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Thread: Flexicam ATC router retrofit with Kflop/Kanalog

  1. #13
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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    You are having so much trouble because you did not choose appropriate limits for your system. This is most likely because you don't really understand how the velocity, acceleration, and jerk are being used and what the values you entered mean. You have velocity set at 1000000 counts per second. At the 22000 or so counts per inch you have would put you over 2500ipm rapid speeds. Is your system capable of that? First step is how fast do you want to rapid? Lets say 500ipm. 500/60 gives 8.33333 inches per second. So your 22222x8.33333 = 185183.3333 or there abouts. Pick a nice even number close to that. Acceleration is how fast you get to that velocity. To start with I would try 4 or 5 times your velocity which would put you in the ballpark on velocity. For jerk 5 to 10 times acceleration to start. So 5-10 million. I may be way off base and your shooting for 2500ipm. Either way your following error is way off usable values as far as I can tell. You really need to show all your screens when you post plots so we can look for settings errors you are not aware of. That means when you post a step response plot of a channel also show pics of the filters screen and config and flash screen for that channel. Hopefully you'll get it all sorted. It gets easier once you see how settings effect each other.

    Ben

    Sent from my E6810 using Tapatalk



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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hey Ben

    You are correct, I don't understand which is why I asked for help. Also, I'm used to working in mm, and now find myself having to deal with counts and inches which isn't helping.

    Anyway, I started with the limits that are in the sample config file, which are V 40000, A 400000 and J at 4000000 (which can be seen in the first plots I attached). The plot's didn't look great so taking Tom's advice, and having read the Wiki, I increased P, D & I without much improvement. I then began to increase the motion profile numbers and the plots (to me) looked better and the servos sounded better. The machine definitely moved better.

    Re. max rapid speed, doing the math, the motors are rated at 3000rpm, through 10:1 gearboxes brings it down to 300rpm, and with a 20 tooth gear at 6.28mm pitch means 125.6mm per rev, so 37.6m/min or 4.944 inch per rev so 1483ipm. That number puts V at 500000, so half of what I had set. I should have worked this out earlier so thank you for pointing that out. I'll try A at1000000 and J at 10000000, sound correct?

    I'll make sure to post the other screens next time. Thank you for your help.

    Eug


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Eug,

    Thanks How small, like 0.1 inch or 2000 counts?
    Yes, or the smallest value that wouldn't fault under normal conditions.

    Getting back to the tuning, I found that it's not possible to increase the P over .8 and both D & I seem to have little positive effect on improving the position, but adversely effect the output. Even small amounts like D of up to 1 and I up to 0.00001 had negative effects, however the 2nd order low pass filter did help.
    Let's focus on D Gain. Typically D Gain should be set many times the P Gain (ie 20X) you should increase it until the system goes unstable then back off. D Gain adds damping. Think of it like submerging your entire system in a vat of thick honey. By itself it will slow things down and make errors worse. But it should make the system much more stable and allow you to increase P Gain more than before and result in less error than before.

    I found that the servo sounded and appeared to perform better as I increased the motion profile. I got to the settings on the attached plot but things were starting to move very quickly, so I wasn't sure if there was any point increasing further. How far should I push it? I did read the article on Velocity, Acceleration and Jerk in the Wiki and wanted to work my way through it but I wasn't sure how to command my axis to move to a good starting point in order to do the tests. Also, I found that when doing these tests with a step size of 10000 (approx 1/2" of movement) I would get certain performance but increasing the step size to 100000 (about 5" of movement) would give different results. What distance should I be testing at?
    I see the the output is going to ~1500 DAC counts which is 75% of max. So that is around the max speed of your system. Your test move is not achieving your Velocity Limit of 1000000 counts/sec. That's like testing a car in your driveway with a speed limit of 300MPH and not seeing any problem. You can't assume the car is capable of 300MPH. As soon as you take the car on a highway you wil find its limits. Showing a Velocity plot would tell the story.

    You must test your system for all move sizes and speeds. Generally i start with small slow moves, then increase to larger faster moves.

    Thinking it through, after I turned the PC back on, I should have loaded up the config profile and gone through the channel settings before doing anything else, correct?
    Yes. With slaved axes you must be sure the slave axis is configured and enabled before moving the Master. Eventually your initialization C Program will configure and enable everything. But during testing you must do that manually.

    In the situation where I have channel 1 slaved to channel 0 (with a gain of -1), is there any need to change any of the settings in channel 1 or are they all ignored?
    No. All settings of a Slave axis must be configured properly. Although you would normally never command the Slave axis to move so its motion profile settings would normally not be used if that is what you mean.

    HTH
    Regards

    TK
    http://dynomotion.com


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom

    Thank you again. I recall reading D should be between 2 - 20 x P. I found that any increase of D would just cause instability in output. I'll have another go and make a short video where you can see the other screens and the results of increasing D, and tell me what I'm doing wrong.

    But back to the slave axis for now, as I want to be crystal clear.

    No. All settings of a Slave axis must be configured properly.
    Do you mean by simply copying over whatever motion profile settings I end up with on ch 0 after I'm finished tuning it? Or by temporarily making ch 1 the master, slaving ch 0 to it and repeating the whole exercise?

    Also, currently my Z axis is very close to the top of it's travel and I can't physically move it without disassembling things. How do I command an axis to move in a certain direction/to a certain position? I launched KmotionCNC but the keyboard buttons must not have been mapped correctly as I couldn't get Z to move.

    Eug


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Eug,

    Do you mean by simply copying over whatever motion profile settings I end up with on ch 0 after I'm finished tuning it? Or by temporarily making ch 1 the master, slaving ch 0 to it and repeating the whole exercise?
    Well as I stated if the Slave is never commanded to move and only always follows the Master's trajectory then it doesn't matter what the motion profile settings of the Slave are. However it is probably a good idea to set them the same as the Master.

    I was mainly referring to all the other settings required for the axis to work correctly including PID setting and such. Note its kind of a catch 22 as the Slave must be working reasonably well to follow the Master in order to tune the Master and vice versa. You can temporarily reverse the Master/Slave roles to test the performance of the other axis.

    Also, currently my Z axis is very close to the top of it's travel and I can't physically move it without disassembling things. How do I command an axis to move in a certain direction/to a certain position? I launched KmotionCNC but the keyboard buttons must not have been mapped correctly as I couldn't get Z to move.
    You might command a move on the Console screen. Such as:

    MoveRel4=-10000

    Regards

    TK
    http://dynomotion.com


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom

    I was mainly referring to all the other settings required for the axis to work correctly including PID setting and such. Note its kind of a catch 22 as the Slave must be working reasonably well to follow the Master in order to tune the Master and vice versa. You can temporarily reverse the Master/Slave roles to test the performance of the other axis.
    Yeah, I mistakenly wrote "motion profile" settings but I meant PID, etc. Anyway that's exactly what I was asking and you answered it. Again thank you for clarifying.

    Eug


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom,

    While on the topic of tuning: I have seen mention previously of replacing the D term with a pole/zero filter, could you elaborate on how to go about implementing that without too much pain? I can intuit the effect of changing the D term ok but that filter is pretty abstract.

    Thanks,
    Andy



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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Andy,

    While on the topic of tuning: I have seen mention previously of replacing the D term with a pole/zero filter, could you elaborate on how to go about implementing that without too much pain? I can intuit the effect of changing the D term ok but that filter is pretty abstract.
    Please read this article in our wiki to see if it helps.

    Regards

    TK
    http://dynomotion.com


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom

    I worked my way through determining max V, A and J and have used numbers about 20% lower to do the plots for both Z and Y axis. I tried moves from about .5" to 30" on the Y axis, and 1" and 2" moves on the Z axis.

    Those PID numbers gave me the lowest error with the best performance, and the 2nd order low pass filter of 80Hz gave me the best results. The servos are quite noisy when sitting still. Is this normal and can anything be done to quiet them down?

    In regards to Max Following Error, the lowest I could set it was about 1500 on Z and 2000 on Y at the V, A and J seen on the plots. Any lower and it would trigger an error and disable the axis when doing the tests. Is this OK?

    What's the next step?

    Attached Thumbnails Attached Thumbnails Flexicam ATC router retrofit with Kflop/Kanalog-z-axis-png   Flexicam ATC router retrofit with Kflop/Kanalog-z-axis-error-png   Flexicam ATC router retrofit with Kflop/Kanalog-y-axis-png   Flexicam ATC router retrofit with Kflop/Kanalog-y-axis-error-png  

    Eug


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Eug

    I worked my way through determining max V, A and J and have used numbers about 20% lower to do the plots for both Z and Y axis. I tried moves from about .5" to 30" on the Y axis, and 1" and 2" moves on the Z axis.
    It isn't clear for Z if you tested at your max Velocity. It's still the "testing your car in your driveway rather than the highway" issue. Plot Velocity to be sure and so we can see the Velocity you are testing.

    Those PID numbers gave me the lowest error with the best performance, and the 2nd order low pass filter of 80Hz gave me the best results.
    Its not normal to need a low pass filter less than ~500Hz. Please set it to 500Hz and try again. It isn't clear to me that you optimized D gain (found where the system goes unstable and then reduce until stable again)

    I'd prefer you just work with one axis at a time. Later you can apply skills learned to the other axes.

    The servos are quite noisy when sitting still. Is this normal and can anything be done to quiet them down?
    Let's not worry about this at this stage.

    In regards to Max Following Error, the lowest I could set it was about 1500 on Z and 2000 on Y at the V, A and J seen on the plots. Any lower and it would trigger an error and disable the axis when doing the tests. Is this OK?
    Those errors are still huge. But keep those values for now so that we are able to move without faults to continue tuning.

    One reason errors are huge because you are limiting what the Integrator is allowed to do. Without I gain all the Output is basically created by the P Gain. With only P Gain to get output we must have error because the Output is simply Error x P. From the plots we can see that to move at your speed the output is going to ~ 800 counts. So the error must be ~1000 counts to produce it, See here for more info.

    Please include error plots so we can see the level of error during the moves. You can also attach the raw data saved as a text file. That way we can further plot the data however we wish and zoom in ourselves.

    Regards

    TK
    http://dynomotion.com


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom

    Just concentrating on the Y axis, I reset the filter to 500Hz and reduced the PID and started again. I had to increase Max Following Error to continue.

    Please have a look and tell me what I'm doing wrong. As you see, I'm increasing until I get instability, then decreasing and moving on. It looks like I get smaller errors with low D & I.

    https://streamable.com/zjyvv

    BTW, video is 2mins50sec long and then just repeats.

    Eug


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    Default Re: Flexicam ATC router retrofit with Kflop/Kanalog

    Hi Tom

    Here's another one, I think it's better.

    https://streamable.com/k7w6c

    Also, below are the settings I found to be the most reliable. I could do moves of any size with no instability.

    Attached Thumbnails Attached Thumbnails Flexicam ATC router retrofit with Kflop/Kanalog-reliable-y-png  
    Attached Files Attached Files
    Last edited by xyz-cnc; 09-15-2018 at 02:35 AM.
    Eug


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