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Stability
If a disturbance to the servo loop causes oscillations with an amplitude that does not change or one that is quickly increasing, then an axis under closed-loop control is not stable. When this occurs, the controller usually generates a
When you examine how stable an axis is, there are three stability margins that you can use: phase margin, gain margin, and sensitivity peak. The Phase Margin (deg) is a calculation option that you can specify for the Closed Loop Tuning and Open Loop Tuning tools. The application shows the phase margin, gain margin, and sensitivity peak directly below the plot in the Frequency Response module. You can make an axis more robust to variation in loading conditions by using more conservative stability margins when you do servo tuning. But this method might have a bad effect on the dynamic performance.
Figure: Margins and Axis Stability
