How to upgrade the detection of little object with a gripper?

Context

Sometimes, you could want to detect some really small object. But with the gripper doesn't detect the object when you take it. For that, you need to upgrade the accuracy of the gripper. 

 

Knowledge

Let's take an example : 

If you take a 2F85, the stroke of the gripper is 85mm. We have around 255 bits of command to open or close the gripper. So if we make 85 / 255 = 0,333 mm, that's approximately the accuracy of the gripper. 

If the object to detect is less than 0,333 mm, the gripper will probably not detect it. 

If you don't use all your stoke, there is a way to upgrade the accuracy of the gripper. For that you will need a small object, in this example, I have taken a jar but it's just for the example. 

Before making your detection, you will make the activation of the gripper but you will limit it. So, you have just to close the finger of the gripper and then put your object around the gripper. 

Then you can make the activation of your gripper. 

 

Then the gripper will make the activation but because the gripper will be limited by the jar he will not make a full open. By that, you will limit the gripper on the stroke. So if your jar is 40mm of diameter, the stroke of your gripper will be 40mm.

 

And that is interesting for the rest because the stroke of the gripper is now 40mm instead of 85mm. The accuracy will change also because it will not be 85 / 255 but 40 / 255 so approximately 0,156 mm. 

So you have now changed the accuracy of the detection. 

One thing important is you need to make this activation each time you use the program. So if you want to use it for your program, you will need to have a specific place for the activation of the gripper with always the same object.