Hi guys, what I’m trying to do is let TCP descend and fit onto a plane in force mode, and stop force mode after feeling a certain amount of force from TCP.
I’m looking for the script manual and figure out how to enter and end force mode. I also find the code to get force on TCP, but I don’t know how to let it return a digital output when force on TCP reach a certain amount so I can set a wait DI.
Attaching the code for getting force on TCP.
I think maybe this is a very generic question for all robots, looking forward your help!
Thank you guys!
Hey,
Do you want to solve this in URscript or as a Polyscope Program?
If you are trying to implement it as a Polyscope program have a look at this article:
https://www.universal-robots.com/articles/ur/programming/seek-using-force/
While this example is not exactly what you need it shows one way of using the force value to stop a motion and trigger another motion.
You can download the finished file at the bottom of the page.
Thank you so much, I download the file it seems good with Polyscope but I need to set this with script code cause I am using it in a GH Robots program to do a customized command.
I need to figure out the script code to do this “if do” stuff.
If you want to do it in grasshopper it will be much more difficult to implement:
If you are using the robots plugin you may not be able to simply create a custom command as the custom command is executed after a point is reached. Some workarounds are necessary in order to do it at the right moment in the program.
I have not tested the solution mentioned below. You may need to make some changes before it runs as you want it to.
- Define a Thread that continually runs and evaluates the amount of force at the tcp in your
init commands:
thread ForceCheck():
maxforce = 50 # The thread will stop if a force of more than 50N (~5kg) is reached
touched = False
while force() < maxforce:
touched = False
end
# if the force is exceeded the following code will run:
touched = True
stopj() # stop the robot from moving any further
movel(pose_add(get actual tcp pose(), p[0, 0, 0.1, 0, 0, 0])) # move up by 100 mm
return
end
This thread creates a while-loop that runs until the force is exceeded.
If the force is higher than maxforce the while loop ends and the robot will stop and move 100mm in Z+ direction.
You need this thread as you will need to check the force continually while motion commands.
- You will then need to run the thread at the right time.
Usually this wouldn’t be a problem but it is made more difficult when trying to do it in robots in Grasshopper.
- Create a Target 100mm above the location you want to probe.
- add a custom command to the target with this code:
target_below = pose_add(get actual tcp pose(), p[0, 0, -0.2, 0, 0, 0])
# creates a target location 200mm below the current position
thrd = run ForceCheck() # start the thread
movel(target_below) # move to the target
The robot will try to move downwards by 200mm. If it encounters an obstacle it will stop.
As mentioned I have not tested it but this is how I would approach the task.
If you try it, use extreme caution and test it with a very simple toolpath.
If you run into problems let me know.
Thank you so much!!! I will try it.