bug in create_statefbk_iosystem, option refgain #1189

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1. murrayrm commented on Dec 20, 2025

   

   murrayrm

   on Dec 20, 2025

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   Thanks for the post! I'll look into this, but if you can also post some code that generates the error, that would be helpful (and we can add it to the unit tests).
2. murrayrm

   self-assigned this

   on Dec 20, 2025
3. miroslavfikar commented on Dec 20, 2025

   

   miroslavfikar

   on Dec 20, 2025

   Last edited by bnavigator

   ContributorAuthor

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   This is my code with modified function.
   bug.py
   Replacing by the library version throws error:

   Traceback (most recent call last):
     File "<string>", line 17, in __PYTHON_EL_eval
     File "/home/fikar/miro/doc/pedagog/tar2/course_2_tar2/exercises/week_02/python/bug.py", line 54, in <module>
       ctrl, sys_cl = ct.create_statefbk_iosystem(sys_ol_full, KK, Kr, integral_action=C, feedfwd_pattern='refgain')
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/home/fikar/miniconda3/lib/python3.13/site-packages/control/statefbk.py", line 1011, in create_statefbk_iosystem
       ctrl = ss(
           A_lqr, B_lqr, C_lqr, D_lqr, dt=sys.dt, name=name,
           inputs=inputs, outputs=outputs, states=states)
     File "/home/fikar/miniconda3/lib/python3.13/site-packages/control/statesp.py", line 1745, in ss
       sys = StateSpace(*args, **kwargs)
     File "/home/fikar/miniconda3/lib/python3.13/site-packages/control/statesp.py", line 272, in __init__
       _check_shape(D, self.noutputs, self.ninputs, name="D")
       ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/home/fikar/miniconda3/lib/python3.13/site-packages/control/mateqn.py", line 645, in _check_shape
       raise ControlDimension(
           f"Incompatible dimensions of {name} matrix; "
           f"expected ({n}, {m}) but found {M.shape}")
   control.exception.ControlDimension: Incompatible dimensions of D matrix; expected (1, 4) but found (1, 5)
   >>> 
   
4. murrayrm commented on Dec 21, 2025

   

   murrayrm

   on Dec 21, 2025

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   Thanks. Extracting the code that generates the error to have everything in one place:

   import control as ct
   import numpy as np
   
   A = np.array([[0, 1, 0], [0, 0, 1], [-6, -11, -6]])
   B = np.array([[0], [0], [1]])
   C = np.array([[1, 0, 0]])
   D = np.array([[0]])
   sys_ol = ct.ss(A, B, C, D, name='OL')
   
   Cfull = np.eye(3)
   Dfull = np.array([[0], [0], [0]])
   sys_ol_full = ct.ss(A, B, Cfull, Dfull, name='OL')
   
   # Extend states by the integral part
   nx, nu = B.shape
   ny, _ = C.shape
   A1 = np.block([[A, np.zeros((nx, ny))], [-C, np.zeros((ny, 1))]])
   B1 = np.vstack((B, np.zeros((ny, nu))))
   
   # Construct the controller
   Q = 150*np.eye(nx+ny)
   R = 1*np.eye(nu)
   Q = np.diag([1, 1, 1, 1/0.01**2])
   K, _, _ = ct.lqr(A1, B1, Q, R)
   Kr = 0
   
   # Preparation for minus sign in create_statefbk_iosystem
   KK = K
   KK[0,3] = - K[0,3]
   
   ctrl, sys_cl = ct.create_statefbk_iosystem(sys_ol_full, KK, Kr, integral_action=C, feedfwd_pattern='refgain')
   
5. murrayrm

   closed this as completedin #1222on Aug 14, 2026