| Using the SISO Design Tool and the LTI Viewer | |
Design Constraints for Open-Loop Nichols Plots
For open-loop Nichols plots, you have the following design constraint options:
Specifying any of these constraint types causes lines or curves to appear in the Nichols plot. In each case, to specify the constraint, enter the value in the Constraint Parameters panel. You can select any or all of them, or have more than one of each.
Specify a minimum phase amount at a given location. For example, you can require a minimum of 30 degrees at the -180 degree crossover. The phase margin specified should be a number greater than 0. The location must be a -180 plus a multiple of 360 degrees. If you enter an invalid location point, the closed valid location is selected.
Specify a gain margin at a given location. For example, you can require a minimum of 20 dB at the -180 degree crossover. The location must be -180 plus a multiple of 360 degrees. If you enter an invalid location point, the closed valid location is selected.
Specify a peak closed-loop gain at a given location. The specified value can be positive or negative in dB. The constraint follows the curves of the Nichols plot grid, so it is recommended that you have the grid on when using this feature.
Gain-Phase Constraint
Specifying a gain-phase constraint causes causes a line to appear across the gain-phase plane between the two specified points, with a shaded region below the line.
| | Example: Adding Upper Gain Limits | Example: Adding a Closed-Loop Peak Gain Constraint | |
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