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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Step Response and step_info accuracy issue","articleBody":"Hi, \r\nI found an accuracy issue related to control.step_response and control.step_info. To be specific, the issue is in _default_response_times() function. \r\nI have two system transfer function sys1 and sys2.They both have exactly the same frequency response.  \r\nsys1:\r\n num1 = [1.067e+05, 5.791e+04], den1 = [10.67, 1.067e+05, 5.791e+04]\r\nOR \r\nk = 10000, zeros = [-0.5426], poles = [-1e+04, -0.5426 ]\r\n\r\nsys2:\r\nnum2 = [1.881e+06], den2 = [188.1, 1.881e+06]\r\nOR \r\nk = 10000, zeros = [], poles = [-1e+04,  ]\r\n\r\nAs you notice, sys1 has extra pole and zero where both have the same value.\r\n\r\nThe issue\r\n----------\r\nWhen I plot the step responses for both systems, the plots are not matched.  Also when I used step_info() to get the characteristics of the systems,  I got a different results. \r\n\r\nThe code:\r\n-----------\r\nhere is the code \r\n```\r\nnum1 = [1.067e+05, 5.791e+04]\r\nden1 = [10.67, 1.067e+05, 5.791e+04]\r\nnum2 = [1.881e+06]\r\nden2 = [188.1, 1.881e+06]\r\nsys_1 = control.TransferFunction(num1, den1)\r\nsys_2 = control.TransferFunction(num2, den2)\r\nt1, y1 = control.step_response(sys_1)\r\nt2, y2 = control.step_response(sys_2)\r\nprint(control.step_info(sys_1))\r\nprint(control.step_info(sys_2))\r\nplt.plot(t1, y1, t2, y2)\r\nplt.grid()\r\nplt.show()\r\n```\r\n\r\nTest on Matlab;\r\n-----------------\r\nI tested the two systems in Matlab. The step() function gives the same step response plot for both systems,  and stepinfo() results exactly the same values for both systems.\r\n\r\n","author":{"url":"https://github.com/rlegnain","@type":"Person","name":"rlegnain"},"datePublished":"2020-07-29T03:34:31.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/440/python-control/issues/440"}