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External Axis (on Rotary Table) - Rotation Speed Control

  • shreenath
  • September 9, 2020 at 6:52 PM
  • Thread is Unresolved
  • shreenath
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    • September 9, 2020 at 6:52 PM
    • #1

    Hello!

    My Robotic system consist of a KR60-3 Robot with an external axis (MG_480_180_30 Motor). External Axis is mounted on a Rotary Table and therefore it is set to form asynchronous, uncoordinated movement of the table with desired speed.

    I wish to design a program that reaches the desired RPM of axis E1 as a function of time (i.e. the rotational speed should ramp up or ramp down wrt to time defined by user)

    I have set E1 as asynchronous.

    I use $VEL_EXTAX[1]=<value>

    ASY_PTP(<Value>)

    by changing the $VEL_EXTAX[1] between the program i get a message "Value is inadmissible"

    Kindly help me with the right set of codes.

    Thanks.

  • SkyeFire
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    • September 9, 2020 at 6:56 PM
    • #2

    What value are you entering? $VEL_EXTAX can only accept integer values of 1 to 100. These are interpreted as a % of $VEL_AXIS_MA

  • Fubini
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    • September 9, 2020 at 6:58 PM
    • #3

    What value do you try to assign? Vel_extax needs to be between 0 and 100 since it refers to a percentage of the maximal velocities according to machine data.

  • shreenath
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    • September 10, 2020 at 6:36 AM
    • #4

    I am passing an integer value.

    Also, by passing an integer value how do i get precise RPM value??

    Also, how to do i get a very smooth RPM increment. As of now i get an jurking motion as i cannot finely increment motion ...

  • Fubini
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    • September 10, 2020 at 6:57 AM
    • #5

    $Vel_axis_ma[] is the maximal motor velocity in rpm. If you have some sort of gearing as well you also have to consider $rat_mot_ax[,] which tells you the number of motor cycles per axis cycle. Finally if you also have some coupling $exax_coup[,] contains the coupling factors.

    https://www.roboterforum.de/roboter-forum/…69566#post69566

    Fubini

  • panic mode
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    • September 10, 2020 at 7:53 AM
    • #6
    Quote from shreenath

    Also, by passing an integer value how do i get precise RPM value??

    Also, how to do i get a very smooth RPM increment. As of now i get an jurking motion as i cannot finely increment motion ...

    programmed speed is not a precise RPM value. it is a desired value or upper limit. this is a step function meaning that programmed value can (and it does) experience sudden changes. for example from 100% to 30% and then to 100% again.

    actual value is result of computation by motion planner, filtering and then smoothed by PI controllers (speed and position) which is how you get gradual and smooth transitions. there is simply very long path between setpoint (programmed value) and actual RPM of the motor.

    robot may not be able to even reach programmed velocity, specially if move is short and acceleration is low.

    so programmed value can be an integer 0-100%

    but commissioning is needed to ensure that that scaling is correct (number of poles, gear ratio etc.) the 100% does not exceed any of the limits (motor, gearbox, whatever)

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

  • shreenath
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    • September 10, 2020 at 9:38 AM
    • #7

    after command run of ASYNC_PTP ; can you not change value of VEL_EXTAX[1] ?? is it true??

    After reaching a RPM; i am unable to change the RPM. By changing the value of VEL_EXTAX[] i get a prompt "Value is inadmissible"

  • Fubini
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    • September 10, 2020 at 10:57 AM
    • #8

    Sure you can change it. Probably you just do it wrong. What your mistake is we can not know because we do not know nor have seen your program. So post it and please not some explanations what you are trying to do but exactly the program you run on the controller. Otherwise we stick to madly imprecise guessing as before and probably get bored answering your questions soon.

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  • Asynchronous, uncoordinated external axis movement

    • TVY
    • August 25, 2017 at 7:27 AM
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