René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Different impulse responses for zpk vs tf","articleBody":"### Discussed in https://github.com/python-control/python-control/discussions/1061\r\n\r\n\u003cdiv type='discussions-op-text'\u003e\r\n\r\n\u003csup\u003eOriginally posted by **MEnzmann** November 19, 2024\u003c/sup\u003e\r\nHi all! \r\n\r\nI am little puzzled about the declaration of transfer-functions with control.zpk. The step-responses / impulse-responses of a transfer-function declared with control.zpk seem to unstable, although the poles are in the left-half plane and a bode plot does not show unstable poles. Am I missing something in the following MME?\r\n\r\nHelp would be appreciated! TIA!\r\n\r\n_import control as ct\r\nimport control.matlab as ml\r\nimport matplotlib.pyplot as pl\r\n#### Declare stable system as zpk \r\nGzp = ct.zpk([-5],[-1,-10], gain=4)\r\nprint(Gzp)\r\n#### Declare same system as tf\r\nGtf = ct.tf([4,20], [1,11, 10])\r\nprint(Gtf)\r\n#### Both systems share the same poles and zeros, the difference of both systems is 0.\r\n#### Yet: the Gzp system is instable in simulations while Gtf is stable (as expected)\r\n[Tzp, Yzp] = ct.impulse_response(Gzp)\r\npl.plot(Tzp, Yzp)\r\npl.show()\r\n[Ttf, Ytf] = ct.impulse_response(Gtf)\r\npl.plot(Ttf, Ytf)\r\npl.show()__\u003c/div\u003e","author":{"url":"https://github.com/murrayrm","@type":"Person","name":"murrayrm"},"datePublished":"2024-11-20T06:23:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/1062/python-control/issues/1062"}