KUKA motor motion

  • capital9
  • Thread is Unresolved
    • #1

    hi people,

    i am using the product designed for rotating application, which is supposed to be controlled with the KUKA motor. Motor name is MG_40_80_45_S0. but the problem was when we connected the system along with the gear box it was rotating in weird motion i.e it rotates few deegrees then stops, again rotates few degrees and it stops, this motion continues.(when whole system is connected).

    but when we use small hand drill machine to rotate the system, whole thing rotates pretty smooth and it is not even as powerful as Kuka motor we are using.

    It made us realize may be we are missing some parameters setting, we have tried various different settings and failure was the result.

    has anyone before worked or experienced such situation?

    or if you guys have any idea what we might be missing ?

    • #2

    How exactly do you cammand your motor? Using a KRL program from KRC or something else? If by KRL probably no blending between your motions.

    the product designed for rotating application

    whats this product?

    when whole system is connected

    whats this system?

    Try to be more specific.

    Fubini

    • #3

    Motor is controlled by KPP 2-40 Amps, which has RDC.

    The have not programmed it yet, but we are manually driving it with KUKA smart pad. just like controlling the axis of KUKA Robot.

    About the product i cant say much, it is disclosed product and is meant for the company. but just know that its function is to distribute objects by rotating.

    And we control distribution by KRC4 which includes rotation of servo, distribution of objects etc.

    may be i can ask you about the parameters of motors.

    have a look at the parameter settings, i havent found any details regarding these.

    and i feel i am making mistake here. Guide me to understand these parameters.

    • #4

    Quote

    we are manually driving it with KUKA smart pad

    How exactly? Incremental mode maybe? In incremental mode only a certaim distance is traveled, then motion stops. Pushing the button again again only a defined incremental step is done.

    Fubini

    • #5

    if you are jogging continuously and this still happens, it would suggest wrong axis tuneup. try increasing speed.

    • #6

    Fubini  panic mode

    hi not only manual jogging but using a program to control the motor gave similar result,

    but we have been changing the parameters of velgain, posgain and velint time, and it sometime improves the motion and sometime does the same thing.

    Manual doesnt help at all like what are these parameter, how to calculate the correct values? the manual from kuka xpert only tells the standard value and also tells the value may differ according to load used.

    that doesnt help at all.

    thats why i asked if anyone knows about those parametes.

    • #7

    well to learn how to do this is not a simple thing. you need o study engineering, take courses on control systems, calculus, how to use step function etc. and of those that did this, maybe 1% actually understands it. in other words learning how to compute the values and plug them in is not something you are going to learn by reading one post online.

    another option is to try to make incremental changes and observe response using trace tool (oscilloscope). this still requires understanding what the response is supposed to look like. goal is to reach target and settle as quickly as possible without overshoot and undershoot. this is covered to some degree in various manuals. there is a manual about configuration of external axis and another about using oscilloscope

    then there is another option using tune servo program (courtesy of KUKA). it was meant for system partners but you can ask and see how it goes.

    • #8

    The stop&go motion sounds very strange. Does the robot throw any messages while this is going on? While you're just holding down the jog key, or executing the test program, does this stop&go happen, or only at interruptions in the motion?

    The first thing I would do, would be to create a simple test program that moves the axis some number of degrees (from 0 to 90 in a single motion command, say), and trigger an O-Scope trace as the axis starts to move. You'll want to look at the actual and commanded velocities, and see if they track each other. Some noise will always be present, but what you want to look for are major deltas, and spikes.

    Now, the O-Scope trace only tells you what the motor is doing. If you don't see the motor stop&going when the physical axis is, then your issue probably lies "downstream" of the motor, in the gearing between the motor and the axis itself.

    If the motor does stop&go during what should be a continuous motion... that's odd. I would expect to see errors in that case.

    It could be the dynamic tuning of the axis, but normally that shows up at the start and end of a motion, not the middle. An external positioner often needs to be manually tuned, to work with the weight and inertia of the positioner. On KRC2s, it was a matter of tuning the P, I, and D gains incrementally, using the O-Scope to see the axis performance, but I've never done it on a KRC4. If you can figure out which KRC4 gain variables map to Proportional and Derivative, you can probably tune it -- start with both gains near 0, then slowly ramp up the P until the axis starts oscillating at the start/end of motion, then start ramping up the D until the oscillations damp out.

    • #9

    SkyeFire

    The motion is go and stop, and this repeats all along. when the motor is separated from the system then motor runs pretty smooth and it applies for all kind of motion i.e jogging manually or programmed.

    but when the motor is connected to the load, it starts behaving weird, i.e. go and stop motion.

    we have been trying to smooth it out with parameter change as mentioned above but haven't perfected it yet, it has been relatively smoother though. and during the motion there are no errors at all. but if we change few parameters then error starts showing up.

    Whole system is supposed to only rotate 360 degrees, so we don't need to speed it up or anything but still the go and stop motion is weird behavior.

    we will be trying other possible ways and ask help with the KUKA.

    and thank you for the reply.

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