Rockwell Automation GMLC Reference Manual - Manual (Page 288)

Publication GMLC-5.2 - November 1999
Configure Cam 251
By configuring the next cam profile as a pending position-lock cam while
the current profile still executes, you set the appropriate parameters ahead
of time. This makes the transition from the current profile to the pending
profile seamless—synchronization between the master and slave axes is
maintained. To ensure smooth motion across the transition, however, be
sure to carefully design your cam profiles so that no position, velocity, or
acceleration discontinuities exist between the end of the current profile
and the start of the new one.
Unlike regular position-lock cams, initiating the new (pending) cam
profile requires no subsequent Position Lock Cam block. Once a pending
position-lock cam has been configured, the new profile takes effect
automatically (and becomes the current profile) the next time the master
axis passes through either the start or end point of the current profile. If
the current cam is configured to execute continuously, the new profile
initiates upon the completion of the current pass through the current
profile. The motion controller keeps track of the master and slave axis
positions, relative to the first profile at the time of the change, and uses
this information to maintain synchronization between the profiles.
After a pending position-lock cam has been configured, the
PCAM_pending_profile_status variable for the selected slave axis is 1
(true). When the new (pending) profile is initiated and becomes the
current profile, PCAM_pending_profile_status = 0 as shown below.
Master Position
Accel
Profile
Operating
Profile
Decel
Profile