Delta RMC151 - Manual (Page 199)

3 Controller Features
c. Make sure the task does not stop when an axis halts.
7. Tune the Axis
a. Tune the axis manually (auto-tuning does not work in RUN mode).
8. Add Other Code
• If other values need to be changed when the feedback is switched, add the necessary
code to the expression. For example, some applications may require different tuning
gains for each feedback.
• Depending on the application, more programming may be needed to make a smooth
transition when switching feedback.
3.10.3. Feedback Linearization using Curves
This topic describes how to implement single-axis feedback linearization by using a curve to
define the relationship between the transducer and the real measurement you need. For
example, a curve can be used to linearize a transducer with as many points as you need. Or,
consider a transducer mounted in a cylinder that drives a swing arm, but you actually need
the position of the end of the arm. Given the machine geometry, a curve can be used to
convert the transducer measurement to the position of the swing arm.
Another method of feedback linearization is via a mathematical formula, as described in
Feedback Linearization Using a Mathematical Formula.
Tip: The Examples section of Delta's online forum includes a Feedback Linearization Using
Curves example. You can use that example to help you get started.
Setting Up Feedback Linearization
Read the Custom Feedback topic before completing this procedure.
1. Determine Actual Measurement Versus Transducer Measurement
a. Determine the relationship of the desired true measurement to the transducer's
measurement. This may be in the form of an equation, or measurements taken at
a number of points throughout the transducer's measurement range.
b. Assemble the data as a table of data consisting of the desired true measurements
and the transducer's measurements. If you have an equation, you can use a
spreadsheet program such as Microsoft Excel to calculate points from the
equation.
2. Create a Curve
a. Create a new curve in the Curve Tool.
b. In the curve data, enter the transducer's values in the x-axis. Enter the desired true
measurements in the y-axis. If you have the data in a spreadsheet program such as
Microsoft Excel, you can copy the data and paste it into the Curve Tool.
c. Make sure the x-values will cover the entire travel range of the physical feedback. If it
does not, you may encounter a runtime error when you run the system.
d. In the curve properties, set the Endpoint Behavior to Natural-Velocity.
e. In the curve properties, set the Interpolation to either Cubic or Linear, as required
by your application.
Note: It is important that the x-axis contains the transducer's values, and the y-axis
contains the desired true measurements.
3. Define Custom Axis and Reference Axis
deltamotion.com 179