Description

shiling2007

opened on Apr 24, 2022

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I am running the example from https://github.com/python-control/python-control/blob/master/examples/kincar-flatsys.py. And I am getting an error message as below,

---

ValueError Traceback (most recent call last)
in ()
130 # Simulation the open system dynamics with the full input
131 t, y, x = ct.input_output_response(
--> 132 vehicle_flat, T, ud, x0, return_x=True)
133
134 # Plot the open loop system dynamics

2 frames
/usr/local/lib/python3.7/dist-packages/control/timeresp.py in _process_labels(labels, signal, length)
681 # Make sure the signal list is the right length and type
682 if len(labels) != length:
--> 683 raise ValueError("List of %s labels is the wrong length" % signal)
684 elif not all([isinstance(label, str) for label in labels]):
685 raise ValueError("List of %s labels must all be strings" % signal)

ValueError: List of output labels is the wrong length**

The program is running in google Colab environment with python version 3.7.
Your help would be much appreciated.

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1. roryyorke commented on Apr 24, 2022

   

   roryyorke

   on Apr 24, 2022

   Contributor

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   That example was updated recently. Assuming you're running python-control version 0.9.1 (check with import control as ct; print(ct.__version__), you need the example file from 0.9.1.
2. murrayrm commented on Apr 24, 2022

   

   murrayrm

   on Apr 24, 2022

   Member

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   Alternatively, you can edit the latest version of the example to be compatible with the earlier version of the code. Here's the diff to implement:

   --- a/examples/kincar-flatsys.py
   +++ b/examples/kincar-flatsys.py
   @@ -109,7 +109,7 @@ def plot_results(t, x, ud):
    # Create differentially flat input/output system
    vehicle_flat = fs.FlatSystem(
        vehicle_flat_forward, vehicle_flat_reverse, vehicle_update,
   -    inputs=('v', 'delta'), outputs=('x', 'y', 'theta'),
   +    inputs=('v', 'delta'), outputs=('x', 'y'),
        states=('x', 'y', 'theta'))
   

   The change is that in the latest master the default for a flat system is that the default outputs are the flat outputs (in v0.9.1, the default outputs were the entire state, which didn't really make sense). This was changed in PR #709.
3. murrayrm

   closed this as completedon Apr 24, 2022
4. shiling2007 commented on Apr 24, 2022

   

   shiling2007

   on Apr 24, 2022

   Author

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   I am good now. Thanks a lot.

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