Rockwell Automation 1756-HYD02 ControlLogix Hydraulic Servo Module - Manual (Page 69)

Publication 1756-UM525A-EN-P - June 2003 69
Using the 1756-HYD02 Module Features Chapter 4
Direction Scaling Ratio The directional scaling ratio compensates for the difference in the maximum speed in the extend vs. retract
direction on single-ended hydraulic cylinders. Different piston areas on the cap (blind) end compared to the
rod end of the cylinder cause the speed difference.
To find this value, you can run the auto-tune routine in both directions and find the ratio of the velocity
scaling in the two directions.
Enable Low-pass Output
Filter Enables the axis loop’s low-pass digital output filter.
During tuning, if the controller detects a high degree of tuning inertia, it enables the Low Pass Output Filter
and calculates and sets a value for Low Pass Output Filter Bandwidth.
Low-pass Output Filter
Bandwidth This Hertz bandwidth value filters out high frequency variation of the hydraulic module output to the drive.
All output from the hydraulic module greater than the Filter Bandwidth setting will be filtered-out, and not
sent to the drive.
If the Low-pass Output Filter Bandwidth value is set to zero, the low-pass output filter is disabled. The lower
the Filter Bandwidth value, the greater the attenuation of these high frequency components of the output
signal. Because the low-pass filter adds lag to the position loop, which pushes the system towards
instability, decreasing the Filter Bandwidth value usually requires lowering the Position or Velocity
Proportional Gain settings to maintain stability. The output filter is particularly useful in high inertia
applications where resonance behavior can severely restrict the maximum bandwidth capability of the
position loop.
Manual Adjust Click on this button to access the Output tab of the Manual Tune dialog for online editing.
The Manual Tune button is disabled when RSLogix 5000 is in Wizard mode, and when you have not yet
saved or applied your offline edits to the above parameters.
Feature: Definition:
Hydraulic Cylinder
Cap End
Rod End
Rod
Piston
Cap End Area =
[(Cylinder Radius) 2 x (pi)]
Rod End Area = [(Cylinder Radius) 2
x (pi)] [(Rod Radius) 2 x (pi)] –
Directional Scaling Ratio =
Cap End Area
Rod End Area
Depending on your Feedback Polarity Setting
Directional Scaling Ratio =
Rod End Area
Cap End Area
or