Rockwell Automation 1771-QB Linear Pos. - Manual (Page 25)

Chapter
3
3Ć1
Positioning with the Linear Positioning Module
This chapter explains how the Linear Positioning Module interacts with a
programmable controller to control axis movement within a linear positioning
system.
Figure 3.1 shows how the module functions in a typical positioning system.
Note that the positioning loop closes in the module and functions independently
of the programmable controller’s I/O scan rate. The fast loop update time of
2 ms is possible, because the module has a built-in microprocessor.
Figure 3.1
The Module in a Positioning System
50040
Linear
Displacement
Transducer
Servo Valve
Desired
Velocity
Axis
Velocity
Command
s
Following
Error
dt
Position
Command
s
dt
K
Kp
D/A
Integrator
+
+
F
+
-
Actual
Position
Feed
Forward
+ +
s
dt
Integrator
I
K
dt D
K
d
+
Derivative
1771-QB MODULE
How the Module Fits in a
Positioning System