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4  Closed loop responses

Closed loop responses are available only in ``rootlocus'' mode. There is a great deal of flexibility in rltool to see various closed loop responses. First you will have to select one ``gain configuration'' out of the possible two. Click on ``Settings-->Gain Configuration''. You will see a selection dialogue box with two choices:

You can choose the gain to be in the forward path like the following figure shows:


This corresponds to the option ``K in forward path''. You can choose to put ``K in the feedback path''. However, ``K in forward path'' is the default.

To see closed loop responses, click on ``Response-->Closed Loop''. You will be prompted to click on a point of the rootlocus to select the ``operating point'' at which you want to see the closed loop response. Once you select the operating point, you are done!

Rltool calculates the closed loop transfer function for the configuration you have selected, i.e. the closed loop transfer function for ``K in forward path'' is
G K
1+G K
and the closed loop transfer function for ``K in feedback path'' is
G
1+GK
You will see a selection menu that shows the following: Click on ``cancel'' to close the response selection menu and return to the main window of rltool.


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