Constant remote TCP with UR

Alexandre_Pare

Hi Pros!
I have been working on a certain application and I wanted to get some advice from you. The application is a deburing application where the deburing tool is fixed and the robot is holding the part. Below is a video of the application with a dummy part that I used to illustrate the issue that I have. The problem that I have is that I want to have the relative speed between the deburing tool and the surface of the part to be constant. So basically I would need the TCP position to update continuously to always be at the point of contact between the part and the object. Otherwise, when the robot tool changes directions I get speed variations on the trajectory. Since the part that I have is not on a straight line, I use the path recording option with the Robotiq FT sensor in constant speed mode to record the trajectory. So off course programming various waypoints with the proper speed would do it but this is long, considering that the clients has many parts to program. Do you have any advice how I could do this?
https://youtu.be/Yq_2TaR7nnQ

Alexandre_Pare

@luke_savage How did you deal with this in your application? I was also wondering how many waypoints you got programmed in your program. 
https://www.youtube.com/watch?v=DfkcvX-qDRA

matthewd92

@Alexandre_Pare you should be able to use the moveP function as that maintains a constant speed regardless of the moves, the maximum speed is set based on the smallest radius that you have, have you tried that?

Alexandre_Pare

@matthewd92  thanks for the tip. I did not try this. The part that I used in the video is a plastic cover for a box we have in our lab. In the real application the part has a more complex trajectory so using the Path recording option with the Robotiq FT sensor is a must. @JeanPhilippe_Jobin how does moveP fit within the path recording option?

Johnson_Liu

[email protected] for the deburring of plastic & metal parts, that we experienced many cases, e.g. Keyboard of desktop, computer case(cover), cell phone case, bicycle parts(curve handler), also the polishing applications of it. That's better to use mechanical compliance tool functions than adjusting the programs continuously, especially for more complex parts and parts model changes frequently.
Please refer the website of Amtru AG- Swizerland company that spin off from ABB Flexible Automation Switzerland-www.amtru.com, we cooperating with them since 2009 cell phone case polishing and get good result, I will send more data for your reference, the tooling will save more than 70% programming time, cause the compliance functions acting by air supply and adjustable. Using Robotiq gripper to handle the different parts to fit the fixed tooling stations(1 more if needed) and it will save a lot of time and getting efficiency. Johnson Liu 

Alexandre_Pare

@Johnson_Liu
The tools that you used from AMTRU AG was this on Universal Robot or you used them on ABB? How does the control work for these tools?

matthewd92

@Alexandre_Pare I also looked at some tools like this at Automatica that use air pressure to regulate the amount of force that the tool is placing onto the object being deburred or polished.  I think I have some literature on them, I will see if I can find it when I am back in the office later today.

Johnson_Liu

@Alexandre_Pare, I try to send you the Amtru tools data including spec., drawing and functios descriptions, the air spindle is freely compliable in all directions. The pressure against the part edge can be set from the robot program(Flexicut Series)/ or using radial arranged springs to provide the filling pressure onto the parts edge(Flexifile2000), the spindle is possible to deburr around circles and corners without changing the tool orientation.Johnson Liu 

Johnson_Liu

Alexandre_Pare, The tools can use on any robots or CNC machine, install on robot side or fixed on the station, that depend on the parts size & weight /or tool's weight and that need to considering payload of robots. We use it on ABB & Fanuc robot, also Everrobot ( Taiwanese Robot company), you also could find the same deburring tool  on AT I website, UR should be no problem to run with it. our Partner -China now using Amtru Finishtool 250 to surface polishing the track rail of High Speed train, Johnson Liu 

MarcAntoine_Lacasse

From the How-to of UR web site I found an example that show how to modify the speed slider from inside a robot program :

http://www.universal-robots.com/how-tos-and-faqs/how-to/ur-how-tos/setting-the-speed-slider-from-a-program-15293/

I modified the Robotiq force sensor template program to set the speed slider based on the force (see Thread_2 on picture)
I filtered the speed parameter with a moving average to obtain something smooth and try this with a trajectory recorded with the Path node.
This program executes the recorded Path with a speed that decreases when the force increases. It could be useful in deburring task to reduce speed accordingly to cutting force. 

Someone could use a similar speed slider hack to adjust the speed at contact point of a fixed deburring tool, for example using the distance between robot flange and tool as parameter.

matthewd92

@Alexandre_Pare this was one of the systems that I looked at in Germany in June, its made by Fer Robotics.  Here is a video, not sure if this is what you would need but it keeps a constant force on the object so that the robot does not have to follow the contour precisely.  https://www.youtube.com/watch?v=IlarUg5y0b0

Alexandre_Pare

@matthewd92
Thanks for the info. However, the issue that I had was concerning the relative speed between the object held by the robot and the tool which was mounted on a table. As you turn the TCP, its speed at the contact location may change even if you have a constant robot TCP. I think what @MarcAntoine_Lacasse said can help!