Object tracking on linear conveyor

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Hey everybody,

I encountered an issue with one robotic's subject, I hope that you could help me with it. Let me explain :

Subject :

I work on an UR arm and with a realsense camera attached to the arm. My subject is to pick an object on a linear conveyor.

Insight :

I know the speed of the conveyor by using a wheel encoder. To know the position of the object, I place the arm in an observing position, then when it detects the object, it creates a new TF frame.

I use Reflexxes (an online motion controller) to generate a position and a velocity command. In order to do that, I need to send the position and the velocity of the object and the end effector as the input command of my control loop.

Issue :

I can’t figure out which kind of control loop I need to implement, in which order, and what kind of corrector I need.

I understand some points like :

First, if I do a velocity control loop on the conveyor speed, I will just need to implement a position control loop on my object. But how to cascade them ? And how to send the command to the robot ?

I hope that you could help me. Thank you