Rockwell Automation 1771-QB Linear Pos. - Manual (Page 132)

Chapter
9
9-1
Advanced Features
The advanced features of the Linear Positioning Module enable you to
create complex movement profiles, synchronize multiple axes, and perform
cam-emulation. They are not required in order to use the module, and
should only be used once you fully understand how to initiate and control
motion using setpoints.
You can implement complex movement profiles using the motion segments
of the motion block. Such profiles can be executed without the intervention
of the programmable controller. The axis moves from one segment to
another using a user-selectable trigger for each motion segment. You
define a movement profile by downloading one or more motion blocks
from the programmable controller to the module using block transfer
writes. The user-controlled sequence of up to 114 motion segments is then
started by specifying the starting motion segment in the command block.
Each motion segment defines a setpoint and a trigger condition. The
setpoint defines the movement profile for a motion segment, while the
trigger defines the conditions to be met to initiate execution of the next
motion segment. The triggers include position, velocity and discrete inputs.
Movements based on position triggers are called chained moves, while
movements based on velocity triggers are called blended moves. A
movement profile may contain blended moves, chained moves and moves
based on discrete input triggers.
A motion block can contain a maximum of six motion segments. It begins
with a motion block control word and may end with an optional
programmable I/O control word. (See Figure 9.1.) The programmable I/O
word lets you configure programmable input and output options.
ATTENTION: You must use the motion block with caution
because, the programmable controller cannot necessarily predict
the final axis position, since motion segments may be triggered
without its knowledge. You should understand thoroughly the
consequences of all the motion profiles which may occur after a
motion block is initiated, and design the ladder logic to account
for them.
Motion Block