Allen-Bradley 1756-HYD02 User Manual page 50

Chapter 2 Cartesian coordinate system
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As the robot moves with incremental moves, towards the end point, the
superimposed move on the concerned axis results in a different axis position than
the one programmed on the path point, resulting in joint values which reach the
user desired position (thereby tracking the object).
Conveyor belt tracking example
The Kinematics ToolFrame sample project shows an example of conveyor tracking
using a 4-axis delta robot. In this example, the conveyor axis is a Master axis which
commands the slave axis: X.
The Conveyor axis is moved using a MAJ instruction. When the MCPM
instruction is executed, the X position on the path point is added to the X axis
position output from the MAG, which is an input into MCTO. MCTO outputs
joint values for the robot, there by tracking the object on the conveyor belt.
The application code also superimposes pick cycle moves using absolute
coordinated moves to pick the objects from a conveyor belt. Because of the
addition of position, the object appears to be on a stationary conveyor. The net
result of the superimposed moves, results in the object getting picked from the
moving conveyor.
Rockwell Automation Publication MOTION-UM002F-EN-P - February 2018