Creating Plots for Tuning

To successfully calculate valid gains using the Tuning Wizard - Use Existing Plot method, you must first generate good plots of motion. The plots should show some motion with changes. Make sure the plot does not include hitting the end, getting stuck, etc. Make sure the Output Polarity was correct when the plot was captured, that is, that a positive Control Output results in movement in the direction of increasing position units.

Plots of motion should:

Contain significant motion. Slight changes in position, pressure, or force are usually not enough.
Include the Control Output and the Actual Position, Actual Pressure, or Actual Force.
Not include long sections of no motion.
Contain motion in one direction only. If your position system behaves differently in each direction of motion, you will need to generate two plots—one for each direction of motion.
Be captured at the smallest loop time possible and uploaded in capture mode. Do NOT use plots captured in trend mode, as they can cause inaccurate results.

Generating Plots

To generate a plot of motion:

Tune the axis using only the Proportional Gain.
Increase the Proportional Gain until the axis tracks well.
Move the axis in both directions, making sure to get a plot of each direction of motion.
In the Tuning Tools, click the Tuning Wizard button.
In the wizard, choose Use Existing Plots and continue.
In the wizard, choose the two recent plots you made of motion.
Complete the wizard, and the Gain Calculator will open. Now you can choose gains and move the axis.

If you are not able to move the axis with Proportional Gain, try using Open Loop commands to move the axis. With the Open Loop Rate (10) command, move the axis and stop it, then upload the plot. You may need to set the plot duration to be long enough to capture both the start and stop in the plot.