.

    I've had better success with keeping licenses. In fact although I have Altium I still maintain a number of projects in 99SE. The last version I paid for was Altium 18. Runs on both WIN-7 (my main workstation) and the new laptop (WIN-10). I've had to drop RAD Studio (Delphi and C++) because the latest upgrade came right after Microsoft stopped support for WIN-7 and Delphi refused to run on WIN-7 at that point.
    Too bad I never got a Protel version of the HP_UHU project. Just the PDFs. Would then be possible to replace the processor with the layout for Henrik Olsson's dsPIC version.

    At the moment I'm working with a PIC32MX1024MCM064 for my Electronic Lead Screw project. It's really a motor controller processor with QEI and PWM plus A/D for motor control but I'm just creating step/dir signals. There's no point in competing with China at this point in time.

  10. #30
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    Re: The UHU parts list, questions and improvement.

    John;
    If I ever find the Altium schematics and pcb files for the HP UHU project I will contact you in order to send them via email. Also the compiled libraries for the project (if I'm lucky enough). Don't count on them yet...

  11. #31
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    Re: The UHU parts list, questions and improvement.

    Quick question about the current limit settings. Looking at the schematic of 1.0c or d there's a VREF and a VREF_OC. VREF is a lower voltage than VREF_OC but it's the input into the slow_limit RC network.

    So how exactly does this work. If the motor is normally a 2.8A motor with a rated torque of 1.27 N.M. but a peak torque rating of 3.9 N.M. so I'd guess a peak amp rating is scaled the same to 8.6A.

    The question then is what to set the reference pot to. The combined sense resistors with 0.01 Ohm will have 28mV across them (I * R) for 2.8A and 86mV for that peak current.

    So what value is VREF at the "TP Current Limit" set to?

  12. #32
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    Re: The UHU parts list, questions and improvement.

    I think you better increase the value of the sense resistors in order to improve the S/N ratio at the comparator, let's say you replace the two parallel current sense resistors by 0.2 ohm 5 Watts non-inductive resistors. Then the current limit Vref should be adjusted to 0.280 Volts and the OC_Vref to about 0.80 Volts in order to make use of the intermittent maximum torque capability of your motor. The resistors will get hot when in the intermittent torque zone but will lower the temperature during normal torque usage, make sure you separate the resistor body from the pcb surface to allow for airflow and avoid toasting the pcb.

  13. #33
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    Re: The UHU parts list, questions and improvement.

    Thanks. I used the numbers I had off the top of my head for my Bergerda AC Servos. Actually the original motors I was using were:
    Skewed Rotor Design:
    Constant Torque: 1.6 N-m ( 226 oz-in)
    Peak Torque: 8.0 N-m ( 1125 oz-in)
    Max Speed at Voltage Constant: 3200 RPM
    Terminal Voltage: 90V
    Constant Current: 7.8A
    Peak Current: 40A
    torque Constant (KT): 0.182 NM/am
    Voltage Constant (KE) 18.95 V/rpm
    Resistance: 0.925 ohm
    Inductance: 2.5 mh
    Inertia: 3.4 kg/cm^2

    But at the moment I want to play with a 24V motor that is marked with these spec's.
    I sub n = 2.7A
    I sub fm = 24A.

    So say I change the two current sense resistors to 0.4 ohms to get a parallel value of 0.2 Ohms x 2.7A = 0.54V.
    Attachment 483724

    The Rev 1.0d drawing has two trim pots as shown above. My boards have only one. I should probably modify the boards for two or set up a different divider for the VREF while the VREF_OC is adjusted with the pot.

    I think the references are not named to guide their purpose. The fast limit is designed to shut down drive when current exceeds VREF_OC which is the higher current setting. VREF_LOCKED_ROTOR is perhaps a better name?

    The VREF signal controls the slow limit which requires the current to be there for some time before it trips and shuts down drive to the motor or restarts it. Perhaps VREF_MOTOR_MAX.

    With those names it's obvious we'd want VREF_MOTOR_MAX to trip on 2.7A and VREF_LOCKED_ROTOR to be 24A or some value between 2.7A and 24A to prevent burning up the motor.

    Have I got that right?

  14. #34
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    Re: The UHU parts list, questions and improvement.

    In the HP_UHU Vref (slow limit) is the trigger point to integrate the current vs time the motor stays above Vref, VRef is equal to the Continuous Current limit of the motor times Rs (Ic*Rs). The motor is allowed to go over this continuous limit for some time, that is, to operate in the intermittent zone, factory limited (generally) by the temperature rise in the motor.
    Vref_OC sets the Maximum Current limit for your motor (Fast Limit) because it will damage your motor to exceed this current.

    If you replace the resistors by 0.4 ohm ones, they must be rated 10 Watts each, or they won't last. It all depended on how much time your equipment stays over the continuous torque limit of the motor and how frequently it does it. If you notice they get too hot, use some speed reduction mechanism after the motor in order to multiply the torque so to avoid overloading it.

  15. #35
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    Re: The UHU parts list, questions and improvement.

    Thanks Hugo,
    I have a project in mind for one of my UHU or HP_UHU boards. Hence some of the questions.
    I use both R8 and an R8-TT collet on my mill. So most of the tools are in TT holders that slip into the 0.75" flatted face R8 collet.
    To drop a tool requires maybe 1 to at most 2 turns of the drawbar.
    To remove the R8 TT collet and say insert my R8 Face Mill requires about 12 turns of the drawbar which I don't want to do each time I remove a TT holder.

    Specified torque for R8 tooling is about 20 ft-lbs although it's unlikely I have ever tightened them that much by hand. But I did build a butterfly impact wrench system along with a socket revolution counter to try and automate things.
    Attachment 483730
    It sort of works but not well. There are two issues.
    1. The socket doesn't always end up lined up with the head and can even jam on crooked so I added a sensor for all the way down.
    2. If the drawbar is not very tight and a short blip of the air to the butterfly wrench sends it spinning and once loose can literally over spin and drop the R8 collet.

    Essentially the problem with the butterfly impact wrench is unloaded is way too fast to be able to properly control.

    I'm using a controller I scavenged from a different project.
    Attachment 483732

    Clearly the butterfly wrench isn't suitable for automated behavior. So I want to drive the drawbar socket with a motor and reduction that at highest power will create 25 ft-lb torque. But I never want to tighten it with more than say 18 ft-lb of torque.

    What I thought I'd try is turn a DC servo for 12 turns or until motion stops and say a 2.0A current limit is reached or a timeout. That's to tighten.

    To loosen if it's a TT Holder the button to release is just tapped and the motor torque is increased to 2.7A and turned for 2 revolutions. (actually way more depending on reduction gear).

    To loosen and remove the R8 collet or tool, the button is held for more than 1/2 second and again torque is increased to 2.7A but now 16 revolutions or as long as the button is held or a timeout.

    So I thought I'd use a UHU and make it possible to adjust the reference so it always has reserve torque to loosen but can never tighten more than a preset value. Once the motor stops the continued steps into the UHU will create a following error. That's the indication that the drawbar is tight. A signal from the controller will toggle the reset line on the UHU to undo the fault.

    So either a relay that switches in a parallel resistor into the reference setting or even a PWM generated filtered voltage to serve as the reference.

    So that's the background. Where I'm undecided is which Vref to 'tweak'.

  16. #36
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    Re: The UHU parts list, questions and improvement.

    You don't need the reserve intermittent zone torque, so only the fast acting Vref_OC is enough. You can adjust both potentiometers to the same value in doubt.

    What about using the reduction gearbox of a battery hand-drill which have some selectable "limit torque" positions? Those are pure mechanical, kind of slip clutch. Or limit the air pressure value so not to exceed a certain torque on your pneumatic impact wrench? Look also at the mechanism of the automobile starter motor for inspiration, it engages and disengages on power up/down automatically.

  17. #37
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    Re: The UHU parts list, questions and improvement.

    I tried the 3/8" electric ratchet. Perfect for torque. But needs mechanical adjustment to change direction. The mechanism internally appears to be more like an impact wrench with a rotating hammer hitting a disk to ratchet the drive.

    I'm not sure the battery drills have the torque capability. Starts to get a bit jury rigged.

    This is what I had in mind for the reduction drive and the 8mm input fits the motor I have.y
    https://www.aliexpress.com/item/1005002841759258.html

    Then a modified UHU drive with a D/A for the reference. Then I can change the torque.

    Without writing new firmware send the motor in the tighten direction for say 20 turns of the planetary output. At some point the motor will stall due to torque being reached. The extra step pulses will cause a fault which I can sense. Now I know the drawbar is tight. Lift it up and run the mill.

    To remove the TT Holder update the D/A to the higher torque setting, reset the UHU, send it in the release direction for two turns of the planetary output. The higher torque should make that easy.

    To remove the R8 same process but now N turns or while release button is pressed but no more than T seconds.

    That's currently how the butterfly works. There's a magnet on the socket holder and a hall sensor on the frame. So I count butterfly wrench turns. But once it's loose if I am late on stopping it the butterfly runs up to 10,000 RPM unloaded and out drops the TT holder and the R8 collet.
    I've thought about just putting some sort of brake on the impact wrench to prevent the high RPM. But I've also found I've over tightened it so much that the air pressure is too low to undo it.

    It's usable but sometimes a pain.

  18. #38
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    Re: The UHU parts list, questions and improvement.

    Your idea make sense, let me think a little more about it. Maybe we are overcomplicating the solution. Or there is a simpler solution somewhere that does not require to turn a nut on the drawbar end for engaging/releasing,

    Edited: Please, look at: https://www.youtube.com/watch?time_c...ature=emb_logo
    and https://hackaday.com/2020/01/11/stac...ll-conversion/

    and also: https://www.youtube.com/watch?v=gkE0vk_oDAU

  19. #39
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    Re: The UHU parts list, questions and improvement.

    I like how he addressed the issue of pressure on the spindle bearings.
    Also the mill shaper behavior for cutting the splines in the disk.
    I didn't see how he replaced his TT Holder R8 collet with an R8 Face mill or a 3/4" chuck. TT Holders aren't strong enough for that size chuck.
    And there's the problem. If all you have is a hammer then everything looks like a nail.
    I want the ability to swap an R8 for a TT holder just as easily as TT to TT or R8 to R8.

    If you look at the R8 changers with Butterfly wrenches in most cases the human operator brings the wrench down until it engages the nut. If the socket doesn't line up he can just blip the air to spin the wrench and then as it slows lower it onto the drawbar. Then pull the handle left or right for tighten or loosen. Since it's R8 he holds it until either the collet/tool drops out or until it's tight.

    But when the computer does it there needs to be a tighter loop and one pulse per rev on a impact wrench that runs up to 10,000 RPM unloaded isn't adequate.

    Not to mention I keep dropping the socket... But that's another problem...

  20. #40
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    Re: The UHU parts list, questions and improvement.

    I've been here before so to speak. What you see in this photo is a servo motor controller by CAN messages into a 100:1 reduction drive which goes into another reduction drive. The square aluminum bar represents a mast that is raised and lowered. The module at the end of the mast is an inclinometer, also reporting via CAN messages.
    Attachment 483972
    The motor is controlled via Torque and Velocity mode. As it approaches an angular set point it switches over to torque mode to nest smoothly against an end stop. It also moves off the stop with torque mode in case the locks are in place. Then at full speed until the next angular set point and then back to torque mode.
    I 3D printed the motor and reduction drive holder.
    Attachment 483974
    I've attached the pdf of the motor. It's 5000 RPM, up to 5 NM and 1.6kW all at 24V. Way too big for what I need but then what it actually lifts is way heavier and it does it very quickly. Would have been nice to score the test system for myself but I no longer work for that company and they are still using it for firmware changes.

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