Gantry Control Mode; Gantry Operation Mode - Servotronix CDHD2S User Manual

Application Setup

6.18.3 Gantry control mode

The CDHD2S gantry system is controlled via a pair of two drives mated via communication
cables. These two drives are called "paired" drives.
The drive of Y1 axis is the main drive. The gantry main drive receives position commands from
the motion controller and executes a position loop on the virtual Y axis (calculated as the average
value of Y1 and Y2).
The drive of Y2 axis is a differential drive. The gantry differential drive handles the error between
the two axes (Y1 and Y2). In a rigid gantry system, its role is to keep the error between Y1 and Y2
as close to 0 as possible.
Note: While the error can be set to a non-zero value (as defined by the controller), the goal for
gantry is usually 0 error between the Y1 and Y2 axes.
Position
Command
Position Feedback
0*
Position Feedback
Note: Main and differential controllers are available for both rigid and flexible gantry types.
However, for rigid gantry, it is not recommended to use a differential controller, and the
gain parameter of the differential controller should be set to 0.
In a flexible gantry system using fieldbus, the motion controller can send non-zero reference
commands to the gantry differential axis.
The parameter GANTRYCMDTYPE defines whether to accept or ignore (fixed at 0) differential
commands.

6.18.4 Gantry operation mode

The CDHD2S gantry drive is only valid in position operation mode.
When COMMODE=0 (serial communication; without fieldbus), the operation mode can be
gearing mode (OPMODE4) or serial positioning mode (OPMODE8).
—179
—
+
HD Loop
-
(Y1+Y2)/2
+
HD Loop
-
(Y1-Y2)
Figure 6-58 Gantry control module
+ Current
Controller
-
+
Current
Controller
+
Y1
Y2