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Catherine_BernierCatherine_Bernier Posts: 144 Crew
edited November 2016 in Applications
I got a request from a customer already owning a FT300.

He wants to make sure the tool the robot is handling is perfectly flat on a surface. How can he use the FT300 for this task?
It's important to consider that the tool position might have a certain imprecision when it's picked up by the gripper.

Edit: The tool has about 1 inch diameter.

@Etienne_Samson, @matthewd92 What do you think would be the simplest way?

Catherine Bernier, Jr. Eng. 

Comments

  • matthewd92matthewd92 Posts: 964Founding Pro, Tactile Sensor Beta Testers Handy
    How large is the contact surface of the tool?
  • About 1 inch diameter

    Catherine Bernier, Jr. Eng. 
  • matthewd92matthewd92 Posts: 964Founding Pro, Tactile Sensor Beta Testers Handy
    edited November 2016
    The thought that comes to mind would be after picking up the tool to move to a known location and measure the torque and forces that the FT is recording. You should be able to ascertain whether the tool is flat or not. 

    Having handled a lot of tools with the gripper I would agree that it's common to have imprecision when the gripper picks up the tool. The best way to combat this is to build a gripper/tool interface that ensures the tool is being held the same way and works towards eliminating the backlash in all of the joints of the gripper. One of the issues wie have seen is that the linkages will "droop" when pickup up a tool. We have drills that we actually have to program in a slight tilt to the tool so that when force is applied we are able to accommodate the movement of the joints. 
  • @matthewd92 Let's say we can grab the tool with the right custom fingertips so it's centered. The programming can bring some challenges too to make sure the tool is really flat on the surface if there is any variation in the orientation of the surface. So how could we use the sensor to make sure the tool is flat? Could we force in Z axis and let the other axes free to move?

    Catherine Bernier, Jr. Eng. 
  • matthewd92matthewd92 Posts: 964Founding Pro, Tactile Sensor Beta Testers Handy
    The easiest would be to use the built-in force wizard and probably a frame point type with the tool as the Frame of reference.

    You would need to have a move in the XY plane of the tool, allow compliance in the Z direction, Rx and Ry rotations as well.  The key that I have learned is to reduce the allowable limits for velocity and rotational velocity way down.  By default they are set to like 150mm/s and 60 degrees/sec.  I usually start at like 10 mm/s and 5 degrees per second and then adjust from there to get the action that I want.  When I first started using the force wizard the challenge was the robot always wanted to flop around, the limits were just too high.  You can then also apply whatever force you need in the Z direction to maintain good contact between the tool and the surface.

    When we did the sanding demo that I posted up in September we wrapped a path node inside of the force wizard so that we could apply a constant downward pressure regardless of how we were holding the tool when teaching the path.
  • Thanks @matthewd92 this is helpful. Could you link to the post you are talking about?

    Catherine Bernier, Jr. Eng. 
  • matthewd92matthewd92 Posts: 964Founding Pro, Tactile Sensor Beta Testers Handy
    @Catherine_Bernier I can't seem to find where I posted it so here is the video again.

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