step_info error for MIMO system  #574

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1. bnavigator commented on Mar 16, 2021

   

   bnavigator

   on Mar 16, 2021

   Contributor

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   Why line 614? Current master has that line at 807, Your own PR #567 duplicates it in 807 and 817.

   Can confirm with current master. The problem is the indexing of yout:

   [ben@skylab:~/src/python-control]% python3                                                                                                                       [0]
   Python 3.8.8 (default, Feb 19 2021, 16:53:21) [GCC] on linux
   Type "help", "copyright", "credits" or "license" for more information.
   >>> from control import ss, step_response, step_info
   >>> 
   >>> A = [[0.68, -0.34], [0.34, 0.68]];
   >>> B = [[0.18, -0.05], [0.04, 0.11]];
   >>> C = [[0, -1.53], [-1.12, -1.10]];
   >>> D = [[0, 0], [0.06, -0.37]];
   >>> m_sys = ss(A,B,C,D,0.2);
   >>> mt,my=step_response(m_sys)
   >>> mt.shape
   (25,)
   >>> my.shape
   (2, 2, 25)
   >>> step_info(m_sys)
   /home/ben/src/python-control/control/statesp.py:1549: UserWarning: Converting MIMO system to SIMO system. Only input 0 is used.
     warn("Converting MIMO system to SIMO system. "
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/ben/src/python-control/control/timeresp.py", line 807, in step_info
       if((yout[i] <= inf_margin) | (yout[i] >= sup_margin)):
   IndexError: index 24 is out of bounds for axis 0 with size 2
   
2. bnavigator commented on Mar 16, 2021

   

   bnavigator

   on Mar 16, 2021

   Contributor

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   Why not adjust #567 to handle MIMO systems the way MATLAB's stepinfo does:

   For a MIMO system, stepinfo returns a structure array in which each entry contains the response characteristics of the corresponding I/O channel of the system. For this example, use a two-output, two-input discrete-time system. Compute the step-response characteristics.
3. juanodecc commented on Mar 16, 2021

   

   juanodecc

   on Mar 16, 2021

   ContributorAuthor

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   Why line 614? Current master has that line at 807, Your own PR #567 duplicates it in 807 and 817.

   Can confirm with current master. The problem is the indexing of yout:

   [ben@skylab:~/src/python-control]% python3                                                                                                                       [0]
   Python 3.8.8 (default, Feb 19 2021, 16:53:21) [GCC] on linux
   Type "help", "copyright", "credits" or "license" for more information.
   >>> from control import ss, step_response, step_info
   >>> 
   >>> A = [[0.68, -0.34], [0.34, 0.68]];
   >>> B = [[0.18, -0.05], [0.04, 0.11]];
   >>> C = [[0, -1.53], [-1.12, -1.10]];
   >>> D = [[0, 0], [0.06, -0.37]];
   >>> m_sys = ss(A,B,C,D,0.2);
   >>> mt,my=step_response(m_sys)
   >>> mt.shape
   (25,)
   >>> my.shape
   (2, 2, 25)
   >>> step_info(m_sys)
   /home/ben/src/python-control/control/statesp.py:1549: UserWarning: Converting MIMO system to SIMO system. Only input 0 is used.
     warn("Converting MIMO system to SIMO system. "
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/ben/src/python-control/control/timeresp.py", line 807, in step_info
       if((yout[i] <= inf_margin) | (yout[i] >= sup_margin)):
   IndexError: index 24 is out of bounds for axis 0 with size 2
   

   yes my bad, is line 614 for version 8.4
4. juanodecc commented on Mar 16, 2021

   

   juanodecc

   on Mar 16, 2021

   ContributorAuthor

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   Why not adjust #567 to handle MIMO systems the way MATLAB's stepinfo does:

   For a MIMO system, stepinfo returns a structure array in which each entry contains the response characteristics of the corresponding I/O channel of the system. For this example, use a two-output, two-input discrete-time system. Compute the step-response characteristics.

   Yes, I am trying to fix it, but I commit a partial solution for now. That improve the performance of this function
5. juanodecc commented on Mar 16, 2021

   

   juanodecc

   on Mar 16, 2021

   ContributorAuthor

   More actions

   Why not adjust #567 to handle MIMO systems the way MATLAB's stepinfo does:

   For a MIMO system, stepinfo returns a structure array in which each entry contains the response characteristics of the corresponding I/O channel of the system. For this example, use a two-output, two-input discrete-time system. Compute the step-response characteristics.

   step_response have limitations, that function can solve only SIMO systems. My idea is convert the step_info into two functions: step_info4data (t, y, yfinal) for multidimentional, time and output parameters, in the other hand, keep a step_info(sys) as is, but that function can call step_info4data () with the proper input vector for MIMO systems. This can allow use the step_info4data function with time vectors and output vectors imported from externals simulation or system stimulation
6. bnavigator commented on Mar 16, 2021

   

   bnavigator

   on Mar 16, 2021

   Contributor

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   I might be missing something, but the current step_response can handle MIMO. See my.shape.
7. murrayrm

   closed this as completedin #577on Mar 20, 2021