Delta RMC151 - Manual (Page 43)

2 Starting Up the RMC
If you are using a feedback device that gives only velocity feedback, such as a
tachometer, see the Analog Velocity Scaling topic instead.
To scale a position system to show the velocity in fpm or rpm, you need to set the
Position Scale parameter. The Position Offset need not be set if you are only concerned
with velocity and not positions.
Position Scale Parameter for a Linear Axis
1. Determine how many Counts the feedback device gives in one foot or one revolution.
2. Open the Scale/Offset Wizard. If it gives a choice, choose Position/Counts.
3. In the First Measured Position section, enter zero in both boxes.
4. In the Second Measured Position section:
• Enter the number of counts per foot or revolution in the Raw Counts box.
• Enter 60 in the Measured Position box.
5. Click Next. The calculated Position Scale will be displayed.
6. Click Next and complete the wizard.
7. Run the system and make sure that the Actual Velocity is correct.
8. Set the Display Units axis parameter to the desired units. For RPM, choose rpm·s. This
will result in the velocity being displayed as rpm. For FPM, choose fpm·s. This will
result in the velocity being displayed as fpm.
Position Scale Parameter for a Rotary Axis
To scale a rotary axis to RPM:
1. Set the Position Unwind to 60.
2. Set the Display Units axis parameter to rpm·s. This will result in the velocity being
displayed as rpm.
2.3. Tuning
2.3.1. Tuning Overview
Once your system is set up and ready for use, it must be tuned in order to control it. Tuning is
the process of adjusting the tuning parameters for optimum control of the system. The better
tuned a system is, the closer the actual movement follows the desired path of movement.
Why is Tuning Necessary?
Tuning is required for moving an axis in closed loop control. In closed loop control, the
RMC generates a target profile. The tuning parameters (gains) then dictate how much
Control Output the RMC should generate each loop time in order to get the Actual Position
to follow the target profile as closely as possible. The gains must be properly tuned to
achieve precise motion.
On a well-tuned system, the Actual Position will closely follow the Target Position. To see
a plot, click here.
This is a plot of a system that is well-tuned:
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