Squeeze a fragile object with Robotiq 2-Finger 85

Robotiq_Customer

Hey,

My customer wants to program the gripper to slowly close until the pipette they are picking up is detected and then move to another waypoint where they want to squeeze the pipette to get the fluid out. Here is an overview:

1.      Go to location A with gripper fingers wide open at height h.

2.      Move the arm down to where the object is – pipette – i.e. down by height h

3.      Slowly close the fingers until rq_object_detect is 1 – the object is detected.

4.      Move arm up back to height h

5.      Move to location B

6.      Down the arm by h - slowly

7.      Squeeze the pipette - slowly

8.      Move arm up to height h.

9.      Move to location A

10.   Move the arm down by h- slowly

11.   Release the pipette – i.e. open the pipette

12.   Move the arm up by h. 

13.   Go step 1.

How would you recommend operating the gripper?

Thanks!

Catherine_Bernier

I see 4 steps in the gripper sequence.

Step 1: Before the initial pick up of the pipette.
The gripper needs to open large enough to allow gripping of the pipette. This is easy thing. You can partially open the gripper large enough or simply have it fully open. 

Step 2: . Closing slowly on the pipette to pick it. 
I am not sure how strong the pipette is but if you want to get a good 'weak' grasp such that you don't squeeze the pipette, here are some key tricks. 

• First figure out at which value the gripper should close to pick the pipette (basically figure out the value of the gripper when closed on the pipette (pipette diameter)). 

• Jog the gripper manually using the widget for this. 

• Then add a couple of digits to that number to make sure you pass that position a bit, but not too much that you actually end up squeezing the pipette. 

• Then start from slower speed and lower force and test it. (First find closing force strong enough to hold the pipette then increase speed once you have found that force to reduce cycle time.) In this you need to use rq_set_force, rq_set_speed and rq_set_pos to achieve the above description. 

• Then having the gripper move using rq_move_and_wait

Step 3: Squeezing the pipette. 
I would simple again use a gripper rq_move_and_wait but this time with rq_set_pos to a position that would allow a proper squeeze of the pipette, rq_set_force at a higher value, rq_set_speed could also be at a higher value. 

Step 4: Back to Step 1
This would basically having the gripper open back up to position of step 1 for the next pipette pickup.

Starting from the pick_and_place_demo_with_subprogram, you should be able to program this fast with simple cut and paste!

Hope this helps!

Robotiq_Customer

Thanks for the thorough description.