Discussion

Left ArrowBack to discussions page
C_HooverC_Hoover Posts: 6 Apprentice
I'm currently having the issue where during our application of putting threaded inserts into holes in a box with a UR 5 if the force becomes too great for the robot it faults out and can't return to the previously programmed points. It gets close but is still off enough (~1mm) to throw off the insertion. Has anyone dealt with this or know of any way to fix it?

Best Answer

Comments

  • C_HooverC_Hoover Posts: 6 Apprentice
    edited October 2016
    Thank you, I'm relatively new to programing the UR but I'll have to play around with the force functionality of the robot. The robot, in its current configuration is really prone to "flopping" over, but that's another issue in its own. Do you know if the maximum force the robot is able to apply is velocity dependent or is the same at any velocity?
  • matthewd92matthewd92 Posts: 491Founding Pro, Tactile Sensor Beta Testers Handy
    Since the standards call for limiting impact, I would presume that the force allowable varies with speed, being the faster you go, the less force you will be able to exert due to momentum.  One of the things that we do is we will move very fast until right before we need to do a precision process.  We will then slow way down and make that move.  There is also a function you can use to verify if the arm is actually at rest if you need to make sure that its not moving, is_steady().  We have used that when we want to move really quickly but then use a force function to make sure that the force function is not seeing residual bounce from the deceleration since we have a number of robots that not only are running at 80-90% of max speed they are also just about maxed out on acceleration values as the cycle time on several of them is very critical.

    Also, make sure that any points that are critical do not have blends as that can throw off the actual placement of the robot in the point.  You need to have a waypoint with a stop here condition prior to anything that is critical in nature.

    When you say the robot tends to "flop" over a lot what do you mean by that?
  • C_HooverC_Hoover Posts: 6 Apprentice
    Thank you, by flop I meant that the current configuration that the robot is in requires a large number of joints to rotate in order to move in certain directions. Being that the robot tries to maintain a certain linear speed it can cause the wrist joints to quickly flip around or swing down to complete a move. The robot will soon be re-mounted in a more appropriate setup shortly however. Also I am not very familiar with the script commands the UR uses. Do you know of any literature or anything that would help me understand or at least show me a list of available commands and their function? 
  • matthewd92matthewd92 Posts: 491Founding Pro, Tactile Sensor Beta Testers Handy
    @C_Hoover here is the link to the URScript 3.3 manual, assuming you are running a 3.3 version software.  You can find all the manuals, drawings, software updates at the Universal Robots Support page.  There are some how-to's and FAQ's out there as well.  The how-to's are not always as clear and complete as they should be.  The best advice I can give about URScript is to just dive in.  The great thing is you can write your own functions so that programming can be easier.  For instance, most of our installs we use pneumatics for something.  SO with a gripper usually you will want a delay anytime you open or close it to give it a chance to perform the action.  You would normally have to write something like:



    With URScript though you can write a simple function like this:



    So that you can now write your program like this:



    This is a very simple case of how to use the script functionality.  We have a standard library of our own functions that we deploy with each of the robots.  It allows us to simply call the things that we do a lot on each of the robots and not have to recreate the wheel each and every time.

    I highly recommend playing around on the UR support site.  The great thing is you have a simulator that you can put on your desktop that matches exactly to the robot.  We will write a bunch of code on the laptop and then simply transfer it to the robot.  Its easier to type out complex stuff that way.  One of the gripes I have with the UR touch pendant is there is no way in Polyscope to define and external keyboard as anything other than Danish....makes it hard to type on one when you have to remember that " is shift 2 and that none of the other symbols line up either.
Sign In or Register to comment.
Left ArrowBack to discussions page