Using the Force-Torque sensor for offseting waypoints

david_firam

Hello,

I am currently working on an application to pick and place some parts using the UR10 robot. Our robot is installed on a mobile platform that can be manually moved making it ideal to take the robot out of the production line in case something unexpected happens.
My goal is to use the FT300 in combination with a custom gripper to palpate the machine so I can offset the robots waypoints in case the robot was moved from it's previous position (not much, just a couple of mm). Our application requires the robot to pick and place parts on centering pins so accuracy is a must.
I was wondering if the FT300 sensor is feasible for accomplishing such a task.

Thank you

Etienne_Samson

@david_firam @Catherine_Bernier yes you can do that, you just need to teach your pick and place using a relative frame. That reference frame will be set according to your reference that you can find probing with the FT sensor.

That being said, it's going to be very hard to reach the required accuracy doing only that what is your required accuracy for the pin insertion ? From my personal experience, you will probably need to use the force sensor to guide your insertion. Basically, you will leave compliance during the insertion, and use the force sensor to apply a force downward while your motion in X and Y is compliant, thus you will "find" the hole and insert in it. That would leave you some room for inaccuracies for the robot cell not being perfectly in place.

matthewd92

I agree with @Etienne_Samson in that you will probably want some way to affix the robot to a known point on the machine or the floor in front of the machine. We use female floor anchors with brackets on our mobile stand that slide up and down on a shoulder bolt so that if the robot needs to be moved, you simply unbolt it and the slide the brackets up, unlock the casters and roll it away. Then when it goes back it is very close to the same position. Definitely within range of using a FT sensor to place parts on centering pin, especially if the pin has any taper at all to make placement easier. 

if you don't need to operate at any real velocity, we actually did this same thing with another robot but made our own floor anchors that were bored for taper T-Handle pins and the ladies moved it into place evermornignn, dropped the pins in and ran it all day. At the end of the shift they simply pulled the pins and rolled it away for cleaning. There was no realigning the program each day. We were close enough to accommodate the very slight misalignment with the gripper tooling. 

Catherine_Bernier

Thanks David for this great question!

@matthewd92, @Nicolas_Lauzier what do you think?

david_firam

Hey @Etienne_Samson, thank you for the answer. I am planning on using the FT sensor also for the insertion of the part in the machine but my biggest concern is the position of the robot related to the machine. My plan is to make the application as simple as possible for the operator to work with so no programming knowledge is required. So after the robot is installed on the line I would like the operator to initiate a offset procedure with the push of a button so the UR can automatically start palpating the target machine and offset the main path waypoints. Afterwards when the robot places the part in the machine I also plan to use the FT sensor to achieve a certain compliance level. 

Catherine_Bernier

@david_firam Since we are talking about mm, could you simply let the FT300 guide you to insert the part in and once it's a success you can record the new position of the robot to reach the target? Can you share some images so we see if vision can help you locate those pins?

Etienne_Samson

@david_firam for your initial positioning you should use 2 holes on the floor and have your mobile plateform.

Here is an example of mobile platform done by Faude, one of our partner in Germany, they sell this as a standard cell. It's on wheels to move it around but then the handle on the side will fix it and the 2 rods you see on the bottom will align it infront of the CNC machine. They sell this standard machine tending cell with our Gripper on it by default with optional FT Sensor and Wrist Camera. They are not the only distributor doing that, I'm sure @Catherine_Bernier could help you find someone doing that in your area!