Rockwell Automation 1771-QB Linear Pos. - Manual (Page 120)

Initializing and Tuning the Axes
Chapter 8
8Ć2
The first step in initializing the module is to adjust the null on each servo valve.
To do so, carry out the following steps:
1. Turn off axis power.
2. Disconnect the servo valve from the module.
3. Start the hydraulic pump and check the system pressure.
ATTENTION: To guard against possible injury keep all personnel
clear of the axis and have a competent person standing by to
disconnect axis power and stop the flow of hydraulic fluid, if
necessary.
4. Adjust the servo null adjustment screw until there is no detectable
movement in the cylinder. In some applications it is important that the axis
should drift towards one end of the stroke if an electrical or servo fault
occurs. In these cases, the valve should be nulled so that the axis drifts at
one quarter inch per second (0.25 ips) in the desired direction. Make sure
the blocking valve or safety plate is energized.
5. Turn off the hydraulic pump.
ATTENTION: Keep the axis near its center of travel. Running the
axis into its mechanical stops could damage equipment.
6. Re-connect the servo valve.
If you load the ladder logic program QB_SETUP (on the accompanying disk)
into the programmable controller to initialize the parameter block, the default
settings will be as shown in Table 8.A. These settings should work for most
applications. Before you load the program, check that the application dependent
parameters noted in Table 8.A are correct for your system. If they are not, edit
the data tables to correct the parameter values. It is strongly recommended that
you also use the axis tuning procedures that follow, to ensure that the settings
you have selected are correct for your application. QB_SETUP assumes that
the module is mounted in slot 0 of rack 0. If your module is mounted
differently, edit the ladder logic program to reflect this. The ladder logic and
data tables for QB_SETUP are illustrated in Figure 8.1 to Figure 8.3.
Important: If you change any parameter block data, you must either cycle
power to the I/O chassis or send a reset command to the module by toggling bit
9 at data table address N45:131.
Adjusting the Servo Valve
Nulls
Initializing the Parameter
Block