Parker Hannifin
home | products | how to buy | support & downloads | literature | search

Click Here to go to new EM&D Knowledge Base (FAQ) site

Following: Master Slave Distance Mismatch Error


D is the distance of the slave axis.
The FOLMD is the distance of the master axis.

In MC0 mode, this equation is checked for the entire move distances. In MC0 mode, the slave will move a distance given by D in the same amount of time that the master moves FOLMD. This makes sense if the ratio were 1, the follower could never move ahead of the master. This is less intuitive when the ratio is not one and numbers programmed for the D and FOLMD need to be checked. If this equation is violated, the controller cannot calculate the trajectory of the slave axis and the Master Slave Distance Mismatch error occurs because the move distance for the slave doesn't make sense for the master distance and the ratio set.

The ratio of the FOLRN/FOLRD is how the slave's velocity relates to the master's velocity. If the ratio is 0.5, the slave will travel at half the velocity that the master travels. Hence, if the master is moving at a constant velocity the ratio is a constant (scaled) velocity.

For MC1 mode (continuous following), the FOLMD defines the distance overwhich the follower is accelerated to speed. The D / FOLMD must always be greater than or equal to the previous segment's ratio, but less than or equal to the current segment's ratio:
Ratio (previous segment) =< D / FOLMD =< Ratio (current segment)

Again, the follower cannot be commanded to move ahead of the master or the Master Slave Distance Mismatch error will occur. In MC1 continuous following, the ratio can be dynamically changed allowing the D to be changed but the value must be set to satisfy the equation for the controller to calculate the trajectory.