CapinWinky
Member
I'm trying to get a better handle on how coordinated motion works on CIP drives like the 6500. From what I gather:
Can someone correct any incorrect assumptions of mine and/or fill in the blanks. Maybe point me to documentation that covers some of these details. I've found 100 pdf documents telling me how to add and configure drives and axes and zero that tell me what is actually going on. The above list is from word of mouth from others, so the details are suspect.
- CIP Sync is used to get the clock in the drive to match up with the clock in the ControlLogix. Variance in the clock values is typically low but increases with each Boundary or Transparent clock. Real world variance measurements appear to be non-existent, but it is implied they are in the single digit microsecond range.
- The PLC does all of the curve calculations to get set points and sends a few of these points, along with clock times the axis should be at the points, every course update period. How many point/time pairs are sent or if it is actually just one point, I don't know, can't find any documentation on this.
- The drives, running at a set cycle time (250microseconds?) handle the PI controller cascade and try to hit the point(s) at the designated times that it received from the PLC. The drive does linear interpolation to define points between the ones provided by the PLC
- Gearing to commanded position is handled by the PLC. It generates the master and slave points at the same time. Gearing to actual position requires the PLC to retrieve the position feedback from the master to generate the slave points (is this feedback data time stamped or jittery regular CIP communication?). The delay for the feedback causes the slave to lag in reaction to master position/speed changes (can this be compensated for?).
Can someone correct any incorrect assumptions of mine and/or fill in the blanks. Maybe point me to documentation that covers some of these details. I've found 100 pdf documents telling me how to add and configure drives and axes and zero that tell me what is actually going on. The above list is from word of mouth from others, so the details are suspect.