User manual

66 Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015
Chapter 2 Configure Integrated Motion Using a PowerFlex 755 Drive
Figure 3 - Base Update Period Example
The Base Update Period is a trade-off between updating positions of your axes
and scanning your code. For a 1756-L6x or 1756-L6xS controller, you can have
4 axes/ms and 8 axes/ms for the 1756-L7x controller.
For detailed information on the Axis Scheduling function, Axis Assignment tab,
and Alternate Update Period Scheduling, see Configure Axis Scheduling on
page 77.
Integrated Architecture Builder
To help you determine motion system performance, use the motion performance
calculator in the Integrated Architecture Builder (IAB).
The IAB is a graphical software tool for configuring Logix-based automation
systems. It helps you select hardware and generate bills of material for
applications that include controllers, I/O, networks, PowerFlex drives, On-
Machine cabling and wiring, motion control, and other devices.
You can find the software at
http://www.rockwellautomation.com/en/e-tools/configuration.html
TIP
Check to see if the Last Scan time values on the Attribute tab are less.
Typically, the value is less than 50% of the Base Update Period.
Motion Planner
Scans of your code and
system overhead.
0 ms 10 ms
20 ms 30 ms 40 ms
In this example, the Base Update Period = 10 ms. Every 10 ms the controller stops scanning your code and whatever else it is doing and
runs the motion planner.