KUKA Velocity / Acceleration

    Hi all

    I am new to the KUKA robot programming, and would like to understand how velocity and acceleration parameters work in the robot. The best way I can describe my problem is by giving an example:

    So I have a PTP movement for one axis to move from lets say 0 degrees to 110 degrees. Assume that this axis is A1 (Axis 1), according to the data sheet (see attached file for KR150-2) this axis has a maximum speed of 110 degrees/sec. So if I apply the velocity command $VEL_AXIS[1] = 50, the axis should move at a speed of 55 degrees/sec, and should complete within 2 seconds, given the acceleration is set 0 (no acceleration).

    However this does not happen and finishes faster than expected. Is there something I misunderstand from how the robot works?

    PS. I am using KRC 2 software with a KR150-2 robot.

    As far as i know, PTP movements do not allow to set exact speeds/accelerations.

    You are only able to exactly control the linear and rotational accelerations of the robot's TCP through the motion interpolation so you must use LIN, CIRC or SPLINE movements in conjuction with motion dynamics modifiers.
    You can't set the acceleratons in m/s^2 or deg/s^2 because the maximum value is dependent on the payload.

    Example, move 1000mm at 200mm/s with maximum acceleration possible.

    Code
    ;init movement and BCO run
BAS(#INITMOV,0)
PTP $POS_ACT


;test movement
LIN {x 0, y 0, z 0, a 0, b 0, c 0} c_dis
BAS(#VEL_CP, 0.2)
BAS(#ACC_cp, 100)
LIN {x 0, y 1000, z 0, a 0, b 0, c 0} c_dis

    Motion dynamic modifiers:

    Set TCP linear velocity to 0.5 m/s
    BAS(#VEL_CP, 0.5)

    Set angular velocities for TCP rotation in degrees/s
    (I don't know exactly what 1 and 2 refer to, you have to experiment a little as i did)
    $VEL.ORI1= 90
    $VEL.ORI2= 70

    Set TCP linear acceleration in percentage of the maximum reachable in relation to the payload.
    You can't set the value in m/s^2
    BAS(#ACC_CP, 20)

    Set angular acceleration of TCP in percentage of maximum rechable.
    $ACC.ORI1=100
    $ACC.ORI2=100

    diglo

    Edited once, last by diglo (September 7, 2016 at 2:20 PM).

    Thanks for the quick reply Diglo.

    Your reply clarified many points that I had in doubt, however I do not understand why we can't control the velocity or accelerations when performing a PTP motion. If this is the case then what is the purpose of the $VEL_AXIS[] = ... command? They mention it in the first few examples on the expert programming manual. I understand that its a percentage of the maximum speed but what is it not applying correctly? And is this maximum speed defined somewhere on the robot?

    panic mode
    There is currently no payload or anything attached to the TCP of the robot.

    Of course you can set velocity and acceleration in PTP movements, the only thing is you can't set a metric speed like m/s od gedg/s, only the percentage of maximum.
    PTP is a best-effort motion strategy which will move the TCP between points as fast as possible given the payload (mass and inertia)

    All values are in percentage of max.

    Code
    BAS(#VEL_PTP, 30)
BAS(#ACC_PTP, 100)

    EDIT: BAS() instruction is available in KRC4, i don't know if it's present in KRC2 also. Using BAS() is easier than setting each sys variable...

    diglo

    Edited once, last by diglo (September 7, 2016 at 4:01 PM).

    ok, that's clear to me. one more question, where i can find the maximum values of each Axis stored in the robot? ie. for KR150-2, the maximum value of Axis1 is 110°/s. Where is this data stored in the controller? is it possible to edit that value?

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