DCS Auto Collision Avoidance

    Hello,

    I have an LR-10ia, and in normal operation I have some points created between my two end points, for collision avoidance. If I didn't, the robot takes the fastest path between the two points, however the J3 joint will hit stuff if I let it do that. In normal operation, this is fine. But if the robot gets stuck at any hypothetical position, where a Get_Home would be called for recovery, the robot will again take the fastest path to get to At_Perch...again inducing a collision.

    If I set up a DCS cartesian position check area for the robot to stay out of, will the robot automatically avoid this area? So, before DCS cartesian point check, it will collide. After cartesian point check enabled, will robot gracefully move around the trouble spot, or will it try to enter the area, and stop/fault instead?

    I think my answer is no, per this thread (Have robot avoid area - Fanuc Robot Forum - Robotforum - Support and discussion community for industrial robots and cobots (robot-forum.com)). But that was the only thread I saw on the subject and it was brief.

    If the above answer is no, and collision avoidance is the programmers job, does anyone have advice on how to write conditional logic for point-to-point movement to walk the robot safely back to At_Perch?

    Maybe, if I'm at a known hazardous point, set a DO to latch something in the PLC. If latch set in PLC, call Get_Home, rotate J2 to straight up and down, rotate J1 to a known ok point, then move to At_Perch position settings?

    Brainstorming inside of a question is probably not proper forum etiquette, I apologize. I just don't know if there is a more obvious solution.

    Thanks,

    -J

  • Lemster68 September 6, 2023 at 4:12 PM

    Approved the thread.
    • Best Answer

    DCS will only stop the robot and trigger a fault. Collision avoidance is the programmers job. You can search the forum for "recovery" to see many discussions.

    The method I prefer is to setup additional DCS zones set to "not stop" and tie them to DIs. Then you can see which DIs are on and choose an appropriate path to get home.

    HawkME,

    I like your approach. I was wondering how to define problematic position envelopes programmatically for that purpose, your approach makes more sense.

    Now to search for and learn how to do DCS zones 100% via pendant. Roboguide sounds nice.

    Thanks for having patience with us newbies. Once I search for "recovery" I see you have said this to many people. It is appreciated.

    -J

    Hi, in short yes, it is programmer job to teach homing trajectory.

    As for DCS CPC, it is used for safety robot detection and stopping. So it is not collision avoidance.

    Apart from PLC you can use internal variables F or R to save state and then use it in logic

    For homing there are multiple solutions>

    1. In each point on trajectory set value to variable (GO or R), then you can jump in program based on value, or you can create separate program with trajectories for groups of values.

    ex. J P5 .... DB 0, R10=5

    and in homing you use JMP LBL[R10].

    or IF R10==5 THEN JMP LBL 5

    or IF R10>5 AND R10<8 THEN trajectory ENDIF

    2. You create world zones (space fnc?) with DO signals and use them to check where is robot tcp, then you create trajectories from each zone.

    ex. IF DO5 THEN trajectory ENDIF

    3. You can check actual robot position in world, and use relative movements / offsets to go to free space (like welding table), then drive home.

    ex. PR[5,3]=-100, (in Z)

    PR[10]=LPOS

    L PR[10] ... TOOL_OFFSET PR[10]

    Or in some cases, like palletization, you can just send robot in Z to specific height and then go directly to home.

    ex. PR[10]=LPOS,

    PR[10,3] = 2000, setting Z value

    J PR[10] ....

    You can also read JPOS values and create logic from there.

    I think most common approach is in example 1. but all depends on what is most effective for your application.

    Hi J,

    Quote from DidIDoThat

    If the above answer is no, and collision avoidance is the programmers job, does anyone have advice on how to write conditional logic for point-to-point movement to walk the robot safely back to At_Perch?

    Well ... the possible procedure for recovery / auto homing depends very much on the application:

    - Is it pick and place?

    - Is it a welding robot? If yes: using a welding gun or a torch?

    - How is the gripper constructed?

    - Is the space above the robot free?

    - Is the robot (partially) engaged in a machine / tool?

    - Are there areas into which the robot should / must not move?

    - Are all positions fixed (taught)?

    - Are any or all positions calculated?

    - Does the robot receive positions externally, e.g. from a camera?

    And so on and so on ...

    Depending on the application, there are different strategies for designing a recovery. In addition, it depends on the available software / option packages, as some solutions (although possible in principle) may not be implemented if a specific Option is missing.

    Kind regards,

    J(örn)

    This solution may be what I end up doing. It may be (or maybe not) more time consuming, but easier on my simpleton brain. But I didn't know how to program the lines, so thank you very much for filling in that blank for me. Will have to look more into variable storage.

    HalbesYoYo,

    I readily take your point on it being application specific. So for what that is worth, pick and place. Picks from one point grabbing two parts at once, dual head pneumatic gripper. The space above the robot is free, and if I used all tool paths as a "flip over" movement, I don't think I would have any obstacle avoidance to deal with, but my supervisor didn't like the flip idea. All positions are jogged to and taught, no calculations (don't know how anyway), no vision thank goodness.

    I really do appreciate the help guys. First robots with no training, I'd be a lot worse off without your kindness.

    Quote from HawkME

    DCS will only stop the robot and trigger a fault. Collision avoidance is the programmers job. You can search the forum for "recovery" to see many discussions.

    The method I prefer is to setup additional DCS zones set to "not stop" and tie them to DIs. Then you can see which DIs are on and choose an appropriate path to get home.

    I've done something similar using reference positions. In my case, my areas were distinct enough that I could set reference zones based on J1 to be able to create a safe homing program.

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