René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Phase shift in bode plot","articleBody":"Given the transfer function\r\nG = 1/s^3\r\nWe should see a constant negative phase of -270°, which is confirmed in matlab\r\n\r\n![image](https://user-images.githubusercontent.com/71486197/98642118-2c613280-232d-11eb-8987-59973bff4dcb.png)\r\n\r\nHowever, both **control.bode** and **control.matlab.bode** give 90° instead of -270°. Although technically the same value, it does get confusing.\r\n\r\n```\r\nimport control\r\nimport control.matlab\r\ns = control.tf('s')\r\n\r\nG = 1/s**3\r\n\r\ncontrol.bode(G);\r\n```\r\n![image](https://user-images.githubusercontent.com/71486197/98642553-eb1d5280-232d-11eb-85d0-d9d6ebfa73d1.png)\r\n\r\n```\r\ncontrol.matlab.bode(G);\r\n```\r\n![image](https://user-images.githubusercontent.com/71486197/98642584-f7091480-232d-11eb-9ad1-d16e6431346d.png)\r\n\r\nWhat i've tried so far\r\n- [x] using different transfer functions (1/s^4 or 1/s^2 * 1/(s+10))\r\n- [x] specifying \"omega\" with a frequency range (as suggested here : https://ch.mathworks.com/matlabcentral/answers/99531-why-is-the-phase-that-is-returned-by-the-bode-function-wrapping-in-the-control-system-toolbox-5-1-r )\r\n- [x] extending the \"omega\" range\r\n\r\nIs it possible to get the \"absolute\" phase of the transfer function ? If not, i would suggest that `control.matlab.bode` be corrected as to reflect the behavior of matlab's bode\r\n\r\nThanks for your help ! ","author":{"url":"https://github.com/SebastienDeriaz","@type":"Person","name":"SebastienDeriaz"},"datePublished":"2020-11-10T07:41:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/467/python-control/issues/467"}