Unexpected and unwanted behaviour of control.ctrb #1097

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1. roryyorke commented on Jan 19, 2025

   

   roryyorke

   on Jan 19, 2025

   Contributor

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   the arguments for ctrb and obsv aren't checked for size.

   In [42]: ct.ctrb(np.eye(2), 0.5)
   Out[42]: 
   array([[0.5, 0.5],
          [0.5, 0.5]])
   
   In [43]: ct.ctrb(0.3*np.eye(2), 0.5)
   Out[43]: 
   array([[0.5 , 0.15],
          [0.5 , 0.15]])
   
   In [44]: ct.ctrb(0.1*np.eye(2), 1)
   Out[44]: 
   array([[1. , 0.1],
          [1. , 0.1]])
   
   In [45]: ct.ctrb(0.1*np.eye(2), np.array([1,1]))
   Out[45]: 
   array([[1. , 1. , 0.1, 0.1],
          [1. , 1. , 0.1, 0.1]])
   
   In [46]: ct.obsv(0.1*np.eye(2), 1)
   Out[46]: 
   array([[1. , 1. ],
          [0.1, 0.1]])
   
   In [47]: ct.obsv(0.1*np.eye(2), [1, 1])
   Out[47]: 
   array([[1. , 1. ],
          [0.1, 0.1]])
   
   In [48]: ct.obsv(0.1*np.eye(2), [1, 1, 1])
   ---------------------------------------------------------------------------
   ValueError                                Traceback (most recent call last)
   Cell In[48], line 1
   ----> 1 ct.obsv(0.1*np.eye(2), [1, 1, 1])
   
   File ~/miniforge3/envs/work/lib/python3.12/site-packages/control/statefbk.py:1070, in obsv(A, C, t)
      1068 # Construct the observability matrix
      1069 obsv = np.zeros((t * p, n))
   -> 1070 obsv[:p, :] = cmat
      1072 for k in range(1, t):
      1073     obsv[k * p:(k + 1) * p, :] = np.dot(obsv[(k - 1) * p:k * p, :], amat)
   
   ValueError: could not broadcast input array from shape (1,3) into shape (1,2)
   

   The fix seems straightforward -- adapt the _ssmatrix calls and size checks from the statesp.StateSpace.__init__.

   👍React with 👍1Reacted by Bart Wolleswinkel
2. murrayrm

   closed this as completedin #1099on Jan 20, 2025