How to perform capping operation using force torque sensor mounted on UR5 arm

gauravb

I have a problem where a threaded cap needs to be operated using FT300 sensor mounted on a UR robot automatically. Since the cap pose can't be precisely identified so the FT sensor needs to identify the normal of cap using compliant mode. I want to know how to proceed in this direction.

bcastets

Not sue if it is what you need but maybe this article could be helpful:
https://dof.robotiq.com/discussion/2365/align-part-surface-with-a-plane-using-robotiq-force-copilot#latest
It presents how to align an object on a surface using the FT300.
If the robot is closed on the object and if the object is well aligned with the base surface then you know its normal.

gauravb

Thanks for your reply. Yeah I have seen this implementation. But in this case the force is being exerted with respect to ground and probably gravity is helping in this case. But in my case I need to bring tooltip of the robotiq gripper normal to the surface of cap. The idea is if it approaches normal to the cap surface then it will be able to grip it properly. What i need is a program which keeps applying force on the cap body by tooltip until the force normal to cap top surface component in this case i.e. Fz is highest and rest forces are almost nil. See image for idea. note: Cap can be in any orientation not necessarily normal to ground plane.

bcastets

@gauravb
You can use same programming process. In the article I shared the gravity does not help that much because the zero of the sensor is made before the manipulation to cancel gravity.

You can use a force node with force applied on Fz and free rotation on Ry (stiffness 0%). Wait a little so that the gripper have time to align and you should be good.