René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Allow the initial phase of a bode plot to be specified","articleBody":"The output of the `bode_plot` function is bounded to between -180 degrees and 180 degrees and doesn't account for conditions when the phase should leave these ranges. For example a phase angle of -270 degrees will be represented as 90 degrees on the bode plot. To illustrate this, I've got a simple example below:\r\n\r\n```import numpy as np\r\nimport control as ct\r\n\r\nm = 2\r\nk = 100_000\r\nWci = 2*np.pi*500\r\n\r\nG1 = ct.TransferFunction([1],[m, 0, -k])\r\nG2 = ct.TransferFunction([1], [1/Wci, 1])\r\nG3 = G1*G2\r\n\r\nct.bode_plot([G1, G2, G3], dB = True, Hz = True)\r\n```\r\n\r\n![image](https://user-images.githubusercontent.com/47535659/78391273-ab2e0a00-75ab-11ea-89ca-5fdb2827084c.png)\r\n\r\n-G1 (blue curve) contains two poles and a DC gain and has a phase angle of -180 degrees.\r\n\r\n-G2 (orange curve) is a simple pole with no DC gain and thus has a phase that starts at 0 degrees and goes to -90 degrees\r\n\r\n-G3 (green curve) is the product of the two transfer functions which on the bode plot corresponds to adding of the curves. We should see the green curve start at a phase of -180 degrees and go to -270 degrees but it does not do this because of the way that the phase angle is computed.\r\n","author":{"url":"https://github.com/Nick-Hemenway","@type":"Person","name":"Nick-Hemenway"},"datePublished":"2020-04-03T18:12:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/388/python-control/issues/388"}